Preparation and properties of C/SiC/ZrO2 porous composites by hot isostatic pressing the pyrolyzed preforms

Three phase mixture of C/SiC/ZrO2 porous composites were prepared from commercially available phenolic resin, Si and ZrO2 powders. In the first step, mixed powders were pyrolyzed at 850 °C in vacuum to obtain a carbonized microporous material and then hot isostatically pressed at 1200, 1300 and 1350 °C for 10 min in an argon pressure of 50 MPa to prepare C/SiC/ZrO2 porous composites, in second step. The hot isostatic pressing led to the increase in density from 3.28 to 3.48 g/cm3 and reduction in porosity (from 32 to 20%) of the composites. X-ray diffraction analyses revealed the existence of β-SiC and carbon might be amorphous in the composites. According to the results of scanning electron microscopy, the crystal growth of β-SiC with facets was observed at 1350 °C. In addition, the energy dispersive spectroscopy showed that carbon/silicon atomic ratio was 1:1 in the crystals. X-ray photoelectron spectroscopy of the composites suggested that evolved gaseous molecules, due to the decomposition of phenolic resin, reacted with molecules containing Si to form β-SiC. The formation and growth of β-SiC in addition to the densification of matrix by hot isostatic pressing led to the increase in hardness (max.: 13.99 GPa) at higher temperatures.