To protect carbon materials from oxidation,SiC coatings were prepared on carbon/carbon(C/C)composites and graphite by chemical vapor reaction.SEM and XRD analyses show that the coatings obtained are composed of SiC gr...To protect carbon materials from oxidation,SiC coatings were prepared on carbon/carbon(C/C)composites and graphite by chemical vapor reaction.SEM and XRD analyses show that the coatings obtained are composed of SiC grains and micro-crystals. The influence of different carbon substrates on oxidation behavior of coated samples was investigated,and then their oxidation mechanisms were studied.Oxidation test shows that the SiC coated graphite has a better oxidation resistance than SiC coated C/C composites at high temperatures(1 623 K and 1 823 K).In the oxidation process,the oxidation curves of SiC coated C/C composites are linear,while those of SiC coated graphite follow a quasi-parabolic manner.The oxidation mechanism of the former is controlled by chemical reaction while the latter is controlled by oxygen diffusion based on the experimental results.The variation of oxidation behavior and mechanism of SiC coatings on two kinds of carbon substrates are primarily contributed to their structure differences.展开更多
研究了复合材料表面 CVD Si C涂层的制备工艺 ,并对涂层的表面致密化性能进行分析。在不同的工艺条件下制备 Si C涂层 ,探讨了温度、载气流速、时间等因素对涂层的影响。利用扫描电镜和 X-射线衍射仪 ,对涂层晶型进行分析 ,讨论不同条件...研究了复合材料表面 CVD Si C涂层的制备工艺 ,并对涂层的表面致密化性能进行分析。在不同的工艺条件下制备 Si C涂层 ,探讨了温度、载气流速、时间等因素对涂层的影响。利用扫描电镜和 X-射线衍射仪 ,对涂层晶型进行分析 ,讨论不同条件下 Si C的结晶形态 ,从而得出制备致密涂层的较好工艺。展开更多
To protect carbon/carbon (C/C) composites from oxidation, a SiC coating modified with SiO2 was prepared by a complex technology. The inner SiC coating with thickness varying from 150 to 300 μm was initially coated by...To protect carbon/carbon (C/C) composites from oxidation, a SiC coating modified with SiO2 was prepared by a complex technology. The inner SiC coating with thickness varying from 150 to 300 μm was initially coated by chemical vapor reaction (CVR): a simple and cheap technique to prepare the SiC coating via siliconizing the substrate that was exposed to the mixed vapor (Si and SiO2) at high temperatures (1 923?2 273 K). Then the as-prepared coating was processed by a dipping and drying procedure with tetraethoxysilane as source materials to form SiO2 to fill the cracks and holes. Oxidation tests show that, after oxidation in air at 1 623 K for 10 h and thermal cycling between 1 623 K and room temperature 5 times, the mass loss of the CVR coated sample is up to 18.21%, while the sample coated with modified coating is only 5.96%, exhibiting an obvious improvement of oxidation and thermal shock resistance of the coating. The mass loss of the modified sample is mainly contributed to the reaction of C/C substrate with oxygen diffusing through the penetrating cracks formed in thermal shock tests.展开更多
基金Project(2006CB600901)supported by the National Basic Research Program of ChinaProjects(50772134,50802115)supported by the National Natural Science Foundation of China
文摘To protect carbon materials from oxidation,SiC coatings were prepared on carbon/carbon(C/C)composites and graphite by chemical vapor reaction.SEM and XRD analyses show that the coatings obtained are composed of SiC grains and micro-crystals. The influence of different carbon substrates on oxidation behavior of coated samples was investigated,and then their oxidation mechanisms were studied.Oxidation test shows that the SiC coated graphite has a better oxidation resistance than SiC coated C/C composites at high temperatures(1 623 K and 1 823 K).In the oxidation process,the oxidation curves of SiC coated C/C composites are linear,while those of SiC coated graphite follow a quasi-parabolic manner.The oxidation mechanism of the former is controlled by chemical reaction while the latter is controlled by oxygen diffusion based on the experimental results.The variation of oxidation behavior and mechanism of SiC coatings on two kinds of carbon substrates are primarily contributed to their structure differences.
文摘研究了复合材料表面 CVD Si C涂层的制备工艺 ,并对涂层的表面致密化性能进行分析。在不同的工艺条件下制备 Si C涂层 ,探讨了温度、载气流速、时间等因素对涂层的影响。利用扫描电镜和 X-射线衍射仪 ,对涂层晶型进行分析 ,讨论不同条件下 Si C的结晶形态 ,从而得出制备致密涂层的较好工艺。
基金Project(2006CB600901) supported by the National Basic Research Program of ChinaProject(50802115) supported by the National Natural Science Foundation of China
文摘To protect carbon/carbon (C/C) composites from oxidation, a SiC coating modified with SiO2 was prepared by a complex technology. The inner SiC coating with thickness varying from 150 to 300 μm was initially coated by chemical vapor reaction (CVR): a simple and cheap technique to prepare the SiC coating via siliconizing the substrate that was exposed to the mixed vapor (Si and SiO2) at high temperatures (1 923?2 273 K). Then the as-prepared coating was processed by a dipping and drying procedure with tetraethoxysilane as source materials to form SiO2 to fill the cracks and holes. Oxidation tests show that, after oxidation in air at 1 623 K for 10 h and thermal cycling between 1 623 K and room temperature 5 times, the mass loss of the CVR coated sample is up to 18.21%, while the sample coated with modified coating is only 5.96%, exhibiting an obvious improvement of oxidation and thermal shock resistance of the coating. The mass loss of the modified sample is mainly contributed to the reaction of C/C substrate with oxygen diffusing through the penetrating cracks formed in thermal shock tests.
