Dimensional stability of bare and coated reaction-bonded silicon carbide

Matthew B. Magida; Roger A. Paquin; James J. Richmond

doi:10.1117/12.22877

1 November 1990 Dimensional stability of bare and coated reaction-bonded silicon carbide

Matthew B. Magida, Roger A. Paquin, James J. Richmond

Proceedings Volume 1335, Dimensional Stability; (1990) https://doi.org/10.1117/12.22877
Event: 34th Annual International Technical Symposium on Optical and Optoelectronic Applied Science and Engineering, 1990, San Diego, CA, United States

Abstract

Reaction bonded silicon carbide (RB SiC) is a two phase mirror material which is readily formable to near-net-shape but can be difficult to polish to a high quality optical surface. The usual solution is the addition of a thick layer of silicon (Si) which may be polished to very high optical quality but which may have a thermal distortion problem due to the mismatch in thermal expansion of the two materials. The second solution is the application of a thick layer of chemically vapor deposited (CVD) SiC which can be polished to high quality but not as readily as the Si. The CVD SiC can also have a mismatch since it is deposited at high temperature and is beta SiC compared to the alpha in the substrate. We have chosen to develop a low temperature method for depositing amorphous SiC which should provide both a polishable surface and a better match of properties. To determine the levels of thermally induced distortion in SiC mirrors we have cryogenically tested 6-inch diameter spherical RB SiC mirrors bare and with polished coatings of amorphous SiC Si and CVD SiC. Results from this program are presented which show that all but the CVD SiC coated mirror are thermally stable. 1.

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Matthew B. Magida, Roger A. Paquin, and James J. Richmond "Dimensional stability of bare and coated reaction-bonded silicon carbide", Proc. SPIE 1335, Dimensional Stability, (1 November 1990); https://doi.org/10.1117/12.22877

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