Materials Science Forum Vol. 946

Abstract: Modern functional metal oxide materials are based upon the use of nanostructured particles. In recent years materials on the basis of yttrium oxide find ever-widening application. The properties of yttrium oxide depend heavily on precursors and synthesis conditions. One of the poorly investigated precursors is yttrium sulfate. The study discusses the products of alkaline hydrolysis of yttrium sulfate obtained by the sol-gel method. The influence of the synthesis pH on morphological, thermal and structural properties of compounds has been examined. Formation of non-stoichiometric compounds occluding counter-ions of the reactant salts in their structure has been revealed. The nanostructured hydrolysis products are formed, which increase their specific surface at annealing and retain their morphology and sizes. The obtained results give grounds to expect using yttrium sulfate as a precursor for synthesis of structured yttrium oxide.

Abstract: The possibility of applying a hyperbolic model for calculating thermodynamic characteristics (the standard molar heat capacity, standard molar entropy) to the V–O system is shown. For calculation of the molar specific heat and entropy within the bounds of the model the general concept has been used: a thermodynamic parameter is divided into two components. The first component depends on the molar mass of a compound, the second one is determined by inter particle interaction. The dependence of the inverse value for the interaction heat capacity (entropy) on composition is of linear character within one region of quasi-equilibrium solid solutions (one region combines compounds with the same or similar structure type).The use of the model allowed refining the available experimental data on vanadium oxides and predicting the values of thermodynamic characteristics for compounds poorly studied in experiment.

Abstract: An experimental study of the phase composition for nine samples of the Cu–Ni–Ce–La alloys with different content of components was carried out. The nickel concentration in the experimental samples varies from 3 to 40 wt. %, the sum of cerium and lanthanum concentrations was not exceed 7 wt. %. Alloys samples of the system Cu–Ni–Ce–La were studied using scanning electron microscopy and microprobe analysis, as well as X-ray analysis. Also, Vickers micro hardness was measured on the cross sections of the experimental samples. In this work, the conditions of intermetallic compounds formation in the as-cast samples were studied. The results of the work can be used for the technological processes analysis of copper and copper-based alloys production.

Abstract: The article describes the problem of the experimental determination of complex dielectric permittivity for natural, activated, and modified quartz systems. The results of determination of specific surface, complex dielectric permittivity, sands porosity are presented in this article. The authors obtained the empirical equation of complex dielectric permittivity calculation for natural, activated, and modified quartz sands, taking into account the effect of moisture, specific surface, porosity, impurities content into consideration. The modification of the sand surface by means of mechanical beneficiation and ultrasonic treatment leads to reduction of complex dielectric permittivity and specific surface, thus contributing to the increase of the active centers quantity on the sands surface. The modification of the sand surface by polyvinyl alcohol aqueous solution leads to increase of complex dielectric permittivity. Polyvinyl alcohol aqueous solution modification envisages the creation of new active centers by oligomers inoculation to the surface and blocking the clay component and authigenous film ingredients. Among the considered methods, ultrasonic treatment in aqueous solution and mechanical beneficiation are the most efficient and technologically acceptable ways of activation.

Abstract: Nowadays, nanostructures made on the basis of mixed oxides are of great interest for fundamental scientific and applied researches because of its potential applications, such as photo catalysts, luminophores, sensitive elements of gas sensors and vacuum sensors. The article describes nanostructural properties of NiO–Al₂O₃–SiO₂ prepared by sol-gel method. Nanocomposites were obtained by mixing a solution of Si (OC₂H₅)₄ (TEOS) as a SiO₂ precursor with a solution containing Al (NO₃)₃ · 9H₂O and Ni (NO₃)₂ · 6H₂O. Ethanol was used as solvent. The gel was dried at room temperature and annealed in the 100–500 °C range. The behavior of chemical bonds is considered by using FTIR technique. Crystallization of NiO phase at 500 °C is observed in XRD patterns. Aluminum atoms are incorporated into silica matrix, which was confirmed by XRD. The amorphous structures which are desirable for next generations are formed at room temperature.

Abstract: Creation of reliable and durable composite materials made of components with different properties is an urgent task. Such materials include multilayered steel. Alternation of a large number of heterogeneous layers leads to a set of properties that are unattainable for homogeneous steel. Production of such composite materials faces many problems. The use of diffusion welding has created a number of composite materials based on steels of different composition, and their properties allow you to use them in the manufacture of cutting tools. The purpose of this work was to study the structure of multilayer composite materials obtained with the help of diffusion welding and the study of the heat treatment effect on the material structure. During the study, the structures of samples of six different composite materials were studied after annealing and after quenching of the metal. The study showed that the studied materials have a pronounced layered structure with a sharp transition boundary from one layer to another. The technology used in the production of composites ensures the actual absence of the transition zone and the absence of such frequent diffusion welding defects as stratifications, pores, oxide inclusions, etc. The study found that during heat treatment process sizes of carbide inclusions in the composite layers decreases, and their number increases.

Abstract: Features of the structure and phase transformations in single-crystal nickel alloys 1, 2 after long high-temperature exposures were considered in this paper. The results and studies of the residual mechanical properties of alloys after exposure are given. Nanophase hardening of single-crystal heat resistant nickel alloys was also considered. The method of heat treatment of single-crystal high-temperature nickel alloys was developed based on the studies. It provides an increase in the strength properties of alloys by 20...30%, due to the formation of bulk nanophases (γ_n + γ'_n). The data obtained on structural and phase changes in high-temperature nickel alloys make it possible to evaluate the stability of the structural state of alloys.

Abstract: The study investigates the hydrolysis products of lanthanum nitrate, obtained at various pH values and times of the hydrolytic agent addition. It has been found that the structure formation of lanthanum oxyhydroxide is accompanied by capturing the admixture ions, namely, the anions of the reactant salt and carbonate ions. It has been shown that thermal decomposition of the hydrolysis products proceeds in four stages for faster hydrolysis. If hydrolysis is slow, the intervals merge together into three stages of thermal decomposition. The hydrolysis products of lanthanum nitrate, heated up to 500...550 С, actually consist of lanthanum oxide containing nitrate and carbonate, chemically bonded to the oxide matrix, in its inner regions. The composition of the synthesized samples changes if pH varies. The minimal content of admixture ions can be observed at the synthesis pH > 10, if the time of the hydrolytic agent addition equals 24 h. The obtained results suggest that lanthanum nitrate can be used as a precursor for synthesis of structured lanthanum oxide.

Abstract: The necessity of finding scientifically grounded methods for the development of new heat-resistant, wear-resistant and corrosion-resistant aluminum alloys is presented in the present work. For this purpose, the analysis of modern methods for computer calculation of phase diagrams in multicomponent metal systems using the Thermo-Calc program was carried out. Therefore, a quantitative analysis of the phase diagram the Al-Cu-Mn-Zr system was carried out, as the basis of deformable high-temperature aluminum alloys. Isothermal and polythermal sections of the phase diagram were calculated in this system. The temperatures of phase transformations were calculated. The mass and volume fractions of the phases in the studied alloys were calculated. The range of concentrations and temperatures at which the maximum amount of dispersoids Al₂₀Cu₂Mn₃ may be achieved, was defined. The minimum amount of Al₂Cu phase is calculated, which should correspond to the best heat resistance of alloys. It is substantiated that in the alloys of a new generation of ALTEK type, the use of homogenization and quenching operations is inexpedient, which implies the possibility of a significant reduction in the cost of heat treatment in comparison with industrial alloys, such as 1201.

Abstract: A method for calculation of the diagrams of steel deoxidation and modification by calcium, magnesium, aluminum and boron was developed. The coordinates of the liquidus surfaces of the oxide systems B₂O₃–Al₂O₃–MgO, B₂O₃–Al₂O₃–CaO, B₂O₃–MgO–CaO were found at 1873 K. The energy parameters were determined for the theory of subregular ionic solutions of the studied oxide systems. The coordinates of the solubility surfaces for the systems Fe–Mg–Al–B–O, Fe–Ca–Al–B–O, Fe–Mg–Ca–Al–B–O were calculated. The effect of the total pressure on solubility of magnesium and calcium in liquid iron was studied. The activity of the components of the metallic melt was calculated using the first-order interaction parameters (Wagner's theory). The activities of the components of solid solutions (oxides and spinels) were equated with their molar fractions. It was shown that during extensive refining of metal from the oxygen, only a small fraction of boron oxidizes and these oxides form fraction of the oxide melts. The major non-metallic oxide inclusions were magnesia spinel, calcium bialuminate and liquid oxide formations. The "free" boron was dissolved in liquid metal in amounts which were in equilibrium with oxide phases.