Zirconium diboride

Borides. Zirconium forms two borides zirconium diboride [12045-64-6] ZrB2, and zirconium dodecaboride [12046-91 -2] The diboride... 

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. 

Fibrous growth of ZrBj occurs under a.c. discharge at 0.5-1 mA, the growth being accelerated by argon addition. Zirconium diboride fibers with a diameter of 9 Lim are obtained ". 

Most borides are chemically inert in bulk form, which has led to industrial applications as engineering materials, principally at high temperature. The transition metal borides display a considerable resistance to oxidation in air. A few examples of applications are given here. Titanium and zirconium diborides, alone or in admixture with chromium diboride, can endure temperatures of 1500 to 1700 K without extensive attack. In this case, a surface layer of the parent oxides is formed at a relatively low temperature, which prevents further oxidation up to temperatures where the volatility of boron oxide becomes appreciable. In other cases the oxidation is retarded by the formation of some other type of protective layer, for instance, a chromium borate. This behavior is favorable and in contrast to that of the refractory carbides and nitrides, which form gaseous products (carbon oxides and nitrogen) in air at high temperatures. Boron carbide is less resistant to oxidation than the metallic borides. 

A. C. Switendick, Electronic Stmcture and Charge Density of Zirconium Diboride, in Boron-rich Solids , eds. D. Emin,... 

Eoex 21) reports the successful formation of borides in a rotating batch melting furnace, fired by an RE induction plasma. An amount of 0.8 kg from a stoichiometric mixture of Zr02 and boron, previously compressed in the rotating vessel to a pressure of 40 kg/cm, is treated by the action of an argon plasma (1 m /hr) for 0.5 hr. Zirconium diboride is formed by the reaction,... 

Borides. Zirconium forms two borides zirconium diboride [12045-64-6] ZrB2, and zirconium dodecabotide [12046-91 -2] ZtB 2- Th diboride is synthesized from the elements, by vapor-phase coreduction of zirconium and boron hahdes, or by the carbothermic reduction of zirconium oxide and boron carbide boric oxide is avoided because of its relatively high vapor pressure at the reaction temperature. 

B. Zirconium Diboride-Reinforced Zirconium Carbide Composites. 93... 

More recently, ceramic composite materials have been described that incorporate zirconium diboride platelet reinforcements in a zirconium carbide matrix [34, 35], These materials are prepared by the directed reaction of molten zirconium with boron carbide (B4C) to form a ceramic material composed of zirconium diboride platelets in a zirconium carbide matrix with a controlled amount of residual zirconium metal. 

Fig. 4. A schematic illustration of the processing used to produce zirconium diboride reinforced zirconium carbide materials by directed metal oxidation.

Fig. 5. The microstructure of zirconium diboride-reinforced zirconium carbide composites produced by directed metal oxidation, (a) A composite prepared with 22 vol % metal, (b) A composite produced with less than 2 vol % metal. 

The kinetics of formation of this zirconium diboride platelet reinforced zirconium carbide have been discussed, as have possible formation mechanisms [36] and detailed microstructural and orientation relationships between the phases [37]. These materials, in addition to being very refractory, are quite hard. Potential applications typically involve wear resistance, either at low to moderate temperatures or for short times at very high temperatures, such as in biomedical and rocket nozzle or rocket motor application [35]. 

However, among all of the above mentioned compounds, the technologically most important are the K2TiF6 and K2ZrF6, because of their frequent use in the electrochemical deposition of titanium and zirconium and the electrochemical synthesis of titanium and zirconium diborides. 

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. 

Huang. T.. et al.. Dispersion of zirconium diboride in an aqueous, high-solids paste, Int. J. Appl. Ceram. Technol., 4, 470, 2007. 

EINECS 234-963-5 Zirconium boride Zirconium boride (ZrB2) Zirconium diboride Zirconium diboride (ZrB2). Refractory for aircraft and rocket applications, thermocouple protection tubes, high-temp, electrical conductor, cutting-tool component, coating tantalum, cathode in high-temp, electrochemical systems oxidation-resistant composites. Atomergic Chemetals Cerac Noah Cham. 

Zirconium and hafnium diboride have been studied less extensively. Zirconium diboride potentially is useful as a coating for solar absorbers [242]. These compositions can be prepared either by hydrogen co-reduction of the metal and boron halides [242], or by the decomposition of the metal tetrakis(tetrahydroborates) M(BH4)4 [241]. 

ZS-7. [Advanced Refractory Tech.] Zirconium diboride for oxidation-resistant ctxnposites, burble absorber of neutrons, elec, contacts, mdten metal crucibles, refractory roughener, cutting tool composites, structural ceramics, wear conqxxients, metal matrix omi-posites. 

Y2Zr207 DIYTTRIUM DIZIRCONIUM HEPTAOXIDE 1822 ZrB2 ZIRCONIUM DIBORIDE 1854... 

These authors studied the heats of formation of zirconium diboride and dioxide at... 

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). 

F. Monteverde and A. Bellosi, Effect of the Addition of Silicon Nitride on Sintering Behaviour and Microstructure of Zirconium Diboride, Scr. Mater., 46(3], 223-228 (2002). 

S.C. Zhang, GE. Hilmas, et al.. Pressureless Densification of Zirconium Diboride with Boron Carbide Additions, J. zlm. Ceram. Soc., 89 5, 1544-1550(2006). 

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