The subject of study is the mathematical model for thermal processes during the formation of nanostructures in a plasma medium. In previous studies, it was shown that for the appearance of nanostructures, it is necessary that there be a certain temperature, its rate of increase, and thermal stresses. The required depth of the near-surface layer of the processed material, which is most favorable for the formation of nanostructures, is determined where the highest temperature stress gradients occur. The current work determines the technological parameters for obtaining nanostructures during ion-plasma treatment of the copper surface, as an example. The task of this work, by changing the energy of the ions, is to choose the location of the fields along the depth of the material to generate the necessary high temperature gradients in the given planes of the material. Thus, significant thermal stresses, and hence nanostructures, can be created in a large volume of material. The method used is analytical. In our work, a mathematical model was developed to describe the generation of temperature fields during ion-plasma surface treatment and tested on the process of copper treatment with oxygen ions. In this model, the joint actions of plasma flows and flows of charged particles with materials are realized through thermophysical, thermomechanical, thermal fatigue, diffusion, thermochemical, plasma-chemical processes and collisions. Therefore, the developed model will contribute to a more accurate determination of technological parameters for the formation of conditions conducive to the stable growth of nanostructures in the surface layers of processed materials. Because of numerous calculations, the dependence of the temperature of the surface layer of copper on the energy of oxygen ions was determined. The temperature fields in the zone of action of ions for three levels of the plane of the surface layer are calculated depending on the depth of penetration of ions for different times of interaction and at different current densities from 2.7∙106 to 2.1∙108 A/m2. Studies have shown that the maximum surface temperature is reached at the end of the thermal action of the ion. Conclusions. The obtained values of thermal stresses showed the possibility of formation of nanostructures in the surface layer of copper under the action of oxygen ions at a depth of x=0.5λm at a current density of 2.7∙106 A/m2. For the x=0.5λm plane at a current density of 3∙107 A/m2, where the largest temperature gradients were found, the maximum temperature stresses were calculated, amounting to 5∙108 N/m, which confirms the creation of conditions for obtaining nanostructures. But at 2.1∙108 A/m2, the total temperature rises, and the temperature gradients decrease, which decreases temperature stresses and failure to meet the conditions for obtaining nanostructures. The results obtained can be used to develop a technology for the production of nanostructures in a plasma environment, for example, on copper by ion-plasma treatment in an oxygen environment.in a plasma environment, for example, on copper by ion-plasma treatment in an oxygen environment.
The subject of research in this article is the processes of excitation of a vacuum-arc discharge in plasma sources by unconventional methods: the transition of a glow discharge into an arc discharge (TGA) and arc initiation using laser radiation (LR). The goals are to increase the service life of ignition systems (IS) for plasma sources to expand their technological capabilities and the quality of the resulting coatings. The tasks: to investigate the modes in which non-traditional IS stably excite an arc discharge and ensure their high service life. The methods used are analytical and experimental research methods, which were carried out using the developed new devices. The following results have been obtained. The study of arc excitation using a TGA in a system of Penning-type electrodes showed that the use of a plasma source with such an IS is advisable in processes in which reaction gases are used to form compounds with its material on the cathode surface. Otherwise, after several hundred triggering, the probability of PTD decreases to values of 10...50 %, which is explained by the cleaning of the cathode surface from various inhomogeneities. The ignition of the TGA arc using dielectric stimulators of the cathode spot (CS) expands the technological capabilities of the plasma source. Here, the arc discharge stably ignites in the pressure range from 10-2 to 10 Pa, with voltage pulses of the order of 2 kV in a magnetic field with a strength of 5.6 104 A/m and a starting pulse energy of 2 J. The design of a plasma source with a combined IS has been developed, which makes it possible to achieve the maximum reliability of the excitation of a vacuum arc. A plasma source with a combined IS has a reliability of starting the device in the pressure range of 10-2 ... 5 Pa, the presence of a magnetic field of 104 ... 105 A/m and amplitude of starting pulses of 1.5...2.0 kV close to 100%. The conditions under which the formation of vapor condensate of the plasma source cathode material on the surface of the LR input window does not occur are considered, and it is proposed to solve this problem by supplying energy to the condensation zone directly to the formed condensate layer. Conclusions. The use of non-traditional methods of excitation of a vacuum-arc discharge was substantiated and studied: using TGA and LR, a combined IS was developed, in which traditional and non-traditional methods of arc ignition are combined using the advantages of each method, parameters were found under which the IS work under study reliably and have high resource.
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