Key Engineering Materials Vol. 909

Abstract: The article describes the methods for producing thin films and structures based on SiC, GaN and their SiC – AlN and Al – GaN solid solutions, as well as mathematical models of film growth and properties-behavior of the I–V characteristics of heterostructures. Two models were developed for producing thin films and heterostructures based on SiC, GaN and their solid solutions. The first model makes it possible to determine the sputtering coefficient when producing films by high-frequency magnetron sputtering. In the second quantum-mechanical model, the equation for the gap of the mean field of condensate was built and the growth rate of a film on the crystalline substrate was determined. The current-voltage characteristic of the transistor based on the AlGaN / GaN heterosystem was provided. The models for the growth of heterostructure films made it possible to modify the technologies for producing perfect SiC crystals and SiC – AlN solid solutions. It was possible to offer a pilot plant for growing SiC crystals with improved control over the modes of induction high-temperature heating of the growth crucible.

Abstract: The IR absorption spectra of hexagonal crystals of lithium iodate α-LiIO₃, used in laser shutters for ship wiring, where the quality, transparency and power of laser radiation are of great importance, are studied. The transmission spectra allowed us to determine the width of the crystal band gap 4.37 eV along the Z-axis (C₆ [0001]) and 4.46 eV along the axis perpendicular to the Z axis. The activation energies and the wavelength of the vibrational centers associated with the vibrations of the H₃O⁺, OH^-, H₂O groups, heavy D₂O and semi-heavy molecules HDO are determined. It is established that the band 1450-1650 cm^-1 is a superposition of at least two broad absorption maxima centered at ~1550 and ~1600 cm^-1. It was experimentally established that the ratio of the absorption coefficients of these bands was ~1:1 (75:74 cm^-1) for crystals grown in H₂O, and ~2:1 (161:84 cm^-1) – for crystals grown in D₂O. This allows us to assume that in a lithium iodate crystal grown in D₂O, the bands 1550 cm^-1 and 1600 cm^-1 correspond to the vibrations of the bound HDO and H₂O molecules, the band 1150 cm^-1 corresponds to the vibrations of heavy water molecules. The results of the study allowed us to propose a mechanism of transport and translational diffusion of protons and to determine the presence of heavy water molecules in crystalline materials, as well as to diagnose the quality of laser crystals.

Abstract: The paper presents the results of experimental studies of the electro-optical properties of β-Tl_1-xCu_xInS₂ (0 X 0,015) single crystals. It was found that in measurements of the induced birefringence, the transmission of the polarizer - crystal - analyzer (P-C-A) system is nonzero both for the presence of an external electric E = 0 and in its absence, which is apparently associated with the presence of internal fields arising in crystals during their growth ().

Abstract: Information about the lime composition used for the restoration of limestone is given. To develop a repair composition, a polysilicate solution was used. It has been established that polysilicate solutions contain a monomer, oligomer and polymeric varieties of silica. It was found by the molybdate method that the content of the polymeric form of silica γ-SiO₂ in the polysilicate solution is 15–19.93%, depending on the content of the silica sol. This composition of the polysilicate solution contributes to the manifestation of the high reactivity of silica. The technology for carrying out restoration work involves the application of a primer layer - liquid glass, followed by the application of a calcium chloride solution. After 20-30 minutes after applying the primer, it is possible to apply the repair composition with a spatula. It is shown that the use of a polysilicate solution in the formulation of a lime composition helps to increase the water resistance, adhesion strength of the composition to the base, and accelerates curing.

Abstract: The paper provides a comparative assessment of using four types of fuel ashes from different types of coal combustion as additives to replace part of the cement in producing a composite binder. The authors assessed the effectiveness of the additives by cement dough properties (water-binder ratio, normal density, initial setting) and the strength of the binder at 1, 3, 7 and 28 days of hardening. The ashes are ranked according to their efficiency in the structure of composite binder in the following sequence: acid ash from Reftinskaya power plant → acid ash from Novotroitskaya power plant → basic ash from Nazarovskaya power plant → acid ash from Troitskaya power plant. The research revealed that the most effective mineral additives were basic ash from the Nazarovskaya power plant and acid ash from the Troitskaya power plant. Their use reduced the amount of cement by 15% and 25% respectively, while reducing the strength by no more than 3%.

Abstract: The paper presents the results of research on creating a high-strength cement composite using a complex additive. The optimal concentrations of additives of the Odolit-K hyper plasticizer in combination with bentonite have been determined. A significant decrease in the w / c ratio and an increase in the cement stone's strength was obtained. High-strength cement composites have been obtained with the optimal content of the complex additive. The volume-weighted average crystallite sizes were calculated using the Scherrer formula on the basis of X-ray studies. Deformation diagrams of statically loaded samples of prisms of the basic and control compositions of high-strength concrete were obtained. Deformation diagrams are investigated.