Search

Crystal-geometrical features of the structure of cast and normalized steel with 0.62 % of C content were studied using EBSD method. Inheritance link between the formation of pearlitic and ferritic-pearlitic structures with the structure of intercrystalline boundaries in cast and normalized steel were demonstrated. It was found that the austenite of cast and normalized steel undergoes plastic deformation in conformity with the mechanisms of sliding, twinning and grain boundary slippage. 72 % of low-angle (3... 15 ºС) and 28% of high-angle (20...60 ºС) intercrystalline boundaries are formed in cast steel. Normalization of cast steel leads to the formation of 23 % low-angle (5...15 ºС) and 77 % high-angle (20...60 ºС) intercrystalline boundaries. After normalization of steel the number of special boundaries Σ3…Σ13 increases from 1% to 7 % comparing to its cast state. The number of special boundaries is approximating the number of proeutectoid ferrite in cast and normalized steel.

The results of studies confirming the feasibility of using low-carbon steels for the manufacture of hot deformation tools of the metal are given. These steels have high heat resistance under thermal cycling conditions with water rapid cooling. The efficiency of alloying of steel depends on the type of tool and its working conditions. The developed heat treatment significantly increase the tool life of low-carbon alloyed steels under working conditions.

A combined microscopic, i.e., powder and single crystal x-ray diffraction and inelastic x-ray scattering, and macroscopic, i.e., heat capacity, characterization was carried out on YB 66 between 10 and 400 K. The system crystallizes in a rather large unit cell with a lattice parameter of about 23.4 Å at room temperature. The volume thermal expansion coefficient is found to be 3.9 × 10 − 5 K − 1 at 295 K. A high Debye temperature above 1000 K was determined using several methods, 1043 (25) K , from heat capacity measurements, 1430 (59) K , from elastic constants measurements, and 1690 (198) K , from thermal expansion measurements. The thermal transport is modeled as a collection of Einstein oscillators with an Einstein temperature of 194 (2) K. The C 11 and C 44 elastic constants are above 400 and 150 GPa , respectively. The average speed of sound in YB 66 is estimated to be 9631 (380) m / s , similar to the average speed of sound in corundum, 10 000 m / s. The large volume of the unit cell and the stiffness of the crystal structure make YB 66 a promising candidate for high-resolution x-ray monochromatization applications. Candidate reflections for high-resolution resonant inelastic x-ray scattering are indicated and potential pitfalls relevant to the quality of crystals and multi-beam cases are mentioned. [ABSTRACT FROM AUTHOR]

Prospects for the use of manganites in various areas of modern technologies require comprehensive studies of their physical and chemical properties. La0.9Mn1.1O3 (LMO) ceramics have been synthesized at an annealing temperature tann of 1150 °C with further post-annealing at 1250, 1350, and 1450 °C. As tann increases, the structure symmetry changes, and both the crystallite size and chemical defects increase. The post-annealing, on one hand, leads to a dramatic reduction of the magnetocaloric effect (MCE) ‖−ΔS maxM ‖ from 3.50 to 0.75 J (kg K)−1 at 2 T and a Curie temperature TC from 227 to 113 K with increasing tann. On the other hand, an external hydrostatic high-pressure P works oppositely enhancing ferromagnetic interactions. The saturation of −ΔS maxM and TC is already achieved at a relatively low P of ≈ 0.4 GPa. LMO-1150 exhibits the best magnetocaloric characteristics compared with other studied samples. Moreover, the electrochemical characteristics of the LMO materials as electrocatalysts for overall water splitting (OER process) and features of their transformation in different 0.5 M K2SO4, 0.5 M K2HPO4, and 0.1 M K2B4O7 electrolytes have been studied thoroughly. After electrocatalysis of LMO, the magnetization M decreases and TC remains, which makes it possible to control the depletion of electrodes and predict their working time based on the magnetic measurements. All samples show the best OER activity in the 0.5 M K2HPO4 media. The obtained results demonstrate the ways for controlling the MCE of LMO under changing internal and external conditions, and an evaluation of the possibilities for their OER applications in electrocatalysts. [ABSTRACT FROM AUTHOR]

Copyright of Progress in Physics of Metals / Uspehi Fiziki Metallov is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The results of a study of magnetoactive elastomers (MAEs) consisting of an elastomer matrix with embedded ferromagnetic particles are presented. A continuous critical bending induced by the magnetic field, characterized by a critical exponent for the bending magnitude, and the derivative of which has a singularity in the critical region is reported for the first time. The mechanical stability loss and the symmetry reduction of the magnetic state, which are interrelated with each other, take place at the critical point. The magnetization in the high-symmetric state (below the critical point) is directed along the magnetic field and the torque is absent. Above the critical point, the magnetization and the magnetic field are noncollinear and there arises a torque, which is self-consistent with the bending. The magnetic field dependence of the MAE bending was found to have a hysteresis, which is associated with the magneto-rheological effect. The shape memory effect was also obtained for the MAE bending in a cycle consisting of magnetization, cooling (at H ≠ 0), and heating (at H = 0). The influence of the critical glass transition temperature of the matrix, as well as its melting/solidification temperature, on the magnetic shape memory effect was studied. [ABSTRACT FROM AUTHOR]

Manganites are multifunctional materials which are widely used in both technology and devices. In this article, new prospects of their use as nanoparticles for various types of applications are demonstrated. For that, the ferromagnetic nanopowder of La0.6Sr0.4MnO3 has been synthesized by the sol–gel method with a subsequent annealing at 700–900 °C. The crystal structure, phase composition and morphology of nanoparticles as well as magnetic, magnetothermal and electrocatalytic properties have been studied comprehensively. The critical sizes of superparamagnetic, single-domain, and multi-domain states have been determined. It has been established that an anomalously wide temperature range of magnetocaloric properties is associated with an additional contribution to the magnetocaloric effect from superparamagnetic nanoparticles. The maximum values of the specific loss power are observed in the relaxation hysteresis region near the magnetic phase transition temperature. The electrochemical stability and features of the decomposition of nanoparticles in 1 M KOH and Na2SO4 electrolytes have been determined. A decrease in the particle size contributes to an increase in electrocatalytic activity for overall water splitting. Magnetocaloric and electrocatalytic results of the work indicate the prospects for obtaining the possibility of changing the temperature regime of electrocatalysis using contactless heating or cooling. [ABSTRACT FROM AUTHOR]

It was found that the anomalous magnetorheological effect observed in initially unstructured magnetoisotropic magnetoactive elastomers, i.e., the growth of their effective shear modulus in an external magnetic field by almost two orders of magnitude, is a result of the uniaxial magnetic anisotropy induced by the magnetic field. An additional magnetoelastic contribution to the mechanical stress created by the induced magnetic anisotropy counteracts the shear and increases the effective shear modulus of the magnetoactive elastomer when the latter is magnetized. Numerical estimates made for the magnitude of magnetorheological effect are in good agreement with known experimental data. [ABSTRACT FROM AUTHOR]

We present the study of the local structure and magnetic inhomogeneity of nano-sized La0.7Sr0.3MnO3 manganites performed by x-ray absorption fine structure (XAFS) spectroscopy and nuclear magnetic resonance (NMR). Nano-powders with particle size of 50-200 nm (NP1) and 20 nm (NP2), and bulk samples (BS) were studied. EXAFS data show the difference between the local structure of core and outer shell of the nano-particle. The data evidenced that the shell of particles presents the disordered crystalline array. According to the NMR, at low temperature the magnetic state of NP1 sample is homogenous. However, with increase of temperature the two ferromagnetic phases, with strong and weakened double exchange, coexist. The NP2 powder is magnetically homogeneous and characterized by weakened double exchange at all temperatures of the existence of the magneto-ordered state. The results specify on possible existence of characteristic spatial scale below which the phase stratification becomes energetically unfavorable. [ABSTRACT FROM AUTHOR]

The influence of hydrostatic pressure, up to 1.2 GPa, on the spin transition behavior in [Fe(phen)2(NCS)2] polymorph II and [CrI2(depe)2] is investigated. As both are mononuclear spin crossover (SCO) systems, they show similar (abrupt) spin transition properties at atmospheric pressure despite the differences in the chemical coordination sphere.

Electron paramagnetic resonance (ESR) study of La[sub 0.7]Ca[sub 0.3-x]Ba[sub x]MnO[sub 3] manganites (x = 0; 0.15; 0.3) is presented. Experimentally observed exponential decreasing of line intensity on temperature is in agreement with the deduced one and indicates the spin-lattice relaxation in manganites near the Curie temperature T[sub c]. The obtained dependence of ESR linewidth on the x value shows the decreasing of strength of spin-lattice interaction with the increasing of T[sub c] (caused by the increasing of the x value). [ABSTRACT FROM AUTHOR]