International Journal of Minerals, Metallurgy and Materials

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Processing technologies for gold-telluride ores

Jian Zhang, Yao Zhang, William Richmond, Hai-peng Wang

2010, 17(1): 1-10. doi: 10.1007/s12613-010-0101-6

中文摘要(360) PDF(22) SpringerLink

摘要:
Gold telluride ores are important gold refractory ores due to the presence of sulfides and other gangue materials. The classification and main physical properties of gold telluride ores were described, and possible treatment methods including flotation, leaching, and oxidation were reviewed. The results show that flotation procedures are much easier for gold tellurides compared to other refractory gold-bearing ores. For the conventional cyanide leaching process, pretreatment such as oxidation is required to achieve high gold recovery. Roasting is a relatively simple but not environment-friendly method; bio-oxidation technology seems to be more suitable for the oxidation of flotation concentrate. Other treatment methods involve cyanide leaching, thiourea leaching, ammoniacal thiosulfate leaching, carbon-in-pulp, and resin-in-pulp, all of which are less commonly utilized.

Ore-proportioning optimization technique with high proportion of Yandi ore in sintering

Sheng-li Wu, Hong-liang Han, Hai-xia Li, Jian Xu, Shi-dong Yang, Xiao-qin Liu

2010, 17(1): 11-16. doi: 10.1007/s12613-010-0102-5

中文摘要(254) PDF(9) SpringerLink

摘要:
The basic sintering characteristics of Yandi ore from Australia, including assimilation ability, liquid phase fluidity, self-strength of bonding phase, forming ability of silico ferrite of calcium and aluminum (SFCA), and so on, were investigated in detail. Besides, the high temperature behavior and function of sintering were obtained. As a result, the techniques for ore-proportioning in sintering were obtained. The results show that Yandi ore possessing higher assimilation ability, better liquid phase fluidity, lower self-strength of bonding phase, and better forming ability of SFCA, should be mixed with iron ores whose properties are opposite to those of Yandi ore. In the optimization of sintering ore-proportioning, Yandi ore, whose price is relatively low, can be mixed as high as 40wt%.

Periodic flow characteristics during RH vacuum circulation refining

Xin-gang Ai, Yan-ping Bao, Wei Jiang, Jian-hua Liu, Peng-huan Li, Tai-quan Li

2010, 17(1): 17-21. doi: 10.1007/s12613-010-0103-4

中文摘要(289) PDF(9) SpringerLink

摘要:
The circulation period of RH vacuum refining was studied to promote the refining efficiency. The influences of the lift gas flow rate and submersion depth of snorkels on the circulation period, and the relationship between mixing time and circulation flow were discussed. The effects of the lift gas flow rate and submersion depth on the degassing rate in one circulation period were studied by water modeling. The results show that the circulation period is shortened by increasing the lift gas flow rate. The circulation period is the shortest when the submersion depth of snorkels is 560 mm. The whole ladle can be mixed thoroughly after three times of circulation. Increasing the lift gas flow rate can enhance the degassing rate of RH circulation.

Decarburization rate of RH refining for ultra low carbon steel

Bai-song Liu, Guo-sen Zhu, Huan-xi Li, Ben-hai Li, Yang cui, Ai-min Cui

2010, 17(1): 22-27. doi: 10.1007/s12613-010-0104-3

中文摘要(357) PDF(16) SpringerLink

摘要:
The decarburization behaviors of ultra low carbon steel in a 210-t RH vacuum degasser were investigated under practical operating conditions. According to the apparent decarburization rate constant (K_C) calculated by the carbon content in the samples taken from the hot melt in a ladle at an interval of 1–2 min, it is observed that the total decarburization reaction period in RH can be divided into the quick decarburization period and the stagnant decarburization period, which is quite different from the traditional one with three stages. In this study, the average apparent decarburization rate constant during the quick decarburization period is 0.306 min^-1, and that of the stagnant period is 0.072 min^-1. Increasing the initial carbon content and enhancing the exhausting capacity can increase the apparent decarburization rate constant in the quick decarburization period. The decarburization reaction comes into the stagnant decarburization period when the carbon content in molten steel is less than 14×10^-6 after 10 min of decarburization.

Determination of inclusions in liquid steel after calcium treatment

Kabamba Tshilombo

2010, 17(1): 28-31. doi: 10.1007/s12613-010-0105-2

中文摘要(265) PDF(20) SpringerLink

摘要:
Nozzle blocking was eliminated by calcium-treated liquid steel through changing the chemical and phase composition of alumina inclusions in aluminium-killed steel. Three different methods were applied to determine the composition of inclusions in liquid steel: total oxygen content samples, sampling spoon samples, and “lollipop” steel samples. The results show that calcium modification of liquid steel influences the inclusion composition varying from 2wt% to 14wt% depending on the method used. The composition of inclusions contains mainly Al₂O₃-CaO only, or is associated with SiO₂ or MgO depending on the initial input. The methods used in this study are indicators of the inclusion composition but can be improved to quantify the inclusion size.

Thermodynamic analysis on the formation mechanism of MgO·Al₂O₃ spinel type inclusions in casing steel

Hai-yan Tang, Jing-she Li

2010, 17(1): 32-38. doi: 10.1007/s12613-010-0106-1

中文摘要(239) PDF(9) SpringerLink

摘要:
MgO·Al₂O₃ spinel type inclusions in casing steel were analyzed by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The results show that there are three forms. One is pure MgO·Al₂O₃ spinel, another is the composite oxide of the Mg-Al-Ca-Si-O system, and the third is the complex with oxide as a core covered by sulfide. The formation mechanisms were studied. The influences of slag basicity and vacuum degree on the magnesium content during the vacuum treatment of molten steel and furnace lining in molten steel were calculated with the coexistence theory of slag structure. The results show that the magnesium content increases with the increase in slag basicity and aluminum content in molten steel, and decreases with the increase in CO partial pressure.

Experimental determination of mechanical properties and short-time creep of AISI 304 stainless steel at elevated temperatures

Josip Brnic, Ji-tai Niu, Goran Turkalj, Marko Canadija, Domagoj Lanc

2010, 17(1): 39-45. doi: 10.1007/s12613-010-0107-0

中文摘要(439) PDF(14) SpringerLink

摘要:
The high temperature properties of AISI 304 stainless steel were studied. Basic data about the employed experimental equipment, testing procedures, and specimen geometry were given. The experimental setup was used to obtain stress-strain diagrams from tensile tests at room temperature as well as several elevated temperatures. Furthermore, the specimens were subjected to short-time creep tests at various temperatures. Stress levels for creep testing were established as a percentage of yield stress. The results indicate that at lowered temperatures and lower stress levels, AISI 304 stainless steel can be used as a sufficiently creep resistant material.

Deformation behavior and microstructure of an Al-Zn-Mg-Cu-Zr alloy during hot deformation

Liang-ming Yan, Jian Shen, Jun-peng Li, Zhou-bing Li, Xiao-dong Yan

2010, 17(1): 46-52. doi: 10.1007/s12613-010-0108-z

中文摘要(238) PDF(10) SpringerLink

摘要:
The hot deformation behavior and microstructures of Al-7055 commercial alloy were investigated by axisymmetric hot compression at temperatures ranging from 300℃ to 450℃ and strain rates from 10^-2 to 10 s^-1, respectively. Microstructures of deformed 7055 alloy were investigated by transmission electron microscopy (TEM). The dependence of peak stress on deformation temperature and strain rate can be expressed by the hyperbolic-sine type equation. The hot deformation activation energy of the alloy is 146 kJ/mol. Moreover, the flow stress curves predicted by the modified constitutive equations are reasonably consistent with the experimental results, which confirms that the proposed deformation constitutive equations can provide evidence for the selection of hot forming parameters. TEM results indicate that dynamic recovery is the main softening mechanism during hot deformation.

Thixo-forging and simulation of complex parts of aluminum alloy AlSi7Mg

Kai-kun Wang

2010, 17(1): 53-57. doi: 10.1007/s12613-010-0109-y

中文摘要(236) PDF(10) SpringerLink

摘要:
In order to investigate the formability of metal material in semisolid state, a series of experiments were carried out by thixo-forging the complex part of aluminum alloy AlSi7Mg. Through changing the upper punch, aluminum parts with different upper-cup dimensions can be successfully produced. The numerical simulation was conducted for investigating the forming limits of AlSi7Mg during thixo-forging. It is found that the simulation result is in good agreement with the experiment one.

Hydrogen-induced cracking behaviors of Incoloy alloy 825

Yong-jin Yang, Ke-wei Gao, Chang-feng Chen

2010, 17(1): 58-62. doi: 10.1007/s12613-010-0110-5

中文摘要(254) PDF(8) SpringerLink

摘要:
The effect of hydrogen on the fracture behaviors of Incoloy alloy 825 was investigated by means of slow strain rate testing (SSRT). Hydrogen was introduced into the sample by electrochemical charging. The results show that surface microcracks form gradually during aging at room temperature when desorption of hydrogen takes place after hydrogen charging at a current density of 5 mA/cm² for 24 h. SSRT shows that the increase of ductility loss is significantly obvious as the hydrogen charging current density increases. Scanning electron microscopy (SEM) images reveal ductile fracture in the pre-charged sample with low current densities, while the fracture includes small quasi-cleavage regions and tends to be brittle fracture as the hydrogen charging current density increases to 5 mA/cm².

Macrostructure and properties of thin walled copper tubes prepared by the downward continuous unidirectional solidification method

Xi Shen, Hong Zhang, Zi-dong Wang, Hua-fen Lou, Yi-ming Jia, Ping-xia Hu

2010, 17(1): 63-68. doi: 10.1007/s12613-010-0111-4

中文摘要(164) PDF(8) SpringerLink

摘要:
The macrostructure and properties of the thin walled copper tube prepared by the downward continuous unidirectional solidification (DCUS) method were studied. The result shows that the macrostructure is closely related to the solid-liquid interface profile, which is influenced by the distance between the cooling water location and the solidification front. The mechanical properties of the thin walled copper tube prepared by the DCUS method are near those of the normal cast copper, and it has good relative density, electrical conductivity, and elongation, which are not greatly affected by casting speed. The thin walled copper tube prepared by the DCUS method also has good processing properties that can be taken to further drawing procedures directly without an intermediate process, and obtains good mechanical properties with the total processing rate of 89.8%.

Mechanical properties of electroformed copper layers with gradient microstructure

Qiang Liao, Li-qun Zhu, Hui-cong Liu, Wei-ping Li

2010, 17(1): 69-74. doi: 10.1007/s12613-010-0112-3

中文摘要(226) PDF(8) SpringerLink

摘要:
The electroformed copper layer with gradient microstructure was prepared using the ultrasonic technique. The microstructure of the electroformed copper layer was observed by using an optical microscope (OM) and a scanning electron microscope (SEM). The preferred orientations of the layer were characterized by X-ray diffraction (XRD). The mechanical properties were evaluated with a Vicker’s hardness tester and a tensile tester. It is found the gradient microstructure consists of two main parts: the outer part (faraway substrate) with columnar crystals and the inner part (nearby substrate) with equiaxed grains. The Cu-(220) preferred orientation increases with the increasing thickness of the copper layer. The test results show that the microhardness of the electroformed copper layer decreases with increasing grain size along the growth direction and presents a gradient distribution. The tensile strength of the outer part of the electroformed copper layer is higher than that of the inner part but at the cost of ductility. Meanwhile, the integral mechanical properties of the electroformed copper with gradient microstructure are significantly improved in comparison with the pure copper deposit.

3D Modeling of the preparation process of metal rubber material

Ming-ji Huang, Xiu-ping Dong, Guo-quan Liu

2010, 17(1): 75-79. doi: 10.1007/s12613-010-0113-2

中文摘要(238) PDF(12) SpringerLink

摘要:
Based on the analysis of the preparation of metal rubber (MR) and two pivotal hypotheses, the uniform distribution and the unaltered topological structure of wires in the radial direction of columns in the punch process, a 3D parametrical model was established based on four approaches: helix-making, planar roughcast-weaving, planar roughcast-rolling, and 3D roughcast punching. In the modeling process, 5 lattice types of weave patterns in planar roughcast were put forward, and 10 quantificational modeling parameters were picked up to exclusively define the column MR component structure. The wire distribution was visualized by CAD techniques. The important performance parameter of column MR components (relative density ρ) can be forecasted by modeling computing, which provides the necessary foundation for the design and optimization of MR materials.

Rapid growth of ZnO hexagonal tubes by direct microwave heating

Zhen-qi Zhu, Jian Zhou

2010, 17(1): 80-85. doi: 10.1007/s12613-010-0114-1

中文摘要(287) PDF(7) SpringerLink

摘要:
Zinc oxide hexagonal tubular crystals were synthesized by direct microwave heating from ZnO powders within 5 min without any metal catalysts or transport agents. ZnO source materials were evaporated from the high-temperature zone in an enclosure, and crystals were grown on the self-source substrate in an appropriate condition. The ZnO vapor formed in the high-temperature zone can deposit and grow on the powders located in the low-temperature zone to form crystals. The scanning electron microscopy (SEM) reveals that these products are hexagonal tube crystals with 80 μm in diameter and 250 μm in length, having a well faceted end and side surface. A possible growth mechanism and the influence of reaction temperature on the formation of crystalline ZnO hexagonal tubes were presented. The photoluminescence (PL) exhibits strong ultraviolet emission at room temperature, indicating the potential applications in short-wave light-emitting photonic devices.

Effect of SiO₂ addition on the microstructure and electrical properties of ZnO-based varistors

Zhen-hong Wu, Jian-hui Fang, Dong Xu, Qin-dong Zhong, Li-yi Shi

2010, 17(1): 86-91. doi: 10.1007/s12613-010-0115-0

中文摘要(313) PDF(17) SpringerLink

摘要:
The microstructure and electrical properties of ZnO-based varistors with the SiO₂ content in the range of 0–1.00mol% were prepared by a solid reaction route. The varistors were characterized by scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectrometry, inductively coupled plasma-atomic emission spectrometry, and X-ray photoelectron spectroscopy. The results indicate that the average grain size of ZnO decreases with the SiO₂ content increasing. A new second phase (Zn₂SiO₄) and a glass phase (Bi₂SiO₅) are found. Element Si mainly exists in the grain boundary and plays an important role in controlling the Bi₂O₃ vaporization. The electric measurement shows that the incorporation of SiO₂ can significantly improve the nonlinear properties of ZnO-based varistors, and the nonlinear coefficients of the varistors with SiO₂ are in the range of 36.8–69.5. The varistor voltage reaches the maximum value of 463 V/mm and the leakage current reaches the minimum value of 0.11 μA at the SiO₂ content of 0.75mol%.

Preparation and performance of dye-sensitized solar cells based on ZnO-modified TiO₂ electrodes

Sheng-jun Li, Yuan Lin, Wei-wei Tan, Jing-bo Zhang, Xiao-wen Zhou, Jin-mao Chen, Zeng Chen

2010, 17(1): 92-97. doi: 10.1007/s12613-010-0116-z

中文摘要(251) PDF(12) SpringerLink

摘要:
The ZnO-modified TiO₂ electrode was prepared by adding Zn(CH₃COO)₂·2H₂O to the TiO₂ colloid during the sol-gel production process, and was used in dye-sensitized solar cells (DSCs). The open circuit voltage (V_OC) and fill factor (ff) of the cells were improved significantly. The performances of the ZnO-modified TiO₂ electrode such as dark current, transient photocurrent, impedance, absorption spectra, and flat band potential (V_fb) were investigated. It is found that the interface charge recombination impedance increases and V_fb shifts about 200 mV toward the cathodic potential. The effect mechanism of ZnO modification on the performance of DSCs may be that ZnO occupies the surface states of the TiO₂ film.

Influence of substrate metals on the crystal growth of AlN films

Juan Xiong, Hao-shuang Gu, Kuan Hu, Ming-zhe Hu

2010, 17(1): 98-103. doi: 10.1007/s12613-010-0117-y

中文摘要(243) PDF(14) SpringerLink

摘要:
AlN films were deposited by reactive radio frequency (RF) sputtering on various bottom electrodes, such as Al, Ti, Mo, Au/Ti, and Pt/Ti. The effects of substrate metals on the orientation of AlN thin films were investigated. The results of X-ray diffraction, atomic force microscopy, and field emission scanning electron microscopy show that the orientation of AlN films depends on the kinds of substrate metals evidently. The differences of AlN films deposited on various metal electrodes are attributed to the differences in lattice mismatch and thermal expansion coefficient between the AlN material and substrate metals. The AlN film deposited on the Pt/Ti electrode reveals highly the c-axis orientation with well-textured columnar structure. The positive role of the Pt/Ti electrode in achieving the high-quality AlN films and high-performance film bulk acoustic resonator (FBAR) may be attributed to the smaller lattice mismatch as well as the similarity of thermal expansion coefficient between the deposited AlN material and the Pt/Ti electrode substrate.

Electrodeposition and characterization of thermoelectric Bi₂Se₃ thin films

Xiao-long Li, Ke-feng Cai, Hui Li, Ling Wang, Chi-wei Zhou

2010, 17(1): 104-107. doi: 10.1007/s12613-010-0118-x

中文摘要(293) PDF(17) SpringerLink

摘要:
Bi₂Se₃ thin films were electrochemically deposited on Ti and indium tin oxide-coated glass substrates, respectively, at room temperature, using Bi(NO₃)₃·5H₂O and SeO₂ as starting materials in diluted HNO₃ solution. A conventional three-electrode cell was used with a platinum sheet as a counter electrode, and a saturated calomel electrode was used as a reference electrode. The films were annealed in argon atmosphere. The influence of cold isostatic pressing before annealing on the microstructure and thermoelectric properties of the films was investigated. X-ray diffraction analysis indicates that the film grown on the indium tin oxide-coated glass substrate is pure rhombohedral Bi₂Se₃, and the film grown on the Ti substrate consists of both rhombohedral and orthorhombic Bi₂Se₃.

Relationship between the microstructure and reaction performance of aluminosilicate

Xiao-ming Liu, Heng-hu Sun, Xiang-peng Feng, Na Zhang

2010, 17(1): 108-115. doi: 10.1007/s12613-010-0119-9

中文摘要(260) PDF(7) SpringerLink

摘要:
A systematic study was conducted to comprehend the mechanism of thermal activation of silica-alumina materials by using ²⁹Si and ²⁷Al magnetic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. The reaction performance of silica-alumina-based materials with different molar ratios of Si/Al, which were thermally activated, was also investigated. With the increase in calcining temperature, the coordination of Al in metakaolin becomes four, five, and six firstly, and then transforms completely to four and six. It is indicated by identical coupled plasma optical emission spectroscopy (ICP) and NMR that, the reaction performance of monomeric silicate anions is better than that of polymeric silicate anions which are primarily cross-linked in the alkali solution. Moreover, it also shows that the thermal activation temperature, cooling method, and the molar ratio of Na/Ca have remarkable effects on the reaction performance.

Relationship between polymerization degree and cementitious activity of iron ore tailings

Zhong-lai Yi, Heng-hu Sun, Chao Li, Yin-ming Sun, Yu Li

2010, 17(1): 116-120. doi: 10.1007/s12613-010-0120-3

中文摘要(217) PDF(7) SpringerLink

摘要:
The aim of this study is to understand the relationship between the polymerization degree and cementitious activity of iron ore tailings. In light of the poor usage of iron ore tailings, stockpile samples from Tangshan were studied in terms of their ability to become cementitious materials. Compound thermal activation was used to improve the cementitious properties of the tailings, while analyzing methods, such as X-ray diffraction (XRD), infrared spectroscopy (IR), nuclear magnetic resonance (NMR), and X-ray photoelectron spectrometer (XPS), were employed to study the changes in phase and structure under different activation conditions. The results reveal clear relationships between the binding energies of Si2p and O1s, polymerization degree, and cementitious activity of iron ore tailings.

Cemented backfilling performance of yellow phosphorus slag

Jia-sheng Chen, Bin Zhao, Xin-min Wang, Qin-li Zhang, Li Wang

2010, 17(1): 121-126. doi: 10.1007/s12613-010-0121-2

中文摘要(583) PDF(9) SpringerLink

摘要:
The experiments on the cemented backfilling performance of yellow phosphorus slag, including physical-mechanical properties, chemical compositions, optimized proportion, and cementation mechanisms, were carried out to make good use of yellow phosphorus slag as well as tackle with environment problems, safety problems, geological hazards, and high-cost issues during mining in Kaiyang Phosphorus Mine Group, Guizhou. The results show that yellow phosphorus slag can be used as the cement substitute for potential coagulation property. Quicklime, hydrated lime, and other alkaline substances can eliminate the high residual phosphorus to improve the initial strength of backfilling body. The recommended proportions (mass ratio) are 1:1 (yellow phosphorus slag:phosphorous gypsum), 1:4:10 (Portland cement: yellow phosphorus slag:phosphorous gypsum), and 1:4:10 (ultrafine powder:yellow phosphorus slag:phosphorous gypsum) with 5wt% of hydrated lime addition, 60wt% of solid materials, no fly ash addition, and good rheological properties. The hydration reaction involves hydration stage, solidifying stage, and strength stage with Ca(OH)2 as the activating agent. The reaction rates of yellow phosphorus slag, Portland cement, and ultrafine powder hydration with the increase of microstructure stability and initial strength.

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2010年第17卷第1期