In Situ Synthesis of Oxide Ceramic Matrix Composites (CMC's) Based on Powder Blends of Fly Ash with Magnesium and Aluminum

摘要

The process of reactive in-situ processing of debse ceramic matrix composites from fly ash blended with Mg-Al or MoO_3-Al powders via self-propagating high-temperature synthesis (SHS) is discussed. Densification was achieved using the reactive forging (RF) technique in which the reactants were forged during the exothermic reaction. The temperatures of processing or preheating (< 800 deg C) were significantly lower than those prevailing in the current methods used for the processing of ceramic matrix composites. Close to full conversion of the reagents into products was achieved during RF, and a moderate external pressure of < = 100 MPa applied in order to densify the composites. The RF products of fly ash-Mg-Al and fly ash-MoO_3-Al blends had the MgAl_2O_4 (Spinel) or Al_2O_3 matrix, respectively. Rapid cooling aftre combustion resulted in fine materials' microstructure.