Biomorphic silicon/silicon carbide ceramics from birch powder

Abstract

A novel process has been developed for the fabrication of biomorphic silicon/silicon carbide (Si/SiC) ceramics from birch powder. Fine birch powder was hot-pressed to obtain pre-templates, which were subsequently carbonized to acquire carbon templates, and these were then converted into biomorphic Si/SiC ceramics by liquid silicon infiltration at 1550°C. The prepared ceramics are characterized by homogeneous microstructure, high density, and superior mechanical properties compared to biomorphic Si/SiC ceramics from birch blocks. Their maximum density has been measured as 3.01g/cm3. The microstructure is similar to that of conventional reaction-bonded silicon carbide. The Vicker's hardness, flexural strength, elastic modulus, and fracture toughness of the biomorphic Si/SiC were 19.6±2.2GPa, 388±36MPa, 364±22GPa, and 3.5±0.3MPam1/2, respectively. The outstanding mechanical properties of the biomorphic Si/SiC ceramics are assessed to derive from the improved uniform microstructure of the pre-templates made from birch powder.