Abstract: Oxynitride glass whose composition is represented by Al—Si—O—N or M—Al—Si—O—N (where M denotes Ca, Mg, or rare earth element), wherein the content of O and N as non-metallic components is in the range of 0 eq %<N≦30 eq %, with O+N=100 eq %, the content of M, Al, and Si as metallic components is in the range of 20 eq %≦Al≦30 eq % and 70 eq %≦Si≦80 eq %, respectively, with Al+Si=100 eq % (if M does not exist) and the content of M, Al, and Si as metallic components is within the hatched area in the composition diagrams shown in FIGS. 1 to 3, if M is Ca, Mg, or rare earth metal, or within the hatched area in the composition diagrams shown in FIGS. 4 to 8, if the content of N is in the range of 5 eq %≦N≦25 eq %. This glass is superior in specific rigidity and fabricability. It contains nitrogen in a controlled amount so that it has improved specific rigidity without its specific gravity increasing.

Abstract: A method of producing a disk having a radius of r and a thickness of 2h from an oxynitride glass by pressing, said method being characterized in that the pressing load (F), the pressing temperature (T), and the pressing time (t) are defined by the expression below. 1 1900 ≥ T ≥ 100 × log 10 ⁡ ( 0.

Abstract: A mixed powder containing: 5-30 wt % of SiC whiskers; 3-30 wt % of a sintering auxiliary agent composed of one kind or more of oxides of Mg, Si, Ca, Ti, Zr, Cr, Ni, Y and rare earth elements; and an Al.sub.2 O.sub.3 powder as a base material; or further containing 0.5-40 wt % of one kind or more of compounds composed of one kind or more of transient elements in the groups IVa, Va, and VIa of the periodic table and one kind or more of C, N and B, are compacted and subjected to pressureless-sintering in a nitrogen containing inert gas atmosphere at a temperature between 1500.degree. and 1900.degree. C. With this method, the SiC whiskers containing Al.sub.2 O.sub.3 based ceramic material, which is densified and has a sufficient strength and toughness, can be formed in a complex shape and a large size.

Abstract: In Al.sub.2 O.sub.3 composites used for machining tools for difficult-cutting steels, etc., strength and toughness are increased by dispersing a Ti compound with an average grain size of not greater than 0.1 .mu.m into Al.sub.2 O.sub.3 particles with the average grain size of not greater than 1 .mu.m, and SiC whiskers are uniformly dispersed between each of Al.sub.2 O.sub.3 particles to form a nanocomposite structure.For the above-mentioned purpose, SiC whiskers containing 0.3 to 1.5% by weight of oxygen, dissolved uniformly in a solvent, are mixed with a starting Al.sub.2 O.sub.3 series powder containing Ti compounds to form a uniform mixture, which is then molded and sintered.