离子色谱法测定煤氮转化为NH3和HCN的行为

NH3和HCN是煤热解过程中释放的主要含氮物，其生成特性与氮氧化物的释放关系密切，因此NH3和HCN的准确测定是该研充方向的关键因素。实验用反应气氛分别为氩、甲烷、15％水蒸气／氩和15％水蒸气／甲烷，经溶液吸收的气相产物用Dionex公司DX-500型离子色谱仪分析测定，考察了热解过程中产生的NOx主要前驱物NH3和HCN的释放规律及其影响因素。在设定的实验条件和测试条件下，得到了较好的实验结果，并推断出一些有意义的结论。     

Determination of dioxins/furans and PCBs by quadrupole ion-trap gas chromatography-mass spectrometry

The versatility and sensitivity of the quadrupole ion trap tandem mass spectrometer has been applied to the determination of polychlorodibenzo-p-dioxins (PCDDs) and polychlorodibenzofurans (PCDFs), and of polychlorinated biphenyls (PCBs). A brief introduction to the theory of ion confinement in a quadrupole ion trap permits discussion of ion trajectory stability, mass-selective ion ejection, the frequencies of ion motion, and the role of resonant excitation of ion motion. The tandem mass spectrometric examination of PCDDs and PCDFs eluting and co-eluting from a gas chromatographic column is described. Illustrative examples are given of the analysis of field samples containing PCDDs and PCDFs. A comparison is presented of the performance of each of a quadrupole ion trap tandem mass spectrometer, a triple stage quadrupole mass spectrometer, and a sector instrument of relatively high mass resolution for the determination of PCDDs and PCDFs. This comparison is made with respect to instrument tuning, calibration plots, detection limits, ion signals at low concentration, relative response factors, ionization cross-sections, and the examination of field samples. The application of quadrupole ion trap tandem mass spectrometry to the examination of PCBs is focused upon those PCB congeners that have the greatest toxicity. 39 congeners of the total of 209 PCB congeners have been identified as having the greatest toxicities. Chemical ionization has been used for the determination of co-eluting congeners #77 and #110 where the toxicity of the former is much greater than that of the latter. An analytical protocol, based on the variation of molecular ion fragmentation according to the degree (or absence) of chlorine ortho-substitution, has been proposed for distinguishing between toxic and nontoxic PCB congeners.     

Development of dielectric barrier discharge plasma processing apparatus for mass spectrometry and thin film deposition

Cost effective and a very simple dielectric barrier discharge plasma processing apparatus for thin film deposition and mass spectroscopic analysis of organic gas mixture has been described. The interesting features of the apparatus are the construction of the dielectric electrodes made of aluminum oxide or alumina (Al(2)O(3)) and glass and the generation of high ignition voltage from the spark plug transformer taken from car. Metal capacitor is introduced in between ground and oscilloscope to measure the executing power during the discharge and the average electron density in the plasma region. The organic polymer films have been deposited on Si (100) substrate using several organic gas compositions. The experimental setup provides a unique drainage system from the reaction chamber controlled by a membrane pump to suck out and remove the poisonous gases or residuals (cyanogens, H-CN, CH(x)NH(2), etc.) which have been produced during the discharge of CH(4)N(2) mixture.     

天然气中稀有气体浓度与同位素比值联测技术及应用

研制了天然气中稀有气体纯化富集的前处理装置,并与稀有气体同位素质谱仪联用,构建了气体样品中He、Ne、Ar、Kr、Xe浓度和同位素比值联测的分析系统,通过1次进样可得到5种稀有气体组分浓度和同位素比值的共计23个数据。稀有气体纯化效果可达99.9%,质谱分析He、Ne、Ar、Kr浓度的相对标准偏差小于10%,同位素比值分析的标准偏差普遍小于5%。将该方法用于分析塔里木盆地天然气样品,得到了丰富的地质地球化学信息,通过稀有气体分布特征进一步明确了塔河和雅克拉气田区域构造活动的差异,以及二者气源岩特性的不同。     

Note: Experiments in hard x-ray chemistry: in situ production of molecular hydrogen and x-ray induced combustion

We have successfully loaded H(2) into a diamond anvil cell at high pressure using the synchrotron x-ray induced decomposition of NH(3)BH(3). In a second set of studies, radiation-assisted release of O(2) from KCLO(3), H(2) release from NH(3)BH(3), and reaction of these gases in a mixture of the reactants to form liquid water using x-rays at ambient conditions was observed. Similar observations were made using a KCLO(3) and NaBH(4) mixture. Depending on reaction conditions, an explosive or far slower reaction producing water was observed.     

An LIF characterization of supersonic BO (X2Σ+) and CN (X2Σ+) radical sources for crossed beam studies

Various ablation sources generating supersonic boron monoxide (BO; X(2)Σ(+)) radical beams utilizing oxygen (O(2)), carbon dioxide (CO(2)), methanol (CH(3)OH), and water (H(2)O) as seeding gases were characterized in a crossed molecular beams setup by mass resolved time-of-flight spectroscopy and spectroscopically via laser induced fluorescence. Intensities of the sources as well as rovibrational energy distributions were analyzed. The molecular oxygen source was found to produce excessive amount of an unwanted BO(2) byproduct. Internal vibrational energy of boron monoxide generated in the water and methanol sources was too high to be considered for the study of dynamics of ground state radicals. The best combination of intensity, purity, and low internal energy was found in the carbon dioxide source to generate boron monoxide. We successfully tested the boron monoxide (BO; X(2)Σ(+)) radical beam source in crossed beams reactions with acetylene (C(2)H(2)) and ethylene (C(2)H(4)). The source was also compared with supersonic beams of the isoelectronic cyano (CN; X(2)Σ(+)) radical.     

Simple calibrated gas feed system

Constant calibrated gas flow is needed in vacuum processes such as plasma etching and sputtering. It is shown that capillary tubes combined with a simple pressure regulator can give satisfactory results. Typical calibrations for different capillary lengths, diameters, and for different gas types (A, N(2), H(2), He, CH(4), CCl(2)F(2), CHClF(2)) are given. Agreement with viscous flow theory is good, and over a 100:1 range in flowrate the resettability and variability in flowrate varies from +/-2% to +/-20%.     

Structure, Mechanical, and Tribological Properties of MoS2/a-C:H Composite Films

A series of hydrogenated amorphous carbon (a-C:H) films doped with molybdenum disulfide (MoS₂) were deposited by medium frequency unbalanced magnetron sputtering with mixed Ar/CH₄ gases of different volume ratios as the source gases. The effects of Ar/CH₄ ratio on morphology, microstructure, mechanical, and tribological properties of the MoS₂/a-C:H composite films were investigated. Results show that the content of MoS₂ in the as-deposited films decreases with the decreasing Ar/CH₄ ratio, and the highest Ar/CH₄ ratio favors the formation of nanostructured films. Besides, the hardness and internal stress of the composite films first decrease and then increase with decreasing Ar/CH₄ ratio. Furthermore, the film deposited at the highest Ar/CH₄ ratio exhibits excellent antiwear ability in all test environments and shows promising potential as a solid lubricating film in aviation and space industries.     

Quantitative analysis of transient surface reactions on planar catalyst with time-resolved time-of-flight mass spectrometry

A procedure for the quantitative analysis of transient surface catalytic reactions in millisecond time resolution has been studied constructing a specially designed apparatus employing (1) pulsed-gas valves for the injection of reactant molecules onto catalysts and (2) a time-of-flight mass spectrometer (TOF-MS) to detect every reaction product simultaneously. For a better understanding of the catalytic activity and selectivity for products quantitatively, a procedure for measuring an amount of reactant molecules injected onto catalyst surface and calibrating the intensity of mass signal were proposed and implemented. We tested the applicability of this procedure for the quantitative analysis of products of NO+H(2) reaction on Pt-Al(2)O(3) catalysts (a planar catalyst: Pt-Al(2)O(3)Si substrates inserted into a micro-tube-reactor with SiC balls). Although the surface area of the planar catalyst was very small, the mass signal intensities of the reaction products were found to be sufficient for the above procedure. We measured the fragmentation patterns and the inherent sensitivity factors in the TOF-MS using the mixture of the internal standard gas Ar and the N-containing gases. The relative sensitivity factors for NH(3), N(2), NO, and N(2)O and the relative intensities of fragment peaks to the molecular ion peak of H(2)O and N(2)O were estimated. The procedure constructed here has enabled us to analyze the transient consecutive secondary catalytic reactions as well as primary reactions based on the formation rate of product molecules per millisecond instead of the mass signal intensities of the reaction products.     

Further laboratory studies and stratospheric flight of a mass spectrometer beam system

A gas expansion system combined with a mass spectrometer has been tested and flown successfully in the stratosphere. Through a sequence of orifices and high speed pumping, gas particles were formed into a molecular beam and analyzed by a sensitive mass spectrometer. During two balloon flights, vertical profiles of all major atmospheric constituents as well as O(3), CO(2), H(2)O and others were obtained. Gases such as (38)Ar and (16)O(17)O provided in-flight calibration standards. The sensitivity of the system was such that gases with mixing ratios of 10 ppb at an ambient pressure of about 10 mbar were detectable.     

Intense beams from gases generated by a permanent magnet ECR ion source at PKU

An electron cyclotron resonance (ECR) ion source is designed for the production of high-current ion beams of various gaseous elements. At the Peking University (PKU), the primary study is focused on developing suitable permanent magnet ECR ion sources (PMECRs) for separated function radio frequency quadrupole (SFRFQ) accelerator and for Peking University Neutron Imaging Facility. Recently, other kinds of high-intensity ion beams are required for new acceleration structure demonstration, simulation of fusion reactor material irradiation, aviation bearing modification, and other applications. So we expanded the ion beam category from O(+), H(+), and D(+) to N(+), Ar(+), and He(+). Up to now, about 120 mA of H(+), 83 mA of D(+), 50 mA of O(+), 63 mA of N(+), 70 mA of Ar(+), and 65 mA of He(+) extracted at 50 kV through a φ 6 mm aperture were produced by the PMECRs at PKU. Their rms emittances are less than 0.2 π?mm?mrad. Tungsten samples were irradiated by H(+) or He(+) beam extracted from this ion source and H∕He holes and bubbles have been observed on the samples. A method to produce a high intensity H∕He mixed beam to study synergistic effect is developed for nuclear material irradiation. To design a He(+) beam injector for coupled radio frequency quadruple and SFRFQ cavity, He(+) beam transmission experiments were carried out on PKU low energy beam transport test bench and the transmission was less than 50%. It indicated that some electrode modifications must be done to decrease the divergence of He(+) beam.     

Chemical ionization tandem mass spectrometer for the in situ measurement of methyl hydrogen peroxide

A new approach for measuring gas-phase methyl hydrogen peroxide [(MHP) CH(3)OOH] utilizing chemical ionization mass spectrometry is presented. Tandem mass spectrometry is used to avoid mass interferences that hindered previous attempts to measure atmospheric CH(3)OOH with CF(3)O(-) clustering chemistry. CH(3)OOH has been successfully measured in situ using this technique during both airborne and ground-based campaigns. The accuracy and precision for the MHP measurement are a function of water vapor mixing ratio. Typical precision at 500 pptv MHP and 100 ppmv H(2)O is ±80 pptv (2 sigma) for a 1 s integration period. The accuracy at 100 ppmv H(2)O is estimated to be better than ±40%. Chemical ionization tandem mass spectrometry shows considerable promise for the determination of in situ atmospheric trace gas mixing ratios where isobaric compounds or mass interferences impede accurate measurements.     

A simple method for the removal of thiols on gold surfaces using an NH4OH-H2O2-H2O solution

The removal behavior of self-assembled monolayers (SAMs) of thiol molecules on a gold substrate by an NH(4)OH-H(2)O(2)-H(2)O solution was studied using attenuated total reflectance infrared spectroscopy (ATR-IR) and atomic force microscopy (AFM). Furthermore, the impact of the concentration of NH(4)OH and H(2)O(2) in the solution and reaction temperature on the SAM removal rate and efficiency was explored. The SAM removal rate and efficiency were significantly influenced by the concentration of NH(4)OH rather than H(2)O(2). The solution containing the 2 : 1 molar ratio of NH(4)OH : H(2)O(2) among three different solutions showed the highest removal rate and efficiency in the removal of 11-mercapto-1-undecanol. The increase in the reaction temperature resulted in the enhancement on the SAM removal rate, but it led to the fast delamination of the gold layer. These results may be useful in the regeneration of sensor surfaces relying on gold/thiol chemistry.     

氩气浓度对热丝法化学气相沉积纳米金刚石膜的影响

采用热丝化学气相沉积方法,以Ar+CH4+H2混合气体作为气源,通过改变氩气浓度,在单晶硅(100)基片上沉积纳米金刚石膜;采用扫描电子显微镜、原子力显微镜、X射线衍射仪和拉曼光谱仪等分析了纳米金刚石膜的形貌、微结构以及残余应力。结果表明:随着氩气浓度的增大,膜的晶粒尺寸逐渐减小到纳米级;由于晶粒细化导致膜内残余应力由拉应力变为压应力,并且压应力随氩气浓度的增大呈现先增大后减小的趋势;当氩气体积分数为98%时,即在贫氢的气氛中成功获得了平均晶粒尺寸为54 nm、均方根粗糙度约为14.7 nm的纳米金刚石膜。     

气相色谱法测定调味水产品中的甜蜜素

研究优化调味水产品中甜蜜素的分析方法,以降低其检出限。在样品前处理过程中加入沉降试剂(沉降试剂Ⅰ:150g/L K4[FeCCN6].3H2O溶液;沉降试剂Ⅱ:300g/L ZnSO4·7H2O溶液),离心后加入无水硫酸钠、亚硝酸钠、正己烷和硫酸,于40℃水浴加热0.5h,经冷水冷却后剧烈震荡,分层后取正己烷层用气相色谱仪测定。实验结果表明,该沉降试剂降解泡沫彻底,分层效果较好。用恒温40℃来酯化,比冰浴效果理想。测定甜蜜素的线性范围为0.5-50μg/mL,线性良好,相关系数0.9992,甜蜜素的最低检出限5mg/kg。基质加标回收实验的平均回收率88.0%-95.0%。该方法简单快捷,且准确度和精密度均符合残留分析要求,尤其适合蛋白质含量较高水产品中甜蜜素的测定。     

CaF2, MgF2, SiO2, Al2O3, SiC, LiF, BaF2, and ZrO2 optical single crystals used in studies in the VUV spectral region

Spectral characteristics of single crystals—fluorite, magnesium fluoride, quartz, sapphire, silicon carbide, lithium fluoride, barium fluoride, and fianite—used as materials for optical windows in studies in the VUV spectral region are presented. Spectral and photometric studies of single crystals in the spectral range 30–700 nm were performed on a BM-70 vacuum spectrophotometer. This instrument is equipped with a vacuum chamber for measuring the light transmission and reflection at radiation angles of incidence between 10° and 70°; this allows both characteristics to be measured sequentially in time without breaking vacuum. Replaceable radiation sources (with and without a window) were used to perform studies in the spectral range 30–700 nm, including measurements in flows of atmospheric and inert gases (Ne, He, Ar, N, and H).     

The effect of vibrational relaxation on the discharge coefficient of critical flow venturis

This paper identifies a new mechanism that can affect the discharge coefficient of critical nozzle flows. Specifically, vibrational relaxation effects are demonstrated to significantly influence the discharge coefficient of selected gases in critical venturi flows. This phenomenon explains why certain gases — like carbon dioxide — exhibit calibration characteristics that differ significantly from other gases (e.g., N₂, O₂, Ar, He, and H₂). A mathematical model is developed which predicts this behavior, and vibrational non-equilibrium effects are further substantiated by two independent experiments.     

Air-borne laser induced fluorescence system for measuring OH and other trace gases in the parts-per-quadrillion to parts-per-trillion range

Described in detail is a laser induced fluorescence system which has been successfully interfaced with two aircraft sampling platforms (i.e., Sabreliner jet and an L-188C Electra). This system, which has been under development for four years, presently consists of the following major components: (1) a Nd-Yag laser driven oscillator-amplifier dye laser; (2) a sampling manifold with associated fluorescence detection optics; (3) an OH calibration chamber; (4) a laser beam steering assembly; and (5) sampling electronics and data processing hardware. During the last three years, this system has been flown some 50 000 air miles making tropospheric OH radical measurements over the latitude range of 70 degrees N to 57 degrees S. OH concentrations measured during these flights have ranged from 30 parts-per-quadrillion (3.7x10(5) molecules/cm(3)) at altitudes of 6 km to 0.8 parts-per-trillion (2.0x10(7) molecules/cm(3)) at 0.5 km. Computations have been completed which indicate that the existing aircraft system with modest modifications should also be capable of detecting natural tropospheric levels of NO, SO(2), CH(2)O, NO(2), HNO(2), NO(3), H(2)O(2), and CS(2) by using both conventional laser-induced fluorescence methodology and multiphoton techniques.     

化学沉淀法制备纳米Al2O3粉体中的反团聚研究

以工业用ＮＨ４Ａｌ（ＳＯ４）２．１２Ｈ２Ｏ和ＮＨ４ＨＣＯ３为原料，采用化学沉淀法制备纳米Ａｌ２Ｏ３粉体。研究了ｐＨ值、乙醇、表面活性剂等因素对Ａｌ２Ｏ３粒子尺寸的影响，并探讨了几种反团聚的机理及效果。     

变压器油中气体拉曼光谱检测及信号处理方法

准确检测变压器油中溶解故障特征气体是诊断变压器运行状态的重要技术手段之一。论文基于拉曼光谱和腔长调制频率锁定原理,搭建了变压器故障特征气体频率锁定腔增强拉曼光检测平台,实现了H_2、CH_4、C_2H_2、C_2H_4、C_2H_6、CO、CO_2等七种故障特征气体的同时检测;1atm时,H_2、CH_4、C_2H_2、C_2H_4、C_2H_6、CO、CO_2的最小检测浓度实验值分别达到106、25、45、73、41、170、126(ppm)。频率锁定增强腔技术使最小检测浓度提高了约68倍。运用小波模极大值法对H_2的拉曼光谱检测信号进行了去噪处理,提出了基于包络线迭代法的光谱基线校正方法,校正后的光谱荧光背景残留减少,使气体拉曼光谱检测准确度提高了约2.95%,为变压器油中溶解故障气体同时准确检测提出了一种新方法。