Plasma-Chemical Conversion of Lower Alkanes with Stimulated Condensation of Incomplete Oxidation Products

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.     

Novel Catalytic Dielectric Barrier Discharge Reactor for Gas-Phase Abatement of Isopropanol

Catalytic gas-phase abatement of air containing 250 ppm of isopropanol (IPA) was carried out with a novel dielectric barrier discharge (DBD) reactor with the inner catalytic electrode made of sintered metal fibers (SMF). The optimization of the reactor performance was carried out by varying the voltage from 12.5 to 22.5 kV and the frequency in the range 200–275 Hz. The performance was significantly improved by modifying SMF with Mn and Co oxide. Under the experimental conditions used, the MnO _x /SMF showed a higher activity towards total oxidation of IPA as compared to CoO _x /SMF and SMF electrodes. The complete destruction of 250 ppm of IPA was attained with a specific input energy of ∼235 J/L using the MnO _x /SMF catalytic electrode, whereas, the total oxidation was achieved at 760 J/L. The better performance of the MnO _x /SMF compared to other catalytic electrodes suggests the formation of short-lived active species on its surface by the in-situ decomposition of ozone.     

Experimental and Theoretical Studies of a Pulsed Microwave Excited Ar/CF4 Plasma

The present work deals with a pulsed microwave discharge in an Ar/CF ₄ gas mixture under a low pressure (1–10 mbar). The discharge chamber developed has a cylindrical geometry with a coupling window alternatively made of quartz or alumina. The setup allows one to investigate the plasma–wall interactions (here etching of the quartz window) and the ignition process of the pulsed microwave plasma. Microwave pulses with a duration of 50–200 s and repetition rate between 1 and 10 kHz are typical for the experiments. The space-time behavior of the fluorine number density in the discharge has been investigated experimentally by optical actinometry. The discharge kinetics is modeled using electron-transport parameters and rate coefficients derived from solutions of the Boltzmann equation. Together with the solution of the continuity and electron balance equations and the rate equations describing the production of CF _x (x=2, 3, 4) radicals and F atoms, a good agreement between experimental and theoretical data can be achieved.     

Erosion of Thin Foils by Sputtering in Hollow Cathodes

A thin copper foil placed diagonally in a cylindrical copper hollow cathode undergoes fast erosion caused by cathode sputtering. Changes in the foil shape are related to current distribution along the hollow cathode axis. The experimental results aid in understanding the increase in spectral lines intensities emitted from conical bottom hollow cathode lamps.     

Ranking Oxidant Sensitiveness: A Guide for Synthetic Utility

Common oxidants used in chemical synthesis, including newly developed perruthenates, were evaluated in the context of understanding (and better appreciating) the sensitiveness and associated potential hazards of these reagents. Analysis using sealed cell differential scanning calorimetry (scDSC) facilitated Yoshida correlations, which were compared to impact sensitiveness and electrostatic discharge experiments (ESD), that enabled sensitiveness ranking. Methyltriphenylphoshonium perruthenate (MTP3, 8 ), isoamyltriphenylphosphonium perruthenate (ATP3, 7 ) and tetraphenylphosphonium perruthenate (TP3, 9 ) were found to be the most sensitive followed by 2-iodoxybenzoic acid (IBX, 2 ) and benzoyl peroxide (BPO, 10 ), whereas the most benign were observed to be Oxone ( 12 ), manganese dioxide (MnO₂, 13 ), and N-bromosuccinimide (NBS, 17 ).     

Effect of corona discharge on cadmium sulphide and lead sulphide films

This paper describes the effect of corona discharge on cadmium sulphide (CdS) and lead sulphide (PbS) films prepared using the chemical route. The property of films before and after exposure to corona has been described in detail. The electronic properties of the CdS and PbS films have been studied by current-voltage (I-V), capacitance-voltage (C-V) measurements. The structural properties and surface morphology were studied by using X-ray diffraction and scanning electron microscopy before and after exposing to Corona discharge. The films displayed the change in surface morphology after exposure to the corona discharge. It has been found that the films showed an increase in resistivity after exposure. This change in property has been attributed to modification in surface states. Time-dependent recovery indicated that room temperature annealing is sufficient to regain the normal resistivity of the films. The experiment was carried with the aim of studying the effect of the interaction of corona discharge on the semiconductor films and its subsequent effects.     

不同碱基物质对燃煤烟气脱氯的影响

实验探究NaOH、Na₂CO₃、NaHCO₃这三种常见的碱基物质在模拟燃煤烟气中的实际表现，发现三种碱基物质均具有一定的脱氯性能，NaOH、Na₂CO₃、NaHCO₃的脱氯性能依次下降，以脱氯效率70%为目标，使用三种碱基物质Na/Cl比分别需要达到5.8、7.1、8.7。高浓度SO₂的存在对烟气脱氯有竞争作用，随着SO₂浓度的提高，脱氯效率线性下降，不同碱基物质下，SO₂浓度对脱氯效率的影响规律基本一致，SO₂浓度每增加100 mg/m³，脱氯效率下降约1.4%。由于三种碱基物质达到相同脱氯效率时的Na/Cl比不同，综合考虑成本和溶解性，NaOH最具工业应用价值。     

The formation of an oscillating system during the sputtering of sapphire single crystal with pulsed glow discharge

Sapphire (α-Al₂O₃, transparent corundum) single crystals were analyzed with pulsed direct current glow discharge mass spectrometry. Combined hollow cathode was used as a discharge cell. To obtain stable sputtering of dielectric material, a formation of initial surface conductivity via preliminary vacuum deposition of thin metallic layer was proposed. Al and Ta film of different thickness (30–200 nm) were considered for this purpose. The approach was found to provide the effective sputtering of dielectrics. The formation of an oscillating system was shown during the sputtering of sapphire samples in a tantalum combined hollow cathode cell. For oriented sapphire single crystals, periodic oscillations of ²⁷Al⁺ intensity were acquired. This phenomenon was observed only for dielectric single crystals and not for other dielectric samples, e.g. alumina ceramic or fused quartz. The linear dependence of oscillation period on the duration of discharge pulse was found. The origin of these oscillations seems to be attributed to periodic fluctuations of surface conductivity. Oscillation periods calculated for two different orientations of sapphire single crystals (001 and 012) were found to be proportional to the main period of sapphire lattice. Therefore, an assumption that the crystal internal structure of the sample might be the cause of the oscillations is discussed.     

以聚乙二醇-b-聚四乙烯基吡啶为模板制备聚联苯胺微/纳米颗粒及其电容特性

以两亲性嵌段共聚物聚乙二醇-b-聚四乙烯基吡啶(PEO-b-P4VP)为模板制备聚联苯胺微/纳米颗粒,调节模板剂胶束溶液pH,得到了一系列形貌和尺寸可控的聚联苯胺微/纳米颗粒。利用红外光谱、核磁共振、透射电镜、循环伏安、恒电流放电、交流阻抗等测试对材料的结构和性能进行了表征。模板法合成的聚联苯胺为平均直径小于200nm的亚微米至纳米级棒状颗粒,其直径随着模板剂胶束溶液pH的降低而增加。所得聚联苯胺颗粒均显示了一定的电化学活性,当电流密度为1A/g时,聚联苯胺的比电容量达到306.3F/g,经过长时间的充放电测试,不同条件下合成的聚联苯胺的容量衰减率均很小,表现出良好的循环稳定性且各样品电化学性能呈现出随着直径的减小而增强的趋势。     

Normal Coordinate Analysis of Pyridine-N-Oxide

We have been interested for some time in the study of the hydrogen bonded complexes in the far-infrared region with special attention to the adducts between phenol and pyridine-N-oxides (1). In such systems the intermolecular mode vσ was identified and some intramolecular vibrations related to the N-O group were observed to be remarkably shifted consequent on hydrogen bonding. In this context we wished to obtain a force field for the complex which could fit the observational results. Unfortunately for one of the constituents i. e. pyridine-N-oxide a force field, suitable for our purposes, was not available and therefore preliminarily we determined it. We report here the results of such analysis.