Abstract: The present invention provides a cerium oxide-based abrasive ensuring high removal rate, less generation of scratches, high-precision polished surface with small surface roughness, and a safe, simple and low-cost production process. Further, the present invention provides a method for producing such an abrasive. The method of the present invention comprises (a) adding a precipitant to an aqueous cerium-containing light rare-earth salt solution to precipitate a light rare-earth salt, thereby obtaining a first slurry containing a light rare-earth salt particle; (b) adding a fluorinating agent to a slurry containing a light rare-earth salt particle to react the light rare-earth salt with the fluorinating agent, thereby obtaining a second slurry containing a light rare-earth fluoride particle; (c) mixing the first slurry and the second slurry to obtain a mixed slurry; and (d) drying and firing the mixed slurry, and a cerium oxide-based abrasive obtained by this method.

Abstract: The present invention provides a cerium oxide-based abrasive ensuring high removal rate, less generation of scratches, high-precision polished surface with small surface roughness, and a safe, simple and low-cost production process. Further, the present invention provides a method for producing such an abrasive. The method of the present invention comprises (a) adding a precipitant to an aqueous cerium-containing light rare-earth salt solution to precipitate a light rare-earth salt, thereby obtaining a first slurry containing a light rare-earth salt particle; (b) adding a fluorinating agent to a slurry containing a light rare-earth salt particle to react the light rare-earth salt with the fluorinating agent, thereby obtaining a second slurry containing a light rare-earth fluoride particle; (c) mixing the first slurry and the second slurry to obtain a mixed slurry; and (d) drying and firing the mixed slurry, and a cerium oxide-based abrasive obtained by this method.

Abstract: The present invention provides a mixed rare earth oxide for the production of a cerium-based abrasive, in which the ignition loss after heating at a temperature of 1,000° C. for 1 hour is 0.5 mass % or less on the dry mass basis and the crystallite diameter is from 200 to 400 ?; a mixed rare earth fluoride for the production of a cerium-based abrasive, in which the ignition loss is from 3 to 15% on the dry mass basis; a process for producing a cerium-based abrasive from these mixed rare earth oxide or mixed rare earth fluoride; and a cerium-based abrasive produced by using these mixed rare earth oxide or mixed rare earth fluoride.

Abstract: Fused alumina particles are covered with a coating of aluminum titanate which is formed by applying a Ti-containing compound to the surface of the fused alumina particles and firing the same to cause a reaction between the Ti-containing compound and the alumina.

Abstract: A sintered alumina abrasive grain comprised of alpha-alumina crystals and a spinel crystalline phase which does not form a continuous phase but is in the form of discrete crystals which are deposited on triple points in alumina crystal boundaries and are substantially uniformly distributed over the abrasive grain. Preferably, the alpha-alumina crystals have an average particle diameter not larger than 1 micron, and the spinel crystalline phase is composed of alumina and an oxide of a metal selected from Ni, Mg and Zn.

Abstract: An abrasive grain for use as a grinding material comprising alpha-alumina crystal particles substantially smaller than 0.5 microns, solidly dissolved with at least one of Ti, Mn, V, Ga, Zn and Rh, and with an a-axis length of the hexagonal unit cell of the alpha-Al.sub.2 O.sub.3 from 4.75892 to 4.76340 angstroms when measured by a powder X-ray diffraction method, and a density of more than 90% of the theoretical value, and an abrasive grain for a grinding material, comprising alpha-alumina crystal particles substantially less than 0.5 microns, solidly dissolved with at least one of Mg, Ni and Co, and with an a-axis length of the hexagonal unit cell of the alpha-Al.sub.2 O.sub.3 from 4.75930 to 4.76340 .ANG. when measured by a powder X-ray diffraction method, and a density of more than 90% of the theoretical value, and further, a grinding wheel and coated cloth manufactured from these abrasive grains.

Abstract: An .alpha.-alumina-based ceramics material comprising crystals of a particle diameter of no greater than 0.2 .mu.m on an average or a particle diameter of substantially no greater than 0.2 .mu.m, and having a density of no lower than 95% of the theoretical density and a hardness of no lower than 2,000 kg/mm.sup.2, and a method for the production thereof.

Abstract: An abrasive grain for use as a grinding material characterized by alpha-corundum crystal particles substantially smaller than 0.5 micron, solidly dissolved with at least one element out of Ti, Mn, V, Ga, Zn and Rh, and with an a-axis length of the hexagonal unit cell of the alpha-Al.sub.2 O.sub.3 at 4.75892 to 4.76340 angstrom when measured by a powder X-ray diffraction method, and a density of more than 90% of the theoretical value, and an abrasive grain for a grinding material, characterized by alpha-corundum crystal particles substantially less than 0.5 micron, solidly dissolved with at least one element out of Mg, Ni and Co, and with an a-axis length of the hexagonal unit cell of the alpha-Al.sub.2 O.sub.3 at 4.75930 to 4.76340 A when measured by a powder X-ray diffraction method, and a density of more than 90% of the theoretical value, and further, a grindstone and grinding cloth manufactured that these abrasive grains.

Abstract: A composition for use in forming a hard tissue substitute comprising (A) a powder ingredient mainly comprised of Ca.sub.n+2 (PO.sub.4).sub.2 O.sub.n-1, where n is from 1.9 to 4.9 and (B) an aqueous solution of an organic acid, preferably of the TCA cycle, or a polymer of an organic acid. This composition has a good affinity with living organisms, a high compressive strength, and a low disintegration rate.

Abstract: Mullite of high purity is obtained by neutralizing an aqueous solution containing a basic aluminum salt and colloidal silica thereby causing formation of a precipitate in the aqueous solution, and subsequently heating the precipitate.

Abstract: From a composition of a fine powder and water, a fine powder minimally susceptible of agglomeration is obtained by a method which comprises adding to the composition of a fine powder and water a water-insoluble organic solvent at least in an amount enough for consequently forming an azeotropic composition with respect to the amount of the water involved, converting the resulting mixed liquid into a W/O type emulsion, and removing the water and the organic solvent from the emulsion.