Electrolytic powders of silicides and borides of chrome

Advances in high-temperature electrochemical synthesis in ionic melts by the onset of XXI century

“…Shapoval et al [46] suggested a classification of the modes of electrochemical synthesis, according to which a large difference (up to 0.73 0.8 V) between the electrodeposition potential of Cr [25], Mo [27], or W [28] from a chloride3cryolite melt containing sodium chromate (or molybdate, or tungstate) and the discharge potential of boron oxyfluoride complexes [26] in the same systems suggests that high-temperature electrochemical synthesis of chromium, molybdenum, and tungsten borides can be performed under conditions of kinetic control only. Electrochemical synthesis of chromium borides was performed from a chloride3cryolite melt containing boron chromate and oxide [26].…”

“…Electrochemical synthesis of chromium borides was performed from a chloride3cryolite melt containing boron chromate and oxide [26]. Depending on the melt composition and electrolysis parameters, either individual phases of Cr 2 B, CrB, and CrB 4 or their mixtures with various component ratios were obtained.…”

“…High-temperature electrochemical synthesis of chromium silicides was performed in the system KCl3KF3K 2 SiF 6 3K 2 CrO 4 . Depending on the melt composition and electrolysis parameters, either Cr 3 Si and CrSi 2 individual phases or mixtures of these, with a small content of free silicon, were obtained [53,57].…”

Electrochemically active species and multielectron processes in ionic melts

“…The molybdate and tungstate ions are stable in NaCl ± NaF melts; the O 27 is not replaced by F 7 with the formation of oxofluoride complexes, and they do not manifest electrochemical activities up to decomposition potentials of the background electrolyte. 213,214 It is known that aluminium fluoride complexes possess acceptor properties with respect to O 27 ions and hence can be used for controlling the acid-base properties. On introduction of AlF 3À 6 in a sodium chloride melt containing MoO 2À 4 and WO 2À 4 anions, waves at 0.7 ± 1.0 V appear on the voltammetric curves.…”

“…x . Taking into account the linear dependences of the reduction wave peak current on the EO 3 (EO 2À 4 ) concentration and on the polarisation rate and using the mass transfer constant of (5 ± 6)610 73 cm s 71 , Malyshev et al 214 reached a conclusion on the diffusion nature of the limiting current. The dependence of the potential of molybdenum or tungsten electrode in a NaCl ± Na 3 AlF 6 melt on the EO 3 or EO 2À 4 concentration vs. the Pt, O 2 /NaCl ± 0.05 Na 2 MO 4 half-cell is well described by the Nernst equation.…”