Search results for "visual_art"

Über die polymeranaloge bromierung von naturkautschuk und einige lösungseigensch aften des bromkautschuks. Über die molekularen konstanten von naturk…

1961

Naturkautschuk last sich in verdunnter Losung in Cyclohexan bromieren, wobei das Molekulargewicht entsprechend dem Bromgehalt zunimmt (polymeranaloge Umsetzung). Fur Bromkautschuk steigenden Bromgehalts wird Cyclohexan ein zunehmend schlechteres Losungsmittel, was sich in einer Abnahme des 2. osmotischen Virialkoeffizienten und einer Kontraktion des Molekulknauels zeigt. Dieses Ergebnis wird in quantitativer Ubereinstimmung durch Viskositats- und Lichtstreuungsmessungen erhalten. Cyclohexanlosungen von Bromkautschuk mit 43% Brom haben bei Zimmertemperatur einen Θ-Punkt. In diesem Zustand ist der Knauel 1,74mal groser als bei freier Drehbarkeit, in ziemlich guter Ubereinstimmung mit dem an a…

1982

Self-lubricating epoxide composites Kompozyty epoksydowe o właściwościach samosmarujących

2015

A com. epoxy resin was modified by addn. of aliph. polyamine, graphite, a poly-α-olefin oil and phosphate fire retardant, cured at 130°C and studied for friction coeff. in contact with steel, heat resistance and mech. strength. The addn. of graphite resulted in a decrease in the resin hardness, impact strength and friction coeff.

Structure and mechanical properties of Al–B composite powder

1997

Abstract Al-B composite powder has been obtained by crushing pieces of composite material presenting industrial waste. Structural peculiarities and microhardness of separate powder particles (d∼1 mm) have been investigated. Original design of high precision microhardness tester made it possible to detect the properties of powder both in near-surface layer and below it. The powder represents a new structurally non-homogenous material with the increased microhardness (1.5 GPa) which grows up to 4 GPa in near-surface layers. Stable oxide compounds are formed on internal surfaces and defects of the aluminium alloy. Powder compacts were obtained. Adhesion on Al–B and Al–Al interfaces at various …

1978

For the three different cases (R=polybutadiene, polypropylene oxide and EPDM) the isothermal cloud point curves of the system styrene/polystyrene/rubber (S/PS/R) show that at 25°C a decomposition into two phases occurs already in the presence of a few percents of polystyrene and rubber. By separating the phases (centrifuge) and analysis of coexisting phases, tie lines and thus critical points could be fixed. Evaluation of the results was made on the basis of the Flory and Huggins theory by means of approximations given for such systems by Scott. The interaction parameters resulting for 25°C are well in agreement with literature data—as far as available. By means of the approximations mentio…

Cyclam-strapped porphyrins and their iron(III)-copper(II) complexes as models for the resting state of cytochrome c oxidase

1999

International audience; The ESR study of two cyclam-strapped porphyrins in which, on one side, the cyclam is attached with a variable length linker to the porphyrin and, on the other side, a non-coordinating strap protects the iron from any intermolecular interaction, is reported. Variation of the linker length is made possible by the use of either a Michael reaction or a nucleophilic substitution, leading respectively to three or two carbon atom links. It is shown that in the case of the shortest link, the oxidized ironÈcopper complex exhibits a spin interaction. The distance between thetwo metal centers is evaluated to be around 4.5 Å, a value consistent with the one found in the natural …

Halogen bond preferences of thiocyanate ligand coordinated to Ru(II) via sulphur atom

2017

Halogen bonding between [Ru(bpy)(CO)2(S-SCN)2] (bpy = 2,2’-bipyridine), I2 was studied by co-crystallising the metal compound and diiodine from dichloromethane. The only observed crystalline product was found to be [Ru(bpy)(CO)2(S-SCN)2]⋅I2 with only one NCS⋅⋅⋅I2 halogen bond between I2 and the metal coordinated S atom of one of the thiocyanate ligand. The dangling nitrogen atoms were not involved in halogen bonding. However, computational analysis suggests that there are no major energetic differences between the NCS⋅⋅⋅I2 and SCN⋅⋅⋅I2 bonding modes. The reason for the observed NCS⋅⋅⋅I2 mode lies most probably in the more favourable packing effects rather than energetic preferences between …

Temperature-Induced Structural Transitions in the Gallium-Based MIL-53 Metal–Organic Framework

2013

We report a structural and thermodynamic investigation of the phase behavior of Ga(OH,F)-MIL-53, a gallium-based metal–organic framework (MOF) having the MIL-53 topology containing 0.7 wt % fluorine bonded to the metal. Despite some small structural differences, especially for the hydrated form, the overall physical chemistry behavior of Ga(OH,F)-MIL-53 is very similar to standard fluorine free Ga-MIL-53 material. A combination of in situ X-ray diffraction, in situ Fourier transform infrared spectroscopy, differential scanning calorimetry, and heat capacity measurements allowed us to establish that Ga(OH,F)-MIL-53 under vacuum (i.e., the empty material) exhibits two stable phases: a nonporo…

l-Arabinose Conformers Adsorption on Ruthenium Surfaces: A DFT Study

2012

Adsorption of 5 L-arabinose tautomers – one acyclic and four cyclic (α and β, pyranose and furanose) species – on a ruthenium surface was studied as a precursor-process of the, nowadays more and more, industrially important sugar catalytic hydrogenation on metal surfaces in water medium. The study was mostly referred to a 37-atom metal catalyst fragment, even though border-effects on the adsorption processes were also checked employing a 61-atom metal fragment. In order to figure out conformational effects on the title process the tautomer flexibility was, at first, investigated by the genetic-algorithm based code Balloon, considering the conformational spaces of the different aquo tautomer…

Selective Cobalt over Nickel separation using neat and confined ionic liquids

2020

International audience; Task Specific Ionic Liquids (TSILs) generated by association between tetraalkylammonium cations and coordinating anions such as dicyanamide (Dca-) and thiocyanate (SCN-) were used for the selective separation of Ni(II) over Co(II). SCN-based TSIL presents higher extraction efficiency than the Dca-based one towards Co(II) (E = 85.4 % vs 54.6 %) and Ni (II) (E = 22 % vs 0.5%) but lower separation factors (βCo/Ni = 21 vs 239). Interestingly, extraction of Co(II) and Ni(II) in Dca-based TSIL can be enhanced using salts with chaotropic anions such as NaNO3 (E > 90 % for Co(II) and E = 85% for Ni(II)). The use of NaCl allows, moreover, the efficient separation of both ions…