International Journal of Minerals, Metallurgy and Materials

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Chemical leaching of an Indian bituminous coal and characterization of the products by vibrational spectroscopic techniques

B. Manoj, A. G. Kunjomana

2012, 19(4): 279-283. doi: 10.1007/s12613-012-0551-0

中文摘要(255) PDF(9) SpringerLink

摘要:
High volatile bituminous coal was demineralized by a chemical method. The vibrations of the "aromatics" structure of graphite, crystalline or non-crystalline, were observed in the spectra at the 1600 cm^-1 region. The band at 1477 cm^-1 is assigned as V_R band, the band at 1392 cm^-1 as V_L band and the band at 1540 cm^-1 as G_R band. Graphite structure remains after chemical leaching liberates oxygenated functional groups and mineral groups. The silicate bands between 1010 and 1100 cm^-1 are active in the infrared (IR) spectrum but inactive in the Raman spectrum. Absorption arising from C-H stretching in alkenes occurs in the region of 3000 to 2840 cm^-1. Raman bands because of symmetric stretch of water molecules were also observed in the spectrum at 3250 cm^-1 and 3450 cm^-1. Scanning electron microscopy analysis revealed the presence of a graphite layer on the surface. Leaching of the sample with hydrofluoric acid decreases the mineral phase and increases the carbon content. The ash content is reduced by 84.5wt% with leaching from its initial value by mainly removing aluminum and silicate containing minerals.

Influence of the roughness and shape of quartz particles on their flotation kinetics

Mehdi Rahimi, Fahimeh Dehghani, Bahram Rezai, Mohammad Reza Aslani

2012, 19(4): 284-289. doi: 10.1007/s12613-012-0552-z

中文摘要(275) PDF(15) SpringerLink

摘要:
Surface roughness and shape play an important role on the behavior of particles in various processes such as flotation. In this research, the influence of different grinding methods on the surface roughness and shape characteristics of quartz particles as well as the effect of these parameters on the flotation of the particles was investigated. The surface roughness of the particles was determined by measuring their specific surface area via the gas adsorption method. The shape characteristics of the particles were measured and calculated by images obtained by scanning electron microscopy via an image analysis system. The flotation kinetics was determined using a laboratory flotation cell. The results showed that the particles of rod mill products have higher roughness and elongation ratio and lower roundness than the particles of ball mill products. The flotation kinetics constant of the particles increased with their surface roughness increasing. Particles with higher elongation and lower roundness indicated higher floatability. In addition, the influence of the surface roughness on the flotation kinetics was greater than that of shape parameters.

Optimization of operation conditions for extracting lithium ions from calcium chloride-type oil field brine

Hong-jun Yang, Qing-hai Li, Bing Li, Feng-qin Guo, Qing-fen Meng, Wu Li

2012, 19(4): 290-294. doi: 10.1007/s12613-012-0553-y

中文摘要(277) PDF(13) SpringerLink

摘要:
Al(OH)3 was prepared to extract lithium ions from calcium chloride-type oil field brine. The influences of four factors, namely temperature, Al³⁺/Li⁺ molar ratio, OH^-/Al³⁺ molar ratio, and contact time between Al(OH)₃ and the brine, on the yield of lithium ions were investigated. It is found that their optimal values are 35℃, 4.5, 2.6, and 6 h, respectively. In the course of the experiment, the apparent pH value was observed. The results reveal that the apparent pH value has no remarkable influence on the yield of lithium ions. Meanwhile, the effects of the concentrations of calcium ions and magnesium ions in the brine on lithium recovery were studied. The results indicate that calcium ions have minor negative influence on the yield of lithium ions under optimal conditions, and magnesium ions slightly influence the yield of lithium ions.

Characteristics of inclusions in high-Al steel during electroslag remelting process

Cheng-bin Shi, Xi-chun Chen, Han-jie Guo

2012, 19(4): 295-302. doi: 10.1007/s12613-012-0554-x

中文摘要(272) PDF(16) SpringerLink

摘要:
The characteristics of inclusions in high-Al steel refined by electroslag remelting (ESR) were investigated by image analysis, scanning electron microscopy (SEM), and energy-dispersive spectrometry (EDS). The results show that the size of almost all the inclusions observed in ESR ingots is less than 5 μm. Inclusions smaller than 3 μm take nearly 75% of the total inclusions observed in each ingot. Inclusions observed in ESR ingots are pure AlN as dominating precipitates and some fine spherical Al₂O₃ inclusions with a size of 1 μm or less. It is also found that protective gas operation and slag deoxidation treatment during ESR process have significant effects on the number of inclusions smaller than 2 μm but little effects on that of inclusions larger than 2 μm. Thermodynamic calculations show that AlN inclusions are unable to precipitate in the liquid metal pool under the present experimental conditions, while the precipitation of AlN inclusions could take place at the solidifying front due to the microsegregation of Al and N in liquid steel during solidification.

Comprehensive model for a slag bath in electroslag remelting process with a current-conductive mould

Fu-bin Liu, Xi-min Zang, Zhou-hua Jiang, Xin Geng, Man Yao

2012, 19(4): 303-311. doi: 10.1007/s12613-012-0555-9

中文摘要(293) PDF(13) SpringerLink

摘要:
A mathematical model was developed to describe the interaction of multiple physical fields in a slag bath during electroslag remelting (ESR) process with a current-conductive mould. The distributions of current density, magnetic induction intensity, electromagnetic force, Joule heating, fluid flow and temperature were simulated. The model was verified by temperature measurements during remelting 12CrMoVG steel with a slag of 50wt%-70wt% CaF₂, 20wt%-30wt% CaO, 10wt%-20wt% Al₂O₃, and ≤ 10wt% SiO₂ in a 600 mm diameter current-conductive mould. There is a good agreement between the calculated temperature results and the measured data in the slag bath. The calculated results show that the maximum values of current density, electromagnetic force and Joule heating are in the region between the corner electrodes and the conductivity element. The characteristics of current density distribution, magnetic induction intensity, electromagnetic force, Joule heating, velocity patterns and temperature profiles in the slag bath during ESR process with current-conductive mould were analyzed.

Lateral growth rate of δ phase during solidification of Fe-0.15wt%C-0.8wt%Mn steel

Guo-wei Chang, Shu-ying Chen, Qing-chun Li, Xu-dong Yue, Guang-can Jin

2012, 19(4): 312-316. doi: 10.1007/s12613-012-0556-8

中文摘要(294) PDF(9) SpringerLink

摘要:
Taking Fe-0.15wt%C-0.8wt%Mn steel as the research object, in situ observations of the δ phase growth process during solidification were conducted by using a high-temperature confocal scanning laser microscope (HTCSLM). The effects of the solid/liquid (S/L) interface's shape, temperature, and curvature radius on the lateral growth rate of δ phase were investigated in detail, and the relational expression among the lateral growth rate of δ phase, temperature, and curvature radius of column-shaped δ phase was deduced for the carbon steel during solidification. The results indicate the growth rate of the concave-shaped S/L interface is larger than that of the convex-shaped S/L interface during the beginning growth of δ phase, but these two kinds of growth rates gradually approach with proceeding in solidification. The calculated lateral growth rate of δ phase is consistent with the experimental result at a cooling rate of 0.045℃/s.

Effect of superplastic deformation on the bonding property of 00Cr25Ni7Mo3N duplex stainless steel

Xiao-hui Chen, Xue-ping Ren, Hui Xu, Jian-guo Tong, Hai-yan Zhang

2012, 19(4): 317-321. doi: 10.1007/s12613-012-0557-7

中文摘要(248) PDF(9) SpringerLink

摘要:
The superplastic deformation diffusion bonding of 00Cr25Ni7Mo3N duplex stainless steel was performed on a hot simulator. The microstructure of the bonding interface was characterized by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The mechanical properties of the specimen were investigated by a shear strength test. The results indicated that the shear strength was improved with the increase of superplastic deformation reduction. When the deformation reduction was up to 50%, the shear strength of the specimen achieved 417 Mpa, approaching to that of the base metal. In addtion, the superplastic diffusion bonding technique was not very sensitive to surface roughness levels. When the surface roughness of the bonding specimen surpassed 0.416 μm (level G2), the shear strength achieved at least 381 MPa.

Antibacterial properties and corrosion resistance of AISI 420 stainless steels implanted by silver and copper ions

Hong-wei Ni, Han-shuang Zhang, Rong-sheng Chen, Wei-ting Zhan, Kai-fu Huo, Zhen-yu Zuo

2012, 19(4): 322-327. doi: 10.1007/s12613-012-0558-6

中文摘要(322) PDF(11) SpringerLink

摘要:
Silver or copper ions are often chosen as antibacterial agents. But a few reports are concerned with these two antibacterial agents for preparation of antibacterial stainless steel (SS). The antibacterial properties and corrosion resistance of AISI 420 stainless steel implanted by silver and copper ions were investigated. Due to the cooperative antibacterial effect of silver and copper ions, the Ag/Cu implanted SS showed excellent antibacterial activities against both Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) at a total implantation dose of 2×10¹⁷ ions/cm². Electrochemical polarization curves revealed that the corrosion resistance of Ag/Cu implanted SS was slightly enhanced as compared with that of un-implanted SS. The implanted layer was characterized by X-ray photoelectron spectroscopy (XPS). Core level XPS spectra indicate that the implanted silver and copper ions exist in metallic state in the implanted layer.

Electrochemical behavior of 304 stainless steel with electrodeposited niobium as PEMFC bipolar plates

Cheng-hao Liang, Cai-hong Cao, Nai-bao Huang

2012, 19(4): 328-332. doi: 10.1007/s12613-012-0559-5

中文摘要(304) PDF(7) SpringerLink

摘要:
In order to enhance the corrosion resistance of 304 stainless steel, niobium was electrodeposited on its surface in air- and water-stable ionic liquids. The electrochemical behaviors of bare and niobium-coated 304 stainless steel were evaluated by electrochemical tests in a simulated proton exchange membrane fuel cell (PEMFC) environment. The results showed that niobium could be electrodeposited on the surface of 304 stainless steel from ionic liquids, and a smooth and strong chemical inert compound film was obtained on the surface of 304 stainless steel, which was mainly composed of NbO and Nb₂O₅. The thin composite film acted as a barrier and remarkably improved the corrosion resistance of 304 stainless steel in the PEMFC environment.

Microstructural evolution and mechanical properties of nanostructured Cu-Al-Ni shape memory alloys

M. Izadinia, K. Dehghani

2012, 19(4): 333-338. doi: 10.1007/s12613-012-0560-z

中文摘要(322) PDF(8) SpringerLink

摘要:
The melt spinning technique, with an applied cooling rate of about 10⁶K/s, was used to produce a nanostructured Cu+13.2Al+ 5.1Ni (in wt%) shape memory alloy. The properties of nanostructured ribbons were then compared with those of conventional coarse structure. The microstructural evolution was characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD) techniques. Microhardness measurements indicate a two-fold increase in hardness because of the produced nanostructure. Comparing to its coarse structure, the nanostructured Cu-Al-Ni shape memory alloy exhibited the enhanced mechanical properties including a ductility of 6.5% and a pronounced plateau in the stress-strain curve.

Microstructure and mechanical properties of BFe10 cupronickel alloy tubes fabricated by a horizontal continuous casting with heating-cooling combined mold technology

Jun Mei, Xin-hua Liu, Jian-xin Xie

2012, 19(4): 339-347. doi: 10.1007/s12613-012-0561-y

中文摘要(236) PDF(10) SpringerLink

摘要:
A new horizontal continuous casting method with heating-cooling combined mold (HCCM) technology was explored for fabricating high-quality thin-wall cupronickel alloy tubes used for heat exchange pipes. The microstructure and mechanical properties of BFe10 cupronickel alloy tubes fabricated by HCCM and traditional continuous casting (cooling mold casting) were comparatively investigated. The results show that the tube fabricated by HCCM has smooth internal and external surfaces without any defects, and its internal and external surface roughnesses are 0.64 μm and 0.85 μm, respectively. The tube could be used for subsequent cold processing without other treatments such as surface planning, milling and acid-washing. This indicates that HCCM can effectively reduce the process flow and improve the production efficiency of a BFe10 cupronickel alloy tube. The tube has columnar grains along its axial direction with a major casting texture of {012} <621>. Compared with cooling mold casting (δ=36.5%), HCCM can improve elongation (δ=46.3%) by 10% with a slight loss of strength, which indicates that HCCM remarkably improves the cold extension performance of a BFe10 cupronickel alloy tube.

Enhanced compression ductility of stoichiometric NiAl at room temperature by Y and Cu co-addition

Xing-hao Du, Chong Gao, Bao-lin Wu, Yu-hua Zhao, Ji-jie Wang

2012, 19(4): 348-353. doi: 10.1007/s12613-012-0562-x

中文摘要(208) PDF(10) SpringerLink

摘要:
The combined effects of (Y, Cu) on the microstructure and room-temperature mechanical properties of the NiAl intermetallic compound under uniaxial compression stress were investigated. It is found that the co-addition of Y and Cu enlarges the difference between the intergranular yield strength and the intragranular yield strength of NiAl grains. Hence, for the resultant NiAl-(Y,Cu) alloy, a mechanically hierarchical structure forms. This is beneficial to improve the room-temperature mechanical response of NiAl alloys; as a result, the resultant alloy with 0.56at% (Y, Cu) exhibits a remarkably enhanced compression plasticity of about 11.2%.

High-temperature mechanical properties and deformation behavior of high Nb containing TiAl alloys fabricated by spark plasma sintering

Xin Lu, Li-hua Zhao, Lang-ping Zhu, Bin Zhang, Xuan-hui Qu

2012, 19(4): 354-359. doi: 10.1007/s12613-012-0563-9

中文摘要(306) PDF(6) SpringerLink

摘要:
A high Nb containing TiAl alloy was prepared from the pre-alloyed powder of Ti-45Al-8.5Nb-0.2B-0.2W-0.02Y (at%) by spark plasma sintering (SPS). Its high-temperature mechanical properties and compressive deformation behavior were investigated in a temperature range of 700 to 1050℃ and a strain rate range of 0.002 to 0.2 s^-1. The results show that the high-temperature mechanical properties of the high Nb containing TiAl alloy are sensitive to deformation temperature and strain rate, and the sensitivity to strain rate tends to rise with the deformation temperature increasing. The hot workability of the alloy is good at temperatures higher than 900℃, while fracture occurs at lower temperatures. The flow curves of the samples compressed at or above 900℃ exhibit obvious flow softening after the peak stress. Under the deformation condition of 900-1050℃ and 0.002-0.2 s^-1, the interrelations of peak flow stress, strain rate, and deformation temperature follow the Arrhenius' equation modified by a hyperbolic sine function with a stress exponent of 5.99 and an apparent activation energy of 441.2 kJ·mol^-1.

Effect of preheat on TIG welding of AZ61 magnesium alloy

Jun Shen, Nan Xu

2012, 19(4): 360-363. doi: 10.1007/s12613-012-0564-8

中文摘要(350) PDF(11) SpringerLink

摘要:
The effects of preheat treatments on the microstructures and mechanical properties of tungsten inert gas (TIG)-welded AZ61 magnesium alloy joints were studied by microstructural observations, microhardness tests and tensile tests. The results showed that the volume fraction of the lamellar β-Mg₁₇(Al,Zn)₁₂ intermetallic compound of in fusion zone (FZ) increased from 15% to 66% with an increase in preheat temperature. Moreover, the microhardness of the FZ and the ultimate tensile strength of the welded joints reached their maximum values when the preheat temperature was 300℃ because more lamellar β-Mg₁₇(Al,Zn)₁₂ intermetallic compounds were distributed at the α-Mg grain boundaries and no cracks and pores formed in the FZ of the welded joint.

Selective interfacial bonding and thermal conductivity of diamond/Cu-alloy composites prepared by HPHT technique

Hui Chen, Cheng-chang Jia, Shang-jie Li, Xian Jia, Xia Yang

2012, 19(4): 364-371. doi: 10.1007/s12613-012-0565-7

中文摘要(321) PDF(10) SpringerLink

摘要:
Cu-based and Cu-alloy-based diamond composites were made by high-pressure-high-temperature (HPHT) sintering with the aim of maximizing the thermal conductivity of the composites. Improvements in interfacial bonding strength and thermo-physical properties of the composites were achieved using an atomized copper alloy with minor additions of Co, Cr, B, and Ti. The thermal conductivity (TC) obtained exhibited as high as 688 W·m^-1·K^-1, but also as low as 325 W·m^-1·K^-1. A large variation in TC can be rationalized by the discrepancy of diamond-matrix interfacial bonding. It was found from fractography that preferential bonding between diamond and the Cu-alloy matrix occurred only on the diamond {100} faces. EDS analysis and Raman spectra suggested that selective interfacial bonding may be attributed to amorphous carbon increasing the wettability between diamond and the Cu-alloy matrix. Amorphous carbon was found to significantly affect the TC of the composite by interface modification.

Preparation and photocatalytic properties of ilmenite NiTiO₃ powders for degradation of humic acid in water

Pei-hong Yuan, Cai-mei Fan, Guang-yue Ding, Yun-fang Wang, Xiao-chao Zhang

2012, 19(4): 372-376. doi: 10.1007/s12613-012-0566-6

中文摘要(319) PDF(8) SpringerLink

摘要:
The powders of ilmenite structure NiTiO₃ were prepared by a modified Pechini process using tetrabutyl titanate and nickel acetate as raw materials, and using citric acid and ethanol as a chelating agent and a solvent respectively. The powder samples were characterized by thermogravimetric and differential thermal analysis (TG-DTA) and X-ray diffraction (XRD). The photocatalytic activity of NiTiO₃ under the irradiation of ultraviolet rays (UV) light was evaluated by degrading humic acid (HA) in water as a probe reaction. The possible photodegradation mechanism was studied by the examination of active species ·OH, ·O₂^-, and holes (h⁺) through adding scavengers. The TG-DTA and XRD results indicated that the good crystal structure of ilmenite phase NiTiO₃ could be obtained when the Ni-Ti citrate complex was calcined at 600℃. The photocatalytic activity experiments indicated that NiTiO₃ had favourable photocatalytic activity under the irradiation of UV light, and the photocatalytic degradation rate of HA reached 95.3% after a 2.5 h reaction with the photocatalyst calcined at 600℃ and a photocatalyst dosage of 0.4 g/L. The possible photocatalytic mechanism was deduced that holes (h⁺) and ·OH radicals are the major reactive active species in the photocatalytic reaction, and dissolved oxygen plays a weak role in the degradation of HA.

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2012年第19卷第4期

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2012年第19卷第4期