Diborides properties

Uses. In spite of unique properties, there are few commercial appUcations for monolithic shapes of borides. They are used for resistance-heated boats (with boron nitride), for aluminum evaporation, and for sliding electrical contacts. There are a number of potential uses ia the control and handling of molten metals and slags where corrosion and erosion resistance are important. Titanium diboride and zirconium diboride are potential cathodes for the aluminum Hall cells (see Aluminum and aluminum alloys). Lanthanum hexaboride and cerium hexaboride are particularly useful as cathodes ia electronic devices because of their high thermal emissivities, low work functions, and resistance to poisoning. 

Although few applications have so far been found for ceramic matrix composites, they have shown considerable promise for certain military applications, especially in the manufacture of armor for personnel protection and military vehicles. Historically, monolithic ("pure") ceramics such as aluminum oxide (Al203), boron carbide (B4C), silicon carbide (SiC), tungsten carbide (WC), and titanium diboride (TiB2) have been used as basic components of armor systems. Research has now shown that embedding some type of reinforcement, such as silicon boride (SiBg) or silicon carbide (SiC), can improve the mechanical properties of any of these ceramics. 

Aveston, J., Cooper, G.A., Kelly, A. (1971), Single and multiple fracture , in The Properties of Fiber Composites, IPC Science Technology Press, Guildford, UK, 15-22 Bahr, H.A., Weiss, H.J., Maschke, H.G., Meissner, F. (1988), Multiple crack propagation in strip caused by thermal shock , Theor. Appl. Fract. Mech., 10, 219-226. Bannister, M.K., Swain, M.V. (1990), Thermal shock of a titanium diboride based composite , Ceram. Int., 16, 77-83... 

EFFECT OF DISPERSITY AND HIGH PRESSURE SINTERING TEMPERATURE OF TITANIUM DIBORIDE ON ITS PHYSICAL AND MECHANICAL PROPERTIES... 

Titanium diboride is an advanced ceramic material with properties similar to those of metals such as high thermal and electrical conductivity. The other distinguishing features of this material are its excellent oxidation resistance and chemical corrosion resistance at elevated temperatures. It can be used as an abrasive and oxidation protection coating as well as the electrode material in aluminium refining. In addition, like other borides it can also be used as a neutron absorber. 

Titanium diboride exhibits a high melting point, electronic conductivity, wetability by molten aluminum, and a resistance towards chemical attack of aluminum and molten fluorides. Due to these properties, TiB2 is considered to be the most promising material for inert cathodes in aluminum electrolysis. Also zirconium diboride belongs to the category of promising constructive materials due to its favorable properties. 

From the physico-chemical properties of the melts of the system KF-KCl-KBF4-K2T1F6, it follows that the most characteristic feature of these melts is the formation of the thermodynamically less stable ionic species TiFy and TiFeCl " with lowered symmetry of the coordination sphere in the melt. The presence of these anions in the melt facilitates most probably the electro-reduction of titanium and thus the formation of titanium diboride on the cathode. 

Canfield, Paul C., and George W. Crabtree. Magnesium Diboride Better Late than Never. Physics Today 56 (2003) 34. Article describes the history and discovery as well as superconducting properties of magnesium diboride. 

F. Monteverde, A. Bellosi, et al.. Processing and Properties of Zirconium Diboride-based Composites, J. European Ceram. Soc., 22 3, 279-288 (2002). 

F. Monteverde, S. Guicciardi, et al.. Advances in Microstructure and Mechanical Properties of Zirconium Diboride Based Ceramics, Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process., 346(1-21,310-319(2003). 

M. Gasch, D. Ellerby, E. liby, S. Beckman, M. Gusman, and S. Johnson, Processing, Properties and Arc Jet Oxidation of Hafnium Diboride/Silicon Carbide Ultra High Temperature Ceramics, J. Mater. Sci., 39, 5925-5937 (2004). 

P. A. Hoffman, Thermoelastic Properties of Silieon Carbide-Titanium Diboride Particulate Composites, MS Thesis, The Pennsylvania State University, 1992. 

M-J. Pan, Microcracking Behavior of Particulate Titanium Diboride-Silicon Carbide Composites and Its Influence on Elastic Properties, Ph.D. Thesis, The Pennsylvania State University, 1994. 

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