Effects of irradiation and post-irradiation annealing on the thermal conductivity/diffusivity of monolithic SiC and f-SiC/SiC composites
Laser flash thermal diffusivity measurements were made on high-purity monolithic CVD-SiC and 2D f-SiC(Hi-Nicalon)/ICVI-SiC composite samples before and after irradiation (250 to 800C, 4-8 dpa-SiC) and after post-irradiation annealing composite samples to 1200C. For irradiated CVD-SiC, the defect concentrations at saturation were estimated to range from 25,300 appm (250C) down to 940 appm (800C). The transverse thermal conductivity ratios after-to-before irradiation (Kir/Ko) determined at the irradiation temperatures were: 0.044 up to 0.12 (250 up to 800C) for irradiated CVD-SiC and 0.18 up to 0.29 (330 up to 800C) for the irradiated Hi-Nicalon composite. Analysis of thermal diffusivity values for the Hi-Nicalon composite measured in air, argon, helium and vacuum indicated that thermal conductivity degradation occurred primarily due to point defect accumulation in the matrix component. After annealing to 1200C and cooling to the irradiation temperature, fiber/matrix debonding occurred due to net shrinkage in the fiber and PyC interface components.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 902054
- Report Number(s):
- PNNL-SA-40772; AT6020100
- Country of Publication:
- United States
- Language:
- English
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