Abstract—The influence of the addition of nanodispersed graphene in an amount of 0.05–0.15 wt

A solution is presented for a non-standard boundary value problem using Laplace’s equation with mixed Dirichlet–Neumann boundary conditions in a two-dimensional element with periodically alternating media that have different conductivities. The distribution of current lines and equipotentials is found for different ratios of media conductivities in the barber-pole structure used in anisotropic magnetoresistive magnetic field sensors.

A study of the radiation-thermal resistance of ferritic steel 16Cr – 4Al – 2W – 0.3Ti – 0.3Y2O3 was made. This ODS (oxide dispersion strengthened) steel is perspective for fusion applications. The “Vikhr” Plasma Focus installation was used to introduse of powerful pulsed flows of helium ions and helium plasma. The power density of a beam of fast helium ions and high-temperature helium plasma flows was ~ 108 and 107 W/cm2 at exposure times of ~ 50 and 100 ns, respectively. The number of pulses N varied in the range from 10 to 30. The rate of evaporation and radiaсtive sputtering changed slightly with an increase in the number of pulses of energy flows acting on the material and amounted to h ≈ 0.01 – 0.02 μm/puls. The irradiated surface after repeated melting under the action of a pulsed radiation-thermal load with powerful energy flows acquired a wave-like character with inclusions of dispersed micro particles of the second phase, containing mainly yttrium, oxygen, aluminum, iron, and titanium. At the same time, in contrast to the refractory metals (W, Mo, Ti) earlier under similar radiation conditions studied, no micro- and macro cracks were formed on the surface of the material facing the plasma. “Vikhr” Plasma Focus setup proved to be an effective tool for simulation testing of candidate materials with magnetic and inertial plasma confinement.

An exact expression is found for the magnetostatic energy of interaction of a synthetic antiferromagnet with a free layer of a spin-tunnel element and ferromagnetic layers in the shape of strongly oblate ellipsoids of revolution. It is established that the exact value of this energy of interaction can differ considerably from the usual value calculated with the expression for a demagnetizing field. The parameters at which the magnetic interaction of a synthetic antiferromagnet is completely compensated are calculated.

A theoretical model of the magnetization distribution is proposed on the basis of an experimentally discovered domain structure and its evolution in an external magnetic field in thin films of FeNiCo composition with uniaxial anisotropy. The analytical dependence of the domain size on the magnitude of the magnetic field is obtained. The change in magnetoresistance because of the evolution of the magnetic domain structure is calculated.

Прямой карбидизацией циркониевого проката в атмосфере смеси газообразных аргона и этилена синтезирован компактный образец стехиометрического карбида циркония ZrC заданной формы. Формирование керамики происходит в результате взаимодействия металла с газообразным этиленом и при поглощении углерода, образующегося на реакционной поверхности при пиролизе С 2 Н 6 . Охарактеризована субструктура керамики, дана оценка механических и проводящих свойств ZrC.

Abstract—The mechanical compressive properties of the materials based on the n-type Bi2Te3–Bi2Se3 (20 mol σ _u^c = 168 MPa (n-type conduction material) and σ _u^c = 133 MPa (p-type conduction material).

Определены кинетические закономерности образования нитридов сплавов Zr–Nb (содержание Nb 0.1, 2.5 и 5 мас. %) при температуре 1900°C. Процесс азотирования характеризуется двухстадийностью, где обе стадии описываются экспоненциальным законом. Скорость химической реакции на второй стадии значительно меньше, чем на первой. Охарактеризован состав формирующихся гетероструктур Zr 1– х Nb х N–ZrN 1– n /β-твердый раствор циркония в ниобии–Zr 1– х Nb х N, установлена последовательность нитридизации компонентов исходного сплава. На первой стадии процесса происходят образование α-твердого раствора азота в Zr и его переход в нестехиометрический нитрид. Кинетическая зависимость на второй стадии описывает нитридизацию фазы β-Nb, образовавшейся при распаде твердого раствора Zr〈Nb〉. Показано, что продолжительность второй стадии процесса определяется количеством ниобия в исходном твердом растворе. Экспериментально подтверждена возможность создания однофазной керамики с активными добавками нитридизацией сплавов Zr–М в одностадийном процессе с сохранением исходной формы металлической заготовки.

We have demonstrated general kinetic aspects of the formation of nitrides of Zr–Nb alloys (containing 0.1, 2.5, and 5 wt

Ceramic nitride samples of tailored composition and shape have been prepared by controlled nitridation of Ti–V metal pairs. We have obtained kinetic and current–voltage curves for the interaction of the Ti–V metal pairs with nitrogen. In different parts of the metal pairs, the nitridation process follows different mechanisms. In the case of the pure metals, the formation of nearly stoichiometric ceramics involves the formation of three- and two-layer graded structures. Nitridation of the junction region, containing a Ti–V solid solution, is determined by the chemical affinity of titanium and vanadium for nitrogen. The formation of titanium nitride leads to decomposition of the Ti–V solid solution in the junction and vanadium metal separation on grain boundaries. The rate of vanadium nitridation increases as the titanium content of the solid solution decreases. The thermoelectric voltage of the Ti–V system in the temperature range from –195.7 to +550°C has been evaluated as a function of the degree of nitridation. The thermoelectric voltage and Seebeck coefficient of metal–ceramic and ceramic structures have been determined as functions of temperature. Characteristically, the thermoelectric voltage of all the nitrided pairs rises monotonically over the entire temperature range studied. Nitrided titanium–vanadium pairs with tailored composition can be used as ceramic thermoelectric converters.

— Compact stoichiometric zirconium carbide (ZrC) with a tailored shape has been synthesized by direct carburization of rolled zirconium metal in an atmosphere of an argon + ethylene gas mixture. Ceramics have been produced by reacting zirconium metal with ethylene gas, through absorption of the carbon released on the reaction surface as a result of C 2 H 6 pyrolysis. We have characterized the microstructure of the ceramics and assessed the mechanical and conductive properties of the synthesized ZrC.

We describe a sequence of structural transformations characterizing high-temperature nitridation of zirconium–niobium alloys containing 0.1–10 wt % niobium. High-temperature saturation of solid solutions of niobium in zirconium with nitrogen is accompanied by decomposition of the Zr〈Nb〉 solid solution and the formation of Zr1 – хNbхN–(ZrN1 – n/β-solid solution of Zr in Nb)–Zr1 – хNbхN composite structures. During nitridation of the heterostructures, zirconium nitride reacts with β-niobium, which is the final step of the nitridation of the parent Zr〈Nb〉 solid solution. Characteristically, the ceramics thus prepared have near-surface porosity reproducing the surface porosity of the as-rolled material.

The new generalized Laplace’s equation for an electric potential is presented, which in the general case, is nonlinear for media with resistance anisotropy caused by the anisotropic magnetoresistance (AMR) effect and determined by the orientation of the magnetization vector relative to the current density vector at an arbitrary point of the sample. The solution to this equation is obtained for an anisotropic medium with a non-uniform distribution of current density and magnetization in the case of an oblique-shaped plate of nanoscale thickness. In addition, the analytical solution was obtained for the current density distribution in such a medium using conformal mapping, which confirms the numerical solution in the case of an isotropic conductor. An analysis of the results showed that the presence of the AMR effect leads to a significant change in the current density distribution in the sample compared to the isotropic case, which is expressed in the deviation of the current density vector in perpendicular to the magnetization vector direction in the plate. It has been established that the presence of an external magnetic field in the film plane, which leads to the emergence of an inhomogeneous magnetization distribution, entails self-organization of the electric current distribution. The graphs of the plate resistance as a function of applied magnetic field demonstrate asymmetry for the cases of the direct and reverse directions of the external magnetic field, which cannot be obtained within the framework of simplified models of current flow in media with the AMR effect.

The change in magnetoresistance upon remagnetization by an external magnetic field is calculated using the model of coherent rotation of the magnetization vector of the free layer of a spin tunnel element subjected to homogeneous strain of tension and compression. It is shown that the conclusions of the theory coincide with the classical experimental.

Ceramics based on hafnium carbide of a given shape have been synthesized by direct carbidization of rolled hafnium in a hydrocarbon atmosphere. Excess carbon resulting from high-temperature pyrolysis of hydrocarbons forms on the surface of ceramic hafnium carbide an easily detachable layer consisting of graphite with an admixture of amorphous carbon. The final formation of ceramics occurs at a temperature of 2400 °C in an atmosphere of an inert gas — argon. The phase composition and structure of the synthesized ceramics are characterized.

Typical experimental dependences of the giant magnetoresistance of a spin tunnel element are compared to theoretical curves obtained using the classical Stoner–Wohlfarth theory of coherent magnetization reversal and a case of incoherent magnetization reversal with the formation of magnetic domains. It is established that the reversal of magnetization through the formation of a domain structure explains the difference between the experimental hysteretic curve and the Stoner–Wohlfarth theory.

A composite material with photocatalytically active properties was obtained by electrophoretic deposition (EP) of highly dispersed anatase on the surface of the carrier. The carrier was a titanium/rutile cermet plate obtained after 2 h of oxidation at 875°C using the oxidative construction approach. During this time, a layer of 15–20 μm of rutile was formed on the titanium plate, which had good adhesion to the surface of the metal core. The breakdown voltage for this sample was ∼150 V. To make the photocatalyst film homogeneous and compact, the deposition was carried out by three cycles of electrophoresis and heat treatment at 395°C. The photocatalytic activity of the obtained samples was studied using the example of the reaction of catalytic decomposition of ozone under the action of ultraviolet radiation.

An analytical solution is obtained for the two-dimensional distribution of the electric potential and current density in an oblique magnetoresistive element using conjugate functions and conformal transformations. Graphs of the dependences of the element’s electrical resistance on an external magnetic field, obtained using the numerical solution to the generalized Laplace equation for an anisotropic magnetoresistive medium, are shown to be asymmetrical.