Sintered alumina-zirconia ceramic bodies
AssigneeNorton Company
InventorsScott W. Pellow, Ronald W. Trischuk, Christopher E. Knapp, Ralph Bauer
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Abstract
Useful ceramic bodies can be made by mixing zirconia powder with seeded alumina gel, drying, and firing at a high enough temperature to convert the alumina in the gel to microcrystalline alpha alumina. Abrasive grits made in this way, with a zirconia content between 15 and 30 weight percent and at least half the zirconia in the tetragonal crystal form are particularly valuable for use in grinding wheels for snagging steels.
Claims37
A ceramic body comprising well intermixed microcrystals of alpha alumina and zirconia with at least three-fourths of said microcrystals appearing to have a maximum dimension between 0.25 and 1 micron when viewed in cross section in an electron micrograph at a magnification of about 10,000-20,000 X, said ceramic body containing from 50 to 95 weight percent of alumina and from 50 to 5 weight percent of zirconia.
A sintered abrasive grit containing from 70-85 weight percent of alumina and 30-15 weight percent of zirconia, both the alumina and the zirconia being in the form of crystals, wherein the alumina crystals have an apparent average size of about 1 micron or less when viewed in cross section in an electron microscope at a magnification of about 10,000-20,000 X, at least one half of the zirconia contained in the grit having the tetragonal crystal form.
A process for making ceramic bodies, comprising the steps of:
- (a) mixing together to form a seeded sol (i) powdered zirconia, (ii) monohydrated alumina, (iii) water, and (iv) a sufficient amount of fine crystalline seeds to facilitate the transformation of monohydrated alumina to crystalline alpha alumina upon heating;
- (b) treating the sol formed in part (a) to produce a gel;
- (c) shaping the gel formed in part (b) into coherent green bodies;
- and
- (d) heating the green bodies sufficiently to convert the monohydrated alumina content of the bodies to alpha alumina crystals, said crystals having a maximum dimension of about 1 micron or less when viewed in cross section in an electron micrograph at a magnification of about 10,000-20,000 X.
Dependencies are inferred from the claim text.