Effect of ultraviolet irradiation or diffuse discharge plasma on structure and surface electrical charge of micro-arc calcium phosphate coatings

The studies of the effect of ultraviolet (UV) irradiation and plasma of a runaway electron preionized diffuse discharge (REP DD) post-treatments on the surface structure and electrical charge of the micro-arc oxidation (MAO) coatings were performed. The UV irradiation and plasma treatment did not effect on the morphology, roughness and thickness of the MAO coatings. However, these post-treatments led to formation of the small fraction of the crystalline CaHPO4phase in the X-ray amorphous structure of the coatings. Moreover, the UV and REP DD plasma treatments increased the electrostatic potential (EP) negative values from –85 mV to –126 mV of the coatings in the following order: MAO < MAO/UV (for 5 min) < MAO/Plasma (with 10,000 pulses) < MAO/UV (for 20 min) < MAO/Plasma (with 80,000 pulses).

Особенности формирования разряда в ускорителе плазмы и структура струи, истекающей в вакуум

Results of investigation of jet structure created by coaxial plasma accelerator with conical insert in discharge formation region are presented. An irregular structure of the glowing argon and deuterium jet fraction was detected using a fast electron-optical camera. An irregular structure of the glowing argon and deuterium jet fractions was detected using a fast camera. Oscillations of jet radiation intensity with characteristic frequency 0.3-0.9 MHz were detected. The jet of argon plasma consisted of fragments diverging from the axis of motion, the plasma recombined 20 µs after the start of current. The deuterium plasma jet was like flakes. The intensity of its radiation significantly decreased by 8 µs. The characteristic frequencies of irregularities of radiation on jet axis for argon were ~ 0.09 cm-1, for deuterium ~ 0.3 cm-1. Studies of discharge behavior in plasma accelerator demonstrate that diffuse discharge was initiated at the bottom of conical insert. After 0.5 µs discharge exited to the outer edge of insert, counteracted and burned between central and outer electrodes. Discharge exit from accelerator was observed after 3 µs and was accompanied by glowing of end of central electrode. In the course of measuring the temperature of side surface of the external electrode using infrared camera, the localization of heating was detected near the edge of conical insert and at accelerator outlet. The research results can be used for gas ionization, in the irradiation of materials, as well as for laboratory simulation of the interaction of plasma flows with a magnetic field in space.