Search results for "calor"

1992

The synthesis and the results of the structural study of two copolysiloxanes with laterally fixed trinitrofluorenone (TNF) units is reported. The two copolysiloxanes having 2,4 (1a) and 5,3 (1b) dimethylsiloxane comonomer units per TNF side group differ significantly in their phase behaviour as evident from optical microscopy, differential scanning calorimetry and X-ray scattering: 1b shows a nematic mesophase whereas 1a is an amorphous material. The different phase behaviour is discussed in terms of microphase separation between the siloxane backbone and TNF side groups.

On lead-scandium tantalate solid solutions with high electrocaloric effect

1992

Abstract The PbSc0,5Ta0,5O3 solutions are found to be a useful material for active elements of microcryogenic devices based on electrocaloric effect. A temperature difference of ΔT = 1. 0-1.8 K at field intensities 20–30 kV/cm in the interval of 210–310 K can be achieved by simultaneous or separate introducing of Sb and Co ions in B-sites of the lattice. The most important contribution to the electrocaloric effect is due to field-induced Fn3m → R3m phase transition in the case of high ordering of B-ions in the perovskite structure ABO3.

Über die lösungswärme von polystyrol in verschiedenen lösungsmitteln

1951

An einem Polystyrol mit einem Molekulargewicht von ca. 20 000 werden die Losungs-warmen in verschiedenen Losungsmitteln in einem Kalorimeter bestimmt. Die meisten Losungsvorgange verlaufen exotherm, in einem Fall (Cyclohexan) wird jedoch bei der Auflosung Warme von der Umgebung aufgenommen. Es wird festgestellt, das die Trocknung der Praparate sehr wichtig fur die Reproduzierbarkeit der Messungen ist. Ferner wird orientierend die Abhangigkeit der Losungswarme vom Polymerisationsgrad sowie von der Konzentration der entstehenden Losung festgestellt. Es wird auserdem orientierend die Mischungswarme von Athylbenzol in verschiedenen Losungsmitteln bestimmt. Measurements of the heat of solution o…

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…

Macro-micro relationship in nanostructured functional composites

2012

This paper examines the results of the characterization of two functional composites: Poly(methyl methacrylate) (PMMA)-Ce:YAG (yttrium aluminium garnet doped with cerium) and PMMA-cobalt hexacyanoferrate (CoHCF). The composites were prepared as possible emitters in the fields of lighting thermal sensors. The prepared composites were char- acterized using transmission electron microscopy (TEM), nuclear magnetic resonance (NMR) spectroscopy, thermogravi- metric analysis (TGA), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) analyses to study the correlation between micro and macro characteristics. We found that the molecular interactions of the two different fill…

Demo 75. Propiedades térmicas

2013

Objetivo: Estudiar la conductividad térmica y el calor específico de varios materiales.

Single π0 production off neutrons bound in deuteron with linearly polarized photons

2021

The quasifree γ→d→π0n(p) photon beam asymmetry, Σ, has been measured at photon energies, Eγ, from 390 to 610 MeV, corresponding to center of mass energy from 1.271 to 1.424 GeV, for the first time. The data were collected in the A2 hall of the MAMI electron beam facility with the Crystal Ball and TAPS calorimeters covering pion center-of-mass angles from 49∘ to 148∘. In this kinematic region, polarization observables are sensitive to contributions from the Δ(1232) and N(1440) resonances. The extracted values of Σ have been compared to predictions based on partial-wave analyses (PWAs) of the existing pion photoproduction database. Our comparison includes the SAID, MAID and Bonn–Gatchina anal…

Apprendimento basato sull'indagine dei fenomeni termici di dissoluzione

2014

Preparation and physico-chemical study of inclusion complexes between idebenone and modified beta-cyclodextrins

1996

The inclusion properties of modifiedβ-cyclodextrins (trimethyl-β-cyclodextrin, dimethyl-β-cyclodextrin and hydroxypropyl-β-cyclodextrin) towards idebenone were compared with naturalβ-cyclodextrin. The inclusion complexes were prepared by different methods (coprecipitation, kneading, and freeze-drying) and characterized by differential scanning calorimetry, X-ray diffractometry, UV, CD and NMR spectroscopy. The results obtained by CD and NMR spectroscopy indicate a different orientation of idebenone in dimethyl-β-cyclodextrin with respect to other cyclodextrins. Stability constants of the complexes were determined in water at various temperatures and consequently thermodynamic parameters wer…

Structural, thermal and photomagnetic properties of spin crossover [Fe(bpp)2]2+ salts bearing [Cr(L)(ox)2]- anions

2009

International audience; This paper is divided into two parts: in the first part, the influence of solvate molecules on the magnetic properties of spin crossover salts of [Fe(bpp)(2)][Cr(L)(ox)(2)]ClO(4) x nS (bpp = 2,6-bis(pyrazol-3yl)pyridine; L = 2,2'-bipyridine (bpy) or 1,10-phenanthroline (phen); ox = oxalate dianion; S = solvent) is analyzed. The second part is devoted to the photomagnetic properties of the previously reported [Fe(bpp)(2)][Cr(L)(ox)(2)](2) family of compounds. The study describes the crystal structure, differential scanning calorimetry (DSC) and magnetic properties of [Fe(bpp)(2)][Cr(bpy)(ox)(2)]ClO(4) x EtOH x 4 H(2)O (1) and [Fe(bpp)(2)][Cr(phen)(ox)(2)]ClO(4) x 1.5 …