Size-dependent properties of dithallium selenide

We report on size-dependent properties of dithallium selenide, Tl2Se. We have carried out a comparative nuclear magnetic resonance (NMR) study of Tl2Se nanorods and bulk samples, measuring NMR spectra and spin-lattice relaxation rate of 203Tl and 205Tl isotopes. Though bulk Tl2Se was reported to be a metal, the Korringa-like spin-lattice relaxation behavior is observed only at low temperatures and is transformed to an activation regime above ~200 K. This finding is interpreted assuming a two-band model in the semimetallic compound. Our measurements show significant difference in the Knight shift and indirect nuclear exchange coupling for the bulk and nanorod Tl2Se samples, reflecting noticeable distinction in their electronic structure. At that, Tl2Se nanorods are semiconductors and exhibit a characteristic activation behavior in the spin-lattice relaxation rate due to the thermal excitation of carriers to the conduction band. The obtained size dependence of the Tl2Se properties is interpreted in terms of the semimetal-semiconductor transformation due to the quantum confinement.Comment: 15 pages, 4 figure

Effect of thickness on the piezoelectric properties of LiNbO3 films

The results were obtained using the equipment of Research and Education Center and the Center of collective use “Nanotechnology” of Southern Federal University

The influence of styles of family education on emotional-volitional sphere of the senior preschool children

The article discusses the style of family education as its most important characteristic, the most inherent ways of attitude of parents to a child, using certain means and methods of pedagogical influence, which are expressed in a peculiar manner of verbal circulation and interactio

Electronic properties and phase transitions in low-dimensional semiconductors

We present the first review of the current state of the literature on electronic properties and phase transitions in TlX and TlMX2 (M = Ga, In; X = Se, S, Te) compounds. These chalcogenides belong to a family of the low-dimensional semiconductors possessing chain or layered structure. They are of significant interest because of their highly anisotropic properties, semi- and photoconductivity, non-linear effects in their I-V characteristics (including a region of negative differential resistance), switching and memory effects, second harmonic optical generation, relaxor behavior and potential applications for optoelectronic devices. We review the crystal structure of TlX and TlMX2 compounds, their transport properties under ambient conditions, experimental and theoretical studies of the electronic structure, transport properties and semiconductor-metal phase transitions under high pressure, and sequences of temperature-induced structural phase transitions with intermediate incommensurate states. Electronic nature of the ferroelectric phase transitions in the above-mentioned compounds, as well as relaxor behavior, nanodomains and possible occurrence of quantum dots in doped and irradiated crystals is discussed.Comment: 70 pages, 38 figure

Experimental study on micro-abrasion behavior of hard coatings: The role of load, sliding distance and abrasive particle size

In this study, the micro abrasion wear behavior of the TiN, TiAlN, TiAlN/TiSiN and AlCrN coated WC materials was investigated. The coating process was carried out using the Physical Vapor Deposition (PVD) method. All coatings have a dense and homogeneous microstructure without delamination or crack formation. Wear tests were performed by fixed ball micro abrasion wear device. Micro abrasion wear test were carried out at different loads, abrasive sizes and sliding distances. As a result of the experiments, the best wear performance was obtained with AlCrN coated WC materials at all loads and abrasive grit sizes, followed by TiAlN/TiSiN coated and TiAlN coated samples. Depending on the increase in load, volume losses were increased in all samples under all conditions. Higher wear losses were determined in the tests performed with larger SiC abrasive particles. In the tests performed with SiC F800, the wear mechanism was micro-grooving wear mechanism, while in SiC F1200 tests the wear mechanism was micro-rolling mechanism. The increased number of cycles increased the volume loss of the samples. In the tests conducted with the SiC F800, the micro-grooves were more pronounced in short-range tests, whereas the groove steps in the long-range tests were reduced. © 2019 IOP Publishing Ltd