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71.
The spatial relaxation of electrons to homogeneous states under the action of space-independent electric fields is investigated
in helium, krypton, and N2 plasmas for various electric field strengths. These investigations are based on a new method recently developed for solving
the one-dimensional inhomogeneous electron Boltzmann equation in weakly ionized, collision-dominated plasmas. Elastic as well
as conservative inelastic collisions of electrons with gas atoms have been included in the kinetic treatment. The spatial
relaxation is caused by an imposed direct disturbance in the velocity distribution of the electrons on a spatial boundary.
A pronounced dependence of the relaxation structure and the resultant relaxation length on the atomic data of the electron
collision processes in different gases has been found. Furthermore the relaxation process sensitively depends on the electric
field strength in the region of medium field values. 相似文献
72.
Schmidt-Szalowski K. Rżanek-Boroch Z. Sentek J. Rymuza Z. Kusznierewicz Z. Misiak M. 《Plasmas and Polymers》2000,5(3-4):173-190
Hexamethyldisiloxane (HMDSO) and hexamethyldisilazane (HMDSN) were used as organosilicon reagents for PE-CVD of thin films under filamentary barrier-discharge conditions at atmospheric pressure. Efficient discharges were obtained in the region of moderate frequencies (5 kHz). The following mixtures of organosilicon reagents with carrier gas and oxidants or ammonia were investigated: HMDSO+Ar, HMDSO+N2, HMDSO+O2+Ar, HMDSO+N2O+Ar, and HMDSN+NH3+N2. Under such conditions HMDSO was converted to produce thin films (10–1000 nm) of silicon oxide, generally containing admixtures of residual organic content (Si—CHn and Si—H groups). The films deposited from HMDSN+NH3+N2 contained silicon, nitrogen and oxygen. 相似文献
73.
大气压旋转螺旋状电极辉光放电等离子体催化甲烷偶联 总被引:2,自引:0,他引:2
采用新研制的具有旋转螺旋状电极的大气压辉光放电等离子体反应器催化甲烷偶联制碳二烃. 实验采用铜电极和不锈钢电极分别考察了输入电场峰值电压和甲烷、氢气进料流量等参数对甲烷转化率和碳二烃收率、选择性的影响. 在长时间连续反应无明显积碳的情况下, 最佳试验结果是电极材料为金属铜, 进料流量为60 mL•min-1, V(CH4 )/V(H2)=1的条件下, 输入电场峰值电压为2.3 kV时, 甲烷转化率为70.64%, 碳二烃单程收率及其选择性分别为69.85%和 99.14%. 相似文献
74.
John E. Nicholas Andrew I. Spiers Nicholas A. Martin 《Plasma Chemistry and Plasma Processing》1986,6(1):39-51
Studies of time-resolved absorption spectra of transient species in the decomposition of NH3 by an r.f. pulse discharge together with product analysis showed that the major radical formed was NH at concentrations of the order of 10–6 mol dm–3 (105 molec. cm–3). Possible mechanisms for the formation of the radical during the discharge and its decay following pulse cut-off were tested by computer simulation of the kinetic data. Following zero-order formation with rate coefficient 0.19±0.03 mol dm–3 s–1, the decay was second order in NH with rate coefficient 2.1±0.5×109 mol–1 dm3 s–1 both for pure NH3 and where NH3/rare gas mixtures were investigated. The kinetic data are consistent with NH removal in a nonassociative radical-radical reaction proceeding via a short-lived collision complex, probably 2NH N2H2 N2 + H2. 相似文献
75.
Partha Sarathi Das Basudam Adhikari Sukumar Maiti 《Journal of polymer science. Part A, Polymer chemistry》1994,32(1):39-45
Fluorination of low-density polyethylene, polyacetylene, and poly(vinyl alcohol) was carried out using SF6 gas under electric discharge. The polymers were partially fluorinated and the extent of fluorination was more in the case of poly (vinyl alcohol) than the other two polymers. The fluorinated polymers were characterized by elemental analysis (Fluorine), IR, and x-ray diffraction. Optical transparency of the films was also measured. The fluorinated polymers show better solvent resistance and decreased transparency than the virgin polymer. © 1994 John Wiley & Sons, Inc. 相似文献
76.
Oxidation of Styrene in a Silent Discharge Plasma 总被引:2,自引:0,他引:2
Anderson Graydon K. Snyder Hans Coogan John 《Plasma Chemistry and Plasma Processing》1999,19(1):131-151
A silent discharge plasma reactor has been developed to study the oxidation of styrene vapor in argon/oxygen mixtures. A number of analytical techniques were employed to determine the destruction efficiency and to characterize the intermediate products. The destruction efficiency was measured as a function of initial styrene concentration, temperature, and energy density of the plasma. The formation of solid products was observed in most experiments. At low temperature (100°C), the solid deposit was polymeric in nature, while at high temperature (300°C) the solid appeared to be amorphous carbon. A combination of high temperature and high energy density resulted in high destruction efficiency and minimal production of solid films. The destruction efficiency vs. energy density is shown to be more complex than a simple model predicting exponential behavior. Several reasons for the discrepancy are suggested. The e-folding energy density for the destruction of styrene is compared to literature values for other organic compounds, measured using similar types of plasma reactors. 相似文献
77.
78.
A numerical model of the negative DC corona plasma along a thin wire in dry air is presented. The electron number density and electric field are determined from solution of the one-dimensional coupled continuity equations of charge carriers and Maxwell's equation. The electron kinetic energy distribution is determined from the spatially homogeneous Boltzmann equation. A parametric study is conducted to examine the effects of linear current density (0.1–100 A per cm of wire length), wire radius (10–1000 m), and air temperature (293–800 K) on the distribution of electrons and the Townsend second ionization coefficient. The results are compared to those previously determined for the positive corona discharge. In the negative corona, energetic electrons are present beyond the ionization boundary and the number of electrons is an order of magnitude greater than in the positive corona. The number of electrons increases with increasing gas temperature. The electron energy distribution does not depend on discharge polarity. 相似文献
79.
The effectiveness of applying a pulsed corona discharge to the destruction of olfactory pollution in air was investigated.
This paper presents a comparative study of the decomposition of three representative sulfide compounds in diluted concentrations:
hydrogen sulfide (H2S), dimethyl sulfide (DMS), and ethanethiol (C2H5SH), which could be completely removed when a sufficient but reasonable energy density was deposited in the gas. DMS showed
the lowest energy cost (around 30 eV/molecules); C2H5SH and H2S had an EC of respectively 45 eV and 115 eV. The efficiency of the non-thermal plasma process increased with decreasing the
initial concentration of sulfide compounds, while the energy yield remained almost unchanged. SO2 was the only identified byproduct of H2S decomposition, but the sulfur balance suggests the formation of undetected SO3. The byproducts analyzed during the degradation of DMS and C2H5SH enabled to propose a reaction mechanism, starting with radical attack and breaking of C–S bonds. 相似文献
80.
S. P. Bugaev A. V. Kozyrev V. A. Kuvshinov N. S. Sochugov P. A. Khryapov 《Plasma Chemistry and Plasma Processing》1998,18(2):247-261
Oxidative conversion of a mixture of natural gas and oxygen in a barrier-discharge plasma-chemical reaction was investigated experimentally. The process was conducted at atmospheric pressure and room temperature. The discharge was initiated by high-voltage pulses of 50–100 s duration at a repetition frequency of up to 2 kHz. The principal feature of the process was that in the plasma-chemical reactor conditions were created which stimulated the condensation of the products of incomplete oxidation of methane that resulted in the formation of aerosol even from nonsaturated vapor. The removal of intermediate reagents from the gaseous phases into the aerosol prevented them from further oxidation. Depending on the experimental conditions, the mass percentage of the components of the condensate formed varied within the following limits: formic acid from 20 to 40%, methanol from 8 to 15%, methylformate from 4 to 8%, and water from 40 to 60%. The conversion process has been realized on a laboratory setup of average power up to 1 kW. In the single-pass mode, a 57% degree of conversion of the mixture has been achieved. The energy value of the condensate is 15–20 kWh/kg. 相似文献