Determination of density changes with expansion polymerization

Materials that polymerize without substantial volume contraction have numerous valuable applications in dentistry and other fields. Two new symmetrical aliphatic spiro-orthocar-bonates, formulated from cis- and trans-2-hydroxymethyl-cyclohexanol to give 2,3,8,9-di(tetramethylene)-1,5,7,11-tetraoxaspiro [5,5] undecanes, showed, by density determinations in dilute solution, that expansion occurs with polymerization. The cis / cis-spiroorthocarbonate racemic mixture showed a 3.9% expansion upon polymerization, and the trans/trans racemic mixture showed a 3.5% expansion. The densities were determined by pycnometry, with a precision reliable to at least four figures. This method is thus recommended for cases of soluble monomer/polymer pairs for which the density difference will be small and where the partial specific volumes are independent of concentration, thereby avoiding the complexities of variable physical states of monomer and/or polymer. © 1993 John Wiley & Sons, Inc.     

New design of a radio-frequency plasma torch

A numerical model has been developed for predicting the two-dimensional flow and temperature fields in a radio-frequency (rf) plasma torch. The method employed here is based on Boulos' model with the exception of the boundary conditions for the electric and magnetic field equations. Calculations have been made for the confirmation of a new sample injection method, which is capable of completely evaporating refractory materials at high feeding rates without interfering with the stability of the plasma. In the newly designed torch, the reagent is radially injected into the hottest part of the plasma through quartz capillary tubes set symmetrically between an inductor coil. Experimental investigations have also been performed for verifying the proper function of the design. These results provide evidence that our radial injection method developed here is more effective in practical processing than the conventional axial injection methods.     

High Reactivity of CH2 Radical in an AR–CH4 Post-Discharge

Plasma Chemistry and Plasma Processing - This work is devoted to the study of the reactivity of CH 2 radical in the post-discharge of an Ar–CH 4 microwave plasma. These radicals are...     

Parametric study of the flow and temperature fields in an inductively coupled r.f. plasma torch

A theoretical investigation of the effect of different parameters on the flow and the temperature fields in a radiofrequency inductively coupled plasma is carried out. The parameters studied are: central injection gas flow rate, total gas flow rate, input power, and the type of plasma gas. The results obtained for argon and nitrogen plasmas at atmospheric pressure indicate that the flow and the temperature fields in the coil region, as well as the heat flux to the wall of the plasma confinement tube, are considerably altered by the changes in the torch operating conditions.     

Growth rate studies of CVD diamond in an RF plasma torch

This paper addresses the complex chemistry in the boundary later over a substrate in a chemical vapor deposition rector at atmospheric pressure. In this study, a highspeed plasma (140m/s) was created using a radio-frequency inductively coupled plasma torch for the deposition of diamond thin films. Growth rates on the order of 50 m/ h were obtained for well-faceted continuous films grown on molybdenum substrates positioned normal to the plasma flow. The highest growth rates were obtained at substrate temperatures of 1370 K and a feed gas ratio of 2.5% CH₄ in H₂. Growth rates are compared to predicted results obtained from numerical simulations, based on a one-dimensional stagnation-point flow, and are/mend to be in good agreement. Several other surface analysis techniques were used to characterize the deposited films, inchaling SEA/, Raman spectroscopy, transmission electron microscopy. Rutherfard backscattering spectroscopy, and hydrogen-forward recoil spectroscopy. Optical emission spectroscopy was used to characterize the RF plasma during the deposition process. Results from these studies form an important database for the validation and improvement of current models of the atmospheric-pressure diamond CVD environment.     

反相气相色谱法测定高密度聚乙烯溶解度参数

采用反相气相色谱(IGC)技术测定了高密度聚乙烯(HDPE)在303.15～343.15 K温度范围内的溶解度参数(δ2)及相关指标。以正己烷(n-C6)、正庚烷(n-C7)、正辛烷(n-C8)、正壬烷(n-C9)、三氯甲烷(CHCl3)及乙酸乙酯(EtAc)作为探针分子溶剂,经计算获得了探针溶剂的比保留体积(V0g)、摩尔吸收焓(ΔHS1)、无限稀释摩尔混合焓(ΔH∞l)、摩尔蒸发焓(ΔHv)、无限稀释活度系数(Ω∞1)以及探针溶剂与HDPE的Flory-Huggins相互作用参数(χ∞1,2)等指标。结果表明,上述6种探针溶剂在测定温度范围内均为HDPE的不良溶剂。此外,还推导出了HDPE在室温(298.15 K)下的溶解度参数δ2为19.00 (J/cm3)0.5。     

气相色谱法测定邻苯二甲酸酯

建立了气相色谱分析邻苯二甲酸酯的方法.选择邻苯二甲酸二甲酯(DMP)、邻苯二甲酸二乙酯(DEP)、邻苯二甲酸二异丁酯(DIBP)、邻苯二甲酸二正丁酯(DBP)、邻苯二甲酸丁苄酯(BBP)、邻苯二甲酸二(2-乙基己基)酯(DEHP)、邻苯二甲酸二正辛酯(DOP)7种标物,对实验方法的准确程度进行了分析.7种标物的线性相关系数都能达到0.999以上,线性范围在0.01～1g/L之间;保留时间的相对标准偏差都在0.1%以内,峰面积的相对标准偏差在2%以内.     

Parametric study of an atmospheric pressure microwave-induced plasma of the mini MIP torch — II. Two-dimensional spatially resolved excitation temperature measurements

Two-dimensional mapping of the excitation temperatures have been carried out in the microwave-induced plasma torch with tangential argon flow. It is detected that the presence of wet aerosols in a nebulizer gas increases axial excitation temperature while desolvation acts in the opposite direction. The influence of low hydrogen concentration in the support gas and potassium in the nebulizer gas on the temperature distribution is studied in detail. The comparison of excitation temperature and electron number density distributions clearly indicates non-equilibrium plasma conditions.     

Determination of an amount of gas by weighing under vacuum conditions and uncertainty analysis

For the determination of the calorific value of gases, a mass determination system for the gas burnt in the calorimeter was developed. Contrary to classical methods, which weigh the gas bottle offline, the method applied here weighs the amount of gas online and continuously. For this purpose, a commercial analytical balance with a readability of 10 µg across the entire weighing range of 205 g was modified for use under vacuum conditions.Since the gas bottle has to be permanently connected to the calorimeter by a steel capillary, an additional force is exerted to the balance. The influence of this force is investigated and determined by a special weighing procedure.In addition, an automatic calibration technique must be developed to ensure the traceability of the results to the national standard of mass. This allows an uncertainty analysis according to the Guide to the Expression of Uncertainty in Measurement (GUM) to be performed.This revised version was published online in November 2005 with corrections to the Cover Date.     

基于自制气体循环系统测定全氟异丁腈中杂质成分

建立了基于自制全密闭进样系统的气相色谱-质谱测定全氟异丁腈(C₄F₇N)商品气中杂质的方法。待测气体在自制的密封系统内稀释并混合均匀,使用在线自动六通阀进样,采用Agilent GS-GASPRO色谱柱(30 m×0.32 mm×5μm)分离,测定了国内某公司(DC公司)和国外某公司(AC公司)的全氟异丁腈绝缘气体的杂质成分。结果表明,全氟异丁腈商品气中含有微量的N₂、O₂、C₃HF₇和痕量的C₃F₆,其中AC公司的C₄F₇N商品气体中的杂质总含量为0.13%, C₄F₇N纯度为99.87%; DC公司的C₄F₇N商品气体中的杂质总含量为0.83%, C₄F₇N纯度为99.17%,两家公司的C₄F₇     

Characteristics and electrode erosion rates of a D.C. plasma torch operating with TiCl4 plasma gas

A stable TiCl₄ plasma was produced using a simplified d.c. torch. The arc was struck between two concentric ring electrodes, d mm apart, and rotated using a magnetic coil. The electrode material was a new TaC composite. The arc was operated at 100 A for up to I h using plasma gas containing 0–30% TiCl₄. The voltage was 24–60 V, depending on the TiCl₄ concentration. The electrode erosion rate was of the order of 20g/C. It is shown that the erosion rate is a function of the aerodynamic drag of the are column.     

Parametric study of an atmospheric pressure microwave-induced plasma of the mini MIP torch — I. Two-dimensional spatially resolved electron-number density measurements

The results of spatial distribution measurements of the electron-number density, N_e, in an atmospheric pressure microwave-induced plasma in argon are presented. Electron-number density is determined from the width of the hydrogen H_β 486.13-nm line. The influence of the microwave input power in the range 80–150 W on the spatial distribution of N_e is first determined. For the selected input power of 100 W, the influence of molecular hydrogen in wet and desolvated nebulizer and support gas, and the corresponding changes in the electron density distributions are studied. The influence of potassium as a low ionization-potential element on the spatial distribution of N_e is also studied, with the result that a considerable lowering of the electron number density is detected.     

Air microwave-induced plasma: Detection of NO in the post-discharge using an ArF laser

ArF laser-induced fluorescence (LIF) spectroscopy was applied to the investigation of the density of NO achieved in the post-discharge of an N₂-O₂ microwave-induced plasma (2450 MHz). The fluorescence spectrum provides a determination of NO vibrational temperature downstream the discharge. Absolute concentration profiles were determined in the low-temperature region of the post-discharge.     

Determination of electron density in an atomic plasma by least-squares fit to the Stark profile

The measurement of electron density by a unique, one-parameter least-squares fit to the Stark-broadened hydrogen emission line is presented. The curve-fit approach utilizes approximately 60–80 points, and provides improved precision in the measurement.A comparison of data obtained by measurement of the width at half-height and by least-squares analysis indicates that the half-width method exhibits substantial systematic errors, generally over-estimating electron density by a factor of 2–3.     

Determination of Cyanide Ion by Derivatization-Gas Chromatography

Abstract

A new gas chromatographic method is described for the determination of cyanide ion in water. Cyanide is converted to benzonitrile by reaction with aniline, sodium nitrite, and copper(II) sulfate. The resulting benzonitrile is extracted into chloroform and determined by gas chromatography with a flame ionization detector. The influences of several ions which may coexist with cyanide on this gas chromatographic method were investigated briefly.     

Determination of Vapor Pressures Using Extrapolation of Adjusted Retention Times

Vapor pressure is one of the fundamental properties which govern the distribution of organic compounds in the environment. This property is estimated for five series of homologous substituted alkanes of the type H—(CH₂)_n—Y, where Y denotes Cl, Br, CHO, COOCH₃, OCOCH₃ and n varies from 5 to 14 using extrapolation of adjusted retention times to 25 °C. The results are compared with those obtained by using indirect methods for 40 compounds and a significant improvement is obtained. Indeed, the absolute average error percentage for the same series does not exceed 2.6%     

Problems in the Determination of Polychlorinated Biphenyls

The presence of aromatic hydrocarbons in pesticide-grade hexanes affects the elution patterns of polychlorinated biphenyls (PCB) and chlorinated hydrocarbon pesticides from silicic acid columns. Several batches of silicic acid Silicar® (Mallinckrodt) were contaminated with 0.031–0.163 mcg/g of PCB expressed as Aroclor® 1254. Chlorinated naphthalenes accompany PCB on silicic acid chromatography and their presence can be detected from an absorption maximum at 306 nm, A^1% _1cm = 329. PCB of the Aroclor® 1254 type were detected in American eel (Anguilla rostrata), herring (Clupea harengus), and Atlantic salmon (Salmo salar) in concentrations of 0.63–0.75, 0.32–0.54, and 0.45 mcg/g wet weight, respectively. Commercial fish oil contained 3.55 mcg/g of PCB.     

毛细管气相色谱法测定二乙基二硫的含量

采用毛细管气相色谱法(GC)测定了二乙基二硫的含量.结果表明,二乙基二硫含量在0.01⁰.4g/L范围内具有良好的线性关系,平均回收率为99.91%;该方法简便、准确、重复性好,可方便地用于二乙基二硫含量的测定.     

Hydrogen uptake capacity of C2H4Sc and its ions: A density functional study

We report the gravimetric hydrogen uptake capacity of C₂H₄Sc complex and isoelectronic ions using Density Functional Theory. We predict that C₂H₄Sc⁺ can bind maximum seven hydrogen molecules in dihydrogen form giving gravimetric uptake capacity of 16.2 wt %, larger by about 2 and 4 wt % than the neutral and anion, respectively. We also found that the interaction of hydrogen molecules with C₂H₄Sc⁺ ion is characteristically different than that with neutral and anion. Vibrational spectroscopic study reveals that C₂H₄Sc and isoelectronic ions are quantum mechanically stable with their characteristic change in respective identified mode. The large gravimetric H₂ uptake capacity of C₂H₄Sc⁺ is well above the target specified by Department of Energy (DOE) by 2015. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010