Two-Temperature Transport Coefficients in Argon–Hydrogen Plasmas—I: Elastic Processes and Collision Integrals

The calculation of two-temperature transport coefficients in an argon–hydrogen plasma at atmospheric pressure is performed using a new theory of two-temperature transport properties recently presented. The latter takes into account the coupling between electrons and heavy species, coupling neglected in the already existing theories of Devoto and Bonnefoi. Transport coefficients are calculated at two-temperatures, the kinetic temperature of electrons T_e being different from that of heavy species T_h. This paper is divided into two parts. The first one is related to elastic processes and its aim is to compare the results obtained with this new theory for viscosity , translational thermal conductivities ^tr _e and ^tr _h and electrical conductivity with the previous results of Bonnefoi. The composition is calculated with the modified equilibrium constant of van de Sanden et al. and the most recent interaction potential are discussed. As it could be expected the electron translational thermal conductivity and the electrical conductivity calculated when taking into account or not the coupling between electrons and heavy species show non-negligible discrepancies. Besides this comparison, the results also show the drastic influence of the non-equilibrium parameter =T_e/T_h on the values of , , ^tr _e, and ^tr _h.     

Synthesis and properties of porous silica obtained by the template method

Micromesoporous samples of SiO₂ were synthesized by the sol-gel method using tetraethoxysilane as a starting reagent and 1–5 wt % cetylpyridinium chloride as a template under the conditions of preadsorption of colloid silica by polyethyleneglycol macromolecules. The adsorption and texture of the samples were studied by the low-temperature nitrogen adsorption-desorption technique. Preadsorption of silica sol was shown to affect the adsorption and capillary-condensation properties of silica. The surface area and the volume of mesopores increased at cetylpyridinium concentrations higher than 1 wt %. The micropore volume increased to a maximum. The capillary-condensation hysteresis loop of H4 type transformed into an H3 loop according to the IUPAC classification.     

Verzweigungsreaktionen bei der Vinylacetat-Polymerisation

Zusammenfassung Bei der Untersuchung der Langketten-Verzweigungsreaktionen wurde für die photosensibilisierte Substanzpolymerisation von Vinylacetat festgestellt, da? mit abnehmendem Polymerisationsgrad zunehmend C-C-Hauptketten-Verzweigungen gebildet werden. Es wird gezeigt, da? diese nicht durch Verseilung abbaubaren Verzweigungen in einer Reaktionsfolge entstehen, die mit Disproportionierungsabbruch beginnt und sich in einer Wachstumsreaktion zwischen zwei Polymerpartikeln fortsetzt. Auf die allgemeine Bedeutung dieser Hauptketten-Verzweigung wird hingewiesen.

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Summary In this paper long chain branching reactions occurring in the photosensitized bulk polymerization of vinyl acetate have been examined. The number of C-C branching points is increased by decreasing the degree of polymerization. These branching points-which cannot be hydrolized-were formed in reactions between growing polymer radicals and polymer molecules showing a terminal double bond resulting from a termination reaction by disproportionation.

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Meinem hochverehrten Lehrer, Herrn Prof. Dr. Dr. h. c.Franz Patat, danke ich für stets f?rdernde Unterstützung.     

A Bistable Microelectromechanical System Actuated by Spin-Crossover Molecules

We report on a bistable MEMS device actuated by spin-crossover molecules. The device consists of a freestanding silicon microcantilever with an integrated piezoresistive detection system, which was coated with a 140 nm thick film of the [Fe(HB(tz)₃)₂] (tz=1,2,4-triazol-1-yl) molecular spin-crossover complex. Switching from the low-spin to the high-spin state of the ferrous ions at 338 K led to a reversible upward bending of the cantilever in agreement with the change in the lattice parameters of the complex. The strong mechanical coupling was also evidenced by the decrease of approximately 66 Hz in the resonance frequency in the high-spin state as well as by the drop in the quality factor around the spin transition.     

One-pot microwave-assisted substitution of a glucuronan trisaccharide

Substitution of a glucuronic acid trisaccharide was easily performed in one step under microwave irradiation, affording a product resulting from simultaneous glycosylation, esterification and a butyl ether formation.     

Synthesis of micro/mesoporous silica using poly(ethylene glycol) as a template

Analysis of isotherms of low-temperature nitrogen adsorption-desorption has revealed the formation of a micro/mesoporous structure in silica resulting from the sol-gel transition of SiO₂ in the presence of poly(ethylene glycol)s with different molecular masses used as templates. The specific surface area of pores has been determined by the BET and Langmuir methods; the volume and surface area of micropores have been estimated by the t-plot method; and the surface area and volume of pores, mesopore size distribution, and average pore diameter have been assessed using the Barrett-Joyner-Halenda method.     

Specific features of absorption of Cu<Superscript>2+</Superscript>, Zn<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>, and Pb<Superscript>2+</Superscript> cations from aqueous solutions by calcium phosphates

Kinetic characteristics of the interaction of trisubstituted calcium phosphate Ca₃(PO₄)₂ · xH₂O with Cu²⁺, Zn²⁺, Co²⁺, and Pb²⁺ ions in aqueous solutions were studied.     

Phenomena Involved in Suspension Plasma Spraying Part 2: Zirconia Particle Treatment and Coating Formation

The first part of this paper was devoted to phenomena related to liquid injection in the Suspension Plasma Spraying (SPS) process. This second part emphasizes the solid particles treatment and the coating generation. A simplified theoretical approach is proposed to evaluate the influence of the numerous experimental parameters on heat and momentum transfers from the plasma jet to individual particles. It is shown that small solid particles vanish by vaporization and are very sensitive to plasma arc fluctuations and thermophoresis effect, which makes particles to escape from the jet. This study is completed by experimental investigations concerning, first, in-flight collection of particles and, second, coating elaboration. The importance of the particle size distribution of the injected powder and the parameters for the plasma generation is demonstrated, as their choice can give either porous or dense coatings.