THORIUM OXIDE - DIFFUSION OF OXYGEN, COMPATIBILITY WITH BORIDES, AND FEASIBILITY OF COATING BORIDES BY PYROHYDROLYSIS OF METAL HALIDES
Rept. for Apr 1962-June 1963
GENERAL ELECTRIC CO CINCINNATI OH
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Measurements of self-diffusion of oxygen in ThO2 were complicated by slow exchange at the surface. The measured values of the diffusion coefficient, D, range from1.8 x 10 to the -13tpower sq cmsec at 800 C to 3.5 x 10 to the - 8th power sq cmsec at 1500 C. The rate constant of the surface reaction, K, ranged from 6.8 x 10 to the -10th power sq cmsec at 800 C to 1.3 x -10th power sq cmsec at 1500 C. Attempts to deposit dense impervious layers of ThO2 on selected solid borides by pyrohydrolysis of ThCl4 were es sentially unsuccessful. Commercially available boride samples which were tested reacted with ThO2 at temperatures in the range 2400 to 2600 C. The boride samples also reacted with graphite in the temperature range of 2400 to 2700 C. Be cause of these reactions, a graphite-boride thoria system will be useful for only limited times at temperatures above 2400 C.
- Inorganic Chemistry