Tantalum boride

Borides. NbBj has been obtained from BBrj and NbBrg, and from NbClj, BCI3 and a Hj-Ar mixture. Above 1473 K, the NbB2 reacts with the quartz substrate to give NbgSia. TaB2 can also be made from the bromide. Calculations have been made of the optimum conditions for the chemical vapour deposition of niobium and tantalum borides. There has been a redetermination of the structure of NbCoB2. °... 

The deposition of either niobium or tantalum boride by CVD is difficult to accomplish, when compared with other binary metal boride compositions. In early attempts a reaction mixture containing the metal and boron halides and Hi was used as a precursor stream. However, this reaction frequently leads to the formation of a deposit which had undergone phase separation into fractions consisting of elemental metal and boron, rather than the metal boride. The reaction only produced metal boride if very low flow rates (< 0.4 mis ) were selected [243]. Alternatively, the thermal decomposition of BBr3 and MBrs (M = Nb, Ta) has been used to deposit NbBi andTaB2 [244]. However, this reaction requires temperatures in excess 1500°C. Mixtures of tantalum pentachloride, TaCIs, and diborane, B2H6, decompose at 500-900°C to yield TaB2 films [245]. 

High Performance Coating of Steel with Tantalum Boride Layers... 

Tab 5 chemical attack test of tantalum and tantalum-boride... 

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]. 

Kuznetsov, S.A., Glagolevskaya, A.L., and Belyaevskii, A.T. (1994) Electrochemical preparation of tantalum boride coatings in salt melts, Zh. PriklKhim. (Russ). 67,1093-1099. 

Mechanical properties of tantalum boride layers 24 Mechanism of molybdenum electrodeposition 186... 

---