Key Engineering Materials Vol. 685

Abstract: Influence of plasma dielectric barrier discharge on oligomerization of carbon monoxide was shown. The ratio of CO and H₂ was equal to 2: 1. Gas flow-rate was 3 cm³/s for H₂ and 6 sm³/s for CO. It was found that methane formation is 1.2% at parameters of dielectric barrier discharge of 0.1 J. per pulse, up to 2000 pulse per second.

Abstract: The influence of the electron beam irradiation on the parameters of aluminum nanopowder oxidation by heating in air was studied. It was found that the oxidation starts at the temperature in the range from 410° C to 460° C and independent on the radiation dose. The degree of oxidation varied from 44.4 % to 58.3 % and its dependence on the radiation dose was not established. The heat energy release occurred in two stages: at the first stage (up to ~ 660° C) in general the increase of the thermal effect was observed. At the second oxidation stage of irradiated aluminum nanopowder the growth of the thermal effect also observed. The peak of heat effect achieved by irradiation (45.0 kGy absorbed dose) was 2576 J/g higher than the thermal effect for non-irradiated aluminum nanopowder. The energy stored is an additional motivating factor in the synthesis of composite materials, intermetallic compounds, hydrogen producing reactions and synthesis of various kinds.

Abstract: Silicon-carbon coatings on silicon substrates were deposited in plasma based nonself-sustained arc discharge with heated cathode by plasma polymerization of silicon organic agent such as polyphenyl methylsiloxane (PPhMS). Silicon-carbon coatings were deposited at PPhMS flow rate of 0.012 ml/min, argon pressure of 0-0.1 Pa, discharge current of 5-8 A, discharge voltage of 130-150 V, and filament current of 68 A. Bipolar pulsed bias voltage was supplied on the substrate during coating deposition. Surface morphology, hardness and elastic modulus of silicon-carbon films were investigated after the deposition. The film surface is very smooth with root-mean-square roughness of 0.579 nm. Maximum hardness of coatings was 11 GPa, and maximum elastic modulus was 142 GPa.

Abstract: Pulsed electric discharge has been used for the removal of iron colloid substances from aqueous solutions. The residual concentration of organic substances in aqueous solution depends on the pulse repetition rate. The maximum decrease in organic substances concentration was observed at the pulse repetition rate of 800 pps. Comparison of the results obtained for iron colloid solutions containing humic substances and solutions of humic subtances with no colloids shows that the highest removal efficiency of organic substances was obtained when no iron and silicon ions were present in the solution. The results of our experiments suggest that pulsed electric discharge treatment for the removal of organic substances from natural waters is more efficient at an after-treatment stage, after precipitation of colloid substances.

Abstract: This paper presents results of study of dissipation processes of pulsed electron beam in the oxygen and hydrogen (300 Torr). These gases are chosen owing of their use as a operating environment at pulse plasmochemical synthesis of nanosized oxides of metals. Experimental studies are conducted on the laboratory TEU-500 electron accelerator (500 keV electron energy; 10 кА ejected electron current; 60 ns half-amplitude pulse duration; 5 pps pulse repetition rate; diameter of a bunch is 5 cm). The electron beam was removed in a drift pipe through the anode window which is the supporting lattice (with optical transparency of 95%) and through aluminum foil 140 microns thick. The pipe of drift is equipped with three shunts of the return current which are fixing a signal at the same time. The received results of researches allow to make a conclusion. It is necessary to increase length to 80 cm and diameter to 30 cm of a pipe of drift for optimum absorption of a pulse electron beam by operating gas, for obtaining high efficiency of electron accelerator of pulse plasmochemical synthesis of nanosized oxides of silicon and the titan.

Abstract: This paper reports about results describing the mechanism of oxidation-reduction reactions occurring in the microwave plasma interaction with organic compounds solutions. Air and argon were used as the plasma gases in the experiments on disrupture of aqueous liquid organic compounds. Application of inversible redox indicator of methylene blue (MB) showed that disrupture of organic substances in microwave plasma was based on redox reactions. It was found that MB highest efficiency in the solution took place when air plasma-supporting gas was used.

Abstract: The paper reports on the interaction of an electric discharge with solutions of organic substances in the electric reactor with iron loading. A colored water solution of organic substances with well-studied properties such as methylene blue (MB), furatsilin and eosin is used. The chosen organic substances allow to demonstrate the redox reactions, destruction of organic substances and their adsorption. It is found out that the process of direct interaction of organic substances with the discharge is 40%. Efficiency of sorption processes on iron load depends on the properties of the dissolved organic substances and for the MB is 21%, for furatsilin is 42% and for eosin is 63%. Post-effects have been observed after the action of the discharges and have shown activity for 24 hours. The obtained results allow modeling the mechanism of transformation of complex organic compounds e.g. humic substances or oil products.

Abstract: Paper presents the results of experiments on multicapillary carbon-epoxy as a candidate material for a cathode of a pulsed electron accelerator. A high voltage pulse of 350 kV, 350 ns (FWHM) was applied to the cathode. The pulse repetition rate was 20 pps. The optical image of the cathode surface after 4×10⁴ shots of electron beam was changed as well as electrical characteristics of the electron diode.

Abstract: Extraction of shale gas and oil has significantly benefited the US economy. However, the applied technology of hydraulic fracturing is inefficient and ecologically unsafe. Electrophysical underground pyrolytic conversion of oil shale kerogen in energy stock can solve these problems. This processing method is feasible due to treeing in rock volume. Treeing has been widely studied in insulation as a negative factor. With regard to oil shale this phenomenon is examined insufficiently despite the fact that in this application area it has its distinctive features and is crucial for the initiation of rock heating and its further conversion. This article describes the shale’s dendrite morphology which is non-typical of conventional treeing in insulation. Features of the discharge structures’ formation are associated with a change of oil shale conductivity by discharge and with a high degree of rock heterogeneity.

Abstract: In this paper the influence of the volume discharge of nanosecond duration formed in a non-uniform electric field at atmospheric pressure on samples of CdHgTe (MCT) epitaxial films of p-type conductivity is investigated. Measurements of electro-physical parameters of MCT samples after irradiation have shown that a layer exhibiting n-type conductivity is formed in the near-surface area of epitaxial films. After more than 600 pulses of influence parameters and thickness of the resulting n-layer is such that the measured field dependence of Hall coefficient corresponds to the material of n-type conductivity. The obtained results show that application of volume nanosecond discharge in air at atmospheric pressure is promising for the modification of the surface properties of epitaxial films of MCT.