МОДЕЛЮВАННЯ ДУГОВОГО РОЗРЯДУ НА МІДНОМУ КАТОДІ ДЛЯ ГЕНЕРАЦІЇ НАНОСТРУКТУР

The paper considers the model of processes acting in the ionization layer of the cathode assembly during plasma generation of nanostructures. In the given model the processes in electrodynamic and gas - dynamic layers of plasma and their coordination are rather densely considered. Therefore, the solution of the model allows to adequately determine the magnitude of the cathode potential jump in the electrodynamic layer, which allows to compensate for all energy losses during the generation of nanostructures, and the magnitude of ion and electron fluxes at the cathode. The calculations were performed at a constant value of the elongation of the ionization layer, because it has little effect on the change in the ion current density along the length of the cathode layers. Also, the calculations confirmed a non-significant dependence of the initial pressure from the ionization layer on the temperature of the electrons. The obtained dependences, the fraction of ionic current at the cathode and the cathode potential drop from the current density at different cathode temperatures, showed that the change in the proportion of ionic current makes it possible to compensate for energy costs to maintain the cathode temperature. And consideration of the equation of energy balance allowed to establish the range of losses of the working fluid at which it is possible not to take into account the energy of evaporation of the working fluid and steam heating. To determine the current density at the cathode, the dependence of the thermoemission current on the cathode temperature and the dependence of the current density on the cathode on the plasma concentration at different cathode drops and different representations of electric field strengths were obtained. This allowed to determine the cathode temperature due to the ionic current density and to estimate the plasma concentration. Depending on the plasma concentration, the electric transfer coefficient for different emission mechanisms and cathode drops is obtained. All this allowed us to determine the dependence of the specific gravity leaving the cathode per unit time per unit area, on the cathode temperature and heat flux density for the copper cathode. Determining the specific gravity and the transfer coefficient makes it possible to determine the life of the cathode during plasma generation of nanostructures.

MINIATURE ORBITRON VACUUM GAUGE WITH BINARY ANODE

Miniature (volume~ 6 cm3) ionization vacuum gauge of orbitron type is developed. The anode of orbitron is made as two wolfram wires with 70 μm diameter, located parallel to gauge axis and being at the distance of 0,5 mm from the axis, much smaller than ion collector radii (8 mm). Diameter and length of the collector are 16 mm and 32 mm, accordingly, of the cathode – 70 μm and 9 mm. Potentials of anode and collector are zero, anode potential is 300 V, cathode potential is (5 – 15) V, cathode burning voltage is 1,6 V at the current of 0, 76 A, electron emission current – 5 μA. Binary anode is applied for thermal degasation (gas away) of electrodes. The numerical simulation has shown that electron trajectories have spiral-shuttle form (as at one wire anode). Spiral radius is (1 – 6) mm, step – (4 – 8) mm, rotation and shuttle periods – 6 ns and 30 ns, the number of turns and traveling time – 1500 and 7 μs, path length and energy – 1000 cm and (20 – 200) eV. It was experimentally confirmed that manometer sensitivity is about 1000 Torr– 1, that is 1,5 orders of magnitude more than for PMI-2 ion manometer. The orbitron with binary anode is better than PMI-2 manometer because it has considerably less value of electron current (two orders of magnitude), cathode burning power (5 times) and work volume (3 times).

Influence of bath composition on Ti metal deposition in molten CaCl2 containing calcium titanate

The dependence of the cathodic behavior of a Ti ion on the molar ratio of CaO to TiO2 (RCaO/TiO2) was investigated in molten CaCl2 above 1373 K, and the influence of RCaO/TiO2 on Ti metal deposition was discussed. The reduction mechanism changed at RCaO/TiO2 = 1.5; a three-step reduction of Ti was suggested in the melt of RCaO/TiO2 < 1.5, while a two-step reduction seemed to occur above RCaO/TiO2 = 1.5. Titanium metal deposition was also affected by RCaO/TiO2 as well as by the cathode potential, and the suitable RCaO/TiO2 was likely 1.5. Since this value was the same as the suitable value in the molten fluoride system, Ti metal was thought to be obtained only from Ti2O76-. Silicon and Al metal were obtained electrochemically in molten CaCl2 containing calcium silicate and aluminate more easily than Ti metal. The difficulty of the Ti metal deposition is likely to be caused by the so-called shuttle reaction; the shuttle reaction can occur in the Ti metal electrolysis because some ionic states of Ti are stable in the bath. To realize better Ti metal deposition, the control of the shuttle reaction should be important.