International Journal of Minerals, Metallurgy and Materials

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研究论文

Use of high-resolution X-ray computed tomography and 3D image analysis to quantify mineral dissemination and pore space in oxide copper ore particles

Bao-hua Yang, Ai-xiang Wu, Guillermo A. Narsilio, Xiu-xiu Miao, Shu-yue Wu

2017, 24(9): 965-973. doi: 10.1007/s12613-017-1484-4

中文摘要(571) PDF(40) SpringerLink

摘要:
Mineral dissemination and pore space distribution in ore particles are important features that influence heap leaching performance. To quantify the mineral dissemination and pore space distribution of an ore particle, a cylindrical copper oxide ore sample (φ4.6 mm×5.6 mm) was scanned using high-resolution X-ray computed tomography (HRXCT), a nondestructive imaging technology, at a spatial resolution of 4.85 μm. Combined with three-dimensional (3D) image analysis techniques, the main mineral phases and pore space were segmented and the volume fraction of each phase was calculated. In addition, the mass fraction of each mineral phase was estimated and the result was validated with that obtained using traditional techniques. Furthermore, the pore phase features, including the pore size distribution, pore surface area, pore fractal dimension, pore centerline, and the pore connectivity, were investigated quantitatively. The pore space analysis results indicate that the pore size distribution closely fits a log-normal distribution and that the pore space morphology is complicated, with a large surface area and low connectivity. This study demonstrates that the combination of HRXCT and 3D image analysis is an effective tool for acquiring 3D mineralogical and pore structural data.

研究论文Open Access

Recovery of iron from copper tailings via low-temperature direct reduction and magnetic separation:process optimization and mineralogical study

Rui-min Jiao, Peng Xing, Cheng-yan Wang, Bao-zhong Ma, Yong-Qiang Chen

2017, 24(9): 974-982. doi: 10.1007/s12613-017-1485-3

中文摘要(670) PDF(39) SpringerLink

摘要:
Currently, the majority of copper tailings are not effectively developed. Worldwide, large amounts of copper tailings generated from copper production are continuously dumped, posing a potential environmental threat. Herein, the recovery of iron from copper tailings via low-temperature direct reduction and magnetic separation was conducted; process optimization was carried out, and the corresponding mineralogy was investigated. The reduction time, reduction temperature, reducing agent (coal), calcium chloride additive, grinding time, and magnetic field intensity were examined for process optimization. Mineralogical analyses of the sample, reduced pellets, and magnetic concentrate under various conditions were performed by X-ray diffraction, optical microscopy, and scanning electron microscopy-energy-dispersive X-ray spectrometry to elucidate the iron reduction and growth mechanisms. The results indicated that the optimum parameters of iron recovery include a reduction temperature of 1150℃, a reduction time of 120 min, a coal dosage of 25%, a calcium chloride dosage of 2.5%, a magnetic field intensity of 100 mT, and a grinding time of 1 min. Under these conditions, the iron grade in the magnetic concentrate was greater than 90%, with an iron recovery ratio greater than 95%.

研究论文

Study on mechanisms of different sulfuric acid leaching technologies of chromite

Pei-yang Shi, Cheng-jun Liu, Qing Zhao, Hao-nan Shi

2017, 24(9): 983-990. doi: 10.1007/s12613-017-1486-2

中文摘要(533) PDF(40) SpringerLink

摘要:
The extraction of chromate from chromite via the sulfuric acid leaching process has strong potential for practical use because it is a simple and environmentally friendly process. This paper aims to study the sulfuric acid leaching process using chromite as a raw material via either microwave irradiation or in the presence of an oxidizing agent. The results show that the main phases in Pakistan chromite are ferrichromspinel, chrompicotite, hortonolite, and silicate embedded around the spinel phases. Compared with the process with an oxidizing agent, the process involving microwaves has a higher leaching efficiency. When the mass fraction of sulfuric acid was 80% and the leaching time was 20 min, the efficiency could exceed 85%. In addition, the mechanisms of these two technologies fundamentally differ. When the leaching was processed in the presence of an oxidizing agent, the silicate was leached first and then expanded. By contrast, in the case of leaching under microwave irradiation, the chromite was dissolved layer by layer and numerous cracks appeared at the particle surface because of thermal shock. In addition, the silicate phase shrunk instead of expanding.

研究论文Open Access

Basic characteristics of Australian iron ore concentrate and its effects on sinter properties during the high-limonite sintering process

Dong-hui Liu, Hao Liu, Jian-liang Zhang, Zheng-jian Liu, Xun Xue, Guang-wei Wang, Qing-feng Kang

2017, 24(9): 991-998. doi: 10.1007/s12613-017-1487-1

中文摘要(486) PDF(12) SpringerLink

摘要:
The basic characteristics of Australian iron ore concentrate (Ore-A) and its effects on sinter properties during a high-limonite sintering process were studied using micro-sinter and sinter pot methods. The results show that the Ore-A exhibits good granulation properties, strong liquid flow capability, high bonding phase strength and crystal strength, but poor assimilability. With increasing Ore-A ratio, the tumbler index and the reduction index (RI) of the sinter first increase and then decrease, whereas the softening interval (∆T) and the softening start temperature (T_10%) of the sinter exhibit the opposite behavior; the reduction degradation index (RDI_+3.15) of the sinter increases linearly, but the sinter yield exhibits no obvious effects. With increasing Ore-A ratio, the distribution and crystallization of the minerals are improved, the main bonding phase first changes from silico-ferrite of calcium and aluminum (SFCA) to kirschsteinite, silicate, and SFCA and then transforms to 2CaO·SiO₂ and SFCA. Given the utilization of Ore-A and the improvement of the sinter properties, the Ore-A ratio in the high-limonite sintering process is suggested to be controlled at approximately 6wt%.

研究论文

Effects of temperature-gradient-induced damage of zirconia metering nozzles

Liang Zhao, Qun-hu Xue

2017, 24(9): 999-1003. doi: 10.1007/s12613-017-1488-0

中文摘要(406) PDF(11) SpringerLink

摘要:
The effects of temperature-gradient-induced damage of zirconia metering nozzles were investigated through analysis of the phase composition and microstructure of nozzle samples. The analysis was carried out using X-ray diffraction and scanning electron microscopy after the samples were subjected to a heat treatment based on the temperatures of the affected, transition, and original layers of zirconia metering nozzles during the continuous casting of steel. The results showed that, after heat treatment at 1540, 1410, or 1300℃ for a dwell time of 5 h, the monoclinic zirconia phase was gradually stabilized with increasing heat-treatment temperature. Moreover, a transformation to the cubic zirconia phase occurred, accompanied by grain growth, which illustrates that the temperature gradient in zirconia metering nozzles affects the mineral composition and microstructure of the nozzles and accelerates damage, thereby deteriorating the quality and service life of the nozzles.

研究论文

Effects of mechanical strain amplitude on the isothermal fatigue behavior of H13

Yan Zeng, Peng-peng Zuo, Xiao-chun Wu, Shu-wen Xia

2017, 24(9): 1004-1009. doi: 10.1007/s12613-017-1489-z

中文摘要(448) PDF(12) SpringerLink

摘要:
Isothermal fatigue (IF) tests were performed on H13 tool steel subjected to three different mechanical strain amplitudes at a constant temperature to determine the effects of mechanical strain amplitude on the microstructure of the steel samples. The samples' extent of damage after IF tests was compared by observation of their cracks and calculation of their damage parameters. Optical microscopy (OM) and scanning electron microscopy (SEM) were used to observe the microstructure of the samples. Cracks were observed to initiate at the surface because the strains and stresses there were the largest during thermal cycling. Mechanical strain accelerated the damage and softening of the steel. A larger mechanical strain caused greater deformation of the steel, which made the precipitated carbides easier to gather and grow along the deformation direction, possibly resulting in softening of the material or the initiation of cracks.

研究论文

Effect of prolonged isothermal heat treatment on the mechanical behavior of advanced NANOBAIN steel

Behzad Avishan

2017, 24(9): 1010-1020. doi: 10.1007/s12613-017-1490-6

中文摘要(584) PDF(10) SpringerLink

摘要:
The microstructural evolution and consequent changes in strength and ductility of advanced NANOBAIN steel during prolonged isothermal heat-treatment stages were investigated. The microstructure and mechanical properties of nanostructured bainite were not expected to be influenced by extending the heat-treatment time beyond the optimum value because of the autotempering phenomenon and high tempering resistance. However, experimental results indicated that the microstructure was thermodynamically unstable and that prolonged austempering resulted in carbon depletion from high-carbon retained austenite and carbide precipitations. Therefore, austenite became thermally less stable and partially transformed into martensite during cooling to room temperature. Prolonged austempering did not lead to the typical tempering sequence of bainite, and the sizes of the microstructural constituents were independent of the extended heat-treatment times. This independence, in turn, resulted in almost constant ultimate tensile strength values. However, microstructural variations enhanced the yield strength and the hardness of the material at extended isothermal heat-treatment stages. Finally, although microstructural changes decreased the total elongation and impact toughness, considerable combinations of mechanical properties could still be achieved.

研究论文

Effects of size reduction on deformation, microstructure, and surface roughness of micro components for micro metal injection molding

Lin Liu, Xin-da Wang, Xiang Li, Xiao-tong Qi, Xuan-hui Qu

2017, 24(9): 1021-1026. doi: 10.1007/s12613-017-1491-5

中文摘要(486) PDF(10) SpringerLink

摘要:
The fabrication of 17-4PH micro spool mandrils by micro metal injection molding was described here. The effects of size reduction on deformation, microstructure and surface roughness were studied by comparing a φ500 μm micro post and a φ1.7 mm cylinder after debinding and sintering. Experimental results show that slumping of the micro posts occurred due to a dramatic increase in outlet vapor pressure initiated at the thermal degradation onset temperature and the moment of gravity. Asymmetrical stress distribution within the micro component formed during the cooling stage may cause warping. Prior solvent debinding and adjustment in a thermal debinding scheme were useful for preventing the deformation of the micro components. Smaller grain size and higher micro hardness due to impeded grain growth were observed for the micro posts compared with the φ1.7 mm cylinder. Surface roughness increased with distance from the gate of the micro spool mandril due to melt front advancement during mold filling and the ensuing pressure distribution. At each position, surface roughness was dictated by injection molding and increased slightly after sintering.

研究论文

Mechanical properties and microstructure of 3D-printed high Co-Ni secondary hardening steel fabricated by laser melting deposition

Hui-ping Duan, Xiao Liu, Xian-zhe Ran, Jia Li, Dong Liu

2017, 24(9): 1027-1033. doi: 10.1007/s12613-017-1492-4

中文摘要(608) PDF(21) SpringerLink

摘要:
The mechanical properties and microstructure of the 3D-printed high Co-Ni secondary hardening steel fabricated by the laser melting deposition technique was investigated using a material testing machine and electron microscopy. A microstructure investigation revealed that the samples consist of martensite laths, fine dispersed precipitates, and reverted austenite films at the martensite lath boundaries. The precipitates are enriched with Co and Mo. Because the sample tempered at 486℃ has smaller precipitates and a higher number of precipitates per unit area, it exhibits better mechanical properties than the sample tempered at 498℃. Although the 3D-printed samples have the same phase constituents as AerMet 100 steel, the mechanical properties are slightly worse than those of the commercial wrought AerMet 100 steel because of the presence of voids.

研究论文

Electrical conductivity optimization of the Na₃AlF₆-Al₂O₃-Sm₂O₃ molten salts system for Al-Sm intermediate binary alloy production

Chun-fa Liao, Yun-fen Jiao, Xu Wang, Bo-qing Cai, Qiang-chao Sun, Hao Tang

2017, 24(9): 1034-1042. doi: 10.1007/s12613-017-1493-3

中文摘要(519) PDF(12) SpringerLink

摘要:
Metal Sm has been widely used in making Al-Sm magnet alloy materials. Conventional distillation technology to produce Sm has the disadvantages of low productivity, high costs, and pollution generation. The objective of this study was to develop a molten salt electrolyte system to produce Al-Sm alloy directly, with focus on the electrical conductivity and optimal operating conditions to minimize the energy consumption. The continuously varying cell constant (CVCC) technique was used to measure the conductivity for the Na₃AlF₆-AlF₃-LiF-MgF₂-Al₂O₃-Sm₂O₃ electrolysis medium in the temperature range from 905 to 1055℃. The temperature (t) and the addition of Al₂O₃ (W(Al₂O₃)), Sm₂O₃ (W(Sm₂O₃)), and a combination of Al₂O₃ and Sm₂O₃ into the basic fluoride system were examined with respect to their effects on the conductivity (κ) and activation energy. The experimental results showed that the molten electrolyte conductivity increases with increasing temperature (t) and decreases with the addition of Al₂O₃ or Sm₂O₃ or both. We concluded that the optimal operation conditions for Al-Sm intermediate alloy production in the Na₃AlF₆-AlF₃-LiF-MgF₂-Al₂O₃-Sm₂O₃ system are W(Al₂O₃) + W(Sm₂O₃)=3wt%, W(Al₂O₃):W(Sm₂O₃)=7:3, and a temperature of 965 to 995℃, which results in satisfactory conductivity, low fluoride evaporation losses, and low energy consumption.

研究论文

Structural, morphological, and optical properties of tin(IV) oxide nanoparticles synthesized using Camellia sinensis extract:a green approach

J. Celina Selvakumari, M. Ahila, M. Malligavathy, D. Pathinettam Padiyan

2017, 24(9): 1043-1051. doi: 10.1007/s12613-017-1494-2

中文摘要(1081) PDF(50) SpringerLink

摘要:
Tin oxide (SnO₂) nanoparticles were cost-effectively synthesized using nontoxic chemicals and green tea (Camellia sinensis) extract via a green synthesis method. The structural properties of the obtained nanoparticles were studied using X-ray diffraction, which indicated that the crystallite size was less than 20 nm. The particle size and morphology of the nanoparticles were analyzed using scanning electron microscopy and transmission electron microscopy. The morphological analysis revealed agglomerated spherical nanoparticles with sizes varying from 5 to 30 nm. The optical properties of the nanoparticles' band gap were characterized using diffuse reflectance spectroscopy. The band gap was found to decrease with increasing annealing temperature. The O vacancy defects were analyzed using photoluminescence spectroscopy. The increase in the crystallite size, decreasing band gap, and the increasing intensities of the UV and visible emission peaks indicated that the green-synthesized SnO₂ may play future important roles in catalysis and optoelectronic devices.

研究论文

Effect of reinforcement content on the adhesive wear behavior of Cu10Sn5Ni/Si₃N₄ composites produced by stir casting

K. Sanesh, S. Shiam Sunder, N. Radhika

2017, 24(9): 1052-1060. doi: 10.1007/s12613-017-1495-1

中文摘要(489) PDF(31) SpringerLink

摘要:
The main objective of this paper was to fabricate Cu10Sn5Ni alloy and its composites reinforced with various contents of Si₃N₄ particles (5wt%, 10wt%, and 15wt%) and to investigate their dry sliding wear behavior using a pin-on-disk tribometer. Microstructural examinations of the specimens revealed a uniform dispersion of Si₃N₄ particles in the copper matrix. Wear experiments were performed for all combinations of parameters, such as load (10, 20, and 30 N), sliding distance (500, 1000, and 1500 m), and sliding velocity (1, 2, and 3 m/s), for the alloy and the composites. The results revealed that wear rate increased with increasing load and increasing sliding distance, whereas the wear rate decreased and then increased with increasing sliding velocity. The primary wear mechanism encountered at low loads was mild adhesive wear, whereas that at high loads was severe delamination wear. An oxide layer was formed at low velocities, whereas a combination of shear and plastic deformation occurred at high velocities. The mechanism at short sliding distances was ploughing action of Si₃N₄ particles, which act as protrusions; by contrast, at long sliding distances, direct metal-metal contact occurred. Among the investigated samples, the Cu/10wt% Si₃N₄ composite exhibited the best wear resistance at a load of 10 N, a velocity of 2 m/s, and a sliding distance of 500 m.

研究论文Open Access

In situ reaction mechanism of MgAlON in Al-Al₂O₃-MgO composites at 1700℃ under flowing N₂

Shang-hao Tong, Yong Li, Ming-wei Yan, Peng Jiang, Jia-jia Ma, Dan-dan Yue

2017, 24(9): 1061-1066. doi: 10.1007/s12613-017-1496-0

中文摘要(570) PDF(18) SpringerLink

摘要:
The Al-Al₂O₃-MgO composites with added aluminum contents of approximately 0wt%, 5wt%, and 10wt%, named as M₁, M₂, and M₃, respectively, were prepared at 1700℃ for 5 h under a flowing N₂ atmosphere using the reaction sintering method. After sintering, the Al-Al₂O₃-MgO composites were characterized and analyzed by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The results show that specimen M₁ was composed of MgO and MgAl₂O₄. Compared with specimen M₁, specimens M₂ and M₃ possessed MgAlON, and its production increased with increasing aluminum addition. Under an N₂ atmosphere, MgO, Al₂O₃, and Al in the matrix of specimens M₂ and M₃ reacted to form MgAlON and AlN-polytypoids, which combined the particles and the matrix together and imparted the Al-Al₂O₃-MgO composites with a dense structure. The mechanism of MgAlON synthesis is described as follows. Under an N₂ atmosphere, the partial pressure of oxygen is quite low; thus, when the Al-Al₂O₃-MgO composites were soaked at 580℃ for an extended period, aluminum metal was transformed into AlN. With increasing temperature, Al₂O₃ diffused into AlN crystal lattices and formed AlN-polytypoids; however, MgO reacted with Al₂O₃ to form MgAl₂O₄. When the temperature was greater than (1640 ±10)℃, AlN diffused into Al₂O₃ and formed spinel-structured AlON. In situ MgAlON was acquired through a solid-solution reaction between AlON and MgAl₂O₄ at high temperatures because of their similar spinel structures.

研究论文

Spheroidization of silica powders by radio frequency inductively coupled plasma with Ar-H₂ and Ar-N₂ as the sheath gases at atmospheric pressu

Lin Li, Guo-hua Ni, Qi-jia Guo, Qi-fu Lin, Peng Zhao, Jun-li Cheng

2017, 24(9): 1067-1074. doi: 10.1007/s12613-017-1497-z

中文摘要(513) PDF(24) SpringerLink

摘要:
Amorphous spherical silica powders were prepared by inductively coupled thermal plasma treatment at a radio frequency of 36.2 MHz. The effects of the added content of hydrogen and nitrogen into argon (serving as the sheath gas), as well as the carrier gas flow rate, on the spheroidization rate of silica powders, were investigated. The prepared silica powders before and after plasma treatment were examined by scanning electron microscopy, X-ray diffraction, and laser granulometric analysis. Results indicated that the average size of the silica particles increased, and the transformation of crystals into the amorphous state occurred after plasma treatment. Discharge image processing was employed to analyze the effect of the plasma temperature field on the spheroidization rate. The spheroidization rate of the silica powder increased with the increase of the hydrogen content in the sheath gas. On the other hand, the spheroidization rate of the silica power first increased and then decreased with the increase of the nitrogen content in the sheath gas. Moreover, the amorphous content increased with the increase of the spheroidization rate of the silica powder.

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