International Journal of Minerals, Metallurgy and Materials

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In situ characterization of natural pyrite bioleaching using electrochemical noise technique

Guo-bao Chen, Hong-ying Yang, Hai-jun Li

2016, 23(2): 117-126. doi: 10.1007/s12613-016-1218-z

中文摘要(287) PDF(9) SpringerLink

摘要:
An in situ characterization technique called electrochemical noise (ECN) was used to investigate the bioleaching of natural pyrite. ECN experiments were conducted in four active systems (sulfuric acid, ferric-ion, 9k culture medium, and bioleaching solutions). The ECN data were analyzed in both the time and frequency domains. Spectral noise impedance spectra obtained from power spectral density (PSD) plots for different systems were compared. A reaction mechanism was also proposed on the basis of the experimental data analysis. The bioleaching system exhibits the lowest noise resistance of 0.101 MΩ. The bioleaching of natural pyrite is considered to be a bio-battery reaction, which distinguishes it from chemical oxidation reactions in ferric-ion and culture-medium (9k) solutions. The corrosion of pyrite becomes more severe over time after the long-term testing of bioleaching.

Electrochemical and spectroscopic study of interfacial interactions between chalcopyrite and typical flotation process reagents

Gustavo Urbano, Isabel Lázaro, Israel Rodríguez, Juan Luis Reyes, Roxana Larios, Roel Cruz

2016, 23(2): 127-136. doi: 10.1007/s12613-016-1219-y

中文摘要(234) PDF(16) SpringerLink

摘要:
Comparative voltammetry and differential double-layer capacitance studies were performed to evaluate interfacial interactions between chalcopyrite (CuFeS₂) and n-isopropyl xanthate (X) in the presence of ammonium bisulfite/39wt% SO₂ and caustic starch at different pH values. Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, contact angle measurements, and microflotation tests were used to establish the type and extent of xanthate adsorption as well as the species involved under different mineral surface conditions in this study. The results demonstrate that the species that favor a greater hydrophobicity of chalcopyrite are primarily CuX and S⁰, whereas oxides and hydroxides of Cu and Fe as well as an excess of starch decrease the hydrophobicity. A conditioning of the mineral surface with ammonium bisulfite/39wt% SO₂ at pH 6 promotes the activation of surface and enhances the xanthate adsorption. However, this effect is diminished at pH ≥ 8, when an excess of starch is added during the preconditioning step.

Uniformity evaluation and optimization of fluid flow characteristics in a seven-strand tundish

Min Wang, Chao-jie Zhang, Rui Li

2016, 23(2): 137-145. doi: 10.1007/s12613-016-1220-5

中文摘要(293) PDF(11) SpringerLink

摘要:
The effect of flow control devices (FCDs) on the uniformity of flow characteristics in a seven-strand symmetrical trapezoidal tundish was studied using both an experimental 1:2.5 hydraulic model and a numerical simulation of a 1:1 geometric model. The variation coefficient (CV) was defined to evaluate the flow uniformity of the seven-strand tundish. An optimized FCD configuration was proposed on the basis of the evaluation of experimental results. It is concluded that a turbulence inhibitor (TI) and U-type dam are essential to improve the uniformity of fluid flow in the seven-strand tundish. In addition, the configuration of inclination T-type dams with a height of 200 mm between the second and third strands and with a height of 300 mm between the third and fourth strands can minimize the proportion of dead zone. After optimizing the configuration of FCDs, the variation coefficient reduces below 20% of the mean value, and the average proportion of dead zone is just 14.6%; in addition, the temperature fluctuation between the strands could be controlled within 0.6 K. In summary, the uniformity of flow and temperature in the seven-strand tundish is greatly improved.

A novel hydrothermal method for zinc extraction and separation from zinc ferrite and electric arc furnace dust

Hui-gang Wang, Yang Li, Jian-ming Gao, Mei Zhang, Min Guo

2016, 23(2): 146-155. doi: 10.1007/s12613-016-1221-4

中文摘要(539) PDF(42) SpringerLink

摘要:
A novel hydrothermal process was developed to extract zinc from pure zinc ferrite (ZnFe₂O₄) nanopowder and zinc-containing electric arc furnace (EAF) dust using hexahydrated ferric chloride (FeCl₃·6H₂O) as a decomposing agent. The effects of solid FeCl₃·6H₂O to ZnFe₂O₄ ratio by mass (R_F/Z), hydrothermal reaction temperature, and time on zinc extraction were systematically investigated. In the results, when the hydrothermal reaction is conducted at 150℃ for 2 h with R_F/Z of 15:20, the efficiency of zinc extraction from ZnFe₂O₄ reaches 97.2%, and the concentration of ferric ions (Fe³⁺) in the leaching solution is nearly zero, indicating a high selectivity for zinc. In addition, the zinc extraction efficiency from the EAF dust reaches 94.5% in the case of the hydrothermal reaction performed at 200℃ for 10 h with the solid FeCl₃·6H₂O to EAF dust ratio by mass (R_{F/EAF dust}) of 15:10. Zinc and iron separation is achieved by adjusting the pH value of the leaching solution according to the different precipitation pH values of metal hydroxides.

A novel process for comprehensive utilization of vanadium slag

Li-ying Liu, Tao Du, Wen-jun Tan, Xin-pu Zhang, Fan Yang

2016, 23(2): 156-160. doi: 10.1007/s12613-016-1222-3

中文摘要(306) PDF(10) SpringerLink

摘要:
Traditional processes for treating vanadium slag generate a huge volume of solid residue and a large amount of harmful gas, which cause serious environmental problems. In this study, a new process for the comprehensive utilization of vanadium slag was proposed, wherein zeolite A and a V₂O₅/TiO₂ system were synthesized. The structural properties of the as-synthesized zeolite A and the V₂O₅/TiO₂ system were characterized using various experimental techniques, including X-ray diffraction, X-ray fluorescence, scanning electron microscopy, and infrared spectroscopy. The results reveal that zeolite A and the V₂O₅/TiO₂ system are successfully obtained with high purity. The results of gas adsorption measurements indicate that the prepared zeolite A exhibits high selectivity for CO₂ over N₂ and is a candidate material for CO₂ capture from flue-gas streams.

Variation in retained austenite content and mechanical properties of 0.2C–7Mn steel after intercritical annealing

Chuan Zhao, Chi Zhang, Wen-quan Cao, Zhi-gang Yang

2016, 23(2): 161-167. doi: 10.1007/s12613-016-1223-2

中文摘要(253) PDF(11) SpringerLink

摘要:
The effects of annealing time and temperature on the retained austenite content and mechanical properties of 0.2C–7Mn steel were studied. The retained austenite content of 0.2C–7Mn steel was compared with that of 0.2C–5Mn steel. It is found that 0.2C–7Mn steel exhibits a similar variation trend of retained austenite content as 0.2C–5Mn steel. However, in detail, these trends are different. 0.2C–7Mn steel contains approximately 7.5vol% retained austenite after austenitization and quenching. The stability of the reversed austenite in 0.2C–7Mn steel is lower than that in 0.2C–5Mn steel; in contrast, the equilibrium reversed austenite fraction of 0.2C–7Mn steel is substantially greater than that of 0.2C–5Mn steel. Therefore, the retained austenite content in 0.2C–7Mn steel reaches 53.1vol%. The tensile results show that long annealing time and high annealing temperature may not favor the enhancement of mechanical properties of 0.2C–7Mn steel. The effect of retained austenite on the tensile strength of the steel depends on the content of retained austenite; in contrast, the 0.2% yield strength linearly decreases with increasing retained austenite content.

Effect of aging temperature on the microstructures and mechanical properties of ZG12Cr9Mo1Co1NiVNbNB ferritic heat-resistant steel

Xue Yang, Lan Sun, Ji Xiong, Ping Zhou, Hong-yuan Fan, Jian-yong Liu

2016, 23(2): 168-175. doi: 10.1007/s12613-016-1224-1

中文摘要(339) PDF(13) SpringerLink

摘要:
The effect of aging on the mechanical properties and microstructures of a new ZG12Cr9Mo1Co1NiVNbNB ferritic heat resistant steel was investigated in this work to satisfy the high steam parameters of the ultra-supercritical power plant. The results show that the main precipitates during aging are Fe(Cr, Mo)₂₃C₆, V(Nb)C, and (Fe₂Mo) Laves in the steel. The amounts of the precipitated phases increase during aging, and correspondingly, the morphologies of phases are similar to be round. Fe(Cr, Mo)₂₃C₆ appears along boundaries and grows with increasing temperature. In addition, it is revealed that the martensitic laths are coarsened and eventually happen to be polygonization. The hardness and strength decrease gradually, whereas the plasticity of the steel increases. What’s more, the hardness of this steel after creep is similar to that of other 9%–12%Cr ferritic steels. Thus, ZG12Cr9Mo1Co1NiVNbNB can be used in the project.

Corrosion behavior and characteristics of the product film of API X100 steel in acidic simulated soil solution

Cui-wei Du, Tian-liang Zhao, Zhi-yong Liu, Xiao-gang Li, Da-wei Zhang

2016, 23(2): 176-183. doi: 10.1007/s12613-016-1225-0

中文摘要(261) PDF(8) SpringerLink

摘要:
The short-term corrosion behavior of API X100 steel in an acidic simulated soil was investigated by electrochemical measurements and soaking experiments, followed by corrosion morphology observations and X-ray photoelectron spectroscopy analyses. The results show that X100 steel exhibits an obvious pitting susceptibility in an acidic soil environment. Pits nucleate after approximately 10 h of immersion. Along with the nucleation and growth of the pits, the charge-transfer resistance and open-circuit potential first increase sharply, then decrease slowly, and eventually reach a steady state. The maxima of the charge-transfer resistance and open-circuit potential are attained at approximately 10 h. The evolution of the electrochemical process is confirmed by the analysis of the product film. The product film exhibits a porous and loose structure and could not protect the substrate well. The product film is primarily composed of ferrous carbonate and ferrous hydroxide (Fe(OH)₂). The concentration of Fe(OH)₂ in the product film increases from the inside to the outside layer.

Microstructure characteristics of Ni/WC composite cladding coatings

Gui-rong Yang, Chao-peng Huang, Wen-ming Song, Jian Li, Jin-jun Lu, Ying Ma, Yuan Hao

2016, 23(2): 184-192. doi: 10.1007/s12613-016-1226-z

中文摘要(280) PDF(8) SpringerLink

摘要:
A multilayer tungsten carbide particle (WCp)-reinforced Ni-based alloy coating was fabricated on a steel substrate using vacuum cladding technology. The morphology, microstructure, and formation mechanism of the coating were studied and discussed in different zones. The microstructure morphology and phase composition were investigated by scanning electron microscopy, optical microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. In the results, the coating presents a dense and homogeneous microstructure with few pores and is free from cracks. The whole coating shows a multilayer structure, including composite, transition, fusion, and diffusion-affected layers. Metallurgical bonding was achieved between the coating and substrate because of the formation of the fusion and diffusion-affected layers. The Ni-based alloy is mainly composed of γ-Ni solid solution with finely dispersed Cr₇C₃/Cr₂₃C₆, CrB, and Ni+Ni₃Si. WC particles in the composite layer distribute evenly in areas among initial Ni-based alloying particles, forming a special three-dimensional reticular microstructure. The macrohardness of the coating is HRC 55, which is remarkably improved compared to that of the substrate. The microhardness increases gradually from the substrate to the composite zone, whereas the microhardness remains almost unchanged in the transition and composite zones.

Fabrication of Fe–TiC–Al₂O₃ composites on the surface of steel using a TiO₂–Al–C–Fe combustion reaction induced by gas tungsten arc cladding

Mahmood Sharifitabar, Jalil Vahdati Khaki, Mohsen Haddad Sabzevar

2016, 23(2): 193-204. doi: 10.1007/s12613-016-1227-y

中文摘要(211) PDF(8) SpringerLink

摘要:
The aim of the present study was to fabricate Fe–TiC–Al₂O₃ composites on the surface of medium carbon steel. For this purpose, TiO₂–3C and 3TiO₂–4Al–3C–xFe (0 ≤ x ≤ 4.6 by mole) mixtures were pre-placed on the surface of a medium carbon steel plate. The mixtures and substrate were then melted using a gas tungsten arc cladding process. The results show that the martensite forms in the layer produced by the TiO₂–3C mixture. However, ferrite–Fe₃C–TiC phases are the main phases in the microstructure of the clad layer produced by the 3TiO₂–4Al–3C mixture. The addition of Fe to the TiO₂–4Al–3C reactants with the content from 0 to 20wt% increases the volume fraction of particles, and a composite containing approximately 9vol% TiC and Al₂O₃ particles forms. This composite substantially improves the substrate hardness. The mechanism by which Fe particles enhance the TiC + Al₂O₃ volume fraction in the composite is determined.

Temperature effect on the corrosion and passivation characterization of Ni_82.3Cr₇Fe₃Si_4.5B_3.2 alloy in acidic media

Khadijah M. Emran, Sanaa T. Arab, Aisha M. Al-Turkustani, Hamad A. Al-Turaif

2016, 23(2): 205-214. doi: 10.1007/s12613-016-1228-x

中文摘要(202) PDF(11) SpringerLink

摘要:
The effects of temperature on corrosion and the electrochemical behavior of Ni_82.3Cr₇Fe₃Si_4.5B_3.2 glassy alloy in HCl, H₂SO₄, and H₃PO₄ acids were studied using AC and DC techniques. Impedance data reveal that the susceptibility to localized corrosion increases with increasing temperature. Potentiodynamic polarization curves reveal that the bulk glassy alloy is spontaneously passivated at all the investigated temperature in H₂SO₄ and H₃PO₄ solutions. A localized corrosion effect in HCl solution is clearly observed. The apparent activation energies in the regions of Tafel, active, and passive, as well as the enthalpies and entropies of the dissolution process were determined and discussed. The high apparent activation energy (E_a) value for H₃PO₄ solution in Tafel region is explained by the low aggressivity of PO₄^3- ions.

Burn-resistant behavior and mechanism of Ti14 alloy

Yong-nan Chen, Ya-zhou Huo, Xu-ding Song, Zhao-zhao Bi, Yang Gao, Yong-qing Zhao

2016, 23(2): 215-221. doi: 10.1007/s12613-016-1229-9

中文摘要(313) PDF(14) SpringerLink

摘要:
The direct-current simulation burning method was used to investigate the burn-resistant behavior of Ti14 titanium alloy. The results show that Ti14 alloy exhibits a better burn resistance than TC4 alloy (Ti–6Al–4V). Cu is observed to preferentially migrate to the surface of Ti14 alloy during the burning reaction, and the burned product contains Cu, Cu₂O, and TiO₂. An oxide layer mainly comprising loose TiO₂ is observed beneath the burned product. Meanwhile, Ti₂Cu precipitates at grain boundaries near the interface of the oxide layer, preventing the contact between O₂ and Ti and forming a rapid diffusion layer near the matrix interface. Consequently, a multiple-layer structure with a Cu-enriched layer (burned product)/Cu-lean layer (oxide layer)/Cu-enriched layer (rapid diffusion layer) configuration is formed in the burn heat-affected zone of Ti14 alloy; this multiple-layer structure is beneficial for preventing O₂ diffusion. Furthermore, although Al can migrate to form Al₂O₃ on the surface of TC4 alloy, the burn-resistant ability of TC4 is unimproved because the Al₂O₃ is discontinuous and not present in sufficient quantity.

Chemical, mechanical, and thermal expansion properties of a carbon nanotube-reinforced aluminum nanocomposite

Manjula Sharma, Vimal Sharma

2016, 23(2): 222-233. doi: 10.1007/s12613-016-1230-3

中文摘要(332) PDF(11) SpringerLink

摘要:
In the present study, the chemical and mechanical properties and the thermal expansion of a carbon nanotube (CNT)-based crystalline nano-aluminum (nano Al) composite were reported. The properties of nanocomposites were tailored by incorporating CNTs into the nano Al matrix using a physical mixing method. The elastic moduli and the coefficient of thermal expansion (CTE) of the nanocomposites were also estimated to understand the effects of CNT reinforcement in the Al matrix. Microstructural characterization of the nanocomposite reveals that the CNTs are dispersed and embedded in the Al matrix. The experimental results indicate that the incorporation of CNTs into the nano Al matrix results in the increase in hardness and elastic modulus along with a concomitant decrease in the coefficient of thermal expansion. The hardness and elastic modulus of the nanocomposite increase by 21% and 20%, respectively, upon CNT addition. The CTE of CNT/Al nanocomposite decreases to 70% compared with that of nano Al.

Synthesis and application of bilayer-surfactant-enveloped Fe₃O₄ nanoparticles: water-based bilayer-surfactant-enveloped ferrofluids

Bai-yi Chen, Jian-hui Qiu, Hui-xia Feng

2016, 23(2): 234-240. doi: 10.1007/s12613-016-1231-2

中文摘要(341) PDF(17) SpringerLink

摘要:
Superparamagnetic carbon-coated Fe₃O₄ nanoparticles with high magnetization (85 emu·g^-1) and high crystallinity were synthesized using polyethylene glycol-4000 (PEG (4000)) as a carbon source. Fe₃O₄ water-based bilayer-surfactant-enveloped ferrofluids were subsequently prepared using sodium oleate and PEG (4000) as dispersants. Analyses using X-ray photoelectron spectroscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy indicate that the Fe₃O₄ nanoparticles with a bilayer surfactant coating retain the inverse spinel-type structure and are successfully coated with sodium oleate and PEG (4000). Transmission electron microscopy, vibrating sample magnetometry, and particle-size analysis results indicate that the coated Fe₃O₄ nanoparticles also retain the good saturation magnetization of Fe₃O₄ (79.6 emu·g^-1) and that the particle size of the bilayer-surfactant-enveloped Fe₃O₄ nanoparticles is 42.97 nm, which is substantially smaller than that of the unmodified Fe₃O₄ nanoparticles (486.2 nm). UV–vis and zeta-potential analyses reveal that the ferrofluids does not agglomerate for 120 h at a concentration of 4 g·L^-1, which indicates that the ferrofluids are highly stable.

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2016年第23卷第2期

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2016年第23卷第2期