2015年 2期 (共 篇) 引用文章 全选
Influence of pouring temperature on solidification behavior, microstructure and mechanical properties of sand-cast Mg-10Gd-3Y-0.4Zr alloy - TNMSC
本平台内已出版文章查询 , Guo-hua WU 已出版文章查询
本平台内已出版文章查询 , Wen-cai LIU 已出版文章查询
本平台内已出版文章查询 , Liang ZHANG 已出版文章查询
本平台内已出版文章查询 , Yang ZHANG 已出版文章查询
本平台内已出版文章查询 , Hans CONRAD 已出版文章查询
本平台内已出版文章查询 , Wen-jiang DING 已出版文章查询
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Influence of the pouring temperature ranging from 680 to 780 °C on the solidification behavior, the microstructure and mechanical properties of the sand-cast Mg-10Gd-3Y-0.4Zr alloy was investigated. It was found that the nucleation undercooling of the α-Mg phase increased from 2.3 to 6.3 °C. The average α-Mg grain size increased from 44 to 71 μm, but then decreased to 46 μm. The morphology of the eutectic compound transformed from a continuous network into a discontinuous state and then subsequently into an island-like block. The volume fraction of β-Mg24RE5 phase increased and its morphology transformed from particle into rod-like. The increase in pouring temperature increased the solute concentration. YS increased from 138 to 151 MPa, and UTS increased from 186 to 197 MPa. The alloy poured at 750 °C had optimal combining strength and ductility. The fracture surface mode transformed from quasi-cleavage crack into transgranular fracture, all plus the dimple-like fracture, with the micro-porosity and the re-oxidation inclusion as major defects. The average α-Mg grain size played a main role in the YS of sand-cast Mg-10Gd-3Y-0.4Zr alloy, besides other factors, i.e. micro-porosity, morphology of eutectic compounds, re-oxidation inclusion and solute concentration.
Effect of multi-step slow shot speed on microstructure of vacuum die cast AZ91D magnesium alloy - TNMSC
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Two multi-step (two-step and three-step) slow shot speeds were used in the vacuum die casting process of AZ91D magnesium alloy. The vacuum pressure variation in the die cavity before mold filling was monitored by using a pressure sensor. The microstructures of the produced castings were analyzed with optical microscope and image analysis software. The experimental results demonstrate that, the vacuum pressure in the die cavity at the beginning of mold filling is significantly reduced by using three-step slow shot speed, resulting in a low gas porosity level in the produced castings. At an appropriate multi-step slow shot speed, the dwell time of the liquid metal in the shot sleeve before mold filling can be reduced and the flow of the liquid metal in the shot sleeve at the later stage of the slow shot process can be restrained, which cause a low externally solidified crystal content in the produced castings.
Microstructure and mechanical properties of AZ61 magnesium alloy prepared by repetitive upsetting-extrusion - TNMSC
本平台内已出版文章查询 , Lian-xi HU 已出版文章查询
本平台内已出版文章查询 , Yu SUN 已出版文章查询
本平台内已出版文章查询 , Jian-bo JIA 已出版文章查询
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本平台内已出版文章查询 , Ju-fu JIANG 已出版文章查询
本平台内已出版文章查询 , Qing-guo MA 已出版文章查询
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The process of repetitive upsetting-extrusion (RUE) was used to achieve severe plastic deformation (SPD) for an as-cast AZ61 magnesium alloy in temperature range of 285-380 °C. The microstructure and mechanical properties of the as-cast and RUE processed AZ61 alloys were investigated. The results indicated that homogeneous fine-grained structure with mean grain size of 3.5 μm was obtained as the accumulated true strain in the axial direction increased to 4.28 after three RUE passes at 285 °C. The dominant reason of grain refinement was considered the dynamic recrystallization induced by strain localization. It was also found that the microstructural evolution was affected by temperature and accumulated deformation. The mechanical properties of RUE processed AZ61 alloys were significantly improved owing to grain refinement. Furthermore, the relationship between deformation parameters and mechanical properties of AZ61 alloy prepared by RUE processing was revealed by tensile tests carried out at room temperature.
Microstructures and mechanical properties of laser welded wrought fine-grained ZK60 magnesium alloy - TNMSC
本平台内已出版文章查询 , Qiang ZHAO 已出版文章查询
本平台内已出版文章查询 , Ping CHEN 已出版文章查询
本平台内已出版文章查询 , Ji-hua CHEN 已出版文章查询
本平台内已出版文章查询 , Bin SU 已出版文章查询
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Fine-grained ZK60 magnesium alloy sheets of 2.0 mm in thickness were successfully joined by laser beam welding (LBW). The effects of welding parameters including laser power and welding speed on the microstructures and mechanical properties of the joints were investigated. A sound bead, with the ultimate tensile strength (UTS) of 300 MPa and elongation of 12.0%, up to 92.5% and 65% of those of the base metal, respectively, is obtained with the optimized welding parameters. No liquation cracking is visible in the partially melted zone (PMZ) owing to the inhibitory action of the fine dispersed precipitates and the fine-grained microstructure in the as-rolled magnesium alloy sheets. The fusion zone (FZ) is featured with the equiaxed dendritic grains of the average grain size about 8 μm, which are similar to those in the heat affected zone (HAZ), and this contributes to the relatively high joint efficiency.
Influence of high frequency vibration on microstructure and mechanical properties of TIG welding joints of AZ31 magnesium alloy - TNMSC
本平台内已出版文章查询 , Shi-yao LIU 已出版文章查询
本平台内已出版文章查询 , Shi CHEN 已出版文章查询
本平台内已出版文章查询 , Lan-tao LIU 已出版文章查询
本平台内已出版文章查询 , Chen YANG 已出版文章查询
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A device for superimposing vibration on workpiece in both horizontal and vertical directions during tungsten-arc inert gas (TIG) welding was developed, with maximum power output of 2 kW at frequency of 15 kHz. AZ31 sheets with thickness of 1 and 3 mm were used in the vibratory welding. Microstructures along with the mechanical properties of the weld joints under different vibrating conditions (vibration direction, vibration amplitude and groove angle) were examined. It is observed that the grain size in welding zone decreases remarkably with the application of vibration, while the amount of second phase β-Mg17Al12 within the zone decreases slightly; meanwhile, microhardness of the weld joints, macroscopic tensile strength and elongation of the weldment increase. Vibration, especially the one along vertical direction, has more impact on the performance of the thick weldments. Influence of vibration on microstructure and mechanical properties of weldments is affected by wave energy transferring in the melt and depends on the processing and geometric parameters including amplitude and direction of vibration, thickness, and groove angles.
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The solid-liquid interfacial morphology evolution was investigated in directional solidification (DS) of Al-1.5%Cu alloy (mass fraction). The results show that the solidified microstructural evolution is gradual other than sharp, and the microstructure patterns are interesting and diversiform at the pulling rate ranging from 30 mm/s to 1500 mm/s. Indeed, dendrite to cell transition follows this sequence: dendrites→banded cellular dendrites→elongated cells and part of dendrites→main elongated cells and little dendrites. Moreover, the present microstructure is not normal microstructure as we saw before. Further, according to the experimental phenomenon, the dendrite to cell transition was studied theoretically. Dendrite tip shape is an important parameter to characterize the dendrite to cell transition. As the dendrite to cell transition is far from equilibrium solidification, non-equilibrium solidification is taken into consideration in calculation. Finally, it is speculated that the dendrite to cell transition would occur at the minimum tip radius.
本平台内已出版文章查询 , Bin-bin TANG 已出版文章查询
本平台内已出版文章查询 , Pei-peng JIN 已出版文章查询
本平台内已出版文章查询 , Lei ZHANG 已出版文章查询
本平台内已出版文章查询 , Wei-dong FEI 已出版文章查询
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The 6061 aluminum matrix composites reinforced with ZnO-coated Mg2B2O5w were fabricated by squeeze casting method and followed by extruded under a technical equivalent condition. The mechanical properties and microstructures of the composites were investigated. The results showed that the elastic modulus of the as-cast composites increased straightly with increasing ZnO coating content. The ultimate tensile strength and yield strength of the as-cast composites rapidly increased initially and then declined with increasing ZnO coating content. However, the elongations of all the as-cast composites had similar values. The elongations of the composites were highly enhanced and the ultimate tensile strength of the composite without ZnO coating was the largest after extrusion. A number of whiskers in the composites with ZnO coating were fractured during the extrusion process, but the whiskers’ breakage extent was limited with the increase of coating content.
本平台内已出版文章查询 , Dong-sheng LI 已出版文章查询
本平台内已出版文章查询 , Xiao-qiang LI 已出版文章查询
本平台内已出版文章查询 , Pan DING 已出版文章查询
本平台内已出版文章查询 , Kai ZHAO 已出版文章查询
本平台内已出版文章查询 , Xuan-zhao HUANG 已出版文章查询
本平台内已出版文章查询 , Ming-jin XU 已出版文章查询
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Hot stretch-creep forming (SCF) is a novel technique to produce hard-to-form thin-walled metal components. Comprehensively considering the analysis results of the springback angle, yield strength and microstructure, four hot SCF process parameters including temperature, stretch velocity, post stretch percentage and dwelling time of a Ti-6Al-4V alloy sheet were optimized using an orthogonal experiment. The results reveal that temperature is the most important factor on springback angle. The yield strength of the deformed material in 0° direction increases, while those in directions of 45° and 90° fluctuate around the original value. After hot SCF, the shape of some a phases changes from short thin grains to long slender ones, and the microhardness changes very little. The optimized parameters with temperature of 700 °C, stretch velocity of 5 mm/min, post stretch percentage of 2% and dwelling time of 8 min are achieved finally.
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Terminal ballistic tests using 7.62 mm armor-piercing incendiary (API) projectiles were performed to evaluate the resistance to penetration of Ti-5Al-5Mo-5V-3Cr-1Zr (Ti-55531) alloy. The dynamic properties were determined by a split Hopkinson pressure bar (SHPB) test system. Ti-55531 plates were subjected to two kinds of heat treatments, leading to the formation of high-strength and high-toughness plates. The results of SHPB test exhibit that the maximum impact absorbed energy of the high-strength plate at a strain rate of 2200 s-1 is 270 MJ/m3; however, the maximum value for the high-toughness plate at a strain rate of 4900 s-1 is 710 MJ/m3. The ballistic limit velocities for the high-strength and high-toughness plates with dimensions of 300 mm×300 mm×8 mm are 330 and 390 m/s, respectively. Excellent dynamic properties of Ti-55531 alloy correspond to good resistance to penetration. The microstructure evolution related to various impact velocities are observed to investigate the failure mechanism.
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Boronizing was applied to Inconel 718. In order to obtain the optimal combination of strength and ductility, the borided Inconel 718 was subjected to standard heat treatment. This consists of solution treatment and then a two-step aging treatment. The borided layer is composed of the compound layer and the boron diffusion zone. Because of the superior hardness of borides, the borided Inconel 718 exhibits a significant reduction in its wear rate and relatively low coefficient of friction (COF) compared with the unborided Inconel 718. The standard heat treatment efficiently promotes the diffusion of boron into the interior of the material and the generation of new borides (Fe2B, CrB). The borided layer with standard heat treatment shows much better wear resistance due to the thicker borided layer (313.76 μm).
High temperature mechanical behavior of alumina dispersion strengthened copper alloy with high content of alumina - TNMSC
本平台内已出版文章查询 , Zhou LI 已出版文章查询
本平台内已出版文章查询 , Qian LEI 已出版文章查询
本平台内已出版文章查询 , Zhu XIAO 已出版文章查询
本平台内已出版文章查询 , Yong PANG 已出版文章查询
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The microstructure and its effects on the high temperature mechanical behavior of Cu-2.7%Al2O3 (volume fraction) dispersion strengthened copper (ADSC) alloy were investigated. The results indicate that fine alumina particles are uniformly distributed in the copper matrix, while a few coarse ones are distributed on the grain boundaries. Tensile tests results show that Hall-Petch mechanism is the main contribution to the yield strength of ADSC alloy at room temperature. Its high temperature strength is attributed to the strong pinning effects of alumina particles on the grain and sub-grain boundaries with dislocations. The ultimate tensile strength can reach 237 MPa and the corresponding yield strength reaches 226 MPa at 700 °C. Tensile fracture morphology indicates that the ADSC alloy shows brittleness at elevated temperatures. Creep tests results demonstrate that the steady state creep rates at 400 °C are lower than those at 700 °C. The stress exponents at 400 °C and 700 °C are 7 and 5, respectively, and the creep strain rates of the ADSC alloy are controlled by dislocation core diffusion and lattice diffusion.
Effects of surface roughness of substrate on properties of Ti/TiN/Zr/ZrN multilayer coatings - TNMSC
本平台内已出版文章查询 , Ke-song ZHOU 已出版文章查询
本平台内已出版文章查询 , Ming-jiang DAI 已出版文章查询
本平台内已出版文章查询 , Fang HU 已出版文章查询
本平台内已出版文章查询 , Qian SHI 已出版文章查询
本平台内已出版文章查询 , Hui-jun HOU 已出版文章查询
本平台内已出版文章查询 , Chun-bei WEI 已出版文章查询
本平台内已出版文章查询 , Fu-qiu LI 已出版文章查询
本平台内已出版文章查询 , Xin TONG 已出版文章查询
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Ti/TiN/Zr/ZrN multilayer coatings were deposited on Cr17Ni2 steel substrates with different surface roughnesses by vacuum cathodic arc deposition method. Microstructure, micro-hardness, adhesion strength and cross-sectional morphology of the obtained multilayer coatings were investigated. The results show that the Vickers hardness of Ti/TiN/Zr/ZrN multilayer coating, with a film thickness of 11.37 μm, is 29.36 GPa. The erosion and salt spray resistance performance of Cr17Ni2 steel substrates can be evidently improved by Ti/TiN/Zr/ZrN multilayer coating. The surface roughness of Cr17Ni2 steel substrates plays an important role in determining the mechanical and erosion performances of Ti/TiN/Zr/ZrN multilayer coatings. Overall, a low value of the surface roughness of substrates corresponds to an improved performance of erosion and salt spray resistance of multilayer coatings. The optimized performance of Ti/TiN/Zr/ZrN multilayer coatings can be achieved provided that the surface roughness of Cr17Ni2 steel substrates is lower than 0.4 μm.
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The thermal properties of a thermal barrier coating (TBC) system comprised of BaO–MgO–SiO2 based glass-ceramic bond coating, 8% (mass fraction) yttria stabilized zirconia (8YSZ) top coating and nimonic alloy substrate were evaluated. The thermal diffusivity and thermal conductivity of the TBC coated substrate were lower than those of bare substrate and glass-ceramic coated substrate under identical conditions. The specific heat capacity, thermal diffusivity and thermal conductivity of the TBC coated substrate increase with the increase of the temperature. Further, it is observed that the thermal conductivity of the TBC system decreases with the increase in the top coating thickness.
本平台内已出版文章查询 , Wen-zhang WANG 已出版文章查询
本平台内已出版文章查询 , Qi CUI 已出版文章查询
本平台内已出版文章查询 , Dong YE 已出版文章查询
本平台内已出版文章查询 , Ji MA 已出版文章查询
本平台内已出版文章查询 , Qing-ming CHEN 已出版文章查询
本平台内已出版文章查询 , Xiang LIU 已出版文章查询
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La0.72Ca0.28MnO3 thin films were deposited on untilted and 15° tilted LaAlO3 (100) single crystalline substrates by pulsed laser deposition. The polycrystalline targets used in the deposition process were synthesized by sol-gel and coprecipitation methods, respectively. The structure, electrical transport properties and surface morphology of the targets and films were studied. It is found that, compared with coprecipitation method, the sol-gel target has more homogeneous components and larger density and grain size, thus the higher insulator-metal transition temperature and larger temperature coefficient of resistivity. The thin film prepared by sol-gel target has a uniform grain size and higher quality. The metal-insulator transition temperature is higher and the laser induced voltage signal is larger. Preparing the target by sol-gel method can largely improve the properties of corresponding thin films in pulsed laser deposition process.
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Ta-containing TiO2 films with Ta contents of 5%, 20%, 33% (mole fraction) were sol-gel coated on the surface roughened Ti6Al4V alloy by dip coating method for biomedical applications. The Ta-TiO2 films on 1.5 mol/L NaOH-HCl pretreated substrate are adherent, but there are cracks for the sample with 33% Ta. X-ray photoelectron spectroscopy results show that Ti and Ta exist as TiO2 and Ta2O5 in the film, and Al element is not detectable. X-ray diffraction and Raman scattering analyses reveal that the addition of Ta decreases crystallization of the films. Potentiodynamic polarization test in a Ca-free Hank’s balanced solution demonstrates that the coating samples markedly improve the corrosion resistance compared with the polished sample. The addition of Ta impedes UV light-induced hydrophilic conversion of the coating samples. The sample with 20% Ta has enough film integrity and hydrophilic conversion rate, and is expected to possess good biological properties.
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Based on the Mg58.5Cu30.5Y11 alloy, 10% Ti, 10% Be and 10% Ti70Be30 (mole fraction) were respectively added to the alloy and samples with a diameter of 3 mm were fabricated by conventional Cu-mold casting method. The phase constituent, thermal stability and microstructure of the alloys were investigated by using X-ray diffraction, differential scanning calorimetry and scanning electron microscopy, respectively. The effects of alloying elements Ti and Be on the microstructure and mechanical properties of Mg58.5Cu30.5Y11 alloy were discussed. The results show that CuTi phase is distributed in (Mg0.585Cu0.305Y0.11)90Ti10 and (Mg0.585Cu0.305Y0.11)90(Ti0.7Be0.3)10 alloys, while CuYBe glassy phase containing CuY crystals is embedded in the matrix of (Mg0.585Cu0.305Y0.11)90Be10 alloy. Under uniaxial compressive loading, the largest compressive fracture strengths for (Mg0.585Cu0.305Y0.11)90Ti10, (Mg0.585Cu0.305Y0.11)90Be10 and (Mg0.585Cu0.305Y0.11)90(Ti0.7Be0.3)10 alloys are 797.6, 952.6 and 1007.8 MPa, respectively, and the strengths are increased by about 17%, 40% and 48% compared with Mg58.5Cu30.5Y11 alloy. The strength reliability for the three alloys is much improved according to the strength distribution region of 10 samples of each alloy.
Effect of cetyltrimethylammonium bromide on morphology and porous structure of mesoporous hydroxyapatite - TNMSC
本平台内已出版文章查询 , Su-ping HUANG 已出版文章查询
本平台内已出版文章查询 , Kun HU 已出版文章查询
本平台内已出版文章查询 , Ke-chao ZHOU 已出版文章查询
本平台内已出版文章查询 , Hong SUN 已出版文章查询
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The mesoporous hydroxyapatite (HA) was synthesized by hydrothermal method utilizing cationic surfactant cetyltrimethylammonium bromide (CTAB) as template. The crystalline phase, morphology and porous structure were characterized respectively by different detecting techniques. The results reveal that the particles are highly crystalline hydroxyapatite phase. The surfactant has little influence on the morphology of the crystals, but affects the porous structure obviously. The sample without CTAB has a low surface area not exceeding 33 m2/g, and no distinct pores can be observed by TEM. While the samples obtained with the surfactant get better parameters. Numerous open-ended pores centered at 2-7 nm spread unequally on the surface of the hydroxyapatite nanorods. The N2 adsorption-desorption experiments show type IV isotherms with distinct hysteresis loops, illustrating the presence of mesoporous structure. When the mole ratio of CTAB to HA is 1:2, the sample has the largest surface area of 97.1 m2/g and pore volume of 0.466 cm3/g.
本平台内已出版文章查询 , Yan-zhong ZHAO 已出版文章查询
本平台内已出版文章查询 , Juan TAN 已出版文章查询
本平台内已出版文章查询 , Shai-hong ZHU 已出版文章查询
本平台内已出版文章查询 , Ke-chao ZHOU 已出版文章查询
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In order to further improve the transfection efficiency of hydroxyapatite nanoparticle (HAp), arginine functionalized hydroxyapatite (HAp/Arg) was synthesized by hydrothermal synthesis. The morphology, crystallite size and zeta potential of the HAp/Arg were characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM) and zeta potential analyzer. The loading and protecting properties of HAp/Arg to DNA were tested by electrophoresis. Its cytotoxicity was also measured in Hela cells and HAEC cells by MTT and LDH, and its transfection efficiency was examined by fluorescence microscope and flow cytometry. The results reveal that HAp/Arg is short rod-like and nano single crystal, the mean diameter is 50-90 nm and zeta potential is 35.8 mV at pH 7.4. HAp/Arg to DNA can be condensed by electrostatic effect and protect DNA against degradation in DNase I, and shows high transfection efficiency without cytotoxicity. These results suggest that HAp/Arg can be a promising alternative as a novel gene delivery system.
Thermal decomposition of magnesium ammonium phosphate and adsorption properties of its pyrolysis products toward ammonia nitrogen - TNMSC
本平台内已出版文章查询 , Jian-jun TANG 已出版文章查询
本平台内已出版文章查询 , Wen-long LI 已出版文章查询
本平台内已出版文章查询 , Zhen-hui ZHONG 已出版文章查询
本平台内已出版文章查询 , Juan YIN 已出版文章查询
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High-purity magnesium ammonium phosphate (MAP) was precipitated by controlling pH value of the reaction system of 9.0-9.5. The thermal decomposition behavior of MAP and the adsorption properties of its pyrolysis products toward ammonia-nitrogen were also studied by XRD, SEM, TGA-DTA and FT-IR methods. The results indicated that high-purity MAP was obtained at pH value of 9.0-9.5. Upon heating to 100-120 °C for 120 min, MAP was thermally decomposed, losing water and ammonia concomitantly with a reduction in grain size and crystallinity. The capacity of pyrolysis products for ammonia nitrogen adsorption reached 72.5 mg/g, with a removal rate of up to 95% from an 800 mg/L solution. The characteristic diffraction peaks corresponding to MAP mainly appeared in their XRD patterns after adsorption of ammonia nitrogen. The pyrolysis products of MAP at 100-120 °C could be recycling-used as the chemical treatment regents of ammonia nitrogen in the practical application.
本平台内已出版文章查询 , Shu WANG 已出版文章查询
本平台内已出版文章查询 , Hai-ming SUN 已出版文章查询
本平台内已出版文章查询 , Xiao-bing WANG 已出版文章查询
本平台内已出版文章查询 , Jian-she LIAN 已出版文章查询
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Cu-doped TiO2 nanoparticles with different doping contents from 0 to 2.0% (mole fraction) were synthesized through sol-gel method. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscope (FE-SEM) were used to characterize the crystalline structure, chemical valence states and morphology of TiO2 nanoparticles. UV-Vis absorption spectrum was used to measure the optical absorption property of the samples. The photocatalytic performance of the samples was characterized by degrading 20 mg/L methyl orange under UV-Vis irradiation. The results show that the Cu-doped TiO2 nanoparticles exhibit a significant increase in photocatalytic performance over the pure TiO2 nanoparticles, and the TiO2 nanoparticles doped with 1.0% Cu show the best photocatalytic performance. The improvement in photocatalytic performance is attributed to the enhanced light adsorption in UV-Vis range and the decrease of the recombination rate of photoinduced electron-hole pair of the Cu-doped TiO2 nanoparticles.
本平台内已出版文章查询 , Jian-ming RUAN 已出版文章查询
本平台内已出版文章查询 , Zhong-cheng ZHOU 已出版文章查询
本平台内已出版文章查询 , Shang-bin SANG 已出版文章查询
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The effect of preparation routes on the physical characteristics and activity of the Ag-MnOx/C composites toward the oxygen reduction reaction (ORR) in alkaline media were studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy-dispersion spectroscopy (EDS) as well as scanning electron microscopy (SEM) and electrochemical techniques. The results show that more Ag and Mn species present on the surface of the Ag-MnOx/C composite prepared by two-step route (Ag-MnOx/C-2) compared to the one prepared by one-step route (Ag-MnOx/C-1), which contributes to its superior activity toward the ORR. The higher electron transfer number involved in the ORR can be observed on the Ag-MnOx/C-2 composite and its specific mass kinetic current at -0.6 V (vs Hg/HgO) is 46 mA/μg, which is 23 times that on the Ag/C. The peak power density of zinc-air battery with the Ag-MnOx/C-2 air electrode reaches up to 117 mW/cm2.
Julio Cesar Serafim CASINI
Julio Cesar Serafim CASINI
本平台内已出版文章查询 , Zai-ping GUO 已出版文章查询
本平台内已出版文章查询 , Hua Kun LIU 已出版文章查询
Hua Kun LIU
本平台内已出版文章查询 , Eliner Affonso FERREIRA 已出版文章查询
Eliner Affonso FERREIRA
本平台内已出版文章查询 , Rubens Nunes FARIA 已出版文章查询
Rubens Nunes FARIA
本平台内已出版文章查询 , Hidetoshi TAKIISHI 已出版文章查询
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The effects of substitution of Sn for Co on the microstructure, hydrogen storage and electrochemical discharge capacity of La0.7Mg0.3Al0.3Mn0.4Co0.5-xSnxNi3.8 (x=0, 0.1, 0.2, 0.3 and 0.5) alloys were investigated using X-ray diffraction (XRD), pressure composition isotherm (PCT) and electrochemical discharge cycle. XRD, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) tests showed that all of alloys are mainly composed of LaNi5 and MgNi2 phases, but when increasing the content of Sn in alloys, the LaNiSn phase appears and microstructure is refined. The PCT showed that increasing substitution of Sn for Co results in decrease of the maximum hydrogen storage capacity from 1.48% (x=0) to 0.85% (x=0.5). The electrochemical tests indicated that the maximum discharge capacity decreases from 337.1 mA？h/g (x=0) to 239.8 mA？h/g (x=0.5); however, the discharge capacity retention at the 100th cycle increases from 70.2% (x=0) to 78.0% (x=0.5).
本平台内已出版文章查询 , Feng WU 已出版文章查询
本平台内已出版文章查询 , Xu-guang GAO 已出版文章查询
本平台内已出版文章查询 , Zhen-tian LIU 已出版文章查询
本平台内已出版文章查询 , Hai-ming XIE 已出版文章查询
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A Co-Mg co-substituted LiNi0.87Co0.10Mg0.03O2 cathode material was prepared by a co-precipitation method. The prepared LiNi0.87Co0.10Mg0.03O2 exhibits excellent electrochemical properties, such as initial discharge capacities of 202.6 mA？h/g and 190.5 mA？h/g at 0.2C and 1C rate, respectively, in operating voltage range of 3.0-4.3 V (versus Li+/Li). The capacity retentions are 96.1% and 93.4% at 0.2C and 1C, respectively, after 50 cycles. Moreover, the cycle performance of the sample was investigated in a 053048-type square Li ion battery. This type of battery can keep 81.7% of initial capacity after 500 charge-discharge cycles at 1C rate, which is close to that of commercial LiCoO2 battery. Therefore, the as-prepared material is capable of such high energy applications as portable product power.
本平台内已出版文章查询 , Da-dong WEN 已出版文章查询
本平台内已出版文章查询 , Yuan-qi JIANG 已出版文章查询
本平台内已出版文章查询 , Yong-he DENG 已出版文章查询
本平台内已出版文章查询 , Ping PENG 已出版文章查询
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The rapid solidification processes of liquid Cu56Zr44 alloys at different cooling rates (γ) were simulated by a molecular dynamics (MD) method. In order to assess the influence of cooling rate on the clustering tendency and degree towards icosahedrons, a ten-indices’ cluster-type index method was suggested to characterize the local atomic structures in the super-cooled liquid and the rapidly solidified solid. And their clustering and ordering degrees as well as the packing density of icosahedral clusters were also evaluated by an icosahedral clustering degree (fI), the chemical order parameter (ηαβ) and densification coefficients (D0, DI and DIS), respectively. Results show that the main local atomic configurations in Cu56Zr44 alloy system are Z12 clusters centered by Cu, and most of which are (12 0 12 0 0 0 0 0 0 0) standard icosahedra and (12 0 8 0 0 0 2 2 0 0) as well as (12 2 8 2 0 0 0 0 0 0) defective icosahedra. Below glass transition temperature (Tg), these icosahedral clusters will be coalesced to various icosahedral medium-range orders (IMROs) by IS linkages, namely, icosahedral bond, and their number N, size n, order parameter ηαβ as well as spatial distributions vary with γ. As the cooling rate exceeds the critical value (γc) at which a glassy transition can take place, a lower cooling rate, e.g., γ1=101 K/ns, is demonstrated to be favorable to uplift the number of icosahedra and enlarge the size of IMROs compared with the higher cooling rates, e.g., γ5=105 K/ns, and their packing density and clustering degree towards icosahedra in the rapidly solidified solid can also benefit from the slow cooling process.
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With microscopic phase-field kinetic model, atomic-scale computer simulation program for the precipitation sequence and microstructure evolution of the ordered intermetallic compound γ′ and θ in ternary Ni75AlxV25-x alloy were studied. The simulation results show that Al concentration has important effects on the precipitation sequence. When Al concentration in Ni75AlxV25-x alloy is low, θ(Ni3V) ordered phase will be firstly precipitated, followed by γ′(Ni3Al) ordered phase. With Al concentration increasing, θ and γ′ ordered phases are simultaneously precipitated. With Al concentration further increasing, γ′ ordered phase is firstly precipitated, followed by θ ordered phase. There is a competition relationship between θ and γ′ ordered phases during growth and coarsening process. No matter which first precipitates, θ ordered phase always occupies advantage in the competition process of coarsening, thus, the microstructure with preferred orientation is formed.
本平台内已出版文章查询 , Xin-bo HE 已出版文章查询
本平台内已出版文章查询 , Rui-jie ZHANG 已出版文章查询
本平台内已出版文章查询 , Shi-di YANG 已出版文章查询
本平台内已出版文章查询 , Xuan-hui QU 已出版文章查询
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The evolution of stresses due to inhomogeneity in metal injection molding (MIM) parts during sintering was investigated. The sintering model of porous materials during densification process was developed based on the continuum mechanics and thermal elasto-viscoplastic constitutive law. Model parameters were identified from the dilatometer sintering experiment. The real density distribution of green body was measured by X-ray computed tomography (CT), which was regarded as the initial condition of sintering model. Numerical calculation of the above sintering model was carried out with the finite element software Abaqus, through the user-defined material mechanical behavior (UMAT). The calculation results showed that shrinkages of low density regions were faster than those of high density regions during sintering, which led to internal stresses. Compressive stresses existed in high density regions and tensile stresses existed in low density regions. The densification of local regions depended on not only the initial density, but also the evolution of stresses during the sintering stage.
本平台内已出版文章查询 , Liang-ju HE 已出版文章查询
本平台内已出版文章查询 , Pei-jie LI 已出版文章查询
本平台内已出版文章查询 , Yi-cong YE 已出版文章查询
本平台内已出版文章查询 , Xue FENG 已出版文章查询
本平台内已出版文章查询 , L. S. NOVIKOV 已出版文章查询
L. S. NOVIKOV
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Al-Sc and Al-Ti semi-infinite targets were impacted by high-speed projectiles at velocities of 0.8, 1.0, 1.2 and 1.5 km/s, respectively. It is found that the Al-Sc targets demonstrate more excellent ability to resist high-speed impact. It is concluded that different microstructures of Al-Sc and Al-Ti alloys, including different grain sizes and secondary particles precipitated in the matrix, result in their greatly different capabilities of resisting impact. Furthermore, the effect of the size range of nanoscale Al3Sc precipitate in Al-Sc alloy on the resistance of high-speed impact was investigated. In addition, computer simulations and validation of these simulations were developed which fairly accurately represented residual crater shapes/geometries. Validated computer simulations allowed representative extrapolations of impact craters well beyond the laboratory where melt and solidification occurred at the crater wall, especially for hypervelocity impact (>5 km/s).
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Slabbing failure often occurs in the surround rock near a deep underground excavation. The mechanism of slabbing failure is still unclear. In order to reveal the influence of the intermediate principal stress (σ2) on slabbing failure, true triaxial unloading compressive test was carried out based on the stress path of the underground engineering excavation, i.e., unloading the minimum principal stress (σ3), keeping σ2, increasing the maximum principal stress (σ1). The initiation and the propagation of slabbing fracture in rock specimens were identified by examining the acoustic emission (AE) and the infrared radiation characterization. The test results show that the failure modes of the granite and red sandstone specimens are changed from shear to slabbing with the increase of σ2. The AE characteristic of rock specimen under low σ2 is swarm type which is the main shock type under high σ2. The infrared radiation properties of rock specimen under different σ2 are also different. The temperature change area is just along the shear fracture such as the uniaxial compression. With the increase of σ2, the temperature change area is planar of rock specimen which proofs that the failure mode of rock specimen turns into slabbing.
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In order to reveal the nonlinear dynamics characteristics of unsteady self-heating process of sulfide ores, nine different kinds of sulfide ore samples from a pyrite mine in China were taken as experimental materials and their self-heating characteristics were measured in laboratory. Furthermore, the measured temperature was studied by integrating wavelet transform, nonlinear characteristic parameters extraction and fuzzy comprehensive evaluation. The results indicate that only the ore samples 1, 2, 6 and 9 have obvious self-heating phenomenon, and their self-heating initiative temperatures are 220 °C, 239 °C, 220 °C and 220 °C, respectively, which means that they are difficult to produce self-heating under normal mining conditions. The correlation dimension of self-heating process is fraction and the maximum Lyapunov exponent is positive, which means that it is feasible to study the self-heating process based on chaotic dynamics theory. The nonlinearities of self-heating process of these four samples (ore samples 1, 2, 6 and 9) are 0.8227, 0.7521, 0.9401 and 0.8827 respectively and the order of the samples according to these results is: sample 6, sample 9, sample 1, sample 2, which is consistent with the measured results of self-heating characteristics. Therefore, the nonlinearity method can be used to evaluate the self-heating tendency of sulfide ores, and it is an effective verification of the reliability of measured results.
本平台内已出版文章查询 , Jian-hua CHEN 已出版文章查询
本平台内已出版文章查询 , Yu-qiong LI 已出版文章查询
本平台内已出版文章查询 , Qian HE 已出版文章查询
本平台内已出版文章查询 , Bo-zeng WU 已出版文章查询
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Electronic structures of complex mineral jamesonite were studied using density functional theory method together with their flotation behavior. The flotation behavior of jamesonite is similar to that of stibnite, indicating good floatability at pH below 6 and easy depression with NaOH, especially with lime. In weak alkaline condition, the flotation behavior of jamesonite is close to that of galena. The coordination structure of Pb for jamesonite is more complex than that for galena. Sb in jamesonite possesses two coordinated modes, whereas Sb of stibnite is only 3-coordinated. Pb in galena is more active than that in jamesonite. Sb (3-coordination) in jamesonite is inactive, in contrast with that in stibnite. However, 4-coordination Sb in jamesonite is more active than 3-coordination Sb. HOMO orbitals of jamesonite and stibnite contain metal atoms, which contribute to the formation of adsorption configuration of CaOH+ when there is lime; therefore, jamesonite and stibnite are easily depressed by lime.
Treatment of copper-rich gold ore by cyanide leaching, ammonia pretreatment and ammoniacal cyanide leaching - TNMSC
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The treatment of a copper sulphide-bearing gold ore by direct cyanide leaching, ammonia pretreatment and ammoniacal cyanide leaching was investigated. Dissolution behaviour of gold and copper in these leaching systems was demonstrated. Severe interference by the copper containing sulphides with cyanide leaching of gold is observed at ρ(NaCN)≤5 g/L. This is consistent with speciation calculations. Ammonia pretreatment is shown to readily eliminate the copper interference, allowing almost complete extraction of gold with concomitantly low reagent consumption in subsequent cyanide leaching. In ammoniacal cyanide system, Box-Behnken experimental design shows the main and interaction effects of NH3, NaCN and Pb(NO3)2. The concentrations of NH3 and NaCN are statistically confirmed to be significant factors affecting extraction of gold while the effect of Pb(NO3)2 is limited. Increasing the concentration of NH3 improves the selectivity and extent of gold extraction and reduces the cyanide consumption. The contribution of reagent interactions to gold extraction is statistically insignificant. These findings highlight that ammonia pretreatment and ammonia-cyanide leaching are promising approaches for the treatment of gold ores with high copper sulphide content.
本平台内已出版文章查询 , Chong-yang LI 已出版文章查询
本平台内已出版文章查询 , Zhi-hong PENG 已出版文章查询
本平台内已出版文章查询 , Gui-hua LIU 已出版文章查询
本平台内已出版文章查询 , Qiu-sheng ZHOU 已出版文章查询
本平台内已出版文章查询 , Tian-gui QI 已出版文章查询
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Reaction behaviors of sulfur and iron compounds in sodium aluminate solutions were investigated. The results show that iron compounds can remarkably remove the S2- but cannot get rid of and in sodium aluminate solutions. The removal efficiency of S2- using ferrous compound and ferric compound can reach 86.10% and 92.70% respectively when the iron compounds were added with a molar ratio of 2:1 compared with the sulfur in liquors at 100 °C. Moreover, several same compounds are formed in those two desulfurization processes with ferrous or ferric compounds, including erdite, hematite, amorphous ferrous sulfide, polymerized sulfur-iron compounds and ferric sulfate. The major difference between these two processes is that the erdite generated from ferrous compounds at the initial reaction stage will convert to a sodium-free product FeS2 at the subsequent stage.
Role of hydrazine and hydrogen peroxide in aluminium hydroxide precipitation from sodium aluminate solution - TNMSC
N. K. SAHU
N. K. SAHU
本平台内已出版文章查询 , C. K. SARANGI 已出版文章查询
C. K. SARANGI
本平台内已出版文章查询 , B. DASH 已出版文章查询
本平台内已出版文章查询 , B. C. TRIPATHY 已出版文章查询
B. C. TRIPATHY
本平台内已出版文章查询 , B. K. SATPATHY 已出版文章查询
B. K. SATPATHY
本平台内已出版文章查询 , D. MEYRICK 已出版文章查询
本平台内已出版文章查询 , I. N. BHATTACHARYA 已出版文章查询
I. N. BHATTACHARYA
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Aluminium hydroxide precipitation from synthetic sodium aluminate solution was studied in the presence of hydrazine or hydrogen peroxide. The addition of low concentration of hydrazine is found to be effective, while higher amount of hydrogen peroxide is required to generate similar effect. XRD data confirm the product phase to be gibbsitic by nature. The scanning electron micrographs (SEM) show that agglomerated products form in the presence of hydrazine while fine discrete particles are produced with hydrogenperoxide. The probable mechanism of precipitation in the presence of hydrazine and hydrogen peroxide is also discussed.
Leaching and recovery of zinc from leaching residue of zinc calcine based on membrane filter press - TNMSC
本平台内已出版文章查询 , Cen-xuan PAN 已出版文章查询
本平台内已出版文章查询 , Gui-hua LIU 已出版文章查询
本平台内已出版文章查询 , Xue-ting WANG 已出版文章查询
本平台内已出版文章查询 , Guang-yu DOU 已出版文章查询
本平台内已出版文章查询 , Ke-song ZHU 已出版文章查询
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The feasibility of leaching and recovery of zinc from zinc leaching residue (ZLR) based on a membrane filter press (MFP) was investigated. Experimental results show that zinc calcines with particle sizes of less than 106 μm and chambers of widths of 30 mm are appropriate for establishing uniform filter cakes to obtain acceptable leaching and recovery results. The leaching of zinc from ZLR performed via washing at 90 to 96 °C for 90 min with spent electrolyte using a MFP results in a zinc extraction rate of 97%, and almost all of the zinc leached are recovered after water washing with MFP, thereby avoiding any loss in the ZLR. Compared with the traditional hot concentrated acid leaching process, the process based on MFP as a leaching reactor is able not only to ensure a high extraction rate but also to reduce the leaching time. Moreover, the thickening, pulping, second leaching, washing, filtering and pressing could be integrated and realized using a single MFP.
Preparation of potassium salt with joint production of spherical calcium carbonate from sintering dust - TNMSC
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Several physical and chemical detection methods were used to study the basic properties of sintering dust (ESP dust) collected from Baogang Steel Corporation. The result shows that the major constituents of the ESP dust are KCl, NaCl, Fe2O3 and Fe3O4. Water leaching experiment on the sintering dust shows that KCl in the ESP dust can be separated and recovered by water leaching and fractional crystallization. Component analysis of leaching solution indicates that the massive calcium sulfate in the leaching solution should be removed first in order to obtain the pure potassium salt. In order to provide theoretical guidance to inhibit the dissolution of calcium ions from the sintering dust, the water leaching experiment of ESP dust and the dissolution behavior of CaSO4 in the potassium chloride, sodium chloride, potassium sulfate and their mixed salt solution were studied. It is found that, a lower liquid-solid ratio should be chosen in the leaching process to inhibit the dissolution of calcium sulfate dehydrate. Using sodium carbonate solution as a precipitating agent, the influences of the concentration of sodium carbonate solution, reaction temperature, stirring speed and equilibrium time on the preparation of the spherical calcium carbonate were studied. Spherical calcium carbonate with good dispersing performance and grain size distribution in nanometer range of less than 10 μm was obtained. Furthermore, a potassium recovery process with joint production of spherical calcium carbonate was designed. This process is technically viable and considerable in economic benefit.
Separation and enrichment of elemental sulfur and mercury from hydrometallurgical zinc residue using sodium sulfide - TNMSC
本平台内已出版文章查询 , Xiao-lan CAI 已出版文章查询
本平台内已出版文章查询 , Ze-biao ZHANG 已出版文章查询
本平台内已出版文章查询 , Li-bo ZHANG 已出版文章查询
本平台内已出版文章查询 , Shi-xing WANG 已出版文章查询
本平台内已出版文章查询 , Jin-hui PENG 已出版文章查询
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The separation and enrichment of mercury and the recovery of elemental sulfur from flotation sulfur concentrate in zinc pressure leaching process were carried out by sodium sulfide leaching and carbon dioxide precipitating. The results show that the leaching rate of elemental sulfur is more than 98%, and 98.13% of mercury is enriched in the residue, under the optimized conditions of sodium sulfide concentration 1.5 mol/L, liquid/solid ratio 6:1 and leaching time 30 min at room temperature. In addition, the content of mercury is enriched 5.23 times that in the leaching residue. The elemental sulfur is precipitated from leaching solution under conditions of carbon dioxide flow rate 200 mL/min and blowing time 150 min, while solution is stirred adequately. The recovery efficiency of elemental sulfur reaches 97.67%, and the purity of elemental sulfur is 99.75%, meeting the requirements of industrial first-rate product standard according to the national standard of GB/T 2449-2006 (PRC).
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The adsorption of copper ions was investigated using pyrolusite ore as a low-cost alternative adsorbent source. Pyrolusite, which contains mainly MnO2, is a manganese ore. The effects of the initial concentration of copper(II) ions, initial pH of solution, adsorbent dosage and particle size on the adsorption process were examined. It was found that the percentage of the adsorbed copper increases with increasing the amount of adsorbent. It was observed that the maximum adsorption occurred at natural initial pH values for all copper concentrations. While the initial solution concentration, initial pH, contact time, stirring speed, particle size and adsorbent dosage were 2.5 mmol/L, natural, 180 min, 200 r/min, 120 μm and 6 g/L, respectively, the efficiency of copper adsorption on pyrolusite ore was 96.5%. The isotherm and kinetic studies relating to this adsorption process were also made. It was determined that the equilibrium data followed the Langmuir isotherm model while the process kinetic could be described by the pseudo-second order kinetic model.
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Corrosion behavior of brass coinage was investigated in synthetic sweat solution by electrochemical measurement and surface analysis methods including scanning electron microscope (SEM) and energy dispersive X-ray spectrometer (EDX). It is indicated that chloride ions in sweat solution accelerate the anodic active dissolution of brass, which is the main reason of pitting corrosion and dezincification corrosion. Meanwhile, lactic acid and ammonia water also promote the anode reaction. The corrosion products on the surface are mainly composed of basic copper chloride, cuprous oxide, the complex consisting of urea in association with copper, and few lactate ion. The kinetics of pitting corrosion development obeys the following equation of J0=0.3735(t+185.93)-1/2, and the process is controlled by dissolution of salt deposited on pit surface.
本平台内已出版文章查询 , Jian-zhang 已出版文章查询
本平台内已出版文章查询 , WANG 已出版文章查询
本平台内已出版文章查询 , Feng-yuan 已出版文章查询
本平台内已出版文章查询 , YAN 已出版文章查询
本平台内已出版文章查询 , Qing ZHANG 已出版文章查询
本平台内已出版文章查询 , Quan-an LI 已出版文章查询
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A systematic investigation was carried out to discuss the corrosion and tribocorrosion behaviors of Hastelloy C276 alloy sliding against Al2O3 pin in artificial seawater, using a pin-on-disk tribometer integrated with a potentiostat for electrochemical control. The results show that the great decrease of open circuit potential and three orders of magnitude increase of corrosion current density occur caused by friction. There are clearly synergistic effect between corrosion and wear, resulting in corrosion-induced-wear and wear-induced-corrosion in tribocorrosion process. The contribution of pure mechanical wear to total material loss exceeds 70% in all sliding conditions, so mechanical wear is the dominant factor during tribocorrosion. For considering synergistic effect between corrosion and wear, the contribution of wear-induced-corrosion to total material loss is not very high although corrosion rate is greatly accelerated by friction. The fraction of corrosion-induced-wear to the total material loss is high and in the range of 14.6%-20.5% under all sliding conditions.
Dynamic interacting relationships among international oil prices, macroeconomic variables and precious metal prices - TNMSC
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From the perspective of long-term and short-term, the methods of TY causality test, generalized impulse response function, variance decomposition were used to investigate the impacts of international oil prices and macroeconomic variables on Chinese gold, silver and platinum prices, but also the feedback effects of Chinese precious metal prices under this impact. The results show that international oil prices play an important role in precious metal price variation both in long-term and short-term, and exchange rate only has an effect in short-term, while interest rate is ineffective in predicting precious metal prices. In addition, precious metal prices have some feedback effects on international oil prices and interest rate in short-term.