Reliability and Completeness of Data on the Impurity Composition of High-Purity Volatile Compounds

A procedure is proposed for assessing the completeness and reliability of data on the impurity composition of high-purity volatile substances. The procedure is illustrated with application to the samples of volatile substances (hydrides, chlorides, permanent gases, and metalorganic compounds) present at the permanent exhibition–collection of extrapure substances (ECES), Russian Academy of Sciences.     

Containerless Automated Processing of High-Purity Intermetallic Compounds and Composites

An automated containerless processing system to directionally solidify high temperature reactive materials has been previously described (1). The software used for control has: been simplified and improved over that previously reported. Temperature has been eliminated as a necessary control variable for the directional solidification process. All proportional and integral (PI) control is based upon image processing using parallel processing software. Control actions can occur several times a second using a DEC 11/23+ computer assisted by two PC's. The system has since been used to produce high-purity bulk metallurgical samples of high melting intermetallic compounds, single crystals grown from oriented seeds, and new polyphase intermetallic/metallic in-situ composites. New characteristics of the process are described; and properties of recently produced materials reviewed and related to current high temperature materials.     

High-Purity Fixed Points of the ITS-90 with Traceable Analysis of Impurity Contents

The International Temperature Scale of 1990 (ITS-90) is based on thermodynamic equilibrium states of ideally pure substances. The largest contribution to the uncertainty budgets of most metallic fixed points is the influence of impurities on the fixed-point temperature. Therefore, a traceable chemical analysis of the remaining impurities with small uncertainty is the basis of further progress. Further requirements are better knowledge of the phase diagrams at very low impurity contents, impurity segregation, and the quantification and correction of thermal effects during a fixed-point realization. In this article, current and future activities at PTB and BAM in order to develop improved metallic fixed-point cells of the ITS-90 are reviewed.     

Processes for the Preparation of High-Purity Arsenic and Its Compounds

Inorganic Materials - This paper presents results of analysis of the patent, scientific, and technical literature concerned with the physicochemical and technological foundations of the preparation...     

Thermodynamic Approach to Optimization of SrTiO3 Chemical Vapor Deposition from Volatile Metalorganic Precursors

Thermodynamic analysis is used to examine the possibility of producing SrTiO₃ films in two precursor systems containing different volatile Ti compounds: TiO(dpm)₂–Sr(dpm)₂–N₂O–Ar (I) and Ti(OPr ⁱ )₂(dpm)₂–Sr(dpm)₂–N₂O–Ar (II). The results demonstrate that, at an initial Ti : Sr atomic ratio of 1 : 1 and a ratio of flow rates /f _Ar = 1, system I contains no region of single-phase SrTiO₃ deposition. Raising the N₂O concentration in the vapor phase makes it possible to deposit SrTiO₃. System II contains a broad temperature range of SrTiO₃ deposition (400–1300 K) over the entire pressure range examined, p _total = 1–100 Pa. These conclusions are verified by depositing films in systems I and II (in particular, in system I in the presence of N₂O activated in an rf discharge). The films grown in system I are found to consist of crystalline SrTiO₃ and an amorphous phase containing residual organics, in particular in the form of CH _x groups with x = 1–3. The films produced in system II consist of nanocrystalline SrTiO₃. In this system, the equilibrium phase SrTiO₃ is formed on the substrate surface via solid-state reaction between TiO₂ and SrO intermediates. The rf activation of N₂O makes it possible to grow crystalline SrTiO₃ at much lower temperatures.     

A Computerized Suite for Analyzing High-Purity Organic Compounds by a Cryometric Method

Principles are presented that have been used in a unified system based on the AKSAMIT computer data acquisition suite. It is intended for analyzing high-purity organic substances by the cryometric method. Results are presented for K-3 benzoic acid certified as CRM GSO 5504-90.     

Statistical Phenomenology of the Elemental Composition of Environmental Systems

The impurity compositions of various environmental systems are examined. The total concentration, dispersion, and standard deviation of the impurity distributions are determined and are used to construct order series. The results demonstrate that the compositions of environmental systems are well represented by the stochastic model for purification, which corresponds to a normal integral distribution function. The processes involved are ranged according to the relative purity of the systems studied.     

挥发性有机物气体标准物质的研制

讨论了挥发性有机物(VOCs)的分析方法和分析手段,并介绍了研制的VOCs注射重量法气体配气装置.针对目前社会上急需的氮中苯、甲苯、乙苯、邻二甲苯、对二甲苯、间二甲苯、苯乙烯、正己烷、乙酸丁酯、十一烷等氮中十个组分钢瓶气体标准物质进行了研制,对提高室内外空气质量检测水平起到积极作用.     

天然燃香燃烧产物中挥发性有机物分析研究

以天然原料制作而成的5种天然燃香,燃烧后利用热脱附-气相色谱质谱联用仪测定其燃烧产物中挥发性有机物TVOC的含量。结果表明,5种天然燃香燃烧后室内空气中TVOC安全通用技术条件》标准中的限值,于原料中加入炭粉在一定程度上可以降低天然燃香燃烧后空气中TVOC的含量。     

Evolution of Near-Surface Elemental Composition Profile and Its Effect on Thermal Diffusivity

In a series of recent experiments, utilizing the method of time resolved spectroscopy of laser-produced plasma (LPP) plumes from specimen surfaces, the near-surface elemental composition profiles were observed to be nonuniform and significantly different from the respective bulk composition. A new study of three alloy systems is reported, with a view toward establishing the causal relationship between the near-surface elemental composition profile of a specimen and its thermophysical properties in general and thermal diffusivity in particular. The systems in question are as follows: two-element Nichrome ribbon; four-element magnetic Mumetal foil; and four-element Wood's alloy. The method of LPP plume spectroscopy has been used throughout to successively expose new surface layers and measure the composition and thermal diffusivity. With two of the systems, modification of the near-surface elemental composition profiles has been forced. Sustained electrical heating of a Nichrome ribbon specimenrevealed preferential diffusion of chromium to the surface, affecting the spectral emissivity and thermal diffusivity as well as depth-dependent local heating rates. In the case of Wood's alloy a sample is melted and re-solidified under a protocol that highlights gravitational forcing. The noncontact spectroscopic method has been used to discover that the top and bottom surfaces acquire two different composition profiles and exhibit commensurate disparity in the measured thermal diffusivity profiles.     

高纯三氟甲烷的制备工艺

综述了高纯三氟甲烷的制备工艺,提出了通过精馏加吸附的纯化方法,将含有二氧化碳、三氟一氯甲烷、三氟一溴甲烷、五氟乙烷、二氟一氯甲烷、二氟二氯甲烷等杂质的粗三氟甲烷,提纯到99.999%以上。     

Investigation of Sorption Microsystems as Reference Samples of Volatile Organic Compounds

Measurement Techniques - The technology of obtaining reference samples of volatile organic compounds using sorption microsystems is described. The most effective are 0.147–0.178 mm...     

Gas-Assisted IR-ATR Probe for Detection of Volatile Compounds in Aqueous Solutions

The application of the principle of solid-phase microextraction (SPME) to attenuated total reflectance (ATR) infrared (IR) probes can provide a convenient and sensitive way to detect volatile organic compounds (VOCs) in aqueous solutions. In this paper a new method to increase the performance of this type of sensing device is proposed. A stream of gas purges out VOCs from aqueous solution. These compounds are directed to an internal-reflection sensor. Several advantages are recognized by this new method as compared with a conventional liquid probe; these include a longer lifetime for the probe, higher selectivity in the detection of VOCs, less limitation in the sample volume, and easier regeneration of the sensing probe.     

基于质谱技术的植物挥发性代谢产物检测的研究现状与展望

植物释放的挥发性代谢的产物包含了植物新陈代谢的重要信息,是人类了解植物生命活动本质规律的重要窗口,是提高植物经济价值的重要物质基础,因此具有巨大的开发利用价值。本文归纳了常见植物挥发性代谢产物的产生途径,综述了常规质谱分析技术在植物挥发性代谢产物分析检测中的应用,同时结合自身研究工作,介绍了新兴复杂基体样品快速质谱分析技术的原理,展望它们在植物挥发性代谢产物检测中的发展趋势。     

水中二氯甲烷等五种挥发性有机物的测定

本文采用吹扫捕集/气相色谱/质谱法测定水中挥发性有机物,具有简便、快速、灵敏、准确等优点,适用于饮用水分析     

Electron Microscopy and Elemental Composition of the Near-Surface Layer of Electron-Irradiated LiF Crystals

Technical Physics Letters - Electron microscopy and optical vibrational spectroscopy techniques have been used to study Li nanoparticles formed on the cleaved surface of lithium fluoride (LiF)...     

镁合金消失模铸件表面膜成分及其结构

采用X射线光电子能谱技术(XPS)对消失模镁合金铸件的表面成分进行了测定,结果表明消失模镁合金铸件表面元素成分为Mg、Al、C、O、Si;结合对镁合金液和消失模样界面间的化学反应分析,揭示了消失模镁合金铸件表面是由MgO、Al2O3、SiO2和无定型C等组成的一层薄膜,即消失模镁合金铸件表面的Al2O3-SiO2-MgO-C复合膜;该复合膜对提高镁合金表面的防腐蚀性有很好的作用;提出了镁合金消失模表面膜的结构模型.这些结果表明,消失模技术作为镁合金零件的成形方法具有独特的优势.     

Separation of Trivalent Americium and Rare-Earth Elements from Iron Impurity Using Certain Coordination Compounds

A procedure was developed for separation of trivalent Am and rare-earth elements from iron, involving stabilization of iron in the Fe(II) state with hydrazine nitrate in weakly acidic solution in the presence of dimethylglyoxime or bipyridine, followed by precipitation of f elements as hydroxides. With bipyridine used as a complexone, the iron content in the recovered and washed 4f and 5f element hydroxides does not exceed 10^?6 M.