Geopolymer matrices with improved hydrothermal corrosion resistance for high-temperature applications

Ceramic matrix composites have to overcome two major barriers for applications in aircraft and stationary turbines/engines. One is the unacceptably high processing cost to obtain sufficient mechanical properties and the other is their poor corrosion resistance under hydrothermal oxidizing conditions typical of engines and turbines. Functional geopolymer composites provide possible solutions to the above two problems since they can be formed by technologically simple processing routes and the hydrothermal corrosion resistance can be improved by tailoring material compositions. In this paper geopolymer matrix materials with superior hydrothermal corrosion resistance were processed from the selected geomimetic compositions. The effects of processing parameters, such as particle size, extent of dissolution, and firing temperature on the compressive strength and microstructures were examined and specimens with a compression strength as high as ~99 MPa were fabricated. Hydrothermal test experiments on KOH-derived geopolymer specimens showed that all of potassium-bonded geopolymer specimens have minimal mass change or dimensional change during hydrothermal exposure in spite of the phase change.