Accession Number : ADA183442

Title :   Silicon Nitride Ceramic Fibers from Preceramic Polymers.

Descriptive Note : Technical rept.,

Corporate Author : SRI INTERNATIONAL MENLO PARK CA

Personal Author(s) : Laine,Richard M ; Blum,Yigal D ; Chow,Andrea ; Schwartz,Kenneth S

PDF Url : ADA183442

Report Date : Jun 1987

Pagination or Media Count : 21

Abstract : The program objectives are to develop: (1) Transition metal catalyzed synthetic routes to designed, tractable silicon nitride (Si3N4) preceramic polymers (polysilazanes) based on SRI developed technology; (2) Methods of spinning the resultant polysilazanes into continuous preceramic fibers; and, (3) Pyrolysis techniques for transforming the preceramic fibers into high strength Si3N4 and silicon carbide nitride (SiCN) fibers. In the past year, we have learned to prepare polysilazanes driven from precursors of the type-?H2SiNMe whose viscoelastic properties can be carefully controlled by type of catalyst and/or reaction conditions. This control has permitted us to draw preceramic fibers of diameters as small as 10 um as seen in the attached photographs. Furthermore, we have developed pyrolysis methodology that permits us to obtain ceramic yields of 50-70% with Si3N4 purities ranging from 80-99%. We have discovered that polymer molecular weight greatly influences the ceramic yield but only monomer design or pyrolysis under a reactive atmosphere seems to influence selectivity to specific ceramic products as shown in the attached Table.

Descriptors :   *POLYMERS, *SILICON NITRIDES, *CERAMIC MATERIALS, *CERAMIC FIBERS, SILICON CARBIDES, SYNTHESIS(CHEMISTRY), PRECURSORS, CATALYSTS, CERAMIC MATERIALS, DIAMETERS, FIBERS, METHODOLOGY, MOLECULAR WEIGHT, MONOMERS, POLYMERS, PYROLYSIS, TABLES(DATA), TRANSITION METALS, VISCOELASTICITY, YIELD

Subject Categories : Organic Chemistry
      Ceramics, Refractories and Glass

Distribution Statement : APPROVED FOR PUBLIC RELEASE