International Journal of Minerals, Metallurgy and Materials

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Bioleaching of chalcopyrite and bornite by moderately thermophilic bacteria: an emphasis on their interactions

Hong-bo Zhao, Jun Wang, Xiao-wen Gan, Wen-qing Qin, Ming-hao Hu, Guan-zhou Qiu

2015, 22(8): 777-787. doi: 10.1007/s12613-015-1134-7

中文摘要(268) PDF(8) SpringerLink

摘要:
Interactions between chalcopyrite and bornite during bioleaching by moderately thermophilic bacteria were investigated mainly by X-ray diffraction, scanning electron microscopy, and electrochemical measurements performed in conjunction with bioleaching experiments. The results showed that a synergistic effect existed between chalcopyrite and bornite during bioleaching by both Acidithiobacillus caldus and Leptospirillum ferriphilum and that extremely high copper extraction could be achieved when chalcopyrite and bornite coexisted in a bioleaching system. Bornite dissolved preferentially because of its lower corrosion potential, and its dissolution was accelerated by the galvanic current during the initial stage of bioleaching. The galvanic current and optimum redox potential of 390-480 mV vs. Ag/AgCl promoted the reduction of chalcopyrite to chalcocite (Cu₂S), thus accelerating its dissolution.

New pyrometallurgical process of EAF dust treatment with CaO addition

Romchat Chairaksa-Fujimoto, Yosuke Inoue, Naoyoshi Umeda, Satoshi Itoh, Tetsuya Nagasaka

2015, 22(8): 788-797. doi: 10.1007/s12613-015-1135-6

中文摘要(435) PDF(27) SpringerLink

摘要:
The non-carbothermic zinc pyrometallurgical processing of electric arc furnace (EAF) dust was investigated on a laboratory scale. The main objective of this process was to convert highly stable zinc ferrite (ZnFe₂O₄), which accounts for more than half of total zinc in the EAF dust, into ZnO and Ca₂Fe₂O₅ by CaO addition. The EAF dust was mixed with CaO powder in various ratios, pressed into pellets, and heated in a muffle furnace in air at temperatures ranging from 700 to 1100℃ for a predetermined holding time. All ZnFe₂O₄ was transformed into ZnO and Ca₂Fe₂O₅ at a minimum temperature of 900℃ within 1 h when sufficient CaO to achieve a Ca/Fe molar ratio of 1.1 was added. However, at higher temperatures, excess CaO beyond the stoichiometric ratio was required because it was consumed by reactions leading to the formation of compounds other than ZnFe₂O₄. The evaporation of halides and heavy metals in the EAF dust was also studied. These components could be preferentially volatilized into the gas phase at 1100℃ when CaO was added.

Reductive smelting of spent lead–acid battery colloid sludge in a molten Na₂CO₃ salt

Yu-jie Hu, Chao-bo Tang, Mo-tang Tang, Yong-ming Chen

2015, 22(8): 798-803. doi: 10.1007/s12613-015-1136-5

中文摘要(298) PDF(13) SpringerLink

摘要:
Lead extraction from spent lead–acid battery paste in a molten Na₂CO₃ salt containing ZnO as a sulfur-fixing agent was studied. Some influencing factors, including smelting temperature, reaction time, ZnO and salt dosages, were investigated in detail using single-factor experiments. The optimum conditions were determined as follows: T = 880℃; t = 60 min; Na₂CO₃/paste mass ratio = 2.8:1; and the ZnO dosage is equal to the stoichiometric requirement. Under the optimum conditions, the direct recovery rate of lead reached 98.14%. The results suggested that increases in temperature and salt dosage improved the direct recovery rate of lead. XRD results and thermodynamic calculations indicated that the reaction approaches of lead and sulfur were PbSO₄→Pb and PbSO₄→ZnS, respectively. Sulfur was fixed in the form of ZnS, whereas the molten salt did not react with other components, serving only as a reaction medium.

Rheological behavior and constitutive equations of heterogeneous titanium-bearing molten slag

Tao Jiang, De-ming Liao, Mi Zhou, Qiao-yi Zhang, Hong-rui Yue, Song-tao Yang, Pei-ning Duan, Xiang-xin Xue

2015, 22(8): 804-810. doi: 10.1007/s12613-015-1137-4

中文摘要(299) PDF(11) SpringerLink

摘要:
Experimental studies on the rheological properties of a CaO–SiO₂–Al₂O₃–MgO–TiO₂–(TiC) blast furnace (BF) slag system were conducted using a high-temperature rheometer to reveal the non-Newtonian behavior of heterogeneous titanium-bearing molten slag. By measuring the relationships among the viscosity, the shear stress and the shear rate of molten slags with different TiC contents at different temperatures, the rheological constitutive equations were established along with the rheological parameters; in addition, the non-Newtonian fluid types of the molten slags were determined. The results indicated that, with increasing TiC content, the viscosity of the molten slag tended to increase. If the TiC content was less than 2wt%, the molten slag exhibited the Newtonian fluid behavior when the temperature was higher than the critical viscosity temperature of the molten slag. In contrast, the molten slag exhibited the non-Newtonian pseudoplastic fluid characteristic and the shear thinning behavior when the temperature was less than the critical viscosity temperature. However, if the TiC content exceeded 4wt%, the molten slag produced the yield stress and exhibited the Bingham and plastic pseudoplastic fluid behaviors when the temperature was higher and lower than the critical viscosity temperature, respectively. When the TiC content increased further, the yield stress of the molten slag increased and the shear thinning phenomenon became more obvious.

Influence of FeO and sulfur on solid state reaction between MnO-SiO₂-FeO oxides and an Fe-Mn-Si solid alloy during heat treatment at 1473 K

Cheng-song Liu, Shu-feng Yang, Kyung-ho Kim, Jing-she Li, Hiroyuki Shibata, Shin-ya Kitamura

2015, 22(8): 811-819. doi: 10.1007/s12613-015-1138-3

中文摘要(317) PDF(8) SpringerLink

摘要:
To clarify the influence of FeO and sulfur on solid state reaction between an Fe-Mn-Si alloy and MnO-SiO₂-FeO oxides under the restricted oxygen diffusion flux, two diffusion couples with different sulfur contents in the oxides were produced and investigated after heat treatment at 1473 K. The experimental results were also compared with previous work in which the oxides contained higher FeO. It was found that although the FeO content in the oxides decreased from 3wt% to 1wt% which was lower than the content corresponding to the equilibrium with molten steel at 1873 K, excess oxygen still diffused from the oxides to solid steel during heat treatment at 1473 K and formed oxide particles. In addition, increasing the sulfur content in the oxides was observed to suppress the diffusion of oxygen between the alloy and the oxides.

Effects of H content on the tensile properties and fracture behavior of SA508-III steel

Jia-hua Liu, Lei Wang, Yang Liu, Xiu Song, Jiong Luo, Dan Yuan

2015, 22(8): 820-828. doi: 10.1007/s12613-015-1139-2

中文摘要(262) PDF(8) SpringerLink

摘要:
SA508-Ⅲ steel was charged with different hydrogen (H) contents using a high-pressure thermal charging method to study the effects of H content on the tensile properties and evaluate the H embrittlement behavior of the steel. The results indicate that the ultimate tensile strength remains nearly unchanged with the addition of H. In contrast, the yielding strength slightly increases, and the elongation significantly decreases with increasing H content, especially at concentrations exceeding 5.6×10^-6. On the basis of fractographic analysis, it is clear that the addition of H changes the fracture mode from microvoid coalescence to a mixture of river patterns and dimples. Carbides are strong traps for H; thus, the H atoms easily migrate in the form of Cottrell atmosphere toward the carbides following moving dislocations during tensile deformation. In addition, stress-induced H atoms accumulate at the interface between carbides and the matrix after necking under three-dimensional stress, which weakens the interfacial bonding force. Consequently, when the local H concentration reaches a critical value, microcracks occur at the interface, resulting in fracture.

Influence of chromium on the initial corrosion behavior of low alloy steels in the CO₂–O₂–H₂S–SO₂ wet–dry corrosion environment of cargo oil tankers

Qing-he Zhao, Wei Liu, Jie Zhao, Dong Zhang, Peng-cheng Liu, Min-xu Lu

2015, 22(8): 829-841. doi: 10.1007/s12613-015-1140-9

中文摘要(275) PDF(8) SpringerLink

摘要:
The influence of Cr on the initial corrosion behavior of low-alloy steels exposed to a CO₂–O₂–H₂S–SO₂ wet–dry corrosion environment was investigated using weight-loss measurements, scanning electron microscopy, N₂ adsorption tests, X-ray diffraction analysis, and electrochemical impedance spectroscopy. The results show that the corrosion rate increases with increasing Cr content in samples subjected to corrosion for 21 d. However, the rust grain size decreases, its specific surface area increases, and it becomes more compact and denser with increasing Cr content, which indicates the enhanced protectivity of the rust. The results of charge transfer resistance (R_ct) calculations indicate that higher Cr contents can accelerate the corrosion during the first 7 d and promote the formation of the enhanced protective inner rust after 14 d; the formed protective inner rust is responsible for the greater corrosion resistance during long-term exposure.

Effect of microstructure on the impact toughness of a bainitic steel bloom for large plastic molds

Zheng Zhang, Xiao-chun Wu, Quan Zhou, Li-li Duan

2015, 22(8): 842-850. doi: 10.1007/s12613-015-1141-8

中文摘要(214) PDF(8) SpringerLink

摘要:
The correlation between the impact toughness and microstructural characteristics of a large bainitic steel bloom has been investigated. The study focuses on microcrack nucleation and propagation in the basic cleavage plane. To analyze the phase transformation during the wind-cooling process, the temperature field of the bloom was acquired by computer simulation, and a continuous cooling transformation experiment was conducted. The results show that compared with the surface of the bloom, the toughness of the bloom’s core is decreased by the increase in proeutectoid ferrite and the coarsening of tempered martensite–austenite constituents. The proeutectoid ferrite decreases the toughness via its effects on carbide precipitation, the formation of martensite–austenite constituents, and the bainite transformation. The relatively large tempered martensite–austenite constituents are conducive to microcrack nucleation and propagation.

Effect of compression direction on the dynamic recrystallization behavior of continuous columnar-grained CuNi10Fe1Mn alloy

Yong-kang Liu, Hai-you Huang, Jian-xin Xie

2015, 22(8): 851-859. doi: 10.1007/s12613-015-1142-7

中文摘要(257) PDF(10) SpringerLink

摘要:
The dynamic recrystallization (DRX) behavior of continuous columnar-grained (CCG) CuNi10Fe1Mn alloy was investigated by hot compression along the solidification direction (SD) and perpendicular to the solidification direction (PD). Specimens were compressed to a true strain of 0.8 at temperatures ranging from 25℃ to 900℃ and strain rates ranging from 0.01 to 10 s^-1. The results indicate that DRX nucleation at grain boundaries (GBs) and DRX nucleation at slip bands (SBs) are the two main nucleation modes. For SD specimens, C-shaped bending and zig-zagging of the GBs occurred during hot compression, which made DRX nucleation at the GBs easier than that at the SBs. When lnZ ≤ 37.4 (Z is the Zener–Hollomon parameter), DRX can occur in SD specimens with a critical temperature for the DRX onset of ~650℃ and a thermal activated energy (Q) of 313.5 kJ·mol^-1. In contrast, in PD specimens, the GBs remained straight, and DRX nucleation occurred preferentially at the SBs. For PD specimens, the critical temperature is about 700℃, Q is 351.7 kJ·mol^-1, and the occurrence condition of DRX is lnZ ≤ 40.1. The zig-zagging of GB morphology can significantly reduce the nucleation energy at the GBs; as a result, DRX nucleation occurs more easily in SD specimens than in PD specimens.

Microstructure and microhardness of nanostructured Al-4.6Cu-Mn alloy ribbons

Zhong-wei Chen, Qin-ying Fan, Kai Zhao

2015, 22(8): 860-867. doi: 10.1007/s12613-015-1143-6

中文摘要(215) PDF(9) SpringerLink

摘要:
The microstructural characteristics and microhardness of nanostructured Al-4.6Cu-Mn ribbons produced by melt spinning were investigated using field-emission gun scanning electron microscopy, transmission electron microscopy, and hardness testing, and the results were compared to those of similar ribbons manufactured by direct-chill casting. It is shown that the nanostructure of the as-melt-spun ribbons consists of α-Al dendrites with a secondary dendrite arm spacing of approximately 0.55-0.80 μm and ultrafine eutectic crystals of a nanosized scale of approximately 100-200 nm on dendritic boundaries. The solidification time and cooling rate of 46-μm-thick ribbons were estimated to be 1.3×10^-6 s and 4.04×10⁶ K·s^-1, respectively. At an aging temperature of 190℃, the coherent θ″ phase in aged ribbons gradually transforms into nanoscale θ'-phase platelets as the aging time is extended from 2 to 8 h; the rod-like morphology of the T (Al₂₀Cu₂Mn₃) dispersoid with 120-160-nm diameter also forms, which results in peak aging hardness. The precipitation behaviors of aged ribbons cannot be changed at the high cooling rates of as-cast ribbons. However, a finer and more uniformly distributed microstructure and a supersaturated solid solution at a high cooling rate can shorten the time required to obtain a certain aging hardness before peak hardness.

Surface modification of Ti-49.8at%Ni alloy by Ti ion implantation: phase transformation, corrosion, and cell behavior

Yan Li, Ting Zhou, Peng Luo, Shuo-gui Xu

2015, 22(8): 868-875. doi: 10.1007/s12613-015-1144-5

中文摘要(303) PDF(9) SpringerLink

摘要:
The Ti-49.8at%Ni alloy was modified by Ti ion implantation to improve its corrosion resistance and biocompatibility. The chemical composition and morphologies of the TiNi alloy surface were determined using atomic force microscopy (AFM), auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy (XPS). The results revealed that Ti ion implantation caused the reduction of Ni concentration and the formation of a TiO₂ nano-film on the TiNi alloy. The phase transformation temperatures of the Ti–TiNi alloy remained almost invariable after Ti ion implantation. Electrochemical tests indicated that the corrosion resistance of TiNi increased after Ti ion implantation. Moreover, the Ni ion release rate in 0.9% NaCl solution for the TiNi alloy remarkably decreased due to the barrier effect of the TiO₂ nano-film. The cell proliferation behavior on Ti-implanted TiNi was better than that on the untreated TiNi after cell culture for 1 d and 3 d.

Fabrication of SrFe_12-xNi_xO₁₉ nanoparticles and investigation on their structural, magnetic and dielectric properties

S. E. Mousavi Ghahfarokhi, S. Hosseini, M. Zargar Shoushtari

2015, 22(8): 876-883. doi: 10.1007/s12613-015-1145-4

中文摘要(321) PDF(7) SpringerLink

摘要:
SrFe_12-xNi_xO₁₉ nanoparticles (x = 0–1) were synthesized by a combustion sol–gel method. Their structure, dielectric and magnetic properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), an LCR metry, and vibrating sample magnetometry (VSM).The results reveal that all samples of Ni doped compounds (SrFe_12-xNi_xO₁₉) with x < 0.2 are single phase. It appears that the Fe³⁺ ions are substituted by Ni²⁺ ions on the crystallographic sites of the SrFe₁₂O₁₉ structure; however, for x ≥ 0.2, the secondary Ni phase ferrite (NiFe₂O₃) appears, which reduces the saturation magnetization and coercivity. In addition, Ni doping reduces the dielectric constant, dielectric loss, and alternating current (ac) electrical conductivity of the samples. The variation in ac conductivity (σ_ac) with frequency shows that the electrical conductivity in these ferrites is mainly attributed to the electron hopping mechanism.Therefore; all the single-phase Ni doped samples are suitable for use in magnetic recording media and microwave devices.

Molten salt synthesis of mullite nanowhiskers using different silica sources

Tao Yang, Peng-long Qiu, Mei Zhang, Kuo-Chih Chou, Xin-mei Hou, Bai-jun Yan

2015, 22(8): 884-891. doi: 10.1007/s12613-015-1146-3

中文摘要(298) PDF(10) SpringerLink

摘要:
Mullite nanowhiskers with Al-rich structure were prepared by molten salt synthesis at 1000℃ for 3 h in air using silica, amorphous silica, and ultrafine silica as the silica sources. The phase and morphology of the synthesized products were investigated by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and transmission electron microscopy. A thermogravimetric and differential thermal analysis was carried out to determine the reaction mechanism. The results reveal that the silica sources play an important role in determining the morphology of the obtained mullite nanowhiskers. Clusters and disordered arrangements are obtained using common silica and amorphous silica, respectively, whereas the use of ultrafine silica leads to highly ordered mullite nanowhiskers that are 80-120 nm in diameter and 20-30 μm in length. Considering the growth mechanisms, mullite nanowhiskers in the forms of clusters and highly ordered arrangements can be attributed to heterogeneous nucleation, whereas disordered mullite nanowhiskers are obtained by homogenous nucleation.

Preparation and characterization of high-strength calcium silicate boards from coal-fired industrial solid wastes

Zhao Cao, Yong-dan Cao, Jin-shan Zhang, Chun-bao Sun, Xian-long Li

2015, 22(8): 892-900. doi: 10.1007/s12613-015-1147-2

中文摘要(399) PDF(10) SpringerLink

摘要:
To realize the comprehensive utilization of coal-fired industrial solid wastes, a novel high-strength board was prepared from calcium silicate slag, fly ash, and flue gas desulfurization (FGD) gypsum. The changes in mineral phases, chemical structure, and morphology during hydration were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). A traditional board made from quartz and lime was prepared as a reference. The novel board not only consumes a lot of solid wastes, but also meets the strength requirement of the class-five calcium silicate board according to the Chinese Standard JC/T 564.2—2008. Microanalysis showed that hydrated calcium silicate gel (C-S-H(I)), ettringite, tobermorite, and xonotlite were successively generated in the novel board by synergistic hydration of the mixed solid wastes. The board strength was improved by the formation of tobermorite and xonotlite but decreased by unhydrated quartz. It was demonstrated that quartz was not completely hydrated in the traditional board. As a result, the flexural strength of the traditional board was much lower than that of the novel board.

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2015年第22卷第8期