Search results for "NUMBER"
showing 10 items of 3939 documents
ChemInform Abstract: Synthesis, Structures and DFT Calculations on Alkaline-Earth Metal Azide-Crown Ether Complexes.
2008
The first examples of azide complexes of calcium, strontium or barium with crown ethers have been prepared and fully characterised, notably [Ba([18]crown-6)(N3)2(MeOH)], [Sr([15]crown-5)(N3)2(H2O)], [Ca([15]crown-5)(N3)2(H2O)] and [Sr([15]crown-5)(N3)(NO3)]. Crystal structures reveal the presence of a variety of coordination modes for the azide groups including 1-, -1,3- and linkages via H-bonded water molecules, in addition to azide ions. The [Ba([18]crown-6)(N3)2(MeOH)]1/3 MeOH contains dinuclear cations with three -1,3-NNN bridges, the first example of this type in main group chemistry. The structures obtained have been compared with molecular structures computed by density functional th…
Mechanical Properties of Composite SPEEK Polymer Membranes Modified with Ionic Liquids
2015
In this work, the mechanical properties of sulphonated polyetheretherketone (SPEEK) membranes impregnated with 3 different ionic liquids (1-butyl-2,3-dimethyl- imidazolium dimethylphosphate ([BMMIM][Me2PO4])), 1,2,3-trimethylimidazolium dimethylphosphate ([MMMIM][Me2PO4])), 1,3-dimethylimidazolium dimethylphosphate ([MMIM][Me2PO4])) have been investigated. Prepared SPEEK/ionic liquid composite membranes are characterized by mechanical testing both in room and elevated temperatures. It was found that the stiffness and tensile strength of composites decreased by increasing the content of ionic liquid and the length of alkyl radical in ionic liquid as well as by increasing the temperature.
Photocrosslinkable dextran hydrogel films as substrates for osteoblast and endothelial cell growth
2012
Functional hydrogel films on solid supports are versatile materials with large potential for cell growth and tissue engineering. Here, we report on a modular approach to generate functional hydrogel composite films for endothelial and osteoblast cell co-culture. The polymer network of the parent hydrogel was formed by a dextran derivative (BP-CMD), which contained carboxymethyl (CM) groups for further chemical functionalization and benzophenone (BP) moieties as a photocrosslinkable unit. BP-CMD could be synthesized by three different routes, first with the benzophenone unit attached via an amide bond, or second by an ether bond, or third as an ion pair between the benzophenone ammonium salt…
On the Mechanism of Xylene Isomerization and its Limitations as Reaction Test for Solid Acid Catalysts
1993
The kinetics of the gas-phase isomerization of m-xylene, over a series of ultraestable Y zeolites, has been studied in a fixed-bed flow reactor under initial conditions. Using deuterated p-xylene as reactant it has been seen that more than 20% of the m- and o-xylene obtained, are formed via a bimolecular mechanism. The relative proportion of uni- to bimolecular mechanism depends on the zeolite composition. The relation between the turnover number, calculated from the kinetic rate constant for the unimolecular mechanism, and the framework Al content of the zeolite, was coincident with the topological zeolite model. Besides, the values of the adsorption constants indicate that dealumination h…
Formation of α-ω(4,7,10,13-pentaoxa-16-azacyclooctadecane) hexadecane micelles in aqueous solution – effect of HCl addition
2003
The structure of aggregates of a new bolaform surfactant [α-ω (4,7,10,13-pentaoxa-16-azacyclooctadecane) hexadecane] in neat aqueous solution has been investigated by small-angle neutron scattering. Preliminary data analysis unequivocally indicates that globular micelles are formed. This finding has been confirmed by the analysis of data obtained upon addition of hydrochloric acid. The observed significant reduction of micelle aggregation number has been attributed to the peculiar complexing ability of the two aza-crown ether units in the surfactant molecule; this is in line with information inferred from the complexation of ions into the non alkylated azacrown ethers. As a consequence of h…
Isobaric vapor-liquid equilibria for binary systems composed of octane, decane, and dodecane at 20 kPa
1996
Vapor−liquid equilibria were measured for binary systems of octane + decane, decane + dodecane, and octane + dodecane at 20.00 kPa using a recirculating still. The results are thermodynamically consistent according to the point-to-point consistency test, and deviation from ideal behavior is small for all systems.
Extraction Chromatographic Behavior of Rf, Zr, and Hf in HCl Solution with Styrenedivinylbenzene Copolymer Resin Modified by TOPO (trioctylphosphine …
2010
It is of great interest to study chemical properties of the transactinide elements with atomic numbers (Z) ≥ 104. One of the most important subjects is to establish the position of the elements at the extreme end of the periodic table. To this end we perform studies of chemical properties of these transactinides and compare them with those of their lighter homologues and with the ones expected from extrapolations in the periodic table. So far, chromatographic studies of the transactinides have provided experimental proof of placing rutherfordium (Rf, Z = 104) through hassium (Hs, Z = 108) into groups 4 to 8, respectively. 1-10 Quite recently, copernicium (Cn, Z = 112) has been shown to be a…
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 …
Soda-AQ pulping of reed canary grass
2001
Abstract Delignification of reed canary grass (Phalaris arundinacea L.) was carried out by conventional soda-anthraquinone (AQ) pulping under varying conditions selected according to an orthogonal experimental design with four factors (cooking parameters) at three levels each L9 (34). The influence of these four parameters, i.e. effective alkali, EA (12, 15, and 18% on oven dried (o.d.) reed, as NaOH), maximum temperature (145, 155, and 165°C), time to maximum temperature (70, 90, and 110 min), and time at maximum temperature (0, 15, and 30 min) on the pulp properties (yield, kappa number, and viscosity) was studied. Results indicated that, with respect to delignification, EA was the most i…
Mechanical properties and XRD of Nafion modified by 2-hydroxyethylammonium ionic liquids
2013
In this work, the Nafion 112 membrane impregnated with 2-hydroxyethylammonium carboxylate ionic liquids have been investigated. The used ionic liquids were 2-hydroxyethylammonium formate [HEA]F, acetate [HEA]A and lactate [HEA]L. Prepared composite membranes Nafion/ionic liquid are characterized by mechanical testing, such as tensile test and creep test. It is found that ionic liquids decrease elastic modulus and creep compliance, but do not have significant effect on the tensile strength. Also, composite membranes were studied by wide angle X-ray diffraction. All ionic liquids shift the peak maximum to the lower angle. In this work, only biodegradable ionic liquids were used for composite …