Effect of preforms on the synthesis of micro .BETA.-SiC from phenol resin and silicon

Abstract

The aim of present study is to investigate the effect of preforms on the synthesis of micro β-SiC. For this purpose, preforms were prepared from commercially available phenol resin and silicon powders by pyrolysing at 650°C and 750°C in vacuum. Then, preforms were hot isostatically pressed (HIPed) at 1400°C for 10 min in an argon atmosphere of 50 MPa to synthesize micro β-SiC. X-ray diffraction analyses showed that the formation of β-SiC was enhanced in the specimens prepared by HIPing the preforms pyrolyzed at 750°C, which might be due the more carbonization and the development of porous structure in the range 600-800°C. Scanning electron microscopy observations revealed the formation of micro-crystals (up to 8 μm in size) with facets in the HIPed specimens. In addition, the degree of crystallites in the specimen obtained from the preforms pyrolyzed at 750°C was higher than the preforms pyrolyzed at 650°C. The energy dispersive spectroscopy showed that crystals were of SiC because the atomic ratio of silicon and carbon atoms in the crystals was almost 1 : 1. The density of the specimens obtained by HIPing the preforms pyrolyzed at 750°C was (3.11 g/cm 3 ) more than the specimens obtained by HIPing preforms pyrolyzed at 650°C (2.95 g/cm 3 ). The HIPing process, in addition to densification, led to the formation and growth of β-SiC.