United States of America as Represented by the Secretary of the Air Force

Ues, Inc.

Michael K Cinibulk

Triplicane A Parthasarathy

Tai-Il Mah

Kristin A Keller

Randall S Hay

Emmanuel E Boakye

Pavel Mogilevsky

Randal S Hay

A method of manufacturing a coated reinforcing fiber for use in Ceramic Matrix Composites, the method comprising pre-oxidizing a plurality of silicon-based fibers selected from the group consisting of silicon carbide (SiC) fibers, silicon nitride (SiN) fibers, SiCO fibers, SiCN fibers, SiCNO fibers, and SiBCN fibers at between 700 to 1300 degrees Celsius in an oxidizing atmosphere to form a silica surface layer on the plurality of silicon-based fibers, forming a plurality of pre-oxidized fibers; applying a rare earth orthophosphate (REPO) coating to the plurality of pre-oxidized fibers; and heating the plurality of REPOcoated pre-oxidized fibers at about 1000-1500 degrees Celsius in an inert atmosphere to react the REPOwith the silica surface layer to form a rare earth silicate or disilicate. The pre-oxidizing step may be 0.5 hours to about 100 hours. The heating step may be about 5 minutes to about 100 hours.

Oxidation-resistant fiber coatings and related methods

The current invention provides a method to fabricate a crack-free continuous fiber-reinforced ceramic matrix composite by eliminating shrinkage stresses through a unique combination of freeze forming and a non-shrinking matrix composition. Cracks related to drying shrinkage are eliminated through freeze forming and cracks related to sintering shrinkage are eliminated by using a matrix that does not shrink at the given sintering temperature. After sintering, a crack-free ceramic composite is obtained.

Method of making crack-free ceramic matrix composites

A reinforcing material is uniformly dispersed in a yttrium aluminum garnet matrix material for use as a machine tool material specially suited for machining Ti or a Ti alloy. The matrix material and the reinforcing material are present in proportions selected such that the machine tool material is substantially resistant to transfer of impurities to a Ti or Ti alloy by way of either chemical reaction with or diffusion into the Ti or Ti alloy material to be machined. The matrix material preferably comprises Y Al O . The reinforcing material may comprise SiC , TiC, TiN, TiB , or combinations thereof and is preferably present in an amount sufficient to enable electrical discharge machining of the machine tool material. In addition, the machine tool material defines a thermodynamically stable phase at relatively high machining temperatures.

Ceramic matrix composite cutting tool material

A method of making a mechanically stable, fiber having an inclusion of ion-conducting material which includes the steps of coating a single-crystal or polycrystalline .alpha.-alumina fiber with a zirconia or a hexaluminate precursor, optionally heating the coated fiber to dry the coating, when the coating is applied as a suspension or sol, heating the coated fiber to a temperature of about 1000.degree. to 1800.degree. C. to promote the growth of alpha-alumina toothlike extensions in the coating and epitaxial formation of the zirconia or hexaluminate on the sides of the extensions, embedding the fiber in an .alpha.-alumina matrix material, and heating the resulting fiber-matrix composite to react and texture the coating and densify the assembly.

Growing community of inventors

Bellbrook, OH, United States of America

Michael K Cinibulk