International Journal of Minerals, Metallurgy and Materials

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Kinetic approach to the study of froth flotation applied to a lepidolite ore

Nathália Vieceli, Fernando O. Durão, Carlos Guimarães, Carlos A. Nogueira, Manuel F. C. Pereira, Fernanda Margarido

2016, 23(7): 731-742. doi: 10.1007/s12613-016-1287-z

中文摘要(266) PDF(21) SpringerLink

摘要:
The number of published studies related to the optimization of lithium extraction from low-grade ores has increased as the demand for lithium has grown. However, no study related to the kinetics of the concentration stage of lithium-containing minerals by froth flotation has yet been reported. To establish a factorial design of batch flotation experiments, we conducted a set of kinetic tests to determine the most selective alternative collector, define a range of pulp pH values, and estimate a near-optimum flotation time. Both collectors (Aeromine 3000C and Armeen 12D) provided the required flotation selectivity, although this selectivity was lost in the case of pulp pH values outside the range between 2 and 4. Cumulative mineral recovery curves were used to adjust a classical kinetic model that was modified with a non-negative parameter representing a delay time. The computation of the near-optimum flotation time as the maximizer of a separation efficiency (SE) function must be performed with caution. We instead propose to define the near-optimum flotation time as the time interval required to achieve 95%–99% of the maximum value of the SE function.

Removal of phosphorus-rich phase from high-phosphorous iron ore by melt separation at 1573 K in a super-gravity field

Jin-tao Gao, Lei Guo, Yi-wei Zhong, Hong-ru Ren, Zhan-cheng Guo

2016, 23(7): 743-750. doi: 10.1007/s12613-016-1288-y

中文摘要(169) PDF(8) SpringerLink

摘要:
A new approach of removing the phosphorus-rich phase from high-phosphorous iron ore by melt separation at 1573 K in a super- gravity field was investigated. The iron-slag separation by super-gravity resulted in phosphorus being effectively removed from the iron-rich phase and concentrated as a phosphorus-rich phase at a temperature below the melting point of iron. The samples obtained by super-gravity exhibited obvious layered structures. All the iron grains concentrated at the bottom of the sample along the super-gravity direction, whereas the molten slag concentrated in the upper part of the sample along the opposite direction. Meanwhile, fine apatite crystals collided and grew into larger crystals and concentrated at the slag–iron interface. Consequently, in the case of centrifugation with a gravity coefficient of G = 900, the mass fractions of the slag phase and iron-rich phase were similar to their respective theoretical values. The mass fraction of MFe in the iron-rich phase was as high as 97.77wt% and that of P was decreased to 0.092wt%.

Phosphorus partitioning and recovery of low-phosphorus iron-rich compounds through physical separation of Linz-Donawitz slag

Dilip Makhija, Rajendra Kumar Rath, Kaushik Chakravarty, Abhay Shankar Patra, Asim Kumar Mukherjee, Akhilesh Kumar Dubey

2016, 23(7): 751-759. doi: 10.1007/s12613-016-1289-x

中文摘要(250) PDF(13) SpringerLink

摘要:
The Linz-Donawitz (LD) steelmaking process produces LD slag at a rate of about 125 kg/t. After metallic scrap recovery, the non-metallic LD slag is rejected because its physical/chemical properties are unsuitable for recycling. X-ray diffraction (XRD) studies have indicated that non-metallic LD slag contains a substantial quantity of mineral phases such as di- and tricalcium silicates. The availability of these mineral phases indicates that LD slag can be recycled by iron (Fe)-ore sintering. However, the presence of 1.2wt% phosphorus (P) in the slag renders the material unsuitable for sintering operations. Electron probe microscopic analysis (EPMA) studies indicated concentration of phosphorus in dicalcium silicate phase as calcium phosphate. The Fe-bearing phases (i.e., wustite and dicalcium ferrite) showed comparatively lower concentrations of P compared with other phases in the slag. Attempts were made to lower the P content of LD slag by adopting various beneficiation techniques. Dry high-intensity magnetic separation and jigging were performed on as-received samples with particle sizes of 6 and 3 mm. Spiral separation was conducted using samples ground to sizes of less than 1 and 0.5 mm. Among these studies, grinding to 0.5 mm followed by spiral concentration demonstrated the best results, yielding a concentrate with about 0.75wt% P and 45wt% Fe.

Phase transformation behavior of titanium during carbothermic reduction of titanomagnetite ironsand

Yi-ran Liu, Jian-liang Zhang, Zheng-jian Liu, Xiang-dong Xing

2016, 23(7): 760-768. doi: 10.1007/s12613-016-1290-4

中文摘要(326) PDF(14) SpringerLink

摘要:
The reduction of titanomagnetite (TTM) ironsand, which contains 11.41wt% TiO₂ and 55.63wt% total Fe, by graphite was performed using a thermogravimetric analysis system under an argon gas atmosphere at 1423–1623 K. The behavior and effects of titanium in TTM ironsand during the reduction process were investigated by means of thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. During the reduction procedure, the titanium concentrated in the slag phase, where the phase transformation followed this sequence: FeO + FeTiO₃ → Fe₂TiO₄ → FeTiO₃ → FeTi₂O₅ → TiO₂. The calculated results for the reduction kinetics showed that the carbothermic reduction was controlled by the diffusion of ions through the product layer. Furthermore, the apparent activation energy was 170.35 kJ·mol^-1.

Influence of oxide scales on the corrosion behaviors of B510L hot-rolled steel strips

Cheng Man, Chao-fang Dong, Hui-bin Xue, Kui Xiao, Xiao-gang Li, Hui-bin Qi

2016, 23(7): 769-778. doi: 10.1007/s12613-016-1291-3

中文摘要(227) PDF(10) SpringerLink

摘要:
The influence of oxide scales on the corrosion behaviors of B510L hot-rolled steel strips was investigated in this study. Focused ion beams and scanning electron microscopy were used to observe the morphologies of oxide scales on the surface and cross sections of the hot-rolled steel. Raman spectroscopy and X-ray diffraction were used for the phase analysis of the oxide scales and corrosion products. The corrosion potential and impedance were measured by anodic polarization and electrochemical impedance spectroscopy. According to the results, oxide scales on the hot-rolled strips mainly comprise iron and iron oxides. The correlation between mass gain and test time follows a power exponential rule in the damp-heat test. The corrosion products are found to be mainly composed of γ-FeOOH, Fe₃O₄, α-FeOOH, and γ-Fe₂O₃. The contents of the corrosion products are different on the surfaces of the steels with and without oxide scales. The steel with oxide scales is found to show a higher corrosion resistance and lower corrosion rate.

Microstructural evolution during ultra-rapid annealing of severely deformed low-carbon steel: strain, temperature, and heating rate effects

M. A. Mostafaei, M. Kazeminezhad

2016, 23(7): 779-792. doi: 10.1007/s12613-016-1292-2

中文摘要(177) PDF(9) SpringerLink

摘要:
An interaction between ferrite recrystallization and austenite transformation in low-carbon steel occurs when recrystallization is delayed until the intercritical temperature range by employing high heating rate. The kinetics of recrystallization and transformation is affected by high heating rate and such an interaction. In this study, different levels of strain are applied to low-carbon steel using a severe plastic deformation method. Then, ultra-rapid annealing is performed at different heating rates of 200–1100℃/s and peak temperatures of near critical temperature. Five regimes are proposed to investigate the effects of heating rate, strain, and temperature on the interaction between recrystallization and transformation. The microstructural evolution of severely deformed low-carbon steel after ultra-rapid annealing is investigated based on the proposed regimes. Regarding the intensity and start temperature of the interaction, different microstructures consisting of ferrite and pearlite/martensite are formed. It is found that when the interaction is strong, the microstructure is refined because of the high kinetics of transformation and recrystallization. Moreover, strain shifts an interaction zone to a relatively higher heating rate. Therefore, severely deformed steel should be heated at relatively higher heating rates for it to undergo a strong interaction.

Production and characterization of high porosity porous Fe-Cr-C alloys by the space holder leaching technique

Da-rong Tian, Yu-hua Pang, Liang Yu, Li Sun

2016, 23(7): 793-798. doi: 10.1007/s12613-016-1293-1

中文摘要(188) PDF(8) SpringerLink

摘要:
Spherical carbamide particles were employed to produce porous Fe-Cr-C alloy with high porosity and large aperture via the space-holder leaching technique. A series of porous samples were prepared by regulating the processing parameters, which included the carbamide content and the compaction pressure. The pore characteristics and compression properties of the produced samples were investigated. The samples were characterized by scanning electron microscopy, image analysis, and compression tests. The results showed that the macro-porosity and the mean pore size were in the ranges 40.4%–82.4% and 0.6–1.5 mm, respectively. The compressive strength varied between 25.38 MPa and 127.9 MPa, and was observed to decrease with increasing total porosity.

Effects of different friction stir welding conditions on the microstructure and mechanical properties of copper plates

Ali Alavi Nia, Ali Shirazi

2016, 23(7): 799-809. doi: 10.1007/s12613-016-1294-0

中文摘要(385) PDF(10) SpringerLink

摘要:
Friction stir welding is a new and innovative welding method used to fuse materials. In this welding method, the heat generated by friction and plastic flow causes significant changes in the microstructure of the material, which leads to local changes in the mechanical properties of the weld. In this study, the effects of various welding parameters such as the rotational and traverse speeds of the tool on the microstructural and mechanical properties of copper plates were investigated; additionally, Charpy tests were performed on copper plates for the first time. Also, the effect of the number of welding passes on the aforementioned properties has not been investigated in previous studies. The results indicated that better welds with superior properties are produced when less heat is transferred to the workpiece during the welding process. It was also found that although the properties of the stir zone improved with an increasing number of weld passes, the properties of its weakest zone, the heat-affected zone, deteriorated.

Microstructure of Ni–Al powder and Ni–Al composite coatings prepared by twin-wire arc spraying

Ji-xiao Wang, Gui-xian Wang, Jing-shun Liu, Lun-yong Zhang, Wei Wang, Ze Li, Qi-xiang Wang, Jian-fei Sun

2016, 23(7): 810-818. doi: 10.1007/s12613-016-1295-z

中文摘要(181) PDF(10) SpringerLink

摘要:
Ni–Al powder and Ni–Al composite coatings were fabricated by twin-wire arc spraying (TWAS). The microstructures of Ni-5wt%Al powder and Ni-20wt%Al powder were characterized by scanning electronic microscopy (SEM) and energy dispersive spectroscopy (EDS). The results showed that the obtained particle size ranged from 5 to 50 μm. The morphology of the Ni–Al powder showed that molten particles were composed of Ni solid solution, NiAl, Ni₃Al, Al₂O₃, and NiO. The Ni–Al phase and a small amount of Al₂O₃ particles changed the composition of the coating. The microstructures of the twin-wire-arc-sprayed Ni–Al composite coatings were characterized by SEM, EDS, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The results showed that the main phase of the Ni-5wt%Al coating consisted of Ni solid solution and NiAl in addition to a small amount of Al₂O₃. The main phase of the Ni-20wt%Al coating mainly consisted of Ni solid solution, NiAl, and Ni₃Al in addition to a small amount of Al and Al₂O₃, and NiAl and Ni₃Al intermetallic compounds effectively further improved the final wear property of the coatings. TEM analysis indicated that fine spherical NiAl₃ precipitates and a Ni–Al–O amorphous phase formed in the matrix of the Ni solid solution in the original state.

Effects of applied potential on the stress corrosion cracking behavior of 7003 aluminum alloy in acid and alkaline chloride solutions

Xiao-yan Zhang, Ren-guo Song, Bin Sun, Hai Lu, Chao Wang

2016, 23(7): 819-826. doi: 10.1007/s12613-016-1296-y

中文摘要(191) PDF(9) SpringerLink

摘要:
Potentiodynamic polarization tests and slow strain rate test (SSRT) in combination with fracture morphology observations were conducted to investigate the stress corrosion cracking (SCC) behavior of 7003 aluminum alloy (AA7003) in acid and alkaline chloride solutions under various applied potentials (E_a). The results show that AA7003 is to a certain extent susceptible to SCC via anodic dissolution (AD) at open-circuit potential (OCP) and is highly susceptible to hydrogen embrittlement (HE) at high negative E_a in the solutions with pH levels of 4 and 11. The susceptibility increases with negative shift in the potential when E_a is less than -1000 mV vs. SCE. However, the susceptibility distinctly decreases because of the inhibition of AD when E_a is equal to -1000 mV vs. SCE. In addition, the SCC susceptibility of AA7003 in the acid chloride solution is higher than that in the alkaline solution at each potential. Moreover, the effect of hydrogen on SCC increases with increasing hydrogen ion concentration.

Microstructure and mechanical properties of cryorolled AZ31 magnesium alloy sheets with different initial textures

Jin-ru Luo, Ya-qiong Yan, Ji-shan Zhang, Lin-zhong Zhuang

2016, 23(7): 827-834. doi: 10.1007/s12613-016-1297-x

中文摘要(234) PDF(13) SpringerLink

摘要:
AZ31 magnesium alloy sheets with different strong textures were cryorolled at the liquid-nitrogen temperature to the strain of 4% and 8%. The microstructure and texture of the rolled sheets were investigated via scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and X-ray diffraction (XRD). The mechanical properties of the sheets were tested through in-plane uniaxial tensile tests at ambient temperature. The tensile stress was exerted in the rolling direction (RD) and transverse directions (TD). The microstructural and textural evolutions of the alloy during cryorolling were investigated. Due to active twining during rolling, the initial texture significantly influenced the microstructural and textural evolutions of the rolled sheets. A {1012} extension twin was found as the dominated twin-type in the cryorolled samples. After cryogenic rolling, the ductility of the samples decreased while the strength increased. Twinning also played an important role in explaining the mechanical differences between the rolled samples with different initial textures. The samples were significantly strengthened by the high stored energy accumulated from cryorolling.

Fabrication of nanoporous silver by de-alloying Cu-Zr-Ag amorphous alloys

Hui Wang, Shang-gang Xiao, Tao Zhang

2016, 23(7): 835-843. doi: 10.1007/s12613-016-1298-9

中文摘要(216) PDF(9) SpringerLink

摘要:
Nanoporous silver (NPS) with a ligament size ranging from 15 to 40 nm was fabricated by de-alloying (Cu₅₀Zr₅₀)_100-xAg_x (x = 10at%, 20at%, 30at%, and 40at%) amorphous ribbons in a mixed aqueous solution of hydrofluoric (HF) acid and nitric acid under free corrosion conditions. Nanoporous silver ligaments and pore sizes were able to be fine-tuned through tailoring the chemical composition, corrosion conditions, and de-alloying time. The ligament size increases with an increase in Ag content and de-alloying time, but decreases with an increase in HF concentration. This phenomenon may be attributed to the dissolution of Zr/Cu and the diffusion, aggregation, nucleation, and recrystallization of Ag, leading to an oriented attachment of adjacent nanocrystals as revealed by TEM analysis.

Conductive and corrosion behaviors of silver-doped carbon-coated stainless steel as PEMFC bipolar plates

Ming Liu, Hong-feng Xu, Jie Fu, Ying Tian

2016, 23(7): 844-849. doi: 10.1007/s12613-016-1299-8

中文摘要(223) PDF(11) SpringerLink

摘要:
Ni–Cr enrichment on stainless steel SS316L resulting from chemical activation enabled the deposition of carbon by spraying a stable suspension of carbon nanoparticles; trace Ag was deposited in situ to prepare a thin continuous Ag-doped carbon film on a porous carbon-coated SS316L substrate. The corrosion resistance of this film in 0.5 mol·L^-1 H₂SO₄ solution containing 5 ppm F^- at 80℃ was investigated using polarization tests. The results showed that the surface treatment of the SS316L strongly affected the adhesion of the carbon coating to the stainless steel. Compared to the bare SS316L, the Ag-doped carbon-coated SS316L bipolar plate was remarkably more stable in both the anode and cathode environments of proton exchange membrane fuel cell (PEMFC) and the interface contact resistance between the specimen and Toray 060 carbon paper was reduced from 333.0 mΩ·cm² to 21.6 mΩ·cm² at a compaction pressure of 1.2 MPa.

An improved implementable process for the synthesis of zeolite 4A from bauxite tailings and its Cr³⁺ removal capacity

Peng-cheng Lei, Xian-jiang Shen, Yang Li, Min Guo, Mei Zhang

2016, 23(7): 850-857. doi: 10.1007/s12613-016-1300-6

中文摘要(176) PDF(10) SpringerLink

摘要:
A simple and practical method for the synthesis of zeolite 4A from bauxite tailings is presented in this paper. Systematic investigations were carried out regarding the capacity of zeolite 4A to remove Cr(Ⅲ) from aqueous solutions with relatively low initial concentrations of Cr(Ⅲ) (5–100 mg·L^-1). It is found that the new method is extremely cost-effective and can significantly contribute in decreasing environmental pollution caused by the dumping of bauxite tailings. The Cr(Ⅲ) removal capacity highly depends on the initial pH value and concentration of Cr(Ⅲ) in the solution. The maximum removal capacity of Cr(Ⅲ) was evaluated to be 85.1 mg·g^-1 for zeolite 4A, measured at an initial pH value of 4 and an initial Cr(Ⅲ) concentration of 5 mg·L^-1. This approach enables a higher removal capacity at lower concentrations of Cr(Ⅲ), which is a clear advantage over the chemical precipitation method. The removal mechanism of Cr(Ⅲ) by zeolite 4A was examined. The results suggest that both ion exchange and the surface adsorption-crystallization reaction are critical steps. These two steps collectively resulted in the high removal capacity of zeolite 4A to remove Cr(Ⅲ).

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2016年第23卷第7期