Accession Number:

ADA109204

Title:

Processing Research on Chemically Vapor Deposited Silicon Nitride

Descriptive Note:

Final technical rept. 1 Jun 80-31 Oct 81 on Phase 3

Corporate Author:

GENERAL ELECTRIC CO PHILADELPHIA PA RE-ENTRY SYSTEMS DEPT

Report Date:

1981-12-01

Pagination or Media Count:

129.0

Abstract:

The feasibility of preparing free standing plate and hemispherical domes of crystalline silicon nitride by the chemical vapor deposition CVD technique has been established as a result of processing research conducted on this program. Physical property characterizations of a wide range of deposits have established the CVD form of silicon nitride as a candidate electromagnetic EM window material for advanced, high-performance tactical missile systems. The EM absorption coefficients of CVD silicon nitride in the UV-IR and radar transmittance passbands are far superior to the more conventional silicon nitride modifications i.e. HPSN and RSSN. At the current stage of process development, the flexure strength is comparable to RSSN exhibiting similar strength retention properties at elevated temperatures. Average room temperature flexure strength levels of 317 MNsq m 46,000 psi were achieved by codeposition with minor amounts of aluminum chloride during this program Phase 3 this level represents a 150 percent increase in strength compared to levels achieved during the initial Phase 1 program. With a better understood deposition model now in hand, as a result of the Phase 3 program, a high probability exists in future process optimization studies for achieving additional improvements in the mechanical and optical properties of CVD alpha-silicon nitride.

Subject Categories:

  • Ceramics, Refractories and Glass
  • Guided Missiles
  • Ultraviolet Detection and Detectors
  • Active and Passive Radar Detection and Equipment

Distribution Statement:

APPROVED FOR PUBLIC RELEASE