Thin Films Deposition from Hexamethyldisiloxane and Hexamethyldisilazane under Dielectric-Barrier Discharge (DBD) Conditions

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—CH_n and Si—H groups). The films deposited from HMDSN+NH₃+N₂ contained silicon, nitrogen and oxygen.     

大气压旋转螺旋状电极辉光放电等离子体催化甲烷偶联

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%.     

Determination of several sugars in serum by high-performance anion-exchange chromatography with pulsed amperometric detection

In this paper, a sensitive, simple and direct method for simultaneous determination of glucose, ribose, isomaltose and maltose in serum sample by high-performance anion-exchange chromatography coupled with integrated pulsed amperometric detection was developed. The four target analytes were easily and completely separated on an anion-exchange column at a flow-rate of 0.25 mL/min by binary step gradient elution in about 16 min and the two eluents were deionized water and 500 mM sodium hydroxide, respectively. The separated four analytes were detected directly by using a gold electrode and quadruple-potential waveform integrated pulsed amperometry without derivatization. Under the optimized conditions, when the injection volume was 25 microL, the detection limits (signal-to-noise ratio equal to 3) for glucose, ribose, isomaltose and maltose were 0.92, 7.50, 12.9 and 10.3 ng/mL, respectively. The calibration graphs of peak area for the four analytes were linear over two to three orders of magnitude with correlation coefficients greater than 0.998. R.S.D. of peak areas of the four analytes for five determinations were no more than 5.6%. The analytical method had been applied to the determination of glucose, ribose, isomaltose and maltose in real serum samples and good results with low relative standard deviation not more than 5.3% were obtained. The accuracy of the proposed method was tested by recovery measurements on spiked samples and good recovery results (98.1-107.9%) were obtained.     

Pulsed,Crossed, Supersonic Molecular Beam Studies of Refractory Atom Reactions

Dynamics of refractory atom reactions have been studied with a crossed beam apparatus combining two pulsed, supersonic molecular beam sources, a pulsed UV laser for creating the refractory atoms in the gas phase by laser ablation, and a pulsed dye laser to probe the reaction products by laser-induced fluorescence. Examples of the A1(²P_j) + O₂(X³∑_g)→ A10(X²∑⁺) + O(³P_j), Mg(¹S_o) + N₂O(X¹∑⁺) → MgO(X¹∑⁺,a³Π) + N₂(X¹∑_g⁺) andC(³P_j) + NO(X²Π_r) → CN(X²∑⁺) + 0(³P_j) systems are given. Comparisons with the studies performed using the conventional steady-state beam approach are made.     

Design and Construction of a Pulsed Field-Gradient NMR Probe for a High-Field Superconducting Magnet

We describe the design and construction of a high-resolution pulsed field-gradient NMR probe for use in a high-field superconducting magnet. Overview and details of the design and construction of the probe case, rf circuitry, temperature control and shielded gradient coils for a heteronuclear probe suitable for a spectrometer (Bruker MSL-300) equipped with a wide bore (i.e., 89 mm) magnet (Oxford) are given. The interior of the probe is designed so mat it may be easily moved to variable height so as to accept easily various gradient coils. A design for a novel jig for the winding of saddle-geometry rf coils is given.     

Kinetics and mechanism in the decomposition of NH3 in a radio-frequency pulse discharge

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.     

Fluorination of polymers by sulfur hexafluoride gas under electric discharge

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.     

Oxidation of Styrene in a Silent Discharge Plasma

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.     

基于定向纳米碳管气体放电的气敏传感器研究

介绍了一种基于定向纳米碳管的气敏传感器,以生长定向纳米碳管的氧化铝模板作为阳极,铝板作为阴极,利用纳米碳管的尖端发射效应,在较低的电压下使气体产生放电现象。通过对纳米碳管在气体中击穿电压和放电电流的测量,实现对气体的定性定量检测。同时纳米碳管气敏传感器还具有体积小、灵敏度高、稳定性好、响应速度快、在常温常压下即可进行检测等优点,具有较好的应用前景。