Stable microwave coaxial cavity plasma system at atmospheric pressure

We present a systematic study of the development of a novel atmospheric microwave plasma system for material processing in the pressure range up to 760 torr and the microwave input power up to 6 kW. Atmospheric microwave plasma was reliably produced and sustained by using a cylindrical resonator with the TM(011) cavity mode. The applicator and the microwave cavity, which is a cylindrical resonator, are carefully designed and optimized with the time dependent finite element Maxwell equation solver. The azimuthal apertures are placed at the maximum magnetic field positions between the cavity and the applicator to maximize the coupling efficiency into the microwave plasma at a resonant frequency of 2.45 GHz. The system consists of a magnetron power supply, a circulator, a directional coupler, a three-stub tuner, a dummy load, a coaxial cavity, and a central cavity. Design and construction of the resonant structures and diagnostics of atmospheric plasma using optical experiments are discussed in various ranges of pressure and microwave input power for different types of gases.     

Building an inexpensive microwave source for electrodeless discharge lamps

We demonstrate that a microwave power source to operate electrodeless discharge lamps can be built by modifying an inexpensive microwave oven at about 1/3 the cost of a commercial unit.     

机载微波辐射计大气温湿廓线反演性能分析

基于RTTOV实现了机载平台的大气微波辐射传输快速计算,给出了机载微波遥感的权重函数;结合ECMWF大气温、湿廓线库建立了用于算法开发的训练库和检验库,并基于神经网络反演算法分析了不同通道组合、观测误差、平台飞行高度等因素对机载平台下微波大气温、湿廓线反演性能的影响。结果表明;神经网络反演算法可以简便、高效地利用多波段的观测信息得到大气温、湿廓线,湿度探测通道可有助于大气温度廓线的反演,且50GHz和118.75GHz附近通道对湿度廓线的反演尤其重要,具有良好的互补性;另外,飞机平台高度的降低能够显著改进飞机以下高度一定范围内的大气温度反演结果。     

Automated microwave radiometer for measuring the atmospheric ozone emission line

The work presents the results of upgrading of microwave spectroradiometer for ground-based remote sensing of Earth’s ozone layer improving essentially the noise temperature (up to value less 1500 K). For this, the low-noise high frequency amplifier was set up in front of the receiver and temperature control of the instrument was changed for stable work of the amplifier.     

Cold plasma brush generated at atmospheric pressure

A cold plasma brush is generated at atmospheric pressure with low power consumption in the level of several watts (as low as 4 W) up to tens of watts (up to 45 W). The plasma can be ignited and sustained in both continuous and pulsed modes with different plasma gases such as argon or helium, but argon was selected as a primary gas for use in this work. The brush-shaped plasma is formed and extended outside of the discharge chamber with typical dimension of 10-15 mm in width and less than 1.0 mm in thickness, which are adjustable by changing the discharge chamber design and operating conditions. The brush-shaped plasma provides some unique features and distinct nonequilibrium plasma characteristics. Temperature measurements using a thermocouple thermometer showed that the gas phase temperatures of the plasma brush are close to room temperature (as low as 42 degrees C) when running with a relatively high gas flow rate of about 3500 ml/min. For an argon plasma brush, the operating voltage from less than 500 V to about 2500 V was tested, with an argon gas flow rate varied from less than 1000 to 3500 ml/min. The cold plasma brush can most efficiently use the discharge power as well as the plasma gas for material and surface treatment. The very low power consumption of such an atmospheric argon plasma brush provides many unique advantages in practical applications including battery-powered operation and use in large-scale applications. Several polymer film samples were tested for surface treatment with the newly developed device, and successful changes of the wettability property from hydrophobic to hydrophilic were achieved within a few seconds.     

A microwave two-wave interferometer for plasma diagnostics

The scheme and the main elements of an interferometer simultaneously operating at frequencies of the 8-and 4-mm ranges are presented. To combin e two radiations in a common waveguide section and separate them by sending to the corresponding receivers, a special separation filter has been developed. A homo-dyne technique for transferring phase measurements to an intermediate frequency is employed in the interferometer. The range of unambiguously measured phase shifts is 1.5°—360°, and the phase-shift measurement error is within 5%.     

Characterization of atmospheric particles by electron probe X-ray microanalysis

Microchemical glass standards were used to validate a quantitation method based on peak-to-background (P/B) ratios from electron probe x-ray microanalysis spectra. This standardless method was applied to the determination of concentrations of individual particles from Malpha or Lalpha lines, as well as from Kalpha lines. The algorithm was tested on particulate glass samples for diameters ranging from 1 to 20 microm. The determined concentrations did not depend on particle size. The certified values for elements were well matched, except for Na, which may migrate under electron bombardment. Finally, classification of qualitative results obtained for aerosol particles was completed by the P/B quantitative method.     

微结构光学零件的大气等离子体数控加工

为了实现对微结构光学零件无表面损伤和亚表面损伤的高效加工,建立了大气等离子体数控加工系统.研究了该系统的平台设计、大气等离子体加工工艺特性及其数控加工过程.首先,根据大气等离子体加工的原理及要求介绍了该数控加工系统的组成.然后,以He/SF6/O2加工熔融石英为例,采用针状电极等离子体矩对系统加工工艺的可控性以及多参数工艺特性进行了探索,并根据工艺实验结果拟合出该加工条件下的去除函数.最后,介绍了整个大气等离子体数控加工的实现过程.实验结果表明:利用该系统可以在平面融石英材料上加工出幅值为150 nm、波长为6 mm的正弦网格结构,由此验证了该数控加工系统的可行性,实现了对复杂面型光学零件表面的确定性加工.     

微波消解微波等离子体炬原子发射光谱法测定芦荟中Fe和Pb的含量

用微波等离子体炬(MPT)为激发光源,氩气为等离子体工作气体,用气动雾化进样,采用标准加入法研究微波等离于体炬原于发射光谱法(MPTAES)测定芦荟中Fe和Pb的方法。详细考察溶液硝酸浓度、微波前向功率、载气流量、工作气流量、氧屏蔽气流量等实验参数对测定的影响,还考察共存离子对测定的影响。同时,还通过常规消解方法与微波消解方法相比较,得出微波消解微波等离子体炬原子发射光谱法具有简单、快速、准确、待测元素不受污染等特点。结果表明,微波消解微波等离子体炬原子发射光谱法可以作为研究芦荟中微量元素的含量的一种行之有效的方法。     

Characterization of magnetic materials using a scanning microwave microprobe

We investigated the electromagnetic properties of metals of iron, nickel, cobalt, aluminum, gold, copper, silver, and permalloy thin films on SiO(2) substrates using a near-field microwave microprobe. The electromagnetic properties of metal sheets were estimated by measuring the microwave reflection coefficient S(11) and compared with the theoretical values. We observed the hysteresis behavior of permalloy thin films on SiO(2) substrates using a near-field scanning microwave microprobes (NSMM) system. Experimental results are in good agreement with the theoretical model of transmission theory. In order to better characterize the electromagnetic properties of metals and magnetic metals instead of the usual method, we take advantage of the noncontact microprobing evaluation capabilities using a near-field microwave.     

A microwave interferometer for steady-state plasma density measurements

An interferometer for a wavelength of 8 mm, capable of homodyne frequency conversion for measuring the electron density of a steady-state plasma from a high-frequency ion source, is described. An original method for generating a reference intermediate-frequency signal using a cavity resonator is applied in the interferometer. The unambiguously measured phase shifts range from 1.5° to 360°, and the error in measuring the phase shift is 5%.__________Translated from Pribory i Tekhnika Eksperimenta, No. 2, 2005, pp. 98–100.Original Russian Text Copyright © 2005 by D. Nagornyi, A. Nagornyi, Voznyi.     

Simple method of determining plasma impedance of streamer discharge in atmospheric air

For atmospheric streamer discharges using a lightning impulse generator, we demonstrate a method of determining the plasma impedance in a streamer region by analyzing the periodic attenuated discharge waveforms having high-frequency components. When the streamer region in the plasma can be treated as an equivalent series circuit model including resistance and inductance elements, the regression waveforms obtained by reducing and smoothing the discharge waveforms are analyzed in the equivalent circuit. We found that the streamer resistance increased exponentially with time after the discharge, whereas the streamer inductance and series impedance were constant at 4.0 Ω for longer than the first period of the discharge waveforms. Moreover, the slope of the regression curve increases more rapidly for the positive streamer resistance than for the negative resistance. Finally, the absolute values of the streamer impedance versus time were 3.3-19 Ω and 3.5-9.0 Ω for positive and negative discharges, respectively.     

Fabrication of diamond nanopowder using microwave plasma torch technique

This article presents a manufacturing process for diamond nanopowder by using a microwave plasma torch technique in a laboratory at near atmospheric pressure. The unique technique utilized in the arrangement is the hybrid plasma torch which was patented in 1997 by Dr. Cheng-Ming Wu in Taiwan. It has the advantage of working at near atmospheric pressure and does not require an extreme vacuum system, which is a necessary condition for fabrication of a large amount of nanoparticles. The applied constituents of gas mixtures for synthesizing diamond nanopowder in the process are CH₄ with AR and CH₄ with N₂, where AR and N₂ serve as catalysts. In processing the reaction chamber, it is first pumped to varied pressures from 40–300 Torr to induce plasma; then, the input reactive gas CH₄ is fixed at a constant flow rate of 0.6 l/min and mixed up with varied input flow rate of the catalysts Ar and N₂ from 0.6–1.2 l/min. The particle size of synthesized diamond nanopowder is within about 25--50 nm diameter, which mainly depends on flow rate of CH₄:AR and CH₄:N₂.     

Analysis on formation mechanism of ultra-smooth surfaces in atmospheric pressure plasma polishing

Atmospheric pressure plasma polishing (APPP) is developed for the final finishing of high quality ultra-smooth surfaces. To improve surface quality, formation mechanism of ultra-smooth surfaces in APPP is studied. Quantum chemistry simulation is used to investigate the interaction between atoms. Simulation of single Si-F bonding process indicates 0.2 eV difference of binding energy between convex and concave models, which reflects the reaction probability of convex structure is higher than that of concave structure. By comparing the spatial atomic configuration and species diffusion path, it is also demonstrated convex topography should be removed faster than concave topography. So roughness of optical surfaces can be reduced further to form ultrasmooth surfaces. And experimental results accord well with theoretical analysis. Detected by atomic force microscopy every 40 s, the average maximum height of surface is testified to decrease faster than the maximum depth obviously, which makes the whole surface going toward a new equilibrium status with lower roughness. Another experiment proves the average surface roughness decreases from Ra 4.529 to 0.926 nm after 100 s continuous machining. And the stereo images also indicate obvious improvement of surface topography. Moreover, free outmost electron is proved to be helpful to promote chemical reaction by simulation, so fresh surfaces may be more favorable for APPP which makes sample preparation more purposeful.     

大气等离子体抛光技术在超光滑硅表面加工中的应用

发展了大气等离子体抛光方法,并用于超光滑表面加工。该技术基于低温等离子体化学反应来实现原子级的材料去除,避免了表层和亚表层损伤。运用原子发射光谱法证明了活性反应原子的有效激发,进而揭示了特定激发态原子对应的电子跃迁轨道。在针对单晶硅片的加工实验中,应用有限元分析法在理论上对加工过程中的空间气体流场分布和样品表面温度分布进行了定性分析。后续的温度检测实验证实了样品表面温度梯度的形成,并表明样品表面最高温度仅为90 ℃。材料去除轮廓检测结果符合空间流场的理论分布模型,加工速率约为32 mm³/min。利用原子力显微镜对表面粗糙度进行测量,证实了加工后样品表面在一定范围内表面粗糙度Ra=0.6 nm。最后,利用X射线光电子谱法研究了该方法对加工后表面材料化学成分的影响。实验和检测结果均表明,该抛光方法可以进行常压条件下的超光滑表面无损抛光加工,实现了高质量光学表面的无损抛光加工。     

Double induction method for electrodeless determination of Hall mobility

An electrodeless (double induction) technique has been developed for the determination of Hall mobility. Measurements were performed on seven solid or liquid metallic samples and the results compared to reported mobilities. With a current of 1 A and magnetic field of 100 G, signals of 100 nV were measured for Cu, Ag, or Au samples, while signals as low as 50 pV can be measured. Hall angles as small as 2 x 10(-6) rad have been determined. The usefulness of this technique in Hall mobility measurements on systems in which electrode dependent results occur or in corrosive materials on which no electrode is stable is emphasized.     

Plasma transferred arc surface modification of atmospheric plasma sprayed ceramic coatings

In this study, a 90MnCrV8 steel surface was coated with aluminum oxide and chromium oxide powders through the Atmospheric plasma spray (APS) and Plasma transferred arc (PTA) methods. The effects of PTA surface melting on the microstructure, hardness, and wear behavior were investigated. The microstructures of plasma-sprayed and modified layers were characterized by Optical microscopy (OM), Scanning electron microscopy (SEM) and Energy dispersive X-ray spectroscopy (EDS). The dry-sliding wear properties of the samples were determined through the ball-on-disk wear test method. Voids, cracks, and nonhomogeneous regions were observed in the microstructure of the APS ceramic-coated surface. These microstructure defects were eliminated by the PTA welding process. The microhardness of the samples was increased. Significant reductions in wear rate were observed after the PTA surface modification. The wear resistance of ceramic coatings increased 7 to 12 times compared to that of the substrate material.

     

Characterization of Alq3 thin films by a near-field microwave microprobe

We observed tris-8-hydroxyquinoline aluminum (Alq3) thin films dependence on substrate heating temperatures by using a near-field microwave microprobe (NFMM) and by optical absorption at wavelengths between 200 and 900nm. The changes of absorption intensity at different substrate heating temperatures are correlated to the changes in the sheet resistance of Alq3 thin films.     

微波消解电感耦合等离子体质谱测定糖果中钛含量

建立了电感耦合等离子质谱（ICP-MS）测定糖果中钛含量的方法,从而推断出食品生产中添加二氧化钛量及食品中的钛残留量是否超标。结果表明,该方法在1．0～100．0g／L范围内呈良好线性关系（r=0．9999）,加标回收率为97．7％～102．2％,测定结果的相对标准偏差为1．04％（n=6）。该方法检出限低,操作简便、快捷、准确,线性范围宽,适用于糖果等食品中钛含量的准确测定。