Silicon carbide morphology

Fig. I.IB illustrates fibers typical of commercial asbestos, while Fig. l.ll shows Fiberglas and Fig. I.IJ silicon carbide whiskers. Some of the fibers in these examples are bent, occasionally through 180°, indicating considerable flexibility. Whiskers of other compounds can also bend but the tensile strength of these materials is their most remarkable feature. The measured values (Table 1.2) are at least ten times higher than those observed for the same compounds in bulk or in another morphology (Walker and Zoltai, 1979). The numerous investigations into the causes of this unique response have produced several hypotheses.

Subsequent preliminary comparative studies of the behavior of an SiC based layer on Ta, Mo, Ti and steel substrates showed that better mechanical stability was obtained with a coating deposited on tantalum. This element was consequently considered to make PFCVD deposit/interlayer/steel stacks. Tantalum can be produced by physical vapor deposition (PVD), at variable thickness, with reproducible morphology. Note that preparation by chemical vapor deposition with or without plasma assistance (CVD or PECVD) is possible at low temperature but would require an optimization study in order to be compatible with the deposition conditions of the silicon carbide layer, the aim being to increase the mechanical stability. 

Silicon carbide is remarkable for its unusually large variety of different morphologies, which differ in their stacking sequences of hexagonal and rhombohedral layers. All hexagonal and rhombohedral forms are often simply described as a-SiC. The commercially available SiC produced by the Acheson process is a-SiC. 

The bulk chemistries, surface chemistries, and morphologies of silicon carbide whiskers vary widely depending on the type of process used, the stage of the process development, and the postsynthesis treatments practiced by the producer. The synthesis of the whiskers as described earlier is... 

Xu YD, Cheng LF, Zhang LT, Zhou WC(1999) Morphology and growth mechanism of silicon carbide chemical vapor deposited at low temperature and normal atmosphere. J Mater Sci 34 551-55... 

Yue Ke, Y. Shishkin, R.P. Devaty, and W.J. Choyke, Chapter 1 Porous SiC preparation, characterization and morphology , in Porous Silicon Carbide and Gallium Nitride, R.M. Feenstra and C.E.C Wood (Eds), John Wiley Sons, Ltd, Chichester 2008. 

P. Tsui, K. E. Spear, in Emergent Process Methods for High-Technology Ceramics Morphological Study of Silicon Carbide Prepared by Chemical Vapor Deposition, (Eds. by R. F. Davis, H. Palmour, HI, and R. L. Porter), Materials Research 17, 1984, pp. 371-380. 

Hollow silicon carbide (SiC) spheres have been synthesized by a microwave heating and carbothermal reduction method with carbon spheres as template and fly ash (a solid waste from coal-fired power plant) as silica source. X-ray diffraction and scanning electron microscope were employed to characterize the morphology, structure of the products. The results show that hollow spheres prepared at 1300 "C under argon atmosphere have a hollow core and SiC shell structure. The shell of a hollow SiC sphere is composed of a lot of irregular SiC nanowires with 5-20 pm in length and 50-500 nm in diameter which belongs to the p-SiC. Moreover, the formation mechanism of the hollow SiC spheres is also discussed. 

J. Schulte-Fischedick, A. Zem, J. Mayer, M. Riihle, M. FrieB, W. Krenkel and R. Kochendotfer, The Morphology of Silicon Carbide in C/C-SiC Composites, Journal of Material Science and Engineering A. Elsevier Science B.V. (2002), p. 146-152. 

Acheson Furnace. An enclosed electric resistance furnace, of the type first used by Acheson in 1891 to make silicon carbides from carbon and sand, which can attain temperatures of 2500 °C. Acicular. see morphology. 

The morphology of epitaxial graphene/CNT is highly influenced by the underlying SiC structure. The basic building block of a silicon carbide is a tetrahedron with four carbon atoms and a single... 

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