Abstract: This invention describes the infiltration methods used to incorporate ceramic additives in carbon/carbon brake disc preforms. Aqueous vacuum infiltration techniques were employed. Both methods were effective in achieving homogeneous dispersion of ceramic additives throughout brake disc thickness. Heat treatment processes were developed to convert oxide additives to more refractory phases. Both temperature and N.sub.2 overpressure were precisely controlled during conversion. By using the additives, infiltration routes, and heat treatment schedules, brake disc friction material performance properties such as friction coefficient, friction coefficient stability, and brake disc wear rate are improved. The disclosed carbon/carbon brake discs can be used in aerospace, automotive and other friction material applications.

Abstract: A ceramic body having a surface region containing tetragonal zirconia is sintered to at least 95% theoretical density at a temperature below about 1550 .degree. C. The surface region is then heat treated to reverse local stresses therein. Low temperature degradation in tetragonal zirconia, and materials containing tetragonal zirconia, is significantly inhibited. The heat treated ceramic is especially suited for use in structural components such as valves, engine housings, pistons (chambers) and the like which, during operation, are frequently exposed to temperatures ranging from room temperature to 500.degree. C. for prolonged periods of time.

Abstract: A ceramic component is manufactured rapidly using a mold made directly from a solid freeform manufacturing process. Solid freeform fabrication, or rapid prototyping, procedures are used to generate molds of materials that are soluble or otherwise fugitive. A gel casting suspension containing ceramic and emulsifying agents is poured into the cavity of the mold and caused to set. The mold is then removed by dissolution or heat treatment, leaving intact the gelcast part. Conventional procedures are then utilized to densify the gelcast component to the required final component. Time consuming and expensive machine tooling procedures are virtually eliminated. Ceramic components are generated rapidly in a cost effective manner.

Abstract: Blades for use in combusion turbine engines are formed from a single crystal aluminum garnet body--desirably a rare earth aluminum garnet body--having an epitaxial surface layer of a second aluminum garnet having a lattice constant larger than that of the body garnet so as to provide a compressive strain, to thereby strengthen the blade.

Abstract: Blades for use in combusion turbine engine are formed from a single crystal garnet body--suitably an aluminum garnet, desirably a rare earth aluminum garnet--having an epitaxial surface layer of a second garnet having a lattice constant larger than that of the body garnet so as a compressive strain, to thereby strengthen the blade.

Abstract: Reinforcement fibers are formed from a single crystal garnet body--suitably an aluminum garnet, desirably a rare earth aluminum garnet--having an epitaxial surface layer of a second garnet having a lattice constant larger than that of the body garnet so as to provide a compressive strain, to thereby strengthen the fiber.

Abstract: A ceramic body has a surface region that contains tetragonal zirconia. The body is partially stabilized with yttria and, optionally, ceria. Substantially the entire surface region is composed of recrystallized tetragonal strain free grains of yttrium oxide zirconium oxide. The content of yttrium in the surface region is substantially the same as the average content of yttrium in the ceramic body, and the surface region is covered with a thin layer of stable tetragonal grains.