Refractories boride-based

In some cases, several refractory compounds can result from two or more parallel reactions occurring simultaneously in the combustion wave. A typical example of this type is the Ti-C-B system, where both the Ti+C and Ti-I-2B reactions affect the combustion synthesis and structure formation processes (Shcherbakov and Pityulin, 1983). By adjusting the contents of carbon and boron powders in the reactant mixture, either carbide- or boride-based ceramics can be obtained. 

The highest melting points of all the known compounds are exhibited by carbides, nitrides, borides and oxides. Since the first three groups of substances are unstable in an oxidizing atmosphere at high temperatures, most industrial refractories are based on oxides. 

The two dominating design variables to be considered Borides and boride-based high-temperature refractories for high-temperature materials are hardness and thermal are treated extensively in [2.2,3,10]. Some properties conductivity as a function of temperature. Figure 3.2-2 are listed in Table 3.2-19. 

Table 3.2-19 Physical properties of borides and boride-based high-temperature refractories [2.4]...

J.J. Melendez-Martfnez, A. Dominguez-Rodn guez, F. Monteverde, C. Melandri and G. De Portu Characterisation and high temperature mechanical properties of zirconium boride-based materials. Journal of the European Ceramic Society 22, 2543-2549 (2002). W.G. Fahrenholtz, G.E. Hilmas, I.G. Talmy and J.A. Zaykoski Refractory diborides of zirconium and hafnium. Journal of the American Ceramic Society 90, 1347-1364 (2007). 

J Etourneau, JP Mercurio, P Hagenmuller. Compounds based on octahedral B units, hexaborides and tetraborides. In VN Matkovich, ed. Boron and Refractory Borides. Berlin Springer, 1977, p 115. 

Bellosi, A., Guicciardi, S., Medri, V., Monteverde, F., Sciti, D., Silvestroni, L. (2011). Processing and Properties of Ultra-Refractory Composites Based onZr- and Hf-Borides State of the Art and Perspectives. In Orlovskaya, N., Lugovy, M. (Eds.), Boron Rich Solids. Sensors, Ultra High Temperature Ceramics, Thermoelectrics, Armor Series NATO Science for Peace and Security Series B Physics and Biophysics (pp. 147-160). Springer. 

Next to Cr C2, TiC is the principal component for heat and oxidation-resistant cemented carbides. TiC-based boats, containing aluminum nitride, AIN, boron nitride, BN, and titanium boride, TiB2, have been found satisfactory for the evaporation of metals (see Boron compounds, refractory boron compounds Nitrides). 

Although the results obtained can be considered as approximate rather than accurate, they give some information about the relative strength of oxocompounds of the Group VIb elements. Nevertheless, these results were used as initial data for the development of the processes of reduction of these oxocompounds in chloride melts [150-152]. Theoretical bases and principles for monitoring the electrochemical processes of deposition of the free refractory metals and their compounds with some non-metals (carbides, borides, silicides, etc.) from molten ionic media [153] were developed. 

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