Transition metal boride ceramics

Pierson, H., A Survey of the Chemical Vapor Deposition of Refractory Transition Metal Borides, in Chemical Vapor Deposited Coatings, pp. 27-45, Am. Ceram. Soc. (1981)... 

These approaches also have the potential of being able to synthesize ceramic-ceramic composites containing transition metal borides or silicides and carbides [54]. 

With the more interesting in the UHTCs, transition metal borides have received much attention and quickly become one of the hottest research topics in recent years. Although the wetting experiments conducted on borides, predominantly on ZrB and HfB, are hmited in the past ten years, they are important to explore and extend the potential applications of the boride-based ceramic by means of joining, such as diffusion bonding and brazing method. 

Recently, there has also been an increase in the importance of melts in their use as a reaction medium for chemical and electrochemical synthesis of compounds for functional and construction ceramics, e.g. double oxides with spinellitic and perowskite structure and binary compounds with prevailing covalent bond character, mainly borides and carbides of transition metals. 

Interest in new compositions and new synthetic routes in the context of catalysis is growing, and recent examples of the synthesis and use of non-oxidic, ceramic compositions in catalysis include SiC as a support for Ni or Pt in CO hydrogenation (2), SiC as a support for Co and Mo for thiophene hydrodesulphurisation (3), transition metal (Ti, Ta, Mo or W) carbides for methanol decomposition (4), early transition metal carbides, nitrides or borides for hydrodenitrogenation of quinoline (5), and the synthesis of high surface area molybdenum carbide (6). 

Fligh-temperature equilibria of the extraordinarily hard borides with metallic melts bring about the opportunity for a pressureless liquid phase sintering and the fabrication of hard and simultaneously tough composites similar to hard metals but are also of interest in ceramic systems or coatings. In this section emphasis is put on binary and ternary borides which are in equilibrium with transition metals. 

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