Melting zirconium/titanium borides

Borides are inert toward nonoxidizing acids however, a few, such as Be2B and MgB2, react with aqueous acids to form boron hydrides. Most borides dissolve in oxidizing acids such as nitric or hot sulfuric acid and they ate also readily attacked by hot alkaline salt melts or fused alkaU peroxides, forming the mote stable borates. In dry air, where a protective oxide film can be preserved, borides ate relatively resistant to oxidation. For example, the borides of vanadium, niobium, tantalum, molybdenum, and tungsten do not oxidize appreciably in air up to temperatures of 1000—1200°C. Zirconium and titanium borides ate fairly resistant up to 1400°C. Engineering and other properties of refractory metal borides have been summarized (1). 

Borides of vanadium, titanium, zirconium, and chromium were produced in thermal plasma by interaction of their melts with boron hydrides (BH3, B2H6) ... 

Taranenko, V.I., Zarutskii, I.V., Bidenko, V.A., and Devyatkin, S. V. (1991) Electrochemical synthesis of titanium and zirconium diborides from chloro-fluoride melts, in Borides (in Russian), IPM AN UkrSSR, Kiev 55-61. 

Advancing in this direction, we studied the possibility of synthesising carbides, borides and silicides of titanium, zirconium, niobium and tantalum in Li-LiCl and Ca-CaCl2 ionic-electronic melts. These melts are referred to as the ionic-electronic ones, because dissolved lithium and calcium dissociate to cations and delocalized electrons ... 

Electrochemical synthesis in melts is one of several promising methods of producing refractoiy metal borides. To develop this method one needs to be aware of the mechanism of the processes occurring both in the melt bulk and on the surface of electrodes. The evidence available is mainly concerned with production of titanium and zirconium borides. The data on electrochemical synthesis of tantalum borides are contradictory and limited by the area of chloride-fluoride melts [1-5]. 

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