US Patent 7501000 - Alpha alumina nanoparticle abrasive

http://www.freepatentsonline.com/7501000.html

This patent from 3M teaches a new nanostructured abrasive composite. Claim 1 reads:

1. A plurality of abrasive particles having a specified nominal grade, wherein at least a portion of the plurality of abrasive particles comprise a glass-ceramic, the glass-ceramic comprising alpha alumina having an average crystal size not greater than 150 nanometers, wherein the abrasive particles of the portion have a density of at least 90 percent of theoretical density.