Abrasive grits formed by ceramic impregnation method of making the same, and products made therewith

Claim 1

Ceramic abrasive grits comprising alpha alumina and at least about 0.5% by weight of at least one modifying metal oxide, the metal of the metal oxide being selected from the group consisting of zirconium, hafnium, cobalt, nickel, zinc, magnesium, yttrium, praseodymium, samarium, ytterbium, neodymium, lanthanum, gadolinium, cerium, dysprosium, erbium, and combinations of two or more of such metals, wherein the concentration of said modifying metal oxide is greater at or near the surface of said grit than at the interior of said grit.

Claim 25

A method of making ceramic abrasive grits, said method comprising the steps of: (1) preparing a sol of alumina hydrate; (2) drying the sol to form a dried porous solid comprised of the dried sol; (3) crushing the dried porous solid to produce particles; (4) preparing a homogeneous mixture of metal oxide metal oxide or its precursor in a liquid vehicle; (5) calcining the dried particles to substantially remove water of hydration and convert the alumina hydrate to an alumina form which is insoluble in said liquid vehicle; (6) impregnating the mixture of step (4) into the calcined particles to achieve an average concentration of modifying additive in the resultant ceramic after firing of at least about 0.5% by weight on a fired solids basis; (7) drying the impregnated particles; (8) calcining the dried impregnated particles to substantially remove bound volatile materials; and (9) firing the grits to produce ceramic abrasive grits.

Claim 26

A method of making ceramic abrasive grits, said method comprising the steps of: (1) preparing a sol of alumina hydrate; (2) drying the sol to form a dried porous solid comprised of the dried sol; (3) crushing the dried porous solid to produce particles; (4) preparing a homogeneous mixture of metal oxide metal oxide or its precursor in a liquid vehicle; (5) calcining the dried particles to substantially remove water of hydration and convert the alumina hydrate to an alumina form which is insoluble in said liquid vehicle; (6) impregnating the mixture of step (4) into the calcined particles to achieve an average concentration of modifying additive in the resultant ceramic after firing of at least about 0.5% by weight on a fired solids basis; (7) drying the impregnated particles; (8) calcining the dried impregnated particles to substantially remove bound volatile materials; and (9) firing the grits to produce ceramic abrasive grits.