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本文评述了铝、镁、铜、铅、锌、锡等常用有色金属中气体分析发展概况。针对这些金属熔点低、易挥发等特点,介绍了还原提取法、电化学法、活化法和表面分析法等各种气体分析方法的适用性和国内外应用情况。认为采用石墨盒或金属包套的惰气熔化法是目前分析易挥发金属中氢、氧的普遍方法。浓差电池法已广泛地用于测定液态金属中氧。采用活化法测定微量气体及表面气体已越来越多。 相似文献
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采用美国HP6890炼厂气分析多维填充柱色谱仪,建立了汽油中气体组分含量快速分析方法。采用汽油直接进样,校正归一化法定量,测定汽油中CO2、H2S和各气体烃组分的含量,完成一个样品的分析仅需22min。实验表明,该方法有很好的精密度,各气体组分浓度值的相对标准偏差均小于4.5%。 相似文献
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先进气体传感器技术在现代社会安全生产生活中扮演着极为重要的角色, 而高效敏感材料的设计与开发是其中的关键. 中空多壳层结构材料因其独特的层层嵌套的多壳层与多腔体结构而表现出特别的物理化学性质, 在气体传感领域显现出巨大的应用潜力. 传统的硬模板法、 软模板法以及基于奥斯特瓦尔德熟化和柯肯德尔效应的无模板法在中空多壳层纳米结构材料的普适制备及壳层结构的精确调控等方面存在诸多限制. 次序模板法的出现突破了上述限制, 促进了该领域的迅速发展. 本文简要回顾了中空多壳层结构材料制备方法的发展历程, 介绍了其在甲醛、 乙醇、 丙酮、 甲苯及二氧化氮等有害气体检测中的具体应用, 分析了其在气体传感领域的独特优势, 最后对该领域面临的挑战和发展前景进行了总结与展望. 相似文献
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<正>专业容量法高温高压气体吸附仪研发及生产厂家——北京金埃谱科技有限公司,与美国佛吉尼亚理工大学在不久前签订了高温高压气体吸附仪采购合同,并顺利完成仪器的验收及调试。这是国产高温高压气体吸附仪首次成功进入美国市场,打破了国外产品的垄断地位。继金埃谱科技的容量法高温高压气体吸附仪获得国内众多用户(例如中国石油大学、四川大学、北京化工大学、河南理工大学、中国矿业大学、中国 相似文献
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The spectral-polarization characteristics of absorption and phosphorescence of molecules of the initial form of nitro-substituted
indolinospirobenzothiopyran were studied in oriented polyethylene films and in solutions with different polarity. An oscillator
model of the electron transitions responsible for the formation of absorption and luminescence spectra was suggested. It was
established that the principal differences in the spectral and photophysical properties of the compound studied and its oxygen-containing
analog are associated with the fact that the electronegativity of the S atom is lower than that of the O atom.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1143–1146, June, 1997. 相似文献
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Two vanilloids, (5E)-8-(4-hydroxy-3-methoxyphenyl)oct-5-en-4-one (1) and 4-[3-hydroxydecyl]-2-methoxyphenol (2), isolated from the dried seeds of Grains of Paradise (Aframomum melegueta), were synthesized; the latter compound was made as the S-enantiomer and the material derived from the seeds was found to be a 1:1.7 mixture of the R and S isomers. The synthetic route used should allow the preparation of analogs having extended alkyl chains and consequently different lipophilicity, and 3, a homolog of 2, was also prepared. 相似文献
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Cotton cellulose was swollen in a sodium hydroxide solution and carboxymethylated by a two-bath method for different periods of time for each process. The kinetics of acid hydrolysis and the crystallinity of the swollen and carboxymethylated samples were measured. The proportion of broken bonds, rate constants for hydrolysis, and permeability of cellulose to hydrolyzing agents were calculated. The susceptibility of glycosidic linkages to acid hydrolysis was improved by carboxymethylation more than by swelling in alkali. The increased accessibility of carboxymethylcellulose to acid was regarded as a consequence of increased intra-and intercrystalline swelling and of the glycosidic bonds' weakness caused by the electron-attracting carboxymethyl group on the C-6 position. 相似文献
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Stepkowska E. T. Perez-Rodriguez J. L. Jimenez de Haro M. C. Sayagues M. J. 《Journal of Thermal Analysis and Calorimetry》2002,69(1):187-204
Main hydration products of two cement pastes, i.e. CSH-gel, portlandite (P) (and specific surface S) were studied by static heating, and by SEM, TEM and XRD, as a function of cement strength (C-33 and C-43) hydration time (th) and subsequent hydration in water vapour.Total change in mass on hydration and air drying, Mo, increased with strength of cement paste and with hydration time. Content of water escaping at 110 to 220°C, defined as water bound with low energy, mainly interlayer and hydrate water, was independent on cement strength but its content increased with (th). Content of chemically bound (zeolitic) water in CSH-gel, escaping at 220-400°C, was slightly dependent on strength and increased with (th). It was possibly derived from the dehydroxylation of CSH-gel and AFm phase. Portlandite water, escaping at 400-500°C, was independent on cement strength and was higher on longer hydration. Large P crystals were formed in the weaker cement paste C-33. Smaller crystals were formed in C-43 but they increased with (th). Carbonate formated on contact with air (calcite, vaterite and aragonite), decomposed in cement at 600-700oC. It was high in pastes C-33(1 month) and C-43(1 month), i.e. 5.7 and 3.3%, respectively; it was less than 1% after 6 hydration months (low sensitivity to carbonation) in agreement with the XRD study showing carbonates in the air dry paste (1month), and its absence on prolonged hydration (6 months) and on acetone treatment. Water vapour treatment of (6 months) pastes or wetting-drying increased this sensitivity.Nanosized P-crystals, detected by TEM, could contribute to the cement strength; carbonate was observed on the rims of gel clusters.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
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The aim of the presented work was the investigation of thermal oxidation of ilmenite in static air atmosphere. The investigations
were carried out by use of a derivatograph (MOM, Hungary). The changes of crystallographic structure of investigated samples
were identified by X-ray diffractometry on Philips PW-1710 diffractometer. In temperature above 500°C appears structure of
hematite Fe2O3. On the basis of the thermogravimetric measurements, the contracting area and contracting volume models were found as the
best fitting experimental data.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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Cyclopropyl derivative of 2,6-di-tert-butylphenol is synthesized as a probe to investigate the mechanism of base-catalyzed autooxidation of phenol derivatives. Our study indicates that one electron reduction of molecular oxygen from phenolate gives phenoxyl radical 3, a key intermediate of autooxidation. The coupling of phenoxyl radical and superoxide radical gives peroxylate anion 4 and produces the final epoxy alcohol adduct 6. 相似文献
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