Key Engineering Materials Vol. 854

Abstract: The article describes the results of studies of Ni-Al ultrathin films obtained by the resistive thermal evaporation method and having the characteristic dimensions of islands of 700-1000 nm with a film thickness of about 500 nm. This paper presents a method of obtaining a film using a unit for creating high vacuum and the subsequent deposition of the film. The obtained film sample was studied using an optical microscope, a scanning probe microscope and a Fourier analyzer. The kinetic characteristics of the film, the film relief, and the characteristic dimensions of the islands were established; the search for regularities in the island structure of films was carried out and its electrical conductivity was determined.

Abstract: The structural changes of condensed fullerenes C₆₀ and C₂₈ at a temperature increase from 200 K to 2000 K have been studied by computational methods using the TERRA software for carbon-argon systems. The processes of destruction of fullerenes C₆₀ and C₂₈ molecules are presented, and the temperature ranges of their thermal stability are determined: up to 1000 K and up to 400 K, respectively. The following thermophysical parameters of the C₆₀-Ar and C₂₈-Ar systems are considered: specific volume, entropy, total enthalpy, total internal energy, equilibrium specific heat, molar mass of the gas phase, gas constant, and mass fraction of the condensed phase. A comparative analysis of their changes with increasing temperature is carried out. The results obtained in the course of thermodynamic modeling are similar to the results of a full-scale experiment conducted under similar conditions. In the future, the obtained data can be used to determine the explosive and fire-hazardous properties of fullerenes as a dispersed solid.

Abstract: Calculation of molecular structure and related vibrational spectra of the isopropyl nitrate was carried out by means of density functional theory (DFT) by employing the Gaussian 03 mathematical package. The molecular geometries were fully optimized by using the Becke's three-parameter hybrid exchange functional combined with the Lee–Yang–Parr correlation functional (B3LYP) and using the 6-31G(d) basis set. By scanning the dihedral angles around C-O and C-C bonds, two energetically most favorable conformers of isopropyl nitrate - TG, GT forms were found. Calculations of the frequencies and forms of normal oscillations of the obtained forms of isopropyl nitrate are performed. The spectral features of the conformational state of isopropyl nitrate and the spectral effects of the formation of intramolecular H...ONO₂ hydrogen bonds have been revealed.

Abstract: This paper presents a numerical simulation of powder sintering. The numerical model presented in this paper uses the discrete element method, which suggests that the material can be modeled by a large set of discrete elements (particles) of a spherical shape that interact with each other. A methodology has been developed to determine the DEM parameters of bulk materials based on machine vision and a neural network algorithm. The approach is suitable for obtaining the exact values of the DEM parameters of the investigated bulk material by comparing the visual images of the material’s behavior at the experimental stand in reality and in the model. Simulation of sintering requires an introduction of cohesive interaction between particles representing interparticle sintering forces. Numerical sintering studies were supplemented with experimental studies that provided data for calibration and model validation. The experimental results have shown a significant capability of the designed numerical model in modeling sintering processes. Evolution of microstructure and density during sintering have been studied under the laboratory conditions.

Abstract: The paper deals with well cementing, which is a complex engineering task requiring special tools and technologies. The authors give an example of complications that arise due to the poor quality of well cementing. The aim of the work is to study the mineral ultrafine additive-nanosilicates, which increase the strength of cement stone and reduce its porosity. Nanosilicate is formed during the cleaning of ore-thermal furnaces in metallurgical plants. One of such technologies is application of metallurgical waste, since it can improve the environment by cleaning the sludge fields from waste and reduce the cost of cement slurry by reducing the amount of cement in the composition. The study provides practical data showing that nanosilicates positively affect the strength of cement stone, reducing its porosity.

Abstract: The article analyses the application of a composite material based on magnesite cement and red mud for the production of high-resistant materials and structures. Technical characteristics are given proving that this composite has several advantages comparing with other materials and opens up new opportunities for the disposal of toxic wastes and developing new materials with unique characteristics. The advantage of this direction is that the composite material created on the basis of “red mud” has increased strength and water resistance; also, it has the structure of a homogeneous monolithic stone. A wide range of applications of neutralized waste is an undeniable positive factor.

Abstract: The development of the fuel and energy complex entails a direct increase in energy consumption and the development of fundamentally new types of resources. In the near future, it is predicted that the role of solid fuels, including low-grade ones, will increase in the country's fuel and energy balance, which is primarily due to their large reserves. Russia ranks third after the USA and Brazil in the world for this mineral and, according to the latest estimates, potential reserves of this raw material are in the order of 700,288.85 million t. The article is devoted to the analysis of the chemical composition of oil shale of the Leningrad field. The point microanalysis of oil shale was carried out on the scanning electron microscope TESCAN, and IR spectra of various functional groups that are part of the shale were obtained and analyzed. It has been revealed that the functional groups C-C, C=O, CH₂, CH₃, SH are typical for the organic component of the oil shale of the Leningrad field. Carbonates, silicates and hydroxides mainly represent the mineral part with impurities represented by phosphates, sulfides and sulfates.

Abstract: The article is devoted to the analysis of the influence of heat treatment of oil shale of the Leningrad field on the total surface area of nanopores and total porosity. Oil shale with particle size up to 0.125 mm in the form of powder and in the form of shale briquette was subjected to heat treatment. The change in the total porosity was studied in the temperature range (0÷1000) oC. The change in the total surface area of nanopores was studied by comparing the initial sample of oil shale with the oil shale ash obtained at 1000 oC. The data presented in this paper is indicative of a decrease in the oil shale nanopores total surface area under heat treatment, for example, for pore diameters (3÷4) nm the area decreases from 15.29 cm²/g to 2.563 cm²/g.

Abstract: Silicon dioxide is the most common silicon compound and a major constituent of the Earth’s crust. Silicon dioxide, also known as silica, is a chemical compound that is an oxide of silicon with the chemical formula SiO₂. Silica is most commonly found in nature as quartz. Quartz exists in natural and synthetic forms. More specifically α-quartz is a widely known material, which is stable at low temperatures and pressures. The α-quartz is considered competent material because over the past many years it has attracted wide attention due to its unique characteristics. The article presents the research results from comparison between one of the morphological varieties of quartz – vein quartz of shungite rocks from Zazhogino deposit of Karelia – and a reference quartz sample. Via the Rietveld method, the values of the lattice parameters are determined. Apparent coherent length for vein quartz samples having contacts with various minerals are determined by the approximation method.

Abstract: The application of special nanomaterials is promising for the development of new methods for the diagnostics and treatment of cancer. Photodynamic therapy (PDT) is a well-known and recognized method of cancer treatment. This type of therapy is less carcinogenic and mutagenic compared to radiation and chemotherapy, since the applied photosensitizers do not bind to DNA of the cells. However, currently this technique is only applicable to skin cancer, while its extension to the treatment of abdominal tumors requires the creation of pharmacological drugs for PDT, which along with a photosensitizer include a colloidal solution of nanosized luminescent phosphor emitting visible light with the required wavelength under the influence of infrared, X-ray or γ-radiation, which easily penetrates the body tissues. Since photosensitizers are already available as commercial products, the most important goal is the development of nanosized phosphors providing the required radiation convertion. In this study, the effects of hydrothermal synthesis, duration and the conditions of rapid thermal annealing (RTA) on Y₂O₃:Eu phosphor particle size were studied. The hydrothermal synthesis technique was carried out in two ways: chloride (precipitation from a chloride solution using NaOH and NH₄OH precipitators) and acetate (decomposition of mixed acetate either without a dispersant at 230° C for 24 hours, or using PEG-200 and PEG-2000 as dispersants at 230 °C for 12 hours). The rapid thermal annealing was performed either at 600 °C for 20 minutes, or at 800 °C for 5 minutes. The developed synthetic approaches afforded Y₂O₃:Eu nanosized phosphor samples with the particle size not exceeding 200 nm.