Journal of Central South University of Technology

Xiao, Zheng-wei; Zhang, Ying-jie; Hu, Guo-rong

doi: 10.1007/s11771-015-2999-3pmid: N/A

The anoxic decomposition and influence of carbon precursors on the properties of LiFePO4/C prepared by using Fe2O3 were investigated. X-ray powder diffractometry, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and carbon content and charge–discharge tests were applied to the characterization of the as-synthesized cathodes. Partial carbon is lost in the anaerobic decomposition of organic precursors and a high hydrogen content leads to a high residual carbon rate. Pyromellitic anhydride and citric acid participate in reactions before and in ball-milling. All the chosen carbon precursors are capable of producing LiFePO4 with high degree of crystallinity and purity. The carbon derived from α-D-glucose, pyromellitic anhydride, soluble starch, citric acid and polyacrylamide has a loose and porous texture in LiFePO4/C which forms conduction on and between LiFePO4 particles. LiFePO4/C prepared by using α-D-glucose, pyromellitic anhydride, citric acid and sucrose exhibits appreciable electrochemical performance. Graphite alone is able to enhance the electrochemical performance of LiFePO4 to a limited extent but incapable of preparing practical cathode.

Xiong, Yi; He, Tian-tian; Li, Peng-yan; Chen, Lu-fei; Ren, Feng-zhang; Volinsky, Alex

doi: 10.1007/s11771-015-3000-1pmid: N/A

Surface microstructure and mechanical properties of pearlitic Fe–0.8%C (mass fraction) steel after laser shock processing (LSP) with different laser pulse energies were investigated by scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD) and microhardness measurements. After LSP, the cementite lamellae were bent, kinked and broken into particles. Fragmentation and dissolution of the cementite lamellae were enhanced by increasing the laser pulse energy. Due to the dissolution of carbon atoms in the ferritic matrix, the lattice parameter of α-Fe increased. The grain size of the surface ferrite was refined, and the microstructure changed from lamellae to ultrafine micro-duplex structure (ferrite (α)+cementite (θ)) with higher laser pulse energy, accompanied by the residual stress and microhardness increase.

Sun, Hong-peng; Cho, Jae-ung

doi: 10.1007/s11771-015-3001-0pmid: N/A

Aluminum foam is widely used in diverse areas to minimize the weight and maximize the absorption of shock energy in lightweight structures and various bio-materials. It presents a number of advantages, such as low density, incombustibility, non-rigidity, excellent energy absorptivity, sound absorptivity and low heat conductivity. The aluminum foam with an air cell structure was placed under the TDCB Mode II tensile load by using Landmark equipment manufactured by MTS to examine the shear failure behavior. The angle of the tapered adhesively-bonded surfaces of specimens was designated as a variable, and three models were developed with the inclined angles differing from one another at 6°, 8° and 10°. The specimens with the inclined angles of 6°, 8° and 10° have the maximum reaction forces of 168 N, 194 N when the forced displacements are 6, 5 and 4.2 mm respectively. There are three specimens with the inclined angles of 10°, 8° and 6° in the order of maximum reaction force. As the analysis result, the maximum equivalent stresses of 0.813 MPa and 0.895 MPa happened when the forced displacements of 6 mm and 5 mm proceeded at the models of 6° and 8°, respectively. A simulation was carried out on the basis of finite element method and the experimental design. The results of the experiment and the simulation analysis are shown not different from each other significantly. Thus, only a simulation could be confirmed to be performed in substitution of an experiment, which is costly and time-consuming in order to determine the shearing properties of materials made of aluminum foam with artificial data.

Chen, Bo-wei; Wu, Biao; Liu, Xing-yu; Wen, Jian-kang

doi: 10.1007/s11771-015-3002-zpmid: N/A

Simulated heap bioleaching of low-grade high pyrite-bearing chalcocite ore was conducted at 40°C with aeration of CO2 and N2. Ore samples were collected at day 43, 64, 85, 106 and subjected to microbial community analysis by 16S rRNA gene clone library. Phylogenetic analyses of 16S rDNA fragments revealed that the retrieved sequences are mainly related to genus Acidithiobacillus, Leptospirillum and Sulfobacillus. Aeration of CO2 and N2 significantly impacted the microbial community composition. When CO2 was aerated, the proportion of genus Acidithiobacillus considerably increased, whereas the proportion of genus Leptospirillum and genus Sulfobacillus declined. However, with the aeration of N2, the proportion of genus Acidithiobacillus and Leptospirillum increased, but genus Sulfobacillus decreased. When there was no aeration, the microbial community was similar to the inocula with the proportion of genus Leptospirillum mounted. These results indicated that the limitation of oxygen could change the bioleaching microbial community and the aeration of CO2 and N2 was favourable for the growth of sulfur-oxidizer (At. caldus) and iron-oxidizer (L. ferriphilum) respectively, which could be used for the regulation of microorganisms’ role in mineral bioleaching.

Yang, Hong-ying; Ma, Zhi-yuan; Huang, Song-tao; Lv, Yang; Xiong, Liu

doi: 10.1007/s11771-015-3003-ypmid: N/A

The application of microwave irradiation for pretreatment of copper anode slime with high nickel content prior to pressure sulfuric acid leaching has been proposed. The microwave-assisted pretreatment is a rapid and efficient process. Through the technology of microwave assisted pretreatment-pressure leaching of copper anode slime, copper, tellurium, selenium and nickel are almost completely recovered. Under optimal conditions, the leaching efficiencies of copper, tellurium, selenium and nickel are 97.12%, 95.97%, 95.37% and 93.90%, respectively. The effect of microwave radiation on the temperature of copper anode slime and leaching solution is investigated. It is suggested that the enhancement on the recoveries of copper, tellurium and selenium can be attributed to the temperature gradient which is caused by shallow microwave penetration depth and super heating occurring at the solid-liquid interface. The kinetic study shows that the pressure leaching of copper anode slime, with and without microwave assisted pretreatment, are both controlled by chemical reactions on the surfaces of particles. It is found that the activation energy calculated for microwave-assisted pretreatment-pressure leaching (49.47 kJ/mol) is lower than that for pressure leaching which is without microwave assisted pretreatment (60.57 kJ/mol).

Wang, Chong-qing; Wang, Hui; Gu, Guo-hua; Fu, Jian-gang; Liu, You-nian

doi: 10.1007/s11771-015-3004-xpmid: N/A

A hydrometallurgical process was developed for recycling pharmaceutical blisters. Leaching aluminum from pharmaceutical blisters using sodium hydroxide (NaOH) solutions was investigated with respect to leaching behaviors and kinetics. A L 9 (34) orthogonal design of experiments suggests that the most significant factor is NaOH concentration followed by temperature and leaching time. Factorial experiments demonstrate that the leaching rate of aluminum increases with increasing of the factors. The optimum conditions are temperature of 70 °C, leaching time of 20 min, NaOH concentration of 1.25 mol/L, liquid-to-solid mass ratio of 15:1 and agitation speed of 400 r/min. Under optimum conditions, the leaching rate is up to 100%, implying that aluminum and polyvinyl chloride (PVC) plastic in pharmaceutical blisters are separated completely. Kinetics of leaching aluminum is best described by the product layer diffusion control model, and the activation energy is calculated to be 19.26 kJ/mol.

Wen, Jin; Liu, Can-jun; Du, Yong; Hu, Chuan-yue; Tian, Xiu-ying

doi: 10.1007/s11771-015-3005-9pmid: N/A

CdS quantum dots sensitized platelike WO3 photoelectrodes were successfully synthesized by a facile hydrothermal method and a modified chemical bath deposition (CBD) technique. To further improve the stability of the photoelectrodes in alkaline environment, the platelike WO3 films were treated with TiCl4 to form a nano-TiO2 buffer layer on the WO3 plate surface before loading CdS QDs. The resulting electrodes were characterized by using XRD, SEM, HR-TEM and UV-vis spectrum. The photocatalytic activity of the resulting electrodes was investigated by degradation of methyl orange (MO) in aqueous solution. The photoelectrochemical (PEC) property of the resulting electrodes was also characterized by the linear sweep voltammetry. The results of both the degradation of MO and photocurrent tests indicated that the as-prepared CdS QDs sensitized WO3 platelike photoelectrodes exhibit a significant improvement in photocatalytic degradation and PEC activity under visible light irradiation, compared with unsupported CdS QDs electrodes. Significantly, coating the WO3 plates with nano-TiO2 obviously facilitate the charge separation and retards the charge-pair recombination, and results in a highest activity for QDs CdS/TiO2/WO3 photoelectrodes.

Li, Yan-jun; Wang, Ru; Han, Yue-xin; Wei, Xin-chao

doi: 10.1007/s11771-015-3006-8pmid: N/A

Suspension roasting followed by magnetic separation is a promising method to upgrade oolitic hematite ore. An oolitic hematite ore was roasted using suspension roasting technology at different temperatures. The phase transformation for iron minerals was investigated by XRD and Mossbauer spectrum, and the characteristics of roasted product were analyzed by VSM and SEM-EDS. Results indicate that the magnetic concentrate is of 58.73% Fe with iron recovery of 83.96% at 650 °C. The hematite is rapidly transformed into magnetite during the roasting with transformation ratio of 92.75% at 650 °C. Roasting temperature has a significant influence on the phase transformation of hematite to magnetite. The transformation ratio increases with increased temperature. After roasting, the magnetic susceptibility is significantly improved, while iron ore microstructure is not altered significantly.

Li, Kun; Pan, Bo; Gao, Wen-peng; Feng, Hai-bo; Fu, Yi-li; Wang, Shu-guo

doi: 10.1007/s11771-015-3007-7pmid: N/A

In order to restore force sensation to robot-assisted minimally invasive surgery (RMIS), design and performance evaluation of a miniature 6-axis force/torque sensor for force feedback is presented. Based on the resistive sensing method, a flexural-hinged Stewart platform is designed as the flexible structure, and a straightforward optimization method considering the force and sensitivity isotropy of the sensor is proposed to determine geometric parameters which are best suited for the given external loads. The accuracy of this method is preliminarily discussed by finite element methods (FEMs). The sensor prototype is fabricated with the development of the electronic system. Calibration and dynamic loading tests for this sensor prototype are carried out. The working ranges of this sensor prototype are 30 N and 300 N·mm, and resolutions are 0.08 N in radial directions, 0.25 N in axial direction, and 2.4 N·mm in rotational directions. It also exhibits a good capability for a typical dynamic force sensing at a frequency close to the normal heart rate of an adult. The sensor is compatible with surgical instruments for force feedback in RMIS.

Tian, Bao-qiang; Yu, Jian-cheng; Zhang, Ai-qun

doi: 10.1007/s11771-015-3008-6pmid: N/A

Wave driven unmanned surface vehicle (WUSV) is a new concept ocean robot drived by wave energy and solar energy, and it is very suitable for the vast ocean observations with incomparable endurance. Its dynamic modeling is very important because it is the theoretical foundation for further study in the WUSV motion control and efficiency analysis. In this work, the multibody system of WUSV was described based on D-H approach. Then, the driving principle was analyzed and the dynamic model of WUSV in longitudinal profile is established by Lagrangian mechanics. Finally, the motion simulation of WUSV and comparative analysis are completed by setting different inputs of sea state. Simulation results show that the WUSV dynamic model can correctly reflect the WUSV longitudinal motion process, and the results are consistent with the wave theory.