V. I. Shapoval

ELECTROCHEMICAL SYNTHESIS OF TUNGSTEN AND MOLYBDENUM BORIDES IN A DISPERSED CONDITION

Electrolytic deposition of tungsten and molybdenum boride particles from ionic melts is studied. Conditions are found for preparing different boride phases. If the anode material is graphite and the voltage in the bath does not exceed 2.5 V the cathode deposit consists mainly of tungsten and molybdenum metals. A mixture of phases (M, M2B, MB, MB2, M2B5) is produced on the cathode with U=2.5−3.5 V, while with U=2.3−3.5 V, while with U=3.5−4.5 V the deposit consists of the higher boride MB4. On the whole the process of electrochemical synthesis for molybdenum and tungsten borides is governed by the following interconnected parameters: electrolytic bath composition, voltage in the bath, temperature, and duration of electrolysis.

Chemical and electrochemical behavior of carbonate melts containing silicon oxide

The optimal conditions of electrochemical synthesis of silicon carbide in carbonate melts containing silicon oxide were determined on the basis of thermodynamic calculations and data of cyclic voltammetry.

Physicochemical properties of tungsten carbide powders prepared from ionic melts

Fine-particle tungsten carbide powders were prepared by high-temperature electrochemical synthesis, and their physicochemical properties were studied. The ceramics fabricated from these powders showed superior mechanical properties. The powders were found to exhibit high catalytic activity for hydrogen electrogeneration and electrodissolution.

Theoretical foundations of galvanic treatment of dielectrics and semiconductors in ionic melts

The behaviors of diamond, cubic boron nitride, and silicon and boron carbides in ionic melts were analyzed thermodynamically and studied by potentiometry and corrosion measurements. The redox reactions occurring at the dielectric (semiconductor)/ionic melt interface were assumed to give rise to an electrochemical potential and surface conductivity. Controllability of the electrochemical potential makes metallization of the materials considered possible. Techniques are suggested for the electrodeposition of molybdenum, tungsten, and their carbides onto diamond, boron nitride, silicon carbide, and boron carbide particles.

Theoretical Foundations and Implementation of High-Temperature Electrochemical Synthesis of Tungsten Carbides in Ionic Melts

Thermodynamic and voltammetric studies of tungsten- and carbon-containing melts were carried out to find the conditions for the high-temperature electrochemical synthesis of tungsten carbide coatings and powders.

Electrochemical synthesis of molybdenum, tungsten, titanium, and zirconium silicides in a dispersed state

The electrolytic deposition of molybdenum, tungsten, titanium, and zirconium silicide powders from ionic melts was investigated. Conditions for the deposition of various phases were found. Electrochemical synthesis of the silicides was affected by the interrelated factors of bath composition, voltage, current density, temperature, and time.

Electrolytic powders of silicides and borides of chrome

Compounds of chrome with silicon and boron (silicides and borides) represent an important group of inorganic compounds with a number of valuable properties. Powders of silicides and borides of chrome may be used to produce structural materials with specified electrophysical and refractory properties, and resistance to corrosion and wear so that they are highly promising for use in new areas of technology. Electrochemical synthesis of chrome silicides was carried out from a molten KCl-KF-K{sub 2}CrO{sub 4}-K{sub 2}SiF{sub 6} mixture. Electroreduction of the fluoroxide complex Cr(VI) to Cr{sub 2}O{sub 3} takes place according to the reversible three-electrode mechanism and is controlled by diffusion. Optimization of the process was reduced to determining the conditions of producing high silicdes CrSi{sub 2} having the most valuable physicomechanical properties.

Electrocrystallization of Molybdenum Carbide in Oxide Melts and the Influence of Electrolysis Parameters on Grain Size and Quality of Deposits

The influence of current density and temperature on crystal grain size in electroplating of molybdenum carbide from tungstate-molybdate-carbonate melts was studied. The initial stages of molybdenum carbide electrocrystallization from tungstate-molybdate-carbonate melts at 750-900° on different substrates were studied by the method of galvanostatic switch-on curves and in situ microstructural analysis.

Electrochemical synthesis of intermetallic compounds and complex carbides based on molybdenum (tungsten) and cobalt (nickel)

Systems for the joint electrodeposition of molybdenum (tungsten) and nickel(cobalt) from ionic melts have been identified. Conditions for depositing the intermetallics molybdenum(tungsten)-nickel(cobalt) and double carbides based on these were ascertained. It is shown that the process of electrochemical synthesis is determined, on the whole, by the ratio of partial currents of reacting components, energies of interaction between them, and the occurrence of parallel reactions between components.

Effects of alkali-metal cations on nitrate-ion N-O bond force constants in ionic melts

Measured frequencies from pure nitrate liquids have been used to calculate the force constants for the nitrate ion and the M+-NO3− systems (M+ = Li+, Na+, K+, Rb+, and Cs+) by a matrix successive-approximation method based on perturbation theory in dependent coordinates. The valency force constants Kq for the N-O bonds are increased by comparison with free NO3−. The N-O bond strengthening is not adequately explained by cation-anion interaction because there is electron-density transfer mainly by the π mechanism within the NO3−. Correction for the vibrational parameters of the interacting particles confirms the previously demonstrated acid-base mechanism for the cation-anion interaction in liquids containing nitrate.