Cordierite ceramics containing silicon carbide whisker reinforcement

Claim 1

A whisker-reinforced polycrystalline cordierite ceramic product having: (a) an oxide crystal phase constituting 60-95% by weight of the product and consisting at least predominantly of cordierite; (b) a silicon carbide whisker phase constituting 5-40% by weight of the product, the silicon carbide whiskers having a diameter not exceeding about 3 microns and a length not exceeding about 30 microns; (c) a composition consisting essentially, in weight percent, of about 5-40% SiC, 25-54% SiO 2 , 18-48% Al 2 O 3 , and 5-19% RO, wherein RO consists essentially of MgO and, optionally, one or more oxides in partial substitution for MgO selected in proportions up to the indicated mole fraction of total RO content from the group consisting of: up to 0.98 MnO, up to 0.25 NiO, up to CoO, and up to 0.40 FeO, but not exceeding 0.98 total of MnO+NiO+CoO+FeO; and (d) a modulus of rupture strength in excess of 5,000 psi.

Claim 4

A method of making a whisker-reinforced cordierite ceramic product which comprises the steps of: (a) compounding a ceramic batch comprising silicon carbide whiskers together with source materials for the oxides SiO 2 , Al 2 O 3 , and RO, wherein RO is MgO and, optionally, one or more of MnO, CoO, FeO and NiO, said batch being compounded in proportions effective to yield, after firing, an oxide-carbide composition consisting essentially, in weight percent, of about 5-40% SiC, 25-54% SiO 2 , 18-48% Al 2 O 3 , and 5-19% RO, wherein RO consists essentially of MgO and, optionally, one or more oxides in partial replacement of MgO selected in proportions up to the indicated mole fraction of total RO content from the group consisting of: up to 0.98 MnO, up to 0.25 NiO, up to 0.15 CoO, and up to 0.40 FeO, but not exceeding 0.98 total of MnO+NiO+CoO+FeO: (b) forming the ceramic batch into a preform for the ceramic product; (c) firing the preform to a temperature at least sufficient to initiate conversion of the source materials for oxides into a cordierite crystal phase and maintaining the preform at said temperature for a time sufficient to complete the formation of cordierite, while providing a non-oxidizing firing atmosphere around the preform during exposure thereof to firing temperatures in excess of about 900° C.

Claim 5

A method of making a whisker-reinforced cordierite ceramic product which comprises the steps of: (a) compounding a ceramic batch comprising silicon carbide whiskers together with source materials for the oxides SiO 2 , Al 2 O 3 , and RO, wherein RO is MgO and, optionally, one or more of MnO, CoO, FeO and NiO, said batch being compounded in proportions effective to yield, after firing, an oxide-carbide composition consisting essentially, in weight percent, of about 5-40% SiC, 25-54% SiO 2 , 18-48% Al 2 O 3 , and 5-19% RO, wherein RO consists essentially of MgO and, optionally, one or more oxides in partial replacement of MgO selected in proportions up to the indicated mole fraction of total RO content from the group consisting of: up to 0.98 MnO, up to 0.25 NiO, up to 0.15 CoO, and up to 0.40 FeO, but not exceeding 0.98 total of MnO+NiO+CoO+FeO: (b) forming the ceramic batch into a preform for the ceramic product; (c) firing the preform to a temperature at least sufficient to initiate conversion of the source materials for oxides into a cordierite crystal phase and maintaining the preform at said temperature for a time sufficient to complete the formation of cordierite, while providing a non-oxidizing firing atmosphere around the preform during exposure thereof to firing temperatures in excess of about 900° C.