Institute of Physics. HI Amirkhanova

Currently, there is an ever-growing interest in carbon materials with increased deformation-strength, thermophysical parameters. Due to their unique physical and chemical properties, such materials have a wide range of applications in various industries. Many prospects for the use of polymer composite materials based on polyvinylidene fluoride (PVDF) for scientific and technical purposes explain the plethora of studies on their characteristics "structure-property", processing, application and ecology which keep appearing. Building a broader conceptual picture of new generation polymeric materials is feasible with the use of innovative technologies; thus, achieving a high level of multidisciplinarity and integration of polymer science; its fundamental problems are formed, the solution of which determines a significant contribution to the natural-scientific picture of the modern world. This review provides explanation of PVDF advanced properties and potential applications of this polymer material in its various forms. More specifically, this paper will go over PVDF trademarks presently available on the market, provide thorough overview of the current and potential applications. Last but not least, this article will also delve into the processing and chemical properties of PVDF such as radiation carbonization, β-phase formation, etc.

The structure and key functional properties of a promising lead-free solid solution, BiFeO₃–BaTiO₃, have been optimised by controlling chemical homogeneity <italic>via</italic> La-substitution strategies and thermal treatment.

Direct measurements of the magnetocaloric effect in samples of rapidly quenched ribbons of Mn50Ni40In10 and Ni50Mn37Sn13 Heusler alloys with potential applications in magnetic refrigeration technology are carried out. The measurements were made by a precise method based on the measurement of the oscillation amplitude of the temperature in the sample while is subjected to a modulated magnetic field. In the studied compositions both direct and inverse magnetocaloric effects associated with magnetic (paramagnet-ferromagnet-antiferromagnet) and structural (austenite-martensite) phase transitions are found. Additional inverse magnetocaloric effects of small value are observed around the ferromagnetic transitions.

Polymer-based magnetoelectric composite materials have attracted a lot of attention due to their high potential in various types of applications as magnetic field sensors, energy harvesting, and biomedical devices. Current researches are focused on the increase in the efficiency of magnetoelectric transformation. In this work, a new strategy of arrangement of clusters of magnetic nanoparticles by an external magnetic field in PVDF and PFVD-TrFE matrixes is proposed to increase the voltage coefficient (αME) of the magnetoelectric effect. Another strategy is the use of 3-component composites through the inclusion of piezoelectric BaTiO3 particles. Developed strategies allow us to increase the αME value from ~5 mV/cm·Oe for the composite of randomly distributed CoFe2O4 nanoparticles in PVDF matrix to ~18.5 mV/cm·Oe for a composite of magnetic particles in PVDF-TrFE matrix with 5%wt of piezoelectric particles. The applicability of such materials as bioactive surface is demonstrated on neural crest stem cell cultures.

The possibility of the formation of high entropy single-phase perovskites using solid-state sintering was investigated. The BaO–SrO–CaO–MgO–PbO–TiO2, BaO–SrO–CaO–MgO–PbO–Fe2O3 and Na2O–K2O–CaO–La2O3–Ce2O3–TiO2 oxide systems were investigated. The optimal synthesis temperature is found between 1150 and 1400 °C, at which the microcrystalline single phase with perovskite structure was produced. The morphology, chemical composition, crystal parameters and dielectric properties were studied and compared with that of pure BaTiO3. According to the EDX data, the single-phase product has a formula of Na0.30K0.07Ca0.24La0.18Ce0.21TiO3 and a cubic structure.

The magnetocaloric effect (MCE) in an Fe48Rh52 alloy and Sm0.6Sr0.4MnO3 manganite was studied in cyclic magnetic fields. The adiabatic temperature change in the Fe48Rh52 alloy for a magnetic field change (ΔB) of 8 T and a frequency (f) of 0.13 Hz reaches the highest value of (ΔTad) of −20.2 K at 298 K. The magnitude of the MCE in Sm0.6Sr0.4MnO3 reaches ΔTad = 6.1 K at the same magnetic field change at 143 K. The temperature regions, where a strong MCE is exhibited in an alternating magnetic field, are bounded in both compounds. In the case of the Fe48Rh52 alloy, the temperature range for this phenomenon is bounded above by the ferromagnetic to antiferromagnetic transition temperature in the zero field condition during cooling. In the case of the Sm0.6Sr0.4MnO3 manganite, the temperature range for the MCE is bounded below by the ferromagnetic-paramagnetic transition temperature in zero field during heating. The presence of these phase boundaries is a consequence of the existence of areas of irreversible magnetic-field-induced phase transitions. It is found that the effect of long-term action of thousands of cycles of magnetization/demagnetization degrades the magnetocaloric properties of the Fe48Rh52 alloy. This can be explained by the gradual decrease in the size of the ferromagnetic domains and increasing role of the domain walls due to giant magnetostriction at the ferromagnetic to antiferromagnetic transition temperature. The initial magnetocaloric properties can be restored by heating of the material above their Curie temperature.

Experimental data on the effect of grain sizes on the shape and width of the hysteresis loop characterizing a metal-semiconductor phase transition in vanadium dioxide films are analyzed in terms of the classical theory of nucleation. It is shown that the factors responsible for the changes in the shape and width of the hysteresis loop with variations in the size of the grains making up a film are associated with the heterogeneous character of nucleation of a new phase, on the one hand, and with the elastic stresses arising in the phase transition, on the other.

The reduction procedure for the general coupled nonlinear Schrödinger (GCNLS) equations with four-wave mixing terms is proposed. It is shown that the GCNLS system is equivalent to the well known integrable families of the Manakov and Makhankov U(n,m)-vector models. This equivalence allows us to construct bright-bright and dark-dark solitons and a quasibreather-dark solution with unconventional dynamics: the density of the first component oscillates in space and time, whereas the density of the second component does not. The collision properties of solitons are also studied.

Creating stimulus-sensitive smart catalysts capable of decomposing organic dyes with high efficiency is a critical task in ecology. Combining the advantages of photoactive piezoelectric nanomaterials and ferroelectric polymers can effectively solve this problem by collecting mechanical vibrations and light energy. Using the electrospinning method, we synthesized hybrid polymer-inorganic nanocomposite fiber membranes based on polyvinylidene fluoride (PVDF) and bismuth ferrite (BFO). The samples were studied by scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), total transmittance and diffuse reflectance, X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), vibrating-sample magnetometer (VSM), and piezopotential measurements. It has been demonstrated that the addition of BFO leads to an increase in the proportion of the polar phase from 86.5% to 96.1% due to the surface ion-dipole interaction. It is shown that the composite exhibits anisotropy of magnetic properties depending on the orientation of the magnetic field. The results of piezo-photocatalytic experiments showed that under the combined action of ultrasonic treatment and irradiation with both visible and UV light, the reaction rate increased in comparison with photolysis, sonolysis, and piezocatalysis. Moreover, for PVDF/BFO, which does not exhibit photocatalytic activity, under the combined action of light and ultrasound, the reaction rate increases by about 3× under UV irradiation and by about 6× under visible light irradiation. This behavior is explained by the piezoelectric potential and the narrowing of the band gap of the composite due to mechanical stress caused by the ultrasound.

The results of direct studies of the magnetocaloric effect (MCE) of the Ni47Mn40Sn12.5Cu0.5 Heusler alloy in cyclic magnetic fields are presented. It is shown that in cyclic magnetic fields, the MCE value near the magnetostructural phase transition depends on the rate of temperature scanning. A higher rate of change in the sample temperature causes the MCE to have a greater value. The observed effect is explained by irreversible phase transition, induced by a magnetic field, from a low-symmetry martensitic phase to a high-symmetry austenitic phase. Moreover, it is observed only within the temperature hysteresis loop of the magnetostructural phase transition. Such materials, despite the considerable MCE values under a single application of the magnetic field, are unpromising due to a strong change in the magnetocaloric properties in cyclic magnetic fields.

The magnetocaloric effect has been measured in manganites of various chemical compositions in weak alternating magnetic fields. The capabilities of a simple method for measuring the magnetocaloric effect by modulating the magnetic field have been demonstrated. The dependence of the magnetocaloric effect on the temperature, magnetic field, and chemical composition of samples is interpreted.

In this report, we present results of the direct measurements of the adiabatic temperature change in MnAs1−xPx compounds (x = 0, 0.02, 0.025, and 0.03) in cyclic magnetic fields up to 8 T. The substitution of As by P results in a slight shift of the Curie temperature and more notable change in the magnetocaloric effect (MCE) value. Estimations of the lattice and magnetic contributions show that in the MnAs compound, the lattice contribution dominates (about 70% of the total MCE). Substitution of As with phosphorus leads to a decrease in the total value of the MCE, which is caused by a decrease in the lattice contribution, and the magnetic contribution almost does not change in the absolute value. A reversible degradation of the magnetocaloric effect in cyclic magnetic fields is found, which restricts the application of this material to the magnetic cooling technology.

A series of phase separated La0.5Ca0.5MnO3 manganite samples with different grain sizes were studied by ac susceptibility, direct magnetocaloric effect (ΔT), and heat capacity measurements. The ac susceptibility shows that fractions of ferromagnetic and antiferromagnetic phases and consequently the phase separated state can be controlled by means of sintering temperature. Lower sintering temperature leads to a ferromagnetic state, while higher sintering temperature increases antiferromagnetic phase fraction, resulting in a phase separated state. In the phase separated samples, ΔT shows a conventional positive peak near TC and an anomalous positive peak at lower temperature near TN. The anomalous positive peak appears at higher magnetic field and is accompanied with thermal hysteresis. It is suggested that the anomalous magnetocaloric behaviors result from phase separation and first order magnetostructural phase transition. This study shows that direct magnetocaloric effect is a useful technique for the study of manganites.

The effect of 16О → 18О isotope substitution on specific heat and magnetocaloric effect of polycrystalline La0.7Ca0.3MnO3 manganite is studied. Mainly the effect of isotope substitution for the specific heat and magnetocaloric effect is only the reduction of temperatures of anomalies. ΔTad values at magnetic field change ΔH = 18 kOe are equal to ΔTad = 2.41 K and 2.60 K for La0.7Ca0.3Mn16O3 (LCMO16) and La0.7Ca0.3Mn18O3 (LCMO18), respectively. The sandwich of the LCMO16 and LCMO18 samples was produced for direct measurement of ΔTad. The use of sandwich from materials with near similar magnetocaloric properties increases the relative cooling power by about 20%.

This paper presents the results of the synthesis of samarium-doped bismuth ferrite (BFO) nanoparticles by the solution combustion method. The dependence of BFO properties on the amount of the samarium (Sm) in the composition was studied. The synthesized nanocomposites were characterized by scanning electron microscopy SEM), X-ray diffractometry (XRD), Raman, Electron Diffuse Reflectance Spectroscopy (EDRS) and Electron Magnetic Resonance (EMR). The photocatalytic (PC) measurements showed the absence of a strict correlation between the PC activity and the crystallite size and band gap. An increase in the PC activity of BFO samples with 10 and 15% doping was observed and it was concluded that in controlling the PC properties in doped BFO, the processes of interfacial polarization at the boundaries of the morphotropic phase transition are of decisive importance. It was supposed that the internal electric field formed at these boundaries contributes to the efficient separation of photogenerated charge carriers.

The effect of the conditions of synthesis and of the substrate material on the metal-semiconductor phase transition in thin vanadium dioxide films prepared using laser ablation has been studied. The broadening of the hysteresis loop is shown to be due to a decrease in the size of the crystal grains making up the film. Conjectures are put forward to explain the formation of asymmetric hysteresis loops.

The coupling between electric, magnetic and elastic features in multiferroic materials is an emerging field in materials science, with important applications on alternative solid-state cooling technologies, energy harvesting and sensors/actuators. In this direction, we developed a thorough investigation of a multiferroic composite, comprising magnetocaloric/magnetostrictive Gd[Formula: see text]Si[Formula: see text]Ge[Formula: see text] microparticles blended into a piezo- and pyroelectric poly(vinylidene) fluoride (PVDF) matrix. Using a simple solvent casting technique, the formation and stabilization of PVDF electroactive phases are improved when the filler content increases from 2 to 12 weight fraction (wt.%). This effect greatly contributes to the magnetoelectric (ME) coupling, with the ME coefficient [Formula: see text] increasing from 0.3 V/cm.Oe to 2.2 V/cm.Oe, by increasing the amount of magnetic material. In addition, magnetic measurements revealed that the ME-coupling has influenced the magnetocaloric effect via a contribution from the electroactive polymer and hence leading to a multicaloric effect. These results contribute to the development of multifunctional systems for novel technologies.

In this research, green synthesized MgONPs from lemon fruit extracts and their fungicidal potential was evaluated against Alternaria dauci infection on carrot (Daucus carota L.) under greenhouse conditions.The scanning and transmission electron microscopy (SEM, TEM) and ultra-violet (UV) visible spectroscopy were used to validate and characterize MgONPs. The crystalline nature of MgONPs was determined using SAED (selected area electron diffraction). MgONPs triggered substantial antifungal activity against A. dauci when exposed to 50 and 100 mg L−1 concentrations but the higher antifungal potential was noticed in 100 mg L−1 under in-vitro conditions. In fungal inoculated plants, a marked decrease in growth, photosynthetic pigments, and an increase in phenol, proline contents, and defense-related enzymes of carrot were seen over control (Distilled water). However, foliar application of MgONPs at 50 and 100 mg L−1 resulted in significant improvement of plant growth, photosynthetic pigments, phenol and proline contents, and defense enzymes activity of carrots with and without A. dauci infection. Spraying of MgONPs at 100 mg L−1 had more plant length (17.11%), shoot dry weight (34.38%), plant fresh weight (20.46%), and root dry weight (49.09%) in carrots when challenged with A. dauci over inoculated control. The leaf blight indices and percent disease severity were also reduced in A. dauci inoculated plants when sprayed with MgONPs. The non-bonding interactions of Alternaria genus protein with nanoparticles were studied using molecular docking.

The effect of quenched nonmagnetic impurities on the phase transitions in the three-dimensional Potts model with the number of spin states q = 4 for the case of the simple cubic lattice is studied using the Monte Carlo method. The phase transitions in this model are studied for spin density p ranging from 1.0 to 0.70. The position of the tricritical point at the phase diagram is determined.

The cyclability and frequency dependence of the adiabatic temperature change (ΔTad) under an alternating magnetic field (AMF) are significantly important from the viewpoint of refrigeration application. Our studies demonstrated, by direct measurements, that the cyclability and low-magnetic-field performance of ΔTad in FeRh alloys can be largely enhanced by introducing second phases. The ΔTad under a 1.8 T, 0.13 Hz AMF is reduced by 14%, which is much better than that (40–50%) of monophase FeRh previously reported. More importantly, the introduction of second phases enables the antiferromagnetic–ferromagnetic phase transition to be driven by a lower magnetic field. Thus, ΔTad is significantly enhanced under a 0.62 T, 1 Hz AMF, and its value is 70% larger than that of monophase FeRh previously reported. Although frequency dependence of ΔTad occurs, the specific cooling power largely increases by 11 times from 0.17 to 1.9 W/g, as the frequency increases from 1 to 18.4 Hz under an AMF of 0.62 T. Our analysis of the phase transition dynamics based on magnetic relaxation measurements indicates that the activation energy barrier is lowered owing to the existence of second phases in FeRh alloys, which should be responsible for the reduction of the driving field. This work provides an effective way to enhance the cyclability and low-magnetic-field performance of ΔTad under an AMF in FeRh alloys by introducing second phases.