Thermodynamic and Diffusivity Measurements in Potential Ultra High TemperatureComposite Materials

摘要

The study of the vaporization kinetics of CaZrO3 and BaZrO3 have been carried outin the temperature range 1600-2000 C using a vacuum microbalance technique. Oxygen tracer diffusion coefficients in CaZrO3, BaZrO3 and SrZrO3 have also been measured using the gas exchange technique. Tracer concentration profiles were determined using nuclear reaction analysis. Both CaZrO3 and BaZrO3 have a relatively high rate of evaporation at high temperatures. However, dry-pressed CaZrO3 shows a smaller rate of evaporation than hot-pressed but impure BaZrO3. Results of the diffusion experiments indicate that CaZrO3 exhibits the largest penetration with BaZrO3 showing the smallest. Apparent oxygen tracer diffusion coefficients were measured for CaZrO3 and SrZrO3 at 1000C. Over the temperature range of 900-1100C, the apparent oxygen tracer diffusion coefficient in BaZrO3 is described by D=5.0 x 10-3 sq.cm/sec exp (-247 KJ/mole/RT). Calcium Zirconate, Barium Zirconate, Strontium Zirconate.