Chemical vapour deposition of boron carbides II: Morphology and microstructure
1989; Elsevier BV; Volume: 172; Issue: 1 Linguagem: Inglês
10.1016/0040-6090(89)90121-1
ISSN1879-2731
AutoresM. Olsson, Staffan Söderberg, Bengt Stridh, Ulf Jansson, J.‐O. Carlsson,
Tópico(s)Diamond and Carbon-based Materials Research
ResumoThe morphology of boron carbide films prepared by chemical vapour deposition (CVD) on α-rhombohedral boron substrates has been investigated. In addition to the stable rhombohedral boron carbide (stoichiometric composition B13C2), metastable orthorhombic and tetragonal phases were obtained. Two types (I and II) of B13C2 could be distinguished with respect to morphology and, also, to the observed broadening of the X-ray diffraction lines. The observed morphologies have been related to previously obtained deposition diagrams. A detailed microstructural characterization of the type I and type II B13C2 has been performed using transmission electron microscopy. A complex, highly strained microstructure, characterized by a needle-like contrast along the (001) planes of the rhombohedral unit cell, is observed for both carbide types. There is a characteristic variation in grain size with film thickness, and three growth zones have been defined. The type II carbide is characterized by a finer grain size in the outer zone and a more heavily strained lattice as compared with the type I carbide. The growth structure indicates that both carbide types were initially deposited as a metastable phase, followed by a solid state transformation.
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