Abrasive grain having rare earth oxide therein
AssigneeMinnesota Mining and Manufacturing Company
InventorHenry A. Larmie
Life of this patent
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Abstract
A preferred abrasive grain comprises a sintered product of a precursor material comprising alumina, zirconia, and rare earth oxide. The preferred abrasive grain has an average hardness of at least about 21 GPa and an average toughness of at least about 4 MPa.multidot.m.sup.1/2. A method of preparing preferred abrasive grain is provided. The improved abrasive grain are useful in abrasive products.
Claims22
A ceramic abrasive grain comprising at least about 70 percent by weight alumina, at least about 0.1 percent by weight zirconia, and at least about 0.1 percent by weight metal oxide selected from the group consisting of:
- (a) yttria;
- (b) a rare earth oxide selected from the group of consisting of oxides of:
- ytterbium, neodymium, lanthanum, praseodymium, samarium, gadolinium, cerium, dysprosium, erbium, and mixtures thereof;
- and (c) mixtures thereof, based on the total weight of said abrasive grain, wherein said alumina is present as one of alpha alumina, at least one alumina reaction product, or a combination thereof, said zirconia is present as one of zirconia, at least one zirconia reaction product, or a combination thereof, and said metal oxide is present as one of a metal oxide, at least one metal oxide reaction product, or a combination thereof, and wherein said abrasive grain has an average hardness of at least about 21 GPa and an average toughness of at least about 4 MPa.multidot.m.sup.1/2.
A ceramic abrasive grain comprising by weight:
- (a) about 70 to about 95% alumina, said alumina being present as one of alpha alumina, at least one alumina reaction product, or a combination thereof;
- (b) about 0.1 to about 15% zirconia, said zirconia present as oneof zirconia, at least one zirconia reaction product, or a combination thereof;
- and
- (c) about 0.1 to about 10% rare earth oxide selected from the group consisting of oxides of:
- neodymium, praseodymium, samarium, ytterbium, lanthanum, gadolinium, cerium, dysprosium, erbium, and mixtures thereof, said rare earth oxide being present as on of a rare earth oxide at least one rare earth oxide reaction product or a combination thereof,
- said ceramic abrasive grain having an average hardness of at least about 21 GPa and an average toughness of at least about 4 MPa.multidot.m.sup.1/2.
An alpha alumina-based ceramic abrasive grain comprising at least about 70% by weight alumina, at least about 0.1% by weight zirconia, and at least about 0.1% by weight rare earth oxide, based on total weight of said abrasive grain, and having:
- (a) an alpha alumina matrix comprising alpha alumina crystallites;
- (b) a plurality of equiaxed zirconia particles distributed between said alpha alumina crystallites;
- and
- (c) a plurality of platelets distributed between said alpha alumina crystallites and said zirconia particles, wherein said platelets exhibit a magnetoplumbite crystal structure, and wherein said platelets comprise material represented by the formula:
- MLnAl.sub.11 O.sub.19
- wherein:
- O is oxygen;
- M is a divalent metal cation;
- Ln is a rare earth metal ion;
- and
- Al is aluminum ion,
- said alpha alumina-based ceramic abrasive grain having an average hardness of at least about 21 GPa and an average toughness of at least about 4 MPa.multidot.m.sup.1/2.
A ceramic abrasive grain comprising a sintered product of precursor material comprising:
- (i) at least about 70% by weight alumina;
- (ii) at least about 0.1% by weight zirconia;
- and
- (iii) at least about 0.1% by weight metal oxide selected from the group consisting of:
- yttria;
- a rare earth oxide selected from the group consisting of:
- ytterbium, neodymium, lanthanum, praseodymium, samarium, gadolinium, cerium, dysprosium, erbium and mixtures thereof;
- and mixtures of yttria and said rare earth oxide;
- based on the total weight of said precursor material, said sintered product having an average hardness of at least about 21 GPa and an average toughness of at least about 4 MPa.multidot.m.sup.1/2.
A method of preparing an abrasive grain having an average hardness of at least about 21 GPa and an average toughness of at least about 4 MPa.multidot.m.sup.1/2, said method comprising the steps of:
- (a) providing a dispersion comprising:
- (i) alpha aluminium oxide monohydrate;
- and
- (ii) a zirconium component selected from the group consisting of zirconia particles;
- zirconium salt material;
- and mixtures thereof;
- (b) forming porous solid base grit material from said dispersion;
- (c) impregnating said porous solid base grit material with an impregnating solution of oxide precursor selected from the group consisting of precursor to oxides of:
- ytterbium, neodymium, lanthanum, praseodymium, samarium, gadolinium, cerium, dysprosium, erbium, yttrium, and mixtures thereof;
- and
- (d) converting said impregnated porous solid base grit material to abrasive grain, said step of converting including a step of sintering the base grit material to provide said abrasive grain.
Dependencies are inferred from the claim text.