Abstract: A process for forming a ceramic alumina-based abrasive grain from a sol gel which contains aluminum oxide monohydrate, a dissolved metal containing sintering aid and sufficient sodium and/or calcium compound to provide in the ceramic from above about 0.05 to about 1.8 weight percent sodium plus calcium, provided that the weight percent calcium is from 0 to about 1.8 and the weight percent sodium is from 0 to about 0.4. The high sodium and calcium is permitted due to rapid heating of the sol gel after drying through a temperature range of from below about 800.degree. C. to above about 1200.degree. C., prior to sintering the dried gel at a temperature above 1200.degree. C. A grain made by the process and coated, bonded and non-woven abrasive articles comprising the grain.

Abstract: The invention comprises a method of making self-supporting ceramic and ceramic composite structures by the oxidation reaction of a body of molten parent metal precursor with a vapor-phase oxidant to form an oxidation reaction product. This reaction or growth is continued to form a thick, self-supporting ceramic or ceramic composite body. The body is recovered and in a separate subsequent operation, at least a portion of a surface is coated with one or more materials in order to effect desired changes in the properties of the surface, e.g., hardness, corrosion resistance.

Abstract: The sol-gel process for forming dense, alumina-base ceramics, the process comprising1. preparing a dispersion of aluminum oxide monohydrate containing a precursor of a modifying additive in the form of a soluble salt;2. gelling the dispersion;3. drying the gel dispersion to form a solid;4. calcining the solid; and5. sintering the calcined solid,is improved by adding to the dispersion at least about 10 weight percent, based on the oxide equivalent of the soluble salt precursor, of at least one densification aid selected from the group consisting of alcohols, glycols and polyether compounds having a vaporization point in excess of the temperature at which the dispersion is dried. This improved process is particularly useful for manufacturing abrasive grains.