Formation of a Ti-siliceous trimodal material with macroholes, mesopores and zeolitic features via a one-pot templating synthesis

Based on a facile one-pot templating synthesis, using a TS-1 zeolite recipe whereby part of the zeolite structure directing agent is replaced by a mesopore templating agent, a trimodal material is formed. The resulting meso-TSM material combines mesoporosity (Ti-MCM-41) with zeolitic features (TS-1) and a unique sheet-like morphology with uniform macroporous voids (macroholes). Moreover, the macrohole formation, mesoporosity and zeolitic properties of the meso-TSM material can be controlled in a straightforward way by adjusting the length of the hydrothermal treatment. This newly developed material may imply great potential for catalytic redox applications and diffusion limitated processes because of its highly tunable character in all three dimensions (micro-, meso- and macroporous scale).     

A scientific application oriented classification for metal transfer modes in GMA welding

In this work, metal transfer in solid wire GMA welding was studied. Several experiments with different combinations of gas-wire-parameters were carried out to observe metal transfer and to characterize the various transfer modes. A laser shadograph system with synchronized electrical signals and high speed filming were used. New modes were observed and their particular characteristics described for completeness. A classification for metal transfer, oriented to scientific personnel (researchers, scholars and students), is proposed, in which the modes are independent of the type of shielding gas or welding power source.     

Production of Biomass-Derived Chemicals and Energy: Chemocatalytic Conversions of Glycerol

The growing production of biodiesel as a renewable source-based fuel leads to an increased amount of glycerol. Thus, it is a favorable starting material to obtain highly functionalized products. From a variety of catalytic reactions three examples, namely glycerol oxidation, glycerol hydrogenolysis and aqueous-phase reforming, were chosen for detailed studies in our group. The experimental focus for the oxidation of glycerol was set on preparation and detailed examination of supported Pt–Bi catalysts in batch reactions as well as in continuous experiments using a trickle bed reactor. For aqueous-phase reforming of glycerol to hydrogen the addition of tin to supported platinum catalysts was investigated. Ruthenium and copper based catalysts could be successfully applied in the hydrogenolysis of glycerol to 1,2-propanediol.     

Joint strength optimization by the mixed-adhesive technique

An ideal adhesive lap joint is one in which the adhesive flexibility and strength properties vary along the overlap length. Because of greater adhesive shear strains at the edges of the overlap, a ductile and flexible adhesive should be used at the overlap ends, while in the middle a stiff and less-ductile adhesive should be used. This technique has been investigated in the past but only a few studies have reported any experimental evidence. In the present study, single-lap adhesive joints were manufactured and tested maintaining the same brittle adhesive in the middle of the overlap and using three different ductile adhesives of increasing ductility at the ends of the overlap. A simple joint strength prediction is proposed for mixed-adhesive joints. The mixed-adhesive technique gives joint strength improvements in relation to a brittle adhesive alone in all cases. For a mixed adhesive joint to be stronger than the brittle adhesive and the ductile adhesive used individually, the load carried by the brittle adhesive must be higher than that carried by the ductile adhesive.     

Improving the tensile strength of carbon nanotube spun yarns using a modified spinning process

A modified process for the dry spinning of carbon nanotube (CNT) yarn is reported. The approach gives an improved structure of CNT bundles in the web drawn from the CNT forest and in the yarn produced from the twisted web leading to improved mechanical properties of the yarn. The process enables many different mechanical and physical treatments to be applied to the individual stages of the pure CNT spinning system, and may allow potential for the development of complex spinning processes such as polymer-CNT-based composite yarns. The tensile strength and yarn/web structure of yarn spun using this approach have been investigated and evaluated using standard tensile testing methods along with scanning electron microscopy. The experimental results show that the tensile properties were significantly improved. The effect of heat treatments and other yarn constructions on the tensile properties are also reported.     

Gold nanoclusters as colloidal catalysts for oxidation of long chain aliphatic 1,2-diols in alcohol solvents

Long chain aliphatic 1,2-diols like 1,2-hexanediol and 1,2-octanediol can be converted to the corresponding α-hydroxy-alkanoates with total chemoselectivity, in an oxidation catalyzed by an aqueous gold sol under O₂ atmosphere. The sol is stabilized with poly(vinylalcohol), and the reaction is performed in alcohol solvents. Two methods are proposed for the efficient recycling of the colloidal Au catalyst. Firstly a solvent-resistant membrane filtration can be applied. As the membrane material, poly(dimethylsiloxane) is chosen. Secondly, in appropriate conditions, the reaction proceeds in the liquid biphasic mode, and the aqueous Au sol can be recycled by phase separation. Using either of both approaches, the colloidal stability and catalytic activity can be preserved over several recycles.     

Hydroxytelechelic hydrocarbon copolymers with high aging resistance for elastomeric materials

Dihydroxytelechelic copolyalkenamers were prepared via metathetical polymerization of cyclic olefins (cyclooctadiene, cyclooctene and cyclododecene) in presence of first generation Grubbs catalyst and butene diacetate as functionalizing chain transfer agent in order to study their aging resistance. The influence of compositions and molar masses of the copolyalkenamers were investigated in terms of thermo‐mechanical properties. Increasing chains length or the proportion of polycyclooctadiene allow to get non‐cristalline polymers. Low T_g materials (between ?78°C and ?108°C) were prepared. The resistance towards oxidation of the different copolyalkenamers was carried out using a viscosity measurement method. A critical time, corresponding to a brutal increase of the apparent viscosity, was related to degradation of the polymers and was shown to be dependent on the Csp² proportion in the structure. The absence of vinylic units and the decrease of the double bonds content within the copolymers were proved to enhance the stability of the copolyalkenamers towards aging resistance. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010