Abstract: A method is disclosed for making an aging-resistant, partially stabilized zirconia ceramic, which method is not totally dependent upon grain size control, can function to eliminate substantially any monoclinic phase that results from machining such zirconia article, and employs a novel heat treatment to do so.The method particularly comprises: (a) sintering such article at a temperature and for a period of time to produce a densified product having little or no monoclinic crystal phase when cooled to room temperature (i.e. 2550.degree.-2650.degree. F. for 0.5-4 hours); (b) subjecting the cooled sintered article a machining operation that results in the formation of monoclinic crystal phase on the surface of the part; and (c) heating said treated article to the temperature range of 1800.degree.-1950.degree. F. (982.degree.-1066.degree. C.) to re-transform monoclinic crystal structure to tetragonal crystal.

Abstract: A method of joining silicon nitride based ceramic bodies is disclosed. At least one interfacing surface of shaped bodies (one or both of which may be hot-pressed or reaction-sintered) receives a layer of metallic aluminum based material. The bodies with the metallic aluminum based material therebetween are subjected to heating at 1400.degree.1900.degree. C. for a period typically 0.5-2 hours in a nitriding atmosphere to effect a chemical bond consisting of a conversion of the interfacing ceramic to a Si--Al--O--N system.

Abstract: A method of making improved SIALON ceramics without the need for hot pressing, is disclosed. A homogeneous slip is prepared from Si.sub.3 N.sub.4, Al.sub.2 O.sub.3 and Y.sub.2 O.sub.3 in the presence of a suspension agent; Y.sub.2 O.sub.3 being present in at least 1% by weight (preferably between 1-25%) and Al.sub.2 O.sub.3 being present in the range 16-40% by weight (preferably 16-18%). The slip is cast and dehydrated. The cast shape is reaction sintered at about 1550.degree.-1700.degree. C (preferably 1600.degree. C) for no less than 3 hours (preferably between 3-12 hours).