Vapor deposition of binary boron--carbon phases at substrate temperatures of 900 to 1800$sup 0$C. II. Rhombohedral boron carbide

Journal Article · Fri Mar 01 04:00:00 EDT 1974 · J. Less-Common Metals, v. 35, no. 1, pp. 131-145

OSTI ID:4350945

Ploog, K

Crystals of rhombohedral boron carbide of composition B/sub 13/C/sub 2/ to B/sub 13/C/sub 3/ were prepared by cheinical vapor deposition on to Ta and BN substrates at 900-- 1800 deg C. Systematic preparative and structural investigations led to the conclusion that only the boronrich boron carbide B/sub 13/C/sub 2/ with a carbon content of 14.6 wt% exists in a completely ordered structure and can be prepared with a satisfactory stoichiometry. This more stable rhombohedral boron carbide has the crystal chemical composition B/sub 12/ CBC, i.e. its structural units are B/sub 12/ icosahedra and linear CBC chains. The incorporation of carbon into the B/sub 13/C/sub 2/ lattice only occurs up to a composition corresponding to B/sub 13/C/sub 3/ (20.4 wt% C). The B/sub 4/C compound with a carbon content of 21.7 wt% was never formed. In all boron carbide products containing more than 21 wt% C, the free carbon was present as graphite. (8 figures) (auth)

• Research Organization: Univ., Munich
• NSA Number: NSA-29-021332
• OSTI ID: 4350945
• Journal Information: J. Less-Common Metals, v. 35, no. 1, pp. 131-145, Journal Name: J. Less-Common Metals, v. 35, no. 1, pp. 131-145; ISSN JCOMA
• Country of Publication: Country unknown/Code not available
• Language: German

Related Subjects

*BORON CARBIDES-- CHEMICAL VAPOR DEPOSITION TANTALUM
BORON NITRIDES-- CRYSTAL STRUCTURE-- SUBSTRATES-- TRIGONAL LATTICES
N50120* --Metals
Ceramics
& Other Materials--Ceramics & Cermets--Preparation & Fabrication