E. V. Nikitina

High-temperature hydrolysis of magnesium nitrate hexahydrate

The high-temperature hydrolysis of magnesium nitrate hexahydrate is studied. The presence of basic magnesium nitrate in the decomposition product at 160°C is found by IR spectroscopy and X-ray diffraction analysis. A mechanism for the high-temperature hydrolysis of Mg(NO3)2 · 6H2O is proposed.

Formation of Oxide Layers on Aluminum, Niobium, and Tantalum in Molten Alkali Metal Carbonates

The electrochemical synthesis of niobium, tantalum, and aluminum oxide nanolayers is studied in the melt of lithium, sodium, and potassium carbonates with various additives to a salt phase in an oxidizing atmosphere at a temperature of 773 and 873 K. A scheme is proposed for high-temperature anion local activation of the process.

Selective Dissolution of Brass in the Molten Eutectic Mixture of Lithium, Sodium, and Potassium Carbonates

The dissolution of L63 brass in molten alkali metal carbonates is shown to occur at an operating temperature of 773 K in the potentiostatic and galvanostatic regimes. The size and number of pores are found to depend on the electrochemical parameters, namely, the applied potential and the current density.

Volumetric thermal expansion coefficients of the equiatomic Na–K and K–Rb melts

The volumetric thermal expansion coefficients of the equiatomic Na–K and K–Rb melts at 373 K are calculated using variational method with an additive hard-sphere reference system. It is found that the Krasko–Gurskii model pseudopotential with the exchange-correlation Geldart–Vosko function yields better agreement with the experimental data as compared to the local Animalu–Heine pseudopotential with the exchange-correlation Toigo–Woodruff function.

Self-diffusion coefficients of cadmium and indium in liquid

The self-diffusion coefficients of liquid Cd and In near melting temperatures are calculated by the Helfand–Devis–Palyvos method using a model square-well pair potential in the random phase approximation. Adequate agreement between the calculated and available experimental data is achieved for both metals under study.

Effect of the electrolyte composition on the corrosion of 12Kh17 steel in molten alkali metal carbonates

The corrosion of 12Kh17 steel in the melts of alkali metal carbonates containing additions of various chemical types is studied using anodic potentiostatic polarization. The morphology of the 12Kh17 steel surface is analyzed by electron-probe microanalysis. The introduction of corrosion passivators and activators affects the mechanism of local corrosion damages. The corrosion of the steel proceeds according to an electrochemical mechanism. Carbonate anions serve as oxidizers of the steel along with oxygen dissolved in the melt. Treatment of a corrosive medium can be used to protect metallic constructions against corrosion in high-temperature salt electrolytes. Combined introduction of corrosion activators and passivators in a salt phase makes it possible to form protective layers with a high corrosion resistance.

Corrosion-electrochemical behavior of zirconium in molten alkali metal carbonates

The corrosion and electrochemical characteristics of zirconium during its interaction with molten lithium, sodium, and potassium carbonates containing from 1 to 5 wt % additives to the salt phase are studied in a temperature range of 500–800°C using gravimetry, corrosion potential measurement, and anodic polarization. The substances decreasing the corrosion losses due to the strengthening and thickening of an oxide film (lithium, sodium, potassium hydroxides) are used as passivators. Sodium chloride, fluoride, and sulfate serve as corrosion stimulators (activators).

Choice of quenching temperature and its effect on the structure and properties of a high-strength grade 01979 aluminum alloy

Differential scanning calorimetry data are presented for the 01979 alloy produced by granular technology. The optimum quenching temperature is confirmed. Strengthening phases dissolve most completely at this temperature. The phase composition of the high-strength aluminum alloy is studied using scanning microscopy and electron microprobe analysis. The AlCu4, AlCr2, and MgZn2 phases and their interplanar spacings are determined.

Effect of alloying on the phase composition of titanium carbonitride–titanium nickelide alloys

X-ray diffraction, electron microprobe analysis, electron microscopy, and chemical analysis are used to study the effect of alloying with zirconium, niobium, vanadium, and molybdenum on the phase composition of titanium carbonitride–titanium nickel cermets. It is shown that two-phase alloys containing alloyed titanium carbonitride and titanium nickelide can only be produced by alloying with zirconium. The addition of niobium, molybdenum, and vanadium leads to the formation of a third phase, namely, NbzNi, Mo(Ti,C), or V4Ni, in the alloy. A correlation between the phase composition of the alloys and the ratio of the energies of formation of titanium carbides and the carbides of alloying elements is found.

Interaction of Fe–Al–Cr–C with the melt of an alkali metal carbonate

The interaction of an Fe–Al–Cr–C (29.5 wt % Fe, 29.35 wt % Cr, 2.56 wt % C, 38.59 wt % Al) alloy with the melt of a lithium, sodium, or potassium carbonate containing 1–5 wt % addition to a salt phase is studied by gravimetry and measuring the corrosion potential and anode polarization curves in the temperature range 500–600°C. As passivators, the substances that decrease the corrosion losses due to hardening and thickening of an oxide film (lithium, sodium, potassium hydroxides) are used. As corrosion stimulators (activators), sodium chloride, fluoride, and sulfate are used. The coalloying of iron with chromium and aluminum results in high corrosion resistance against both frontal (continuous) and local (pitting, intercrystalline) corrosion as a result of formation of chemically resistant and high-adhesion oxide layers with their participation. X-ray diffraction analysis reveals gamma aluminum oxide, spinel (alumochromite) traces, and lithium aluminate at the surface.