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Open AccessReport10.2172/6943439

Characterization of SiC coatings on HTGR fuel particles. Final report

Robert J Lauf,D. N. Braski-1981-01-01
6

TL;DRAbstract

Fuel particles for the HTGR contain a layer of pyrolytic silicon carbide to act as a pressure vessel and fission product barrier. The SiC is deposited by thermal decomposition of methyltrichlorosilane (CH/sub 3/SiCl/sub 3/ or MTS) in an excess of hydrogen. Coatings deposited at temperatures from 1500 to 1700/sup 0/C and coating rates from 0.4 to 1.2 ..mu..m/min have been studied by transmission electron microscopy, small-angle x-ray scattering, x-ray diffraction, optical microscopy, density measurements, scanning electron microscopy, and microhardness measurements. Transmission electron microscopy has the necessary resolution to provide crystallographic information on small coating defects. Major defects were voids, stacking faults, and dislocations. Small-angle x-ray scattering was used to measure the void size distribution; voids were generally from 20 to 80 nm in diameter. X-ray diffraction indicates that SiC coatings are predominantly cubic ..beta..-SiC. However, the high stacking

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Fuel particles for the HTGR contain a layer of pyrolytic silicon carbide to act as a pressure vessel and fission product barrier. The SiC is deposited by thermal decomposition of methyltrichlorosilane (CH/sub 3/SiCl/sub 3/ or MTS) in an excess of hydrogen. Coatings deposited at temperatures from 1500 to 1700/sup 0/C and coating rates from 0.4 to 1.2 ..mu..m/min have been studied by transmission electron microscopy, small-angle x-ray scattering, x-ray diffraction, optical microscopy, density measurements, scanning electron microscopy, and microhardness measurements. Transmission electron microscopy has the necessary resolution to provide crystallographic information on small coating defects. Major defects were voids, stacking faults, and dislocations. Small-angle x-ray scattering was used to measure the void size distribution; voids were generally from 20 to 80 nm in diameter. X-ray diffraction indicates that SiC coatings are predominantly cubic ..beta..-SiC. However, the high stacking

Keywords

Materials scienceTransmission electron microscopyScanning electron microscopeCoatingPyrolytic carbonCrystallographyDiffractionComposite material

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