Fabrication of net shape reaction bonded oxide ceramics

Zero-shrinkage mullite-zirconia ceramics with Y2O3Y2O3 and MgO as sintering additives and siloxanes as low loss binders were fabricated by direct oxidation of ZrAl3/ZrSi2ZrAl3/ZrSi2 and ZrAl3/Zr2Si/3Y-ZrO2ZrAl3/Zr2Si/3Y-ZrO2 powder compacts. Depending on the starting composition the sintered ceramics contain either ZrO2 and mullite or ZrO2, alumina and mullite as crystalline phases. The reaction bonding process was studied by thermogravimetry, dilatometry and quantitative XRD-phase analysis. Due to their dense microstructure reaction-bonded 55/45 (vol.%) ZrO2/mullite composites sintered at 1450° C exhibit biaxial flexure strengths up to 630 MPa. Reaction bonded ZrO2/Al2O3ZrO2/Al2O3 /mullite composites (30/25/45 vol.%) show biaxial flexure strengths of 635 MPa.