Plasma Chemistry and Plasma Processing (v.29, #1)

Gas-Phase Chemistry of Pulsed n-Hexane Discharge by Richard Gordon Pierce; Gabriel Padron-Wells; Matthew J. Goeckner (1-11).
Many types of carbon films are being investigated for use in many different applications for their electrical, mechanical, and optical properties. Organic based plasmas are beginning to be used for the production of a wide variety of novel film stacks. The use of these stacks can range from sensor to dielectrics for flexible electronics to biocompatible surfaces. Knowledge of how these films actually grow is largely unknown. In light of this, we have performed Fourier transform infrared (FTIR) spectroscopy to the study of hexane plasmas. We use this diagnostic to identify different plasma-produced daughter species produced from n-hexane. For example, we observe the creation of methane, ethylene, and acetylene. From this we develop a likely dissociation model for the parent gas.
Keywords: Pulsed plasma polymerization; FTIR; n-Hexane; Cold plasma

The decomposition of propane diluted in air has been investigated using a pulsed high-voltage dielectric barrier discharges reactor. Effects of the temperature (from 300 to 800 K) and humidity in air on propane conversion and on produced species are studied. CO and CO2 are the two main carbon species produced but other carbon species can be also obtained as functions of electrical parameters or temperature. Total decomposition of inlet propane to CO2 is possible when propane is diluted in wet air from 600 K. Thermal energy is an important parameter to limit the energy density injected in the plasma reactor and to reduce the total energetic cost keeping a high propane decomposition yield.
Keywords: Non-thermal plasma; DBD; Volatile organic compounds; Propane; Heating

Plasma-catalytic Reactor for Decomposition of Chlorinated Hydrocarbons by K. Krawczyk; B. Ulejczyk; H. K. Song; A. Lamenta; B. Paluch; K. Schmidt-Szałowski (27-41).
The conversion of trichloromethane in mixtures with air was investigated under normal pressure in a gliding discharge (GD) reactor operated in both a homogeneous gas system and with a solid catalyst. The Pt catalyst supported by a honey-comb cordierite structure was placed in the reactor below the ends of the electrodes. Cl2 and HCl were the main products of the CHCl3 conversion. The presence of CCl4 was also noted. The influence of the electrode length and the distance between the electrodes in the narrowest section on CHCl3 conversion was examined. The Pt catalyst revealed some activity in the trichloromethane processing. This resulted in an increased overall CHCl3 conversion with the portion of CHCl3 converted to CCl4 smaller than that in the homogeneous system. The effect of temperature on CHCl3 conversion was found to be significant.
Keywords: Plasma-catalytic system; Gliding discharges; Pt catalyst; Trichloromethane

Low-temperature NO x Selective Reduction by Hydrocarbons on H-Mordenite Catalysts in Dielectric Barrier Discharge Plasma by Hong-Yu Fan; Chuan Shi; Xiao-Song Li; Xue-Feng Yang; Yong Xu; Ai-Min Zhu (43-53).
Toward achieving selective catalytic reduction of NO x by hydrocarbons at low temperatures (especially lower than 200 °C), C2H2 selective reduction of NO x was explored on H-mordenite (H-MOR) catalysts in dielectric barrier discharge (DBD) plasma. This work reported significant synergistic effects of DBD plasmas and H-MOR catalysts for C2H2 selective reduction of NO x at low temperatures (100–200 °C ) and across a wide range of O2 content (0–15%). At 100 °C, NO x conversions were 3.3, 11.6 and 66.7% for the plasma alone, catalyst alone and in-plasma catalysis (IPC) cases (with a reactant gas mixture of 500 ppm NO, 500 ppm C2H2, 10% O2 in N2, GHSV = 12,000 h−1 and input energy density of 125 J L 1), respectively. At 200 °C, NO x conversions were 3.8, 54.0 and 91.4% for the above three cases, respectively. Also, strong signals of hydrogen cyanide (HCN) byproduct were observed in the catalyst alone system by an on-line mass spectrometer. By contrast, almost no HCN was detected in the IPC system.
Keywords: Plasma; NO x ; SCR; DBD; H-MOR catalysts; Synergistic effect

The fluid–solid coupling model is developed to simulate substrate melting and deformation during molten droplet impact. In this model, the liquid and solid parts of splat and substrate are governed by the SPH formulations of the Navier–Stokes equations and the conservation equations of continuum mechanics, respectively. This is the first time that the fluid–solid coupling by the SPH method is applied to simulation of the interaction between droplet and substrate during thermal spray coating. The simulation results on formation of the crater are presented to study the Ni droplet impacting onto the Sn substrate, and Mo droplet impacting onto the Steel, Al, and Brass substrates, respectively. It is found that the initial temperatures and thermal properties of droplet and substrate have great effects on the substrate melting and the morphologies of the splat and the substrate.
Keywords: Droplet impact; Substrate melting; Solidification; Fluid–solid coupling model; Smoothed particle hydrodynamics

Determination of the Number of OH Radicals in EB-Irradiated Humid Gases Using Oxidation of CO by Teruyuki Hakoda; Akihiko Shimada; Kanae Matsumoto; Koichi Hirota (69-78).
Electron beam (EB) technology has an advantage for treating dilute environmental pollutants in gases due to high-density population of active species such as radicals and atoms. In general, OH radicals play an important role of initiating the decomposition and removal of such pollutants. It is quite important to understand the behavior of OH radical production for the development of efficient decomposition/removal processes and the comparison with other purification methods. The number of OH radicals produced in humid N2 at doses of 2.0–10.0 kGy with dose rates of 0.17–2.55 kGy/s under 1-MeV EB irradiation was indirectly determined using an index of oxidation of CO to CO2, which has been used in atmospheric chemistry. An experiment under conditions where all OH radicals produced react with CO demonstrated that the concentration of CO2 increased linearly with doses of 0–10 kGy, and the G(OH) was estimated as 4.90.
Keywords: Electron beam; Determination; OH radicals; CO; Oxidation; CO2