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The most promising method of increasing the wear resistance of low-resource parts of machines and mechanisms is the formation of wear-resistant layers on their working surfaces from the most accessible and low-cost materials for coatings in combination with technologies for applying coatings and their subsequent processing. The article proposes a method for creating parts with wear-resistant coatings, combining flame and (or) electric arc spraying of steels of ferritic and martensitic classes and their subsequent electrical contact processing. When creating coatings, it is proposed to use an approach based on the creation and targeted controlled use of deformation-induced structural-phase transformations and metastable states during the application of gas-thermal coatings and their processing, which ensure an increase in microhardness, wear resistance, physical-mechanical and operational properties. A new approach to obtaining gas-thermal steel coatings on low-alloy steels with increased wear resistance is proposed, which is based on the creation and purposeful controlled use of deformation structural-phase γ→α transformations and metastable states by means of temperature-force influence during their electrical contact processing; The relationship between the physico-mechanical properties of steel coatings and structural-phase γ→α transformations in them is established, and it is shown that the level of these properties, controlled by the degree of saturation of the martensitic α-phase with carbon, increases with an increase in the content of carbon and carbide inclusions in steels. [ABSTRACT FROM AUTHOR]

The paper presents the results of the studies into the photoluminescence of cytosine molecules in a neutral liquid medium induced by the radiation of a xenon lamp with a wavelength of 280 nm. It was found that the luminescence is represented by a wide band with a vague threshold at a wavelength of 340 nm and a blurred maximum in the spectral region of 365-380 nm. It is shown that the presented luminescence curve reflects fluorescence, while phosphorescence is absent entirely. The lack of phosphorescence can be explained by the effect of the solvent. The obtained results are compared with the data of known studies. The discrepancies found may be primarily due to the pH of the solvents used in the previous studies. It is the first time that experiments with the excitation of luminescence of a neutral liquid solution of cytosine molecules under the simultaneous action of xenon lamp radiation with a wavelength of 280 nm and a continuous laser beam with a wavelength of 530 nm and a power of 0.25 W have been performed. It has been established that under these experimental conditions the luminescence curve acquires a qualitatively new form - the luminescence threshold is shifted to the short-wavelength region, and the luminescence curve has an additional maximum at a wavelength of 410 nm. An explanation of the physical nature of this phenomenon is given, which is that the intense electromagnetic field generated by the laser promotes the efficient formation of singlet exciters of cytosine (photodimers). In the process of their decay, cytosine photodimers form excited monomers in singlet states which, by intercombinational conversion (intersystem crossing), intensively populate metastable triplet states. The radiation decay of the formed metastable triplet states causes phosphorescence, which is the reason for the appearance of the second maximum in the wavelength range of 410 nm. Attention is drawn to the fact that metastable triplet states play a key role in the photochemistry of nucleic acid bases and presumably will have a major impact on the development of new biotechnologies. [ABSTRACT FROM AUTHOR]

The Cahn-Hilliard model concepts are extended to describe the spinodal decomposition of GaxIn1-xPyAs1-y solid solutions grown on the InP substrate. The energy of elastic deformation of the thin layer of a solid solution was calculated on the assumption of its coherent conjugation with the massive InP substrate. The excess energy of component mixing in the solid phase was modeled in accordance with the simple solution model, when the simultaneous substitution of components in the metal and metalloid sub lattices of the sphalerite structure is incorporated. The system of differential equations describing variations of the composition of a semiconductor solid solution after its spinodal decomposition was solved numerically under various thermodynamic conditions. The temperature-concentration intervals in which the oscillations of the supersaturated metastable state of the solid phase may take place were found by analyzing the phase portrait of the resulting system of differential equations. We obtained the thermodynamic synthesis conditions ensuring the appearance of the microoscillations of the solid solution composition. It was shown that the development of intensive oscillations (composition modulation effect in material) is caused by the mutual transition of all excess thermodynamic energy of mixing of an unstable solid phase into the energy of elastic stresses of the coherently conjugated layers of decaying material (energy resonance). The shape of the component concentration profiles in the obtained oscillatory process differs significantly from the shape corresponding to harmonic oscillations. One reason for this is the complex dependence of the model's parameters of the distribution on the material's composition. Another reason is that the solutions found are in close proximity to the resonance, which is characterized by a significant increase in the oscillation amplitude and, as a consequence, the manifestation of nonlinear properties of the system. The results obtained clearly illustrate the formation of concentration domains during the spinodal decomposition of the multicomponent semiconductor solid phase. The results of the parameter calculation for the oscillatory process were compared with the data on the modulation composition effect, which is experimentally observed during the production of elastically strained GaxIn1-xPyAs1-y heterostructures. The interval of thermodynamic parameters of the growing system which ensures the development of the composition modulation effect in GaxIn1-xPyAs1-y solid solutions was considered in detail. [ABSTRACT FROM AUTHOR]

The Cahn and Hilliard model concept is adapted for describing the spinodal decomposition of GacIn1-cP solid solutions grown on a GaAs substrate. The elastic strain energy of a thin layer of a solid solution is calculated on the assumption that it is coherently conjugated with a massive GaAs substrate. The excess energy of mixing of the components in the solid phase is modeled in the framework of the simple solutions theory. The resulting differential equation describing the variations of the semiconductor solid solution composition under various conditions of its synthesis is solved by numerical and qualitative analysis methods. In particular, the thermodynamic conditions for the appearance of the oscillation regime during the relaxation of the supersaturated metastable state of the solid phase are found by analyzing the phase portrait of the obtained differential equation. It is shown that the appearance of such oscillations, i.e. of the composition modulation effect in the solid solution, is caused by the mutual transition of the excess thermodynamic energy of mixing of the unstable solid phase into the energy of elastic stresses of coherently conjugated layers after decompositions. The concentration profiles of the components in the obtained oscillatory process differ significantly from the harmonic ones. This is explained by the strong correlation between the parameters of the differential equation and the material composition. Moreover, the derived solutions are revealed in a vicinity of the resonance state, which is characterized by a significant increase in the oscillation amplitudes and, as a consequence, the manifestation of system’s nonlinearity. The results obtained concern the formation of concentration domains during the spinodal decomposition of a semiconductor solid phase. The results for the calculations of the oscillating process parameters are compared with the data on the composition modulation effect, which is experimentally observed in the growth of elastically strained GacIn1-cP – GaAs heterostructures. The range of thermodynamic parameters of the growth system where the composition modulation effect in the of GacIn1-cP solid solutions has to be observed is specified on the system’s temperaturecomposition phase diagram. [ABSTRACT FROM AUTHOR]