Patent ID: 7368406

Claim:
A process to make a ceramic body comprising the steps of: providing a starting powder mixture comprising ceramic whiskers, a ceramic additive powder other than aluminum oxynitride, and aluminum oxynitride powder that contains less than or equal to about 0.1 weight percent aluminum nitride wherein the aluminum oxynitride powder is made by a process comprising the steps of: forming a powder mixture by mixing alumina powder and aluminum nitride powder according to the following formula: ((4−x)/3) alumina and x aluminum nitride wherein x is in mole percent and ranges between about 0.31 and about 0.61; adding between about 0.1 mole percent and about 1.0 mole percent of pure aluminum powder to the powder mixture; and reacting the powder mixture containing aluminum at a temperature between about 1600° C. and about 1900° C. for a duration between about 2 hours and about 24 hours in a flowing nitrogen atmosphere so as to form aluminum oxynitride; consolidating the starting powder mixture into the ceramic body, and wherein the ceramic body having a Vicker's Hardness Number (VHN) determined per ASTM E384-99e1 being at least about 15.00, and a fracture toughness (K IC ) per Evans and Charles being at least about 5.0 MPa·m 1/2 .