A Model for the Oxidation of ZrB2, HfB2 and TiB2 (Postprint)
Abstract
A mechanistic model that interprets the oxidation behavior of the diborides of Zr, Hf and Ti in the temperature range of ~1000-1800 deg C was formulated. Available thermodynamic data and literature data for vapor pressures and diffusivities were used to evaluate the model. Good correspondence was obtained between theory and experiments for weight gain, recession and scale thickness as functions of temperature and oxygen partial pressure. At temperatures below about 1400 deg C, the rate-limiting step is the diffusion of dissolved oxygen through a film of liquid boria in capillaries at the base of the oxidation product. At higher temperatures, the boria is lost by evaporation, and the oxidation rate is limited by Knudsen diffusion of molecular oxygen through the capillaries between nearly columnar blocks of the oxide, MO2.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 2007
- Accession Number
- ADA519243
Entities
People
- M. Opeka
- R. A. Rapp
- R. J. Kerans
- Triplicane A. Parthasarathy
Organizations
- Universal Energy Systems