Abstract: This invention is a method of manufacturing oxide porous bodies and components of alumina and magnesia, using alumina and magnesia powders as raw materials, wherein (1) cold isostatic pressure (CIP) of at least 100 MPa is applied to the materials to introduce a plastic deformation with lattice disorder in the surface vicinity without external changes in the particles, (2) by sintering (calcining) the powders with the above described plastic deformation, the microscopic plastic deformation is removed and, at the same time, formation and growth of necks between grains is induced, (3) from the above described steps (1) and (2), a highly porous body with a structure constituted by a three dimensional network of grains connected through the necks is produced.

Abstract: The present invention relates to a method for producing a porous silicon nitride sintered body having high strength and low thermal conductivity, which comprises of adding more than 10 volume % of rodlike beta-silicon nitride single crystals with a larger mean diameter than that of a silicon nitride raw powder into a mixture comprising the silicon nitride raw powder and a sintering additive, preparing a formed body with rodlike beta-silicon nitride single crystals oriented parallel to the casting plane according to a forming technique such as sheet casting and extrusion forming, sintering said formed body to develop elongated silicon nitride grains from the added rodlike beta-silicon nitride single crystals as nuclei and obtain the sintered body with the elongated grains being dispersed in a complicated state.

Abstract: An object of the present invention is to provide a high-porosity, high-strength porous silicon nitride having great tolerance with respect to strain and stress, and a method for producing the same, and the present invention relates to a high-porosity, high-strength porous silicon nitride having great tolerance with respect to strain and stress, characterized in that rodlike grains of silicon nitride with a minor diameter of 0.5 to 10 .mu.m and an aspect ratio of 10 to 100 are oriented in a single direction, and the rest of the structure other than the rodlike grains consists solely of pores with a porosity of 5 to 30%, and further the above-mentioned porous silicon nitride is produced by mixing rodlike particles of silicon nitride with a minor diameter of 0.5 to 10 .mu.

Abstract: The present invention relates to a silicon nitride sintered body having a remarkably increased strain-to-fracture, a low elasticity and high strength, characterized by consisting of a layered structure of alternating porous silicon nitride layers 1 to 1000 .mu.m thick with a porosity of 5 to 70 volume % and dense silicon nitride layers 1 to 1000 .mu.m thick with a porosity of less than 5 volume %, being layered as materials with optional tiers. In addition, this invention relates to a method for producing the silicon nitride sintered body as described above, which comprises of forming dense layers and porous layers by sheet casting or extrusion forming so as to prepare the layers to be capable of 1 to 1000 .mu.m thick after sintering, stacking them to obtain layered materials with optional tiers and sintering them at 1600.degree. to 2100 .degree. C. under a nitrogen atmosphere.

Abstract: A method for the production of a high-strength high-toughness silicon nitride sinter includes the steps of mixing a silicon nitride powder with a sintering additive, adding to the resultant mixture as seed particles 0.1 to 10% by volume, based on the amount of the mixture, of elongated single crystal .beta.-silicon nitride particles having a larger minor diameter than the average particle diameter of the silicon nitride powder and having an aspect ratio of at least 2, forming the resultant mixture so as to orient the elongated single crystal .beta.-silicon nitride particles as seed particles in a specific direction, and heating the green body to density it and simultaneously induce epitaxial growth of single crystal .beta.-silicon nitride particles, and a high-strength, high-toughness silicon nitride sinter obtained by the method.

Abstract: A method for the production of a high-strength high-toughness silicon nitride sinter includes the steps of mixing a silicon nitride powder with a sintering additive, adding to the resultant mixture as seed particles 0.1 to 10% by volume, based on the amount of the mixture, of elongated single crystal .beta.-silicon nitride particles having a larger minor diameter than the average particle diameter of the silicon nitride powder and having an aspect ratio of at least 2, forming the resultant mixture so as to orient the elongated single crystal .beta.-silicon nitride particles as seed particles in a specific direction, and heating the green body to density it and simultaneously induce epitaxial growth of single crystal .beta.-silicon nitride particles, and a high-strength, high-toughness silicon nitride sinter obtained by the method.