International Journal of Minerals, Metallurgy and Materials

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Effect of reverse flotation on magnetic separation concentrates

S. O. Bada, A. S. Afolabi, M. J. Makhula

2012, 19(8): 669-674. doi: 10.1007/s12613-012-0611-5

中文摘要(264) PDF(15) SpringerLink

摘要:
Reverse flotation studies on magnetite samples have revealed that the use of starch as a depressant of Fe-oxides has a hydrophilic effect on the surface of Fe-bearing silicates and significantly decreases Fe in the silica-rich stream when used in combination with an amine (Lilaflot D817M). In this study, the effect of reverse flotation on the optimization of products obtained from magnetic separation was investigated. Two different magnetic samples, zones 1 and 2, were milled to <75 μm and then subjected to low intensity magnetic separation (LIMS). The LIMS test conducted on the <75 μm shown an upgrade of 46.40wt% Fe, 28.40wt% SiO₂ and 2.61wt% MnO for zone 1 and 47.60wt% Fe, 29.17wt% SiO₂ and 0.50wt% MnO for zone 2. Further milling of the ore to <25 μm resulted in a higher magnetic-rich product after magnetic separation. Reverse flotation tests were conducted on the agitated magnetic concentrate feed, and the result shows a significant upgrade of Fe compared to that obtained from the non-agitated feed. Iron concentrations greater than 69%, and SiO₂ concentrations less than 2% with overall magnetite recoveries greater than 67% and 71% were obtained for zones 1 and 2, respectively.

A novel synthesis process of ETS-4 titanosilicate using commercial anatase in the absence of fluoride ions

Li-ying Liu, Wen-jun Tan, Penny Xiao, Yu-chun Zhai

2012, 19(8): 675-678. doi: 10.1007/s12613-012-0612-4

中文摘要(223) PDF(10) SpringerLink

摘要:
A novel synthesis process for ETS-4 titanosilicate using commercial anatase as the titanium source in the absence of fluoride ions was studied. Fluoride ions and traced ETS-4 seeds have important roles in forming ETS-4 structures. However, the method using ETS-4 seeds instead of fluoride ions to improve product purity and productivity is environment-friendly. ETS-4, ETS-4(NS), and ETS-4(NaF) were respectively synthesized using traced ETS-4 seeds, without seeds, and with fluoride ions. The as-synthesized samples were identified by X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis. Adsorption isotherms and adsorption heats of nitrogen and methane on the prepared ETS-4 were also measured. The results showed that ETS-4 samples could be prepared using anatase in the absence of fluoride ions, with good purity, comparable physicochemical properties, and excellent adsorption properties.

Production of pig iron from red mud waste fines using thermal plasma technology

K. Jayasankar, P. K. Ray, A. K. Chaubey, A. Padhi, B. K. Satapathy, P. S. Mukherjee

2012, 19(8): 679-684. doi: 10.1007/s12613-012-0613-3

中文摘要(325) PDF(25) SpringerLink

摘要:
Red mud, an insoluble residue produced during alkali leaching of bauxite, is considered as a low-grade iron ore containing 30% to 50% iron. The present paper deals with the use of thermal plasma technology for producing pig iron from red mud waste fines. The smelting reduction of red mud was carried out in a 35 kW DC extended arc thermal plasma reactor. Red mud was properly mixed with fluxes and graphite (fixed carbon, 99%) as a reductant as per stoichiometric requirement. The effect of various process parameters like a reductant, fluxes and smelting time on iron recovery was studied and optimized. An optimum condition for the maximum recovery of iron was obtained. A new thermal plasma process applicable to direct iron making from red mud waste fines that would achieve significant utilization of red mud was proposed.

A model for estimating the rate constant between CO₂-CO gas and molten slag containing iron oxides using optical basicity

Teng Zhang, Xiao-jun Hu, Qi-feng Shu, Kuo-Chih Chou

2012, 19(8): 685-688. doi: 10.1007/s12613-012-0614-2

中文摘要(243) PDF(9) SpringerLink

摘要:
A simple model for estimating the rate constant between CO₂-CO gas and molten slag containing iron oxides was developed using optical basicity only. In this model, the temperature dependence of the rate constant can be described by the Arrhenius law, and the activation energy can be expressed with a linear function of the slag's optical basicity. The model was applied to some molten slag systems, such as FeO, FeO-CaO, FeO-SiO₂, FeO-Na₂O, FeO-CaO-SiO₂, FeO-SiO₂-P₂O₅, FeO-SiO₂-Na₂O, and FeO-CaO-SiO₂-P₂O₅. A comparison between the predicted results and measured data showed that the model worked well.

Thermodynamic modeling of the Ge-La binary system

Miao Liu, Chang-rong Li, Zhen-min Du, Cui-ping Guo, Chun-ju Niu

2012, 19(8): 689-698. doi: 10.1007/s12613-012-0615-1

中文摘要(334) PDF(12) SpringerLink

摘要:
The Ge-La binary system was critically assessed by means of the calculation of phase diagram (CALPHAD) technique. The associate model was used for the liquid phase containing the constituent species Ge, La, Ge₃La₅, and Ge_1.7La. The terminal solid solution diamond-(Ge) with a small solubility of La was described using the substitutional model, in which the excess Gibbs energy was formulated with the Redlich-Kister equation. The compounds with homogeneity ranges, α(Ge_1.7La), β(Ge_1.7La), and (GeLa), were modeled using two sublattices as α(Ge,La)_1.7La, β(Ge,La)_1.7La, and (Ge,La)(Ge,La), respectively. The intermediate phases with no solubility ranges, Ge₄La₅, Ge₃La₄, Ge₃La₅, and GeLa₃, were treated as stoichiometric compounds. The three allotropic modifications of La, dhcp-La, fcc-La, and bcc-La, were kept as pure element phases since no solubility of Ge in La was reported. A set of self-consistent thermodynamic parameters of the Ge-La binary system was obtained. The calculation results agree well with the available experimental data from literatures.

A cellular automata model for simulating grain structures with straight and hyperbolic interfaces

A. Ramírez-López, M. Palomar-Pardavé, D. Muñoz-Negrón, C. Duran-Valencia, S. López-Ramirez, G. Soto-Cortés

2012, 19(8): 699-710. doi: 10.1007/s12613-012-0616-0

中文摘要(319) PDF(13) SpringerLink

摘要:
A description of a mathematical algorithm for simulating grain structures with straight and hyperbolic interfaces is shown. The presence of straight and hyperbolic interfaces in many grain structures of metallic materials is due to different solidification conditions, including different solidification speeds, growth directions, and delaying on the nucleation times of each nucleated node. Grain growth is a complex problem to be simulated; therefore, computational methods based on the chaos theory have been developed for this purpose. Straight and hyperbolic interfaces are between columnar and equiaxed grain structures or in transition zones. The algorithm developed in this work involves random distributions of temperature to assign preferential probabilities to each node of the simulated sample for nucleation according to previously defined boundary conditions. Moreover, more than one single nucleation process can be established in order to generate hyperbolic interfaces between the grains. The appearance of new nucleated nodes is declared in sequences with a particular number of nucleated nodes and a number of steps for execution. This input information influences directly on the final grain structure (grain size and distribution). Preferential growth directions are also established to obtain equiaxed and columnar grains. The simulation is done using routines for nucleation and growth nested inside the main function. Here, random numbers are generated to place the coordinates of each new nucleated node at each nucleation sequence according to a solidification probability. Nucleation and growth routines are executed as a function of nodal availability in order to know if a node will be part of a grain. Finally, this information is saved in a two-dimensional computational array and displayed on the computer screen placing color pixels on the corresponding position forming an image as is done in cellular automaton.

Austenite grain growth behavior of Q1030 high strength welded steel

Rong-ting Xiao, Hao Yu, Ping Zhou

2012, 19(8): 711-716. doi: 10.1007/s12613-012-0617-z

中文摘要(269) PDF(12) SpringerLink

摘要:
The austenite grain growth behavior of Q1030 steel was studied under different heating conditions. The austenite grain size increases with the heating temperature and holding time increasing. Austenite grains grow in an exponential manner with rising heating temperature and in a parabolic manner with prolonging holding time. A mathematical model for describing the austenite grain growth behavior of Q1030 steel was obtained on the basis of experimental results using regression analysis. When the heating temperatures lie between 1000 and 1100℃ at a certain holding time, abnormal grain growth appears, which causes mixed grains in Q1030 steel.

Corrosion inhibition of stainless steel by a sulfate-reducing bacteria biofilm in seawater

Fu-shao Li, Mao-zhong An, Dong-xia Duan

2012, 19(8): 717-725. doi: 10.1007/s12613-012-0618-y

中文摘要(397) PDF(8) SpringerLink

摘要:
Corrosion inhibition of stainless steel due to a sulfate-reducing bacteria (SRB) biofilm in seawater was studied. By atomic force microscopy, a layer of fish-scale-like biofilm was found to form as stainless steel coupons were exposed to the culture media with SRB, and this biofilm grew more and more compact. As a result, coupons' surface under the biofilm turned irregular less slowly than that exposed to the sterilized culture media. Then, physicoelectric characteristics of the electrode/biofilm/solution interface were investigated by electrochemical impedance spectroscopy (EIS), and the coverage of the biofilm as well as the relative irregularity of coupons' surface was also recorded by EIS spectra. Finally, anodic cyclic polarization results further demonstrated the protective property of the biofilm. Therefore, in estimation of SRB-implicated corrosion of stainless steel, not only the detrimental SRB metabolites but also the protective SRB biofilm as well should be taken into account.

Corrosion behaviors of thermally grown oxide films on Fe-based bulk metallic glasses

Hong-xiang Li, Shan-lin Wang, Yeonuk Jeong, Seonghoon Yi

2012, 19(8): 726-732. doi: 10.1007/s12613-012-0619-x

中文摘要(229) PDF(8) SpringerLink

摘要:
Oxide films formed on the surfaces of Fe-based bulk metallic glasses in the temperature range between 373 K and 573 K were characterized and their effects on the corrosion behaviors were investigated by microstructural and electrochemical analysis. The oxide film formed at 573 K is iron-rich oxide and it exhibits an n-type semiconductor at a higher potential than 0.35 V and a p-type semiconductor at a lower potential than 0.35 V. Capacitance measurements show that the donor density decreases with the increase in oxidation temperature, while the thickness of the space charge layer increases with the oxidation temperature rising. The result of immersion tests shows that the mass loss rate increases with the oxidation temperature rising. Therefore, the correlation between microstructure and corrosion resistance needs to be proposed because the corrosion resistance is deteriorated with the development of the oxide films.

Abrasive wear behavior of cast iron coatings plasma-sprayed at different mild steel substrate temperatures

Ya-zhe Xing, Qiu-lan Wei, Chao-ping Jiang, Jian-min Hao

2012, 19(8): 733-738. doi: 10.1007/s12613-012-0620-4

中文摘要(337) PDF(8) SpringerLink

摘要:
Three kinds of cast iron coatings were prepared by atmospheric plasma spraying. During the spraying, the mild steel substrate temperature was controlled to be averagely 50, 180, and 240℃, respectively. Abrasive wear tests were conducted on the coatings under a dry friction condition. It is found that the abrasive wear resistance is enhanced with the substrate temperature increasing. SEM observations show that the wear losses of the coatings during the wear tests mainly result from the spalling of the splats. Furthermore, the improved wear resistance of the coatings mainly owes to the formation of oxides and the enhancement in the mechanical properties with the substrate temperature increasing.

Microstructural evolution and intermetallic formation in Al-8wt% Si-0.8wt% Fe alloy due to grain refiner and modifier additions

Amir Hassani, Khalil Ranjbar, Sattar Sami

2012, 19(8): 739-746. doi: 10.1007/s12613-012-0621-3

中文摘要(289) PDF(13) SpringerLink

摘要:
An alloy of Al-8wt% Si-0.8wt% Fe was cast in a metallic die, and its microstructural changes due to Ti-B refiner and Sr modifier additions were studied. Apart from usual refinement and modification of the microstructure, some mutual influences of the additives took place, and no mutual poisoning effects by these additives, in combined form, were observed. It was noticed that the dimensions of the iron-rich intermetallics were influenced by the additives causing them to become larger. The needle-shaped intermetallics that were obtained from refiner addition became thicker and longer when adding the modifier. It was also found that α-Al and eutectic silicon phases preferentially nucleate on different types of intermetallic compounds. The more iron content of the intermetallic compounds and the more changes in their dimensions occurred. Formation of the shrinkage porosities was also observed.

Eutectic reaction and cored dendritic morphology in yttrium doped Zr-based amorphous alloys

Wei-jie Peng, Yong Zhang

2012, 19(8): 747-751. doi: 10.1007/s12613-012-0622-2

中文摘要(275) PDF(7) SpringerLink

摘要:
The microalloying effect of yttrium on the crystallization behaviors of (Zr_0.525Al_0.10Ti_0.05Cu_0.179Ni_0.146)_100-x Y_x, and (Zr_0.55Al_0.15-Ni_0.10Cu_0.20)_100-x Y_x (x=0, 0.4, and 1, thus the two alloy systems were denoted as Zr52.5, Zr52.5Y0.4, Zr52.5Y1, and Zr55, Zr55Y0.4, Zr55Y1, respectively) was studied. Transmission electron microscopy (TEM) results suggested that the crystalline phases were different in the two Zr-based alloys and with different yttrium contents. ZrNi-phase and Al₃Zr₅ phase precipitations can be well explained by the mechanisms of nucleation and growth. Al₃Zr₅ phase is mainly formed by a peritectic-like reaction, while ZrNi-phase by a eutectic reaction. The contents of elements Y, Al, and Ti may dominate the reaction types. The orientation relationship between Y₂O₃ particles and Al₃Zr₅ phase is also discussed.

Effect of modified elastomeric binders on the electrochemical properties of silicon anodes for lithium-ion batteries

Tao Li, Juan-yu Yang, Shi-gang Lu

2012, 19(8): 752-756. doi: 10.1007/s12613-012-0623-1

中文摘要(356) PDF(13) SpringerLink

摘要:
Silicon has been investigated intensively as a promising anode material for rechargeable lithium-ion batteries. The choice of a binder is very important to solve the problem of the large capacity fade observed along cycling. The effect of modified elastomeric binders on the electrochemical performance of crystalline nano-silicon powders was studied. Compared with the conventional binder (polyvinylidene fluoride (PVDF)), Si electrodes using the elastomeric styrene butadiene rubber (SBR) and sodium carboxymethyl cellulose (SCMC) combined binder show an improved cycling performance. The reversible capacity of the Si electrode with the SCMC/SBR binder is as high as 2221 mA·h/g for 30 cycles in a voltage window between 0.005 and 2 V. The structure changes from SEM images of the silicon electrodes with different binders were used to explore the property improvement.

Phase analysis and thermal conductivity of in situ O'-sialon/β-Si₃N₄ composites

Xiao-lei Li, Xiao-liang Chen, Hui-ming Ji, Xiao-hong Sun, Ling-ge Zhao

2012, 19(8): 757-761. doi: 10.1007/s12613-012-0624-0

中文摘要(315) PDF(10) SpringerLink

摘要:
Typical O'-sialon-based ceramics, with a formula of Si_2-xAl_xO_1+xN_2-x, where x was set as 0.25, were fabricated by in-situ synthesis. Si₃N₄, Al₂O₃, and SiO₂ powders were used as raw materials, and MgO and Y₂O₃ were added as sintering additives. All the samples were sintered at different temperatures under a nitrogen pressure of 0.25-0.30 MPa, and their microstructure, phase content, and thermal conductivity were evaluated. The effects of O'-sialon and β-Si₃N₄ on the thermal conductivity were analyzed by numerical calculation in detail. In the case of the similar porosity, the thermal conductivity of O'-sialon-based ceramics decreased with the ratio of O'-sialon/β-Si₃N₄ increasing. When the ratio was 12, the thermal conductivity of O'-sialon ceramics sintered at 1360℃ was 1.197 W·m^-1·K^-1.

Preparation and characterization of barium strontium titanate/silicon nanoporous pillar array composite thin films by a sol-gel method

Shun-hua Xiao, Wei-fen Jiang

2012, 19(8): 762-767. doi: 10.1007/s12613-012-0625-z

中文摘要(252) PDF(12) SpringerLink

摘要:
Barium strontium titanate (Ba_0.5Sr_0.5TiO₃, BST)/silicon nanoporous pillar array (Si-NPA) thin films were prepared by a spin-coating/annealing technique based on Si-NPA with micro/nano-structure. Both the isomer conversion of acetylacetone and the network structure combined by enol and Ti-alkoxide facilitate the formation of the BST sol and the subsequent crystallization. Before the perovskite BST begins to form, the intermediate phase (Ba,Sr)Ti₂O₅CO₃ is found. The boundary between BST and Si-NPA is of clarity and little interface diffusion, disclosing that Si-NPA is an ideal template substrate in the preparation of multifunctional composite films.

Structure and properties of NASICON synthesized by two different zirconium salts

Heng-yao Dang, Xing-min Guo, Yong-ping Huang, Jiang-qi Rong

2012, 19(8): 768-773. doi: 10.1007/s12613-012-0626-y

中文摘要(234) PDF(9) SpringerLink

摘要:
ZrOCl₂·8H₂O and ZrO(NO₃)₂·2H₂O were used respectively to synthesize a NASICON solid electrolyte by a sol-gel method. The structure and properties of two samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). The crystal structure was investigated by the Rietveld refinement. It is found that both the samples contain a monoclinic C2/c phase as the main conductive phase with the lattice parameters of a=1.56312 nm, b=0.90784 nm and c=0.92203 nm, though a small amount of rhombohedral phase is also detected in the final product. The sample synthesized by ZrO(NO₃)2·2H₂O contains more monoclinic phase (89.48wt%) than that synthesized by ZrOCl₂·8H₂O (74.91wt%). As expected, the ionic conductivity of the latter is higher than that of the former; however, the activation energy of the latter (0.37 eV) is slightly higher than that of the former (0.35 eV).

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2012年第19卷第8期