Search results for "Thermal"
showing 10 items of 3576 documents
E-beam curing of epoxy based blends in order to produce high performance composites
2007
In this work, blends of a difunctional epoxy monomer and a thermoplastic toughening agent are E-beam irradiated at two different dose rates and two different total absorbed doses. The influence of the processing conditions on the thermal properties and on the morphology of the obtained matrices has been investigated. In particular, it is shown how the increase of the dose rate causes an increase of the temperature during irradiation, thus inducing a simultaneous thermal and radiation curing. On the contrary, at low-dose rate the system mainly undergoes to radiation curing, thus making the cured material very sensible to a post-irradiation thermal treatment with a significant improvement of …
Intramolecular coupling of acetylenic groups of bis(alkynyl)phosphanes and silanes mediated by benzynezirconocene: a route to new mono- and tricyclic…
2004
Benzo-zirconacyclohexadiene-phospha or silacyclobutene fused ring systems are easily prepared via a benzynezirconocene intermediate by means of thermolysis of Cp 2 ZrPh 2 in the presence of bis(alkynyl)phosphanes or silanes. These polyunsaturated systems are the source of a variety of new mono- or tricyclic heterocycles incorporating either one or two heteroatoms.
The influence of counterions and hydrophobic moieties on the thermostability of Langmuir-Blodgett multilayers
1994
Abstract Langmuir-Blodgett (LB) multilayers with various counterions and different organic moieties (one- and two-chain fatty acids, polymeric acid) are prepared to investigate on line temperature-dependent structural changes and desorption by small-angle X-ray scattering (SAXS), interference-enhanced reflection and Nomarsky microscopy. On temperature increase a sequence of phase transitions can be observed. A crystalline LB film melts to a fluid phase and eventually desorbs either from droplets or from a homogeneous film. The phase sequence depends on the counterion: nickel stearate and magnesium stearate melt while the layered structure is conserved; SAXS measurements reveal a continuous,…
Optical Hole Burning and Thermal Irreversibility of Non-Ergodic Systems: Polymers, Proteins, Glasses
1989
A spectral hole is used to probe configurational dynamics of non-ergodic systems far below the glass transition temperature
Thermal, Pressure and Light Induced Spin Transition in the Two-Dimensional Coordination Polymer [Fe(pmd)2[Cu(CN)2]2]
2008
[EN] A complete structural, calorimetric, and magnetic characterisation of the 2D coordination spin crossover polymer {Fe(pmd)(2)[Cu(CN)(2)](2)} is reported. The crystal structure has been investigated below room temperature at 180 K and 90 K, and at 30 K after irradiating the sample at low temperature with green light ( lambda = 532 nm). The volume cell contraction through the thermal spin transition is only 18 angstrom(3) which is lower than the usually observed value of around 25-30 angstrom(3) while the average Fe-N bond distances decrease by the typical value of about 0.19 angstrom. The structural data of the irradiated state indicate that the high spin state is well induced since the …
Substituent effects on axle binding in amide pseudorotaxanes: comparison of NMR titration and ITC data with DFT calculations
2012
The binding behaviour of differently substituted diamide axle molecules to Hunter/Vögtle tetralactam macrocycles was studied with a combination of NMR titration, isothermal titration calorimetry (ITC) experiments and calculations employing density functional theory (DFT), along with dispersion-corrected exchange-correlation functionals. Guests with alkyl or alkenyl chains attached to the diamide carbonyl groups have a significantly higher binding affinity to the macrocycle than guests with benzoyl amides and their substituted analogues. While the binding of the benzoyl and alkenyl substituted axles is enthalpically driven, the alkyl-substituted guest binds mainly because of a positive bindi…
Efficient Self-Assembly of Di-, Tri-, Tetra-, and Hexavalent Hosts with Predefined Geometries for the Investigation of Multivalency
2015
Coordination-driven self-assembly of differently shaped di- to hexavalent crown-ether host molecules is described. A series of [21]crown-7- and [24]crown-8-substituted bipyridine and terpyridine ligands was synthetized in a "toolbox" approach. Subsequent coordination to 3d transition metal and ruthenium(II) ions provides an easy and fast access to host assemblies with variable valency and pre-defined orientations of the crown-ether moieties. Preliminary isothermal calorimetry (ITC) titrations provided promising results, which indicated the host complexes under study to be suitable for the future investigation of multivalent and cooperative binding. The hosts described herein will also be su…
Solvothermal synthesis, crystal structure and magnetic properties of homometallic Co(II) and Cu(II) chains with double di(4-pyridyl)sulfide as bridges
2012
Abstract Two new coordination polymers {[Co(μ-4,4′-dps)2(H2O)2](NO3)2·2(4,4′-dps)·4H2O}n (1) and {[Cu(μ-4,4′-dps)2(H2O)2](NO3)2·2H2O}n (2) [4,4′-dps = di(4-pyridyl)sulfide] have been synthesized by solvothermal reactions between the nitrate salts of cobalt(II) (1) and copper(II) (2) and the 4,4′-dps molecule. Compounds 1 and 2 have been characterized by elemental analysis, thermal analysis (TG/DTA), vibrational spectroscopy, single crystal X-ray diffraction analysis and variable-temperature magnetic measurements. Compounds 1 and 2 are cationic chain compounds of formula {[M(μ-4,4′-dps)2(H2O)2]n2n+ [M = Co(II) (1) and Cu(II) (2)] with double 4,4′-dps bridges, uncoordinated nitrate anions, an…
Environmental impact of mining activities on the Hermioni area, Greece
1993
Publisher Summary This chapter investigates the environmental impact of mining activities in the Hermioni area, Greece, including the offshore area. A chemical analysis of sediments associated with diabase lavas in the Hermioni mine area has shown significant enrichments in Fe, Mn, Zn, Cu, and As relative to normal pelagic clays. Marked geographic compositional variations within the Hermioni area have been observed, the highest metal enrichments found at Baroutospelia. Mineralogically the Fe–Mn sediments contain hematite, quartz, and minor amounts of illite, smectites, and feldspars. A chemical analysis of sulfide ore samples showed that the Hermioni ores are Cu-rich pyrites, always contain…
Sustainable nanocomposites based on halloysite nanotubes and pectin/polyethylene glycol blend
2013
Abstract This study was focused on the preparation and characterization of biofilms based on pectin/polyethylene glycol 20000 (PEG) blend and halloysite nanotubes (HNTs). The obtained blends loaded with a natural nanoclay are proposed as sustainable alternative to the polymers produced from non-renewable resources such as fossil fuels. Properties of technological interest have been monitored and they were correlated to the structural features of the nanocomposites. It turned out that the wettability of the films can be tuned by changing the composition and the distribution of HNTs into the material as well as the surface roughness. The tensile properties of the blend are enhanced by the pre…