International Journal of Minerals, Metallurgy and Materials

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Reductive leaching of manganese from low-grade pyrolusite ore in sulfuric acid using pyrolysis-pretreated sawdust as a reductant

Ya-li Feng, Shi-yuan Zhang, Hao-ran Li

2016, 23(3): 241-246. doi: 10.1007/s12613-016-1232-1

中文摘要(546) PDF(49) SpringerLink

摘要:
Manganese (Mn) leaching and recovery from low-grade pyrolusite ore were studied using sulfuric acid (H₂SO₄) as a leachant and pyrolysis-pretreated sawdust as a reductant. The effects of the dosage of pyrolysis-pretreated sawdust to pyrolusite ore, the concentration of sulfuric acid, the liquid/solid ratio, the leaching temperature, and the leaching time on manganese and iron leaching efficiencies were investigated. Analysis of manganese and iron leaching efficiencies revealed that a high manganese leaching efficiency was achieved with low iron extraction. The optimal leaching efficiency was determined to be 20wt% pyrolysis-pretreated sawdust and 3.0 mol/L H₂SO₄ using a liquid/ solid ratio of 6.0 mL/g for 90 min at 90℃. Other low-grade pyrolusite ores were tested, and the results showed that they responded well with manganese leaching efficiencies greater than 98%.

Innovative method for boron extraction from iron ore containing boron

Guang Wang, Jing-song Wang, Xin-yun Yu, Ying-feng Shen, Hai-bin Zuo, Qing-guo Xue

2016, 23(3): 247-256. doi: 10.1007/s12613-016-1233-0

中文摘要(356) PDF(27) SpringerLink

摘要:
A novel process for boron enrichment and extraction from ludwigite based on iron nugget technology was proposed. The key steps of this novel process, which include boron and iron separation, crystallization of boron-rich slag, and elucidation of the boron extraction behavior of boron-rich slag by acid leaching, were performed at the laboratory. The results indicated that 95.7% of the total boron could be enriched into the slag phase, thereby forming a boron-rich slag during the iron and slag melting separation process. Suanite and kotoite were observed to be the boron-containing crystalline phases, and the boron extraction properties of the boron-rich slag depended on the amounts and grain sizes of these minerals. When the boron-rich slag was slowly cooled to 1100℃, the slag crystallized well and the efficiency of extraction of boron (EEB) of the slag was the highest observed in the present study. The boron extraction property of the slow-cooled boron-rich slag obtained in this study was much better than that of szaibelyite ore under the conditions of 80% of theoretical sulfuric acid amount, leaching time of 30 min, leaching temperature of 40℃, and liquid-to-solid ratio of 8 mL/g.

Recovery of alkali and alumina from Bayer red mud by the calcification–carbonation method

Xiao-feng Zhu, Ting-an Zhang, Yan-xiu Wang, Guo-zhi Lü, Wei-guang Zhang

2016, 23(3): 257-268. doi: 10.1007/s12613-016-1234-z

中文摘要(458) PDF(45) SpringerLink

摘要:
Red mud produced in the Bayer process is a hazardous solid waste because of its high alkalinity; however, it is rich in valuable components such as titanium, iron, and aluminum. In this study, a novel calcification–carbonation method was developed to recover alkali and alumina from Bayer red mud under mild reaction conditions. Batch experiments were performed to evaluate the potential effects of important parameters such as temperature, amount of CaO added, and CO₂ partial pressure on the recovery of alkali and alumina. The results showed that 95.2% alkali and 75.0% alumina were recovered from red mud with decreases in the mass ratios of Na₂O to Fe₂O₃ and of Al₂O₃ to Fe₂O₃ from 0.42 and 0.89 to 0.02 and 0.22, respectively. The processed red mud with less than 0.5wt% Na₂O can potentially be used as a construction material.

Effect of slag composition on the cleanliness of 28MnCr5 gear steel in the refining processes

Wen-liang Dong, Hong-wei Ni, Hua Zhang, Ze-an Lü

2016, 23(3): 269-275. doi: 10.1007/s12613-016-1235-y

中文摘要(277) PDF(12) SpringerLink

摘要:
The equilibrium reaction between CaO—Al₂O₃—SiO₂—MgO slag and 28MnCr5 molten steel was calculated to obtain the suitable slag composition which is effective for decreasing the oxygen content in molten steel. The dissolved oxygen content [O] in molten steel under different top slag conditions was calculated using a thermodynamic model and was measured using an electromotive force method in slag–steel equilibrium experiments at 1873 K. The relations among [O], the total oxygen content (T.O), and the composition of the slag were investigated. The experimental results show that both [O] and T.O decrease with decreasing SiO₂ content of the slag and exhibit different trends with the changes in the CaO/Al₂O₃ mass ratio of the slag. Increasing the CaO/Al₂O₃ mass ratio results in a decrease in [O] and an increase in T.O. To ensure that T.O ≤ 20 ppm and [O] ≤ 10 ppm, the SiO₂ content should be controlled to <5wt%, and the CaO/Al₂O₃ mass ratio should be in the range from 1.2 to 1.6.

Superior machinability of steel enhanced with BN and MnS particles

Ya-nan Chen, Yan-ping Bao, Min Wang, Xiao-feng Cai, Lin-jing Wang, Li-hua Zhao

2016, 23(3): 276-282. doi: 10.1007/s12613-016-1236-x

中文摘要(321) PDF(12) SpringerLink

摘要:
The strategy that replacing part of MnS with BN was proposed in order to decrease the sulfur content in sulfur based free-cutting steel. The effects of BN and MnS inclusions on the microstructure and machinability of the steel were systematically investigated. The results show that most of the BN and MnS inclusions exist individually in the steel and only a small amount of them are in a composite state forming either isolated particles or clusters of particles. In the case of multi-phased steel, the theoretical calculation predicts that the volume of large BN particles should be 0.7 times of the volume of large MnS particles. The machinability of this type of BN and MnS alloy steel over a wide range of cutting speeds ranging from a low speed appropriate for drilling to a high speed appropriate for turning is confirmed as being equal to or superior to that of an MnS reference steel, even though the sulfur content in the composite steel is only half that of the MnS steel. The aptitude for cutting effect of 240 ppm nitrogen and 115 ppm boron in the composite steel is demonstrated to be equivalent or even better than 1000 ppm sulfur in MnS free-cutting steel.

Coarsening behavior of MX carbonitrides in type 347H heat-resistant austenitic steel during thermal aging

Ying-hui Zhou, Chen-xi Liu, Yong-chang Liu, Qian-ying Guo, Hui-jun Li

2016, 23(3): 283-293. doi: 10.1007/s12613-016-1237-9

中文摘要(259) PDF(18) SpringerLink

摘要:
In this work, the growth kinetics of MX (M = metal, X = C/N) nanoprecipitates in type 347H austenitic steel was systematically studied. To investigate the coarsening behavior and the growth mechanism of MX carbonitrides during long-term aging, experiments were performed at 700, 800, 850, and 900℃ for different periods (1, 24, 70, and 100 h). The precipitation behavior of carbonitrides in specimens subjected to various aging conditions was explored using carbon replicas and transmission electron microscopy (TEM) observations. The corresponding sizes of MX carbonitrides were measured. The results demonstrates that MX carbonitrides precipitate in type 347H austenitic steel as Nb(C,N). The coarsening rate constant is time-independent; however, an increase in aging temperature results in an increase in coarsening rate of Nb(C,N). The coarsening process was analyzed according to the calculated diffusion activation energy of Nb(C,N). When the aging temperature was 800–900℃, the mean activation energy was 294 kJ·mol^-1, and the coarsening behavior was controlled primarily by the diffusion of Nb atoms.

Microstructure simulation of rapidly solidified ASP30 high-speed steel particles by gas atomization

Jie Ma, Bo Wang, Zhi-liang Yang, Guang-xin Wu, Jie-yu Zhang, Shun-li Zhao

2016, 23(3): 294-302. doi: 10.1007/s12613-016-1238-8

中文摘要(286) PDF(10) SpringerLink

摘要:
In this study, the microstructure evolution of rapidly solidified ASP30 high-speed steel particles was predicted using a simulation method based on the cellular automaton-finite element (CAFE) model. The dendritic growth kinetics, in view of the characteristics of ASP30 steel, were calculated and combined with macro heat transfer calculations by user-defined functions (UDFs) to simulate the microstructure of gas-atomized particles. The relationship among particle diameter, undercooling, and the convection heat transfer coefficient was also investigated to provide cooling conditions for simulations. The simulated results indicated that a columnar grain microstructure was observed in small particles, whereas an equiaxed microstructure was observed in large particles. In addition, the morphologies and microstructures of gas-atomized ASP30 steel particles were also investigated experimentally using scanning electron microscopy (SEM). The experimental results showed that four major types of microstructures were formed: dendritic, equiaxed, mixed, and multi-droplet microstructures. The simulated results and the available experimental data are in good agreement.

Effect of lower bainite/martensite/retained austenite triplex microstructure on the mechanical properties of a low-carbon steel with quenching and partitioning process

Wan-song Li, Hong-ye Gao, Zhong-yi Li, Hideharu Nakashima, Satoshi Hata, Wen-huai Tian

2016, 23(3): 303-313. doi: 10.1007/s12613-016-1239-7

中文摘要(333) PDF(11) SpringerLink

摘要:
We present a study concerning Fe–0.176C–1.31Si–1.58Mn–0.26Al–0.3Cr (wt%) steel subjected to a quenching and partitioning (Q&P) process. The results of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and tensile tests demonstrate that the microstructures primarily consist of lath martensite, retained austenite, lower bainite (LB), and a small amount of tempered martensite; moreover, few twin austenite grains were observed. In the microstructure, three types of retained austenite with different sizes and morphologies were observed: blocky retained austenite (~300 nm in width), film-like retained austenite (80–120 nm in width), and ultra- fine film-like retained austenite (30–40 nm in width). Because of the effect of the retained austenite/martensite/LB triplex microstructure, the specimens prepared using different quenching temperatures exhibit high ultimate tensile strength and yield strength. Furthermore, the strength effect of LB can partially counteract the decreasing strength effect of martensite. The formation of LB substantially reduces the amount of retained austenite. Analyses of the retained austenite and the amount of blocky retained austenite indicated that the carbon content is critical to the total elongation of Q&P steel.

Microstructural evolution and mechanical properties of an Fe–18Ni–16Cr–4Al base alloy during aging at 950℃

Man Wang, Yong-duo Sun, Jing-kai Feng, Rui-qian Zhang, Rui Tang, Zhang-jian Zhou

2016, 23(3): 314-322. doi: 10.1007/s12613-016-1240-1

中文摘要(226) PDF(7) SpringerLink

摘要:
The development of Gen-IV nuclear systems and ultra-supercritical power plants proposes greater demands on structural materials used for key components. An Fe–18Ni–16Cr–4Al (316-base) alumina-forming austenitic steel was developed in our laboratory. Its microstructural evolution and mechanical properties during aging at 950℃ were investigated subsequently. Micro-structural changes were characterized by scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy. Needle-shaped NiAl particles begin to precipitate in austenite after ageing for 10 h, whereas round NiAl particles in ferrite are coarsened during aging. Precipitates of NiAl with different shapes in different matrices result from differences in lattice misfits. The tensile plasticity increases by 32.4% after aging because of the improvement in the percentage of coincidence site lattice grain boundaries, whereas the tensile strength remains relatively high at approximately 790 MPa.

Kinetics of discontinuous precipitation in Cu–20Ni–20Mn alloy

Wei-bin Xie, Qiang-song Wang, Guo-liang Xie, Xu-jun Mi, Dong-mei Liu, Xue-Cheng Gao

2016, 23(3): 323-329. doi: 10.1007/s12613-016-1241-0

中文摘要(289) PDF(12) SpringerLink

摘要:
The morphology and growth kinetics of discontinuous precipitation (DP) in a Cu–20Ni–20Mn alloy were investigated in the temperature range of 523–673 K by optical microscopy, scanning electron microscopy, and transmission electron microscopy. A lamellar mixed structure consisting of alternating lamellae of a matrix and NiMn phase was observed in DP colonies. The volume fraction of regions formed by a DP reaction was determined by quantitative metallographic measurements. The kinetics of DP was evaluated on the basis of the Johnson–Mehl–Avrami–Kolmogorov equation, which resulted in a time exponent of approximately 1.5. We confirmed that the nucleation of the discontinuous precipitate was confined to grain edges or boundaries at an early stage of the reaction. The activation energy of DP process was determined to be approximately (72.7 ±7.2) kJ/mol based on the Arrhenius equation; this result suggests that DP is controlled by grain boundary diffusion. The hardness values exhibited good correlation with the volume fraction of DP; this correlation was attributed to the presence of the ordered NiMn phase.

Preparation of CNT/AlSi10Mg composite powders by high-energy ball milling and their physical properties

Lin-zhi Wang, Ying Liu, Wen-hou Wei, Xu-guang An, Tao Zhang, Ya-yun Pu

2016, 23(3): 330-338. doi: 10.1007/s12613-016-1242-z

中文摘要(223) PDF(10) SpringerLink

摘要:
This study investigated the effects of carbon nanotube (CNT) concentration on the micro-morphologies and laser absorption properties of CNT/AlSi10Mg composite powders produced by high-energy ball milling. A scanning electron microscope, X-ray diffractometer, laser particle size analyzer, high-temperature synchronous thermal analyzer, and UV/VIS/NIR spectrophotometer were used for the analysis of micrographs, phases, granulometric parameters, thermal properties, and laser absorption properties of the composite powders, respectively. The results showed that the powders gradually changed from flake- to granule-like morphology and the average particle size sharply decreased with increases in milling rotational speed and milling time. Moreover, a uniform dispersion of CNTs in AlSi10Mg powders was achieved only for a CNT content of 1.5wt%. Laser absorption values of the composite powders were also observed to gradually increase with the increase of CNT concentration, and different spectra displayed characteristic absorption peaks at a wavelength of approximately 826 nm.

Thermodynamic study and methanothermal temperature-programmed reaction synthesis of molybdenum carbide

Parham Roohi, Reza Alizadeh, Esmaeil Fatehifar

2016, 23(3): 339-347. doi: 10.1007/s12613-016-1243-y

中文摘要(269) PDF(10) SpringerLink

摘要:
Nanostructured molybdenum carbide (Mo₂C) was successfully prepared from molybdenum trioxide (MoO₃) using methanothermal temperature-programmed reaction. Thermodynamic analysis indicated that in presence of methane, the formation of Mo₂C from MoO₃ occurs through the path of MoO₃ → MoO₂ → Mo₂C. The carburized MoO₃ was characterized using X-ray diffraction (XRD), CHNS/O analysis, Brunauer–Emmett–Teller (BET) analysis, and field-emission scanning electron microscopy (FESEM). At final carburization temperatures of 700 and 800℃ and at methane contents ranging from 5vol% to 20vol%, Mo₂C was the only solid product observed in the XRD patterns. The results indicated that the effect of methane content on the formation of the carbide phase is substantial compared with the effect of carburization time. Elemental analysis showed that at a final temperature of 700℃, the carbon content of carburized MoO₃ is very close to the theoretical carbon mass percentage in Mo₂C. At higher carburization temperatures, excess carbon was deposited onto the surface of Mo₂C. High-surface-area Mo₂C was obtained at extremely low heating rates; this high-surface-area material is a potential electrocatalyst.

Influence of growth conditions on the electrochemical synthesis of SnS thin films and their optical properties

Hosein Kafashan, Farid Jamali-Sheini, Reza Ebrahimi-Kahrizsangi, Ramin Yousefi

2016, 23(3): 348-357. doi: 10.1007/s12613-016-1244-x

中文摘要(518) PDF(15) SpringerLink

摘要:
Tin sulfide (SnS) thin films were prepared by electrodeposition onto fluorine-doped tin oxide (FTO) glass substrates using an aqueous solution containing SnCl₂ and Na₂S₂O₃ at various deposition potentials (E) and bath concentrations. The pH value and temperature of the solution were kept constant. The deposited films were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), photoluminescence (PL), and ultraviolet–visible (UV–Vis) spectroscopy. The FESEM images demonstrated that changes in the deposition potential (E) and solution concentration led to marked changes in the morphology of the deposited SnS films. Energy-dispersive X-ray analysis (EDXA) results showed that the Sn/S atomic ratio strongly depended on both the solution concentration and the deposition potential. To obtain an Sn/S atomic ratio approximately equal to 1, the optimal Sn²⁺/S₂O₃^2- molar ratio and E parameter were 1/8 and -1.0 V, respectively. The XRD patterns showed that the synthesized SnS was obviously polycrystalline, with an orthorhombic structure. The effects of the variations of bath concentration and deposition potential on the band-gap energy (E_g) were studied using PL and UV–Vis experiments. The PL spectra of all the SnS films contained two peaks in the visible region and one peak in the infrared (IR) region. The UV–Vis spectra showed that the optical band-gap energy varies from 1.21 to 1.44 eV.

Enhanced photocatalytic activity of electrochemically synthesized aluminum oxide nanoparticles

Deepak Pathania, Rishu Katwal, Harpreet Kaur

2016, 23(3): 358-371. doi: 10.1007/s12613-016-1245-9

中文摘要(283) PDF(21) SpringerLink

摘要:
In this study, aluminum oxide (Al₂O₃) nanoparticles (NPs) were synthesized via an electrochemical method. The effects of reaction parameters such as supporting electrolytes, solvent, current and electrolysis time on the shape and size of the resulting NPs were investigated. The Al₂O₃ NPs were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, thermogravimetric analysis/differential thermal analysis, energy-dispersive X-ray analysis, and ultraviolet–visible spectroscopy. Moreover, the Al₂O₃ NPs were explored for photocatalytic degradation of malachite green (MG) dye under sunlight irradiation via two processes: adsorption followed by photocatalysis; coupled adsorption and photocatalysis. The coupled process exhibited a higher photodegradation efficiency (45%) compared to adsorption followed by photocatalysis (32%). The obtained kinetic data was well fitted using a pseudo-first-order model for MG degradation.

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2016年第23卷第3期

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2016年第23卷第3期