In order to analyze the effect of voltage during micro-arc oxidation(MAO)on corrosion and wear properties of Ti6Al4V(TC4),the MAO technology was employed to treat TC4 samples fabricated by selective electron beam melt...In order to analyze the effect of voltage during micro-arc oxidation(MAO)on corrosion and wear properties of Ti6Al4V(TC4),the MAO technology was employed to treat TC4 samples fabricated by selective electron beam melting(SEBM)at the voltages of 400,420 and 450 V.The results show that the metastable anatase phase gradually transforms to rutile phase with oxidation time and temperature increasing.The surface morphology of coating contains numerous micropores with uniform size distribution.Cracks and pores over 10μm are found on MAO-TC4 sample with applied voltage of 450 V.The thickness of MAO coating is positively correlated with the voltage.The corrosion resistance and wear resistance are related to phase composition,micropore size distribution on the surface and film thickness.When the voltage is 420 V,the coating shows the smallest corrosion current density(0.960×10^-7 A/cm^2)and the largest resistance(7.17×10^5Ω·cm^2).Under the same load condition,the coating exhibits larger friction coefficient and wear loss than the TC4 substrate.With the increase of voltage,the wear mechanism of the coating changes from abrasive wear to adhesive wear,and the adhesive wear is intensified at applied voltage of 450 V,with a maximum friction coefficient of 0.821.展开更多
The effect of CaCO3 addition on the carbothermic reduction of nickel slag was studied,and the mechanism of CaCO3 in improving the reduction was analyzed.The results showed that when the CaCO3 content added to the slag...The effect of CaCO3 addition on the carbothermic reduction of nickel slag was studied,and the mechanism of CaCO3 in improving the reduction was analyzed.The results showed that when the CaCO3 content added to the slag was increased from 0 to 8 wt.%,initiation temperature of the carbothermic reaction decreased from 1100 to 1000℃,the temperature reaching the maximum reduction rate decreased from 1150 to 1100℃,and the reduction degree of the nickel slag increased from 58%to 88%.The iron particles in the reduced nickel slag were coarsened and the X-ray diffraction intensity of metallic iron peaks increased,confirming that the addition of CaCO3 was beneficial to the reduction of nickel slag and recovery of iron.展开更多
A systematic and green low-temperature sulfation roasting−water leaching strategy was put forward to achieve a very high fluorine removal rate of 97.82%for spent carbon cathode(SCC),which was believed as a hazardous s...A systematic and green low-temperature sulfation roasting−water leaching strategy was put forward to achieve a very high fluorine removal rate of 97.82%for spent carbon cathode(SCC),which was believed as a hazardous solid waste.And the carbon could be recycled with a purity of 90.29 wt.%in the flaky microstructure.Thermodynamic analysis and the results of SEM,XRD and EDS indicate that most of the fluoride could convert into water-soluble sulfate at low temperature.And the highest fluorine removal rate could be obtained when<0.15 mm SCC particles were mixed with sulfuric acid at a liquid-to-solid ratio of 1:1,and then roasted at 300℃ for 0.5 h.The sulfate was removed to purify the carbon via water-leaching process.Avrami exponents and corresponding activation energy for the roasting and leaching process demonstrated that both processes are controlled by diffusion.展开更多
The VO2 powders were prepared by hydrothermal synthesis.The effects of heat treatment conditions and Y-doping on the structure and phase transition temperature of VO2 were studied.The XRD,SEM and TEM results show that...The VO2 powders were prepared by hydrothermal synthesis.The effects of heat treatment conditions and Y-doping on the structure and phase transition temperature of VO2 were studied.The XRD,SEM and TEM results show that the heat treatment temperature has a significant effect on the crystal transformation of VO2 precursor.Increasing temperature is conducive to the transformation of precursor VO2(B)to ultrafine VO2(M).The Y-doping affects the structure of VO2.Y^3+can occupy the lattice position of V4+to form YVO4 solid solution,which can increase the cell parameters of VO2.Due to the lattice deformation caused by Y-doping,the aggregation of particles is prevented,and the grain is refined obviously.DSC curves show that Y-doping can reduce the phase transition temperature of VO2(M).After adding 9 at.%Y,the phase transition temperature can be reduced from 68.3 to 61.3℃.展开更多
The effect of B_(2)O_(3) content on the viscosity of SiO_(2)−MgO−FeO-based molten slag system was investigated using the rotating cylinder method.The evolution process of the melt structure under different contents of...The effect of B_(2)O_(3) content on the viscosity of SiO_(2)−MgO−FeO-based molten slag system was investigated using the rotating cylinder method.The evolution process of the melt structure under different contents of B_(2)O_(3) was comprehensively studied via FTIR spectroscopy and a model for calculating the degree of polymerization was developed.The results showed that the viscosity of the molten slag decreased with the addition of B_(2)O_(3),which had a slight effect when its content exceeded 3 wt.%.As the addition of B_(2)O_(3) increased from 0 to 4 wt.%,the break temperature of the slags decreased from 1152 to 1050℃ and the apparent activation energy decreased from 157.90 to 141.84 kJ/mol.The addition of B_(2)O_(3) to the molten slag destroyed the chain silicate structure to form a more cyclic borosilicate structure.The Urbain model was improved to calculate the viscosity of the SiO_(2)−MgO−FeO-based slags,and the values were in good agreement with the experimentally measured values.展开更多
基金Projects(51504191,51671152,51874225)supported by the National Natural Science Foundation of ChinaProject supported by the Fund of State Key Laboratory of Porous Metal Materials,China。
文摘In order to analyze the effect of voltage during micro-arc oxidation(MAO)on corrosion and wear properties of Ti6Al4V(TC4),the MAO technology was employed to treat TC4 samples fabricated by selective electron beam melting(SEBM)at the voltages of 400,420 and 450 V.The results show that the metastable anatase phase gradually transforms to rutile phase with oxidation time and temperature increasing.The surface morphology of coating contains numerous micropores with uniform size distribution.Cracks and pores over 10μm are found on MAO-TC4 sample with applied voltage of 450 V.The thickness of MAO coating is positively correlated with the voltage.The corrosion resistance and wear resistance are related to phase composition,micropore size distribution on the surface and film thickness.When the voltage is 420 V,the coating shows the smallest corrosion current density(0.960×10^-7 A/cm^2)and the largest resistance(7.17×10^5Ω·cm^2).Under the same load condition,the coating exhibits larger friction coefficient and wear loss than the TC4 substrate.With the increase of voltage,the wear mechanism of the coating changes from abrasive wear to adhesive wear,and the adhesive wear is intensified at applied voltage of 450 V,with a maximum friction coefficient of 0.821.
基金Projects(51774224,51574189) supported by the National Natural Science Foundation of China
文摘The effect of CaCO3 addition on the carbothermic reduction of nickel slag was studied,and the mechanism of CaCO3 in improving the reduction was analyzed.The results showed that when the CaCO3 content added to the slag was increased from 0 to 8 wt.%,initiation temperature of the carbothermic reaction decreased from 1100 to 1000℃,the temperature reaching the maximum reduction rate decreased from 1150 to 1100℃,and the reduction degree of the nickel slag increased from 58%to 88%.The iron particles in the reduced nickel slag were coarsened and the X-ray diffraction intensity of metallic iron peaks increased,confirming that the addition of CaCO3 was beneficial to the reduction of nickel slag and recovery of iron.
基金the Natural Science Foundation of Hunan Province,China(No.2020JJ1007).
文摘A systematic and green low-temperature sulfation roasting−water leaching strategy was put forward to achieve a very high fluorine removal rate of 97.82%for spent carbon cathode(SCC),which was believed as a hazardous solid waste.And the carbon could be recycled with a purity of 90.29 wt.%in the flaky microstructure.Thermodynamic analysis and the results of SEM,XRD and EDS indicate that most of the fluoride could convert into water-soluble sulfate at low temperature.And the highest fluorine removal rate could be obtained when<0.15 mm SCC particles were mixed with sulfuric acid at a liquid-to-solid ratio of 1:1,and then roasted at 300℃ for 0.5 h.The sulfate was removed to purify the carbon via water-leaching process.Avrami exponents and corresponding activation energy for the roasting and leaching process demonstrated that both processes are controlled by diffusion.
基金Projects(51404183,51504177)supported by the National Natural Science Foundation of China。
文摘The VO2 powders were prepared by hydrothermal synthesis.The effects of heat treatment conditions and Y-doping on the structure and phase transition temperature of VO2 were studied.The XRD,SEM and TEM results show that the heat treatment temperature has a significant effect on the crystal transformation of VO2 precursor.Increasing temperature is conducive to the transformation of precursor VO2(B)to ultrafine VO2(M).The Y-doping affects the structure of VO2.Y^3+can occupy the lattice position of V4+to form YVO4 solid solution,which can increase the cell parameters of VO2.Due to the lattice deformation caused by Y-doping,the aggregation of particles is prevented,and the grain is refined obviously.DSC curves show that Y-doping can reduce the phase transition temperature of VO2(M).After adding 9 at.%Y,the phase transition temperature can be reduced from 68.3 to 61.3℃.
基金financially supported by the National Natural Science Foundation of China (No.51774224)。
文摘The effect of B_(2)O_(3) content on the viscosity of SiO_(2)−MgO−FeO-based molten slag system was investigated using the rotating cylinder method.The evolution process of the melt structure under different contents of B_(2)O_(3) was comprehensively studied via FTIR spectroscopy and a model for calculating the degree of polymerization was developed.The results showed that the viscosity of the molten slag decreased with the addition of B_(2)O_(3),which had a slight effect when its content exceeded 3 wt.%.As the addition of B_(2)O_(3) increased from 0 to 4 wt.%,the break temperature of the slags decreased from 1152 to 1050℃ and the apparent activation energy decreased from 157.90 to 141.84 kJ/mol.The addition of B_(2)O_(3) to the molten slag destroyed the chain silicate structure to form a more cyclic borosilicate structure.The Urbain model was improved to calculate the viscosity of the SiO_(2)−MgO−FeO-based slags,and the values were in good agreement with the experimentally measured values.
