Structure and thermodynamics of hydrocarbon liquids: Computer simulation based on rism theory

A system of Ornstein-Zernike integral equations is solved numerically to determine the heats of vaporization ΔH_V of liquid ethane, propane, and n-butane. It is shown that the calculations (the deformations of valence bonds and bond angles in the liquid-phase molecules are ignored) give rather accurate values of ΔH_V, which are in agreement with the corresponding experimental data. On the other hand, it is established that if there are intramolecular rotational degrees of freedom, ΔH_V depends on the angle of internal rotation ϕ. The function ΔH_V(ϕ) is minimum for trans-conformations (ϕ=0) and maximum for cis-conformations (ϕ=180°). Hence, intermolecular interactions stabilize compact (convolute) conformations. The energy of this effect is of the order of 1 kJ/mole. Tver State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 5, pp. 808–813, September–October, 1995. Translated by I. Izvekova     

Instrumental neutron activation analysis of semiconductor grade silicon

The single comparator method in neutron activation analysis has been applied to the investigation of the purity of silicon single-crystals of different origins. The following impurities were determined: Au, Sb, Co, Cu and Na. Studies were also carried out on the surface contamination of silicon samples introduced through steps of sample preparation and irradiation. Up to nineteen elements on the surface of samples were analysed and found to be easily reduced to low levels or detection limits by washing and etching.     

Modellrechnungen zum Dendriten-Wachstum in partiell-kristallinen Hochpolymeren

Zusammenfassung Überstrukturen in partiell-kristallinen Thermoplasten liegen oft in Gestalt von Sphärolithen vor. Es wird versucht, ihre Entstehung auf behindertes Dendritenwachstum zurückzuführen. Die durch das Simulationsmodell beschriebenen Strukturen werden mit experimentell beobachteten verglichen.

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Superstructures in partial-crystalline thermoplastics often show the shape of spherulites. The reason of this can be a handicapped growth of dendrites. The structures obtained by a simulation model are compared with those obtained by experiments.

     

Catalytic activity of palladium-containing zeolites in the complete oxidation of benzene

The dependence of palladium distribution in zeolites on the temperature of thermal treatment has been established from the data on oxygen chemisorption and the statistical processing of electron micrographs. The influence of palladium distribution in zeolites on their catalytic activity towards the complete oxidation of benzene has been shown.

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Inhibierungseffekt von 1,1,4,4-Tetraphenyl-2-tetrazen bei der radikalischen Polymerisation von Styrol

Ohne Zusammenfassung