Sol-gel abrasive grains

Sol-Gel Abrasive Grains—History, Precursor Properties and Microstructural Control... 

One of the routes to dense, fine-microstructured, polycrystaUine abrasive minerals considered by 3M at that time (-1974) was sol-gel technology. Prior to work on abrasives, 3M s Dr. Harold Sowman had been successful utilizing sol-gel approaches for the synthesis of nuclear fuel pellets and production of ceramic fibers. He, along with Dr. Melvin Leitheiser, initiated an effort to develop new aluminous abrasive minerals based on sol-gel technology. They focused their effort on the conversion of colloidal boehmite, y-AlOOH, into dense, polycrystalline alumina. Since that time, boehmite has become, not only the precursor of choice for sol-gel abrasive grains, but the precursor of choice for virtually every sol-gel alumina process. 

Boehmite possesses several characteristics that make it the alumina precursor of choice for manufacture of sol-gel abrasive grains. Boehmite is readily dispersible in acidified water to form electrostatically-stabilized, high solids colloidal dispersions. Other particulate forms of alumina including alpha alumina and aluminum hydroxide are not readily available in nanoparticle size and require organic additives to form finely divided, high solids dispersions. The point of zero charge and the isoelectric point of boehmite are about 8.5... 

This paper provides a concise historical perspective of sol-gel abrasive materials, an overview of the synthesis and properties of boehmite, the critical alumina precursor material used in the production of commercial abrasive minerals, a discussion of the conversion of boehmite into abrasive grains and examples of the microstructural control that has been achieved via manipulation of the chemistry of these sol-gel materials. 

Fig. 1. SEM photomicrograph of polished and thermally etched section of Norton SG sol—gel alumina abrasive grain.

Coated abrasives consist of a flexible backing on which films of adhesive hold a coating of abrasive grains. The backing may be paper, cloth, open-mesh cloth, vulcanized fiber (a specially treated cotton rag base paper), or any combination of these materials. The abrasives most generally used are fused aluminum oxide, sol-gel alumina, alnmina-zirconia. silicon carbide, garnet, emeiy, and flint. 

Erikson, D.D., Wood, T.E., and Wood, W.F., Historical development of abrasive grain. Sol-gel processing symposium, Ceram. Trans., 12, 95, 1998. 

Conventional abrasive grains (sdicium carbide (SiC), aluminum oxide or corundum (AI2O3), Sol-Gel corundum)... 

Bange D.E., Erickson D.D., Wood T.E., Wood W.P. Sol-gel products news. 3M cubitron 321 abrasive grain. J. Sol-Gel Sci. Technol. 2000 18 288-289 Bazin N., Andrew J.E., Mcinnes H.A. Comparison of different high and low index materials in the manufacture of high laser damage threshold mirrors at the 351 nm wavelength. J. Sol-Gel Sci. Technol. 1998 13 757-761... 

Schwabel M.G., Kendall P.E. Alumina abrasive grains produced by sol-gel technology. Am. Ceram. Soc. Bull. 1991 70 1596-1598... 

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