Solid State Phenomena Vol. 312

Abstract: A comprehensive study of the structure and phase composition, magnetostrictive and magnetic properties of the (Sm_0.5R_0.5)Fe₂ (R = Gd, Tb) compounds was performed. The effect of partial replacement of samarium by gadolinium and terbium on the microstructure of the surface, the temperature of phase transitions, the magnitude of magnetostrictive deformations and magnetization was studied. Using atomic force and magnetic force microscopy, the surface topology at the micro and nanoscale was established, and information on the magnetic domain structure at room temperature was obtained.

Abstract: A theoretical study was made of the dependence of the blocking temperature of the core/shell system of nanoparticles on the intensity of their magnetostatic interaction. It is shown that with an increase in the concentration of nanoparticles (intensity of the magnetostatic interaction), the blocking temperature increases. Moreover, the of large nanoparticles changes more significantly.

Abstract: An understanding of the magnetic properties in an amorphous alloy requires comprehensive studies of magnetic anisotropy at various scales. In this paper such a study is carried out using amorphous ribbons FeCuNbSiB. The magnetic anisotropy associated with the rolling axis of ribbons does not affect hysteresis loop measurements, but the disappearance of a fingerprint-like pattern in the domain structure occurs in different fields when they are applied along and transverse the rolling axis. A correlation between the local magnetic anisotropy constant and the nanoscale within which the local easy axis is ordered was found.

Abstract: We utilize the Metropolis algorithm to obtain statistical averages of the domain wall length in a FePt granular structure after remagnetization is performed by an ultrashort polarized laser impulse. We propose and check the cluster-size-based order parameter, which along with magnetization, shows the domain wall length, and as a consequence, the average cluster size in the system. We treat the inverse Faraday effect as an external directed magnetic field and show impulse time- and laser power- dependent estimates within the Heisenberg model.

Abstract: Nanoparticles of Nd(Fe_1-xCo_x)B with Co concentrations ranging from x = 0 to 0.5 were prepared using a modified Pechini-type sol-gel method. We have shown the influence of Co on the morphology and size of nanoparticles, as well as on elements distribution in nanostructures. It was found that nanoparticles with increased content of Fe and Co were formed during the synthesis process. There was an interdiffusion of Nd and Fe, both after oxidation and after reduction. This study helped to define promising “bottom-up” approaches for the fabrication of nanomaterials for the advanced Nd(_Fe1-xCo_x)B permanent magnets by chemical synthesis.

Abstract: Spark erosion of WC-8Co carbide pieces in oil resulted in a powder consisting of nanostructured spherical microparticles formed by rapid crystallization of the melt. These particles consist of rounded WC grains with an average diameter of about 0.18 μm, surrounded by cobalt. The process productivity, specific energy consumption, microstructure, particle size distribution, chemical and phase compositions of the obtained powder are determined. It was found that as a result of oil pyrolysis, free carbon is formed (3.4 %), which makes this powder unsuitable for the production of carbide products from it. A technique has been developed and the process of controlled removal of excess carbon by annealing the obtained powder in a CO₂ atmosphere at a temperature of 1000 °C has been studied. As a result of annealing for 120 minutes, the carbon content decreases to the required value (5.6 %). Studies of the phase composition and microstructure showed that the obtained particles consist of elongated WC grains, the average diameter of which increased to 0.43 μm.

Abstract: Antibacterial composites based on linen and NPs obtained by pulsed laser ablation of a zinc target in air were synthesized at various concentrations of the active component (ZnO NPs). The surface morphology and optical properties of ZnO/linen composites were investigated by scanning electron microscopy and UV-visible spectroscopy. The antibacterial activity of ZnO/linen composites was tested on S.aureus in accordance with ISO 20743:2013. It was found that the antibacterial activity depends on the concentration of ZnO NPs. High antibacterial activity of the composites was achieved when the concentration of the active component was of 0.25 mg/cm2. At a concentration of 0.1 mg/cm2 the composites showed only a bacteriostatic effect. The use of photoactivation of composites by LED radiation of 365 nm for 10 min led to an increase in antibacterial activity about 1.5 times for the samples in both concentrations.

Abstract: The paper presents results of investigation of biocompatible coatings on VT1-0 commercially pure titanium formed using plasma electrolytic oxidation (PEO) method. The effects of samples with different surface treatment on the functional activity of cells innate immunity have been studied. The study of enzymes has showed the higher stimulation of cellular metabolism during the first hour of contact with the PEO-coating in comparison with the uncoated titanium. The smallest immunostimulatory influence has been obtained for PEO-coating. It has been established that PEO-layers on titanium affect the functional state of cellular processes accompanying bone mineralization.

Abstract: New method of synthesis of biocompatible, biodegradable and nontoxic composite materials based on polysaccharide chitosan and inorganic phosphate component will be presented in this work. Materials structure was changed by in situ transformation of phosphate phases. Transformation of initial precursors to hydroxyapatite as one of the most stable phosphate phase occurred as a result of thermal and alkaline treatment. XRD and SEM methods were applied to investigate structure and morphology of obtained samples.

Abstract: Plasma electrolytic oxidation (PEO) was used to form a protective layer on 5754 and 2024 aluminum alloys to improve the corrosion properties of the processed materials. The protective performances of the obtained coatings were studied by a combination of electrochemical methods and salt spray test. The absence of pitting corrosion after a 7-day test for the entire series of PEO-layers on aluminum alloys 5754 and 2024 was confirmed by scanning electron microscopy (SEM). Also, microcracks were detected only in the SEM-image for the most porous and thin PEO-coating formed on aluminum alloy 2024 at duty cycle = 0.06 and 30 min.