A Si-Al-lr oxidation resistant coating was prepared for SiC coated carbon/carbon composites by slurry dipping. The phase composition, microstructure and oxidation resistance of the as-prepared Si-Al-lr coating were st...A Si-Al-lr oxidation resistant coating was prepared for SiC coated carbon/carbon composites by slurry dipping. The phase composition, microstructure and oxidation resistance of the as-prepared Si-Al-lr coating were studied by XRD （X-ray diffraction）, SEM （scanning electron microscopy）, and isothermal oxidation test at 1773 K in air, respectively. The surface of the as-prepared Si-Al-lr coating was dense and the thickness was approximately 100 um. Its anti-oxidation property was superior to that of the inner SiC coating. The weight loss of SiC/Si- Al-lr coated carbon/carbon composites was less than 5 wt. pct after oxidation at 1773 K in air for 79 h. The local oxidation defects in the coating may result in the failure of the SiC/Si-Al-Ir coating.展开更多
Different compositions of yttrium silicates coatings were deposited on SiC-C/C by plasma spraying and an outer borosilicate glass was applied on the yttrium silicates coatings surfaces. The structure of the multi-laye...Different compositions of yttrium silicates coatings were deposited on SiC-C/C by plasma spraying and an outer borosilicate glass was applied on the yttrium silicates coatings surfaces. The structure of the multi-layer coatings was characterized by XRD and SEM analyses. High temperature oxidation behavior of the multi-layer coatings coated C/C composites was investigated. Results show that SiC/2SiO2 Y2O3/1.5SiO2 Y203/ SiO2 Y2O3/glass multi-layer coating has better high temperature oxidation resistance, protecting carbon/ carbon composites from oxidation at 1 773 K in air for 164 h with the weight loss of 1.65%. The oxidation weight loss of the coated C/C with time accorded with parabolic rule in the temperature range 1 573 K-1 873 K; and the corresponding oxidation activation energy of the coated carbon/carbon composites is 132.2 kJ/mol.展开更多
A new way to prepare SiC whiskers through the induction of carbon fiber was suggested. With the processing steps of opening furnace firstly and then shutting it, rice hall, as the only raw material, was carbonified to...A new way to prepare SiC whiskers through the induction of carbon fiber was suggested. With the processing steps of opening furnace firstly and then shutting it, rice hall, as the only raw material, was carbonified to get excess quantity of Si in rice hull. After a certain catalyzer was added, SiC whiskers were prepared by means of the induction of carbon fiber. The component and morphology of the whisker were analyzed by XRD, SEM and TEM. The results reveal that the diameters of the whiskers range in 0.5-2μm and their lengths in 100-500μm. The whiskers are straightβ-SiC crystals with smooth surface. The whisker is homogeneous and its productivity is 100%. Two kinds of formation mechanisms, both VLS mechanism and vapor formation mechanism, are involved during the growth of the whiskers. But the vapor formation mechanism relatively plays a key role.展开更多
基金supported by the National "973"Project under grant No. 2006CB600908
文摘A Si-Al-lr oxidation resistant coating was prepared for SiC coated carbon/carbon composites by slurry dipping. The phase composition, microstructure and oxidation resistance of the as-prepared Si-Al-lr coating were studied by XRD （X-ray diffraction）, SEM （scanning electron microscopy）, and isothermal oxidation test at 1773 K in air, respectively. The surface of the as-prepared Si-Al-lr coating was dense and the thickness was approximately 100 um. Its anti-oxidation property was superior to that of the inner SiC coating. The weight loss of SiC/Si- Al-lr coated carbon/carbon composites was less than 5 wt. pct after oxidation at 1773 K in air for 79 h. The local oxidation defects in the coating may result in the failure of the SiC/Si-Al-Ir coating.
基金Supported by National Natural Science Foundation of China(No.50772063)the Program for New Century Excellent Talents in University(No.NCET-06-0893)
文摘Different compositions of yttrium silicates coatings were deposited on SiC-C/C by plasma spraying and an outer borosilicate glass was applied on the yttrium silicates coatings surfaces. The structure of the multi-layer coatings was characterized by XRD and SEM analyses. High temperature oxidation behavior of the multi-layer coatings coated C/C composites was investigated. Results show that SiC/2SiO2 Y2O3/1.5SiO2 Y203/ SiO2 Y2O3/glass multi-layer coating has better high temperature oxidation resistance, protecting carbon/ carbon composites from oxidation at 1 773 K in air for 164 h with the weight loss of 1.65%. The oxidation weight loss of the coated C/C with time accorded with parabolic rule in the temperature range 1 573 K-1 873 K; and the corresponding oxidation activation energy of the coated carbon/carbon composites is 132.2 kJ/mol.
基金Project(50225210) supported by the National Natural Science Foundation of China for Distinguished Young Scholars Project(03H53044) supported by the Aeronautic Science of China
文摘A new way to prepare SiC whiskers through the induction of carbon fiber was suggested. With the processing steps of opening furnace firstly and then shutting it, rice hall, as the only raw material, was carbonified to get excess quantity of Si in rice hull. After a certain catalyzer was added, SiC whiskers were prepared by means of the induction of carbon fiber. The component and morphology of the whisker were analyzed by XRD, SEM and TEM. The results reveal that the diameters of the whiskers range in 0.5-2μm and their lengths in 100-500μm. The whiskers are straightβ-SiC crystals with smooth surface. The whisker is homogeneous and its productivity is 100%. Two kinds of formation mechanisms, both VLS mechanism and vapor formation mechanism, are involved during the growth of the whiskers. But the vapor formation mechanism relatively plays a key role.
