To improve the wear resistance and corrosion resistance of magnesium alloys, a 5 kW continuous wave CO2 laser was used to investigate the laser surface cladding on AZ31 B magnesium alloys with Al-Si/Al2O3-TiO2 composi...To improve the wear resistance and corrosion resistance of magnesium alloys, a 5 kW continuous wave CO2 laser was used to investigate the laser surface cladding on AZ31 B magnesium alloys with Al-Si/Al2O3-TiO2 composite powders. A detailed microstructure, chemical composition, and phase analysis of the composite coatings were studied by scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, and X-ray diffraction （XRD）. The laser cladding shows good metallurgical bonding with the substrate. The composite coatings are composed of Mgl7Al12, Al3Mg2, Mg2Si, Al2O3, and TiO2 phases. Compared to the average microhardness （50HV0.05） of the AZ3 1 B substrate, that of the composite coatings （230HV0.05） is improved significantly. The wear resistances of the surface layers were evaluated in detail. The results demonstrate that the wear resistances of the laser surface-modified samples are considerably improved compared to the substrate. It also show that the composite coatings exhibit better corrosion resistance than that of the substrate in 3.5wt% NaCI solution.展开更多
Biodegradable magnesium-based alloys are very promising materials for temporary implants. Laser welding is an important joining method in such application. In this study, the as-rolled AZ31B magnesium alloy sheets of ...Biodegradable magnesium-based alloys are very promising materials for temporary implants. Laser welding is an important joining method in such application. In this study, the as-rolled AZ31B magnesium alloy sheets of 1 mm in thickness were successfully joined by Nd ： YAG laser welding. The microstructure and properties of the welded joint were investigated. The result shows that the welded joint is characterized by a narrow heat-affected zone, finer grains and a large number of precipitates distribute in the matrix in the weld. Microhardness of the weld is significantly improved to 72 HV 0. 05 as compared to 55 HV 0. 05 of the base metal. Tensile strength of butt-welded joint is 180. 24 MPa, which is 76. 8% that of the base metal. The electrochemical corrosion experiment shows that the corrosion resistance of laser welded joint is significantly improved in a 3.5 wt. % NaCl solution.展开更多
Mg matrix composites with SiC particles ranging from 5vol%-25vol% were prepared using stirring casting method. Die casting, squeezing casting, and extrusion were applied for inhibiting or eliminating the defects such ...Mg matrix composites with SiC particles ranging from 5vol%-25vol% were prepared using stirring casting method. Die casting, squeezing casting, and extrusion were applied for inhibiting or eliminating the defects such as gas porosity and shrinkage void. Through die casting and squeezing casting, most of the defects in Mg matrix composites could be eliminated, but the mechanical properties were improved limitedly. On the other hand, after hot extrusion, not only most of the defects of as-cast composites ingots were eliminated, but also the mechanical properties were improved markedly. With the addition of SiC, the tensile strength, yield strength and elastic modulus of as extrusion SiCp/AZ61 composites increased remarkably, and the elongation decreased obviously.展开更多
A hybrid material of carbon microspheres（CMSs） with Ag decoration（Ag/CMSs） was developed.Poly（3-hexylthiophene）：Ag/CMSs composite film was prepared by spin-coating.Scanning electron microscopy,transmission elec...A hybrid material of carbon microspheres（CMSs） with Ag decoration（Ag/CMSs） was developed.Poly（3-hexylthiophene）：Ag/CMSs composite film was prepared by spin-coating.Scanning electron microscopy,transmission electron microscopy,Fourier transform infrared spectrometry,X-ray diffraction,thermogravimetric analysis and cyclic voltammetry were employed to analyze the morphologies,structures,thermal properties and energy levels of Ag/CMSs.The optical property of the composite films was characterized by ultraviolet-visible spectrophotometry and fluorescent spectrometry.The results indicate that silver nanoparticles（AgNPs,d = 10-20 nm） are distributed on the surface of CMSs.LUMO and HOMO energy levels of Ag/CMSs are-3.97 and-5.52 e V,below the vacuum energy level,respectively,indicating that it is feasible to use Ag/CMSs as an electron acceptor.Ag NPs are blended into the active layer to trigger localized surface plasmon resonance,and consequently enhance light harvesting.The coupling of surface plasmons and excitons increased the probability of exciton dissociation.展开更多
Co-precipitation compound precursors-hydrothermal processing was employed to synthesize Ni/Cu/A12OJZrO2 composite powder, and ZrO2-based composite ceramics was prepared. The technology recycled the metal of nickel, co...Co-precipitation compound precursors-hydrothermal processing was employed to synthesize Ni/Cu/A12OJZrO2 composite powder, and ZrO2-based composite ceramics was prepared. The technology recycled the metal of nickel, copper and aluminum from sludge, and the recovery rate of nickel was up to 95.5%. The property of ZrO2-based composite ceramics was improved because of the existence of nickel and copper particles. The fracture toughness of Ni/Cu/A12OJZrO2 composite ceramics was 8.52 MPa·m1/2 and the compressive strength was 51 MPa, showing the increase by 2.54 times and 1.5 times, respectively, compared with those of pure ZrO2 ceramics.展开更多
Good ignition-proof principle and mechanical properties were realized in Mg-Y-Ca-Zr alloy system.By adding Y and Ca elements,the ignition point of Mg-3.5Y-0.8Ca alloy was improved to over 1173 K,and the alloy could be...Good ignition-proof principle and mechanical properties were realized in Mg-Y-Ca-Zr alloy system.By adding Y and Ca elements,the ignition point of Mg-3.5Y-0.8Ca alloy was improved to over 1173 K,and the alloy could be melted in air without any protections.The ef-fect of Zr addition on the microstructures and mechanical properties of Mg-3.5Y-0.8Ca alloys were investigated,and Mg-3.5%Y-0.8%Ca-0.4%Zr alloy had good comprehensive properties with tensile strength of 190 MPa and elongation of 11%.Auger electron spectros-copy（AES） and X-ray diffraction（XRD） analysis revealed that the oxide film formed on the surface of Mg-3.5Y-0.8Ca alloy was mainly composed of Y2O3.Thermogravimetric measurements in dry air indicated that the oxidation dynamics curves measured at 773,873 and 973 K followed the cubic law.Moreover,the semiconductor characteristic of Y2O3 film and its effect on ignition-proof properties of Magnesium al-loys were discussed from the viewpoint of electrochemistry.展开更多
Titania-silica (TS) nanocomposite powder with three different composite structures, containing 10―30 mol% SiO2 in each structure, have been prepared by sol-gel processes. The surface characteristics of these titania-...Titania-silica (TS) nanocomposite powder with three different composite structures, containing 10―30 mol% SiO2 in each structure, have been prepared by sol-gel processes. The surface characteristics of these titania-silica samples have been investigated by X-ray photo-emission spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM). The study for all TS oxides annealed at 773 and 1173 K showed: an abnormal surface enrichment in Si increased with increasing annealing temperature; the Ti3+, Ti2+, Si3+ and Si2+ oxides coexisted with Ti4+ and Si4+ oxides, and the contents of these Ti/Si suboxides increased with increasing SiO2 content and annealing temperature; there was a layer rich in O on the topmost surface and the excess O could be attributed to the chemadsorption of H2O; different composite structures could lead to different contents of Ti/Si suboxides. These results indi- cated that the surface of TS oxide powder derived by sol-gel process was a double layer with enriched O first and then SiOx/TiOy (x, y<2). Ti/Si suboxides could result from the thermal diffusion of Ti4+ and Si4+, which might be induced by the strong interaction between Ti4+ and Si4+.展开更多
基金Funded by the national Natural Science Foundation of China (No. 51075293)the Foundation for Development of Science and Technology of Taiyuan University of Technology,China(No.K201014)
文摘To improve the wear resistance and corrosion resistance of magnesium alloys, a 5 kW continuous wave CO2 laser was used to investigate the laser surface cladding on AZ31 B magnesium alloys with Al-Si/Al2O3-TiO2 composite powders. A detailed microstructure, chemical composition, and phase analysis of the composite coatings were studied by scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, and X-ray diffraction （XRD）. The laser cladding shows good metallurgical bonding with the substrate. The composite coatings are composed of Mgl7Al12, Al3Mg2, Mg2Si, Al2O3, and TiO2 phases. Compared to the average microhardness （50HV0.05） of the AZ3 1 B substrate, that of the composite coatings （230HV0.05） is improved significantly. The wear resistances of the surface layers were evaluated in detail. The results demonstrate that the wear resistances of the laser surface-modified samples are considerably improved compared to the substrate. It also show that the composite coatings exhibit better corrosion resistance than that of the substrate in 3.5wt% NaCI solution.
基金The work was supported by the National Natural Science Foundation of China （ Grant No. 51305292 ） and the Aviation Science Foundation （ Grant No. 20105429001 ）.
文摘Biodegradable magnesium-based alloys are very promising materials for temporary implants. Laser welding is an important joining method in such application. In this study, the as-rolled AZ31B magnesium alloy sheets of 1 mm in thickness were successfully joined by Nd ： YAG laser welding. The microstructure and properties of the welded joint were investigated. The result shows that the welded joint is characterized by a narrow heat-affected zone, finer grains and a large number of precipitates distribute in the matrix in the weld. Microhardness of the weld is significantly improved to 72 HV 0. 05 as compared to 55 HV 0. 05 of the base metal. Tensile strength of butt-welded joint is 180. 24 MPa, which is 76. 8% that of the base metal. The electrochemical corrosion experiment shows that the corrosion resistance of laser welded joint is significantly improved in a 3.5 wt. % NaCl solution.
基金Funded by the Program for New Century Excellent Talents in University(NCET-12-1040)the National Natural Science Foundation of China(Nos.50901048 and 51174143)+2 种基金the Key Project of Chinese Ministry of Education(No.2012017)the Program Foundation of Ministry of Education of China(No.20101402110008)Natural Science Foundation of Shanxi(No.2010021022-5)
文摘Mg matrix composites with SiC particles ranging from 5vol%-25vol% were prepared using stirring casting method. Die casting, squeezing casting, and extrusion were applied for inhibiting or eliminating the defects such as gas porosity and shrinkage void. Through die casting and squeezing casting, most of the defects in Mg matrix composites could be eliminated, but the mechanical properties were improved limitedly. On the other hand, after hot extrusion, not only most of the defects of as-cast composites ingots were eliminated, but also the mechanical properties were improved markedly. With the addition of SiC, the tensile strength, yield strength and elastic modulus of as extrusion SiCp/AZ61 composites increased remarkably, and the elongation decreased obviously.
基金Funded by the National Natural Science Foundation of China(21176169)the Shanxi Provincial Key Innovative Research Team in Science and Technology(2012041011,2015013002-10)+1 种基金the International Science&Technology Cooperation Program of China(2012DFR50460)the Research Project Supported by Shanxi Scholarship Council of China(2012-038)
文摘A hybrid material of carbon microspheres（CMSs） with Ag decoration（Ag/CMSs） was developed.Poly（3-hexylthiophene）：Ag/CMSs composite film was prepared by spin-coating.Scanning electron microscopy,transmission electron microscopy,Fourier transform infrared spectrometry,X-ray diffraction,thermogravimetric analysis and cyclic voltammetry were employed to analyze the morphologies,structures,thermal properties and energy levels of Ag/CMSs.The optical property of the composite films was characterized by ultraviolet-visible spectrophotometry and fluorescent spectrometry.The results indicate that silver nanoparticles（AgNPs,d = 10-20 nm） are distributed on the surface of CMSs.LUMO and HOMO energy levels of Ag/CMSs are-3.97 and-5.52 e V,below the vacuum energy level,respectively,indicating that it is feasible to use Ag/CMSs as an electron acceptor.Ag NPs are blended into the active layer to trigger localized surface plasmon resonance,and consequently enhance light harvesting.The coupling of surface plasmons and excitons increased the probability of exciton dissociation.
基金Funded by the International Cooperation Program of Shanxi Province(No. 2009081046)Program for Changjiang Scholar and Innovative Research Team in University(No.IRT0972)Key Laboratory of Materials Interface Science and Engineering, Ministry of Education, Taiyuan University of Technology, Taiyuan Shanxi,China
文摘Co-precipitation compound precursors-hydrothermal processing was employed to synthesize Ni/Cu/A12OJZrO2 composite powder, and ZrO2-based composite ceramics was prepared. The technology recycled the metal of nickel, copper and aluminum from sludge, and the recovery rate of nickel was up to 95.5%. The property of ZrO2-based composite ceramics was improved because of the existence of nickel and copper particles. The fracture toughness of Ni/Cu/A12OJZrO2 composite ceramics was 8.52 MPa·m1/2 and the compressive strength was 51 MPa, showing the increase by 2.54 times and 1.5 times, respectively, compared with those of pure ZrO2 ceramics.
基金Project supported by the National Natural Science Foundation of China (50901048,51174143)the fund of the State Key Laboratory of Solidification Processing in NWPU (SKLSP201003)+1 种基金Program for Changjiang Scholar and Innovative Research Team in University (IRT0972)Program for the Top Young Academic Leaders of Higher Learning Institutions of Shanxi and Natural Science Foundation of Shanxi (2010021022-5)
文摘Good ignition-proof principle and mechanical properties were realized in Mg-Y-Ca-Zr alloy system.By adding Y and Ca elements,the ignition point of Mg-3.5Y-0.8Ca alloy was improved to over 1173 K,and the alloy could be melted in air without any protections.The ef-fect of Zr addition on the microstructures and mechanical properties of Mg-3.5Y-0.8Ca alloys were investigated,and Mg-3.5%Y-0.8%Ca-0.4%Zr alloy had good comprehensive properties with tensile strength of 190 MPa and elongation of 11%.Auger electron spectros-copy（AES） and X-ray diffraction（XRD） analysis revealed that the oxide film formed on the surface of Mg-3.5Y-0.8Ca alloy was mainly composed of Y2O3.Thermogravimetric measurements in dry air indicated that the oxidation dynamics curves measured at 773,873 and 973 K followed the cubic law.Moreover,the semiconductor characteristic of Y2O3 film and its effect on ignition-proof properties of Magnesium al-loys were discussed from the viewpoint of electrochemistry.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 20776091 and 90306014)
文摘Titania-silica (TS) nanocomposite powder with three different composite structures, containing 10―30 mol% SiO2 in each structure, have been prepared by sol-gel processes. The surface characteristics of these titania-silica samples have been investigated by X-ray photo-emission spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM). The study for all TS oxides annealed at 773 and 1173 K showed: an abnormal surface enrichment in Si increased with increasing annealing temperature; the Ti3+, Ti2+, Si3+ and Si2+ oxides coexisted with Ti4+ and Si4+ oxides, and the contents of these Ti/Si suboxides increased with increasing SiO2 content and annealing temperature; there was a layer rich in O on the topmost surface and the excess O could be attributed to the chemadsorption of H2O; different composite structures could lead to different contents of Ti/Si suboxides. These results indi- cated that the surface of TS oxide powder derived by sol-gel process was a double layer with enriched O first and then SiOx/TiOy (x, y<2). Ti/Si suboxides could result from the thermal diffusion of Ti4+ and Si4+, which might be induced by the strong interaction between Ti4+ and Si4+.
