Vol 59, No 6 (2023)

We have studied reaction between mechanochemically activated tantalum powder and amorphous boron in the molar ratio 1 : 2 in ionic melts of salts with various compositions at temperatures of 1023 and 1073 K in an argon atmosphere. The results demonstrate that the use of the ionic melts allows one to obtain nearly spherical TaB2 particles (sp. gr. P6/mmm) ~70 nm in average diameter, with unit-cell parameters a = 0.3077–0.3090 nm and с = 0.3227–0.3245 nm.

The surface morphology, elemental and phase compositions, and local electrical properties of fullerite films containing various atomic fractions of tin and bismuth have been studied using scanning probe microscopy, scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and Fourier transform IR spectroscopy. The films were grown on oxidized single-crystal silicon substrates by deposition from a combined atomic–molecular flow using resistive evaporation in vacuum. Their thickness was 1 μm. The as-grown films consisted of grains ranging in size from 30 to 200 nm. Their X-ray diffraction patterns showed reflections from C60 fullerite with a face-centered cubic lattice, which was in a stressed state due to the incorporation of dopant atoms, and reflections from pure tin and bismuth. Optical spectroscopy results indicated the formation of complexes of fullerenes with Sn and Bi atoms. According to electric force microscopy results, the tin- and bismuth-doped fullerite films have a considerably lower surface potential and a nonuniform surface capacitance gradient distribution.

Layered structures in the form of submicron-thick nickel layers on single-crystal lithium niobate (LiNbO3) ferroelectric substrates have been produced by ion beam sputter deposition. At room temperature, the structures exhibit an interfacial magnetoelectric effect, whose largest magnitude is 108 mV/A in a transverse configuration of the magnetic and electric fields and 4 mV/A in a longitudinal configuration. Analysis of mechanical strain leads us to conclude that the interface makes a considerable contribution to magnetoelectric interaction in the Ni/LiNbO3 structures obtained in this study. The materials can find application in designing piezoelectric devices and acoustic, optical, and spin wave electronics.

In this paper, we report an improved solid-state synthesis of Na3V2(PO4)3 isostructural with the NASICON superionic conductor and ranging in particle size from 0.5 to 4.5 μm with the use of spray drying of an aqueous solution of precursors, followed by annealing in a nitrogen atmosphere. The specific capacity of a composite of the synthesized Na3V2(PO4)3 and expanded graphite reaches 117.00 mAh/g at a charge–discharge rate of C/20 and drops to 76.73 mAh/g after 200 cycles in charge–discharge life tests at a charge–discharge rate of 1C. The apparent diffusion coefficient of sodium ions in the solid phase of the Na3V2(PO4)3/C composite for deintercalation and intercalation processes is 5.87 × 10–11 and 4.60 × 10–11 cm2/s, respectively.

Magnesium aluminate spinel has been prepared by sol–gel synthesis. We have studied the effect of europium and yttrium oxides on the synthesis of magnesium aluminate spinel and kinetics of spinel formation during heat treatment in the temperature range 500–1000°C. According to X-ray diffraction and chemical analysis data, the formation of magnesium aluminate spinel from a dried xerogel prepared from a mixture of the Al(NO3)3 and Mg(NO3)2 compounds in the ratio 2 : 1, respectively, occurred at a temperature of 1000°C and a firing time of 240 min. The resultant material contained free MgO as an impurity phase. The addition of 1.5 wt % Eu2O3 relative to the total weight of the starting mixture reduced the peak spinel formation temperature to 900°C at a firing time of 240 min. In the case of Y2O3, the addition of 3 wt % was needed to maximize spinel formation at this temperature.

Properties of porous materials prepared from glasses of the Na2O–B2O3–SiO2–GeO2 system have been studied using low-temperature nitrogen adsorption/desorption measurements. The results demonstrate that germanium substitution for silicon in the glasses studied leads to an increase in pore volume at SiO2/GeO2 ratios of down to 0.5. The porous glass with this composition has the largest specific surface area and micro- and mesopore volumes. We assume that the observed changes in the porosity parameters of glass in the case of complete germanium substitution for silicon are related to structural features of the borogermanate glass network, associated with B–O–B bond breaking and the formation of non-bridging oxygen atoms.

Porous ceramic materials have been prepared from BS16-6-76 chopped basalt fiber with CuS and ZrO2 additions by granulation, pressing, and subsequent sintering in air. Computer-controlled X-ray diffraction measurements have been used to carry out profile analysis and assess the qualitative and relative quantitative phase compositions of the materials. We have identified the sequence of phase transformations in the basalt fiber and confirmed that fiber crystallization during cooling after sintering begins with the formation of aluminosilicate spinel nuclei, which act as crystallization centers and become incorporated into the structure of orthoclase. The last to form in the phase hierarchy is a low-molecular-weight Fe-containing phase, namely, hematite (α-Fe2O3), built in a framework silicate of isomorphous series. The surface of the basalt fiber in the sintered material modified with copper sulfide and zirconium oxide additions has been shown to be covered with ~500-nm inclusions of a crystalline phase.

Composites have been prepared using nanopowders whose precursors were synthesized by a sol–gel hydrolysis process in 1 M solutions of the ZrOCl2, Al(NO3)3, Yb(NO3)3, and Sr (NO3)2 salts the amount of which corresponded to the basic composition (mol %) 50Al2O3, (50 – n)3Yb-TZP (tetragonal zirconia polycrystals stabilized with 3% Yb2O3), and n = 1, 3, or 6% SrO as a modifier. We have studied how the amount of the modifier influences the phase composition, microstructure, and mechanical properties of the composites. The addition of the modifier has been found to shift the θ-Al2O3 → α-Al2O3 transition to higher temperatures. In situ sintering of the starting nanopowders in the temperature range 1250–1400°C has been shown to result in the formation of alpha-alumina and strontium hexaaluminate. Raising the modifier concentration to above 3% increases the closed porosity of the composites, reducing their bending strength from 700 to 450 MPs.

We have proposed a composition of a new alloy based on zinc alloy TsAM 4-1, prepared from Ts3 crude zinc: TsAMSv 4-1-2.5. The alloy has been studied potentiostatically in potentiodynamic mode in NaCl electrolyte at a potential sweep rate of 2 mV/s. We have assessed the effect of vanadium additions on the electrochemical corrosion behavior of zinc alloy TsAMSv 4-1-2.5 in NaCl electrolyte. The results demonstrate that alloying with vanadium shifts the free corrosion, pitting, and repassivation potentials of the alloys to positive values. With increasing chloride ion concentration, the corrosion rate of the alloys rises, independent of their composition. The addition of vanadium to alloy TsAMSv 4-1-2.5 reduces its corrosion rate in NaCl electrolyte by 15–20%, which in turn ensures a decrease in protective layer thickness and makes it possible to save at least 10% of the metal.