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Processing of biomorphous SIC ceramics from paper preforms by Chemical Vapor infiltration and reaction (CVI-R) technique

Abstract:

Chemical Vapor Infiltration and Reaction (CVI-R) technique is used to produce biomorphic high porous SiC ceramics derived from paper preforms. The first step is the carbonization of the biological structure to obtain a biocarbon (CB) template. The CB - template is then infiltrated with Si/SiC by CVI technique using methyltrichlorosilane in excess of hydrogen as a precursor. The reaction between carbon and silicon to silicon carbide is completed by a following thermal treatment (1250°C - 1600°C) of the samples as an additional processing step. The resulting SiC ceramics have extreme low density and show excellent mechanical properties, such as high strength and damage tolerance. Such properties make them suitable as catalysts supports for automotive applications, filters, foams or heat and noise insulation materials. The main advantage of the CVI-R technique compared to the other siliconization methods is the possibility to define the properties of the resulting ceramics by varying the infiltration and reaction conditions. Due to the relative mild infiltration temperatures (800°C - 900°C) it is possible to obtain ceramics retaining the exact micro as well as macro structure of the initial carbon preform.