Accession Number : ADA188154

Title :   High Yield Synthesis of B4C/BN Ceramic Materials by Pyrolysis of Polymeric Lewis Base Adducts of Decaborane(14).

Descriptive Note : Technical rept.,

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY

Personal Author(s) : Rees, William S , Jr ; Seyferth, Dietmar

PDF Url : ADA188154

Report Date : 04 Nov 1987

Pagination or Media Count : 20

Abstract : In previous work, we have developed useful polymeric precursors whose pyrolysis provides high yields of silicon nitride or silicon nitride/silicon carbide blends. The main applications of such preceramic polymers (preparation of ceramic fibers and coatings and their use as binders for ceramic powders) require that the polymeric precursor be processable, i.e., soluble in organic solvents and or fusible. Although the major efforts of workers in the preceramic polymer area have, to date, been directed toward the development of useful precursors for silicon carbide, silicon nitride, silicon carbonitride and silicon oxynitride, boron containing ceramics (the carbide, nitride, phosphides, silicides and others) are class of ceramic materials whose properties are very attractive in terms of high technology applications. Thus boron carbide has exceptional thermal stability (mp 2450 C), a microhardness of 4.05 GPa (vs 2.53 GPa for SiC), high compressive strength and radiation stability. Various routes exist for the preparation of boron carbide and boron nitride. For boron carbide, however, none of these proceed by way of a processable intermediate. For boron nitride, preparative routes based on the pyrolysis of silicon substituted, oligomeric borazines and of a boric acid/1,2,3-propanetriol condensation product have been reported. We report the results of our initial efforts to develop processible polymeric precursors whose pyrolysis gives boron-containing ceramic materials in high yield. The initial objective of our research was the preparation and evaluation of polymers which would serve as precursors for boron carbide or blends of boron carbide and boron nitride.

Descriptors :   *BORON, *BORON CARBIDES, *CARBIDES, *CERAMIC MATERIALS, *POLYMERS, *PYROLYSIS, BINDERS, BORON NITRIDES, CERAMIC FIBERS, COATINGS, COMPRESSIVE PROPERTIES, HIGH RATE, HIGH STRENGTH, NITRIDES, ORGANIC SOLVENTS, PHOSPHIDES, POWDERS, PRECURSORS, PREPARATION, RADIATION, SILICIDES, SILICON, SILICON CARBIDES, SILICON COMPOUNDS, SILICON NITRIDES, STABILITY, STRENGTH(MECHANICS), SYNTHESIS, THERMAL STABILITY, YIELD

Subject Categories : Polymer Chemistry
      Ceramics, Refractories and Glass

Distribution Statement : APPROVED FOR PUBLIC RELEASE