Plasma reactions of methane in nitrogen and nitrogen/oxygen carriers by matrix isolation FTIR spectroscopy

The plasma-induced reactions of traces of methane in nitrogen and nitrogen/oxygen carriers have been investigated by freezing the products onto a 10 K CsI substrate and performing FTIR analysis on the product mixture. Isotopic substitution studies have been used to assist in identification of reaction intermediates and final products. A combination of low (10 mTorr) and high (2 Torr) pressure discharges has also been used to help in the identification of these products. Oxygen concentration was increased in a stepwise fashion to determine its effect on the reaction product distribution. In the present work, methyl radical was the principal product in low-pressure N₂/CH₄ plasmas, and small amounts of HCN and NH₃ were also produced. In the higher-pressure plasmas, HCN and NH₃ were the principal products. As O₂ was added to the plasmas, CO, H₂O, CO₂, N₂O, NO, O₃, HONO, and HNO₃ were produced in approximately the order shown, i.e., CO was formed in good yield at low oxygen partial pressures, but HNO₃ was produced only in slight yield even at the highest oxygen pressures used in this work. These results are discussed in terms of the development of a plasma device having potential application for destruction of environmentally hazardous materials and how trace organic pollutants might react in such a system.     

纳米碱土金属钛酸盐对MnO_2电极电化学行为的影响

采用溶胶-凝胶法制得钙钛矿型MTiO_3(M=Mg,Ca,Sr,Ba)纳米粉体，并将所得纳 米MTiO_3用于40%KOH电解液中MnO_2电极的物理改性。恒流放电测试结果表明，掺 杂5%的纳米MTiO_3能部分抑制MnO_2电极第二步放电过程中电化学惰性物质 Mn_3O_4的生成，可使MnO_2电极放电提高40%以上；改性电极的可充性能也得到一 定的改善。循环伏安测试表明，在充放电过程中，纳米MTiO_3只是填充到MnO_2空 隙中，并未参与电极反应；纳米MTiO_3的掺入改善了电极的传质和传荷环境，增大 了改性电极的氧化还原电流，提高了电活性物质的利用率；但经多次循环充放，纳 米MTiO_3不能有效地阻止MnO_2的结构崩溃，只能有限地延缓其容量的衰减速度。     

介质阻挡放电脱除甲醛的化学动力学模拟

对大气压介质阻挡放电脱除甲醛进行了化学动力学模拟, 建立了时空平均化的模型, 并对相关的结果进行了实验验证. 分析了各主要物种的浓度随放电时间的变化, 在模拟空气气氛下, HCHO主要由O·和OH·自由基脱除, 其中, OH·自由基的作用更为突出. 强调了氮分子的第一电子激发态N2(A3∑+u)的作用, 它与O2、H2O 分子的碰撞增加了O·和OH·自由基的浓度,在氮气气氛中, N2(A3∑+u)态是使HCHO脱除的主要物种.讨论了HCHO初始浓度、气体流量对HCHO 脱除比能耗和产物中CO2/CO 摩尔比值的影响, HCHO 初始浓度较高时, 甲醛脱除的比能耗较低, 在输入能量密度<60 J·L-1, HCHO 初始浓度较低时, 产物中nCO2 /nCO值较高.     

Chlorinated Organic Compound Removal by Gas Phase Pulsed Streamer Corona Electrical Discharge with Reticulated Vitreous Carbon Electrodes

Trichloroethylene (TCE) and vinyl chloride (VC) removal by gas phase pulsed corona discharge was investigated with attention to energy efficiency and byproduct identification. Approximately 50–95% removal of TCE and vinyl chloride was observed, depending on the energy density applied to the gas. Water vapor reduced TCE removal in some experiments. Evidence was found for post-corona reactions leading to removal of vinyl chloride downstream of the plasma discharge, while significant post-corona removal of TCE was not observed. Removal efficiencies of 100–900 g/kW-hr in the case of 1000 ppm feed of TCE, and of 2–24 g/kW-hr for a 100 ppm feed of vinyl chloride were found. In the TCE experiments, the formation of dichloroacetyl chloride was observed, while an unknown byproduct was found with vinyl chloride. The addition of a platinum-rhodium coated electrode was found to reduce the post-corona removal of vinyl chloride at low energy density.     

On the Use of Global Kinetics Models for the Investigation of Energy Deposition and Chemistry in RF Argon–Oxygen Plasmas Working in the Torr Regime

A global plasma model is used to investigate the chemistry and energy deposition in 13.56 MHz radio-frequency capacitively coupled oxygen–argon discharges under conditions usually used for the deposition of tin oxide films. These models are based on the solution of a stationary electron Boltzmann equation coupled to species balance equations including the vibrational kinetics equations of O₂. The results obtained showed that vibrational non equilibrium of O₂-molecule is not significant. The dissociation degree of O₂ was found to be around a few percents and the discharge was often moderately electronegative even for small O₂ contents in the feed gas. The ionization and energy dissipation mechanisms are mainly governed by the collisional processes involving O₂ for an oxygen feed gas composition greater than 20%. Results also showed that the predicted densities of the charged species and the electronegative character of the discharge are strongly linked to the assumption made on the homogeneity of the power deposition. On the contrary, the predicted density of O-atom is not sensitive to this assumption.     

Electrolytic Nickel Oxides in the Electrodes of Lithium Secondary Batteries

A nickel oxide is synthesized for lithium secondary batteries using the suggested technology of electrolysis of aqueous solutions containing Ni²⁺. These oxides are studied by methods of x-ray structure analysis, thermal analysis, and atomic force microscopy in parallel with the determination of electrochemical characteristics. Electrolytic NiO has better specific discharge characteristics and cycle life as compared with other electrolytic nickel oxide compounds. It may be used as cathodic and anodic material in thin-layer lithium batteries.     

Hydrogen Isotope Exchange Reactions in an Atmospheric Pressure Discharge Utilizing Water as Carrier Gas

Allowing water/hydrogen or water/hydrogen/He gas mixture to flow through micro- hollow type of electrodes and applying 60 Hz AC power between the electrodes made it possible to sustain large area and atmospheric pressure discharge. The electrode assembly was constructed by sandwiching a dielectric spacer with two thin metal sheets and boring an array of micro holes through them. Another variation of the assembly was prepared by stacking thin metallic sheets so that the stack functions as an electrode through which the gas mixture flows for generating dielectric barrier discharge. A large volume of the gas mixture, while producing plasma, underwent instantaneous hydrogen isotope exchange reactions between H₂O and D₂O or between D₂O and H₂ gas molecules. The efficiency of the atmospheric pressure discharge was assessed by measuring the extent of the exchange reactions at a given flow rate of the gas mixture.     

Spark discharge assisted laser induced breakdown spectroscopy

Laser induced breakdown spectroscopy is combined with a spark discharge to operate in a laser triggered spark discharge mode. This spark discharge laser induced breakdown spectroscopy (SD-LIBS) is evaluated for Al and Cu targets in air under atmospheric pressure. Significant enhancement in the measured line intensities and the signal-to-background ratios, which depend on the spark discharge voltage and the laser fluence, is observed in spark discharge laser induced breakdown spectroscopy when compared to laser induced breakdown spectroscopy alone for similar laser conditions. The measured line intensities increase with the applied voltage for both targets, and the ratio of the measured line intensity using spark discharge laser induced breakdown spectroscopy to that using laser induced breakdown spectroscopy is found to increase as the laser fluence is decreased. For Al II 358.56, such intensity enhancement ratio increases from 50 to 400 as the laser fluence is decreased from 48 to 4 J/cm² at an applied voltage of 3.5 kV. Thus, spark discharge laser induced breakdown spectroscopy allows for using laser pulses with relatively low energy to ablate the studied material, causing less ablation, and hence less damage to its surface. Moreover, applying spark discharge laser induced breakdown spectroscopy gives up to 6-fold enhancement in the S / B ratio, compared to those obtained with laser induced breakdown spectroscopy for the investigated spectral emission lines.     

微波等离子体增强辉光放电光源激发温度的研究

研究了一种改进型的微波等离子体增强辉光放电光源在光谱分析中的应用，对其重要的参数指标－激发温度进行了较为较细的考察。结果表明引入微波等离子体后辉光放电的激发温度明显高于单纯辉光放电时的激发温度。     

Direct Non-oxidative Methane Conversion by Non-thermal Plasma: Experimental Study

The direct non-oxidative conversion of methane to higher hydrocarbons in non-thermal plasma, namely dielectric barrier discharge and corona discharge, has been investigated experimentally at atmospheric pressure. In dielectric barrier discharge, the methane is mainly converted to ethane and propane with small amounts of unsaturated and higher hydrocarbons. While in corona discharge, methane was activated mainly to acetylene with small amount of other higher hydrocarbons. Decreasing the gas flow or increasing power input will improve the methane conversion and product yields. It is found that the methane conversion and main product yield against the input specific energy were special functions in both dielectric barrier discharge and corona discharge, independent of the reactor size, and whether fixing flow rate or power input and changing the power input or flow rate. The corona discharge is a promising alternative method for methane conversion to produce acetylene and hydrogen at low temperature.