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Research Article
Petroleum coke as reductant in co-reduction of low-grade laterite ore and red mud to prepare ferronickel: Reductant and reduction effects
Xiaoshuang Guo, Zhengyao Li, Jicai Han, Dong Yang, and Tichang Sun
Available online 3 December 2021, https://doi.org/10.1007/s12613-021-2389-9
[Abstract](0) [PDF 1080KB](1)

Petroleum coke is industrial solid wastes and its disposal and storage has been a great challenge to the environment. In this study, petroleum coke was utilized as a novel co-reduction reductant of low-grade laterite ore and red mud. A ferronickel product of 1.98wt% nickel and 87.98wt% iron was obtained with 20wt% petroleum coke, which the roasting temperature and time was 1250 ℃ and 60 mins, respectively. The corresponding recovery of nickel and total iron were 99.54wt% and 95.59wt%, respectively. Scanning electron microscopy-energy dispersive spectrometry (SEM-EDS) analysis showed metallic nickel and iron mainly existed in the form of ferronickel particles which distributed uniformly at approximately 30 μm with high purity. This study demonstrated that petroleum coke is a promising reductant in the co-reduction of laterite ore and red mud. Compared to other alternatives, petroleum coke is advantageous with reduced production cost and high applicability in anthracite-deficient areas.

Research Article
Semi-empirical estimation for enhancing negative thermal expansion in PbTiO3-based perovskites
Tao Yang, Longlong Fan, Yilin Wang, Kun Lin, Jun Chen, and Xianran Xing
Available online 3 December 2021, https://doi.org/10.1007/s12613-021-2390-3
[Abstract](0) [PDF 579KB](1)

Generally, most materials expand when heated and contract when cooled, whereas negative thermal expansion (NTE) materials are very rare. As a typical NTE material, PbTiO3 and related compounds have drawn particular interest in recent years. The discovery of enhanced NTE system of PbTiO3 is beneficial to deepen our understanding of the mechanism of them and regulate their properties. At present, the method of discriminating enhanced NTE material based on PbTiO3 is not universal. Here, we propose a semi-empirical method, through evaluating the average lattice distortion in related systems, to estimate the relative coefficient of thermal expansion conveniently. The rationality of the method was verified by the analysis of 0.6PbTiO3-0.4Bi(GaxFe1-x)O3 system. So far, all the PbTiO3-based compounds with enhanced NTE conform well to this method. This method provides the possibility to find more enhanced NTE PbTiO3-based materials.

Research Article
Tension-compression asymmetry and corresponding deformation mechanism in ZA21 magnesium bars with bimodal structure
Yujiao Wang, Yun Zhang, and Haitao Jiang
Available online 3 December 2021, https://doi.org/10.1007/s12613-021-2388-x
[Abstract](0) [PDF 1830KB](1)

We investigated the asymmetric tension-compression (T-C) behavior of ZA21 bars with bimodal and uniform structures through axial tension and compression tests. The results show that the yield strengths of bars having bimodal structure are 206.42 and 140.28 MPa under tension and compression, respectively, which are higher than that of bars having uniform structure, that is, tensile and compressive yield strength of 183.71 and 102.86 MPa, respectively. Prismatic slip and extension twinning under tension and basal slip and extension twinning under compression dominate the yield behavior and induce the T-C asymmetry. However, due to the basal slip activated in fine grains under tension and the inhibition of extension twinning by fine grains under compression, the bimodal structure possesses a lower T-C asymmetry (0.68) compared to the uniform structure (0.56). Multiple extension twins occur during deformation, and the selection of twin variants depends on the Schmid factor of the six variants activated by parent grains. Furthermore, the strengthening effect of the bimodal structure depends on the grain size and the ratio of coarse and fine grains.

Research Article
The icosahedral quasicrystal structure of Mg40Zn55Nd5 phase and its thermodynamic stability
Shuai Zhang, Qianqian Li, Hongcan Chen, Qun Luo, and Qian Li
Available online 3 December 2021, https://doi.org/10.1007/s12613-021-2391-2
[Abstract](0) [PDF 1518KB](1)

The quasicrystal phase is beneficial to increasing the strength of magnesium alloys. However, its complicated structure and unclear phase relations impede however the design of alloys with good mechanical properties. In this paper, the Mg40Zn55Nd5 icosahedral quasicrystal (I-phase) structure is discovered in the as-cast Mg-58Zn-4Nd alloy by atomic resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). It has cloud-like morphology with the composition of Mg41.6Zn55.0Nd3.4. The selected area electronic diffraction (SAED) analysis shows that the icosahedral quasicrystal structure has 5-fold, 4-fold, 3-fold, and 2-fold symmetry zone axes. The thermodynamic stability of the icosahedral quasicrystal is investigated by differential scanning calorimetry (DSC) in the annealed alloys. When annealing above 300 °C, the Mg40Zn55Nd5 quasicrystal is found to decompose into a stable ternary phase Mg35Zn60Nd5, binary phase MgZn and α-Mg, which suggests that the quasicrystal is a metastable phase in Mg-Zn-Nd system.

Research Article
Effect of N2 partial pressure on comprehensive properties of antibacterial TiN/Cu nanocomposite coating
Hui Liu, Yanhui Zhao, Chuanshi Sui, Yi Li, Muhammad Ali Siddiqui, Susu Li, Tong Li, Shuyuan Zhang, Hai Wang, Tao Jin, Ren Ling, Ke Yang, and Ning Zhang
Available online 26 November 2021, https://doi.org/10.1007/s12613-021-2387-y
[Abstract](32) [PDF 1003KB](2)

Foreign body reactions to the wear debris and corrosion products from the implants, and bacterial infections are the main factors leading to the implant failures. In order to resolve these problems, the antibacterial TiN/Cu nanocomposite coatings with various N2 partial pressures were deposited on 304 stainless steels using an arc ion plating (AIP) system, named TiN/Cu-xPa (x=0.5, 1.0, 1.5). The results of X-ray diffraction analysis, energy-dispersive X-ray spectroscopy, and scanning electron microscopy showed that the N2 partial pressures determined the Cu contents, surface defects, and crystallite sizes of TiN/Cu nanocomposite coatings, which further influenced the comprehensive abilities. And the hardness and wear resistances of TiN/Cu coatings were enhanced with increase of the crystallite sizes. Under the co-actions of surface defects, crystallite sizes and Cu content, TiN/Cu-1.0Pa and TiN/Cu-1.5Pa coatings possessed excellent corrosion resistance. Besides, the biological tests proved that all the TiN/Cu coatings showed no cytotoxicity with strong antibacterial ability. Among them, TiN/Cu-1.5Pa coating significantly promoted the cell proliferation, which is expected to be a novel antibacterial, corrosion-resistant and wear-resistant coating on the surfaces of medical implants.

Research Article
Phosphorus reduction behavior of high phosphate iron ore during hydrogen-rich sintering
Yanbiao Chen, Wenguo Liu, and Haibin Zuo
Available online 25 November 2021, https://doi.org/10.1007/s12613-021-2385-0
[Abstract](56) [PDF 1288KB](5)

High-phosphorus iron ore resource is recognized as refractory iron ore because of its high phosphorus content and complex ore phase structure. Therefore, it is of great theoretical and practical significance to develop innovative technology to realize the efficient utilization of high-phosphorus iron ore resources. According to this, a method of phosphorus gasification removal in hydrogen-rich sintering process was proposed. In this paper, the reduction mechanism of phosphorus in hydrogen-rich sintering was studied, as well as the reduction kinetics of apatite based on the non-isothermal kinetic method. The results show that improving the reduction time from 20min to 60min, the dephosphorization rate increases from 10.93% to 29.51%. Companied with the reduction of apatite, the metal iron accumulates, part of the reduced phosphorus gas is absorbed by metal iron to form stable iron-phosphorus compounds, resulting in a great reduction of dephosphorization rate. The reduction of apatite is mainly concentrated in the sinter zone and burning zone, and the reduced phosphorus gas moves downward along with flue gas under suction pressure and is condensed and adsorbed partly by the sintering bed when passing through the drying zone and green mix zoon, as a result, the dephosphorization rate is greatly reduced. Based on the Ozawa formula of iso-conversion rate, the reduction activation energy of apatite is 80.42 kJ/mol. The mechanism function of apatite reduction is determined by differential method (Freeman-Carroll method) and integral method (Coats-Redfern method). The differential form of the equation is f(a)= 2(1-a)1/2, and the integral form is G(a)= 1-(1-a)1/2.

Research Article
The effect of runner design and pressurization on the microstructure of high pressure die cast Mg-3.0Nd-0.3Zn-0.6Zr alloy
Tongtong Zhang, Wenbo Yu, Chaosheng Ma, Yuqi Zhou, and Shoumei Xiong
Available online 25 November 2021, https://doi.org/10.1007/s12613-021-2386-z
[Abstract](25) [PDF 2296KB](2)

Externally solidified crystals (ESCs) are unavoidable in high-pressure die casting (HPDC), which is detrimental to the mechanical performance of castings. In order to reduce ESCs quantities and clarify the relationship between ESCs and formation of defects (defect band and pores), 2D and 3D characterizations were carried out on the castings produced through ingate runner equipped with and without ESCs collector. It reveals that ESCs reduction can strongly modify the morphologies of defect band and shrinkage pores. 3D reconstruction reveals that the net-shrinkage pores transformed into isolated island-shrinkage pores with the reduction of ESCs quantities and size. Tensile fracture further proves that the mechanical properties of HPDC castings are strongly related with the ESCs fraction rather than the porosity volume. Meanwhile, tensile transgranular fracture mode transformed into intergranular fracture mode duo the reduction of ESCs. In addition, it reveals the casting pressurization can strongly reduce the porosity morphology, volume and size.

Research Article
Efficiency enhancement of Cs0.1(CH3NH3)0.9PbI3 perovskite solar cell by surface passivation using iso-butyl ammonium iodide
Wakul Bumrugsan, Kritsada Hongsith, Vasan Yarangsi, Pisith Kumnorkeaw, Sukrit Sucharitakul, Surachet Phaduangdhitidhada, and Supab Choopun
Available online 19 November 2021, https://doi.org/10.1007/s12613-021-2382-3
[Abstract](46) [PDF 1196KB](7)

Efficiency enhancement of Cs0.1(CH3NH3)0.9PbI3 solar cell devices was performed by using iso-butyl ammonium iodide (IBA) passivated on Cs0.1(CH3NH3)0.9PbI3 films. The n-i-p structure of perovskite solar cell devices was fabricated with the structure of FTO/SnO2/Cs0.1(CH3NH3)0.9PbI3 and IBA/Spiro-OMeTAD/Ag. The effect of different weights of IBA passivated on Cs-doped PSCs was systematically investigated and compared with non-passivated devices. It was found that the 5mg IBA-passivated devices exhibited a high PCE of 15.4% higher than 12.6% of non-IBA-passivated devices. The improvement of photovoltaic parameters of the 5 mg IBA-passivated devices can be clearly observed compared to the Cs-doped device. The better performance of the IBA-passivated device can be confirmed by the reduction of PbI2  phase in the crystal structure, lower charge recombination rate, lower charge transfer resistance, and improved contact angle of perovskite films. Therefore, IBA passivation on Cs0.1(CH3NH3)0.9PbI3 is a promising technique to improve the efficiency of Cs-doped perovskite solar cells.

Research Article
Comparative study on the atmospheric corrosion behavior of Nb- and Sb-added weathering steels exposed to the South China Sea
Wei Wu, Lili Zhu, Peilin Chai, Niyun Liu, Longfei Song, Zhiyong Liu, and Xiaogang Li
Available online 19 November 2021, https://doi.org/10.1007/s12613-021-2383-2
[Abstract](38) [PDF 1975KB](4)

The atmospheric corrosion behavior of new-type weathering steels (WSs) was comparatively studied, and the effects of Nb and Sb during corrosion were clarified in detail through field exposure and characterization. The results showed that the addition of Nb and Sb played positive roles in corrosion resistance, but there was a clear difference between these two elements. Nb addition slightly improved the rust property of conventional WS but could not inhibit the electrochemical process. In contrast, Sb addition significantly improved the corrosion resistance from the aspects of electrochemistry and rust layer. Specifically, 0.05% Sb optimized the rust structure, accelerated the formation of a high proportion of dense and protective α-FeOOH, repelled the invasion of Cl-, and retarded localized acidification at the bottom of the pit.

Research Article
Improving the room-temperature bendability of Mg-3Al-1Zn alloy sheet by introducing a bimodal microstructure and the texture re-orientation
Chao He, Yibing Zhang, Ming Yuan, Bin Jiang, Qinghang Wang, Yanfu Chai, Guangsheng Huang, Dingfei Zhang, and Fusheng Pan
Available online 19 November 2021, https://doi.org/10.1007/s12613-021-2384-1
[Abstract](30) [PDF 1421KB](3)

A significant enhancement of bendability was achieved by the introduction of bimodal microstructure for AZ31B alloy sheets via pre-compression and subsequent annealing (PCA) process. This combined treatment led to the c-axis of the extracted samples that were inclined by 30° to the rolling direction (30° sample) further shifted toward the rolling direction (RD) and resulted in a higher (Schmid factors) SF value of basal slip under the RD tensile stress. Furthermore, the bimodal microstructure that was introduced by the PCA process broke the damage bands (DBs) in the initial hot rolled AZ31B alloy sheets and gave rise to a more uniform strain distribution in the outer tension region of the bending samples, in which the tensile deformation was accommodated by the equally distributed {10-12} tension twinning and basal slip. Consequently, the bimodal microstructure, shifted basal texture and the modification of DBs were responsible for the significant enhancement in the bendability of the AZ31 alloys.

Research Article
Evaluation and classification of rock heterogeneity based on acoustic emission detection
Tongzhao Zhang, Hongguang Ji, Xiaobo Su, Shuang You, Daolu Quan, Zhou Zhang, and Jinzhe Li
Available online 16 November 2021, https://doi.org/10.1007/s12613-021-2381-4
[Abstract](38) [PDF 3056KB](4)

For deep rock mechanics and subsurface engineering, accurately characterizing and evaluating rock heterogeneity as well as analyzing the correlation between the heterogeneity and physical and mechanical properties of rocks are critical. This study investigated the characteristics of acoustic emission signals produced in the process of strong and weak phase damage to rocks. The failure mechanisms of the strong and weak phases were analyzed by performing Brazilian splitting tests on different metagabbros and granites. The strong–weak phase ratio of the rocks and the uniformity of their spatial distribution were characterized. Test results show that as the feldspar develops, the strong-phase ratio of the metagabbro increases. However, the spatial distribution of feldspar minerals in the metagabbro becomes less uniform. The mineral spatial distribution uniformity in the altered granite is good; however, its strong-phase ratio is low. Furthermore, the strong-phase ratio of the typical granite is high; however, its mineral spatial distribution uniformity is poor. Moreover, uniaxial and triaxial test results show that the peak strength and elastic modulus of the rocks are related to the strong–weak phase ratio and mineral spatial distribution uniformity of the rocks. This study provides a new analytical method for the mechanical evaluation of deep rocks.

Invited Review
Reagent types and action mechanisms in flotation of ilmenite: A review
Jiaozhong Cai, Jiushuai Deng, Liang Wang, Mingzhen Hu, Hongxiang Xu, Xiao'an Hou, Bozeng Wu, and Shimei Li
Available online 16 November 2021, https://doi.org/10.1007/s12613-021-2380-5
[Abstract](33) [PDF 1154KB](10)

Ilmenite is an essential mineral for the extraction of titanium. Conventional physical separation methods have difficulty recovering fine ilmenite, and dressing plants have begun applying flotation to recover ilmenite. The interaction of reagent groups with Ti and Fe sites on the ilmenite surface dramatically influences the ilmenite flotation. Nevertheless, the investigation on Fe sites has received more attention because the activity of Ti is lower than that of Fe. For the activators on ilmenite flotation, most are metal ions but typically lead ions. Metal ions of activators promote the flotation of ilmenite by increasing the active sites on the ilmenite surface. Combined reagents have a better selective separation of ilmenite than a single reagents due to its synergistic effect. Combining the lead ion (Pb2+) and the benzyl hydroxamic acid (BHA) into a Pb–BHA complex has a marked effect on ilmenite flotation, which puts forward a new idea of developing combined reagents for ilmenite flotation. This review considers reagent types and action mechanisms in flotation of ilmenite. Besides, based on the analysis of the previous work, a brief future outlook of reagent types and action mechanisms in flotation of ilmenite was also proposed in the study.

Research Article
Effect of titanium content on the refinement of coarse columnar austenite grains during solidification of peritectic steel
Jiazhi An, Zhaozhen Cai, and Miaoyong Zhu
Available online 9 November 2021, https://doi.org/10.1007/s12613-021-2375-2
[Abstract](104) [PDF 1496KB](11)

The effect of titanium content on the refinement of austenite grain size in as-cast peritectic carbon steel was investigated by fast directional solidification experiments that simulate the solidification and growth of surface and subsurface austenite in continuously cast slabs. Transmission electron microscope(TEM) and scanning electron microscope(SEM) were used to analyze the size and distribution of Ti(C, N) precipitates during solidification. Based on these results, the pinning pressure of Ti(C, N) precipitates on the growth of coarse columnar grains (CCGs) was studied. The results show that the austenite microstructure of as-cast peritectic carbon steel is mainly composed of regions of CCGs and fine columnar grains (FCGs). Increasing the content of titanium reduces the region and the short axis of the CCGs. When the content of titanium is 0.09 wt%, there is no CCG region. Dispersed microscale particles will firstly form in the liquid, which will decrease the transition temperature from FCGs to CCGs. The chain-like nanoscale Ti(C, N) will precipitate with the decrease of the transition temperature. Furthermore, calculations shows that the refinement of the CCGs is caused by the pinning effect of Ti(C, N) precipitates.

Invited Review
Technology strategies to achieve carbon-peak and carbon-neutrality for Chinese metal mines
Qifeng Guo, Xun Xi, Shangtong Yang, and Meifeng Cai
Available online 9 November 2021, https://doi.org/10.1007/s12613-021-2374-3
[Abstract](61) [PDF 573KB](5)

Greenhouse gas (GHG) emissions related to human activities have significantly caused climate change since the Industrial Revolution. China aims to achieve its carbon emissions peak before 2030 and carbon neutrality before 2060. This paper attempts to review and discuss technical strategies to achieve the “dual-carbon” targets in Chinese metal mines. First, global carbon emissions and emission intensity from metal mining industries are analysed. The metal mining status and carbon emissions in China are then examined. Further, advanced technologies for carbon mitigation and carbon sequestration in metal mines are reviewed. Finally, a technical roadmap for achieving carbon-neutrality in Chinese metal mines are proposed. It has been found that some international giants have already made carbon reduction targets and planned to achieve carbon neutrality by 2050. Moreover, improving mining efficiency by developing advanced technologies and replacing fossil fuel with renewable energy are two key approaches to reducing GHG emissions. Green mines can significantly benefit the carbon neutrality process for metal mines through carbon absorption of reclamation vegetation. The geothermal energy extraction from operating and abandoned metal mines is a promising technology for providing clean energy and contributing to the carbon neutrality target for Chinese metal mines. Carbon sequestration by mining backfill and tailing through mineral carbonation has the potential to permanently and safely store carbon dioxide, which can eventually transform the metal mining industry to become carbon neutral or even carbon negative.

Invited Review
Tribological properties of high-entropy alloys: A review
Zhuo Cheng, Shuize Wang, Guilin Wu, Junheng Gao, Xusheng Yang, and Honghui Wu
Available online 9 November 2021, https://doi.org/10.1007/s12613-021-2373-4
[Abstract](81) [PDF 1658KB](14)

Tribology includes the branch of friction, wear and lubrication, and it largely determines the service performance of structural materials. The advent and abundance of newly-emerging high-entropy alloy display outstanding hardness, anti-oxidation and anti-softening ability, etc., which enrich the wear-resistance alloy family. To systematically demonstrate the tribological behavior of high-entropy alloys, this review starts from the basic tribological characteristics of single-phase, dual-phase multi-phase high-entropy alloys, and high-entropy alloy composites at room temperature, and then the strategies to improve the tribological property of HEAs are summarized. Additionally, the tribological performances at elevated temperature are also discussed. Finally, this review is concluded by providing a brief perspective on the future development of high-entropy alloys toward tribological applications.

Research Article
Enhanced sulfidization of azurite surfaces by ammonium phosphate and its effect on flotation
Qian Zhang, Shuming Wen, Qicheng Feng, and Han Wang
Available online 9 November 2021, https://doi.org/10.1007/s12613-021-2379-y
[Abstract](37) [PDF 1104KB](4)

Although azurite is one of the most important copper oxide minerals, the recovery of this mineral via sulfidization-xanthate flotation is typically unsatisfactory. The present work demonstrates the enhanced sulfidization of azurite surfaces using ammonia phosphate ((NH4)3PO4) together with Na2S, based on micro-flotation experiments, time-of-flight secondary ion mass spectrometry (ToF−SIMS), X-ray photoelectron spectroscopy (XPS), zeta-potential measurements, contact angle measurements, Fourier-transform infrared (FT-IR) spectroscopy and ultraviolet-visible (UV-vis) spectroscopy. Micro-flotation experiments showed that the floatability of azurite was increased following the simultaneous addition of (NH4)3PO4 and Na2S. ToF-SIMS and XPS analyses demonstrated the formation of a high concentration of S species on the azurite surface and an increase in the number of Cu(I) species after exposure to (NH4)3PO4 and Na2S compared with the azurite–Na2S system. The zeta potential of azurite particles was negatively shifted and the contact angle on the azurite surface was increased with the addition of (NH4)3PO4 prior to Na2S. These results indicate that treatment with (NH4)3PO4 enhanced the sulfidization of azurite surfaces, which in turn promoted xanthate attachment. FT-IR and UV-vis analyses confirmed that the addition of (NH4)3PO4 increased the adsorption of xanthate while reducing the consumption of xanthate during the azurite flotation process. Thus, (NH4)3PO4 had a beneficial effect on the sulfidization flotation of azurite.

Research Article
Effect of carbonate additive on the microstructure and corrosion resistance of plasma electrolytic oxidation coating on Mg-9Li-3Al alloy
Siyuan Jin, Xiaochun Ma, Ruizhi Wu, Tingqu Li, Jiaxiu Wang, Boris L. Krit, Legan Hou, Jinghuai Zhang, and Guixiang Wang
Available online 9 November 2021, https://doi.org/10.1007/s12613-021-2377-0
[Abstract](60) [PDF 1244KB](9)

Carbonate is added into the silicate system electrolyte in order to improve the corrosion resistance of the plasma electrolytic oxidation (PEO) coating on Mg-9Li-3Al (LA93) alloy. The influences of carbonate on the morphology, structure and phase composition of the coating were investigated by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The corrosion resistance of the coating was evaluated by electrochemical experiment, hydrogen evolution and immersion test. The results show that, the addition of carbonate brings about the denser coating with increased hardness and the corrosion resistant Li2CO3 phase is formed. Electrochemical experiments show that, compared with the coating without carbonate, the corrosion potential of the carbonate coating is positively shifted (24 mV), and the corrosion current density is reduced by approximately an order of magnitude. The coating with carbonate addition possesses higher corrosion resistance, and it has a longer-term protection ability.

Invited Review
The application of low-cost particulate matter sensors for air quality monitoring and exposure assessment in underground mines - A review
Nana Amoako Amoah, Guang Xu, Yang Wang, Jiayu Li, Yongming Zou, and Baisheng Nie
Available online 9 November 2021, https://doi.org/10.1007/s12613-021-2378-z
[Abstract](313) [PDF 837KB](30)

Exposure to mining-induced particulate matter (PM) including coal dust and diesel particulate matter (DPM) causes severe respiratory diseases such as coal workers’ pneumoconiosis (CWP) and lung cancer. Limited spatiotemporal resolution of current PM monitors causes miners to be exposed to unknown PM concentrations, with increased overexposure risk. Low-cost PM sensors offer a potential solution to this challenge with their capability in characterizing PM concentrations with high spatiotemporal resolution. However, its application in underground mines have not been explored. With the aim of examining the potential application of low-cost sensors in underground mines, a critical review of the present status of PM sensor research is conducted. The working principles of present PM monitors and low-cost sensors are compared. Sensor error sources are identified, and comprehensive calibration processes are presented to correct them. Evaluation protocols are proposed to evaluate sensor performance prior deployment and the potential application of low-cost sensors is discussed.

Research Article
Phase equilibria studies of the titanomagnetite and ilmenite smelting slags
Jinfa Liao and Baojun Zhao
Available online 9 November 2021, https://doi.org/10.1007/s12613-021-2376-1
[Abstract](59) [PDF 677KB](10)

Phase equilibrium information of the slag plays an important role in pyrometallurgical processes to obtain optimum fluxing conditions and operating temperatures. Smelting reduction of titanomagnetite and ilmenite ores in iron blast furnace can form Ti(CN) particles causing increased viscosities of slag and hot-metal. HIsmelt has been developed in recent years for ironmaking which does not need coke and sinter. Formation of Ti(CN) in the HIsmelt process is avoided because the oxygen partial pressure in the process is higher than that in the blast furnace. Smelting of TiO2-containing ores in HIsmelt process results in Al2O3–MgO–SiO2–CaO–TiO2 slag. Phase equilibria in this slag system have been investigated using equilibration, quenching and electron probe microanalysis (EPMA) technique. The experimental results are presented in two pseudo-binary sections, which represent the process of HIsmelt to treat 100% titanomagnetite ore and 100% titanomagnetite + 50% ilmenite respectively. The primary phases observed in the composition range investigated include pseudo-brookite M3O5 (MgO·2TiO2–Al2O3·TiO2), spinel (MgO·Al2O3), perovskite CaTiO3 and rutile TiO2. The results show that the liquidus temperatures decrease in the TiO2 and M3O5 primary phase fields with increasing CaO concentration and increase in the spinel and CaTiO3 primary phase fields with increasing CaO concentration. Calculation of solid-phase fractions from the experimental data has been demonstrated. Effect of the basicity on liquidus temperatures of the slag has been discussed. It seems that smelting of titanomagnetite plus ilmenite ores has significant advantages to obtain low-sulphur hot-metal and high-TiO2 slag. Experimentally determined liquidus temperatures are compared with the FactSage predictions to evaluate the existing thermodynamic databases.

Research Article
Effects of microstructure characteristics on the tensile properties and fracture toughness of TA15 alloy fabricated by hot isostatic pressing
Langping Zhu, Yu Pan, Yanjun Liu, Zhiyu Sun, Xiangning Wang, Hai Nan, Muhammad Arif Mughal, and Xin Lu
Available online 4 November 2021, https://doi.org/10.1007/s12613-021-2371-6
[Abstract](44) [PDF 2101KB](9)

Powder hot isostatic pressing (HIP) is an effective method to achieve near-net-shape manufacturing of high-quality complex thin-walled titanium alloy parts, and it has received extensive attention in recent years. However, there are few reports about the microstructure characteristics on the strengthening and toughening mechanisms of powder HIPed titanium alloys. Therefore, TA15 powder was prepared into alloy by HIP approach, which are used to explore the microstructure characteristics at different HIP temperatures, and the corresponding tensile properties and fracture toughness. Results show that the fabricated alloy has a "basket-like structure" when the HIP temperature below 950°C, consisting of lath clusters and surrounding small equiaxed grains belts. When the HIP temperature is higher than 950°C, the microstructure gradually transformed into the Widmanstatten structure, accompanied by a significant increase in grain size. The tensile strength and elongation are reduced from 948 MPa and 17.3% for the 910°C specimen to 861 MPa and 10% for the 970°C specimen. The corresponding tensile fracture mode changed from transcrystalline plastic fracture to mixed fracture including intercrystalline cleavage. The fracture toughness of the specimens increased from 82.64 MPa√m for the 910°C specimen to 140.18 MPa√m for the 970°C specimen. Specimens below 950°C tend to form holes due to the prior particle boundaries (PPBs), which is not conducive to toughening. Specimens above 950°C have high fracture toughness due to the crack deflection, crack branching and shear plastic deformation of the Widmanstatten structure. This study provides a valid reference for the development of powder HIPed titanium alloy.

Research Article
Bullet-like vanadium-based MOFs as a highly active catalyst for promoting the hydrogen storage property in MgH2
Zhiyu Lu, Jiahuan He, Mengchen Song, Yan Zhang, Fuying Wu, Jiaguang Zheng, Liuting Zhang, and Lixin Chen
Available online 4 November 2021, https://doi.org/10.1007/s12613-021-2372-5
[Abstract](38) [PDF 1578KB](4)

The practical application of magnesium hydride (MgH2) was seriously limited by its high desorption temperature and slow desorption kinetics. In this study, a bullet-like catalyst based on vanadium related MOFs (MOFs-V) was successfully synthesized and doped with MgH2 by ball milling to improve its hydrogen storage performance. Microstructure analysis demonstrated that the as-synthesized MOFs was consisted of V2O3 with a bullet-like structure. After adding 7wt% MOFs-V, the initial desorption temperature of MgH2 was reduced from 340.0°C to 190.6°C. Besides, the MgH2+7wt% MOFs-V composite released 6.4wt% H2 within 5 min at 300°C. Hydrogen uptake was started at 60°C under 32 bar hydrogen pressure for the 7wt% MOFs-V containing sample. The desorption and absorption apparent activity energy of the MgH2+7wt% MOFs-V composite was calculated to be 99.6±12.6 kJ mol-1 and 32.8±3.9 kJ mol-1, much lower than154.5±16.3 kJ mol-1 and 81.1±2.4 kJ mol-1 for the as-prepared MgH2. The MgH2+7wt% MOFs-V composite exhibited superior cyclic property. During the 20 cycles isothermal dehydrogenation and hydrogenation experiments, the hydrogen storage capacity stayed almost unchanged. X-ray diffraction (XRD) and X-ray photoelectron spectrometer (XPS) measurements confirmed the presence of metallic vanadium in the MgH2+ 7wt% MOFs-V composite, which served as catalytic unit to markedly improve the hydrogen storage properties of Mg/MgH2 system.

Research Article
Enhanced mechanical properties of Mg-3Al-1Zn alloy sheets through slope extrusion
Huabao Yang, Yanfu Chai, Bin Jiang, Chao He, Junjie He, Qingshan Yang, and Ming Yuan
Available online 28 October 2021, https://doi.org/10.1007/s12613-021-2370-7
[Abstract](151) [PDF 756KB](16)

A novel extrusion approach, entitled slope extrusion (SE), was employed to manufacture AZ31 alloy sheets. The microstructures, textures and mechanical properties were investigated, compared with those of the AZ31 sheet fabricated by conventional extrusion (CE). Through the combination of finite element simulation and actual experiment, the ultimate results indicated that significant grain refinement (from 9.1 to 7.7 and 5.6 μm) and strong basal texture (from 12.6 to 17.6 and 19.5 mrd) were achieved by the SE process. The essence was associated with the additional introduced inclined interface in the process of SE, which could bring about more asymmetric deformation and stronger accumulated strain along the ND when compared with the process of CE. As a consequence, the SE sheets exhibited a higher yield strength (YS) and ultimate tensile strength (UTS) than the counterparts of the CE sheet, which was mainly assigned to the synergistic effects from grain refining and texture strengthening.

Research Article
Influence of Zr and Mn additions on microstructure and properties of Mg–2.5wt% Cu–Xwt% Zn (X = 2.5, 5, and 6.5) alloys
A.V. Koltygin, V.E. Bazhenov, I.V. Plisetskaya, V.A. Bautin, A.I. Bazlov, N.Y. Tabachkova, O.O. Voropaeva, A.A. Komissarov, and V.D. Belov
Available online 26 October 2021, https://doi.org/10.1007/s12613-021-2369-0
[Abstract](50) [PDF 1148KB](9)

The effects of adding Zr and Mn in amounts less than 1 wt% on the microstructure, mechanical properties, casting properties, and corrosion resistance of Mg–Zn–Cu alloys containing 2.5wt% Cu and 2.5–6.5wt% Zn was studied. The hardness and electrical conductivity measurements were used to find an optimal heat treatment schedule with the best mechanical properties. It has been established that Zr significantly increases the yield strength of the alloys due to a strong grain refinement effect. However, the presence of Mn and Zr has a detrimental effect on alloy's elongation at fracture. It was shown that the precipitation of the Mg2Cu cathodic phase in the alloy structure negatively affects the corrosion behavior. Nevertheless, the addition of Mn decreased the corrosion rate of the investigated alloys. The best combination of the mechanical, casting, and corrosion properties were achieved in the alloys containing 2.5wt% Cu and 5wt% Zn; however, the Mn or Zr additions can improve the properties of the alloys. For example, the addition of Mn or Zr increased the fluidity of the alloys.

Research Article
Preparation and characterization of ceramic materials with low thermal conductivity and high strength using high-calcium fly ash
Mana Rodchom, Panida Wimuktiwan, Kanit Soongprasit, Duangduen Atong, and Supawan Vichaphund
Available online 22 October 2021, https://doi.org/10.1007/s12613-021-2367-2
[Abstract](154) [PDF 1529KB](21)

In this research, high calcium-fly ash (HCFA) collected from the Mae Moh electricity generating plant in Thailand was utilized as a raw material for ceramic production. The main compositions of HCFA characterized by XRF mainly consisted of 28.55 wt% SiO2, 16.06 wt% Al2O3, 23.40 wt% CaO and 17.03 wt% Fe2O3. Due to high proportion of calcareous and ferruginous contents, HCFA was used for replacing the potash feldspar in amounts of 10-40 wt%. The influence of substituting high-calcium fly ash (0-40 wt%) and sintering temperatures (1000-1200 οC) on physical, mechanical, and thermal properties of ceramic-based materials was investigated. The results showed that the incorporation of HCFA in appropriate amounts could enhance the densification and the strength as well as reduce the thermal conductivity of ceramic samples. High proportion of calcareous and ferruginous constituents in fly ash promoted the vitrification behavior of ceramic samples. As a result, the densification was enhanced by liquid phase formation at optimum fly ash content and sintering temperature. In addition, these components also facilitated a more abundant mullite formation and consequently improved flexural strength of the ceramic samples. The optimum ceramic properties were achieved with adding fly ash content between 10-30 wt% sintered at 1150-1200 οC. At 1200 οC, the maximum flexural strength of ceramic-FA samples with adding fly ash 10-30wt% (PSW-FA(10)-(30)) was obtained in the range of 92.25-94.71 MPa when the water absorption reached almost zero (0.03%). In terms of thermal insulation materials, the increase in fly ash addition had a positively effect on the thermal conductivity, due to the higher levels of porosity created by gas evolving from the inorganic decomposition reactions inside the ceramic-FA samples. The addition of 20-40 wt% high-calcium fly ash in ceramic samples sintered at 1150 οC reduced the thermal conductivity to 14.78-49.25%, while maintaining acceptable flexural strength values (~ 45.67-87.62 MPa). Based on these promising mechanical and thermal characteristics, it is feasible to utilize this high-calcium fly ash as an alternative raw material in clay compositions for manufacturing of ceramic tiles

Research Article
The role of Al substitution on the phase evolution in synthesized Mg2Cu nanoparticles: An insight from X-ray diffraction analysis
Elham Mohseni-Sohi and Farshid Kashani Bozorg
Available online 22 October 2021, https://doi.org/10.1007/s12613-021-2368-1
[Abstract](54) [PDF 1549KB](4)

In this study, the effect of Mg replacement with Al on the discharge capacity of Mg2Cu powder mixture is investigated. The mixture of nanocrystalline powder is prepared via mechanical alloying (MA) technique with a high energy planetary ball mill. In addition, different moles of Al are substituted to Mg2Cu powder (0.05, 0.1, 0.15, 0.2, and 0.3). X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) are used to analyze changes in structure, morphology, and grain size. The obtained powder is utilized as an anode in a nickel-metal hydride battery (Ni-MH). In the specimens with 0.05 M Al content, the orthorhombic structure of Mg2Cu is emerged after 5 hours milling. The results reveal that more than 0.2 M Al substitution leads to an appearance of MgCu2 peaks. Al substitution does not affect microstructure uniformity; however, it causes a decrease in crystalline size and lattice parameters. The SAD pattern elucidates that the electrode with the Mg1.9Al0.1Cu chemical composition and 20 hours milling has the maximum discharge capacity.

Research Article
Extraction of lithium from simulated pyrometallurgical slag of spent lithium-ion batteries by binary eutectic molten carbonates
Hui Dang, Zhidong Chang, Hualei Zhou, Sihang Ma, Min Li, and Jialing Xiang
Available online 16 October 2021, https://doi.org/10.1007/s12613-021-2366-3
[Abstract](80) [PDF 733KB](28)

Effectively extracting lithium from the pyrometallurgical slag of spent lithium-ion batteries at a relatively low temperature remains a great challenge. Herein, potassium carbonate/sodium carbonate (K2CO3/Na2CO3) which could form eutectic molten salts at 720°C were used as the roasting agents for extracting lithium from the pyrometallurgical slag. The lithium is successfully extracted from slag by K2CO3/Na2CO3 roasting followed by water leaching. According to the theoretical calculation results, lengths of Li-O bonds increase after adsorption of K+/Na+, resulting in easily release of Li+ from the lattice of LiAlSi2O6 after roasting with K2CO3/Na2CO3. Moreover, the TG-DSC results indicate that the eutectic phenomenon of K2CO3 and Na2CO3 is observed at 720°C and the reaction of slag and eutectic molten salts happens above 720°C. The X-ray diffraction results suggest that Li+ in slag is exchanged by K+ in K2CO3 which is accompanied by the formation of KAlSiO4, while Na2CO3 is mainly employed as a fluxing agent. The lithium extraction efficiency can reach 93.87% under the following optimal conditions: roasting temperature of 740°C, roasting time of 30 min, leaching temperature of 50°C, leaching time of 40 min and water/roasted samples mass ratio of 10:1. This work provides a new system for extracting lithium from the pyrometallurgical slag of spent lithium-ion batteries.

Research Article
Optimisation of alloy composition for highly-formable magnesium sheet
Zhuoran Zeng, Mingzhe Bian, Shiwei Xu, Weineng Tang, Chris Davies, Nick Birbilis, and Jianfeng Nie
Available online 15 October 2021, https://doi.org/10.1007/s12613-021-2365-4
[Abstract](158) [PDF 2229KB](22)

The effectiveness of Ca or Gd addition on ductility and formability of Mg-Zn-Zr based dilute alloys in deep drawing has not been systematically compared previously. In this study, formable Mg-Zn-Gd-Zr and Mg-Zn-Ca-Zr sheet alloys are produced by hot rolling. These sheets have similarly weakened basal texture, but the sheet of the Mg-Zn-Gd-Zr alloys has higher ductility and formability than that of Mg-Zn-Ca-Zr alloys. The combined addition of 0.2 wt.% Ca and 0.4 wt.% Gd to the Mg-1Zn-0.5Zr (wt.%) alloy leads to a Mg-1Zn-0.4Gd-0.2Ca-0.5Zr alloy that has even better ductility and its formability during deep drawing is comparable to the benchmark Al6016 sheet. An increase in Ca concentration from 0.2 wt.% to 0.5 wt.% leads to decreased sheet ductility and formability, predominantly due to grain boundary embrittlement.

Research Article
Optimize two-phase distribution of lithium-rich materials to stabilize structure and suppress voltage attenuation
Yang Yu, Jianling Li, Guimei Han, Zhe Yang, Jianjian Zhong, and Feiyu Kang
Available online 12 October 2021, https://doi.org/10.1007/s12613-021-2362-7
[Abstract](66) [PDF 1253KB](7)

Lithium-rich materials possess ultra-high specific capacity, but the redox of oxygen is not completely reversible, resulting in voltage attenuation and structural instability. A stepwise co-precipitation method is used for the first time in this paper to achieve the control of the two-phase distribution through controlling the distribution of transition metal elements and realize the modification of particle surface structure without the aid of heterologous ions. The results of characterization tests show that the content of LiMO2 phase inside the particles and the content of Li2MnO3 phase on the surface of the particles are successfully increased, and the surface induced formation of Li4Mn5O12 spinel phase or some disorderly ternary. The electrochemical performance of the modified sample is as follows: LR (pristine) shows specific discharge capacity of 72.7 mA h g-1 after 500 cycles at 1C, while GR (Modified sample) shows specific discharge capacity of 137.5 mA h g-1 at 1C, and the discharge mid-voltage of GR still remains above 3 V when cycling to 220 cycles at 1C (mid-voltage of LR remains above 3 V when cycling to 160 cycles at 1C). Therefore, deliberately regulating the local state of the two phases is an successful way to reinforced the material structure and inhibition the voltage attenuation.

Research Article
Self-assembled TiO2 hole blocking layers for efficient perovskite solar cells
Zhongbao Que, Liang Chu, Shuaibo Zhai, Yifei Feng, Chen Chen, Wei Liu, Ruiyuan Hu, Jing Hu, and Xing’ao Li
Available online 1 October 2021, https://doi.org/10.1007/s12613-021-2361-8
[Abstract](91) [PDF 864KB](5)

Self-assembled process for device functional layers is a simple, feasible and energy-saving strategy. In mesoporous PSCs, compact and scaffold TiO2 films generally function as the hole blocking and electron transporting layers, respectively. However, they are both typically generated through high-temperature annealing. Here, we deposited TiO2 compact films by a room-temperature self-assembled process, which were conducted as an effective hole blocking layer for perovskite solar cells. The thickness of TiO2 compact films can be easily controlled by the deposition time. By optimizing the TiO2 compact films (80 nm), the power conversion efficiency of mesoporous perovskite solar cells without and with hole conductor layers was up to 10.66% and 17.95%, respectively. Interestingly, an all-low-temperature planar perovskite solar cell with the self-assembled TiO2 layer achieve power conversion efficiency of 16.42%.

Research Article
Effect of heat treatment temperature on the structure and the formaldehyde removal performance of an interior wall tile
Ruqin Gao, Yingrui Huang, Enhui Wang, Xinmei Hou, Lu Pan, Guoting Li, and Bingtao Liu
Available online 30 September 2021, https://doi.org/10.1007/s12613-021-2359-2
[Abstract](71) [PDF 504KB](3)

A diatomite-based porous ceramic support has been prepared using solid-phase sintering and low-temperature calcination processes. Using diatomite as the main raw material, adding appropriate amount of tourmaline and sintering aids to the glaze, and combining different heat treatment temperatures of the glaze layer, tourmaline/diatomite-based interior wall tiles are prepared. The glaze layer under different heat treatment temperatures is characterized by thermogravimetric-differential thermal analysis, X-ray diffraction and scanning electron microscope. The influences of heat treatment temperature on the microscopic morphology and structure of the glaze layer are analyzed. Taking formaldehyde as the target degradation product, the effects of tourmaline/diatomite-based interior wall tiles on the removal of formaldehyde under different heat treatment temperatures of the glaze layer are investigated. The results show that with the increase of heat treatment temperature, the original pores of diatomite decreases, and the specific surface area, and the structure of tourmaline changes. The surface structure of the material is slightly damaged at 850℃, the strength is increased, and the removal effect of formaldehyde is better. In a 1 m3 environmental chamber, the formaldehyde removal rate reaches 73.6% in 300 min. When the temperature is increased to 950℃ and above, diatomite and the structure of tourmaline are destroyed, and the ability of the material to adsorb and degrade formaldehyde decreases.

Invited Review
A brief review on fabrication and application of porous materials from silicon-rich industrial solid waste
Chao Miao, Lixing Liang, Shumei Chen, Kaixuan Shang, Yi Zhang, and Jing Ouyang
Available online 30 September 2021, https://doi.org/10.1007/s12613-021-2360-9
[Abstract](117) [PDF 1482KB](20)

Porous materials have many promising prospects in such fields as sound insulation, heat barrier, vibration attenuation, and catalysts, due to their special porous structures. Most of the industrial solid wastes such as tailings, coal gangue, and fly ash are rich in silicon. As far as this is concerned. In this regard, the high silicon content makes it a potential raw material for the synthesis of silicon-based multi-porous materials such as zeolites, mesoporous silica, glass ceramics, geopolymer foams, etc. In this mini review, the representative silicon-rich industrial solid wastes (SRISW) are selected as the objects, which focused on the processing and application of silicon porous materials from the aspects of physical and chemical properties of SRISW. The transformation methods of preparing porous materials from silicon rich industrial solid wastes are summarized, and their research status in micro-, meso-, and macro-scale porous materials are concluded, respectively. Also the possible problems existing in the application of silicon-rich industrial solid wastes, and in the preparation of functional porous materials are analyzed, and their developing orientation is prospected. This review should provide a typical reference for the recycling and utilization of industrial solid wastes to develop some sustainable “green materials”.

Invited Review
Carbon materials: The burgeoning promise in electronics
Yuting Zheng, Junjun Wei, Jinlong Liu, Liangxian Chen, Kang An, Xiaotong Zhang, Haitao Ye, Xiaoping Ouyang, and Chengming Li
Available online 28 September 2021, https://doi.org/10.1007/s12613-021-2358-3
[Abstract](84) [PDF 1381KB](6)

Current electronic technology based on silicon is approaching to its physical and scientific limits. When facing the compulsory choice of finding a practicable way of potential material alternatives for next generation electronics, carbon-based devices showing numerous superiorities (e.g., fast speed, low power consumption and simple process) combining with the unique nature of versatile allotropes of carbon element are unfolding the promise of upcoming electronics revolution. Now it is the time that carbon electronics are greatly advancing with not only developed preparation but also sophisticated design. In this perspective, the representatives with various dimensions, e.g., carbon nanotubes, graphene, bulk diamond, together with extraordinary performance are reviewed. Based on these members of carbon materials family, the associated state-of-the-art devices and composite hybrid all-carbon structures are also emphasized to embody their inherent dominances in the electronics field. Advances of commercial production with improved cost-efficiency and material quality as well as devices design are ongoingly accelerating to the bright future, and it is virtually even impossible to keep up with this burgeoning situation.

Research Article
Influence of rare earth Ce on hot deformation behavior of as-cast Mn18Cr18N high nitrogen austenitic stainless steel
Yushuo Li, Yanwu Dong, Zhouhua Jiang, Qingfei Tang, Shuyang Du, and Zhiwen Hou
Available online 23 September 2021, https://doi.org/10.1007/s12613-021-2355-6
[Abstract](67) [PDF 2158KB](10)

In this paper, hot deformation behavior of Mn18Cr18N and Mn18Cr18N+Ce high nitrogen austenitic stainless steel at 1173~1473 K and 0.01~1 s-1 are investigated by thermal compression tests. Influence mechanism of Ce on the hot deformation behavior is analyzed by Ce-containing inclusions and segregation of Ce. The results show that, after adding Ce, large, angular, hard and brittle inclusions (TiN-Al2O3, TiN and Al2O3) can be modified to fine and dispersed Ce-containing inclusions (Ce-Al-O-S and TiN-Ce-Al-O-S). During the solidification, Ce-containing inclusions can be used as heterogeneous nucleation particles to refine as-cast grains. During the hot deformation, Ce-containing inclusions can pin dislocation movement and grain boundary migration, induce dynamic recrystallization (DRX) nucleation, and avoid the formation and propagation of micro cracks and gaps. In addition, During the solidification, Ce atoms will enrich at the front of solid-liquid interface, resulting in composition supercooling and refining the secondary dendrites. Similarly, during the hot deformation, Ce atoms tend to segregate at the boundaries of DRX grains, inhibiting the growth of grains. Under the synergistic effect of Ce-containing inclusions and Ce segregation, although the hot deformation resistance and hot deformation activation energy are improved, DRX is more likely to occur and the size of DRX grains is significantly refined, and the problem of hot deformation cracking can be alleviated. Finally, the microhardness of samples was measured. The results showed that, compared with as-cast samples, the microhardness of hot-deformed samples increases significantly, and with the increase of DRX degree, the microhardness decreases continuously. In addition, Ce can affect the microhardness of Mn18Cr18N steel by affecting as-cast and hot deformation microstructure.

Research Article
Enhancing formability of FeSi6.5 steel by anodic polarization
Dong Zhao, Feng Ye, Binbin Liu, Haoyang Du, Yaakov B. Unigovski, Emmanuel M. Gutman, and Roni Shneck
Available online 23 September 2021, https://doi.org/10.1007/s12613-021-2356-5
[Abstract](77) [PDF 610KB](9)

The effect of anodic polarization on plastic deformation behavior and formability of FeSi6.5 steel at room temperature was experimentally investigated through uniaxial tensile and drawing of wire specimen in sulfuric acid solution with current densities of 0-40 mA/cm2. The formability of the FeSi6.5 steel was significantly improved after the anodic polarization. The plastic elongation of the specimen as an anode in the electrochemical environment was 4.4-7%, but 2.7% in the air. The drawing force under the anodic polarization decreased by 12.5-26% compared to that in deionized water. The softening is mainly attributed to the relief in work hardening caused by surface atomic dissolution. The work hardening mechanism of the FeSi6.5 steel wires under anodic polarization condition was analyzed using Hollomon equation and Voce relation combined with the K-M approach. These data support the view that the surface atom dissolution facilitates dislocation slip. FeSi6.5 steel wires were obtained using electrochemical cold drawing and presented a smooth surface and good ductility without crack after five-pass drawing with a total cross-section area reduction of 88%. The drawing with the assistance of anodic polarization is a promising technology for processing hard and brittle metal materials.

Research Article
Effect of extrusion on the microstructure and mechanical properties of a low-alloyed Mg-2Zn-0.8Sr-0.2Ca matrix composite reinforced by TiC nano-particles
Zedong Wang, Kaibo Nie, Kunkun Deng, and Jungang Han
Available online 14 September 2021, https://doi.org/10.1007/s12613-021-2353-8
[Abstract](93) [PDF 701KB](15)

In this work, a low-alloyed Mg-2Zn-0.8Sr-0.2Ca matrix composite reinforced by TiC nano-particles is successfully prepared by semi-solid stirring under the assistance of ultrasonic and then the as-cast composite is hot extruded. The results indicate that the volume fraction of dynamical recrystallization and the recrystallized grain size have a certain decline at lower extrusion temperature or rate. The finest grain size of ~0.30 µm is obtained in the sample extruded at 200℃ and 0.1 mm/s. The as-extruded sample displays a strong basal texture intensity, and the basal texture intensity increases to 5.937 mud while the extrusion temperature increases from 200℃ to 240℃. The ultra-high mechanical properties (ultimate tensile strength of 480.2 MPa, yield strength of 462 MPa) are obtained after extrusion at 200℃ with a rate of 0.1 mm/s. Among all strengthening mechanisms for the present composite, grain refinement contributes the most to the increase in strength. A mixture of cleavage facets and dimples are observed in the fracture surfaces of three as-extruded nanocomposites, which explain a mix of brittle-ductile fracture way of the samples.

Research Article
Effect of samarium on N2 selectivity of SmxMn0.3−xTi catalysts during selective catalytic reduction of NOx with NH3
Shengyang Zhang, Bolin Zhang, Boyu Wu, Bo Liu, and Shengen Zhang
Available online 7 September 2021, https://doi.org/10.1007/s12613-021-2348-5
[Abstract](88) [PDF 863KB](9)

The objective of this work is to study the improvement effect of Sm on Mn-based catalysts for selective catalytic reduction (SCR) of NO with NH3. A series of SmxMn0.3–xTi catalysts (x = 0, 0.1, 0.15, 0.2, 0.3) were prepared by co-precipitation. The activity tests indicated that the Sm0.15Mn0.15Ti catalyst showed superior performances with NO conversion of 100% and N2 selectivity above 87% at 180–300°C. The characterizations showed that the doping of Sm suppressed the crystallization of TiO2 and Mn2O3 phases, and increased the specific surface area and acidity. Especially, the surface area increased from 152.2 m2·g−1 of Mn0.3Ti to 241.7 m2·g−1 of Sm0.15Mn0.15Ti. These all contributed to the catalytic activity. The XPS results indicated that the relative atomic ratios of Sm3+/Sm and Oβ/O of Sm0.15Mn0.15Ti were 76.77% and 44.11%, respectively. The existence of Sm contributed to the increase of surface absorbed oxygen (Oβ) and the decrease of the surface concentration of Mn4+, which improved the catalytic activity. In the results of H2-TPR, the presence of Sm induced higher reduction temperature and lower H2 consumption (0.3 mmol g–1) of Sm0.15Mn0.15Ti catalyst than that of Mn0.3Ti catalyst. The decrease of Mn4+ weakened the redox property of the catalysts, and increased the N2 selectivity by suppressing the formation of N2O from both NH3 oxidation and nonselective catalytic reduction reaction. The results of in situ DRIFT spectra revealed that the NH3-SCR of NO over Sm0.15Mn0.15Ti catalyst mainly followed the Eley-Rideal mechanism. The Sm doping increases surface absorbed oxygen and weakens the redox property to improve the NO conversion and N2 selectivity of Sm0.15Mn0.15Ti catalyst.

Research Article
Effect of the capsule on deformation and densification behavior of nickel-based superalloy compact during hot isostatic pressing
Lebiao Yang, Xiaona Ren, Chao Cai, Pengju Xue, M. Irfan Hussain, Yusheng Shi, and Changchun Ge
Available online 7 September 2021, https://doi.org/10.1007/s12613-021-2349-4
[Abstract](91) [PDF 1458KB](6)

The Shima yield criterion used in finite element analysis for nickel-based superalloy powder compact during hot isostatic pressing (HIP) was modified through uniaxial compression experiments. The influence of cylindrical capsule characteristics on FGH4096M superalloy powder compact deformation and densification behavior during HIP was investigated through simulations and experiments. Results reveals the simulation shrinkage prediction fitted well with the experimental shrinkage including a maximum shrinkage error of 1.5%. It was shown that the axial shrinkage was 1.7% bigger than radial shrinkage for a cylindrical capsule with the size of Φ50 mm × 100 mm due to the force arm difference along the axial and radial direction of the capsule. The stress deviated from the isostatic state in the capsule led to the uneven shrinkage and non-uniform densification of the powder compact. The ratio of the maximum radial displacement to axial displacement increased from 0.47 to 0.75 with the capsule thickness increased from 2 mm to 4 mm. The pressure transmission was related to the capsule thickness and the capsule material performance, and physical parameters in the HIP process.

Research Article
In-situ observation of the kinetic dissolution of Al2O3 particles in CaO-Al2O3-SiO2 slags using laser confocal scanning microscopy
Changyu Ren, Caide Huang, Lifeng Zhang, and Ying Ren
Available online 31 August 2021, https://doi.org/10.1007/s12613-021-2347-6
[Abstract](99) [PDF 677KB](17)

The dissolution kinetics of Al2O3 in CaO-Al2O3-SiO2 slags was studied using high-temperature confocal scanning laser microscope at 1773 to 1873 K. The results show that the controlling step during the Al2O3 dissolution was diffusion in the molten slag. It was found that dissolution curves of Al2O3 particles was hardly agreed with the traditional boundary layer diffusion model with the increase of the CaO/Al2O3 of slag. A modified diffusion equation considering slag viscosity was developed to study the dissolution mechanism of Al2O3 in slag. Diffusion coefficients of Al2O3 in slag were calculated as 2.8 ×10-10 to 4.1 ×10-10 m2/s. The dissolution rate of Al2O3 increased with higher temperature, CaO/Al2O3, and particle size. A new model was shown to be vAl2O3 = 0.16 × R01.58 × x3.52 × (T-Tmp)1.11 to predict the dissolution rate and the total dissolution time of Al2O3 inclusions with various sizes.

Research Article
Mg-intercalation engineering of MnO2 electrode for high-performance aqueous magnesium-ion batteries
Yue Zhao, Bei Wang, Minjie Shi, Shibo An, Liping Zhao, and Chao Yan
Available online 31 August 2021, https://doi.org/10.1007/s12613-021-2346-7
[Abstract](152) [PDF 1353KB](15)

Rechargeable aqueous magnesium-ion batteries (MIBs) show great promise for low-cost, high-safety, and high-performance energy storage applications. Although manganese dioxide (MnO2) is considered as a potential electrode material for aqueous MIBs, the low electrical conductivity and unsatisfactory cycling performance greatly hinder the practical application of MnO2 electrode. To overcome these problems, herein, a novel Mg-intercalation engineering approach for MnO2 electrode to be used in aqueous MIBs is presented, wherein the structural regulation and electrochemical performance of the Mg-intercalation MnO2 (denoted as MMO) electrode are thoroughly investigated by Density functional theory (DFT) calculations and in-situ Raman investigation. The results demonstrate that the Mg intercalation is essential to adjusting the charge/ion state and electronic band gap of MMO electrode, as well as the highly reversible phase transition of the MMO electrode during the charging–discharging process. Because of these remarkable characteristics, the MMO electrode can be capable of delivering a significant specific capacity of ~419.8 mAh g-1, while exhibiting a good cycling capability over 1000 cycles in 1 M aqueous MgCl2 electrolyte. On the basis of such MMO electrode, we have successfully developed a soft-packaging aqueous MIB with excellent electrochemical properties, revealing its huge application potential as the efficient energy storage devices.

Research Article
Effect of Co2+ substitution in B-sites of the perovskite system on the phase formation, microstructure, electrical and magnetic properties of Bi0.5(Na0.68K0.22Li0.10)0.5TiO3 ceramics
Pamornnarumol Bhupaijit, Chonnarong Kaewsai, Tawat Suriwong, Supree Pinitsoontorn, Surirat Yotthuan, Naratip Vittayakorn, and Theerachai Bongkarn
Available online 26 August 2021, https://doi.org/10.1007/s12613-021-2345-8
[Abstract](123) [PDF 1368KB](28)

Bi0.5(Na0.68K0.22Li0.10)0.5Ti1-xCoxO3 lead-free perovskite ceramics (BNKLT-xCo, x = 0, 0.005, 0.010, 0.015 and 0.020) were fabricated via the solid-state combustion technique. A small-amount of Co2+ ion substitution into Ti-sites led to modification of the phase formation, microstructure, electrical and magnetic properties of BNKLT ceramics. Coexisting rhombohedral and tetragonal phases were observed in all samples using the XRD technique. The Rietveld refinement revealed that the rhombohedral phase increased from 39 to 88 % when x increased from 0 to 0.020. The average grain size increased when x increased. With increasing x, more oxygen vacancies were generated, leading to asymmetry in the S-E loops. For the composition of x = 0.010, a high dielectric constant (m) of 5384 and a large strain (Smax) of 0.23 % with d33* (Smax/Emax) of 460 pm/V were achieved. The BNKLT-0Co ceramic showed diamagnetic behavior but all of the BNKLT-xCo ceramics exhibited paramagnetic behavior, measured at 50 K.

Research Article
Bioleaching and biosorption behavior of vanadium-bearing stone coal by Bacillus mucilaginosus
Yingbo Dong, Shijia Chong, and Hai Lin
Available online 21 August 2021, https://doi.org/10.1007/s12613-021-2344-9
[Abstract](427) [PDF 605KB](45)

The recovery of vanadium (V) from stone coal by bioleaching is a promising method. The bioleaching experiments and the biosorption experiments were carried out, aiming to explore the adsorption characteristics of Bacillus mucilaginosus (B. mucilaginosus) on the surface of vanadium-bearing stone coal, and the related mechanisms have been investigated. After bioleaching at 30°C for 28 days, the cumulative leaching rate of V reached 60.2%. The biosorption of B. mucilaginosus on stone coal was affected by many factors. When the leaching system pH=5.0, strong electrostatic attraction between bacteria and stone coal promoted biosorption. Bacteria in the logarithmic growth phase had mature and excellent biosorption properties. The initial bacterial concentration of 3.5×108 cfu/mL was conducive to adhesion, with 38.9% adsorption rate and 3.6×107 cfu/g adsorption quantity. The adsorption of B. mucilaginosus on the stone coal conformed to the Freundlich model and the pseudo-second-order kinetic model. Bacterial surface carried functional groups (-CH2, -CH3, -NH2, et al.), which were highly correlated with the adsorption behavior. In addition, biosorption changed the surface properties of stone coal, resulting in the isoelectric point (IEP) approaching the bacteria. The results of our study could provide an effective reference for the adsorption laws of bacteria on minerals.

Invited Review
Research progress of interface modification and thermal conduction behavior of diamond/metal composites
Ping Zhu, Pingping Wang, Puzhen Shao, Xiu Lin, Ziyang Xiu, Qiang Zhang, Equo Kobayashi, and Gaohui Wu
Available online 18 August 2021, https://doi.org/10.1007/s12613-021-2339-6
[Abstract](107) [PDF 1152KB](16)

Diamond/metal composites are widely used in national defense technology and national production due to their outstanding properties of high thermal conductivity and low expansion. However, the difference of chemical properties leads to the interface incompatibility between diamond and metal, which has an important impact on the properties of the composites. Interfacial modification is an effective way to improve the interfacial bonding and reduce the interfacial thermal resistance. This paper reviews the experimental research on interface modification of diamond/metal composites and the application of material calculation simulation in diamond/metal composites. Combining computational simulation and experiment is an expected method to advance the research of diamond/metal composite interface modification.

Research Article
Effects of Li addition on microstructures and tensile properties of the extruded Mg–1Zn–xLi alloy
Jun Zhao, Bin Jiang, Qinghang Wang, Ming Yuan, Yanfu Chai, Guangsheng Huang, and Fusheng Pan
Available online 18 August 2021, https://doi.org/10.1007/s12613-021-2340-0
[Abstract](164) [PDF 1527KB](11)

Li addition is verified to be an effective method to increase the room temperature ductility and formability of Mg alloys. In the present study, the microstructure, texture and tensile properties of extruded Mg–1Zn–xLi (wt%, x=0, 1, 3, 5) alloy sheets were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), and electron backscatter diffraction (EBSD). It is found that Li addition resulted in the grain coarsening and the development of new transverse direction (TD)–tilting and 〈10–10〉 parallel to extrusion direction textures, which was related to the improved dynamic recrystallization and the increased prismatic slip during extrusion. The Mg–1Zn–5Li sheet showed the weakest texture, which contained both basal and TD–tilting oriented grains. No additional phase was formed with Li addition. Tensile properties showed that the yield strength of Mg–1Zn–xLi sheets gradually decreased with increasing Li content, which was mainly related to grain coarsening and texture weakening. In addition, the ductility of the Mg–1Zn–xLi sheet was remarkably enhanced by Li addition. The elongation of the Mg–1Zn–5Li sheet was 30.3% along the transverse direction, which was three times than that of Mg–1Zn sheet. Microstructural analysis implied that this significant ductility enhancement was associated with the improvement activation of prismatic and basal slips during the tensile tests. This study may provide insights into the development of high-ductility, low-density Mg–Zn–Li based alloys.

Research Article
Titanium dioxide-graphene composite electrochemical sensor for detection of hexavalent chromium
Natpichan Pienutsa, Krittamet Yannawibut, Jetthana Phattharaphongmanee, Oukrit Thonganantakul, and Sira Srinives
Available online 12 August 2021, https://doi.org/10.1007/s12613-021-2338-7
[Abstract](210) [PDF 863KB](17)

Hexavalent chromium (Cr(VI)) compound is useful to various industries but is toxic and carcinogenic. In this research work, we fabricate an amperometric sensor for the determination of Cr(VI), using a titanium dioxide (TiO2)-reduced graphene oxide (rGO) composite as the sensing element. The composite was synthesized following sol-gel chemistry, yielding TiO2 nanoparticles of ~50 nm in size, immobilized on chemically exfoliated rGO sheets. The composite was employed in a 3-electrode electrochemical cell and operated in an amperometric mode, exhibiting good responses to the 50 to 500 ppb Cr(VI). Our best result from pH 3 Mcilvane’s buffer solution reveals the sensitivity of 9.12x10-4 ppb-1 and a detection limit of 6 ppb with no signal interference from 200 ppm Ca(II), 150 ppm Mg(II), and 50 ppb Pb(II). The excellent results of the TiO2-rGO sensor can be attributed to synergic effects between TiO2 and rGO, resulting from the presence of n-p heterojunctions and the formation of the TiO2 nanoparticles on rGO.

Research Article
Effect of chromium interlayer thickness on interfacial thermal conductance across copper/diamond interface
Xiaoyan Liu, Fangyuan Sun, Luhua Wang, Zhanxun Che, Guangzhu Bai, Xitao Wang, Jinguo Wang, Moon J. Kim, and Hailong Zhang
Available online 29 July 2021, https://doi.org/10.1007/s12613-021-2336-9
[Abstract](185) [PDF 1745KB](28)

The thermal conductivity of diamond particles reinforced copper matrix  composite as an attractive thermal management material is significantly lowered by the non-wetting heterointerface. The paper investigates the heat transport behavior between a 200 nm Cu layer and a single-crystalline diamond substrate inserted by a chromium (Cr) interlayer having a series of thicknesses from 150 nm down to 5 nm. The purpose is to detect the impact of the modifying interlayer thickness on the interfacial thermal conductance (h) between Cu and diamond. The time-domain thermoreflectance measurements suggest that the introduction of Cr interlayer dramatically improves the h between Cu and diamond owing to the enhanced interfacial adhesion and bridged dissimilar phonon states between Cu and diamond. The h value exhibits a decreasing trend as the Cr interlayer becomes thicker because of the increase in thermal resistance of Cr interlayer. The high h values are observed for the Cr interlayer thicknesses below 21 nm since phononic transport channel dominates the thermal conduction in the ultrathin Cr layer. The findings provide a way to tune the thermal conduction across the metal/nonmetal heterogeneous interface, which plays a pivotal role in designing materials and devices for thermal management applications.

Research Article
Effect of chemical composition on the micromorphology, phase composition, and calcification roasting process of vanadium slag
Tangxia Yu, Tao Jiang, Jing Wen, Hongyan Sun, Ming Li, and Yi Peng
Available online 24 July 2021, https://doi.org/10.1007/s12613-021-2334-y
[Abstract](143) [PDF 1739KB](15)

The chemical composition of vanadium slag significantly affects its element distribution and phase composition, which affect the subsequent calcification roasting process and vanadium recovery. In this work, seven kinds of vanadium slags derived from different regions in China were used as the raw materials to study the effects of different components on the vanadium slag’s micromorphology, phase composition, calcification roasting, and leaching rate of major elements using SEM, XRD, and ICP-AES. The results showed that the spinel phase was wrapped with silicate phase in all vanadium slag samples. The main elements in the spinel phase were Cr, V, and Ti from the interior to the exterior. The size of spinel phase in low chromium vanadium slag was larger than other vanadium slags with higher chromium contents. The spinel phase of high-calcium and high-phosphorus vanadium slag was more dispersed. The strongest diffraction peak of vanadium spinel phase in vanadium slag migrated to a higher diffraction angle, and (Fe0.6Cr0.4)2O3 was formed after calcification roasting as the chromium content increased. A large amount of Ca2SiO4 was produced because excess Ca reacted with Si in high-calcium and high-phosphorus vanadium slag. The vanadium leaching rates reached 88% in some vanadium slags. The chromium leaching rates were less than 5% in all vanadium slags. The silicon leaching rate in high-calcium and high-phosphorus vanadium slag was much higher than other slags. The leaching rates of manganese were higher than 10%, and the leaching rate of iron and titanium were negligible.

Research Article
The effects of shape and particle size on the photocatalytic kinetics and mechanism of nano-CeO2
Zixiang Cui, Lu Zhang, Yongqiang Xue, Yanan Feng, Mengying Wang, Jiaojiao Chen, Boteng Ji, Chenyu Wang, and Yidi Xue
Available online 20 July 2021, https://doi.org/10.1007/s12613-021-2332-0
[Abstract](139) [PDF 889KB](10)

Nanomaterials have been widely applied to many fields because of their excellent photocatalytic performance. The performance is closely related to the catalytic kinetics, but it is not completely clear that the influencing regularities of shape and particle size on the photocatalytic kinetics of nanomaterials and the photocatalytic kinetic mechanism. In this paper, nano-CeO2 with different shapes and particle sizes were prepared, the kinetic parameters of adsorption and photocatalytic degradation were determined, and the effects of shape and particle size on the kinetics of adsorption and photocatalysis and photocatalytic mechanism were discussed. The results show that the shape and particle size have significant influences. With the decreases of diameter, the performances of adsorption and photocatalysis of nano-CeO2 are improved; and these performances of spherical nano-CeO2 are greater than those of linear nano-CeO2. The shape and particle size have no effects on the kinetic order and mechanism of the whole photocatalytic process. Then a generalized mechanism of photocatalytic kinetics of nanomaterials was proposed and the mechanism rate equation was derived. Finally, the conclusion can be drawn: the desorption of photodegradation products is the control step of photocatalytic kinetics, and the kinetic order of photocatalytic degradation reaction is 1. The mechanism is universal and all nanomaterials have the same photocatalytic kinetic mechanism and order.

Research Article
Effects of Zr content on electrochemical performance of Ti/Sn-Ru-Co-ZrOx electrodes
Linhui Chang, Sheng Chen, Xionghui Xie, Buming Chen, Haihong Qiao, Hui Huang, Zhong-cheng Guo, Yapeng He, and Ruidong Xu
Available online 7 July 2021, https://doi.org/10.1007/s12613-021-2326-y
[Abstract](276) [PDF 891KB](36)

The low cell voltage during electrolytic Mn from the MnCl2 system can effectively reduce the power consumption. In this work, the Ti/ Sn-Ru-Co-Zr modified anodes were obtained by using thermal decomposition oxidation. The physical parameters of coatings were observed by SEM. Based on the electrochemical performance and SEM/XRD of the coatings, the influences of Zr on electrode performance were studied and analyzed. When the mole ratio of Sn-Ru-Co-Zr = 6:1:0.8:0.3, the cracks on the surface of coatings were the smallest, and the compactness was the best due to the excellent filling effect of ZrO2 nanoparticles. Moreover, the electrode prepared under this condition had the lowest mass transfer resistance and high chloride evolution activity in the 1M NH4Cl + 1.5M HCl system. The service life of 3102 h was achieved according to the empirical formula of accelerated-life-test of the new type anode.

Research Article
Effect of trace yttrium on the microstructure, mechanical property, and corrosion behavior of homogenized Mg-2Zn-0.1Mn-0.3Ca-xY biological magnesium alloy
Liangyu Wei, Mingfan Qi, Yuzhao Xu, Jingyuan Li, Jin Wang, Aisen Liu, and Jicheng Wang
Available online 7 July 2021, https://doi.org/10.1007/s12613-021-2327-x
[Abstract](105) [PDF 1933KB](7)

The effects of trace yttrium (Y) element on the microstructure, mechanical properties, and corrosion resistance of Mg-2Zn-0.3Ca-0.1Mn-xY (x=0, 0.1, 0.2, 0.3) biological magnesium alloys are investigated. Results show that grain size decreases from 310μm to 144μm when the Y content increases from 0 wt.% to 0.3 wt.%. At the same time, the volume fraction of the second phase increases from 0.4% to 6.0%, the yield strength of the alloy continues to increase, and the ultimate tensile strength and elongation decrease initially and then increase. When the Y content element increases to 0.3 wt.%, Mg3Zn6Y phase begins to precipitate in the alloy; thus, the alloy exhibits the most excellent mechanical property. At this time, its ultimate tensile strength, yield strength, and elongation are 119MPa, 69MPa, and 9.1%, respectively. In addition, when the Y content is 0.3 wt.%, the alloy shows the best corrosion resistance in the simulated body fluid (SBF). This investigation has revealed that the improvement of mechanical properties and corrosion resistance is mainly attributed to the grain refinement and the precipitated Mg3Zn6Y phase.

Research Article
Oxidation resistance of PM Ti-45Al-10Nb alloy at high temperature
Xuchen Jin, Peihao Ye, Hongrui Ji, Zhuanxia Suo, Boxin Wei, Xuewen Li, and Wenbin Fang
Available online 24 June 2021, https://doi.org/10.1007/s12613-021-2320-4
[Abstract](101) [PDF 1068KB](3)

TiAl alloy with high Nb content, nominally Ti-45Al-10Nb, was prepared by powder metallurgy, and the oxidation resistance at 850, 900, and 950℃ was investigated. The high-temperature oxidation-resistance mechanism and oxidation dynamics were discussed following the oxide skin morphology and microstructural evolution analysis. The oxide skin structures were similar for 850 and 900℃, with TiO2+Al2O3 mixture covering TiO2 with dispersed Nb2O5. At 950℃, the oxide skin was divided into four sublayers, from the outside to the parent metal: loose TiO2+Al2O3, dense Al2O3, dense TiO2+Nb2O5, and TiO2 matrix with dispersed Nb2O5. The Nb layer suppressed the outward diffusion of Ti atoms, hindering the growth of TiO2, and simultaneously promote the formation of a continuous Al2O3 protective layer, providing the alloy with long-term high-temperature oxidation resistance.

Research Article
Utilization of DTAB as a collector for reverse flotation separation of quartz from fluorapatite
Wenbiao Liu, Wenxuan Huang, Feng Rao, Zhanglei Zhu, Yongming Zheng, and Shuming Wen
Available online 24 June 2021, https://doi.org/10.1007/s12613-021-2321-3
[Abstract](342) [PDF 481KB](11)

Reverse flotation desilication has been an indispensable step for obtaining high-grade fluorapatite. In this work, Dodecyl Trimethyl Ammonium Bromide (DTAB) was recommended as an efficient collector for the reverse flotation separation of quartz from fluorapatite. Its collectivity for quartz and selectivity for fluorapatite were also compared with the figures corresponding to the conventional collector dodecylamine hydrochloride (DAC) via micro-flotation experiments. The adsorption behaviors of both DTAB and DAC on minerals were systematically investigated with surface chemical analyses such as contact angle determination, zeta potential detection, and adsorption density measurement. It was revealed that compared to DAC, DTAB displayed similar and strong collectivity for quartz, while it showed a better selectivity (or worse collectivity) for fluorapatite, resulting in a high-efficiency for the separation of the two minerals. Surface chemical analyses showed that the adsorption ability of DTAB on quartz surface was as strong as DAC, while the adsorption amount of DTAB on fluorapatite surface was much lower than that of DAC, which associated to the flotation performance well. During the floatation separation of the actual ore, 8% fluorapatite with higher grade can be obtained by using DTAB in contrast to DAC. Therefore, DTAB is a promising collector to the high-efficiency purification and sustainable utilization of the valuable fluorapatite recourses.

Research Article
Influences of multiple laser shock peening impacts on microstructure and mechanical properties of Ti-6Al-4V alloy fabricated by electron beam melting
Liang Lan, Ruyi Xin, Xinyuan Jin, Shuang Gao, and Bo He
Available online 24 June 2021, https://doi.org/10.1007/s12613-021-2322-2
[Abstract](191) [PDF 1248KB](11)

Laser shock peening (LSP) is an attractive post-processing method to tailor surface microstructure and enhance mechanical performances of additive manufactured (AM) components. The effects of multiple LSP impacts on the microstructure and mechanical properties of Ti-6Al-4V part produced by electron beam melting (EBM), as a mature AM process, were studied in this work. Microstructure, surface topography, residual stress and tensile performance of EBM-manufactured Ti-6Al-4V specimens were systematically analyzed subjected to different LSP impacts. The distribution of porosities in EBM sample was assessed via X-ray computed tomography. The results show that EBM samples with two LSP impacts possess a lower porosity value of 0.05% compared to the value of 0.08% for untreated samples. The strength of EBM samples with two LSP impacts is remarkably raised by 12% as compared with the as-built samples. The grains of α phase is refined in near-surface layer and a dramatic increase in the depth and magnitude of compressive residual stress (CRS) is achieved in EBM sample with multiple LSP treatments. The grain refinement of α phase and CRS with larger depth are responsible for the strength enhancement of EBM samples with two LSP impacts.

Research Article
Effects of the incorporation amount of CdS and Cd(SCN2H4)2Cl2 on the performance of perovskite solar cells
Jihong Zheng, Liangxin Zhu, Zhitao Shen, Fumin Li, Lanyu Ling, Huilin Li, and Chong Chen
Available online 12 June 2021, https://doi.org/10.1007/s12613-021-2316-0
[Abstract](224) [PDF 1100KB](15)

An excellent organolead halide perovskite film plays an important role for good-performance perovskite solar cells (PSCs), while there are many defects at perovskite crystals, which is bad for both the photovoltaic properties and the stability of solar cells. Therefore, a strategy of incorporating a complex of CdS and Cd(SCN2H4)2Cl2 into CH3NH3PbI3 active layer is proposed to solve this problem. This study systematically analyzes the effect of different doping concentration of CdS and Cd(SCN2H4)2Cl2 on the performance and stability of PSCs. Our results find that an appropriate incorporation concentration of CdS and Cd(SCN2H4)2Cl2 doped in CH3NH3PbI3 can improve the performance of the prepared solar cells, which is mainly due to that the CdS and Cd(SCN2H4)2Cl2 can effectively passivate the defects at perovskite crystals, thereby suppressing the charge recombination in PSCs and promoting the charge extraction at TiO2/perovskite interface. Furthermore, the stability of PSCs is also significantly improved due to the reduced perovskite crystal defects and enhanced compactness of the C:C:CH3NH3PbI3 composite film. 

Research Article
Mechanism of calcium lignosulfonate in apatite and dolomite flotation system
Bo Feng, Liangzhu Zhang, Wenpu Zhang, Huihui Wang, and Zhiyong Gao
Available online 11 June 2021, https://doi.org/10.1007/s12613-021-2313-3
[Abstract](395) [PDF 571KB](20)

Since the physical and chemical properties of apatite and dolomite can be similar, the separation of these two minerals is difficult. Therefore, when performing this separation using the flotation method, it is necessary to search for selective depressants. An experimental research was performed on the separation behavior of apatite and dolomite using calcium lignosulfonate as a depressant, and the mechanism by which this occurs was analyzed. The results show that calcium lignosulfonate has a depressant effect on both apatite and dolomite, but the depressant effect on dolomite is stronger at the same dosage. Mechanism analysis shows that the adsorptive capacity of calcium lignosulfonate on dolomite is higher than that of apatite, which is due to the strong reaction between calcium lignosulfonate and the Ca sites on dolomite. In addition, there is a hydrogen bond between calcium lignosulfonate and dolomite, which further prevents the adsorption of sodium oleate to dolomite, thus greatly inhibiting the flotation of dolomite.

Research Article
Isothermal oxidation behavior of Nb-bearing austenitic cast steels at 950°C
Hailong Zhao, Longfei Li, and Qiang Feng
Available online 11 June 2021, https://doi.org/10.1007/s12613-021-2314-2
[Abstract](231) [PDF 1694KB](7)

The oxidation behaviors of three austenitic cast steels with different morphology of primary carbides at 950°C in air was investigated using SEM, EDS, XRD and FIB/TEM. It was found that their oxidation kinetics followed a logarithmic law and the oxidation rate could be significantly decreased as long as a continuous silica layer formed at the scale/substrate interface. When the local Si concentration was inadequate, the internal oxidation beneath the oxide scale occurred. The spallation of oxides during cooling could be inhibited with the formation of internal oxidation, owing to the reduced mismatch stress between the oxide scale and the substrate. The "Chinese-script" primary Nb(C,N) was superior to the dispersed primary Nb(C,N) in suppressing the oxidation penetration in the interdendritic region by supplying a high density of Cr quick-diffusion channels. In addition, the innermost and the outermost oxidation layers were both found to be enriched with Cr, while the Cr evaporation in the outermost layer was significant when the water-vapor concentration in the environment was high enough. These findings further the understanding regarding the oxidation behavior of austenitic cast steels and will promote the alloy development for exhaust components.

Research Article
Characterization and ultraviolet–visible shielding property of samariumcerium compounds containing Sm2O2S prepared by Co-precipitation method
Yanping Li, Xue Bian, Xun Jin, Peng Cen, Wenyuan Wu, and Gaofeng Fu
Available online 1 June 2021, https://doi.org/10.1007/s12613-021-2309-z
[Abstract](145) [PDF 1452KB](5)

Since ultraviolet (UV) light, as well as blue light, which was part of visible light, was harmful to skin, samarium-cerium compounds containing Sm2O2S were synthesized by co-precipitation method. This kind of compounds blocks not only UV light, but also blue light that is part of visible light. The minimum values of average transmittance (360–450 nm) and band gap of samarium-cerium compounds were 8.90% and 2.30 eV, respectively, which were less than 13.96% and 2.63 eV of CeO2. Elemental analysis (EA), X-ray diffraction (XRD), Fourier transformation infrared (FT-IR), and Raman spectra determined that the samples contained Ce4O7, Sm2O2S, Sm2O3, and Sm2O2SO4. The micro-structure of samples was analyzed by scanning and transmission electron microscopy (SEM, TEM). X-ray photoelectron spectrum (XPS) showed cerium had Ce3+ and Ce4+ valence states, and oxygen was divided into lattice oxygen and oxygen vacancy that was direct cause of the decrease of average transmittance and band gap.

Research Article
Effect of Al2O3 content on the viscosity and structure of CaO–SiO2–Cr2O3–Al2O3 slags
Fang Yuan, Zheng Zhao, Yanling Zhang, and Tuo Wu
Available online 18 May 2021, https://doi.org/10.1007/s12613-021-2306-2
[Abstract](199) [PDF 1282KB](18)

The effect of Al2O3 on the viscosity and structure of CaO–SiO2–Cr2O3–Al2O3 slags is investigated to facilitate recycling of Cr in steelmaking slags. The slags exhibit good Newtonian behavior at high temperature. The viscosity of acidic slag first increases from 0.825 to 1.141 Pa·s as the Al2O3 content increases from 0 to 10wt% and then decreases to 1.071 Pa·s as the Al2O3 content increases further to 15wt%. The viscosity of basic slag first increases from 0.084 to 0.158 Pa·s as the Al2O3 content increases from 0 to 15wt% and then decreases to 0.135 Pa·s as the Al2O3 content increases further to 20wt%. Furthermore, Cr2O3-containing slag requires less Al2O3 to reach the maximum viscosity than Cr2O3-free slag; the Al2O3 contents at which the behavior changes are 10wt% and 15wt% for acidic and basic slags, respectively. The activation energy of the slags is consistent with the viscosity results. Raman spectra demonstrate that [AlO4] tetrahedra appear initially and are replaced by [AlO6] octahedra with further addition of Al2O3. The dissolved organic phosphorus content of the slag first increases and then decreases with increasing Al2O3 content, which is consistent with the viscosity and Raman results.

Research Article
Significantly improved hydrogen storage behaviors of MgH2 with Nb nanocatalyst
Farai Michael Nyahuma, Liuting Zhang, Mengchen Song, Xiong Lu, Beibei Xiao, Jiaguang Zheng, and Fuying Wu
Available online 13 May 2021, https://doi.org/10.1007/s12613-021-2303-5
[Abstract](224) [PDF 1697KB](14)

The study explores the excellent modification effect of Nb nanocatalyst prepared via surfactant assisted ball milling technique (SABM) on the hydrogen storage properties of MgH2. Optimal catalyst doping concentration was determined by comparing onset decomposition temperature, released hydrogen capacity and reaction rate for different MgH2+ywt% Nb (y = 0, 3, 5, 7, 9) composites. The MgH2+5wt% Nb composite started releasing hydrogen at 186.7℃ and a total of 7.0wt% hydrogen was released in the dehydrogenation process. In addition, 5wt% Nb doped MgH2 also managed to release 4.2wt% H2 within 14 minutes at 250℃ and had the ability to absorb 4.0wt% hydrogen in 30 minutes at 100℃. Cycling tests revealed that MgH2+5wt% Nb could retain 6.3 wt% H2 capacity (89.2%) after 20 cycles. Dehydrogenation and hydrogenation activation energy values were decreased from 140.51±4.74 kJ·mol-1 and 70.67±2.07 kJ·mol-1 to 90.04±2.83 kJ·mol-1 and 53.46±3.33 kJ·mol-1 after doping MgH2 with Nb, respectively. Microstructure analysis proved that homogeneously distributed NbH acted as active catalytic unit for improving the hydrogen storage performance of MgH2. These results indicate SABM can be considered as an option to develop other nanocatalysts for energy related areas.

Research Article
The wetting behavior of CaO-Al2O3-based mold flux with various BaO and MgO contents on steel substrate
Lejun Zhou, Hao Luo, Wanlin Wang, Houfa Wu, Erzhuo Gao, You Zhou, and Daoyuan Huang
Available online 8 May 2021, https://doi.org/10.1007/s12613-021-2300-8
[Abstract](213) [PDF 747KB](20)

The interfacial phenomena in mold have great impact on the smooth operation and the quality of the casting product. In this paper, the wetting behavior of CaO-Al2O3-based mold flux with different BaO and MgO contents was studied. The results show that the contact angle between molten flux and IF steel substrate increased from 62.4o to 74.5o with the increase of BaO content from 3wt% to 7wt%, while it decreased from 62.4o to 51.3o with the increase of MgO content from 3wt% to 7wt%. The interfacial tension also increased from 1630.3 to 1740.8 mN/m when the BaO content increased, but it reduced from 1630.3 to 1539.7 mN/m with the addition of MgO. The changes of contact angle and interfacial tension were mainly due to the fact that the bridging oxygen (O0) at the interface was broken into non-bridging oxygen (O-) and free oxygen (O2-) by MgO. However, more O- and O2- connected into O0 when BaO was added, since the charge compensation effect of BaO was so stronger that it offset the effect of providing O2−.

Research Article
Pyrolysis behaviour and combustion kinetics of waste printed circuit boards
kang Yan, Chongwei Liu, Liping Liu, Min Xiong, Zhongtang Zhang, Shuiping Zhong, Zhifeng Xu, and Jindi Huang
Available online 30 April 2021, https://doi.org/10.1007/s12613-021-2299-x
[Abstract](151) [PDF 1158KB](7)

The effective recycling of waste printed circuit boards (WPCBs) can conserve resources and reduce environmental pollution. This study explores the pyrolysis and combustion characteristics of WPCBs in various atmospheres through thermogravimetric and Gaussian fitting analyses. Furthermore, this study analyses the pyrolysis products and combustion processes of WPCBs through thermogravimetric–Fourier transform infrared and thermogravimetric–mass spectrometry analytical techniques. Results show that the pyrolysis and combustion processes of WPCBs do not constitute a single reaction, but rather, they constitute an overlap of multiple reactions. The pyrolysis and combustion process of WPCBs is divided into multiple reactions by Gaussian peak fitting, and the kinetic parameters of each reaction are obtained by the Coats-Redfern method. In an argon atmosphere, pyrolysis consists of the overlap of the preliminary pyrolysis of epoxy resin, pyrolysis of small organic molecules, and pyrolysis of brominated flame retardants. The reaction mechanism functions are G(α)= (1-α)-1-1, G(α) = (1-α)-1-1 and G(α)= [-(1-α)]4 (α is the conversion rate of the reaction,  G(α) is the mechanism function of the reaction). The combustion of WPCB in oxygen consists of the overlap of the epoxy resin and brominated flame retardant combustion reactions; the reaction mechanism functions are G(α)= ((1-α)-1/3-1)2 and G(α)= ((1-α)-1/3-1)2. This study provided the theoretical basis for pollution control, process optimization and reactor design of WPCBs pyrolysis.

Research Article
Effect of particle micro-structure on the electrochemical properties of LiNi0.8Co0.1Mn0.1O2 cathode material
Ze-xun Tang, Hong-qi Ye, Xin Ma, and Kai Han
Available online 23 April 2021, https://doi.org/10.1007/s12613-021-2296-0
[Abstract](156) [PDF 1375KB](14)

Ni-rich layered material is a kind of high-capacity cathode to meet the requirement of electric vehicles. As for the typical LiNi0.8Co0.1Mn0.1O2 material, the particle formation is significant for electrochemical properties of the cathode. In this work, the structure, morphology and electrochemical performance of LiNi0.8Co0.1Mn0.1O2 secondary particles and single crystals are systematically studied. A lower Ni2+/Ni3+ ratio of 0.66 and a lower residual alkali content of 2280 ppm were achieved on the surface of single crystals. In addition, the single crystals showed a discharge capacity of 191.6 mAh/g at 0.2 C (~12 mAh/g lower than that of the secondary particles) and enhanced electrochemical stability, especially when cycled at 50 °C and in a wider electrochemical window (between 3.0 and 4.4 V vs. Li+/Li). The LiNi0.8Co0.1Mn0.1O2 secondary particles were suitable for applications requiring high specific capacity, whereas single crystals exhibited better stability, indicating that they are more suitable for use in long life requested devices.

Research Article
Simultaneously improving mechanical properties and corrosion resistance of as-cast AZ91 Mg alloy by ultrasonic surface rolling
Jing Han, Cong Wang, Yuan-ming Song, Zhi-yuan Liu, Jia-peng Sun, and Ji-yun Zhao
Available online 23 April 2021, https://doi.org/10.1007/s12613-021-2294-2
[Abstract](246) [PDF 1659KB](39)

Mg alloy casting parts commonly suffer from drawbacks of low surface properties, high susceptibility to corrosion, unsatisfactory absolute strength, and poor ductility, which seriously limit their wide application. Here, a surface nanocrystallization technique, i.e., ultrasonic surface rolling (USR), was applied on an as-cast AZ91 Mg alloy sheet to improve its corrosion resistance and mechanical properties. The USR produces double smooth surfaces with Ra=0.026 μm and gradient nanostructured surface layers on the sheet. Due to this special microstructure modification, the USR sheet exhibits 51% and 50% improvements in tensile yield strength and ultimate strength without visibly sacrificed ductility comparable to its untreated counterpart, as well as a 24% improvement in surface hardness. The USR sheet also shows good corrosion resistance in 3.5% NaCl aqueous solution. The corrosion current density of the USR sheet reduces by 63% after immersion for 1 h, and 25% after immersion for 24 h compared to that of the untreated counterpart. The enhanced strength and hardness are mainly related to the gradient nanostructure. The improved corrosion resistance is mainly ascribed to the decreased surface roughness, nanostructured surface, and residual compressive stress. The present results state that USR is an effective and attractive method to improve multiple properties of Mg alloy casting parts, and thus can be used as an additional and last working procedure to achieve high-performance Mg alloy casting parts.

Research Article
Quantitative micro-electrochemical study of duplex stainless steel 2205 in 3.5wt% NaCl solution
Shuang-yu Cai, Ke-ke Lu, Xin-nan Li, Lei Wen, Fei-fei Huang, and Ying Jin
Available online 20 April 2021, https://doi.org/10.1007/s12613-021-2291-5
[Abstract](274) [PDF 849KB](33)

Duplex stainless steels (DSSs) are suffering from various localized corrosion attacks such as pitting, selective dissolution, crevice corrosion during their service period. It is of great value to quantitatively analyze and grasp the micro-electrochemical corrosion behavior and related mechanism for DSSs on the micrometer or even smaller scales. In this work, scanning Kelvin probe force microscopy (SKPFM) and energy dispersive spectroscopy (EDS) measurements were performed to reveal the difference between the austenite phase and ferrite phase in microregion of DSS 2205. Then traditional electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) tests were employed for micro-electrochemical characterization of DSS 2205 with different proportion phases in Φ40 μm and Φ10 μm micro holes. Both of them can only be utilized for qualitative or semi-quantitative micro-electrochemical characterization of DSS 2205. Coulostatic perturbation method was employed for quantitative micro-electrochemical characterization of DSS 2205. What is more, the applicable conditions of coulostatic perturbation were analyzed in depth by establishing a detailed electrochemical interface circuit. A series of microregion coulostatic perturbations for DSS 2205 with different proportion phases in Φ10 μm micro holes showed that as the austenite proportion increases, the corresponding polarization resistance of microregion increases linearly.

Research Article
Recover titanium, aluminum, magnesium and separate silicon from titanium-bearing blast furnace slag by sulfuric acid curing-leaching
Long Wang, Liang Chen, Wei-zao Liu, Guo-quan Zhang, Sheng-wei Tang, Hai-rong Yue, Bin Liang, and Dong-mei Luo
Available online 20 April 2021, https://doi.org/10.1007/s12613-021-2293-3
[Abstract](189) [PDF 1339KB](15)

An energy-efficient route was adopted to treat titanium-bearing blast furnace slag (TBBFS) in this study. Titanium, aluminum and magnesium were simultaneously extracted and silicon was separated by sulfuric acid curing in low temperature and low concentration sulfuric acid leaching. The process parameters of sulfuric acid curing TBBFS were systematically studied. Under the optimal conditions, the recovery of titanium, aluminum and magnesium reached 85.96%, 81.17% and 93.82%, respectively. The rapid leaching model was used to limit the dissolution and polymerization of silicon, and the dissolution of silicon was only 3.18%. The mechanism of sulfuric acid curing-leaching was investigated. During the curing process, the reaction occurred rapidly and released heat massively. Under the attack of hydrogen ions, the structure of TBBFS was destroyed, silicate was depolymerized to form filterable silica, and titanium, magnesium, aluminum, and calcium ions were replaced to form sulfates and enriched on the surface of silica particles. Titanium, aluminum, and magnesium were recovered in the leaching solution, and calcium sulfate and silica were enriched in the residue after leaching. This method could effectively avoid the formation of silica sol during the leaching process and accelerate the solid-liquid separation.

Research Article
Influence of process parameters and aging treatment on the microstructure and mechanical properties of AlSi8Mg3 alloy fabricated by selective laser melting
Yao-xiang Geng, Hao Tang, Jun-hua Xu, Yu Hou, Yu-xin Wang, Zhen He, Zhi-jie Zhang, Hong-bo Ju, and Li-hua Yu
Available online 31 March 2021, https://doi.org/10.1007/s12613-021-2287-1
[Abstract](155) [PDF 1808KB](8)
Many studies have investigated the selective laser melting (SLM) of AlSi10Mg and AlSi7Mg alloys, but there is still a lack of researches focused on Al-Si-Mg alloys specifically tailored for SLM. In this work, a novel high Mg-content AlSi8Mg3 alloy was specifically designed for SLM. The results showed that this new alloy exhibited excellent SLM processability with the lowest porosity of 0.07%. Massive lattice distortion led to a high Vickers hardness in samples fabricated at a high laser scanning speed due to the precipitation of Mg2Si nanoparticles from the α-Al matrix induced by high-intensity intrinsic heat treatment during SLM. The maximum microhardness and compressive yield strength of the alloy reached 211±4 HV and 526±12 MPa, respectively. After aging treatment at 150 ℃, the maximum microhardness and compressive yield strength of the samples were further improved to 221±4 HV and 577±5 MPa, respectively. These values are higher than those of most known aluminum alloys fabricated by SLM. This paper provides a new idea for optimizing the mechanical properties of Al-Si-Mg alloys fabricated using SLM.
Research Article
Flotation kinetics performance of different coal size fractions with nanobubbles
Hua Han, An Liu, Cai-li Wang, Run-quan Yang, Shuai Li, and Huai-fa Wang
Available online 6 March 2021, https://doi.org/10.1007/s12613-021-2280-8
[Abstract](368) [PDF 957KB](29)
The flotation kinetics of different size fractions of conventional and nanobubbles (NBs) flotation were compared to investigate the effect of NBs on flotation performance of various coal particle size. Six flotation kinetics models were selected to fit the flotation data and NBs were observed on the hydrophobic surface under hydrodynamic cavitation by atomic force microscope (AFM) scanning. The flotation results indicate that the best flotation performance of size fraction at -0.125+0.074 mm can be obtained either in conventional or NBs flotation, NBs increase the combustible recovery of almost all of the size fractions, but increase the product ash content of -0.25-0.074 mm and reduce the product ash content of -0.045 mm at the same time. The first-order models can both be used to fit the flotation data in conventional and NBs flotation, the classical first-order model is the most suitable one. NBs have an obvious enhancement of flotation rate on coarse size fraction (-0.5+0.25 mm) but decrease the flotation rate of the medium size (-0.25+0.074 mm), the improvement of flotation speed on fine coal particles (-0.074 mm) is probably the reason of the better flotation performance of raw sample flotation.
Research Article
Surface nanobubbles on hydrophobic surface and its implication to flotation
Chen-wei Li, Dan-long Li, Xin Li, Ming Xu, and Hai-jun Zhang
Available online 5 March 2021, https://doi.org/10.1007/s12613-021-2279-1
[Abstract](417) [PDF 1804KB](41)
Nanobubbles play a potential role in the application of fine particles flotation. In this work, the identification of nanoentities was identified with contact mode atomic force microscope (AFM). Meanwhile, the influence of setpoint ratio and amplitude of cantilever and the responses of the formed surface nanobubbles to the fluctuations of pH, salt concentrations, and surfactant concentrations in the slurry, were studied respectively. Nanobubbles were found on highly oriented pyrolytic graphite (HOPG) surface as HOPG was immersed in deionized water in the ambient temperature. The coalescence of nanobubbles occurred under contact mode, which provides strong evidence supporting the gaseous nature of these nanostructures on HOPG. The measuring height of surface nanobubbles decreased with the setpoint ratio (Asetpoint/Afree). The change in concentrations of pH and MIBC shows a negligible influence on lateral size and height of the preexisting surface nanobubbles. The addition of LiCl results in a negligible change in lateral size but an obvious change in height of surface nanobubbles. The present results are expected to provide a valuable reference to understand the properties of surface nanobubbles and design nanobubbles-assisted flotation processes.
Research Article
Hot compressive deformation of eutectic Al-17at% Cu alloy on the interface of the Cu-Al composite plate produced by horizontal continuous casting
Jun Wang, Fan Zhao, Guo-liang Xie, Jia-xuan Xu, and Xin-hua Liu
Available online 3 March 2021, https://doi.org/10.1007/s12613-021-2276-4
[Abstract](225) [PDF 2138KB](15)
On the interface of the Cu-Al composite plate from horizontal continuous casting, the eutectic tissue layer thickness accounts for more than 90% of the total interface thickness, and the deformation in rolling forming plays an important role in the quality of the composite plate. The eutectic tissue material on the interface of the Cu-Al composite plate was prepared by changing the cooling rate of ingot solidification and the deformation in hot compression was investigated. The results show that deformation temperature is over 300 ℃, the softening effect of dynamic recrystallization of α-Al is greater than the hardening effect, and uniform plastic deformation of eutectic tissue is caused. The constitutive equation of flow stress in the eutectic tissue layer was established by Arrhenius hyperbolic-sine mathematics model, providing a reliable theoretical basis for the deformation of the Cu-Al composite plate.
Research Article
Effect of an external magnetic field on improved electroslag remelting cladding process
Zhi-wen Hou, Yan-wu Dong, Zhou-hua Jiang, Zhi-hao Hu, Li-meng Liu, and Kun-jie Tian
Available online 3 March 2021, https://doi.org/10.1007/s12613-021-2277-3
[Abstract](227) [PDF 1357KB](9)
Obtaining a uniform interface temperature field plays a crucial role in the interface bonding quality of bimetal compound rolls. Therefore, in this study, an improved electroslag remelting cladding (ESRC) process using external magnetic field is proposed to improve the uniformity of the interface temperature of compound rolls. The improved ESRC comprises a conventional ESRC circuit and an external coil circuit. A comprehensive 3D model, including multi-physics fields is solved to study the effect of external magnetic field on the multi-physics fields and interface temperature uniformity. The simulated results demonstrate that the non-uniform Joule heat and flow fields cause a non-uniform interface temperature in the conventional ESRC. As for the improved ESRC, the magnetic flux density (Bcoil) along the z-axis is produced by an anticlockwise current of the external coil. The rotating Lorentz force is generated from the interaction between the radial current and axial Bcoil. Therefore, the slag pool flows clockwise, which enhances circumferential effective thermal conductivity. As a result, the uniformity of the temperature field and interface temperature improve. In addition, the magnetic flux density and rotational speed of the simulated results are in good agreement with those of the experimental results, which verifies the accuracy of the improved ESRC model. Therefore, an improved ESRC is efficient for industrial production of the compound roll with a uniform interface bonding quality.
Research Article
Role of trace additions of Ca and Sn in improving the corrosion resistance of Mg-3Al-1Zn alloy
Pan-pan Wang, Hai-tao Jiang, Yu-jiao Wang, Yun Zhang, Shi-wei Tian, Ye-fei Zhang, and Zhi-ming Cao
Available online 18 February 2021, https://doi.org/10.1007/s12613-021-2268-4
[Abstract](281) [PDF 1276KB](11)
The limited wide applicability of commercial Mg alloys is mainly attributed to the poor corrosion resistance. Addition of alloying elements is the simplest and effective method to improve the corrosion properties. Based on the low-cost alloy composition design, the corrosion behavior of commercial Mg-3Al-Zn (AZ31) alloy bearing minor Ca or Sn element was characterized by scanning Kelvin probe force microscopy, hydrogen evolution, electrochemical measurements and corrosion morphology analysis. Results revealed that the potential difference of Al2Ca/α-Mg and Mg2Sn/α-Mg was ∼230±19 mV and ∼80±6 mV, much lower than that of Al8Mn5/α-Mg (∼430±31 mV) in AZ31 alloy, which illustrated that AZ31-0.2Sn alloy performed the best corrosion resistance, followed by AZ31-0.2Ca, while AZ31 alloy exihited the worst corrosion resistance. Moreover, Sn dissolved into matrix obviously increased the potential of α-Mg and participated in the formation of dense SnO2 film at the interface of matrix, while Ca element was enriched in the corrosion product layer, resulting in the corrosion product layer of AZ31-0.2Ca/Sn alloys more compact, stable and protective than AZ31 alloy. Therefore, AZ31 alloy bearing 0.2wt% Ca or Sn element exhibited excellent balanced properties, which is potential to be applied in commercial more comprehensively.
Research Article
Novel confinement combustion method to nanosized WC/C for efficient electrocatalytic oxygen reduction
Peng-qi Chen, Huan Wu, Yun-xiao Tai, Yu-fei Gao, Jia-yu Chen, and Ji-gui Cheng
Available online 4 February 2021, https://doi.org/10.1007/s12613-021-2265-7
[Abstract](375) [PDF 993KB](18)
Nanosized WC/C catalyst was synthesized via a novel ultra-rapid confinement combustion synthesis method. Result showed that the amount of activated carbon (AC) played an important role in the morphology and structure controlling of both the precursor and the final powder. Due to the confinement of the pore structure and large specific surface area of AC, the WC particles synthesized inside the pores of AC had the size of 10-20 nm. When applied to oxygen reduction performance, the half-wave potential was -0.24 V and the electron transfer number was 3.45, which meant that the main reaction process is the transfer of four electrons. The detailed electrocatalytic performance and the underlying mechanism were investigated in this work. Our study provides a novel approach for the design of new composition and structure catalysts which has a certain significance for promoting the commercialization of fuel cells.
Research Article
Effects of Nd on microstructure and mechanical properties of as-cast Mg-12Gd-2Zn-xNd-0.4Zr alloys with stacking faults
Li-xin Hong, Rong-xiang Wang, and Xiao-bo Zhang
Available online 2 February 2021, https://doi.org/10.1007/s12613-021-2264-8
[Abstract](339) [PDF 1451KB](6)
In order to study the effects of Nd addition on microstructure and mechanical properties of Mg-Gd-Zn-Zr alloys, the microstructure and mechanical properties of the as-cast Mg-12Gd-2Zn-xNd-0.4Zr (x = 0, 0.5, and 1 wt%) alloys were investigated by using optical microscope, scanning electron microscope, X-ray diffractometer, nano indentation tester, microhardness tester, and tensile testing machine. The results show that the microstructures mainly consist of α-Mg matrix, eutectic phase and stacking faults. The addition of Nd plays a significant role in grain refinement and uniform microstructure. The tensile yield strength and microhardness increase but the compression yield strength decreases with increasing Nd addition, leading to weakening tension-compression yield asymmetry in reverse of the Mg-12Gd-2Zn-xNd-0.4Zr alloys. The highest ultimate tensile strength (194 MPa) and ultimate compression strength (397 MPa) are obtained with 1 wt% Nd addition of the alloy.
Research Article
Blast furnace ironmaking process with super high TiO2 in the slag: Density and surface tension of the slag
Zheng-de Pang, Yu-yang Jiang, Jia-wei Ling, Xue-wei Lv, and Zhi-ming Yan
Available online 2 February 2021, https://doi.org/10.1007/s12613-021-2262-x
[Abstract](333) [PDF 886KB](30)
Considering high novelty and potential on ultra–high (>80%) or full V–Ti–Magnetite ore under blast furnace smelting, we are conducting a series of works on physics character of high TiO2 bearing blast furnace slag (BFS) for slag optimization. This work discussed the density and surface tension of high TiO2 bearing BFS using the Archimedean principle and the maximum bubble pressure method, respectively. The influence of TiO2 content and MgO/CaO (mass ratio) on the density and surface tension of CaO–SiO2–TiO2–MgO–Al2O3 slags were investigated. Results indicated that the density of slags decreased as increasing TiO2 content from 20 to 30 wt%, but it increased slightly as increasing MgO/CaO from 0.32 to 0.73. In view of silicate network structure, the density and the degree of polymerization (DOP) of network structure have a consistent trend. The addition of TiO2 reduces (Q3)2/(Q2) ratio, decreases DOP, which leads to the decrease of slag density. The surface tension of CaO–SiO2–TiO2–MgO–Al2O3 slags decreased dramatically as increasing TiO2 content from 20 to 30 wt%. Conversely, it increased as increasing MgO/CaO from 0.32 to 0.73. Furthermore, the iso–surface tension lines were obtained under 1723K using the Tanaka developed model in view of Butler formula. It may be useful for slag optimization of ultra–high proportion (>80%) or even full V–Ti–Magnetite ore under BF smelting.
Research Article
Experimental investigation on the intermetallic growth behavior during post deformation annealing in multilayer Ti/Al/Nb composite interfaces
Roya Jafari and Beitallah Eghbali
Available online 2 February 2021, https://doi.org/10.1007/s12613-021-2263-9
[Abstract](349) [PDF 1498KB](3)
In the present research, the tri-metal Ti-Al-Nb composites were processed through three procedures: hot pressing, rolling, and hot pressing, followed by subsequent rolling. The fabricated composites were then subjected to annealing at 600, 625, and 650 ºC temperatures at different times. Microstructure observation at the interfaces reveals that the increase in plastic deformation strain significantly affects TiAl3 intermetallic layers’ evolution and accelerates the layers’ growth. On the contrary, the amount of applied strain does not significantly affect the evolution of the NbAl3 intermetallic layer thickness. It was also found that Al and Ti atoms’ diffusion has occurred throughout the TiAl3 layer, but only Al atoms diffuse through the NbAl3 layer. The slow growth rate of the NbAl3 intermetallic layer is due to the lack of diffusion of Nb atoms and the high activation energy of Al atoms’ reaction with Nb atoms.
Invited Review
A review of the synthesis and application of zeolites from coal-based solid wastes
Xiao-yu Zhang, Chun-quan Li, Shui-lin Zheng, Yong-hao Di, and Zhi-ming Sun
Available online 22 January 2021, https://doi.org/10.1007/s12613-021-2256-8
[Abstract](482) [PDF 870KB](20)
Zeolite derived from coal-based solid wastes (coal gangue and coal fly ash) not only can cope with the environmental problems caused by coal-based solid wastes but also achieve their valuable utilization. In this paper, the physicochemical properties of coal gangue and coal fly ash were introduced. Then the mechanism and application characteristics of the pretreatment processes for zeolite synthesis from coal-based solid wastes were introduced as well. After that, the synthesis processes of coal-based solid waste zeolite and their merits and demerits were summarized in detail. Furthermore, the application characteristics of various coal-based solid waste zeolites and their common application fields were also illustrated. By the end of this review, we propose that alkaline fusion-assisted supercritical hydrothermal crystallization may be an efficient method for synthesizing coal-based solid waste zeolites. Besides, more attention should be paid to the recycling of alkaline waste liquid and the application of coal-based solid waste zeolites in the field of volatile organic compounds adsorption removal.
Research Article
Analysis of local microstructure and strengthening mechanisms in adjustable-gap bobbin tool friction stir welds of Al-Mg
Dong Wu, Wen-ya Li, Qiang Chu, Yang-fan Zou, Xi-chang Liu, and Yan-jun Gao
Available online 22 January 2021, https://doi.org/10.1007/s12613-021-2254-x
[Abstract](371) [PDF 1218KB](11)
The bobbin tool friction stir welding process was used to join 6 mm thick 5A06 aluminum alloy plates. Optical microscope was used to characterize the microstructure. The electron backscatter diffraction (EBSD) identified the effect of non-homogeneous microstructure on the tensile properties. It was observed that the grain size in the top of the stir zone (SZ) is smaller than that in the centre region. The lowest ratio of recrystallization and density of the geometrically-necessary dislocations (GNDs) in the SZ was found in the middle near the thermo-mechanically affected zone (TMAZ) being 22% and 1.15×10-13 m-2, respectively. The texture strength of the heat-affected zone (HAZ) is the largest, followed by that in the SZ, with the lowest being in the TMAZ. There were additional interfaces developed which contributed to the strengthening mechanism, and their effect on tensile strength was analysed. The tensile tests identified the weakest part in the joint at the interfaces, and the specific reduction value is about 93MPa.
Research Article
Effects of heat treatments on microstructures of TiAl alloys
Wen Yu, Jian-xin Zhou, Ya-jun Yin, Zhi-xin Tu, Xin Feng, Hai Nan, Jun-pin Lin, and Xian-fei Ding
Available online 16 January 2021, https://doi.org/10.1007/s12613-021-2252-z
[Abstract](471) [PDF 1841KB](21)
This study aims to investigate the effects of heat treatments on microstructures of γ-TiAl alloys. Two Ti-47Al-2Cr-2Nb alloy ingots were manufactured by casting method and then heat treated in two types of heat treatments. Their microstructures were studied by both optical and scanning electron microscopies. The chemical compositions of two ingots were determined. The ingot with lower Al content only obtains lamellar structures while the one higher in Al content obtains nearly lamellar and duplex structures after heat treatment within 1270°C to 1185°C. A small amount of B2 phase is found to be precipitated in both as-cast and heat-treated microstructures. They are distributed at grain boundaries when holding at a higher temperature, such as 1260°C. However, B2 phase is precipitated at grain boundaries and in colony interiors simultaneously after heat treatments happened at 1185°C. Furthermore, the effects of heat treatments on grain refinement and other microstructural parameters are discussed.
Research Article
Combining the 8-hydroxyquinoline intercalated layered double hydroxide film and sol-gel coating for active corrosion protection of the magnesium alloy
Yahya Jafari Tarzanagh, Davod Seifzadeh, and Roghaye Samadianfard
Available online 16 January 2021, https://doi.org/10.1007/s12613-021-2251-0
[Abstract](445) [PDF 1853KB](13)
The 8-Hydroxyquinoline (8-HQ) intercalated Layered Double Hydroxides (LDH) film as underlayer and sol-gel layer was combined for active corrosion protection of the AM60B magnesium alloy. The LDH, LDH/sol-gel, and LDH@HQ/sol-gel coatings were analyzed using the SEM, FESEM, EDX, XRD, AFM, and EIS methods. The SEM images showed that the surface was entirely coated by the LDH film composed of vertically-grown nanosheets. The same morphology was observed for the LDH/sol-gel and LDH@HQ/sol-gel coatings. Also, almost the same topography was observed for both composite coatings except that the LDH@HQ/sol-gel coating had relatively higher surface roughness. Although the LDH film had the same impedance behavior as the alloy sample in 3.5 wt. % NaCl solution, its corrosion resistance was much higher, which could be due to its barrier properties as well as to the trapping of the chloride ions. Similar to the LDH film, the corrosion resistance of the LDH/sol-gel composite diminished with increasing the exposure time. However, its values were much higher than that of the LDH film, which was mainly related to the sealing of the solution pathways. The LDH@HQ/sol-gel composite showed much better anti-corrosion properties than the LDH/sol-gel coating due to the adsorption of the 8-HQ on the damaged areas through the complexation.
Research Article
Evolution laws of microstructures and mechanical properties during heat treatments for near-α high temperature titanium alloys
Xiao-zhao Ma, Zhi-lei Xiang, Tao Li, Yi-lan Chen, Ying-ying Liu, Zi-yong Chen, and Qun Shu
Available online 6 January 2021, https://doi.org/10.1007/s12613-021-2248-8
[Abstract](373) [PDF 1799KB](6)
Evolution laws of microstructures, mechanical properties and fractographs after different solution temperatures were investigated through various analyses methods. With the increasing solution temperatures, contents of primary α phase decreased, and contents of transformed β structures increased. Lamellar α grains dominated the characteristics of transformed β structures, and widths of secondary α lamellas increased monotonously. For as-forged alloy, large silicides with equiaxed and rod-like morphologies, and nano-scale silicides were found. Silicides with large sizes might be (Ti, Zr, Nb)5Si3 and (Ti, Zr, Nb)6Si3. Rod-like silicides with small sizes precipitated in retained β phase, exhibiting near 45° angles with α/β grain boundaries. Retained β phases in as-heat treated alloys were incontinuous. 980STA exhibited excellent combinations of room temperature (RT) and 650℃ mechanical properties. Characteristics of fracture surfaces largely depended on the evolutions of microstructures. Meanwhile, silicides promoted the formation of mico-voids.
Research Article
Mechanical properties of Al-15Mg2Si composites prepared under different solidification cooling rates
Elahe Safary, Reza Taghiabadi, and Mohammad Hosein Ghoncheh
Available online 29 December 2020, https://doi.org/10.1007/s12613-020-2244-4
[Abstract](482) [PDF 1571KB](18)
The effect of different cooling rates (2.7, 5.5, 17.1, and 57.5 °C/s) on the solidification parameters, microstructure, and mechanical properties of Al-15Mg2Si composites was studied. The results showed that, high cooling rate refined the Mg2Si particles and changed their morphology to the more compacted forms with less microcracking tendency The average radius and fraction of primary Mg2Si particles decreased from 20 µm and 13.5% to about 10 µm and 7.3%, respectively, as the cooling rate increased from 2.7 °C/s to 57.5 °C/s. Increasing the cooling rate also improved the distribution of microconstituents, decreased the size of grains, and reduced the volume fraction of micropores. The mechanical properties results revealed that augmenting the cooling rate from 2.7 °C/s to about 57.5 °C/s increased the hardness and quality index by 25% and 245%, respectively. High cooling rate also changed the fracture mechanism from brittle dominated to a high-energy ductile mode comprising of extensive dimpled zones.
Research Article
Reciprocating sliding wear properties of sintered Al-B4C composites
Mahmut Can ŞENEL, Yusuf Kanca, and Mevlüt Gürbüz
Available online 29 December 2020, https://doi.org/10.1007/s12613-020-2243-5
[Abstract](459) [PDF 1698KB](24)
Pure aluminum and boron carbide reinforced aluminum matrix composites with various content (1, 6, 15, 30 wt.%B4C) were fabricated using the powder metallurgy technique. The influence of boron carbide amount on the mechanical and tribological behavior of sintered Al-B4C was examined. The highest density (~2.54 g/cm3), lowest porosity (4%), maximum Vickers hardness (~75 HV), as well as, lowest weight loss (0.4 mg), and lowest specific wear rate (0.00042 mm3/Nm) under a 7 N load were obtained with Al-30B4C composites. Enhancement of 167% in hardness, a decrease of 75.8% in weight loss, and a decrease of 76.7% in specific wear rate under an applied load of 7 N were determined when compared with pure aluminum. Similarly, the SEM images of the worn surface revealed that the narrowest wear grove (0.85 mm) at a load of 7 N was detected at Al-B4C composite and the main wear mechanism was observed as an abrasive wear mechanism. According to the friction analysis, the coefficient of friction between surfaces increased with increasing boron carbide content and decreasing the applied load. In conclusion, boron carbide is an effective reinforcement material in terms of tribological and mechanical performance of Al-B4C composites.
Research Article
Microstructure and mechanical properties of friction pull plug welding for 2219-T87 aluminum alloy with the tungsten inert gas weld
Zhen Shao, Lei Cui, Li-jun Yang, Peng Lu, Hui-miao Wang, Zhuan-ping Sun, and Jian-ling Song
Available online 11 November 2020, https://doi.org/10.1007/s12613-020-2222-x
[Abstract](586) [PDF 1595KB](8)
Friction pull plug welding (FPPW) of 2219-T87 Tungsten Inert Gas (TIG) welded joint was studied. The microstructures, precipitate evolution, mechanical properties, and fracture morphologies of the joint were analyzed and discussed. Defect-free joints were obtained by using 7,000 r/min rotational speed, 12 mm axial feeding displacement and 20–22 kN axial force. It was found that, within the welding parameters as mentioned above, metallurgical bonding between the plug and plate can be achieved by the formation of recrystallized grains. According to the different microstructural features, the FPPW joint can be divided into different regions, including such as heat-affected zone (HAZ), thermo-mechanically affected zone (TMAZ), recrystallization zone, heat-affected zone in TIG weld (TIG-HAZ), and thermo-mechanically affected zone in TIG weld (TIG-TMAZ). In TIG-TMAZ, the grains were highly deformed and elongated owing to the shear and extrusion form the plug during FPPW process. The hardness distribution showed that TIG-TMAZ was the area with the lowest strength. The main reason of softening in TMAZ was identified as the dissolution of θ' and the coarsening of θ precipitate particles. In tensile test, the FPPW joint welded with 22 kN axial force showed the highest ultimate tensile strength of 237 MPa. The location of crack and facture was found in TIG-TMAZ. The fracture morphology of the tensile sample showed good plasticity and toughness.
Research Article
Wear behavior of the Zn-38Al-3.5Cu-1.2Mg/SiCp composite with different stabilization treatments
Sheng Liu, Qing Yuan, Yu-tong Sima, Chen-xi Liu, Fang Han, and Wen-wei Qiao
Available online 4 November 2020, https://doi.org/10.1007/s12613-020-2217-7
[Abstract](621) [PDF 2041KB](6)
Zn-38Al-3.5Cu-1.2Mg composite reinforced by nano SiCp was fabricated by stirring assisted ultrasonic vibration. In order to improve the abrasive resistance of the Zn-38Al-3.5Cu-1.2Mg/SiCp composite, several stabilization treatments with distinct solid solutions and aging temperatures were designed. The results indicate that the optimal stabilization treatment for the 38Al-3.5Cu-1.2Mg/SiCp composite involves a solution treatment at 380 °C for 6 h and aging at 170 °C for 48 h. The stabilization treatment leads to the formation of dispersive and homogeneous nano SiCp. During the friction wear condition, the nano SiCp limits the microstructure evolution from the hard α(Al, Zn) phase to the soft β(Al, Zn) phase. Besides, the increased amount of nano SiCp improves the grain dimension and contributes to abrasive resistance. Furthermore, the initiation and propagation of crack produced in the friction wear process are suppressed by the stabilization treatment, thereby improving the abrasive resistance of the Zn-38Al-3.5Cu-1.2Mg/SiCp composite.
Research Article
Phase evolution and properties of glass ceramic foams prepared by bottom ash, fly ash and pickling sludge
Jun-jie Zhang, Xiao-yan Zhang, Bo Liu, Christian Ekberg, Shi-zhen Zhao, and Shen-gen Zhang
Available online 4 November 2020, https://doi.org/10.1007/s12613-020-2219-5
[Abstract](711) [PDF 1348KB](13)
Municipal solid waste incineration bottom ash (BA), fly ash (FA) and pickling sludge (PS), causing severe environmental pollution, were transformed into glass ceramic foams with the aid of CaCO3 as the pore-foaming agent by sintering in this paper. The effect of BA/FA ratio on the phase composition, pore morphology, pore size distribution, physical properties, glass structure unit of the samples was investigated, with results showing that with the increase of BA/FA ratio, the content of glass phase, Si-O-Si and Q3Si units decrease gradually. The glass transmission temperature of the mixture has also been reduced. These leads to the decrease of the glass viscosity, further causing bubble coalescence and uneven pore distribution. Glass ceramic foams with uniform spherical pores (average pore size of 106 μm) would be fabricated, when the content of BA, FA and PS were 35wt%, 45wt% and 20wt% respectively, contributing to the glass ceramic foams of high performance with bulk density of 1.76 g/cm3, porosity of 56.01% and compressive strength exceeding 16.23 MPa. This versatile and low-cost approach brings new insight of synergistically recycling solid wastes.
Research Article
Enhanced detection of ppb-level NO2 by uniform Pt-doped ZnSnO3 nanocubes
Yao-yu Yin, Yan-bai Shen, Si-kai Zhao, Ang Li, Rui Lu, Cong Han, Bao-yu Cui, and De-zhou Wei
Available online 21 October 2020, https://doi.org/10.1007/s12613-020-2215-9
[Abstract](872) [PDF 913KB](20)
ZnSnO3 nanocubes (ZSNCs) with various Pt concentrations (1at%, 2at%, and 5at%) were synthesized by the high-yield and facile one-pot hydrothermal method. The microstructures of the obtained products were characterized by XRD, FESEM, TEM, EDS and XPS. The results showed that the ZSNCs with perovskite structure are approximately 600 nm in side length, and this size was reduced to 400 nm after Pt doping. PtOx (PtO and PtO2) nanoparticle with the diameter of about 5 nm were uniformly coated on the surface of ZSNCs. NO2 sensing properties showed that 1% Pt-ZSNCs exhibited the highest response to NO2 than pure ZSNCs and Pt-ZSNCs with other Pt concentrations. The maximum response of 1 at% Pt-ZSNCs to 500 ppb NO2 was 16.0 at the optimal operating temperature of 125 °C, which was over 11 times higher than that of pure ZSNCs. The enhanced NO2 sensing mechanisms of Pt-ZSNCs were discussed in consideration of catalytic activities and chemical sensitization of Pt doping.
Research Article
Numerical simulation of flash reduction process in a drop tube reactor with variable temperature
Yi-ru Yang, Qi-peng Bao, Lei Guo, Zhe Wang, and Zhan-cheng Guo
Available online 20 October 2020, https://doi.org/10.1007/s12613-020-2210-1
[Abstract](841) [PDF 926KB](45)
A computational fluid dynamics (CFD) model was developed to accurately predicate the flash reduction process, which is considered to be an efficient alternative ironmaking process. Laboratory-scale experiments were conducted in drop tube reactors (DTRs) to verify the accuracy of the CFD model. The reduction degree of ore particles was selected as a critical indicator of model prediction, and the simulated and experimental results were in good agreement. The influencing factors, including the particle size (20–110 μm), peak temperature (1250–1550 °C), and reductive atmosphere (H2/CO), were also investigated. The height variation lines indicated that smaller particles (50 μm) had a longer residence time (3.6 s). CO provided a longer residence time (~1.29 s) compared with H2 (~1.09 s). However, both the experimental and analytical results show that the reduction degree of particles in CO atmosphere only reached 60%, significantly lower than that in H2 atmosphere, even at the highest temperature (1550 °C). The optimum experimental particle size and peak temperature for the preparation of high-quality reduced iron were found to be 50 μm and 1350 °C in H2 atmosphere and 40 μm and 1550 °C in CO atmosphere, respectively.
Research Article
Two refractory high-entropy alloys CrHfNbTaTi and CrHfMoTaTi: Phase, microstructure and compressive properties
Jiao-jiao Yi, Fu-yang Cao, Ming-qin Xu, Lin Yang, Lu Wang, and Long Zeng
Available online 20 October 2020, https://doi.org/10.1007/s12613-020-2214-x
[Abstract](919) [PDF 689KB](38)
Two new refractory high-entropy alloys, CrHfNbTaTi and CrHfMoTaTi, deriving from the well-known HfNbTaTiZr alloy by principal element substitutions, were prepared by vacuum arc-melting. Their phase components, microstructures, and compressive properties in the as-cast state were investigated intensively. The results showed that both alloys are mainly composed of a BCC and cubic laves phase. In terms of the mechanical properties, the yield strength increased remarkably from 926 MPa of HfNbTaTiZr to 1258 MPa of CrHfNbTaTi, meanwhile a promising ductility of around 24.3 % elongation was retained. The morphology and composition of the network-shape interdendritic regions were closely related to the improvement in mechanical properties deduced by elemental substitution. Whereas, dendritic surrounded by the incompact interdendritic shell at the case of the incorporation of Mo deteriorates the yield strength, and results in a typical brittle feature.
Research Article
Enhanced microstructural and mechanical properties of Stellite/WC nanocomposite on Inconel 718 deposited through vibration-assisted laser cladding
Hossein Hosseini-Tayeb and Seyed Mahdi Rafiaei
Available online 20 October 2020, https://doi.org/10.1007/s12613-020-2211-0
[Abstract](919) [PDF 1803KB](12)
Stellite-21/WC nanopowders were deposited on Inconel using vibration-assisted laser cladding through different laser parameters. To study about the microstructural and mechanical behaviors, optical and scanning electron microscopes, hardness measurements, and wear characterizations were employed. The results showed that the variation of cooling rate resulted in remarkable effects on the microstructure of the as-cladded composites. Moreover, increasing the laser power from 150 W to 250 W increased the heat input and the dilutions. Also, in the higher power of the laser (i.e. 250 W), dilution was affected by two factors that were scanning rate and powder feeding rate. Through the addition of WC nanoparticles as the reinforcement, the dilution magnitude intensified while the hardness value surprisingly increased from 350 to 700 HV. The wear characterizations indicated that the composites containing 3 wt% WC nanoparticles possessed the highest wear resistance.
Research Article
Effects of mechanical vibration on physical, metallurgical and mechanical properties of cast-A308 (LM21) aluminum alloy
Siddharth Yadav, S.P. Tewari, J.K. Singh, and S.C. Ram
Available online 14 October 2020, https://doi.org/10.1007/s12613-020-2209-7
[Abstract](917) [PDF 1556KB](27)
The present investigation deals with the improvement in microstructure, physical, and mechanical properties of die-cast A308 alloy subjected to mechanical vibration during solidification. The different frequencies (0, 20, 30, 40, and 50 Hz) at constant amplitude (31 μm) were employed using a power amplifier as the power input device. X-ray diffractometer, optical microscopy, and scanning electron microscopy were used to examine the morphological changes in the cast samples under stationary and vibratory conditions. Metallurgical features of castings were evaluated by ImageJ analysis software. The average values of metallurgical features, i.e., primary α-Al grain size, dendrite arm spacing (DAS), avg. area of eutectic silicon, aspect ratio, and percentage porosity were reduced by 34, 59, 56, 22, and 62% respectively at 30 Hz frequency compared to stationary casting. The mechanical tests of cast samples showed that yield strength, ultimate tensile strength, elongation, and microhardness were increased by 8, 13, 17, and 16%, respectively, at 30 Hz frequency compared to stationary casting. The fractured surface of tensile specimens exhibited mixed-mode fracture behavior due to the appearance of brittle facets, cleavage facets, ductile tearing, and dimple morphologies. The presence of small dimples showed some plastic deformation occurred before fracture.
Research Article
Influence of polymer solution on the morphology and local structure of NH4ZnPO4 powders synthesized by a simple precipitation method at room temperature
Santi Phumying, Thongsuk Sichumsaeng, Pinit Kidkhunthod, Narong Chanlek, Jessada Khajonrit, Somchai Sonsupap, and Santi Maensiri
Available online 13 October 2020, https://doi.org/10.1007/s12613-020-2208-8
[Abstract](849) [PDF 1416KB](21)
In this work, NH4ZnPO4 powders were synthesized by a simple precipitation method at room temperature. The effect of PVP, PVA, sucrose and CTAB solution on the morphology and structure of the prepared samples was investigated. The phase composition and morphology of the prepared samples were characterized by using X-ray diffraction and scanning electron microscopy, respectively. Depending on the polymer sources, the hexagonal structure prepared by using non-surfactant of water completely changed to monoclinic structure when CTAB was added into the process. X-ray absorption near edge structure (XANES) and X-ray photoelectron spectroscopy (XPS) was used to study the local structure and surface electronic structure of the prepared samples confirming that the oxidation states of P and Zn ions are 5+ and 2+, respectively. By using ICP-OES technique, our NH4ZnPO4 powders can be classified as a slow-release fertilizer where less than 15% of the ions was released in 24 h. This study shows that a simple precipitation method using water, PVP, PVA, sucrose and CTAB as a template can be used to synthesize NH4ZnPO4 powders. In addition, this method may be extended for the preparation of other oxide materials.
Research Article
Parametric study of spark plasma sintering of Al20Cr20Fe25Ni25Mn10 high entropy alloy with improved microhardness and corrosion
Andries Mthisi, Nicholus Malatji, A. Patricia I. Popoola, and L. Rudolf Kanyane
Available online 25 September 2020, https://doi.org/10.1007/s12613-020-2200-3
[Abstract](1258) [PDF 1157KB](22)
Multicomponent Al20Cr20Fe25Ni25Mn10 alloys were synthesized using spark plasma sintering at temperatures (800 °C, 900 °C and 1000 °C) and holding times (4, 8 and 12 minutes), with aim to develop a high entropy alloy (HEA). The characteristics of spark plasma synthesized (SPSed) alloys were experimental explored through investigation of microstructures, microhardness and corrosion using scanning electron microscope coupled with energy dispersive spectroscopy, Vickers microhardness tester and potentiodynamic polarization respectively. Also, X-ray diffractometry characterization was employed to identify the phases formed on the alloys developed. The EDS results revealed that the alloys consist of elements selected in this work irrespective of varying the sintering parameters. Also, the XRD, EDS and SEM collectively provided evidence that the fabricated alloys are characterized by globular microstructures exhibiting FCC phase formed on a basis of solid solution mechanism; this implies that SPSed alloy shows features of HEAs. The alloy produced at 1000 °C and holding time 12 minutes portrayed an optimal microhardness of 447.97 HV, however, this microhardness decreased to 329.47 HV after heat treatment. The same alloy showed outstanding corrosion resistance performance. Increase in temperature resulted in Al20Cr20Fe25Ni25Mn10 alloy with superior density, microhardness and corrosion resistance over other alloys developed at different parameters.
Research Article
Effect of graphene-oxide on corrosion, mechanical and biological properties of Mg-based nanocomposite
Saeid Jabbarzare, Hamid Reza Bakhsheshi-Rad, Amir Abbas Nourbakhsh, Tahmineh Ahmadi, and Filippo Berto
Available online 25 September 2020, https://doi.org/10.1007/s12613-020-2201-2
[Abstract](1359) [PDF 2126KB](29)
The purpose of this paper is to investigate the role of graphene oxide (GO) on mechanical and corrosion behaviors, antibacterial performance, and cell response of Mg-Zn-Mn (MZM) composite. MZM/GO nanocomposites were made with various amounts of GO (0.5, 1.0, and 1.5 wt.%) by the semi powder metallurgy method. The GO influence on the MZM composite was analyzed by hardness, compressive and corrosion tests, and antibacterial and cytotoxicity tests. According to the experimental results, increasing the GO amount increased hardness values, compressive value, and antibacterial performance of the MZM composite, while cell viability and osteogenesis level presented reversed trends. It was shown, based on the electrochemical examination, which the corrosion behavior of the MZM alloy was significantly enhanced after encapsulation of 0.5 wt.% GO. Taken together, the antibacterial and mechanically MZM nanocomposites reinforced with GO to be used for implant applications.
Research Article
Interface behavior of chalcopyrite during flotation from cyanide tailings
Xue-min Qiu, Hong-ying Yang, Guo-bao Chen, Lin-lin Tong, Zhe-nan Jin, and Qin Zhang
Available online 27 August 2020, https://doi.org/10.1007/s12613-020-2170-5
[Abstract](1460) [PDF 1042KB](18)
Interface characteristics of cyanide tailings are very different compared with those of raw ore. Valuable elements could not be comprehensively recovered via flotation from cyanide tailings originating from Shandong province, China. Herein, the interface and floatability of these tailings were investigated. The chalcopyrite in the cyanide tailings investigated herein was fine with a porous surface. The floatability of 68% chalcopyrite was similar to galena in the presence of a collector. This part of chalcopyrite was compactly wrapped in a layer of fine galena particles. The recovery of chalcopyrite sharply decreased as the nonpolar oil residue in cyanide tailings was removed through alcohol extraction; however, this removal had no effect on galena. The other chalcopyrite in the flotation tailings was covered with an oxidation layer consisting of O, Fe, S, Pb, Cu, Zn, and Si.
Research Article
Carbothermic reduction of vanadium titanomagnetite with the assistance of sodium carbonate
Lu-ming Chen, Yu-lan Zhen, Guo-hua Zhang, De-sheng Chen, Li-na Wang, Hong-xin Zhao, Fan-cheng Meng, and Tao Qi
Available online 10 August 2020, https://doi.org/10.1007/s12613-020-2160-7
[Abstract](1495) [PDF 2054KB](36)
In the present study, the carbothermic reduction of vanadium titanomagnetite concentrates (VTC) with the assistance of Na2CO3 was carried out in argon atmosphere between 1073 K and 1473 K. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to investigate the phase transformations during the reaction process. By investigating the reaction between VTC and Na2CO3, it was concluded that molten Na2CO3 could break the structure of titanomagnetite by combining with the acidic oxides (Fe2O3, TiO2, Al2O3, and SiO2) to form the Na-rich melt, and release FeO and MgO. Therefore, Na2CO3 could accelerate the reduction rate. In addition, the addition of Na2CO3 was also beneficial for the agglomeration of iron particles and the slag-metal separation by decreasing the viscosity of slag. Thus, the Na2CO3 assisted carbothermic reduction will be a promising method to treat VTC at low temperatures.
Research Article
Process and kinetics of the selective extraction of cobalt from high-silicon low-grade cobalt ore by ammonia leaching
Lei Tian, Ao Gong, Xuan-gao Wu, Xiao-qiang Yu, Zhi-feng Xu, and Li-jie Chen
Available online 10 August 2020, https://doi.org/10.1007/s12613-020-2161-6
[Abstract](1436) [PDF 1527KB](6)
In this study, an ammonia-based system was used to selectively leach Co from an African high-silicon low-grade Co ore. In this process, other elemental impurities were prevented from leaching; hence, the subsequent process was simple and environmentally friendly. The results revealed that the leaching ratio of Co can reach 95.61% using (NH4)2SO4 as a leaching agent under experimental conditions, which involved a (NH4)2SO4 concentration, reductant dosage, leaching temperature, reaction time, and liquid–solid ratio of 300 g/L, 0.7 g, 353 K, 4 h, and 6:1, respectively. The leaching kinetics of Co showed that the apparent activation energy of Co leaching was 72.97 kJ/mol (i.e., in the range of 40–300 kJ/mol). This indicated that the leaching of Co from the Co ore was controlled using an interfacial chemical reaction. The reaction orders of the particle size and (NH4)2SO4 concentration during leaching were 0.21 and 1.5, respectively. The leaching kinetics model of the Co developed in this study can be expressed as 1-(1-α)1/3 = 28.01 × 103×r0-1 × [(NH4)2SO4]1.5 × exp(-72970/8.314T).
Research Article
Effect of calcination temperature on the pozzolanic activity of maize straw stem ash treated with portlandite solution
Ting-ye Qi, Hao-chen Wang, Guo-rui Feng, Yu-jiang Zhang, Jin-wen Bai, and Yan-na Han
Available online 24 July 2020, https://doi.org/10.1007/s12613-020-2148-3
[Abstract](1549) [PDF 1117KB](25)
The effect of calcination temperature on the pozzolanic activity of maize straw stem ash (MSSA) was evaluated. The MSSA samples calcined at temperature values of 500, 700, and 850 °C were dissolved in portlandite solution for 6 h, and the residual samples were obtained. The MSSA and MSSA residual samples were analyzed using FT-IR, XRD, SEM, and XPS to determine the vibration bonds, minerals, microstructure, and Si 2p transformation behavior. The conductivity, pH value, loss of conductivity with dissolving time of the MSSA-portlandite mixed solution were determined. The main oxide composition of MSSA were silica and potassium oxide. The dissolution of Si4+ content of MSSA at 500 °C were high compared to those of the other calcination temperatures. The conductivity and loss of conductivity of MSSA at 700 °C were high compared to those of the other calcination temperatures at a particular dissolving time due to the higher KCl content in MSSA at 700 °C. C-S-H was easily identified in MSSA samples using XRD, and small cubic and nearly spherical particles of C-S-H were found in the MSSA residual samples. In conclusion, the optimum calcination temperature of MSSA having the best pozzolanic activity is 500 °C but avoid excessive agglomeration.
Research Article
A new electrochemical process on the recovery metallic Mn from waste LiMn2O4 based Li-ion batteries in NaCl-CaCl2 melts
Jing-long Liang, Dong-bin Wang, Le Wang, Hui Li, Wei-gang Cao, and Hong-yan Yan
Available online 16 July 2020, https://doi.org/10.1007/s12613-020-2144-7
[Abstract](1621) [PDF 798KB](25)
A new method for the recovery of Mn is proposed via direct electrochemical reduction of LiMn2O4 from the waste lithium-ion batteries in NaCl-CaCl2 melts at 750℃. The results show the reduction process of LiMn2O4 by electrochemical methods on the coated electrode surface are in three steps, Mn(IV) → Mn(III) → Mn(II) → Mn. The products of electro-deoxidation are CaMn2O4, MnO, (MnO)x(CaO)1-x and Mn. Metal Mn appears when the electrolytic voltage increased to 2.6 V. Increasing the voltage could promote the deoxidation reaction process. With the advancement of the three-phase interline(3PI), the electric deoxygenation gradually proceeds from the outward to core. With the high voltage, the kinetic process of the reduction reaction is accelerated, and double 3PI in different stages are generated.
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Research Article
Structural and Bader charge analysis of hydration reactivity difference between dicalcium silicate and tricalcium silicate
Chong-chong Qi, Xin-hang Xu, and Qiu-song Chen
  Available online 15 October 2021, https://doi.org/10.1007/s12613-021-2364-5
[FullText HTML](251) [PDF 1432KB](19) SpringerLink
Cement hydration is the underlying mechanism for the strength development in cement-based materials. The structural and electronic properties of calcium silicates should be elucidated to reveal their difference in hydration reactivity. Here, we comprehensively compared β-C2S and M3-C3S and investigated their structural properties and Bader charge in the unit cell during surface reconstruction and after single water adsorption via density functional theory. We identified different types of atoms in β-C2S and M3-C3S by considering the bonding characteristics and Bader charge. We then divided the atoms into the following groups: for β-C2S, Ca and O atoms divided into two and four groups, respectively; for M3-C3S, Ca, O, and Si atoms divided into four, four, and three groups, respectively. Results revealed that the valence electron distribution on the surface was more uniform than that on the unit cell, indicating that some atoms became more reactive after surface relaxation. During water adsorption, the electrons of β-C2S and M3-C3S were transferred from the surface to the adsorbed water molecules through position redistribution and bond formation/breaking. On this basis, we explained why β-C2S and M3-C3S had activity differences. A type of O atom with special bond characteristics (no O–Si bonds) and high reactivity existed in the unit cell of M3-C3S. Bader charge analysis showed that the reactivity of Ca and O atoms was generally higher in M3-C3S than in β-C2S. Ca/O atoms had average valence electron numbers of 6.437/7.550 in β-C2S and 6.481/7.537 in M3-C3S. Moreover, the number of electrons gained by water molecules in M3-C3S at the surface was higher than that in β-C2S. The average variations in the valence electrons of H2O on β-C2S and M3-C3S were 0.041 and 0.226, respectively. This study further explains the differences in the hydration reactivity of calcium silicates and would be also useful for the design of highly reactive and environmentally friendly cements.
Novel Cr3+-activated far-red emitting phosphors with β-Ca3(PO4)2-type structure for indoor plant cultivation
Fangyi Zhao, Zhen Song, and Quanlin Liu
  Available online 12 October 2021, https://doi.org/10.1007/s12613-021-2363-6
[FullText HTML](129) [PDF 1303KB](17) SpringerLink
Cr3+-activated far-red and near-infrared phosphors have drawn considerable attention owing to their adjustable emission wavelengths and wide applications. Herein, we reported a series of Cr3+-doped phosphors with β-Ca3(PO4)2-type structure, of which Ca9Ga(PO4)7:Cr3+ possessed the highest far-red emission intensity. At an excitation of 440 nm, the Ca9Ga(PO4)7:Cr3+ phosphors exhibited a broad emission band ranging from 650 to 850 nm and peaking at 735 nm and superimposed two sharp lines centered at 690 and 698 nm. The optimal sample Ca9Ga0.97(PO4)7:0.03Cr3+ had an internal quantum efficiency of 55.7%. The luminescence intensity of the Ca9Ga0.97(PO4)7:0.03Cr3+ phosphor obtained at 423 K could maintain 68.5% of that at room temperature, demonstrating its outstanding luminescence thermal stability. A phosphor-conversion light-emitting diode was fabricated, indicating that the Ca9Ga(PO4)7:Cr3+ phosphor has potential applications in indoor plant cultivation.
Mica-stabilized polyethylene glycol composite phase change materials for thermal energy storage
Dongyao Zhang, Chuanchang Li, Niangzhi Lin, Baoshan Xie, and Jian Chen
  Available online 24 September 2021, https://doi.org/10.1007/s12613-021-2357-4
[FullText HTML](176) [PDF 1279KB](19) SpringerLink
Mica was used as a supporting matrix for composite phase change materials (PCMs) in this work because of its distinctive morphology and structure. Composite PCMs were prepared using the vacuum impregnation method, in which mica served as the supporting material and polyethylene glycol (PEG) served as the PCM. Fourier transform infrared and X-ray diffraction analysis confirmed that the addition of PEG had no effect on the crystal structure of mica. Moreover, no chemical reaction occurred between PEG and mica during the vacuum impregnation process, and no new substance was formed. The maximum load of mica-stabilized PEG was 46.24%, the phase change temperature of M400/PEG was 46.03°C, and the latent heat values of melting and cooling were 77.75 and 77.73 J·g−1, respectively. The thermal conductivity of M400/PEG was 2.4 times that of pure PEG. The thermal infrared images indicated that the thermal response of M400/PEG improved relative to that of pure PEG. The leakage test confirmed that mica could stabilize PEG and that M400/PEG had great form-stabilized property. These results demonstrate that M400/PEG has potential in the field of building energy conservation.
Research Article
Multicomponent transition metal phosphide for oxygen evolution
Lihua Liu, Ning Li, Jingrui Han, Kaili Yao, and Hongyan Liang
  Available online 10 September 2021, https://doi.org/10.1007/s12613-021-2352-9
[FullText HTML](136) [PDF 1608KB](7) SpringerLink
Transition metal phosphides (TMPs) have exhibited decent performance in an oxygen evolution reaction (OER), which is a kinetic bottleneck in many energy storages and conversion systems. Most reported catalysts are composed of three or fewer metallic components. The inherent complexity of multicomponent TMPs with more than four metallic components hinders their investigation in rationally designing the structure and, more importantly, comprehending the component-activity correlation. Through hydrothermal growth and subsequent phosphorization, we reported a facile strategy for combining TMPs with tunable elemental compositions (Ni, Fe, Mn, Co, Cu) on a two-dimensional titanium carbide (MXene) flake. The obtained TMPs/MXene hybrid nanostructures demonstrate homogeneously distributed elements. They exhibit high electrical conductivity and strong interfacial interaction, resulting in an accelerated reaction kinetics and long-term stability. The results of different component catalysts’ OER performance show that NiFeMnCoP/MXene is the most active catalyst, with a low overpotential of 240 mV at 10 mA·cm−2, a small Tafel slope of 41.43 mV·dec−1, and a robust long-term electrochemical stability. According to the electrocatalytic mechanism investigation, the enhanced NiFeMnCoP/MXene OER performance is due to the strong synergistic effect of the multi-elemental composition. Our work, therefore, provides a scalable synthesis route for multi-elemental TMPs and a valuable guideline for efficient MXene-supported catalysts design.
Research Article
Compressive fatigue behavior and failure evolution of additive fiber-reinforced cemented tailings composites
Jia-jian Li, Shuai Cao, Erol Yilmaz, and Yun-peng Liu
  Available online 10 September 2021, https://doi.org/10.1007/s12613-021-2351-x
[FullText HTML](197) [PDF 2232KB](27) SpringerLink
The ordinary cemented tailings backfill (CTB) is a cement-based composite prepared from tailings, cementitious materials, and water. In this study, a series of laboratory tests, including uniaxial compression, digital image correlation measurement, and scanning electron microscope characteristics of fiber-reinforced CTB (FRCTB), was conducted to obtain the uniaxial compressive strength (UCS), failure evolution, and microstructural characteristics of FRCTB specimens. The results show that adding fibers could increase the UCS values of the CTB by 6.90% to 32.76%. The UCS value of the FRCTB increased with the increase in the polypropylene (PP) fiber content. Moreover, the reinforcement effect of PP fiber on the CTB was better than that of glass fiber. The addition of fiber could increase the peak strain of the FRCTB by 0.39% to 1.45%. The peak strain of the FRCTB increased with the increase in glass fiber content. The failure pattern of the FRCTB was coupled with tensile and shear failure. The addition of fiber effectively inhibited the propagation of cracks, and the bridging effect of cracks by the fiber effectively improved the mechanical properties of the FRCTB. The findings in this study can provide a basis for the backfilling design and optimization of mine backfilling methods.
Invited Review
A review of the strengthening–toughening behavior and mechanisms of advanced structural materials by multifield coupling treatment
Xiu Song, Lei Wang, and Yang Liu
  Available online 10 September 2021, https://doi.org/10.1007/s12613-021-2350-y
[FullText HTML](78) [PDF 3151KB](6) SpringerLink
The application of an external field is a promising method to control the microstructure of materials, leading to their improved performance. In the present paper, the strengthening and toughening behavior of some typical high-performance structural materials subjected to multifield coupling treatment, including electrostatic field, electro-pulse current, thermal field, and stress field, are reviewed in detail. In addition to the general observation that the plasticity of materials could be increased by multi-external fields, strength enhancement can be achieved by controlling atomic diffusion or phase transformations. The paper is not limited to the strengthening and toughening mechanisms of the multifield coupling effects on different types of structural materials but is intended to provide a generic method to improve both the strength and ductility of the materials. Finally, the prospects of the applications of multi-external fields have also been proposed based on current works.
Research Article
In situ carbon coating for enhanced chemical stability of copper nanowires
Xiaolan Tong, Hao Hu, Xingzhong Zhao, and Qidong Tai
  Available online 21 August 2021, https://doi.org/10.1007/s12613-021-2343-x
[FullText HTML](138) [PDF 837KB](14) SpringerLink
Copper nanowires (CuNWs) are promising electrode materials, especially for used in flexible and transparent electrodes, due to their advantages of earth-abundant, low-cost, high conductivity and flexibility. However, the poor stability of CuNWs against oxidation and chemical corrosion seriously hinders their practical applications. Herein, we propose a facile strategy to improve the chemical stability of CuNWs by in situ coating of carbon protective layer on top of them through hydrothermal carbonization method. The influential factors on the growth of carbon film including the concentration of the glucose precursor (carbon source), hydrothermal temperature, and hydrothermal time are systematically studied. By tailoring these factors, carbon layers with thickness of 3–8 nm can be uniformly grown on CuNWs with appropriate glucose concentration around 80 mg·mL−1, hydrothermal temperature of 160–170°C, and hydrothermal time of 1–3 h. The as-prepared carbon-coated CuNWs show excellent resistance against corrosion and oxidation, and are of great potential to use broadly in various optoelectronic devices.
Microstructure, mechanical properties and deformation mechanisms of an Al–Mg alloy processed by the cyclical continuous expanded extrusion and drawing approach
Ruiqing Lu, Long Zhang, Shuwei Zheng, Dingfa Fu, Jie Teng, Jianchun Chen, Guodong Zhao, Fulin Jiang, and Hui Zhang
  Available online 18 August 2021, https://doi.org/10.1007/s12613-021-2342-y
[FullText HTML](124) [PDF 1704KB](8) SpringerLink
Al–Mg alloys are an important class of non-heat treatable alloys in which Mg solute and grain size play essential role in their mechanical properties and plastic deformation behaviors. In this work, a cyclical continuous expanded extrusion and drawing (CCEED) process was proposed and implemented on an Al–3Mg alloy to introduce large plastic deformation. The results showed that the continuous expanded extrusion mainly improved the ductility, while the cold drawing enhanced the strength of the alloy. With the increased processing CCEED passes, the multi-pass cross shear deformation mechanism progressively improved the homogeneity of the hardness distributions and refined grain size. Continuous dynamic recrystallization played an important role in the grain refinement of the processed Al–3Mg alloy rods. Besides, the microstructural evolution was basically influenced by the special thermomechanical deformation conditions during the CCEED process.
Invited Review
Controlled crystal orientation of two-dimensional Ruddlesden–Popper halide perovskite films for solar cells
Jiuyao Du, Mengqi Zhang, and Jianjun Tian
  Available online 18 August 2021, https://doi.org/10.1007/s12613-021-2341-z
[FullText HTML](188) [PDF 1203KB](30) SpringerLink
Metal halide perovskite solar cells have attracted considerable attention because of their high-power conversion efficiency and cost-effective solution-processable fabrication; however, they exhibit poor structural stability. Two-dimensional (2D) Ruddlesden–Popper (RP) perovskites could address the aforementioned issue and present excellent stability because of their hydrophobic organic spacer cations. However, the crystallographic orientation of 2D crystals should be perpendicular to the bottom substrates for charges to transport fast and be collected in solar cells. Moreover, controlling the crystallographic orientation of the 2D RP perovskites prepared by the solution process is difficult. Herein, we reviewed the progress of recent research regarding 2D RP perovskite films with the focus on the crystallographic orientation mechanism and orientation controlling methods. Furthermore, the current issues and prospects of 2D RP perovskites in the photovoltaic field were discussed to elucidate their development and application in the future.
Kinetics of the hydrogen absorption and desorption processes of hydrogen storage alloys: A review
Qian Li, Xi Lin, Qun Luo, Yuan Chen, Jingfeng Wang, Bin Jiang, and Fusheng Pan
  Available online 6 August 2021, https://doi.org/10.1007/s12613-021-2337-8
[FullText HTML](1162) [PDF 1380KB](89) SpringerLink
High hydrogen absorption and desorption rates are two significant index parameters for the applications of hydrogen storage tanks. The analysis of the hydrogen absorption and desorption behavior using the isothermal kinetic models is an efficient way to investigate the kinetic mechanism. Multitudinous kinetic models have been developed to describe the kinetic process. However, these kinetic models were deduced based on some assumptions and only appropriate for specific kinetic measurement methods and rate-controlling steps (RCSs), which sometimes lead to confusion during application. The kinetic analysis procedures using these kinetic models, as well as the key kinetic parameters, are unclear for many researchers who are unfamiliar with this field. These problems will prevent the kinetic models and their analysis methods from revealing the kinetic mechanism of hydrogen storage alloys. Thus, this review mainly focuses on the summarization of kinetic models based on different kinetic measurement methods and RCSs for the chemisorption, surface penetration, diffusion of hydrogen, nucleation and growth, and chemical reaction processes. The analysis procedures of kinetic experimental data are expounded, as well as the effects of temperature, hydrogen pressure, and particle radius. The applications of the kinetic models for different hydrogen storage alloys are also introduced.
Invited Review
Research progress on selective laser melting processing for nickel-based superalloy
Maohang Zhang, Baicheng Zhang, Yaojie Wen, and Xuanhui Qu
  Available online 19 July 2021, https://doi.org/10.1007/s12613-021-2331-1
[FullText HTML](293) [PDF 2554KB](32) SpringerLink
Selective laser melting (SLM), an additive manufacturing process mostly applied in the metal material field, can fabricate complex-shaped metal objects with high precision. Nickel-based superalloy exhibits excellent mechanical properties at elevated temperatures and plays an important role in the aviation industry. This paper emphasizes the research of SLM processed Inconel 718, Inconel 625, CM247LC, and Hastelloy X, which are typical alloys with different strengthening mechanisms and operating temperatures. The strengthening mechanism and phase change evolution of different nickel-based superalloys under laser irradiation are discussed. The influence of laser parameters and the heat-treatment process on mechanical properties of SLM nickel-based superalloys are systematically introduced. Moreover, the attractive industrial applications of SLM nickel-based superalloy and printed components are presented. Finally, the prospects for nickel-based superalloy materials for SLM technology are presented.
Preparation and oxidation characteristics of ZrC–ZrB2 composite powders with different proportions
Yu Wang, Guohua Zhang, and Kuochih Chou
  Available online 13 July 2021, https://doi.org/10.1007/s12613-021-2330-2
[FullText HTML](142) [PDF 2133KB](14) SpringerLink
ZrC and ZrB2 are both typical ultra-high temperature ceramics, which can be used in the hyperthermal environment. In this study, a method for preparing ultrafine ZrC–ZrB2 composite powder was provided, by using the raw materials of nano ZrO2, carbon black, B4C, and metallic Ca. It is worth pointing out that ZrC–ZrB2 composite powder with any proportion of ZrC to ZrB2 could be synthesized by this method. Firstly, a mixture of ZrC and C was prepared by carbothermal reduction of ZrO2. By adjusting the addition amount of B4C, ZrC was boronized by B4C to generate ZrC–ZrB2 composite powder with different compositions. Using this method, five composition powders with different molar ratios (100ZrC, 75ZrC–25ZrB2, 50ZrC–50ZrB2, 25ZrC–75ZrB2, and 100ZrB2) were prepared. When the temperature of boronization and decarburization process was 1473 K, the particle size of product was only tens of nanometres. Finally, the oxidation characteristics of different composite powders were investigated through oxidation experiments. The oxidation resistance of ZrC–ZrB2 composite powder continued to increase as the content of ZrB2 increased.
Recent progress of efficient utilization of titanium-bearing blast furnace slag
Yongfeng Cai, Ningning Song, Yunfei Yang, Lingmin Sun, Peng Hu, and Jinshu Wang
  Available online 30 June 2021, https://doi.org/10.1007/s12613-021-2323-1
[FullText HTML](194) [PDF 1291KB](19) SpringerLink
Titanium-bearing blast furnace slag (BFS) has valuable compositions and potential environmental hazardousness. Thus, developing efficient and green approaches to utilize BFS is highly desired for resource economization and environmental protection. In the past decades, many attempts have been adopted to reuse BFS efficiently, and significant advances in understanding the fundamental features and the development of efficient approaches have been achieved. This review provides a comprehensive overview of the latest progress on the efficient utilization of BFS and discusses the mechanism and characteristics of various approaches, along with their application prospects. In particular, the extraction and enrichment of titanium-bearing phases from BFS are highlighted because of the high availability of titanium resources. This systemic and comprehensive review may benefit the design of new and green utilization routes with high efficiency and low cost.
High thermal conductivity and high strength magnesium alloy for high pressure die casting ...
Jian Rong, Wenlong Xiao, Xinqing Zhao, Chaoli Ma, Haimiao Liao, Donglei He, Ming Chen, Meng Huang, and Chen Huang
  Available online 18 June 2021, https://doi.org/10.1007/s12613-021-2318-y
[FullText HTML](215) [PDF 1067KB](16) SpringerLink
With the rapid development of 3C industries, the demand for high-thermal-conductivity magnesium alloys with high mechanical performance is increasing quickly. However, the thermal conductivities of most common Mg foundry alloys (such as Mg–9wt%–1wt%Zn) are still relatively low. In this study, we developed a high-thermal-conductivity Mg–4Al–4Zn–4RE–1Ca (wt%, AZEX4441) alloy with good mechanical properties for ultrathin-walled cellphone components via high-pressure die casting (HPDC). The HPDC AZEX4441 alloy exhibited a fine homogeneous microstructure (average grain size of 2.8 μm) with granular Al11RE3, fibrous Al2REZn2, and networked Ca6Mg2Zn3 phases distributed at the grain boundaries. The room-temperature thermal conductivity of the HPDC AZEX4441 alloy was 94.4 W·m–1·K–1, which was much higher than 53.7 W·m–1·K–1 of the HPDC AZ91D alloy. Al and Zn in the AZEX4441 alloy were largely consumed by the formation of Al11RE3, Al2REZn2, and Ca2Mg6Zn3 phases because of the addition of RE and Ca. Therefore, the lattice distortion induced by solute atoms of the AZEX4441 alloy (0.171%) was much lower than that of the AZ91D alloy (0.441%), which was responsible for the high thermal conductivity of the AZEX4441 alloy. The AZEX4441 alloy exhibited a high yield strength of ~185 MPa, an ultimate tensile strength of ~233 MPa, and an elongation of ~4.2%. This result indicated that the tensile properties were comparable with those of the AZ91D alloy. Therefore, this study contributed to the development of high-performance Mg alloys with a combination of high thermal conductivity, high strength, and good castability.
Research Article
Kinetic analysis and modeling of maize straw hydrochar combustion using a multi-Gaussian-distributed activation energy model
Chun-mei Yu, Shan Ren, Guang-wei Wang, Jun-jun Xu, Hai-peng Teng, Tao Li, Chun-chao Huang, and Chuan Wang
  Available online 18 May 2021, https://doi.org/10.1007/s12613-021-2305-3
[FullText HTML](180) [PDF 1179KB](11) SpringerLink
Combustion kinetics of the hydrochar was investigated using a multi-Gaussian-distributed activation energy model (DAEM) to expand the knowledge on the combustion mechanisms. The results demonstrated that the kinetic parameters calculated by the multi-Gaussian-DAEM accurately represented the experimental conversion rate curves. Overall, the feedstock combustion could be divided into four stages: the decomposition of hemicellulose, cellulose, lignin, and char combustion. The hydrochar combustion could in turn be divided into three stages: the combustion of cellulose, lignin, and char. The mean activation energy ranges obtained for the cellulose, lignin, and char were 273.7–292.8, 315.1–334.5, and 354.4–370 kJ/mol, respectively, with the standard deviations of 2.1–23.1, 9.5–27.4, and 12.1–22.9 kJ/mol, respectively. The cellulose and lignin contents first increased and then decreased with increasing hydrothermal carbonization (HTC) temperature, while the mass fraction of char gradually increased.
Research Article
Incorporation of nano/micron-SiC particles in Ni-based composite coatings towards enhanced mechanical and anti-corrosion properties
Bowei Zhang, Qiao Zhang, Zhan Zhang, Kui Xiao, Qiong Yao, Guojia Ma, Gang Sun, and Junsheng Wu
  Available online 18 May 2021, https://doi.org/10.1007/s12613-021-2307-1
[FullText HTML](165) [PDF 938KB](11) SpringerLink
In the manuscript, Ni-based composite coatings incorporated with nano/micron SiC particles were fabricated via electrochemical co-deposition in Watts bath, followed by the evaluation of their mechanical and anti-corrosion properties. The micrographic observations suggest that the SiC particles with various sizes can be well incorporated to the Ni substrate. X-ray diffraction (XRD) patterns indicate that SiC particles with smaller sizes could weaken the preferential growth of Ni along (2 0 0) facet. In addition, it is found that the incorporated SiC particles with medium micron sizes (8 and 1.5 μm) could significantly enhance the micro-hardness of the Ni composite coatings. Nevertheless, electrochemical measurements demonstrate that micron-sized SiC particles would weaken the corrosion resistance of Ni composite coatings ascribed to the structure defects induced. In contrast, the combined incorporation of nanosized (50 nm) SiC particles with medium micron (1.5 μm) ones is capable of promoting the compactness of the composite coatings, which is beneficial to the long-term corrosion resistance with negligible micro-hardness loss.
Research Article
Chemical vapor deposition growth behavior of graphene
Jie Wang, Tengfei Fan, Jianchen Lu, Xiaoming Cai, Lei Gao, and Jinming Cai
  Available online 9 May 2021, https://doi.org/10.1007/s12613-021-2302-6
[FullText HTML](189) [PDF 918KB](14) SpringerLink
The optimized growth parameters of graphene with different morphologies, such as dendrites, rectangle, and hexagon, have been obtained by low-pressure chemical vapor deposition on polycrystalline copper substrates. The evolution of fractal graphene, which grew on the polycrystalline copper substrate, has also been observed. When the equilibrium growth state of graphene is disrupted, its intrinsic hexagonal symmetry structure will change into a non-hexagonal symmetry structure. Then, we present a systematic and comprehensive study of the evolution of graphene with different morphologies grown on solid copper as a function of the volume ratio of methane to hydrogen in a controllable manner. Moreover, the phenomena of stitching snow-like graphene together and stacking graphene with different angles was also observed.
Research Article
Effect of Al content on the reaction between Fe−10Mn−xAl (x = 0.035wt%, 0.5wt%, 1wt%, and 2wt%) steel and CaO−SiO2−Al2O3−MgO slag
Hui-xiang Yu, De-xin Yang, Jia-ming Zhang, Guang-yuan Qiu, and Ni Zhang
  Available online 28 April 2021, https://doi.org/10.1007/s12613-021-2298-y
[FullText HTML](154) [PDF 1247KB](23) SpringerLink
The effect of Al content (0.035wt%, 0.5wt%, 1wt%, and 2wt%) on the composition change of steel and slag as well as inclusion transformation of high manganese steel after it has equilibrated with CaO−SiO2−Al2O3−MgO slag was studied using the method of slag/steel reaction. The experimental results showed that as the initial content of Al increased from 0.035wt% to 2wt%, Al gradually replaced Mn to react with SiO2 in slag to avoid the loss of Mn due to the reaction; this process caused both Al2O3 in slag and Si in steel to increase while SiO2 and MnO in slag to reduce. In addition, the type of inclusions also evolved as the initial Al content increased. The evolution route of inclusions was MnO → MnO−Al2O3−MgO → MgO → MnO−CaO−Al2O3−MgO and MnO−CaO−MgO. The shape of inclusions evolved from spherical to irregular, became faceted, and finally transformed to spherical. The average size of inclusions presented a trend that was increasing first and then decreasing. The transformation mechanism of inclusions was explored. As the initial content of Al increased, Mg and Ca were reduced from top slag into molten steel in sequence, which consequently caused the transformation of inclusions.
Research Article
Effect of extrusion process on microstructure and mechanical and corrosion properties of biodegradable Mg–5Zn–1.5Y magnesium alloy
Hassan Jafari, Amir Houshang, Mojiri Tehrani, and Mahsa Heydari
  Available online 27 February 2021, https://doi.org/10.1007/s12613-021-2275-5
[FullText HTML](424) [PDF 1877KB](22) SpringerLink
The effect of extrusion temperature and ratio on the microstructure, hardness, compression, and corrosion behavior of Mg–5Zn–1.5Y alloy were analyzed in this study. The microstructural observations revealed that the cast alloy consists of α-Mg grains, and Mg3Zn6Y and Mg3Zn3Y2 intermetallic compounds, mostly located on the α-Mg grain boundaries. Extruded alloy at higher temperatures showed coarser grain microstructures, whereas those extruded at higher ratios contained finer ones, although more dynamic recrystalized grains with lower intermetallics were measured at both conditions. Combined conditions of the lower temperature (340°C) and higher ratio (1:11.5) provided higher compressive strengths. However, no significant hardness improvement was achieved. The extrusion process could decrease the corrosion rate of the cast alloy in simulated body fluid for over 80% due to primarily the refined microstructure. The extrusion temperature showed a more pronounced effect on corrosion resistance compared to the extrusion ratio, and the higher the extrusion temperature, the higher the corrosion resistance.
Functionalization of diatomite with glycine and amino silane for formaldehyde removal
Yonghao Di, Fang Yuan, Xiaotian Ning, Hongwei Jia, Yangyu Liu, Xiangwei Zhang, Chunquan Li, Shuilin Zheng, and Zhiming Sun
  Available online 29 December 2020, https://doi.org/10.1007/s12613-020-2245-3
[FullText HTML](490) [PDF 351KB](25) SpringerLink
Two amino-functionalized diatomite (DE) composites modified by 3-aminopropyltriethoxysilane (APTS) or glycine (GLY) (i.e., APTS/DE and GLY/DE) were successfully synthesized via the wet chemical method for the time- and cost-efficient removal of indoor formaldehyde (HCHO). First, the optimal preparation conditions of the two composites were determined, and then their microstructures and morphologies were characterized and analyzed. Batch HCHO adsorption experiments with the two types of amino-modified DE composites were also conducted to compare their adsorption properties. Experimental results indicated that the pseudo-second-order kinetic and Langmuir isotherm models could well describe the adsorption process, and the maximum adsorption capacities of APTS/DE and GLY/DE prepared under optimal conditions at 20℃ were 5.83 and 1.14 mg·g−1, respectively. The thermodynamic parameters of the composites indicated that the adsorption process was spontaneous and exothermic. The abundant amine groups grafted on the surface of DE were derived from the Schiff base reaction and were essential for the high-efficient adsorption performance toward HCHO.
Research Article
Interfacial bonding characteristics and mechanical properties of H68/AZ31B clad plate
Ting-ting Zhang, Wen-xian Wang, Jie Zhang, and Zhi-feng Yan
  Available online 12 December 2020, https://doi.org/10.1007/s12613-020-2240-8
[FullText HTML](399) [PDF 3255KB](1) SpringerLink
Interfacial bonding, microstructures, and mechanical properties of an explosively-welded H68/AZ31B clad plate were systematically studied. According to the results, the bonding interface demonstrated a “wavy-like” structure containing three typical zones/layers: (1) diffusion layer adjacent to the H68 brass plate; (2) solidification layer of melted metals at the interface; (3) a layer at the side of AZ31B alloy that experienced severe deformation. Mixed copper, CuZn2, and α-Mg phases were observed in the melted-solidification layer. Regular polygonal grains with twins were found at the H68 alloy side, while fine equiaxed grains were found at the AZ31B alloy side near the interface due to recrystallization. Nanoindentation results revealed the formation of brittle intermetallic CuZn2 phases at the bonding interface. The interface was bonded well through metallurgical reactions due to diffusion of Cu, Zn, and Mg atoms across the interface and metallurgic reaction of partially melted H68 and AZ31B alloys.
Research Article
Activity coefficient of NiO in SiO2-saturated MnO–SiO2 slag and Al2O3-saturated MnO–SiO2–Al2O3 slag at 1623 K
Guoxing Ren, Songwen Xiao, Caibin Liao, and Zhihong Liu
  Available online 1 October 2020, https://doi.org/10.1007/s12613-020-2205-y
[FullText HTML](1291) [PDF 1006KB](45) SpringerLink
As a part of the fundamental study related to the reduction smelting of spent lithium-ion batteries and ocean polymetallic nodules based on MnO–SiO2 slags, this work investigated the activity coefficient of NiO in SiO2-saturated MnO–SiO2 slag and Al2O3-saturated MnO–SiO2–Al2O3 slag at 1623 K with controlled oxygen partial pressure levels of 10−7, 10−6, and 10−5 Pa. Results showed that the solubility of nickel oxide in the slags increased with increasing oxygen partial pressure. The nickel in the MnO–SiO2 slag and MnO–SiO2–Al2O3 slag existed as NiO under experimental conditions. The addition of Al2O3 in the MnO–SiO2 slag decreased the dissolution of nickel in the slag and increased the activity coefficient of NiO. Furthermore, the activity coefficient of NiO (γNiO), which is solid NiO, in the SiO2 saturated MnO–SiO2 slag and Al2O3 saturated MnO–SiO2–Al2O3 slag at 1623 K can be respectively calculated as γNiO = 8.58w(NiO) + 3.18 and γNiO = 11.06w(NiO) + 4.07, respectively, where w(NiO) is the NiO mass fraction in the slag.
Effect of cathodic potential on stress corrosion cracking behavior of 21Cr2NiMo steel in simulated seawater
Menghao Liu, Zhiyong Liu, Cuiwei D, Xiaoqin Zhan, Chunduo Dai, Yue Pan, and Xiaogang Li
  Available online 25 September 2020, https://doi.org/10.1007/s12613-020-2199-5
[FullText HTML](1205) [PDF 719KB](5) SpringerLink
This study aims at providing systematically insights to clarify the impact of cathodic polarization on the stress corrosion cracking (SCC) behavior of 21Cr2NiMo steel. Slow-strain-rate tensile tests demonstrated that 21Cr2NiMo steel is highly sensitive to hydrogen embrittlement at strong cathodic polarization. The lowest SCC susceptibility occurred at −775 mV vs. SCE, whereas the SCC susceptibility was remarkably higher at potentials below −950 mV vs. SCE. Scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) revealed that the cathodic potential decline caused a transition from transgranular to intergranular mode in the fracture path. The intergranular mode transformed from bainite boundaries separation to prior austenitic grain boundaries separation under stronger cathodic polarization. Furthermore, corrosion pits promoted the nucleation of SCC cracks. In conclusion, with the decrease in the applied potential, the SCC mechanism transformed from the combination of hydrogen embrittlement and anodic dissolution to typical hydrogen embrittlement.
Effect of cermet substrate characteristics on the microstructure and properties of TiAlN coatings
Qianbing You, Ji Xiong, Tianen Yang, Tao Hua, Yunliang Huo, and Junbo Liu
  Available online 25 September 2020, https://doi.org/10.1007/s12613-020-2198-6
[FullText HTML](1346) [PDF 1708KB](41) SpringerLink
The composition and structure of substrate materials have important influences on coating performance, especially in terms of bonding strength and coating hardness, which determine whether the coating can be used for a given application. In this study, a TiAlN coating is deposited on Ti(C,N)-based cermet (TC) substrates with 0wt%–20wt% WC by arc ion plating. The influence of cermet substrate characteristics on the structure and properties of the TiAlN coating is then researched. Results show that the TiAlN coating deposited on the TC substrate has a columnar grain structure. As WC increases, the strength ratio of I(111)/I(200) and adhesive strength of TiAlN gradually increases. In the absence of WC in the substrate, the preferred orientation of the TiAlN coating is (200). As WC increases, the preferred orientation of the TiAlN coating becomes (111) and (200). Notable differences in adhesive strength between the coating and substrate could be attributed to the microstructure and composition of the latter. Scratching results show that the adhesive strengths of the TiAlN coating on the 0wt%–20wt% WC cermet substrate are 52–65 N. Among the coatings obtained that on the TC substrate with 15wt% WC presents the highest H/E and H3/E2, which indicates that this coating also features the best wear resistance. The failure mechanisms of the coated tools include coating peeling, adhesive wear, and abrasive wear. As the cutting speed increases, the degree of flank wear increases and the durability of the coating decreases accordingly. Increases in WC result in an initial decrease followed by a gradual increase in the flank wear of the coated cermet inserts.
Research Article
Microstructure and tribological behavior of the nickel-coated-graphite-reinforced Babbitt metal composite fabricated via selective laser melting
Xingke Zhao and Xusheng Hai
  Available online 19 September 2020, https://doi.org/10.1007/s12613-020-2195-9
[FullText HTML](1271) [PDF 3401KB](5) SpringerLink
To improve the properties of Babbitt alloys, Ni-coated-graphite-reinforced Babbitt metal composite specimens were prepared via selective laser melting (SLM), and the composites microstructures, mechanical properties, and tribological properties were studied through scanning electron microscopy (SEM), shear testing, and dry-sliding wear testing, respectively. The results showed that most of the nickel-coated graphite (NCGr) particles were distributed at the boundaries of laser beads in the cross section of the SLM composite specimens. Microcracks and microvoids formed at the boundaries of laser beads where NCGr particles accumulated. Both the shear strength and the friction coefficient of the SLM composite specimens decreased with increasing NCGr content. The shear strength and the friction coefficient of the SLM composite sample with 6wt% NCGr were approximately 20% and 33% lower than those of the NCGr-free sample, respectively. The friction mechanism changed from plastic shaping furrow to brittle cutting with increasing NCGr content. A practical Babbitt material with a lower friction coefficient and sufficient strength can be obtained by controlling the NCGr particle dispersion; this can be achieved by choosing NCGr particles with a thicker Ni layer and precisely controlling the laser energy input during the SLM process.
Research Article
Flow zone distribution and mixing time in a Peirce–Smith copper converter
Hongliang Zhao, Jingqi Wang, Fengqin Liu, and Hong Yong Sohn
  Available online 19 September 2020, https://doi.org/10.1007/s12613-020-2196-8
[FullText HTML](1300) [PDF 1259KB](43) SpringerLink
Peirce–Smith copper converting involves complex multiphase flow and mixing. In this work, the flow zone distribution and mixing time in a Peirce–Smith copper converter were investigated in a 1:5 scaled cold model. Flow field distribution, including dead, splashing, and strong-loop zones, were measured, and a dimensionless equation was established to determine the correlation of the effects of stirring and mixing energy with an error of <5%. Four positions in the bath, namely, injection, splashing, strong-loop, and dead zones, were selected to add a hollow salt powder tracer and measure the mixing time. Injecting a quartz flux through tuyeres or into the backflow point of the splashing wave through a chute was recommended instead of adding it through a crane hopper from the top of the furnace to improve the slag-making reaction.
Research Article
Stress corrosion cracking behavior of high-strength mooring-chain steel in the SO2-polluted coastal atmosphere
Meng-hao Liu, Zhi-yong Liu, Cui-wei Du, Xiao-qin Zhan, Xiao-jia Yang, and Xiao-gang Li
  Available online 12 September 2020, https://doi.org/10.1007/s12613-020-2192-z
[FullText HTML](1429) [PDF 4970KB](6) SpringerLink
21Cr2NiMo steel is widely used to stabilize offshore oil platforms; however, it suffers from stress-corrosion cracking (SCC). Herein, we studied the SCC behavior of 21Cr2NiMo steel in SO2-polluted coastal atmospheres. Electrochemical tests revealed that the addition of SO2 increased the corrosion current. Rust characterization showed that SO2 addition densified the corrosion products and promoted pitting. Furthermore, slow strain rate tests demonstrated a high susceptibility to SCC in high SO2 contents. Fracture morphologies revealed that the stress-corrosion cracks initiated at corrosion pits and the crack propagation showed transgranular and intergranular cracking modes. In conclusion, SCC is mix-controlled by anodic dissolution and hydrogen embrittlement mechanisms.
Research Article
Synthesis, characterization and magnetic properties of KFeO2 nanoparticles prepared by a simple egg white solution route
Thongsuk Sichumsaeng, Nutthakritta Phromviyo, Supree Pinitsoontorn, Pinit Kidkhunthod, Narong Chanlek, and Santi Maensiri
  Available online 12 September 2020, https://doi.org/10.1007/s12613-020-2194-x
[FullText HTML](1509) [PDF 1004KB](21) SpringerLink
Nanoparticles of potassium ferrite (KFeO2) in this work were synthesized by a simple egg white solution method upon calcination in air at 773, 873, and 973 K for 2 h. The effects of calcination temperature on the structural and magnetic properties of the synthesized KFeO2 nanoparticles were investigated. By varying the calcination temperature, X-ray diffraction and transmission electron microscopy results indicated the changes in crystallinity and morphology including particle size, respectively. Notably, the reduction in particle size of the synthesized KFeO2 was found to have a remarkable influence on the magnetic properties. At room temperature, the synthesized KFeO2 nanoparticles prepared at 873 K exhibited the highest saturation magnetization (MS) of 2.07 × 104 A·m−1. In addition, the coercivity (HC) increased from 3.51 to 16.89 kA·m−1 as the calcination temperature increased to 973 K. The zero-field cooled (ZFC) results showed that the blocking temperatures (TB) of about 125 and 85 K were observed in the samples calcined at 773 and 873 K, respectively. Therefore, this work showed that the egg white solution method is simple, cost effective, and environmentally friendly for the preparation of KFeO2 nanoparticles.
Effect of graphene addition on the physicomechanical and tribological properties of Cu nanocomposites
Adnan I. Khdair and A. Ibrahim
  Available online 5 September 2020, https://doi.org/10.1007/s12613-020-2183-0
[FullText HTML](1398) [PDF 731KB](34) SpringerLink
This paper presents an experimental investigation of the mechanical and tribological properties of Cu–graphene nanosheets (GN) nanocomposites. We employed the electroless coating process to coat GNs with Ag particles to avoid its reaction with Cu and the formation of intermetallic phases. We analyzed the effect of GN content on the structural, mechanical, and tribological properties of the produced nanocomposites. Results showed that the electroless coating process is an efficient technique to avoid the reaction between Cu and C and the formation of intermetallic phases. The addition of GNs significantly improves the mechanical and tribological properties of Cu nanocomposites. However, the addition of GNs needs to be done carefully because, after a certain threshold value, the mechanical and tribological properties are negatively affected. The optimum GN content is determined to be 0.5vol%, at which hardness, wear rate, and coefficient of friction are improved by 13%, 81.9%, and 49.8%, respectively, compared with Cu nanocomposites. These improved properties are due to the reduced crystallite size, presence of GNs, and homogenous distribution of the composite constituents.
Three-dimensional graphitic carbon sphere foams as sorbents for cleaning oil spills
Saisai Li, Haijun Zhang, Longhao Dong, Haipeng Liu, and Quanli Jia
  Available online 3 September 2020, https://doi.org/10.1007/s12613-020-2180-3
[FullText HTML](1405) [PDF 737KB](13) SpringerLink
Frequent offshore oil spill accidents, industrial oily sewage, and the indiscriminate disposal of urban oily sewage have caused serious impacts on the human living environment and health. The traditional oil–water separation methods not only cause easily environmental secondary pollution but also a waste of limited resources. Therefore, in this work, three-dimensional (3D) graphitic carbon sphere (GCS) foams (collectively referred hereafter as 3D foams) with a 3D porous structure, pore size distribution of 25–200 μm, and high porosity of 62vol% were prepared for oil adsorption via gel casting using GCS as the starting materials. The results indicate that the water contact angle (WCA) of the as-prepared 3D foams is 130°. The contents of GCS greatly influenced the hydrophobicity, WCA, and microstructure of the as-prepared samples. The adsorption capacities of the as-prepared 3D foams for paraffin oil, vegetable oil, and vacuum pump oil were approximately 12–15 g/g, which were 10 times that of GCS powder. The as-prepared foams are desirable characteristics of a good sorbent and could be widely used in oil spill accidents.
Research Article
Fabrication of green one-part geopolymer from silica-rich vanadium tailing via thermal activation and modification
Shenxu Bao, Yongpeng Luo, and Yimin Zhang
  Available online 3 September 2020, https://doi.org/10.1007/s12613-020-2182-1
[FullText HTML](1588) [PDF 1536KB](31) SpringerLink
The aim of this investigation was to prepare geopolymeric precursor from vanadium tailing (VT) by thermal activation and modification. For activation, a homogeneous blend of VT and sodium hydroxide was calcinated at an elevated temperature and then modified with metakaolin to produce a geopolymeric precursor. During the thermal activation, the VT was corroded by sodium hydroxide and then sodium silicate formed on the particle surfaces. After water was added, the sodium silicate coating dissolved to release silicon species, which created an alkaline solution environment. The metakaolin then dissolved in the alkaline environment to generate aluminum species, which was followed by geopolymerization. The VT particles were connected by a gel produced during geopolymerization, which yielded a geopolymer with excellent mechanical performance. This investigation not only improves the feasibility of using geopolymer technology for large-scale and in-situ applications, but also promotes the utilization of VT and other silica-rich solid wastes.
Research Article
Process–structure–property relationship for plasma-sprayed iron-based amorphous/crystalline composite coatings
Abhishek Pathak, Biswajyoti Mukherjee, Krishna Kant Pandey, Aminul Islam, Pavan Bijalwan, Monojit Dutta, Atanu Banerjee, and Anup Kumar Keshri
  Available online 27 August 2020, https://doi.org/10.1007/s12613-020-2171-4
[FullText HTML](1729) [PDF 1162KB](56) SpringerLink
This study explores the fabrication of Fe-based amorphous/crystalline coating by air plasma spraying and its dependency on the coating parameters (plasma power, primary gas flow rate, powder feed rate, and stand-off distance). X-ray diffraction of the coatings deposited at optimized spray parameters showed the presence of amorphous/crystalline phase. Coatings deposited at a lower plasma power and highest gas flow rate exhibited better density, hardness, and wear resistance. All coatings demonstrated equally good resistance against the corrosive environment (3.5wt% NaCl solution). Mechanical, wear, and tribological studies indicated that a single process parameter optimization cannot provide good coating performance; instead, all process parameters have a unique role in defining better properties for the coating by controlling the in-flight particle temperature and velocity profile, followed by the cooling pattern of molten droplet before impingement on the substrate.
Research Article
U(VI) adsorption behavior onto polypyrrole coated 3R-MoS2 nanosheets prepared with the molten salt electrolysis method
Yuhui Liu, Meng Tang, Shuang Zhang, Yuling Lin, Yingcai Wang, Youqun Wang, Ying Dai, Xiaohong Cao, Zhibin Zhang, and Yunhai Liu
  Available online 30 July 2020, https://doi.org/10.1007/s12613-020-2154-5
[FullText HTML](1819) [PDF 2006KB](56) SpringerLink
To improve the separation capacity of uranium in aqueous solutions, 3R-MoS2 nanosheets were prepared with molten salt electrolysis and further modified with polypyrrole (PPy) to synthesize a hybrid nanoadsorbent (PPy/3R-MoS2). The preparation conditions of PPy/3R-MoS2 were investigated and the obtained nanosheets were characterized with scanning electron microscope (SEM), high resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS). The results showed that PPy/3R-MoS2 exhibited enhanced adsorption capacity toward U(VI) compared to pure 3R-MoS2 and PPy; the maximum adsorption was 200.4 mg/g. The adsorption mechanism was elucidated with XPS and FTIR: 1) negatively charged PPy/3R-MoS2 nanosheets attracted \begin{document}$ {\rm{UO}}_2^{2 + } $\end{document} by an electrostatic interaction; 2) exposed C, N, Mo, and S atoms complexed with U(VI) through coordination; 3) Mo in the complex partly reduced the adsorbed U(VI) to U(IV), which further regenerated the adsorption point and continuously adsorbed U(VI). The design of the PPy/3R-MoS2 composite with a high adsorption capacity and chemical stability provides a new direction for the removal of radionuclide.
Effect of 2-mercaptobenzothiazole concentration on sour-corrosion behavior of API X60 pipeline steel: Electrochemical parameters and adsorption mechanism
Masoud Sabzi, Amir Hayati Jozani, Farzad Zeidvandi, Majid Sadeghi, and Saeid Mersagh Dezfuli
  Available online 30 July 2020, https://doi.org/10.1007/s12613-020-2156-3
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We investigated the effect of‎the 2-mercaptobenzothiazole concentration on the sour-corrosion behavior of API ‎X60 pipeline steel in an environment containing H2S at 25°C and in the presence of 0, 2.5, 5.0, 7.5, and 10.0 g/L of ‎2-mercaptobenzothiazole inhibitor. To examine this behavior, we conducted open-circuit potential (OCP), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) tests. Energy dispersive spectroscopy and scanning electron microscopy were also used to analyze the corrosion products. The results of the OCP and potentiodynamic polarization tests revealed that ‎2-mercaptobenzothiazole reduces the speed of both the anodic and cathodic reactions. An assessment of the Gibbs free energy of the inhibitor (\begin{document}$ {\Delta G}_{\mathrm{a}\mathrm{d}\mathrm{s}}^{\ominus} $\end{document}) indicated that its value was less than −20 kJ·mol−1 and greater than −40 kJ·mol−1. Therefore, the adsorption of 2-mercaptobenzothiazole onto the surface of the API X60 pipeline steel occurs both physically and chemically, the latter of which is particularly intentional. In addition, as the \begin{document}$ {\Delta G}_{\mathrm{a}\mathrm{d}\mathrm{s}}^{\ominus} $\end{document} value was negative, we could conclude that the adsorption of 2-mercaptobenzothiazole onto the surface of the pipeline steel occurs spontaneously. The EIS results indicate that with the increase in the 2-mercaptobenzothiazole inhibitor concentration, the corrosion resistance of API X60 steel increases. An analysis of the corrosion products revealed that iron sulfide compounds form on the surface. In summary, the results showed that an increase in the inhibitor concentration results in a decrease in the corrosion rate and an increase in inhibitory efficiency. Additionally, we found that the 2-mercaptobenzothiazole adsorption process on the API X60 steel surfaces in an H2S-containing environment follows the Langmuir adsorption isotherm and occurs spontaneously.
Microstructure and phase elemental distribution in high-boron multi-component cast irons
Yu.G. Chabak, K. Shimizu, V.G. Efremenko, M.A. Golinskyi, K. Kusumoto, V.I. Zurnadzhy, and A.V. Efremenko
  Available online 9 July 2020, https://doi.org/10.1007/s12613-020-2135-8
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The novel cast irons of chemical composition (wt%) 0.7C–5W–5Mo–5V–10Cr–2.5Ti were invented with the additions of 1.6wt% B and 2.7wt% B. The aim of this work was to study the effect of boron on the structural state of the alloys and phase elemental distribution with respect to the formation of wear-resistant structural constituents. It was found that the alloy containing 1.6wt% B was composed of three eutectics: (a) “M2(C,B)5+ferrite” having a “Chinese Script” morphology (89.8vol%), (b) “M7(C,B)3+Austenite” having a “Rosette” morphology, and (c) “M3C+Austenite” having a “Ledeburite”-shaped morphology (2.7vol%). With 2.7wt% of boron content, the bulk hardness increased from HRC 31 to HRC 38.5. The primary carboborides M2(C,B)5 with average microhardness of HV 2797 appeared in the structure with a volume fraction of 17.6vol%. The volume fraction of eutectics (a) and (b, c) decreased to 71.2vol% and 3.9vol%, respectively. The matrix was “ferrite/austenite” for 1.6wt% B and “ferrite/pearlite” for 2.7wt% B. Both cast irons contained compact precipitates of carbide (Ti,M)C and carboboride (Ti,M)(C,В) with a volume fraction of 7.3–7.5. Based on the energy-dispersive X-ray spectroscopy, the elemental phase distributions and the appropriate phase formulas are presented in this work.
Research Article
Extraction of copper from copper-bearing biotite by ultrasonic-assisted leaching
Bao-qiang Yu, Jue Kou, Chun-bao Sun, and Yi Xing
  Available online 5 July 2020, https://doi.org/10.1007/s12613-020-2132-y
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Copper-bearing biotite is a refractory copper mineral found on the surface of the Zambian Copperbelt. Biotite is a copper oxide from which copper is extracted by various methods, especially by leaching. Leaching is the process of extracting a substance from a solid material dissolved in a liquid. To improve the efficiency of the leaching process by a more effective method, a new method called ultrasonic-assisted acid leaching is proposed and applied in this study. Compared with regular acid leaching, the ultrasound method reduced the leaching time from 120 to 40 min, and sulfuric acid concentration reduced from 0.5 to 0.3 mol·L−1. Besides, leaching temperature could be reduced from 75 to 45°C at the leaching rate of 78%. The mechanism analysis indicates that an ultrasonic wave can cause the delamination of a copper-bearing biotite and increase its specific surface area from 0.55 to 1.67 m2·g−1. The results indicate that copper extraction from copper-bearing biotite by ultrasonic-assisted acid leaching is more effective than regular acid leaching. This study proposes a promising method for recycling valuable metals from phyllosilicate minerals.
Synthesis and characterization of ceria nanoparticles by complex-precipitation route