Influence of ZrO2 and SiC on physico-mechanical, microstructure and electrical properties of cordierite ceramics based on utilizing talc/oil shale waste

Abstract

The present paper describes the in situ fabrication of fired cordierite-based ceramic matrix composites containing dispersed particles of ZrO₂ or SiC. Mixing Oil shale and talc with additions of monoclinic ZrO₂ or SiC up to 15 wt% was performed and fired at 1200 °C. However, the initial mix composition of oil shale and talc was calculated stoichiometric to prepare cordierite ceramics, and the prepared mixtures were subjected to firing at 1150, 1200, and 1250 °C to optimize the cordierite formation. Phase compositions, microstructure, bulk density, apparent porosity, hardness, fracture toughness, electric, and dielectric properties were carefully investigated. The results showed that the optimum temperature for firing cordierite before the addition of SiC or ZrO₂ is 1200 °C. The bulk density increased to 2.2 g/cm³ and apparent porosity decreased to about 9 % after the addition of 15 wt% of ZrO₂. The increase of SiC led to an increase in apparent porosity and a decrease in bulk density. The maximum bulk density reached 2 g/cm³ and the minimum apparent porosity dropped to 26 % after the addition of 10 wt% of SiC Vickers hardness and fracture toughness of the cordierite-ZrO₂ or SiC samples increased with increasing percentage of ZrO₂ or SiC compared to pure cordierite samples. The maximum hardness value for ZrO₂-containing samples is 7.8 GPa, while it reached 8.2 GPa for SiC-containing samples. Dielectric and electric properties are enhanced by the addition of ZrO₂, which reversed is in the case of SiC addition. Thus this work succeeded in enhancing the mechanical and electrical properties of cordierite after the addition of ZrO or SiC for their ceramic filed applications.