Babenkov E. Electrochemical behaviour of niobium in low-temperature carbamide-containing melts

The dissertation is devoted to studying the processes taking place under electrolyze of carbamide-containing melt and studying the electrochemical behaviour of niobium in these melts. It was defined the peculiarities of electrochemical behaviour of mixed ion-organic melts and their influence on electrochemical properties of niobium in the melts based on carbamide. The main characteristic of Nb behaviour is the strong passivation of metal surface in carbamide and its mixtures with ionic salts. The defining of depassivation conditions of Nb surface in different compositions of melts make possible to realize the Nb electrochemical dissolution with forming of the halogenide complexes of metal ion in high degree of oxidation Nb(V) in all melts, type [NbHal6]-. The reduction of Nb(V) complexes take place, but only to formation the complexes of Nb(IV) in melt. That is impossible to obtain the cathodic deposit in these conditions. The Nb ability to passivation allows to developing the method of Nb electropolishing in carbamide-chloride melt.