MATERIAL TRANSPORT DURING SINTERING OF FLUORITE STRUCTURE MATERIALS
The sintering rate of thoria powder compacts and of compacts of other fluorite structure materials was investigated during the initial period of rapid densification. The densification rate, determined as a function of temperature with temperature increasing at controlled rates, increased to a maximum, decreased to a minimum, and then rose again. Except under extreme conditions, compacts brought to temperature had a temperature-dependent density despite variations in the heat-up cycle. When the sintering temperature of ThO/sub 2/ was raised, the increase in densification rate was much greater than the corresponding increase in the diffusion coefficient of thorium, the slower diffusing species, indicating that bulk diffusion is not the dominant material transport mechanism. The densification behavior was compatible with transport of material by dislocation movement. Prolonged holding at an intermediate temperature before heating to the final sintering temperature resulted in a curtailment of the densification, suggesting the operation of two or more transport mechanisms which are not contributing to sintering in the same manner. (auth)
- Research Organization:
- Oak Ridge National Lab., Tenn.
- DOE Contract Number:
- W-7405-ENG-26
- NSA Number:
- NSA-17-032535
- OSTI ID:
- 4679283
- Report Number(s):
- CONF-50-15
- Country of Publication:
- United States
- Language:
- English
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