Structure and phase composition of material based on vanadium alloy V-4.9Ti-4.8Cr and ferrite steel 17Cr-12Ni-Fe

Three-layer materials consisting of the V-4.9Ti-4.8Cr/ferrite steel 17Cr-12Ni-Fe /V-4.9Ti-4.8C

The influence of scandium on the composition and structure of the Ti-Al alloy obtained by "Hydride Technology"

In this study the influence of scandium on the structural and phase state of the Ti-Al alloy obtained by the method of “Hydride Technology” (HT). The Rietveld method has allowed for determining the content of basic phases of the 49at.%Ti-49at.%Al-2at.%Sc system. By means of the methods of transmission electron microscopy (TEM) and X-ray spectral microanalysis, it has been established that scandium additives into the Ti-Al system result in the change of the quantitative content of phases in local regions of the structure. The Ti2Al5 phase has been found, and Ti2Al has been absent. In the morphology of substructures Ti-Al and Ti-Al-Sc there are lamellar structures or lamellae; the peculiarities of the distribution, fraction and size of which are influenced by scandium additives. The average width of Al-rich lamellae has been 0.85 U+03BCm, which is four times greater than that for the Ti-Al system (0.21 U+03BCm). For Ti-rich lamellae of the sample of the Ti-Al-Sc alloy, the average width of the lamellae has been 0.54 U+03BCm, and for Ti-Al it has been 0.34 U+03BCm. Based on the obtained data, a scheme of the distribution of phases in the composition of the Ti-Al-Sc alloy in the lamellar structures has been proposed. It has been established that in the Ti-Al-Sc system there is growth of the near-surface strength relative to Ti-Al. In this way, the microhardness of the Ti-Al-Sc alloy has amounted to 1.7 GPa, that is of the Ti-Al alloy which is 1.2 GPa

Structure peculiarities of binary state diagrams of vanadium with neighboring elements of Mendeleev’s periodic table

Data on search for correlations between a structure of state diagrams of binary systems based on V-Me (Me = Ti, Zr, Hf, Nb, Ta, Cr, Mo, W) and crystal-geometric and crystal-chemical parameters were presented. Manifestation of both positive and negative deviations in experimental concentration dependences of the atomic volume in solid solutions in systems V-Me (Me = Ti, Nb, Ta, Cr, Mo) from Zen's law was established. It was found that in the systems with unbounded regions of solid solutions, the deviation from Zen's law is insignificant. A correlation was found between the types of state diagrams and the difference in atomic volumes of alloy-forming elements in systems V-Me (Me = Ti, Nb, Ta, Cr, Mo)

Corrosion resistance of neodymium and dysprosium hydrides

This paper describes the methods of obtaining hydrides of rare earth elements such as dysprosium and neodymium. The properties and corrosion resistance of these elements are investigated. A synthesis method of monophasic dysprosium and neodymium dihydrides is presented. Synthesized dihydrides are agglomerates with an average size of 3-50 µm and are formed by crystalline grains of a nanometer size. BET specific surface area, morphology, elemental analyses and composition of samples have been studied. Corrosion stability in aqueous solutions of hydrochloric acid and sodium hydroxide were studied. It was determined that both hydrides undergo hydrolysis in acid and alkaline mediums. Neodymium hydride is more stable to corrosion than dysprosium hydride, which is proved by its longer exposure to aggressive medium to hydrides. The formation of insoluble /poorly soluble products of corrosion can make a significant contribution to the process of powder dissolution

Peculiarities of structure and phase composition of V-Ti-Cr alloy obtained by sintering technique

Abstract Alloy of the V-Ti-Cr system is a promising material exploited under high radiation and in corrosion environment. We sintered V-4.9Ti-4.8Cr alloy from particles with original average size of 30, 280 and 200 μm, respectively for vanadium, titanium and chromium powders, by pressing of the powder mixture and its further sintering. The studies were undertaken using the methods of X-ray structural analysis, scanning electron microscopy with an energy dispersive analyzer and transmission electron microscopy. It was established that the structure of the alloy represented matrix grains (BCC solid solution), along the boundaries and at junctions of which the groups of oxycarbonitride particles of V, Ti, Cr (C,N,O) type of the variable elemental composition were arranged. The particles possessed a plate-like (0.4 x 2.0 μm) and rounded (0.5 μm) shape. The solid solution of the alloy was heterogeneous by concentration. This was evidenced by the complications of the diffraction patterns obtained from the corresponding sections of the structure. These were cords of main reflexes, satellites and emergence of a moire banded contrast in separate sections of the sample. Inside the matrix grains, there were nanoparticles (15 μm) of carbide V55Cr25C20, being a source of elastic internal local stresses

The structural and phase state of the TiAl system alloyed with rare-earth metals of the controlled composition synthesized by the "hydride technology"

The structural state and the quantitative phase analysis of the TiAl system, alloyed with rareeart

Direct synthesis of dimethyl ether from synthesis gas: Experimental study and mathematical modeling

Direct synthesis of dimethyl ether (DME) from syngas, was investigated over a CuO-ZnO-Al2O3 catalyst for methanol synthesis and a γ-Al2O3 catalyst for a methanol dehydration. On the base of mathematical modeling, thermodynamic analysis was carried out in a wide range of pressures (10–100 bar) and temperatures (220–280 °C) for binary mixtures (H2 + CO) with an H2/CO = 1–6 M ratio. The influence of reaction conditions on the equilibrium content of components in the mixture was modelled. The effect of the loading method of catalysts of the methanol synthesis and its dehydration (layerwise loading, mixing) in the DME synthesis in a single reaction step on the CO conversion and the yield of DME was experimentally studied. It has been demonstrated that the layerwise combined loading with the intermediate mixed layer of CuO-ZnO-Al2O3 catalysts of the methanol synthesis and the γ-Al2O3 catalyst for the DME synthesis (2:1:2, ratio parts, i.e. two parts of the catalyst of the methanol synthesis, one part of a mixture of the catalysts and two parts of the catalyst of the methanol dehydration) allow to obtain the higher yield of DME. The effect of operating conditions (pressure, temperature, ratio H2/CO, time on stream, and catalyst stability) on the CO conversion and yield of DME was studied. The optimal conditions for loading variant 2:1:2 are: the pressure is 30 bar, the temperature is 280 °C and the initial ratio of H2/CO is equal to 2. At that, the CO conversion remains practically constant during 180 h reaction run

Direct synthesis of dimethyl ether from synthesis gas: Experimental study and mathematical modeling

Direct synthesis of dimethyl ether (DME) from syngas, was investigated over a CuO-ZnO-Al2O3 catalyst for methanol synthesis and a γ-Al2O3 catalyst for a methanol dehydration. On the base of mathematical modeling, thermodynamic analysis was carried out in a wide range of pressures (10–100 bar) and temperatures (220–280 °C) for binary mixtures (H2 + CO) with an H2/CO = 1–6 M ratio. The influence of reaction conditions on the equilibrium content of components in the mixture was modelled. The effect of the loading method of catalysts of the methanol synthesis and its dehydration (layerwise loading, mixing) in the DME synthesis in a single reaction step on the CO conversion and the yield of DME was experimentally studied. It has been demonstrated that the layerwise combined loading with the intermediate mixed layer of CuO-ZnO-Al2O3 catalysts of the methanol synthesis and the γ-Al2O3 catalyst for the DME synthesis (2:1:2, ratio parts, i.e. two parts of the catalyst of the methanol synthesis, one part of a mixture of the catalysts and two parts of the catalyst of the methanol dehydration) allow to obtain the higher yield of DME. The effect of operating conditions (pressure, temperature, ratio H2/CO, time on stream, and catalyst stability) on the CO conversion and yield of DME was studied. The optimal conditions for loading variant 2:1:2 are: the pressure is 30 bar, the temperature is 280 °C and the initial ratio of H2/CO is equal to 2. At that, the CO conversion remains practically constant during 180 h reaction run

Application of silica-based sorbents to extraction of rare earth elements from loparite processing products

В России основными источниками редкоземельных элементов (РЗЭ) являются апатит и лопарит. Лопарит – комплексный титанат и ниобат, содержащий до 30 % мас. оксидов РЗЭ преимущественно цериевой группы. Доочистку, групповое разделение, выделение индивидуальных концентратов РЗЭ проводят с применением экстракционных методов, широко используемый для этих целей экстрагент – трибутилфосфат (ТБФ). Экстракционные технологии имеют ряд недостатков, в частности, большое число ступеней разделения из-за невысоких коэффициентов разделения индивидуальных РЗЭ в совокупности с трудностями разделения жидких фаз. Исключить последний недостаток можно при использовании сорбентов, содержащих ТБФ. В качестве носителей можно использовать как органические полимеры, так и неорганические соединения; среди последних широко используется кремнезём, который и был выбран в рамках данного исследования. В статье кратко описана методика синтеза образцов сорбентов. В качестве исходных реагентов для синтеза были использованы тетраэтоксисилан, трибутилфосфат, хлорид олова и нанотрубки. Для синтезированных образцов определен ряд физико-химических свойств (объем пор и их средний диаметр, площадь и морфология поверхности, кислотно-основные свойства поверхности), проведен термогравиметрический анализ. Сорбционные свойства образцов были проверены на примере извлечения РЗЭ из технологических растворов лопарита. В результате получены коэффициенты разделения пар Sm/La до 3,7, Pr/Nd – до 1,8, поэтому потенциально изученные образцы могут быть использованы для выделения самария из суммы РЗЭ, а также для разделения пары Pr-Nd

Structure and phase composition of material based on vanadium alloy V-4.9Ti-4.8Cr and ferrite steel 17Cr-12Ni-Fe

Three-layer materials consisting of the V-4.9Ti-4.8Cr/ferrite steel 17Cr-12Ni-Fe /V-4.9Ti-4.8C