Major scientific results
Mathematical research into the reasons for the formation of the microplasma process has allowed us to determine the theoretical basis of material treatment in the microplasma regime. In the cathode microplasma process discharges are formed under the conditions of depletion of the electrode layer. Decrease in the ion and impurity concentration in the electrode layer in the cathode regime results in cleaning the surface from contamination and the formation of a barrier layer, which is broken down with increasing voltage followed by a microplasma discharge.
On the basis of investigation of the mechanisms of the formation of oxide coatings, we give a mathematical description of the process of producing layered gradient oxide coatings in the microplasma regime, when the limiting stage of the process is the stage of delivering ions, which form a coating from a solution, taking into account the influence of the electric field for coatings with pores of various size. We have also studied the kinetics of the coating formation depending on the concentration of the metal ions, hydroxide ions, the solubility product of the compounds, and pH medium. We have obtained analytical expressions of the distribution of the concentration of the anions and cations involved in the formation of a coating and their flows, taking into account their migration.
For the first time, we have suggested a parametric model of high-current processes in electrolyte solutions whose parameters are specific active resistance of the metal-solution interface and permittivity, as well the method of their determination. The parametric model allows one to calculate the total current and simulate the process of producing a layered gradient coating (reveal the current shape and polarization dependences) at various shapes of the polarizing voltage without manufacturing a power source.
For the first time, we have determined the parameters of microplasma systems (specific active resistance and permittivity, and their variation during the process) on steels, titanium, aluminium in various regimes (pulse potentiostatic, pulse galvanostatic, potentiodynamic) as well as at various pulse durations and component concentrations of the electrolyte solution.
Based on the measurement of the capacitance of the double electric layer, we have investigated the surface state (charge density, surface tension) at the electrode-model solution interface of the oxide coatings developed for implantology.
We have also investigated the adsorption capability of the oxide coatings for implantology on antibiotics and sulpho preparations, which are used in most operations, procaine, B6 and B12 vitamine solutions and casein. It has been shown that coatings of different compositions exhibit different adsorption properties of medical preparations, which allows one to purposefully choose the type of coating. On the basis of research into the morphology of the coatings obtained in various electrolytes, we have revealed the physico-chemical mechanisms linking the electrolyte composition and the coating structure. It has been demonstrated that coatings without pores (with the pore size ranging from 0.1-0.3 μm) are produced from solutions, in which metal ions are in the form of cations. If a coating is produced from a solution with oxygen-containing metal anions, then porous coatings are formed (1-10 μm).
Loading of porous coatings leads to the formation of microcracks located normal to the loading axis, that relax on the pores, which prevents from the development of macrocracks.
We have developed ways of treatment of medical tools in the microplasma regime with the purpose of cleaning and sterilizing. For the first time, experimental installations have been constructed for the treatment of small surgical tools in the microplasma regime.
We have studied the physico-mechanical properties of the produced layered gradient coatings: microhardness, composition, adhesion, porosity, wear resistance, thermal resistance and corrosion resistance in various media.
A new class of functional and decorative coatings has been developed. We have also produced coatings on aluminium, magnesium, titanium and zirconium, which possessing increased wear resistance. The coatings are of a practical deep black colour, they are formed with a sublayer having a high modulus of elasticity.
At present we are developing physico-chemical models revealing the character and behavior of the volt-ampere dependences of the fast high-current processes in electrolyte solutions on various alloys. Unique investigation equipment has been constructed to record the volt-ampere characteristics of microplasma processes and study partial electrochemical and plasma reactions. We have worked out trained mathematical models based on neural networks capable to reveal the alloy type and the technology of its preparation a data-processing and measuring complex.
The data-processing and measuring complex records currents and the specifying voltage in the digital form, calculates the volt-ampere dependences and reveals the active and capacitive current components. Analysis of the active and capacitive components allows one to work on determining partial electrochemical reactions. The applied power source yields a voltage up to 600 V and an average current up to 40 A. Research into the volt-ampere characteristics of the microplasma processes made it possible to elaborate fast analytical techniques to determine aluminium, magnesium and titanium alloys and assess correctness of their technological manufacture.
The unique research equipment has made it possible to study chemical reactions in the water-organic media at the phase interface and synthesize new promising organic and inorganic compounds.
We have shown the possibility of obtaining the fullerenes C60 and C70.
We have also demonstrated the possibility of a sharp increase in the rate of the extraction processes and a new way of controlling the extraction and re-extraction processes.
We have shown the possibility of creating fuel cells by means of a high-energy effect on the phase interface.
Investigation of the volt-ampere characteristics at the phase interface allows suggesting the possibility of synthesizing organic compounds and developing new analytical methods, which make it possible to quickly analyse organic substances in organic solutions.
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