The nano and submicron ultrafine spherical alumina and silica powders produced by SRP using the direct combustion method feature controllable particle sizes ranging from 0.1 μm to 10 μm. These powders possess 100% particle sphericity, no agglomeration, excellent dispersibility, and uniform particle size distribution. The products have low impurity content, especially extremely low levels of alkali metal ions such as sodium and potassium, with all series products below 20 ppm...