Boride composites

The deposition of either niobium or tantalum boride by CVD is difficult to accomplish, when compared with other binary metal boride compositions. In early attempts a reaction mixture containing the metal and boron halides and Hi was used as a precursor stream. However, this reaction frequently leads to the formation of a deposit which had undergone phase separation into fractions consisting of elemental metal and boron, rather than the metal boride. The reaction only produced metal boride if very low flow rates (< 0.4 mis ) were selected [243]. Alternatively, the thermal decomposition of BBr3 and MBrs (M = Nb, Ta) has been used to deposit NbBi andTaB2 [244]. However, this reaction requires temperatures in excess 1500°C. Mixtures of tantalum pentachloride, TaCIs, and diborane, B2H6, decompose at 500-900°C to yield TaB2 films [245]. 

D. Brodkin, S. R. Kalidindi, M. W. Barsoum and A. Zavaliangos. Microstructural Evolution during Transient Plastic Phase Processing of Titanium Carbide-Titanium Boride Composites, J. Am. Ceram, Soc.,19,1945-49(1996)... 

Gidikova, N., Kovacheva, R., 1996. Titanium- and molybdenum-boride composite coatings on steel. Prakt. Metallogr. 33, 154. 

Brodkin, D., Zavaliangos, A., Kalidindi, S. R., Barsoum, M. W. (1999). Ambient- and high-temperature properties of titanium carbide-titanium boride composites fabricated by transient plastic phase processing. Journal of the American Ceramic Society, 82, 665-672. doi 10.1111/j.ll51-2916.1999.tb01815.x. 

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