The effect of the chromium concentration on the magnetic properties of Fe–Cr precursors for hard-magnetic Fe–Cr–Co materials is studied. Nitrogen used as a sintering atmosphere and a long annealing time enhance are found to increase the coercive force H c of the materials. The phase formation in Fe–30% Cr alloys is traced during heat treatment in nitrogen and argon atmosphere using thermal analysis.

The structure and physical properties of natural sphalerites and galena from the Dal'negorsk ore massif were investigated. A nonlinear temperature dependence of the unit-cell parameters of sphalerite in the range 80-300 K was established by X-ray diffraction. The microstructure and elemental composition of sphalerites with different iron contents were studied. The results show that an increase in iron content in sphalerite solid solution leads to an increase in the unit-cell parameters. It is found that sphalerites are insulators in the temperature range from 4 to 300 K, as their absolute electrical resistivity is greater than 1 MOhm.m. The temperature dependence of sphalerite magnetization has a peak corresponding to the mineral transition from antiferromagnetic to ferrimagnetic state with a Neel temperature of about 90 K in fields of 0, 0.15, and 1.00 T. The magnetic state of natural galena is due to a sphalerite impurity: The extrema in the temperature magnetization curve are typical of sphalerite. (C) 2017, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.

Physicochemical features of the YBa2Cu3O6 + δ superconductor synthesized via ceramic route and subjected to a kind of modification by long-term exposure to an atmosphere with low pH2O have been studied by X-ray diffraction, thermal analysis, and magnetometry. The resulting material had a high degree of saturation with air components at room temperature and 30% humidity, up to 1.5 wt % in 30 days, which is not inherent in YBa2Cu3O6 + δ.

A comparative analysis of the thermal and magnetic properties of synthesized samples of troilite (FeS) and hexagonal (Fe0.94S) and monoclinic (Fe0.875S) pyrrhotites was performed by X-ray diffraction, combined thermogravimetric analysis and calorimetry, and thermomagnetic measurements. The pyrrhotite composition affects the temperatures and heats of phase transitions of the samples during heating and cooling in the range of 300–670 K. The temperature and the magnetic field strength determine the magnetization of pyrrhotites. Higher magnetization is inherent in monoclinic pyrrhotite, while troilite has lower magnetization.

Методами рентгенографии, совмещенного термогравиметрического анализа и калориметрии, а также термомагнитных измерений проведен сравнительный анализ термических и магнитных свойств синтезированных образцов троилита (FeS), гексагонального (Fe0.94S) и моноклинного (Fe0.875S) пирротинов. Составы пирротинов влияют на температуры и теплоты фазовых переходов образцов при нагревании и охлаждении в интервале 300–670 К. Температура и напряженности магнитного поля определяют намагниченность пирротинов. Установлено, что большей намагниченностью обладает моноклинный пирротин, меньшей – троилит.

The magnetic properties of a synthetic sample of Fe0.94S pyrrhotine with the hexagonal crystal structure have been studied in the temperature range of 4–300 K. It has been found that the temperature dependence of magnetization has maxima in the temperature ranges of 30–35 and 122–133 K, which are explained by the Verwey-type transitions.

Statistically significant correlations between physical and mechanical properties of sintered specimens of iron with a wide range of impurity concentrations in the initial powder are determined. The saturation magnetization of the specimens increases linearly upon growth in the density; the coercivity decreases linearly upon growth in the ultimate bending strength. The correlation between the resistivity and the ultimate bending strength obeys a hyperbolic law.

Исследованы магнитные свойства поликристаллических образцов малоникелистого природного пирротина и синтезированных пирротинов составов Fe0.675Ni0.200S и Fe0.475Ni0.400S. Показано, что все исследуемые пирротины обладают температурным магнитным гистерезисом в области 298–623 К. В результате этого не только повышается различие в значениях магнитного момента материалов после режима нагрев–охлаждение, но и изменяется их магнитное состояние.

The magnetic properties of polycrystalline natural pyrrhotite samples with low-nickel contents and synthesized Fe0.675Ni0.2S and Fe0.475Ni0.4S pyrrhotites are investigated. All of the investigated pyrrhotites are shown to have a thermal magnetic hysteresis in the region of 298–623 K. As a result, there is not only an increase in the difference between the magnetic moment values of the materials after a heating-cooling regime, but also a change in their magnetic state.

Magnetic, electrical, and mechanical properties as well as the structure of Fe-Co powder materials are investigated. It is found that the structural rearrangement from the BCC solid solution of Co in α-Fe (α phase) to the HCP solid solution of Fe in α-Co (ɛ phase) takes place with the increase in Co content. There are nonequilibrium mixtures of these phases in areas of intermediate composition containing residual oxides present in the initial Co powder.

The effect of doping on the temperature evolution of the crystal structure of the YBa2Cu3O y high-temperature superconductor has been investigated. The crystal structure of Y1 − x Ca x Ba2Cu3Oy (x = 0, 0.1; y = 6.6, 6.8, 6.95) has been studied using the full-profile analysis with X-ray powder diffraction data in the temperature range 100–300K. The unit cell parameters, the bond lengths, and the calculated linear and volume coefficients of thermal expansion are characterized by a nonmonotonic behavior in the temperature range ∼160–225 K. Samples with the oxygen content y = 6.6–6.8 in both systems (with x = 0 and 0.1) have negative linear coefficients of thermal expansion at low temperatures. A possible reason for the anomalous behavior can be the change in the state of the electronic subsystem. The data analysis confirms that the doping mechanisms upon oxygen introduction, and when Y is substituted for Ca are different.

The mechanisms of formation of NdSr 2− x Ca x Mn 2 O 7 (0 ≤ x ≤ 2.0) solid solution have been studied. The dependence of its volume magnetic susceptibility on the calcium concentration is obtained. The stability of this solid solution is compared with that of similar solid solutions in lanthanum-containing systems.

Complex investigation of the physical properties and structure of sintered powder materials of the Fe-Si system after grinding of a mixture of powders in two different mechanical aggregates has been performed. It is shown that fragmentation of powders in both a BW-micro vibration grinder and in a Fritsch-type centrifugal planetary mill leads to a nonmonotonic change in the properties of sintered materials. This result is explained by mechanical activation of powders during grinding.

The integrated study of the structure and magnetic, electrical, and mechanical properties of the Fe-Si powder materials in a range of silicon concentrations 0–12 wt % showed that the dependence of all physicomechanical properties of these materials on the silicon content was related to the sequence of the formation of the disordered silicon solution in iron, ordered solution, and the Fe 3 Si phase.

The effect of the sintering atmosphere on the structure and physical properties of magnetically soft Fe-P powder materials was studied. It is shown that the structure-sensitive properties of the magnetic materials sintered in a nitrogen-hydrogen mixture (96% N-2 + 4% H-2) are higher than those of the materials sintered in a hydrogen atmosphere. This is due to the formation of a structure with a higher grain size and a uniform pore-size distribution.

Magnetic, electrical, and mechanical measurements have been made on specimens made by liquid-phase and solid-phase sintering of iron and copper powders over wide concentration ranges. A study is made on the scope for using magnetic and electrical parameters for nondestructive testing of Fe-Cu system material quality.

The effect of impurities in the iron powder on the physical properties of sintered magnetically soft materials was studied. Although vanadium increased the coercive force, it improved properties such as the saturation magnetization, specific electrical resistance, and hardness. The coercive force and bend strength of the powder materials were linearly dependent on the amount of carbide-forming elements. Phosphorous decreased this undersirable effect. Increasing the fraction of carbide forming elements in the materials decreased their densities, and increased their specific electrical resistances, phosphorous being unable to change this dependence.