High Temperature Liquid and Glass Precursors for Oxyphosphate Ceramic Composites

Abstract

Abstract : The overall objective of this project has been explore the structure, dynamics and physical chemistry of rare earth aluminophosphosilicates (REAPS) glasses for the purpose of designing low temperature synthetic routes for fabricating high temperature, high fracture toughness ceramic-matrix-composites. The concept is based on a glass-ceramic approach that combines the densification of glass powders via viscous sintering followed by independent crystallization anneals. The challenge with REAPS glasses is to balance the design criteria for effective synthesis with the criteria of the composite applications. One objective was to find appropriate compositions that allowed sufficient range of temperatures to sinter glass powders above their glass transition temperatures to separately densify glass powders in their supercooled state with the hindrance of premature crystallization. In subsequent step, the densified glasses would be crystallized in a manner to produce microstructures of appropriate utility. The work undertaken has been to evaluate and understand the pertinent physical and chemical properties that are necessary for optimizing the chemistry that best meets both demands. Fortunately, we identified compositions that satisfy both sets of criteria with almost no compromise and the feasibility of the glass-ceramic approach for producing ceramic matrix nanocomposites was proven.