International Journal of Minerals, Metallurgy and Materials

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Thermodynamics and density functional theory study of potassium dichromate interaction with galena

Jian-Hua Chen, Xian-Hao Long, Li-Hong Lan, Qian He

2014, 21(10): 947-954. doi: 10.1007/s12613-014-0994-6

中文摘要(327) PDF(9) SpringerLink

摘要:
The adsorption heat and reaction rate constant of potassium dichromate on the surface of galena were studied. The results indicate that potassium dichromate tends to adsorption on the galena surface. The reaction order is only 0.08385, suggesting that the concentration of potassium dichromate has little influence on its adsorption on the galena surface. In addition, the simulation of CrO₄²⁻ adsorption on the PbS (100) surface in the absence and presence of O₂ was carried out by density functional theory (DFT). The calculated results show that CrO₄²⁻ species adsorb energetically at the Pb-S bond site, and the presence of O₂ can enhance this adsorption.

Ferronickel enrichment by fine particle reduction and magnetic separation from nickel laterite ore

Xiao-hui Tang, Run-zao Liu, Li Yao, Zhi-jun Ji, Yan-ting Zhang, Shi-qi Li

2014, 21(10): 955-961. doi: 10.1007/s12613-014-0995-5

中文摘要(368) PDF(16) SpringerLink

摘要:
Ferronickel enrichment and extraction from nickel laterite ore were studied through reduction and magnetic separation. Reduction experiments were performed using hydrogen and carbon monoxide as reductants at different temperatures (700–1000°C). Magnetic separation of the reduced products was conducted using a SLon-100 cycle pulsating magnetic separator (1.2 T). Composition analysis indicates that the nickel laterite ore contains a total iron content of 22.50wt% and a total nickel content of 1.91wt%. Its mineral composition mainly consists of serpentine, hortonolite, and goethite. During the reduction process, the grade of nickel and iron in the products increases with increasing reduction temperature. Although a higher temperature is more favorable for reduction, the temperature exceeding 1000°C results in sintering of the products, preventing magnetic separation. After magnetic separation, the maximum total nickel and iron concentrations are 5.43wt% and 56.86wt%, and the corresponding recovery rates are 84.38% and 53.76%, respectively.

Influence of gangue existing states in iron ores on the formation and flow of liquid phase during sintering

Guo-liang Zhang, Sheng-li Wu, Shao-guo Chen, Bo Su, Zhi-gang Que, Chao-gang Hou

2014, 21(10): 962-968. doi: 10.1007/s12613-014-0996-4

中文摘要(257) PDF(9) SpringerLink

摘要:
Gangue existing states largely affect the high-temperature characteristics of iron ores. Using a micro-sintering method and scanning electron microscopy, the effects of gangue content, gangue type, and gangue size on the assimilation characteristics and fluidity of liquid phase of five different iron ores were analyzed in this study. Next, the mechanism based on the reaction between gangues and sintering materials was unraveled. The results show that, as the SiO₂ levels increase in the iron ores, the lowest assimilation temperature (LAT) decreases, whereas the index of fluidity of liquid phase (IFL) increases. Below 1.5wt%, Al₂O₃ benefits the assimilation reaction, but higher concentrations proved detrimental. Larger quartz particles increase the SiO₂ levels at the local reaction interface between the iron ore and CaO, thereby reducing the LAT. Quartz-gibbsite is more conductive to assimilation than kaolin. Quartz-gibbsite and kaolin gangues encourage the formation of liquid-phase low-Al₂O₃-SFCA with high IFL and high-Al₂O₃-SFCA with low IFL, respectively.

Textural changes in metallurgical coke prepared with polyethylene

Stanislav S. Gornostayev, Jyrki J. Heino, Tommi M. T. Kokkonen, Hannu T. Makkonen, Satu M. M. Huttunen, Timo M. J. Fabritius

2014, 21(10): 969-973. doi: 10.1007/s12613-014-0997-3

中文摘要(225) PDF(7) SpringerLink

摘要:
The effect of high-density polyethylene (HDPE) on the textural features of experimental coke was investigated using polarized-light optical microscopy and wavelet-based image analysis. Metallurgical coke samples were prepared in a laboratory-scale furnace with 2.5%, 5.0%, 7.5%, 10.0%, and 12.5% HDPE by mass, and one sample was prepared by 100% coal. The amounts and distribution of textures (isotropic, mosaic and banded) and pores were obtained. The calculations reveal that the addition of HDPE results in a decrease of mosaic texture and an increase of isotropic texture. Ethylene formed from the decomposition of HDPE is considered as a probable reason for the texture modifications. The approach used in this study can be applied to indirect evaluation for the reactivity and strength of coke.

Effect of tunnel structure on the specific capacitance of etched aluminum foil

Ning Peng, Li-Bo Liang, Ye-Dong He, Hong-Zhou Song, Xiao-Fei Yang, Xiao-Yu Cai

2014, 21(10): 974-979. doi: 10.1007/s12613-014-0998-2

中文摘要(285) PDF(12) SpringerLink

摘要:
The morphology of etched aluminum foil was observed using scanning electron microscopy, which led to the establishment of a cylindrical model and two merged models, considering the fixed weight loss of etching. The maximum of specific capacitance and the corresponding optimum values for tunnel sizes at various anodization voltages were predicted. The increased size distribution and taper of tunnels were demonstrated to decrease the specific capacitance, whereas the addition of polymeric additive into the tunnel widening solution was demonstrated to increase the capacitance. The formation of merged tunnels on the etched aluminum surface, irrespective of the presence of row-merged tunnels or cluster-merged tunnels, resulted in a dramatic decrease in the specific capacitance. It is concluded that, enhancing the uniformity of tunnel size and distribution and avoiding the formation of merged tunnels are the effective approach to achieving the higher capacitance for the tunnel etched and formed aluminum foil.

Effect of partition coefficient on microsegregation during solidification of aluminium alloys

M. H. Avazkonandeh-Gharavol, M. Haddad-Sabzevar, H. Fredriksson

2014, 21(10): 980-989. doi: 10.1007/s12613-014-0999-1

中文摘要(287) PDF(10) SpringerLink

摘要:
In the modeling of microsegregation, the partition coefficient is usually calculated using data from the equilibrium phase diagrams. The aim of this study was to experimentally and theoretically analyze the partition coefficient in binary aluminum-copper alloys. The samples were analyzed by differential thermal analysis (DTA), which were melted and quenched from different temperatures during solidification. The mass fraction and composition of phases were measured by image processing and scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectroscopy (EDS) unit. These data were used to calculate as the experimental partition coefficients with four different methods. The experimental and equilibrium partition coefficients were used to model the concentration profile in the primary phase. The modeling results show that the profiles calculated by the experimental partition coefficients are more consistent with the experimental profiles, compared to those calculated using the equilibrium partition coefficients.

Damage prediction of 7025 aluminum alloy during equal-channel angular pressing

M. Ebrahimi, Sh. Attarilar, C. Gode, F. Djavanroodi

2014, 21(10): 990-998. doi: 10.1007/s12613-014-1000-z

中文摘要(285) PDF(8) SpringerLink

摘要:
Equal-channel angular pressing (ECAP) is a prominent technique that imposes severe plastic deformation into materials to enhance their mechanical properties. In this research, experimental and numerical approaches were utilized to investigate the mechanical properties, strain behavior, and damage prediction of ECAPed 7025 aluminum alloy in various conditions, such as die channel angle, outer corner angle, and friction coefficient. Experimental results indicate that, after the first pass, the yield strength, ultimate tensile strength, and hardness magnitude are improved by approximately 95%, 28%, and 48.5%, respectively, compared with the annealed state, mainly due to grain refinement during the deformation. Finite element analysis shows that the influence of die channel angle is more important than that of outer corner angle or friction coefficient on both the strain behavior and the damage prediction. Also, surface cracks are the main cause of damage during the ECAP process for every die channel angle except for 90°; however, the cracks initiated from the neighborhood of the central regions are the possible cause of damage in the ECAPed sample with the die channel angle of 90°.

Mechanical, electrical, and thermal properties of the directionally solidified Bi-Zn-Al ternary eutectic alloy

M. Şahin, E. Çadırlı

2014, 21(10): 999-1008. doi: 10.1007/s12613-014-1001-y

中文摘要(200) PDF(7) SpringerLink

摘要:
A Bi-2.0Zn-0.2Al (wt%) ternary eutectic alloy was prepared using a vacuum melting furnace and a casting furnace. The samples were directionally solidified upwards at a constant growth rate (V = 18.4 μm/s) under different temperature gradients (G = 1.15–3.44 K/mm) and at a constant temperature gradient (G = 2.66 K/mm) under different growth rates (V = 8.3–500 μm/s) in a Bridgman-type directional solidification furnace. The dependence of microstructure parameter (λ) on the solidification parameters (G and V) and that of the microhardness (Hv) on the microstructure and solidification parameters were investigated. The resistivity (ρ) measurements of the studied alloy were performed using the standard four-point-probe method, and the temperature coefficient of resistivity (α) was calculated from the ρ-T curve. The enthalpy (ΔH) and the specific heat (C_p) values were determined by differential scanning calorimetry analysis. In addition, the thermal conductivities of samples, obtained using the Wiedemann-Franz and Smith-Palmer equations, were compared with the experimental results. The results revealed that, the thermal conductivity values obtained using the Wiedemann-Franz and Smith-Palmer equations for the Bi-2.0Zn-0.2Al (wt%) alloy are in the range of 5.2–6.5 W/Km and 15.2–16.4 W/Km, respectively.

Non-monotonic influence of a magnetic field on the electrochemical behavior of Fe₇₈Si₉B₁₃ glassy alloy in NaOH and NaCl solutions

Hong-di Zhang, Xiao-yu Li, Jing Pang, Li-juan Yin, Hai-jian Ma, Ying-jie Li, Yan Liu, Wei-min Wang

2014, 21(10): 1009-1018. doi: 10.1007/s12613-014-1002-x

中文摘要(241) PDF(8) SpringerLink

摘要:
The corrosion behavior and microstructure of Fe₇₈Si₉B₁₃ glassy alloy in NaOH and NaCl solutions under a 0.02-T magnetic field were investigated through electrochemical testing and scanning electron microscopy (SEM). The current-density prepeak (PP) in the anodic polarization curves in low-concentration NaOH solutions (classified as type I) tends to disappear when the NaOH concentration is increased to 0.4 mol/L and the magnetic field is applied. Under the magnetic field, the height of the second current-density peak is increased in low-concentration NaOH solutions (type I) but decreased in high-concentration NaOH solutions (type II). The non-monotonic effect of the magnetic field was similarly observed in the case of polarization curves of samples measured in NaCl solutions. Ring-like corroded patterns and round pits are easily formed under the magnetic field in NaOH and NaCl solutions. These experimental results were discussed in terms of the magnetohydrodynamic (MHD) effect.

Dielectric, piezoelectric, and ferroelectric properties of lanthanum-modified PZTFN ceramics

Arvind Kumar, S. K. Mishra

2014, 21(10): 1019-1027. doi: 10.1007/s12613-014-1003-9

中文摘要(319) PDF(9) SpringerLink

摘要:
Specimens of Pb_1−1.5xLa_x(Zr_0.53Ti_0.47)_1−y−zFe_yNb_zO₃(x = 0, 0.004, 0.008, 0.012, and 0.016, y = z = 0.01) (PZTFN) ceramics were synthesized by a semi-wet route. In the present study, the effect of La doping was investigated on the structural, microstructural, dielectric, piezoelectric, and ferroelectric properties of the ceramics. The results show that, the tetragonal (space group P4mm) and rhombohedral (space group R3c) phases are observed to coexist in the sample at x = 0.012. Microstructural investigations of all the samples reveal that La doping inhibits grain growth. Doping of La into PZTFN improves the dielectric, ferroelectric, and piezoelectric properties of the ceramics. The hysteresis loops of all specimens exhibit nonlinear behavior. The dielectric, piezoelectric and ferroelectric properties show a maximum response at x ≥ 0.012, which corresponds to the morphotropic phase boundary (MPB).

Morphology, crystal structure and hydration of calcined and modified anhydrite

Xiao-qing Niu, Ji-chun Chen

2014, 21(10): 1028-1032. doi: 10.1007/s12613-014-1004-8

中文摘要(277) PDF(9) SpringerLink

摘要:
The effects of calcination and modification on the morphology (shapes and textures) and crystal structure of anhydrite powders were studied. The results show that, calcination at 100°C causes anhydrite to disintegrate into smaller crystals, accompanied by a slight increase in d-spacing. Without calcination and modification, the solidification time and curing time of anhydrite are 15 and 77 h, respectively. After the treatment, however, the solidification time and curing time are shortened significantly to 9.5 and 14 min, respectively. The compressive and flexural strengths of hydration products made from the treated anhydrite reach 10.2 and 2.0 MPa, respectively. The much shorter solidification and curing time make it possible to use anhydrite as a building and construction material.

Hydroxyapatite/alumina nanocrystalline composite powders synthesized by sol-gel process for biomedical applications

S. Khorsand, M. H. Fathi, S. Salehi, S. Amirkhanlou

2014, 21(10): 1033-1036. doi: 10.1007/s12613-014-1005-7

中文摘要(322) PDF(9) SpringerLink

摘要:
Hydroxyapatite/alumina nanocrystalline composite powders needed for various biomedical applications were successfully synthesized by sol-gel process. Structural and morphological investigations of the prepared composite powders were performed using X-ray diffractometer (XRD), scanning electron microscopy (SEM), X’Pert HighScore software, and Clemex Vision image analysis software. The results show that the crystallite size of the obtained composite powders is in the range of 25 to 90 nm. SEM evaluation shows that the obtained composite powders have a porous structure, which is very useful for biomedical applications. The spherical nanoparticles in the range of 60 to 800 nm are embedded in the agglomerated clusters of the prepared composite powders.

Fabrication of an r-Al₂Ti intermetallic matrix composite reinforced with α-Al₂O₃ ceramic by discontinuous mechanical milling for thermite reaction

A. Mosleh, M. Ehteshamzadeh, R. Taherzadeh Mousavian

2014, 21(10): 1037-1043. doi: 10.1007/s12613-014-1006-6

中文摘要(263) PDF(7) SpringerLink

摘要:
In this study, a powder mixture with an Al/TiO₂ molar ratio of 10/3 was used to form an r-Al₂Ti intermetallic matrix composite (IMC) reinforced with α-Al₂O₃ ceramic by a novel milling technique, called discontinuous mechanical milling (DMM) instead of milling and ignition of the produced thermite. The results of energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) of samples with varying milling time indicate that this fabrication process requires considerable mechanical energy. It is shown that Al₂Ti-Al₂O₃ IMC with small grain size was produced by DMM after 15 h of ball milling. Peaks for γ-TiAl as well as Al₂Ti and Al₂O₃ are observed in XRD patterns after DMM followed by heat treatment. The microhardness of the DMM-treated composite produced after heat treatment was higher than Hv 700.

Erratum to: Modeling the effects of ore properties on water recovery in the thickening process

Majid Unesi, Mohammad Noaparast, Seiyd Ziaedin Shafaei, Esmaeil Jorjani

2014, 21(10): 1044-1044. doi: 10.1007/s12613-014-1007-5

中文摘要(210) PDF(14) SpringerLink

摘要: