Towards Development of New Materials with Improved Thermal Stress Properties

Two methods of using Al2W3O12, a compound with a low-positive coefficient of thermal expansion (CTE), to produce materials with improved thermoelastic properties were studied: formation of polymer/nanopowder composites with reduced CTEs, and production of bulk ceramics with improved thermal shock resistance. Dispersion of Al2W3O12 in HDPE in amounts up to 6 wt.% was found to leave the thermal and elastic properties of the matrix essentially unchanged. The elastic properties of the matrix remained stable following 300 thermal cycles between 10 and 90 ¡C, indicating that thermal stress resulting from CTE mismatch is not sufficiently large to damage the composites. The thermal conductivity of Al2W3O12 in polycrystalline and monocrystalline forms was measured in order to predict its thermal shock resistance. The inherently low thermal conductivity of the monocrystalline material was found to be decreased further when used in polycrystalline form. Spark plasma sintering was found to be a promising method to reduce porosity and therefore increase the strength of bulk Al2W3O12 ceramics.