Bulletin of the Russian Academy of Sciences: Physics最新文献

We studied the evolution of the phase composition of laser welded joints before and after heat treatment of 3rd generation Al–Li alloys using synchrotron radiation. The article demonstrates the fundamental role of the alloying elements of copper and lithium in formation of the phase composition of the fusion zone of the weld. It has been established that laser exposure changes the phase composition of the alloy. Namely, low copper contents mainly lead to formation of T₂(Al₆CuLi₃) and T₃(Al₅CuLi₃) phases, the average copper contents form T₁(Al₂CuLi), T₂(Al₆CuLi₃), T₃(Al₅CuLi₃) phases and the presence of high copper contents results in formation of T₁(Al₂CuLi) phase at the boundaries of dendrite. Post-heat treatment restores the initial phase composition in the fusion zone. As for the solid solution, the δ'(Al₃Li) phase is formed at low copper contents, the δ'(Al₃Li) and T₁(Al₂CuLi) phases are formed at average copper contents, and T₁(Al₂CuLi) phase is observed at high copper contents. Consequently, this makes it possible to improve the mechanical properties of weld joint specimens to match the numbers of the initial alloy.

X-ray diffraction on synchrotron radiation was used to analyze kidney stones as part of phantom objects simulating the patient’s body. The radiation photon energies were 33.7, 67 and 112 keV. It has been shown that the use of synchrotron monochromatic radiation with photon energy E ≥ 67 keV allows one to reliably identify the mineral composition of uroliths. The shift to a higher photon energy range can significantly reduce the radiation load on patients during diagnosis. The patient’s weight factor also becomes less critical.

The structure, magnetic properties and ferromagnetic resonance curves of cobalt ferrite particles synthesized by chemical coprecipitation technique have been studied. The possibility of resonant heating of powder in a magnetic anisotropy field of particles is shown, which can find application in medicine for magnetic hyperthermia.

We considered a domain wall as a structure which shifts the phase of a propagating spin wave under the condition of applied electric field by means of an inhomogeneous magnetoelectric coupling. The result is that the electrically induced transition of the Bloch domain wall into the Néel domain wall changes the phase of spin wave passed through the domain wall by nearly 180°.

Concentration and angular dependences of the parameters (line width and position) of ferromagnetic resonance (FMR) for CoTaNb/MgO composite films with metal alloy concentrations x = 0.27–0.72 were obtained in the work. Granular, granular-percolation structure and zigzag stripe magnetic structure for films with different x were detected. An increase in the FMR parameters with an increase in the angle from 0° to 90° between the constant magnetic field and the film plane with different x was observed. It was shown in the work that the behavior of the angular dependences strongly depends on the magnetic structure of the films, which have the greatest change in the region of transition from granular to granular-percolation structure with extended magnetic metallic microregions. The FMR method is a structure-sensitive method for scientific studies of the electromagnetic properties of thin magnetic composite films with granular and percolation structures and their combinations was demonstrated.

As a part of the first-stage experimental stations at the SKIF Center for Shared Use, a unique station 1–3 “Fast Processes” is being created, designed to study detonation, shock wave processes, as well as processes of reaction of materials to pulsed thermal or mechanical influence. The station will include three sections: the “Plasma” section, designed to study the processes of reaction of materials to pulsed thermal and mechanical loads; section “Dynamic processes, main building”, which is supposed to study shock wave processes and section “Dynamic processes, separate building”, intended for studying detonation and shock wave processes. To conduct experiments at stations 1–3, five coordinate X-ray detectors of various types are being developed. We described in detail the characteristics of the detectors and the status of development.

We studied the magnetic properties of Co₇₃Fe₄Si₁₂B₁₁ ferromagnetic microwires in initial amorphous and crystalline state achieved by thermal treatment with direct current. A microwire in amorphous state is found to be characterized with quasilinear hysteresis loop with small coercive force less than 0.05 kA/m. Once crystallized, the microwire loses its soft magnetic properties, its hysteresis loop radically expands, and the coercive force becomes equal to 15 kA/m.

The authors study diffractive optical elements manufactured via contact printing on a dichromated gelatin and direct laser writing on photoresist. The elements modify the point-spread function for three-dimensional super resolution fluorescence microscopy. It is shown that both elements produce two-lobed rotating light fields that can be used for three-dimensional nanoscopy. Results from the subdiffractive localization of fluorescent labels are presented, and the accuracy of coordinate reconstruction is determined.

Differential scanning calorimetry (DSC) is used to study the phase transformations of four amorphous metal alloys based on transition metals Fe and Ni with additives of Si and C. The temperature dependences of the heat flux upon phase transformations are measured along with changes in the mass and specific heat capacity of amorphous alloys. Two phase transformations associated with the temperature of glass transition and complete crystallization are identified. The relative volume of the crystalline fraction of alloys heated to 1000°C is calculated. It is concluded there are nanocrystalline phases between the first and second phase transitions at heating rates of 0.1°C/s.

Confocal optical microscopy data with a resolution of 1 μm on the spatial heterogeneity of a vitrified film prepared from a melt powder of an anisometric europium(III) β-diketonate complex are presented. It has been shown that the heterogeneity caused by crystalline inclusions in the amorphous structure of the film, leads to a temperature memory effect, when the film can be in different states at the same temperature.