О МЕХАНИЗМЕ ОБРАЗОВАНИЯ МОЛЕКУЛ SrF ПРИ ЭЛЕКТРОТЕРМИЧЕСКОМ МОЛЕКУЛЯРНО-АБСОРБЦИОННОМ ОПРЕДЕЛЕНИИ ФТОРА

Thermochemical processes accompanying the formation of gaseous molecules SrFg at the electrothermal determination of fluorine via the molecular absorption were investigated using equilibrium thermodynamic modeling. The algorithm of modeling was developed.For carrying out the calculations non-equilibrium thermodynamic system realized in graphite furnace was divided into serial quasi-equilibrium thermodynamic subsystems. These subsystems correspond to the major stages of temperature-time program: drying of the sample, pyrolysis, vaporization and gaseous dimer molecule formation. Original chemical compound of thermodynamic subsystems during modeling, method for its realization and treatment of calculated data were recommended for each stage. The evaluation of modeling accuracy was carried out using published experimental data and the results of our own experiments.Theoretically according to our experimental cases of mixed and separated injection of Sr(NO3)2  and  NaF solutions on different area platform of graphite furnace were examined. The carried out calculations made it possible to establish the composition of condensed residues after stages of drying and pyrolysis, gas phase composition of the analytical zone of graphite furnace at the stage of evaporation and molecules formation. It has been established that molecules SrFg formation happens due to thermal decomposition of condensed SrF2c for the mixed injection of solutions and interaction gaseous compounds of fluorine with   Srg   for the separated injection of solutions.The proposed algorithm may be used for research of other dimer molecules formation in a graphite furnace. The results of modeling may be useful for the selection of temperature-time program of heating, method of calibration, increasing the sensitivity and accuracy of halogens determination. Key words: fluorine, strontium, dimer molecules, molecular absorption, graphite furnace, thermodynamic modeling, interference gallium, temperature of drying, pyrolysis and evaporation.(Russian)DOI: http://dx.doi.org/10.15826/analitika.2014.18.3.005 P.V. Zaitceva, A.A. Pupyshev, Iu.А. KurmachevFederal State Autonomous Educational Institution of Higher Professional Education «Ural Federal University named after the first President of Russia B.N. Yeltsin» (UrFU), Ekaterinburg, 620002, Russian Federation Методом равновесного термодинамического моделирования изучены термохимические процессы, сопровождающие образование газообразных молекул SrFg при электротермическом молекулярно-абсорбционном определении фтора. Разработан алгоритм моделирования. Расчеты выполнены с помощью программного комплекса HSC 6.1 с собственной базой термодинамических данных.Для проведения расчетов неравновесную термодинамическую систему, реализуемую в графитовой печи, разбивали на последовательные квазиравновесные термодинамические подсистемы,  соответствующие основным стадиям температурно-временной программы: высушивание пробы, пиролиз, испарение и образование газообразных димерных молекул. Для каждой стадии рекомендован исходный химический состав термодинамических подсистем при проведении моделирования, способ его реализации и обработки расчетных данных. Оценку правильности моделирования проводили по опубликованным и собственным экспериментам.Теоретически, в соответствии с экспериментом, рассмотрены случаи совместного внесения растворов Sr(NO3)2 и NaF на один участок и раздельное внесение этих растворов на разные участки платформы графитовой печи. Проведенные расчеты позволили установить состав конденсированных остатков после стадий высушивания и пиролиза, состав газовой фазы аналитической зоны графитовой печи на стадии испарения и образования молекул. Установлено, что образование молекул SrFg происходит за счет термического разложения конденсированного SrF2c при совместном введении растворов и взаимодействия газообразных соединений фтора с Srg  – при раздельном.Правильность предложенного алгоритма моделирования подтверждена сопоставлением с экспериментальными температурными кривыми пиролиза и образования молекул SrFg, проявлением матричных помех от галлия. Предложенный алгоритм может быть использован для изучения образования других димерных молекул в графитовой печи. Результаты моделирования полезны для выбора температурно-временной программы нагрева, способа градуировки, повышения чувствительности и точности определения галогенов.Ключевые слова: фтор, стронций, димерные молекулы, молекулярное поглощение, графитовая печь, молекулярно-абсорбционный анализ, термодинамическое моделирование, помехи галлия, температуры сушки, пиролиза и испарения.DOI: http://dx.doi.org/10.15826/analitika.2014.18.3.005

EFFECT OF DENDRITIC SEGREGATION ON THE STRUCTURE AND PROPERTIES OF HEAT-RESISTANT STEEL 15H2NMFA

The features of the development of dendritic segregation of reactor steel for use in atomic energy have been investigated. Samples of low-alloyed steel of pearlite class — 15H2NMFA were used as materials for research. The studies were based on the results of metallographic analysis, using scanning electron microscopy and durometric analysis.Исследованы особенности развития дендритной ликвации реакторной стали для использования в атомной энергетике. В качестве материалов для проведения исследований использовались образцы из низколегированной стали перлитного класса — 15Х2НМФА. Исследования были основаны на результатах металлографического анализа, метода растровой электронной микроскопии и дюрометрического анализа

Sub-threshold resonances in few-neutron systems

Three- and four-neutron systems are studied within the framework of the hyperspherical approach with a local S-wave nn-potential. Possible bound and resonant states of these systems are sought as zeros of three- and four-body Jost functions in the complex momentum plane. It is found that zeros closest to the origin correspond to sub-threshold (nnn) (1/2-) and (nnnn) (0+) resonant states. The positions of these zeros turned out to be sensitive to the choice of the $nn$--potential. For the Malfliet- Tjon potential they are E(nnn)=-4.9-i6.9 (MeV) and E(nnnn)=-2.6-i9.0 (MeV). Movement of the zeros with an artificial increase of the potential strength also shows an extreme sensitivity to the choice of potential. Thus, to generate ^3n and ^4n bound states, the Yukawa potential needs to be multiplied by 2.67 and 2.32 respectively, while for the Malfliet-Tjon potential the required multiplicative factors are 4.04 and 3.59.Comment: Latex, 22 pages, no PS-figures, submitted to J.Phys.

Use of Multilinear Calibration in Atomic Emission Spectral Analysis of Ferroboron

An article is focused on the possibility of using multi-line calibration and its advantage over one-line on the example of ferroboron analysis. The influence of operational spectrometer parameters on intensity of analytical lines is investigated

OPTIMIZATION OF THE TEMPERATURE-TIME PROGRAM FOR ELECTROTHERMAL MOLECULAR ABSORPTION DETERMINATION OF IODINE

Various experimental factors influencing the shape of the pyrolysis curve for the BaI molecule were studied in this paper. Dividing the pyrolysis stage into two stages and increas-ing the cleaning time made it possible to optimize the pyrolysis curve

Prospects in Analytical Atomic Spectrometry

Tendencies in five main branches of atomic spectrometry (absorption, emission, mass, fluorescence and ionization spectrometry) are considered. The first three techniques are the most widespread and universal, with the best sensitivity attributed to atomic mass spectrometry. In the direct elemental analysis of solid samples, the leading roles are now conquered by laser-induced breakdown and laser ablation mass spectrometry, and the related techniques with transfer of the laser ablation products into inductively-coupled plasma. Advances in design of diode lasers and optical parametric oscillators promote developments in fluorescence and ionization spectrometry and also in absorption techniques where uses of optical cavities for increased effective absorption pathlength are expected to expand. Prospects for analytical instrumentation are seen in higher productivity, portability, miniaturization, incorporation of advanced software, automated sample preparation and transition to the multifunctional modular architecture. Steady progress and growth in applications of plasma- and laser-based methods are observed. An interest towards the absolute (standardless) analysis has revived, particularly in the emission spectrometry.Comment: Proofread copy with an added full reference list of 279 citations. A pdf version of the final published review may be requested from Alexander Bol'shakov <[email protected]