Abstract: A ceramic composite material consisting of two or more crystal phases of different components, each crystal phase having a non-regular shape, said crystal phases having three dimensional continuous structures intertwined with each other, at least one crystal phase thereof being a single crystal. Further, by removing at least one crystal phase from this ceramic composite material, there is provided a porous ceramic material consisting of at least one crystal phase and pores, said crystal phase and pores having non-regular shapes and being three dimensionally continuous and intertwined with each other.

Abstract: A novel ceramic composite of a solidified body consisting of at least two crystal phases of oxides selected from metal oxides and complex metal oxides, except for the Al.sub.2 O.sub.3 /Y.sub.3 Al.sub.5 O.sub.12 combination.

Abstract: A ceramic composite material consisting of single crystal .alpha.-Al.sub.2 O.sub.3 and single crystal Y.sub.3 Al.sub.5 O.sub.12 is provided. This composite material has high mechanical strength and creep behavior particularly at high temperatures.

Abstract: A novel ceramic composite material consisting of single crystal .alpha.-Al.sub.2 O.sub.3 and polycrystal Y.sub.3 Al.sub.5 O.sub.12 and a ceramic composite material consisting of polycrystal .alpha.-Al.sub.2 O.sub.3 and polycrystal Y.sub.3 Al.sub.5 O.sub.12, each having a high mechanical strength and creep behavior particularly at high temperature are provided.

Abstract: A SiAlON-based sintered body having a high mechanical strength and fracture toughness, as well as an excellent oxidation resistance, is provided. The SiAlON-based sintered body comprises 5 to 50% by weight of a first crystal phase of RE.alpha.-SiAlON represented by RE.sub.x (Si, Al).sub.12 (O, N).sub.16, where RE stands for at least one modifying rare earth element selected from the group consisting of Ho, Er, Tm, Yb and Lu and x has a value of 0<x.ltoreq.2, 30 to 90% by weight of a second crystal phase of .beta.-SiAlON represented by Si.sub.6-z Al.sub.z O.sub.z N.sub.8-z (0<z.ltoreq.4.2), and 1 to 50% by weight of a third crystal phase containing at least one rare earth element RE selected from the group consisting of Ho, Er, Tm, Yb and Lu, optionally together with 1 to 20% by weight of a crystal phase of .alpha.-silicon nitride.

Abstract: A fine particulate .alpha.-Sialon powder with a narrow particle size distribution, thus having an excellent sinterability, can be produced by using as the starting materials (a) amorphous silicon nitride, (b) metallic aluminum or aluminum nitride, and (c) an oxide of a metal which can be incorporated in the interstices of .alpha.-Sialon lattice or a metal compound capable of forming such a metal oxide upon thermal decomposition, and optionally, (d) an oxygen-containing compound of alumina or silicon, followed by heat treatment of the resultant mixture.

Abstract: Uniform sialon powders having a sharp particle size distribution are obtained by mixing (i) amorphous silicon nitride powders, (ii) an oxygen-containing compound of silicon or/and aluminum, and (iii) aluminum metal, aluminum nitride and/or silicon, and then heating the resultant mixture at 1300.degree. to 1800.degree. C. in an atmosphere containing nitrogen.

Abstract: A lower alcohol, especially methanol, or dimethyl ether is subjected to pyrolysis conditions in the presence of a specific catalyst to obtain lower olefins. The catalyst is comprised of a smectite, such as a montmorillonite clay, having superimposed aluminosilicate layers and zirconium oxide intercalated between the structural, aluminosilicate layers.