STATISTICS OF TIO2 CRYSTAL-GROWTH IN AIR ON A METALLIC SURFACE HEATEDAT TEMPERATURES IN THE RANGE OF 900-1100-DEGREES-C

Samples of titanium oxidized in air at temperatures between 900 and 11 00 degrees C were examined by scanning electron microscopy. The crysta l length and width were manually measured. A simple theoretical model that assumes the crystal growth as a time-continuous Markov process wa s developed. A Fokker-Planck equation for the crystal size probability distribution was derived. Its solution is a Weibull-Gnedenko distribu tion. By fitting this distribution to the experimental data some kinet ic parameters were evaluated quantitatively. A nearly linear kinetic l aw (below 1000 degrees C) and a fourth-order law (above 1000 degrees C ) were identified.