In order to improve the uniformity of both the concentration of gaseous reagent and the deposition of matrix within micro pores during the chemical vapor infiltration (CVI) process, a calculation modeling of gas phase...In order to improve the uniformity of both the concentration of gaseous reagent and the deposition of matrix within micro pores during the chemical vapor infiltration (CVI) process, a calculation modeling of gas phase diffusion transport within micro pores was established. Taken CH 3SiCl 3 as precursor for depositing SiC as example, the diffusion coefficient, decomposing reaction rate, concentration within the reactor, and concentration distributing profiling of MTS within micro pore were accounted, respectively. The results indicate that, increasing the ratio of diffusion coefficient to decomposition rate constant of precursor MTS is propitious to decrease the densification gradient of parts, and decreasing the aspect ratio (L/D) of micro pore is favorable to make the concentration uniform within pores.展开更多
Large area diamond films were fabricated on copper substrates by a multi-step process comprised of electroplating Cu-diamond composite layer on Cu substrate, plating a Cu layer to fix the protruding diamond particles,...Large area diamond films were fabricated on copper substrates by a multi-step process comprised of electroplating Cu-diamond composite layer on Cu substrate, plating a Cu layer to fix the protruding diamond particles, and depositing continuous diamond film on composite interlayer by hot-filament chemical vapor deposition （HFCVD）. The interface characteristics, internal stress and adhesion strength were investigated by scanning electron microscopy, Raman analysis and indentation test. The results show that the continuous film without cracks is successfully obtained. The microstructure of the film is a mixture of large cubo-octahedron grains grown from homo-epitaxial growth and small grains with （111） apparent facets grown from lateral second nuclei. The improved adhesion between diamond film and substrate results from the deep anchoring of the diamond particles in the Cu matrix and the low residual stress in the film.展开更多
Zinc alloy coating attracted much attention due to its high anti-corrosive properties.Particularly,zinc alloy coatings containing magnesium was considered a promising metallic alloy due to a remarkable improvement of ...Zinc alloy coating attracted much attention due to its high anti-corrosive properties.Particularly,zinc alloy coatings containing magnesium was considered a promising metallic alloy due to a remarkable improvement of corrosion resistance.The proper magnesium content for Zn-Mg alloy coatings was studied.The samples were prepared using thermal evaporation method.The influence of Zn-Mg alloy coating on corrosion resistance was evaluated using immersion test,potentiodynamic test,and galvanic test in 3% NaCl solution at room temperature.The results show that the corrosion resistance of Zn-Mg alloy coatings is strongly dependent on magnesium content.Corrosion potential decreases with increasing magnesium content,whereas current density increases up to 15% magnesium content,and passivity region was found only in Zn-Mg coatings.展开更多
文摘In order to improve the uniformity of both the concentration of gaseous reagent and the deposition of matrix within micro pores during the chemical vapor infiltration (CVI) process, a calculation modeling of gas phase diffusion transport within micro pores was established. Taken CH 3SiCl 3 as precursor for depositing SiC as example, the diffusion coefficient, decomposing reaction rate, concentration within the reactor, and concentration distributing profiling of MTS within micro pore were accounted, respectively. The results indicate that, increasing the ratio of diffusion coefficient to decomposition rate constant of precursor MTS is propitious to decrease the densification gradient of parts, and decreasing the aspect ratio (L/D) of micro pore is favorable to make the concentration uniform within pores.
基金Projects(51071070,51271079)supported by the National Natural Science Foundation of ChinaProject(NCET-11-0156)supported by New Century Excellent Talents in University,China
文摘Large area diamond films were fabricated on copper substrates by a multi-step process comprised of electroplating Cu-diamond composite layer on Cu substrate, plating a Cu layer to fix the protruding diamond particles, and depositing continuous diamond film on composite interlayer by hot-filament chemical vapor deposition （HFCVD）. The interface characteristics, internal stress and adhesion strength were investigated by scanning electron microscopy, Raman analysis and indentation test. The results show that the continuous film without cracks is successfully obtained. The microstructure of the film is a mixture of large cubo-octahedron grains grown from homo-epitaxial growth and small grains with （111） apparent facets grown from lateral second nuclei. The improved adhesion between diamond film and substrate results from the deep anchoring of the diamond particles in the Cu matrix and the low residual stress in the film.
基金supported by the Smart Coating Steel Development Center,World Premier Materials (WPM) Program of the Ministry of Knowledge Economy of Korea and Korea Maritime University
文摘Zinc alloy coating attracted much attention due to its high anti-corrosive properties.Particularly,zinc alloy coatings containing magnesium was considered a promising metallic alloy due to a remarkable improvement of corrosion resistance.The proper magnesium content for Zn-Mg alloy coatings was studied.The samples were prepared using thermal evaporation method.The influence of Zn-Mg alloy coating on corrosion resistance was evaluated using immersion test,potentiodynamic test,and galvanic test in 3% NaCl solution at room temperature.The results show that the corrosion resistance of Zn-Mg alloy coatings is strongly dependent on magnesium content.Corrosion potential decreases with increasing magnesium content,whereas current density increases up to 15% magnesium content,and passivity region was found only in Zn-Mg coatings.
