Abstract: A process for producing an aluminum nitride sintered body is disclosed, comprising mixing an aluminum nitride powder with (a) a calcium compound and (b) a copper compound, and, if desired, (c) a yttrium compound as sintering aids; molding the mixture; and sintering the molded article in a non-oxidative atmosphere. The resulting sintered body has a high density (3.10 g/cm.sup.3 or higher) and a high thermal conductivity (110 W/mK or higher) even by sintering at a low temperature (1500.degree. to 2000.degree. C.).

Abstract: An aluminum nitride powder obtained by firing and reacting a mixture of alumina and carbon in a nitrogen-containing atmosphere is disclosed, the aluminum nitride powder having an oxygen content of not more than 2.0% by weight, an iron content of not more than 20 ppm, a silicon content of not more than 100 ppm, and a titanium content of not more than 20 ppm and having has a tapped density of at least 1.0 g/cm.sup.3. An aluminum nitride powder containing from 0.01% to 10% by weight of a sintering aid is also disclosed, the aluminum nitride powder having an oleophilic surface and having a tapped density of at least 1.0 g/cm.sup.3. The aluminum nitride powder of the present invention has excellent moldability, has a high tapped density, is less in formation of coagulated particles, and has a sharp particle size distribution.

Abstract: In a furnace which allows a feed powder or granules in a stack of trays on a base plate to be reacted with a reactive gas, the improvement wherein each of the trays has a cutout or an opening providing a passage for the reactive gas or the produced gas both at the top of one side wall and in the bottom wall to the opposite side of the tray, the base plate having an opening through which the reactive gas is introduced or the produced gas is discharged.

Abstract: A method for producing .alpha.-form silicon nitride having a central particle diameter of 0.3 to 1.0 .mu.m (.alpha.-Si.sub.3 N.sub.4) of high-grade and fine powder for its sintered body excellent in heat-stability and mechanical strength which comprises heat-treating at 1,450.degree.-1,550.degree. C., in an atmosphere containing nitrogen, a mixture prepared by adding one of additives:(a) a mixture of at least one of Be, Sr, Ge, Sn, Ti, Hf and compounds thereof with 0.01-1 part by weight of silicon nitride powder having a BET specific surface area of 15 to 50 m.sup.2 /g and consisting substantially of the .alpha.-form crystal, and(b) a mixture of Zr and compounds thereof with 0-1 part by weight of silicon nitride powder having a BET specific surface area of 15 to 50 m.sup.2 /g and consisting substantially of the .alpha.-form crystal,in a total amount of 0.001-0.

Abstract: An improved method for the production of endosseous implants is disclosed. The method includes thermally spraying a hydroxyapatite-containing powder onto the surface of a metallic core material, and treating the resultant product with an aqueous solution which does not substantially dissolve the hydroxyapatite but can dissolve calcium oxide, to thereby dissolve out alkaline components. The endosseous implants of this invention have excellent mechanical properties and excellent affinity to the living body without hematolysis, and hence, are useful for the treatment or recovery of defective or lost bones, joints and tooth roots.

Abstract: When an abrasive having an oleophilic surface intended for use in magnetic recording media, said abrasive being obtained by subjecting an inorganic powder material having a Mohs hardness of 5 or above and an average particle size of 2 .mu.m or below to a wet contact treatment with an aqueous solution or an organic solvent solution containing a dispersing agent having an oleophilic group and drying the treated powder material, is used together with a magnetic powder material in the magnetic recording layer of a magnetic recording medium, the wear of the magnetic head can be prevented and the still characteristics of the recording medium is improved.

Abstract: A method for producing a high-grade fine powder of .alpha.-form silicon nitride (.alpha.-Si.sub.3 N.sub.4) for use as sintered bodies excellent in heat-stability and mechanical strength which comprises heat-treating, in an atmosphere containing nitrogen, a mixture prepared by adding additive:a mixture of at least one of Mg, Ca, and compounds thereof with 0.01-1 part by weight of silicon nitride powder,in a total amount of 0.001-0.1 part by weight calculated in terms of elemental weight(s) of Mg or/and Ca, and 1 part or less by weight of silicon nitride powder, to 1 part by weight of silicon oxide powder and 0.4-4 parts by weight of carbon powder.