International Journal of Minerals, Metallurgy and Materials

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Dimensioning a stockpile operation using principal component analysis

Siyi Li, Marco de Werk, Louis St-Pierre, Mustafa Kumral

2019, 26(12): 1485-1494. doi: 10.1007/s12613-019-1849-y

中文摘要(829) PDF(50) SpringerLink

摘要:
Mineral processing plants generally have narrow tolerances for the grades of their input raw materials, so stockpiles are often maintained to reduce material variance and ensure consistency. However, designing stockpiles has often proven difficult when the input material consists of multiple sub-materials that have different levels of variances in their grades. In this paper, we address this issue by applying principal component analysis (PCA) to reduce the dimensions of the input data. The study was conducted in three steps. First, we applied PCA to the input data to transform them into a lower-dimension space while retaining 80% of the original variance. Next, we simulated a stockpile operation with various geometric stockpile configurations using a stockpile simulator in MATLAB. We used the variance reduction ratio as the primary criterion for evaluating the efficiency of the stockpiles. Finally, we used multiple regression to identify the relationships between stockpile efficiency and various design parameters and analyzed the regression results based on the original input variables and principal components. The results showed that PCA is indeed useful in solving a stockpile design problem that involves multiple correlated input-material grades.

研究论文

Seaweed glue as a novel polymer depressant for the selective separation of chalcopyrite and galena

Xiong Chen, Guo-hua Gu, Zhi-xiang Chen

2019, 26(12): 1495-1503. doi: 10.1007/s12613-019-1848-z

中文摘要(687) PDF(26) SpringerLink

摘要:
The use of seaweed glue (SEG) as a novel polymer depressant for the separation of chalcopyrite from galena with butyl xanthate (BX) as a collector was studied through microflotation experiments. Contact angle, adsorption, dynamic potential, and infrared spectral analyses were conducted to clarify the mechanism underlying the action of SEG on minerals. The results of microflotation experiments indicated that chalcopyrite could be selectively separated from galena by using a SEG depressant concentration of 15 mg·L^-1, BX concentration of 10 mg·L^-1, and methyl isobutyl carbinol concentration of 8.5 mg·L^-1 at pH 8.0. A Cu concentrate with a grading of 23.68wt% was obtained at a recovery rate of 81.52% from mixed minerals with 8.29wt% Cu content. Contact angle analysis showed that the effect of SEG on the wettability of galena was stronger than that on the wettability of chalcopyrite. Adsorption, zeta potential, and FT-IR spectral analyses revealed that SEG and BX were coadsorbed on the surfaces of galena. SEG depressed galena by covering xanthate ions in the functional groups of -COO and mainly underwent weak physisorption on chalcopyrite. These mechanisms account for the ability of SEG to depress galena effectively while enabling chalcopyrite flotation.

研究论文

Relationship among the secretion of extracellular polymeric substances, heat resistance, and bioleaching ability of Metallosphaera sedula

Run-lan Yu, Zhen-hua Liu, Zhao-jing Yu, Xue-ling Wu, Li Shen, Yuan-dong Liu, Jiao-kun Li, Wen-qing Qin, Guan-zhou Qiu, Wei-min Zeng

2019, 26(12): 1504-1511. doi: 10.1007/s12613-019-1851-4

中文摘要(726) PDF(19) SpringerLink

摘要:
This paper describes the investigation of the secretion of extracellular polymeric substances (EPS) by an extremely thermoacidophilic archaea, Metallosphaera sedula (M. sedula), during the bioleaching of pyrite under different temperatures and discusses the relationship among the EPS secretion, its heat resistance, and its ability to bioleach pyrite. The investigation results indicate that the amount of extracellular proteins is significantly higher than the amount of extracellular polysaccharides in the extracted EPS whether free cells or attached cells; these results are quite different from the behavior of mesophilic Acidithiobacillus ferrooxidans. Although the growth of M. sedula is inhibited at 80℃, the bioleaching ability of M. sedula is only slightly lower than that at the optimum growth temperature of 72℃ because of the heat resistance mechanism based on EPS secretion. The secretion of more extracellular proteins is an important heat resistance mechanism of M. sedula.

研究论文

The mechanism and products for co-thermal extraction of biomass and low-rank coal with NMP

Jun Zhao, Hai-bin Zuo, Jing-song Wang, Qing-guo Xue

2019, 26(12): 1512-1522. doi: 10.1007/s12613-019-1872-z

中文摘要(860) PDF(19) SpringerLink

摘要:
The high-value utilization of low-rank coal would allow for expanding energy sources, improving energy efficiencies, and alleviating environmental issues. In order to use low-rank coal effectively, the hypercoals (HPCs) were co-extracted from two types of low-rank coal and biomass via N-methyl-2-purrolidinone (NMP) under mild conditions. The structures of the HPCs and residues were characterized by proximate and ultimate analysis, Raman spectra, and Fourier transform infrared (FT-IR) spectra. The carbon structure changes within the raw coals and HPCs were discussed. The individual thermal dissolution of Xibu (XB) coal, Guandi (GD) coal, and the biomass demonstrated that the biomass provided the lowest thermal dissolution yield Y₁ and the highest thermal soluble yield Y₂ at 280℃, and the ash content of three HPCs decreased as the extraction temperature rose. Co-thermal extractions in NMP at various coal/biomass mass ratios were performed, demonstrating a positive synergic effect for Y₂ in the whole coal/biomass mass ratios. The maximum value of Y₂ was 52.25wt% for XB coal obtained with a XB coal/biomass of 50wt% biomass. The maximum value of Y₂ was 50.77wt% for GD coal obtained with a GD coal/biomass of 1:4. The difference for the optimal coal/biomass mass ratios between XB and GD coals could be attributed to the different co-extraction mechanisms for this two type coals.

研究论文

Effect of surfactant on the dielectric and electrorheological properties of zinc borate/silicone oil dispersions

Omer Yunus Gumus, Halil Ibrahim Unal

2019, 26(12): 1523-1530. doi: 10.1007/s12613-019-1853-2

中文摘要(961) PDF(25) SpringerLink

摘要:
Zinc borate (ZB) particles dispersed in silicone oil (SO) at concentrations of φ=5vol%-20vol% were subjected to dielectric analysis to elucidate their polarization strength, time, and mechanism. Results revealed that all virgin dispersions lacked polarization. Triton X-100, a non-ionic surfactant, was added to ZB/SO dispersions to enhance the polarizability of ZB particles. The addition of 1vol% Triton X-100 enhanced the polarizability of ZB/SO dispersions, and the 15vol%ZB/SO system provided the highest dielectric difference Δε' (the difference in ε' values at zero and infinite frequency, Δε'=ε₀-ε_µ) of 3.64. The electrorheological (ER) activities of the ZB/SO/Triton-X dispersion system were determined through the ER response test, and viscoelastic behaviors were investigated via oscillation tests. A recoverable deformation of 36% under an applied electrical field strength of 1.5 kV/mm was detected through creep and creep recovery tests.

研究论文

Analysis of oxide layer structure in nitrided grain-oriented silicon steel

Xiao-long Wu, Xia Li, Ping Yang, Zhi-wei Jia, Hai-li Zhang

2019, 26(12): 1531-1538. doi: 10.1007/s12613-019-1850-5

中文摘要(896) PDF(41) SpringerLink

摘要:
The production of low-temperature reheated grain-oriented silicon steel is mainly based on the acquired inhibitor method. Due to the additional nitriding process, a high nitrogen content exists in the oxide layer, which changes the structure of the oxide layer. In this study, the structure of the surface oxide layer after nitriding was analyzed by scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD), glow discharge spectrometry (GDS), and X-ray diffraction (XRD). The size and orientation of ferritic grains in the oxide layer were characterized, and the distribution characteristics of the key elements along the thickness direction were determined. The results show that the oxide layer of the steel sample mainly comprised particles of Fe₂SiO₄ and spherical and lamellar SiO₂, and Fe₄N and fcc-Fe phases were also detected. Moreover, the size and orientation of ferritic grains in the oxide layer were different from those of coarse matrix ferritic grains beneath the oxide layer; however, some ferritic grains exhibited same orientations as those in the neighboring matrix. Higher nitrogen content was detected in the oxide layer than that in the matrix beneath the oxide layer. The form of nitrogen enrichment in the oxide layer was analyzed, and the growth mechanism of ferritic grains during the oxide layer formation is proposed.

研究论文

Experimental investigation of the cyclic degradation of the one-way shape memory effect of NiTi alloys

Tian-xing Zhao, Guo-zheng Kang, Chao Yu, Qian-hua Kan

2019, 26(12): 1539-1550. doi: 10.1007/s12613-019-1884-8

中文摘要(565) PDF(21) SpringerLink

摘要:
Based on stress- and strain-controlled cyclic tension-unloading-heat-cooling tests, cyclic degradation of the one-way shape memory effect (OWSME) of NiTi shape memory alloys (SMAs) was investigated. It was seen, in thermo-mechanical coupled cyclic tests, that residual strain after each cycle accumulated, but the martensite reorientation stress and dissipation energy-per-cycle decreased as the number of cycles increased. Meanwhile, the cyclic degradation of OWSME was aggravated by increasing the stress/strain amplitude. In addition, the stress-strain response of NiTi SMAs was further investigated by performing simultaneous thermo-mechanical coupled cyclic tests with various phase-angle differences between the mechanical and thermal cyclic loadings. It can be concluded that such cyclic response depends significantly on prescribed phase-angle differences. Obtained experimental results are helpful for both the development of constitutive models and engineering applications of NiTi SMAs.

研究论文

Effect of Cr content and cooling rate on the primary phase of Al-2.5Mn alloy

Hang-qi Feng, Zhi-bo Yang, Ye-tong Bai, Li Zhang, Yu-lin Liu

2019, 26(12): 1551-1558. doi: 10.1007/s12613-019-1862-1

中文摘要(662) PDF(20) SpringerLink

摘要:
The effect of Cr content and cooling rate on the microstructure of Al-Mn alloy was studied using well resistance furnace melting, and the alloy was analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The experimental results showed that adding Cr could significantly improve the morphology of the primary phase in the Al-2.5Mn alloy. Without Cr, the primary phase in the alloy was thick, needle-like, and strip-like structure. After adding 0.2wt%-0.5wt% Cr, the primary phase in the upper part of the alloy was gradually fined and reached the best effect at 0.35wt% Cr. When the content of Cr was 0.5wt%, the microstructure of the primary phase in the upper part began to coarsen. The bottom of the alloy was a large bulk phase, but still much finer than that without adding Cr. XRD and SEM analysis showed that the precipitation phase at the bottom was mainly Al₈₅Mn₇Cr₈, while the fine microstructure at the top was Al₆Mn and Al₃Mn. The results of the cooling rate experiments showed that the primary phase of Al-2.5Mn-0.35Cr was further refined, and the eutectic microstructure was partly achieved, under air-cooling condition. And when the cooling method was iron die-cooling, the microstructure of the Al-2.5Mn-0.35Cr alloy was changed into a eutectic microstructure.

研究论文

Effects of Sc and Zr microalloying on the microstructure and mechanical properties of high Cu content 7xxx Al alloy

Chong-yu Liu, Guang-biao Teng, Zong-yi Ma, Li-li Wei, Bing Zhang, Yong Chen

2019, 26(12): 1559-1569. doi: 10.1007/s12613-019-1840-7

中文摘要(841) PDF(31) SpringerLink

摘要:
The effects of Sc and Zr microalloying on the microstructure and mechanical properties of a 7xxx Al alloy with high Cu content (7055) during casting, deformation, and heat treatment were investigated. The addition of Sc and Zr not only refined the grains but also transformed the θ-phase into the W-phase in the 7055 alloy. Minor Sc and Zr additions enhanced the hardness and yield strength of the 7055-T6 alloy by strengthening the grain boundaries and Al₃(Sc,Zr) precipitates. However, a further increase in the Sc and Zr fractions did not refine the grains but instead resulted in the formation of the large-sized W-phase and primary coarse Al₃(Sc,Zr) phase and subsequently deteriorated the mechanical properties of the alloys. The 7055 alloy with 0.25Sc addition exhibited the best mechanical property among the prepared alloys.

研究论文

Ordering and disordering of in situ grown MgAl-layered double hydroxide and its effect on the structural and corrosion resistance properties

Muhammad Ahsan Iqbal, Michele Fedel

2019, 26(12): 1570-1577. doi: 10.1007/s12613-019-1844-3

中文摘要(800) PDF(18) SpringerLink

摘要:
A MgAl-layered double hydroxide (MgAl-LDH) protective film was developed on AA6082 substrates via the in situ hydrothermal growth method to obtain a distinct cauliflower-like LDH structure, and coated substrates were further heat-treated in air at temperatures from 100 to 250℃ to further improve the corrosion resistance of MgAl-LDH by taking advantage of the LDH memory effect; also, the effect of calcination on MgAl-LDH structural stability and the corresponding corrosion resistance properties were investigated. The structural characterization of uncalcined and calcined LDH films were examined using scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, and Fourier transform infrared spectroscopy. The corresponding corrosion protection efficiency of the developed coating was studied through potentiodynamic polarization experiments and by electrochemical impedance spectroscopy. Compared with uncalcined MgAl-LDH, the calcined film showed a relatively lower corrosion current density and a higher impedance value, especially after heat treatment at 250℃. The findings demonstrate that calcination strongly affects the oriented growth of the LDH and causes an increase in the surface area and contraction of the basal spacing, which in turn caused a compact structure that substantially influenced the LDH corrosion resistance properties.

研究论文

On the liquid-phase technology of carbon fiber/aluminum matrix composites

Sergei Galyshev, Andrew Gomzin, Rida Gallyamova, Igor Khodos, Fanil Musin

2019, 26(12): 1578-1584. doi: 10.1007/s12613-019-1877-7

中文摘要(722) PDF(19) SpringerLink

摘要:
The main problems with the liquid-phase technology of carbon fiber/aluminum matrix composites include poor wetting of the fiber with liquid aluminum and formation of aluminum carbide on the fibers' surface. This paper aims to solve these problems. The theoretical and experimental dependence of porosity on the applied pressure were determined. The possibility of obtaining a carbon fiber/aluminum matrix composite wire with a strength value of about 1500 MPa was shown. The correlation among the strength of the carbon fiber reinforced aluminum matrix composite, the fracture surface, and the degradation of the carbon fiber surface was discussed.

研究论文

Reliability evaluation of hardness test methods of hardfacing coatings with hypoeutectic and hypereutectic microstructures

Nilay Çömez, Can Çivi, Hülya Durmuş

2019, 26(12): 1585-1593. doi: 10.1007/s12613-019-1866-x

中文摘要(3204) PDF(26) SpringerLink

摘要:
Hardfacing coatings involve hard carbide/boride phases dispersed in a relatively soft steel matrix. For the hardness measurements of hardfacing coatings, depending on the microstructure, both the hardness test method and the applied load affect the hardness results; therefore, they affect the wear performance predictions of the coating. For this reason, the proper hardness test method should be determined according to the microstructure of the coating, and the reliability of the obtained hardness data should be established. This study aimed to determine the most suitable hardness test method for hypoeutectic and hypereutectic microstructures of hardfacing coatings by analyzing the reliability of Rockwell-C and Vickers hardness test results. Reliability analyses showed that Rockwell-C is not a suitable hardness test method for hypereutectic hardfacing coatings. Based on the relationship between wear resistance and hardness, Vickers hardness method was found more suitable for the considered materials.

研究论文

Cementitious property of NaAlO₂-activated Ge slag as cement supplement

Hua-zhe Jiao, Shu-fei Wang, Ai-xiang Wu, Hui-ming Shen, Jian-dong Wang

2019, 26(12): 1594-1603. doi: 10.1007/s12613-019-1901-y

中文摘要(800) PDF(33) SpringerLink

摘要:
Germanium (Ge), a waste residue leaching from zinc (Zn) smelting process, has potential cementitious properties and could be recycled as a cement supplement activated by chemical reagents. In this work, a test was conducted to determine the hydration properties of Ge slag-cement-based composites with Ge slag (GS)/ordinary Portland cement (PC) contents of 0wt%, 5wt%, 10wt%, 15wt%, 20wt%, and 25wt% and water-to-binder ratio (w/b) of 0.4. The activators Ca(OH)₂, AlCl₃, NaAlO₂, and Na₂CO₃ were mixed under 1wt%, 2wt%, 3wt%, and 4wt% dosages of GS weight. The composition and microstructure of the hydration products were investigated by the combined approaches of X-ray diffraction (XRD), thermogravimetry-differential scanning calorimetry (TG-DSC), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). First, the GS cementitious property is attributed to the high content of CaSO₄·2H₂O. Second, the activators affected the acceleration performance in the following order:NaAlO₂, Na₂CO₃, AlCl₃, and Ca(OH)₂. More importantly, the 28-day unconfined compressive strength (UCS) is 45.34 MPa at the optimum formula of 0.6wt% NaAlO₂, 15wt% GS, and 85wt% PC, which is 9.16% higher than the control. Thus, NaAlO₂ is beneficial for the ettringite (AFt) generation, resulting in the C-S-H structure compaction. However, the Zn²⁺ residue inhibited the AFt formation, representing an important challenge to the strength growth with curing age. Consequently, the GS could be recycled as a supplement to the cement under the activator NaAlO₂.

研究论文

Corrosion mechanism of magnesia-chromite refractories by ZnO-containing fayalite slags: Effect of funnel glass addition

Zhe-nan Jin, Jian-fang Lü, Hong-ying Yang, Zhi-yuan Ma

2019, 26(12): 1604-1616. doi: 10.1007/s12613-019-1912-8

中文摘要(956) PDF(30) SpringerLink

摘要:
An efficient approach for lead extraction from waste funnel glass through the lead smelting process has been proposed. To clarify the effect of funnel glass addition on the degradation of magnesia-chromite refractories by ZnO-containing fayalite slag, the corrosion behavior of magnesia-chromite refractories in lead smelting slags with different funnel glass additions from 0wt% to 40wt% was tested. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) was used to acquire the microstructural information of the worn refractory samples. Experimental results showed that the corrosion of magnesia-chromite refractory consisted predominantly of the dissolution of MgO into slag. ZnO and FeO reacted with periclase and chromite to form (Zn,Fe,Mg)O solid solution and (Zn,Fe,Mg)(Fe,Al,Cr)₂O₄ spinel, respectively. With the addition of funnel glass, the solubility of MgO increased whereas ZnO levels remained stable, thereby resulting in a reduced Mg content and an elevated Zn and Fe content in the (Zn,Fe,Mg)O solid solution and the (Zn,Fe,Mg)(Fe,Al,Cr)₂O₄ spinel. Considering the stability of the (Zn,Fe,Mg)O solid solution layer and the penetration depth of the slag, the optimal funnel glass addition for lead smelting was found to be 20wt%.

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2019年第26卷第12期