Mullite ceramic whisker composite article exhibiting high-temperature strength

Claim 1

A process for the manufacture of a fracture-toughened mullite ceramic article which comprises the steps of: (a) providing a flowable slurry comprising free oxides dispersed in a first liquid vehicle, the free oxides consisting essentially of a mixture of SiO 2 , Al 2 O 3 and ZrO 2 wherein the mole ratio Al 2 O 3 :SiO 2 is about 3:2 and the weight fraction of ZrO 2 is in the range of about 15-40% by weight; (b) providing a flowable whisker dispersion comprising SiC whiskers dispersed in a second liquid vehicle; (c) combining the flowable slurry with the whisker dispersion to provide a mixed dispersion, the combination being in a proportion such that the SiC whiskers comprise 10-50% by weight of the solids present in the mixed dispersion; (d) removing the liquid vehicle from the mixed dispersion to provide a solid mixture; and (e) reacting the free SiO 2 with the free Al 2 O 3 in the solid mixture while consolidating the mixture to a unitary ceramic article, said reacting and consolidating comprising heating to a temperature at least sufficient to obtain conversion of the free SiO 2 and Al 2 O 3 in the solid mixture to mullite crystals; thus to provide a fracture-toughened mullite ceramic article having a room temperature modulus of rupture strength in excess of 70,000 psi.