Vol 55, No 2 (2019)

A macromolecular concept of the structure of solids and induction constants are used to quantitatively assess the reactivity of hydroxyl groups on the surface of single-crystal matrices, as exemplified by silicon. The oxide layer on the surface of such matrices is shown to influence the reactivity of silanol groups in atomic layer deposition processes.

The resistivity of low-palladium copper-based FCC solid solutions has been measured as a function of temperature during heating and cooling. We have compared the electrical properties of pure copper and those of the Cu–8 at % Pd alloy, which can undergo L1₂ ordering, after similar heat treatments. The anomalies found in the Cu–5.9 at % Pd alloy have been interpreted in terms of the formation of nuclei of an L1₂ ordered phase, in contrast to the generally accepted Cu–Pd phase diagram. The resistometry data indicate that the temperatures of the order → disorder phase transformation (t_c) in the Cu–8 at % Pd alloy is ~380°C, and that in the Cu–5.9 at % Pd alloy is t_c ≈ 350°C. The experimental data obtained are compared to first principles calculation results on the stability of the L1₂ phase in the Cu–Pd binary alloys.

Plastic deformation is shown to influence magnetic parameters of rapidly quenched wire with the composition Co₆₆Fe₄Ta_2.5Si_12.5B₁₅ prepared by melt drawing and its sensitivity to tensile stress. Plastic deformation reduces magnetic parameters, such as the remanence, coercive force, and differential magnetic permeability, but enhances their sensitivity to external tensile stress. This finding can be accounted for by the increase in the magnetostriction constant of the wire in response to the plastic strain induced in it.

We have studied water vapor sorption properties of close-packed opal structures made up of monodisperse spherical silica particles 150 to 350 nm in diameter. The results attest to polymolecular water adsorption followed by capillary condensation in meso- and micropores within the structure-forming particles. The maximum adsorption value, ~0.13 g of H₂O per gram of dry SiO₂, essentially coincides with the specific volume of inner pores in the particles. The annealing temperature has been shown to influence the adsorption properties and effective refractive index of the opal photonic crystals. The refractive index of dry and adsorbed water-filled opal structures has been determined as a function of annealing temperature.

Nanostructured titanium dioxide (TiO₂) with a particle size from 7 to 50 nm, photocatalytically active for organic reactions under illumination with visible light, has been prepared by sol–gel synthesis at different pH values of the starting solution. X-ray diffraction data demonstrate the formation of a crystalline anatase phase in an acid medium and an amorphous phase in an alkaline medium. Annealing at a temperature of 350°C for 4 h has led to a phase transition from the amorphous structure to anatase in all of the samples. The particle size has been shown to increase from 7 to 50 nm as the solution pH rises from 3 to 9. Further increasing the pH value to 10 reduces the particle size to 23 nm. Diffuse reflection spectra indicate that the band gap of the samples ranges from 2.9 to 3.4 eV and that annealing reduces it to 2.8–3.2 eV. According to comparative testing results, the efficiency of the synthesized TiO₂ as a catalyst for oxidative \({\text{S}}_{{\text{N}}}^{{\text{H}}}\) cross-coupling of acridine with indole is comparable to that of the commercially available catalysts Degussa P25 and Hombifine N, as evidenced by product yields above 50%.

Sr_0.5Ba_0.5Nb₂O₆ (SBN) relaxor ferroelectric films of different thicknesses have been grown on Pt(111)/Si(001) substrates by rf sputtering. We have studied their structure, composition–depth profiles, lattice dynamics, and dielectric properties at temperatures from 25 to 200°C. The results demonstrate that the composition of the films does not vary with depth and corresponds to that of the ceramic target used and that the SBN/Pt interface has a transition layer more than 30 nm in thickness, consisting of a mixture of platinum and SBN. According to X-ray diffraction characterization results, the films are polycrystalline, with a preferential orientation of the SBN [001] axis along the normal to the substrate surface. At a film thickness of 950 nm or above, the SBN films on Pt(111)/Si substrates differ insignificantly in unit-cell parameters, lattice dynamics, and Burns temperature from SBN single crystals. We discuss general relationships of structure formation and characteristics of the films.

Using characteristics of valence electron and core level X-ray photoelectron spectra at binding energies in the range from 0 to ~1000 eV, we have determined the quantitative elemental composition of the surface of silicate glass samples containing Si, Al, Na, K, Ca, Mg, Fe, S, O, and C, whose surface was modified in different ways. We have identified the oxidation states of the ions in the glasses, which, as expected, correspond to Si⁴⁺, Al³⁺, Na⁺, K⁺, Ca²⁺, and Mg²⁺. It has been shown that chemical modification of the glass surface produces the largest changes for potassium and sodium: their concentration considerably decreases in comparison with that in the starting glass.

Mechanically activated Ni + Al mixtures containing two types of nickel powder, PNK (carbonyl nickel) and PNE-1 (electrolytic nickel), have been characterized by X-ray diffraction. The behavior of structural parameters of the mixtures containing both nickel powders has been studied as a function of milling time. During milling, the internal stress of the nickel and aluminum in the mixture containing the PNK nickel powder reaches a higher level in comparison with the PNE-1 powder. Moreover, in the case of the PNK powder, synthesis directly in the grinding vial of the mill requires a longer milling time in comparison with the PNE-1 powder (11 and 7 min, respectively). Milling for a time shorter than the critical one increases the density of structural defects in both mixture components (as evidenced by an increase in the full width at half maximum of X-ray diffraction peaks and a reduction in their intensity). Mechanical activation produces different structural changes in the nickel and aluminum: the maximum internal stress in the nickel exceeds that in the aluminum, but the aluminum is comminuted to a higher degree (its crystallite size decreases to a lower level).

The behavior of individual rare earth elements of the heavy-medium group (HMREE) in the composition of extremely loaded mixture of extractants of Cyanex^®572–TBP in the conditions of scrubbing with solutions of nitric acid without rare earths in extraction separation of the concentrate of MREE is discussed. The effect of the concentration of nitric acid in scrubbing solutions on the degree of stripping of the sum and individual HMREE has been studied. The possibility of extraction separation for the lines of Tb–Gd, Dy–Tb, Ho–Dy, and Er–Ho for scrubbing solutions containing less than 0.6 М nitric acid has been shown. The results of the study have been checked on a model counterflow cascade of extractors.