Crystal structure formation of BaAl_2Si_2O_8 known as polymorphic compound is investigated in present work depending on conditions of preparation. Characteristics of ceramics have been studied for different modifications of crystal structure. Additional technologic operations (grinding with following heat treatment) have been found to result in polymorphic transformation. Dielectric properties of BaAl_2Si_2O_8 ceramics have been studied for hexagonal, monoclinic crystal structure modifications as well as for that based on phase mixture. It has been shown that the sintering of ceramic material based on the monoclinic crystal structure modification of BaAl_2Si_2O_8 takes place in temperature diapason of 1300-1350°C. Sintering of material with the hexagonal crystal structure modification occurs in temperature diapason of 1450-1500°C. Ceramics materials based on compound BaAl_2Si_2O_8 are found to have low porosity, high Q-factor and dielectric characteristics, allowing use of these ceramic materials for production of resonators and other microwave equipments.
Current paper presents the results of investigating of nanostructured cathode arc vacuum evaporation coatings, based on (Ti, Hf, Nb, Si)N. Several methods of the structural and elemental analysis were used: proton microbeam, nano- and micro-electron beam, X-ray diffraction analysis. To determine tribological properties (scratch resistance, adhesive and cohesive strength) of the coatings, scratch testing were conducting. Influence of thermal annealing at temperatures 300, 500, 800, 1000C on elemental composition, microstructure, residual stress, phase composition, profiles of atomic distribution in the coatings were investigated.
Using X-ray microanalysis and scanning electron microscopy Zn-Ni-SiO_2 plating containing SiO_2 nanoparticles were studied. It was found that X-ray irradiation of the electrolyte leads to the increased Ni concentration in Zn-Ni-SiO_2(X) films and the grain size is also increasing (the grain size is twice that in the unirradiated case). A thickness of Zn-Ni-SiO_2(X) plating is 20 μm and a thickness of the Zn-Ni-SiO_2 plating is about 15 μm. The surface morphology was studied using AFM method. Increasing Ni concentration and Ni_5Zn_{21} phase due to X-Ray irradiation of the electrolyte leading to the improved mechanical properties of the coating.
We have studied the ion-beam synthesis of GaSb nanocrystals in Si by high-fluence "hot" implantation of Sb and Ga ions followed by thermal annealing. The Rutherford backscattering, transmission electron microscopy/transmission electron diffraction, Raman spectroscopy and photoluminescence were used to characterize the implanted layers. It was found that the nanocrystal size increases from 5 to 60 nm in the samples annealed at 900°C up to 20-90 nm in those annealed at 1100°C. For the samples annealed at 900°C a broad band in the region of 0.75-1.05 eV is registered in the photoluminescence spectra. The nature of this photoluminescence band is discussed.
First results in the field of synthesis and research of the multicomponent (Ti-Zr-Hf-V-Nb)N nanostructured coatings are presented in the paper. Influence of processes of spinodal segregation and mass-transfer on single-layered or multilayered crystal boundary (second phase) forming were explored. Superhard nanostructured coatings were investigated before and after annealing at the temperature 600°C using unique methods (slow positron beam, proton microbeam particle induced X-ray emission-μ, Rutherford backscattering-analysis, scanning electron microscopy with energy dispersive X-ray spectroscopy, X-ray diffraction analysis was performed using DRON-4 and nanoindentor). Diffraction spectra were taken point-by-point, with a scanning step 2Θp=0.05 to 0.1°. We detected that positron trapping by defects was observed on the nanograins boundaries and interfaces (vacancies and nanopores which are the part of triple and larger grain's boundary junction). The 3D distribution maps of elements obtained by the proton microbeam (particle induced X-ray emission-μ) together with the results obtained by slow positron microbeam gave us comprehensive information about physical basis of the processes, connected with diffusion and spinodal segregation in superhard coatings.
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