Agglomerate abrasive grain and a method of making the same

• US 20020160694A1
• Filed: 10/05/2001
• Published: 10/31/2002
• Est. Priority Date: 10/06/2000
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: McArdle, James L., Wood, William P.
• Granted Patent: US 6,790,126 B2
• Time in Patent Office: Days
• US Class Current: 451/41
• CPC Class Codes: B24D 18/00 Manufacture of grinding tools or other grinding devices, e.g. wheels, not otherwise provided for
• CPC Class Codes: B24D 3/04 and being essentially inorganic
• CPC Class Codes: B24D 3/06 metallic or mixture of metals with ceramic materials, e.g. hard metals, "cermets", cements
• CPC Class Codes: C04B 2235/3206 Magnesium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3218 Aluminium (oxy)hydroxides, e.g. boehmite, gibbsite, alumina sol
• CPC Class Codes: C04B 2235/3224 Rare earth oxide or oxide forming salts thereof, e.g. scandium oxide
• CPC Class Codes: C04B 2235/3225 Yttrium oxide or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3227 Lanthanum oxide or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3272 Iron oxides or oxide forming salts thereof, e.g. hematite, magnetite
• CPC Class Codes: C04B 2235/3275 Cobalt oxides, cobaltates or cobaltites or oxide forming salts thereof, e.g. bismuth cobaltate, zinc cobaltite
• CPC Class Codes: C04B 2235/443 Nitrates or nitrites
• CPC Class Codes: C04B 2235/5427 millimeter or submillimeter sized, i.e. larger than 0,1 mm
• CPC Class Codes: C04B 2235/5472 Bimodal, multi-modal or multi-fraction
• CPC Class Codes: C04B 2235/6021 Extrusion moulding
• CPC Class Codes: C04B 2235/77 Density
• CPC Class Codes: C04B 35/00 Shaped ceramic products characterised by their composition porous ceramic products C04B38/00; ceramic articles characterised by particular shape, see the relevant classes, e.g. linings for casting ladles, tundishes, cups or the like B22D41/02; ceramic substrates for microelectronic semi-conductors H01L23/15; Ceramics compositions containing free metal bonded to carbides, diamond, oxides, borides, nitrides, silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides or sulfides other than as macroscopic reinforcing agents C22C; shaping of ceramics B28B; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products chemical preparation of powders of inorganic compounds C01; infiltration of sintered ceramic preforms with molten metal C04B41/51
• CPC Class Codes: C04B 35/1115 Minute sintered entities, e.g. sintered abrasive grains or shaped particles such as platelets abrasives C09K3/14
• CPC Class Codes: C04B 35/44 based on aluminates
• CPC Class Codes: C04B 35/622 Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
• CPC Class Codes: C04B 35/62815 Rare earth metal oxides
• CPC Class Codes: C04B 35/62886 : by wet chemical techniques
• CPC Class Codes: C04B 35/6303 : Inorganic additives
• CPC Class Codes: C04B 35/6316 : Binders based on silicon compounds
• CPC Class Codes: C09K 3/1409 : Abrasive particles per se preparation of diamond C01B32/25
• CPC Class Codes: C09K 3/1427 : obtained by division of a mass agglomerated by melting, at least partially, e.g. with a binder
• CPC Class Codes: C09K 3/1436 : Composite particles, e.g. coated particles
• CPC Class Codes: Y10T 428/2982 : Particulate matter [e.g., sphere, flake, etc.]
• CPC Class Codes: Y10T 428/2991 : Coated
• CPC Class Codes: Y10T 428/2993 : Silicic or refractory material containing [e.g., tungsten oxide, glass, cement, etc.]
• CPC Class Codes: Y10T 428/2996 : Glass particles or spheres
• CPC Class Codes: Y10T 428/2998 : including synthetic resin or polymer

Abstract

Agglomerate abrasive grain is disclosed. The agglomerate abrasive grain can be incorporated into abrasive products such as coated abrasives, bonded abrasives, nonwoven abrasives, and abrasive brushes. A method of making agglomerate abrasive grain is also disclosed.

Claims

1. Agglomerate abrasive grain comprising a plurality of abrasive particles bonded together with a sintered, crystalline ceramic bonding material, wherein the bonding material comprises, on a theoretical oxide basis, at least 50 percent by weight crystalline Al₂O₃, based on a total metal oxide content of the bonding material, and wherein the abrasive particles have an average particle size of at least 5 micrometers.

2. The agglomerate abrasive grain according to claim 1, wherein the average particle size of the particles is at least 25 micrometers.

3. The agglomerate abrasive grain according to claim 1, wherein the average particle size of the particles is at least 100 micrometers.

4. The agglomerate abrasive grain according to claim 1, wherein the abrasive particles comprise fused abrasive particles.

5. The agglomerate abrasive grain according to claim 1, wherein the abrasive particles include abrasive particles selected from the group consisting of fused aluminum oxide abrasive particles, white fused aluminum oxide abrasive particles, heat-treated fused aluminum oxide abrasive particles, brown fused aluminum oxide abrasive particles, silicon carbide abrasive particles, boron carbide abrasive particles, titanium carbide abrasive particles, diamond abrasive particles, cubic boron nitride abrasive particles, garnet abrasive particles, fused alumina-zirconia abrasive particles, sintered alpha alumina-based abrasive particles, boehmite-derived, sintered alumina abrasive particles, and a combination thereof.

6. The agglomerate abrasive grain according to claim 1, wherein the bonding material comprises, on a theoretical oxide basis, at least 60 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material.

7. The agglomerate abrasive grain according to claim 1, wherein the bonding material comprises, on a theoretical oxide basis, at least 90 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material.

8. The agglomerate abrasive grain according to claim 1, wherein the bonding material comprises, on a theoretical oxide basis, at least 95 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material.

9. The agglomerate abrasive grain according to claim 1, wherein the abrasive particles include sintered, alpha alumina-based abrasive particles.

10. The agglomerate abrasive grain according to claim 9, wherein the sintered, alpha alumina-based abrasive particles comprise of alpha alumina crystals having an average crystal size of less than 1 micrometer.

11. The agglomerate abrasive grain according to claim 9, wherein the bonding material and the sintered, ceramic alpha alumina-based abrasive particles have substantially the same composition.

12. The agglomerate abrasive grain according to claim 9, wherein the bonding material and the sintered, ceramic alpha alumina-based abrasive particles have substantially the same composition and microstructure.

13. An abrasive article including:

binder material; and

a plurality of agglomerate abrasive grain according to claim 1 secured within said article by said binder material.

15. The agglomerate abrasive grain according to claim 14, wherein the abrasive particles have a density of at least 95% of theoretical density.

16. The agglomerate abrasive grain according to claim 14, wherein the abrasive grain has a porosity value of at least 30 percent.

17. The agglomerate abrasive grain according to claim 14, wherein the abrasive particles comprise fused abrasive particles.

18. The agglomerate abrasive grain according to claim 14, wherein the abrasive particles comprise sintered, alpha alumina-based abrasive particles.

19. The agglomerate abrasive grain according to claim 14, wherein the abrasive particles include abrasive particles selected from the group consisting of fused aluminum oxide abrasive particles, white fused aluminum oxide abrasive particles, heat-treated fused aluminum oxide abrasive particles, brown fused aluminum oxide abrasive particles, silicon carbide abrasive particles, boron carbide abrasive particles, titanium carbide abrasive particles, diamond abrasive particles, cubic boron nitride abrasive particles, garnet abrasive particles, fused alumina-zirconia abrasive particles, sintered alpha alumina-based abrasive particles, boehmite-derived, sintered alumina abrasive particles, and a combination thereof.

20. The agglomerate abrasive grain according to claim 14, wherein the bonding material comprises, on a theoretical oxide basis, at least 60 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material.

21. The agglomerate abrasive grain according to claim 14, wherein the bonding material comprises, on a theoretical oxide basis, at least 90 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material.

22. The agglomerate abrasive grain according to claim 14, wherein the bonding material and the sintered, ceramic alpha alumina-based abrasive particles have substantially the same composition.

23. The agglomerate abrasive grain according to claim 14, wherein the bonding material and the sintered, ceramic alpha alumina-based abrasive particles have substantially the same composition and microstructure.

24. An abrasive article including:

binder material; and

a plurality of agglomerate abrasive grain according to claim 17 secured within said article by said binder material.

26. The method according to claim 25, wherein the abrasive particles comprise fused abrasive particles.

27. The method according to claim 25, wherein the abrasive particles include abrasive particles selected from the group consisting of fused aluminum oxide abrasive particles, white fused alumina abrasive particles, heat-treated aluminum oxide abrasive particles, brown aluminum oxide abrasive particles, silicon carbide abrasive particles, boron carbide abrasive particles, titanium carbide abrasive particles, diamond abrasive particles, cubic boron nitride abrasive particles, garnet abrasive particles, fused alumina-zirconia abrasive particles, sintered alpha alumina-based abrasive particles, boehmite-derived alumina abrasive particles, and a combination thereof.

28. The method according to claim 25, wherein the precursor abrasive particles comprise boehmite.

29. The method according to claim 25, wherein the bonding material comprises, on a theoretical oxide basis, at least 60 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material.

30. The method according to claim 25, wherein the bonding material comprises, on a theoretical oxide basis, at least 90 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material.

31. The method according to claim 25, further comprising, prior to said heating:

drying the agglomerated particles;

calcining the dried agglomerated particles to provide porous agglomerated particles; and

impregnating the porous agglomerated particles with a composition comprising water and at least one of metal oxide or metal oxide precursor.

32. The method according to claim 25, wherein the average particle size of the particles is at least 25 micrometers.

33. The method according to claim 25, wherein the average particle size of the particles is at least 100 micrometers.

34. The method according to claim 25, wherein the abrasive particles are comprised of crystals having an average crystal size less than 10 micrometers.

35. The method according to claim 25, wherein the abrasive particles include sintered, crystalline ceramic alpha alumina-based abrasive particles.

36. The method according to claim 25, wherein the bonding material and the sintered, ceramic alpha alumina-based abrasive particles have substantially the same composition.

37. The method according to claim 25, wherein the bonding material and the sintered, ceramic alpha alumina-based abrasive particles have substantially the same composition and microstructure.

38. The method according to claim 25, wherein the abrasive particles of the agglomerate abrasive grain have a density of at least 85% of theoretical density, and the agglomerate abrasive grain has a porosity value of at least 30 percent.

40. The method according to claim 39, wherein the abrasive particles comprise fused abrasive particles.

41. The method according to claim 39, wherein the abrasive particles include abrasive particles selected from the group consisting of fused aluminum oxide abrasive particles, white fused alumina abrasive particles, heat-treated aluminum oxide abrasive particles, brown aluminum oxide abrasive particles, silicon carbide abrasive particles, boron carbide abrasive particles, titanium carbide abrasive particles, diamond abrasive particles, cubic boron nitride abrasive particles, garnet abrasive particles, fused alumina-zirconia abrasive particles, sintered alpha alumina-based abrasive particles, boehmite-based alumina abrasive particles, and a combination thereof.

42. The method according to claim 39, wherein the precursor abrasive particles comprise boehmite.

43. The method according to claim 39, wherein the bonding material comprises, on a theoretical oxide basis, at least 60 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material.

44. The method according to claim 39, wherein the bonding material comprises, on a theoretical oxide basis, at least 90 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material.

45. The method according to claim 39, further comprising, prior to said heating:

drying the agglomerated particles;

calcining the dried agglomerated particles to provide porous agglomerated particles; and

impregnating the porous agglomerated particles with a composition comprising water and at least one of metal oxide or metal oxide precursor.

46. The method according to claim 39, wherein the average particle size of the particles is at least 25 micrometers.

47. The method according to claim 39, wherein the average particle size of the particles is at least 100 micrometers.

48. The method according to claim 39, wherein the abrasive particles are comprised of crystals having an average crystal size less than 10 micrometers.

49. The method according to claim 39, wherein the abrasive particles include sintered, crystalline ceramic alpha alumina-based abrasive particles.

50. The method according to claim 39, wherein the bonding material and the sintered, ceramic alpha alumina-based abrasive particles have substantially the same composition.

51. The method according to claim 39, wherein the bonding material and the sintered, ceramic alpha alumina-based abrasive particles have substantially the same composition and microstructure.

52. The method according to claim 39, wherein the abrasive particles have a density of at least 95% of theoretical density.

53. The method according to claim 39, wherein the abrasive grain has a porosity value of at least 30 percent.

14. Agglomerate abrasive grain comprising a plurality of polycrystalline abrasive particles bonded together with a sintered, crystalline ceramic bonding material, wherein the bonding material comprises, on a theoretical oxide basis, at least 50 percent by weight crystalline Al₂O₃, based on a total metal oxide content of the bonding material, the abrasive particles have a density of at least 85% of theoretical density, and the agglomerate abrasive grain has a porosity value of at least 10 percent.

25. A method for making agglomerate abrasive grain comprising:

contacting a plurality of at least one of abrasive particles or precursor abrasive particles with a precursor bonding material such that the particles agglomerate together; and

heating the agglomerated particles at at least one temperature for a time sufficient to convert the agglomerated particles, into agglomerate abrasive grain comprising a plurality of abrasive particles bonded together with a sintered bonding material;

wherein the sintered bonding material comprises, on a theoretical oxide basis, at least 50 percent by weight crystalline Al₂O₃, based on the total metal oxide content of the bonding material; and

wherein the abrasive particles of the agglomerate abrasive grain have an average particle size of at least 5 micrometers.

39. A method for making agglomerate abrasive grain comprising:

contacting a plurality of at least one of abrasive particles or precursor abrasive particles with a precursor bonding material such that the particles agglomerate together; and

heating the agglomerated particles at at least one temperature for a time sufficient to convert the agglomerated particles into agglomerate abrasive grain comprising a plurality of abrasive particles bonded together with a sintered bonding material;

wherein the sintered bonding material comprises, on a theoretical oxide basis, at least 50 percent by weight crystalline Al₂O₃, based on the total metal oxide content of the bonding material; and

wherein the heat-treated abrasive particles have a density of at least 85% of theoretical density, and the agglomerate abrasive grain has a porosity value of at least 10 percent.

54. Agglomerate abrasive grain comprising a, plurality of sintered polycrystalline abrasive particles bonded together via crystalline ceramic, metal oxide bonding material, wherein the bonding material comprises, on a theoretical oxide basis, at least 50 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material, wherein the crystalline abrasive particles are comprised of crystals having an average size less than 10 micrometers, and wherein at least three of the largest abrasive particles have substantially the same volume.

55. The agglomerate abrasive grain according to claim 54, wherein the bonding material comprises, on a theoretical oxide basis, at least 60 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material.

56. The agglomerate abrasive grain according to claim 54, wherein the bonding material comprises, on a theoretical oxide basis, at least 95 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material.

57. The agglomerate abrasive grain according to claim 54, wherein the crystalline abrasive particles include alpha alumina-based abrasive particles.

58. The agglomerate abrasive grain according to claim 54, wherein the crystalline abrasive particles include sintered, crystalline ceramic alpha alumina-based abrasive particles.

59. The agglomerate abrasive grain according to claim 58, wherein the sintered, crystalline ceramic alpha alumina-based abrasive particles are comprised of alpha alumina crystals, and wherein the average size of the alpha alumina crystals is less than 1 micrometer.

60. The agglomerate abrasive grain according to claim 54, wherein the crystalline ceramic, metal oxide bonding material and the sintered, ceramic alpha alumina-based abrasive particles have substantially the same composition and microstructure.

61. An abrasive article including:

binder material; and

a plurality of agglomerate abrasive grain according to claim 55 secured within said article by said binder material.

62. Agglomerate abrasive grain comprising a plurality of sintered, crystalline abrasive particles bonded together via crystalline ceramic, metal oxide bonding material, wherein the bonding material comprises, on a theoretical oxide basis, at least 50 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material, wherein the crystalline abrasive particles are comprised of crystals having an average size less than 10 micrometers, and wherein at least three of the largest abrasive particles are greater than 20 micrometers in size.

63. The agglomerate abrasive grain according to claim 62, wherein the bonding material comprises, on a theoretical oxide basis, at least 60 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material.

64. The agglomerate abrasive grain according to claim 62, wherein the bonding material comprises, on a theoretical oxide basis, at least 90 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material.

65. The agglomerate abrasive grain according to claim 62, wherein the crystalline abrasive particles include alpha alumina-based abrasive particles.

66. The agglomerate abrasive grain according to claim 62, wherein the crystalline abrasive particles include sintered, crystalline ceramic alpha alumina-based abrasive particles.

67. The agglomerate abrasive grain according to claim 66, wherein the sintered, crystalline ceramic alpha alumina-based abrasive particles are comprised of alpha alumina crystals, and wherein the average size of the alpha alumina crystals is less than 1 micrometer.

68. The agglomerate abrasive grain according to claim 66, wherein the crystalline ceramic, metal oxide bonding material and the sintered, ceramic alpha alumina-based abrasive particles have substantially the same composition and microstructure.

69. The agglomerate abrasive grain according to claim 62, wherein at least three of the largest abrasive particles are greater than 40 micrometers in size.

70. An abrasive article including:

binder material; and

a plurality of agglomerate abrasive grain according to claim 62 secured within said article by said binder material.

71. Agglomerate abrasive grain comprising a plurality of sintered, crystalline abrasive particles bonded together via crystalline ceramic, metal oxide bonding material, wherein said agglomerate abrasive grain comprises, on a theoretical oxide basis, at least 85% by weight Al₂O₃, based on the total metal oxide content of the agglomerate abrasive grain, and wherein at least three of the largest abrasive particles are greater than 20 micrometers in size.

72. The agglomerate abrasive grain according to claim 71, wherein the bonding material comprises, on a theoretical oxide basis, at least 97 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material.

73. The agglomerate abrasive grain according to claim 71, wherein the crystalline abrasive particles include alpha alumina-based abrasive particles.

74. The agglomerate abrasive grain according to claim 71, wherein the crystalline abrasive particles include sintered, crystalline ceramic alpha alumina-based abrasive particles.

75. The agglomerate abrasive grain according to claim 74, wherein the sintered, crystalline ceramic alpha alumina-based abrasive particles are comprised of alpha alumina crystals, and wherein the average size of the alpha alumina crystals is less than 1 micrometer.

76. The agglomerate abrasive grain according to claim 74, wherein the crystalline ceramic, metal oxide bonding material and the sintered, ceramic alpha alumina-based abrasive particles have substantially the same composition and microstructure.

77. The agglomerate abrasive grain according to claim 71, wherein at least three of the largest abrasive particles are greater than 40 micrometers in size.

78. An abrasive article including:

binder material; and

a plurality of agglomerate abrasive grain according to claim 71 secured within said article by said binder material.

80. The agglomerate abrasive grain according to claim 79, wherein the plurality of abrasive particles has a porosity value of at least 30 percent.

81. The agglomerate abrasive grain according to claim 79, wherein the agglomerate abrasive grain has a porosity value in the range from 30 to about 45 percent.

82. The agglomerate abrasive grain according to claim 79, wherein the bonding material comprises, on a theoretical oxide basis, at least 60 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material.

83. The agglomerate abrasive grain according to claim 79, wherein the bonding material comprises, on a theoretical oxide basis, at least 90 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material.

84. The agglomerate abrasive grain according to claim 79, wherein the bonding material comprises, on a theoretical oxide basis, at least 95 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material.

85. The agglomerate abrasive grain according to claim 79, wherein the crystalline abrasive particles include alpha alumina-based abrasive particles.

86. The agglomerate abrasive grain according to claim 79, wherein the crystalline abrasive particles include sintered, crystalline ceramic alpha alumina-based abrasive particles.

87. The agglomerate abrasive grain according to claim 86, wherein the sintered, crystalline ceramic alpha alumina-based abrasive particles are comprised of alpha alumina crystals, and wherein the average size of the alpha alumina crystals is less than 1 micrometer.

88. The agglomerate abrasive grain according to claim 86, wherein the crystalline ceramic, metal oxide bonding material and the sintered, ceramic alpha alumina-based abrasive particles have substantially the same composition and microstructure.

89. The agglomerate abrasive grain according to claim 79, wherein at least three of the largest abrasive particles are greater than 20 micrometers in size.

90. An abrasive article including:

binder material; and

a plurality of agglomerate abrasive grain according to claim 79 secured within said article by said binder material.

79. Agglomerate abrasive grain comprising a plurality of sintered, polycrystalline abrasive particles bonded together via crystalline ceramic, metal oxide bonding material, wherein the bonding material comprises, on a theoretical oxide basis, at least 50 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material, and wherein the agglomerate abrasive grain has a porosity value in the range from 10 to about 60 percent.

91. A method for making agglomerate abrasive grain comprising a plurality of sintered, crystalline, alpha alumina-based abrasive particles bonded together via crystalline ceramic, metal oxide bonding material, wherein the bonding material comprises, on a theoretical oxide basis, at least 50 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material, and wherein at least three of the largest abrasive particles have substantially the same volume, said method comprising:

contacting dried, boehmite-based precursor particles in the presence of liquid such that a plurality of said precursor particles agglomerate together; and

heating the agglomerated particles at at least one temperature for a time sufficient to provide said agglomerate abrasive grain.

92. The method according to claim 91, wherein the liquid comprises water.

93. The method according to claim 91, wherein the liquid comprises acidified water.

94. The method according to claim 91, wherein the liquid comprises water and metal oxide precursor.

95. The method according to claim 94, wherein the metal oxide precursor is a metal nitrate salt in solution.

96. The method according to claim 91, wherein the liquid comprises water and metal oxide precursor selected from the group consisting of chromium nitrate, cobalt nitrate, dysprosium nitrate, erbium nitrate, europium nitrate, ferric nitrate, gadolinium nitrate, ferric nitrate, lanthanum nitrate, lithium nitrate, magnesium nitrate, manganese nitrate, neodymium nitrate, nickel nitrate, praseodymium nitrate, samarium nitrate, yttrium nitrate, zinc nitrate, zirconium hydroxynitrate, zirconium nitrate, zirconium oxynitrate, and combinations thereof in solution.

97. The method according to claim 91, wherein contacting the dried, boehmite-based precursor particles in the presence of liquid includes rotating the particles in the presence of the liquid with a disc agglomerator.

98. The method according to claim 91, wherein the bonding material and the sintered, crystalline, alpha alumina-based abrasive particles comprise, on a theoretical oxide basis, at least 60 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material.

99. The method according to claim 91, wherein the bonding material and the sintered, crystalline, alpha alumina-based abrasive particles comprise, on a theoretical oxide basis, at least 90 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material.

100. A method for making agglomerate abrasive grain comprising a plurality of sintered, crystalline, alpha alumina-based abrasive particles bonded together via crystalline ceramic, metal oxide bonding material, wherein the bonding material comprises, on a theoretical oxide basis, at least 50 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material, and wherein at least three of the largest abrasive particles have substantially the same volume, said method comprising:

contacting dried, boehmite-based precursor particles in the presence of liquid such that a plurality of said precursor particles agglomerate together;

drying the agglomerated precursor particles;

calcining the dried agglomerated precursor particles to provide porous agglomerated precursor particles;

impregnating the porous agglomerated precursor particles with a composition comprising liquid and at least one of metal oxide or metal oxide precursor;

heating the impregnated, agglomerated precursor particles at at least one temperature for a time sufficient to provide said agglomerate abrasive grain.

101. A method for making agglomerate abrasive grain comprising a plurality of sintered, crystalline, alpha alumina-based abrasive particles bonded together via crystalline ceramic, metal oxide bonding material, wherein the bonding material comprises, on a theoretical oxide basis, at least 50 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material, and wherein at least three of the largest abrasive particles are greater than 20 micrometers in size, said method comprising:

contacting dried, boehmite-based precursor particles in the presence of liquid such that a plurality of said precursor particles agglomerate together; and

heating the agglomerated particles at at least one temperature for a time sufficient to provide said agglomerate abrasive grain.

102. The method according to claim 101, wherein the liquid comprises water.

103. The method according to claim 101, wherein the liquid comprises acidified water.

104. The method according to claim 101, wherein the liquid comprises water and metal oxide precursor.

105. The method according to claim 104, wherein the metal oxide precursor is a metal nitrate salt in solution.

106. The method according to claim 101, wherein the liquid comprises water and metal oxide precursor selected from the group consisting of chromium nitrate, cobalt nitrate, dysprosium nitrate, erbium nitrate, europium nitrate, ferric nitrate, gadolinium nitrate, ferric nitrate, lanthanum nitrate, lithium nitrate, magnesium nitrate, manganese nitrate, neodymium nitrate, nickel nitrate, praseodymium nitrate, samarium nitrate, yttrium nitrate, zinc nitrate, zirconium hydroxynitrate, zirconium nitrate, zirconium oxynitrate, and combinations thereof in solution.

107. The method according to claim 101, wherein contacting the dried, boehmite-based precursor particles in the presence of liquid includes rotating the particles in the presence of the liquid with a disc agglomerator.

108. The method according to claim 101, wherein the sintered, crystalline, alpha alumina-based abrasive particles are comprised of alpha alumina crystals having an average size less than 10 micrometers.

109. The method according to claim 101, wherein the bonding material and the sintered, crystalline, alpha alumina-based abrasive particles comprise, on a theoretical oxide basis, at least 60 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material.

110. The method according to claim 101, wherein the bonding material and the sintered, crystalline, alpha alumina-based abrasive particles comprise, on a theoretical oxide basis, at least 90 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material.

111. A method for making agglomerate abrasive grain comprising a plurality of sintered, crystalline, alpha alumina-based abrasive particles bonded together via crystalline ceramic, metal oxide bonding material, wherein the bonding material comprises, on a theoretical oxide basis, at least 50 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material, and wherein at least three of the largest abrasive particles are greater than 20 micrometers in size, said method comprising:

contacting dried, boehmite-based precursor particles in the presence of liquid such that a plurality of said precursor particles agglomerate together;

drying the agglomerated precursor particles;

calcining the dried agglomerated precursor particles to provide porous agglomerated precursor particles;

impregnating the porous agglomerated precursor particles with a composition comprising liquid and at least one of metal oxide or metal oxide precursor; and

heating the impregnated, agglomerated precursor particles at at least one temperature for a time sufficient to provide said agglomerate abrasive grain.

113. The method according to claim 112, wherein the liquid comprises water.

114. The method according to claim 112, wherein the liquid comprises acidified water.

115. The method according to claim 112, wherein the liquid comprises water and metal oxide precursor.

116. The method according to claim 115, wherein the metal oxide precursor is a metal nitrate salt in solution.

117. The method according to claim 112, wherein the liquid comprises water and metal oxide precursor selected from the group consisting of chromium nitrate, cobalt nitrate, dysprosium nitrate, erbium nitrate, europium nitrate, ferric nitrate, gadolinium nitrate, ferric nitrate, lanthanum nitrate, lithium nitrate, magnesium nitrate, manganese nitrate, neodymium nitrate, nickel nitrate, praseodymium nitrate, samarium nitrate, yttrium nitrate, zinc nitrate, zirconium hydroxynitrate, zirconium nitrate, zirconium oxynitrate, and combinations thereof in solution.

118. The method according to claim 112, wherein contacting the dried, boehmite-based precursor particles in the presence of liquid includes rotating the particles in the presence of the liquid with a disc agglomerator.

119. The method according to claim 112, wherein the sintered, crystalline, alpha alumina-based abrasive particles are comprised of alpha alumina crystals having an average size less than 5 micrometers.

120. The method according to claim 112, wherein at least three of the largest abrasive particles are greater than 40 micrometers in size.

121. The method according to claim 112, wherein the bonding material and the sintered, crystalline, alpha alumina-based abrasive particles comprise, on a theoretical oxide basis, at least 95 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material.

124. The method according to claim 123, wherein the liquid comprises water.

125. The method according to claim 123, wherein the liquid comprises acidified water.

126. The method according to claim 123, wherein the liquid comprises water and metal oxide precursor.

127. The method according to claim 126, wherein the metal oxide precursor is a metal nitrate salt in solution.

128. The method according to claim 123, wherein the liquid comprises water and metal oxide precursor selected from the group consisting of chromium nitrate, cobalt nitrate, dysprosium nitrate, erbium nitrate, europium nitrate, ferric nitrate, gadolinium nitrate, ferric nitrate, lanthanum nitrate, lithium nitrate, magnesium nitrate, manganese nitrate, neodymium nitrate, nickel nitrate, praseodymium nitrate, samarium nitrate, yttrium nitrate, zinc nitrate, zirconium hydroxynitrate, zirconium nitrate, zirconium oxynitrate, and combinations thereof in solution.

129. The method according to claim 123, wherein contacting the dried, boehmite-based precursor particles in the presence of liquid includes rotating the particles in the presence of the liquid with a disc agglomerator.

130. The method according to claim 123, wherein the sintered, crystalline, alpha alumina-based abrasive particles are comprised of alpha alumina crystals having an average size less than 5 micrometers.

131. The method according to claim 123, wherein at least three of the largest abrasive particles are greater than 40 micrometers in size.

132. The method according to claim 123, wherein the bonding material and the sintered, crystalline, alpha alumina-based abrasive particles comprise, on a theoretical oxide basis, at least 60 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material.

133. The method according to claim 123, wherein the bonding material and the sintered, crystalline, alpha alumina-based abrasive particles comprise, on a theoretical oxide basis, at least 90 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material.

134. The method according to claim 123, wherein the plurality of abrasive particles has a porosity value of at least 30 percent.

135. The method according to claim 123, wherein the agglomerate abrasive grain has a porosity value in the range from 20 to about 50 percent.

136. The method according to claim 123, wherein the agglomerate abrasive grain has a porosity value in the range from 30 to about 45 percent.

112. A method for making agglomerate abrasive grain comprising a plurality of sintered, crystalline, alpha alumina-based abrasive particles bonded together via crystalline ceramic, metal oxide bonding material, wherein said agglomerate abrasive grain comprises, on a theoretical oxide basis, at least 85% by weight alumina, based on the total metal oxide content of the agglomerate abrasive grain, and wherein at least three of the largest abrasive particles are greater than 20 micrometers in size, said method comprising:

contacting dried, boehmite-based precursor particles in the presence of liquid such that a plurality of said precursor particles agglomerate together; and

heating the agglomerated particles at at least one temperature for a time sufficient to provide the agglomerate abrasive grain.

122. A method for making agglomerate abrasive grain comprising a plurality of sintered, crystalline, alpha alumina-based abrasive particles bonded together via crystalline ceramic, metal oxide bonding material, wherein said agglomerate abrasive grain comprises, on a theoretical oxide basis, at least 85% by weight alumina, based on the total metal oxide content of the agglomerate abrasive grain, and wherein at least three of the largest abrasive particles are greater than 20 micrometers in size, said method comprising:

contacting dried, boehmite-based precursor particles in the presence of liquid such that a plurality of said precursor particles agglomerate together;

drying the agglomerated precursor particles;

calcining the dried agglomerated precursor particles to provide porous agglomerated precursor particles;

impregnating the porous agglomerated precursor particles with a composition comprising liquid and at least one of metal oxide or metal oxide precursor; and

heating the impregnated, agglomerated precursor particles at at least one temperature for a time sufficient to provide said agglomerate abrasive grain.

123. A method for making agglomerate abrasive grain comprising a plurality of sintered, crystalline, alpha alumina-based abrasive particles bonded together via crystalline ceramic, metal oxide bonding material, wherein the bonding material comprises, on a theoretical oxide basis, at least 50 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material, and wherein said agglomerate abrasive grain has a porosity value in the range from 10 to 60 percent, said method comprising:

contacting dried, boehmite-based precursor particles in the presence of liquid such that a plurality of said precursor particles agglomerate together; and

heating the agglomerated particles at at least one temperature for a time sufficient to provide said agglomerate abrasive grain.

137. A method for making agglomerate abrasive grain comprising a plurality of sintered, crystalline, alpha alumina-based abrasive particles bonded together via crystalline ceramic, metal oxide bonding material, wherein the bonding material comprises, on a theoretical oxide basis, at least 50 percent by weight Al₂O₃, based on the total metal oxide content of the bonding material, and wherein said agglomerate abrasive grain has a porosity value in the range from 10 to 60 percent, said method comprising:

contacting dried, boehmite-based precursor particles in the presence of liquid such that a plurality of said precursor particles agglomerate together;

drying the agglomerated precursor particles;