A study of the reaction pathways during electrochemical reduction of dense Nb2O5 pellets in molten CaCl2 medium

Corrosion of high density graphite anodes during direct electrochemical de-oxidation of solid oxides in molten CaCl2 medium

“…5 that substantial corrosion of the graphite anode and hence mass loss did occur even after the 45 h period of electrolysis. This typical corrosion behaviour of anode was observed in our previous study too [36]. The discussion brings to the fore the possibility of graphite corrosion and mass loss by process/es other than reaction (2).…”

“…Electrolysis experiments were carried out with Nb 2 O 5 pellet as the cathode at a cell voltage of 3.1 V for different periods of time (2,9,22,26,35,44 and 56 h) during which the graphite rods were dipped into the melt up to a length of about 3.6 cm (area $ 12.09 cm 2 ). It was observed in our earlier studies with similar Nb 2 O 5 pellets that it is necessary to electrolyse the pellet for about 44 h or more for complete conversion to the Nb metal [36]. It was also confirmed in these studies that the transformation of the oxide pellet to metal takes place through in-situ formation and decomposition of different chemical phases involving Ca, Nb and O and these phase changes are often indicated by the discontinuities in the electrolysis (I-t) curves.…”

“…Powder compacted and sintered Nb 2 O 5 pellets were used as the cathodes in the electro-reduction cell. The procedure adopted for the preparation of the pellets and the cathode assembly have been discussed in detail in our previous publication on the electro-reduction of Nb 2 O 5 [36]. An alumina crucible containing the salt was placed in a high temperature molten salt reactor whose top flange was equipped with provisions for insertion of electrodes in a leak-tight manner into the liquid salt during electrolysis.…”

Difference in the Mechanism of Electrochemical Deoxidation of Conducting and Non-conducting Solid Oxide Preforms: An Experimental Demonstration with TiO2 and SiO2 Pellet Electrodes in CaCl2 Melt

“…Moisture-free CaCl 2 was obtained by thermal drying of CaCl 2 .6H 2 O (Merck, Extra Pure) under vacuum as discussed [7] . The dried salts were stored in an inert atmosphere glove box prior to use in the experiments.…”

“…The thermodynamic stability and electrical characteristics of an oxide electrode are known to have strong influence on its electro-reduction behaviour [3,5,6] in addition to many other parameters such as applied voltage, duration of electrolysis, sintering temperature of the oxide performs etc. [3,7,8] . Several studies have been reported on the electrochemical reduction of oxides such as TiO 2 [1,3,5,[8][9][10][11] , Nb 2 O 5 [7,12,13] , UO 2 [14][15][16] , SiO 2 [17][18][19][20][21][22][23][24][25][26] etc.…”