Search results for "Calorimetry"
showing 10 items of 504 documents
Quantification of low levels of amorphous content in sucrose by hyperDSC.
2005
A method was developed for the quantification of low levels of amorphous content in sucrose with hyperDSC. The method was based on the fact that the change of specific heat at the glass transition is linearly proportional to the amorphous content. It was found out that as annealing time increased, the glass transition temperature moved to a higher temperature and the change of specific heat increased. DeltaC(p) for annealed totally amorphous sucrose was 0.761+/-0.012 Jg(-1) degrees C(-1). Synthetic mixtures with various proportions of crystalline and amorphous sucrose were prepared. The following linear regression between DeltaC(p) and amorphous content was obtained: DeltaC(p)=0.0075x - 0.0…
Relationship between the Glass Transition of Myoglobin-Water-Disaccharide systems and Protein Thermal Denaturation
2009
Thermal Denaturation of Myoglobin in Water–Sugar Matrices and Relationship with the Glass Transition of the System
2009
Mechanical and thermal behaviour of networks with “flexible” and “rigid” chains
1996
“Rigid-rod” telechelics were synthesized via repetitive Diels-Alder reaction of biscyclohexadienes and bis(1,2,4-triazoline-3,5-diones). The bistriazolinediones were used in slight excess. The rigidity of the building blocks and the molecular weight were varied. Various amounts of these reactive telechelics are used to crosslink cis-1,4-polybutadiene. The mechanical and the thermal properties of these two-component networks were investigated by stress-strain, differential scanning calorimetry and dynamic-mechanical measurements. The occurrence of microphase separation between the “rigid” and the “flexible” components is discussed to explain the properties of these materials.
An experimental investigation on the poor hydrogen sorption properties of nano-structured LaNi5 prepared by ball-milling
2011
Abstract Nano-structured LaNi5 hydrogen storage materials prepared by ball-milling is analysed using differential scanning calorimetry (DSC) and x-ray photoelectron spectroscopy (XPS). DSC results indicate a partial elimination of defects at 500 °C in a more efficient way for the short-time ball-milled powders compared to the long-time ball-milled ones. XPS results show almost no change in the core-level electronic structure for La and Ni of LaNi5 in the bulk and the nano-structured forms, but gives an indication that the self-restoring mechanism of the active surface observed in the bulk sample (Siegmann et al. Phys. Rev. Lett. 40, 972) may not be occurring in the nano-powders. Results fro…
Snapshots of a solid-state transformation: Coexistence of three phases trapped in one crystal
2016
Crystal-to-crystal transformations have been crucial in the understanding of solid-state processes, since these may be studied in detail by means of single crystal X-ray diffraction (SCXRD) techniques. The description of the mechanisms and potential intermediates of those processes remains very challenging. In fact, solid-state transient states have rarely been observed, at least to a sufficient level of detail. We have investigated the process of guest extrusion from the non-porous molecular material [Fe(bpp)(HL)](ClO)·1.5CHO (bpp = 2,6-bis(pyrazol-3-yl)pyridine; HL = 2,6-bis(5-(2-methoxyphenyl)-pyrazol-3-yl)pyridine; CHO = acetone), which occurs through ordered diffusion of acetone in a c…
Structure and properties of tris(tetramethylammonium) nonabromodiarsenate(III), [(CH3)4N]3[As2Br9]
2007
The new tetramethylammonium bromoarsenate(III) crystal [(CH3)4N]3 [As2Br9] has been synthesized and its phase behaviour established by differential scanning calorimetry and dilatometry. Three phase transitions are found: at 346/346 K , at 165/171 K and at 157/165 K on cooling/heating. Single-crystal x-ray diffraction studies of phases I (at 370 K) and II (at 298 K) have shown that the structure comprises discrete [As2Br9]3− anions and disordered [(CH3)4N]+ cations. Phase II crystallizes in the polar space group P31c; its polar nature was confirmed by pyroelectric measurements. Phase I has higher symmetry, P63mc or . Dielectric dispersion measurements revealed a relaxation process in the cry…
Thermal, spectroscopic and crystallographic analysis of mannose-derived linear polyols
2018
The major diastereomer formed in the Barbier-type metal-mediated allylation of D-mannose has previously been shown to adopt a perfectly linear conformation, both in solid state and in solution, resulting in the formation of hydrogen-bonded networks and subsequent aggregation from aqueous solution upon stirring. Here, a comprehensive study of the solid state structure of both the allylated D-mannose and its racemic form has been conducted. The binary melting point diagram of the system was determined by differential scanning calorimetry analysis, and the obtained results, along with structure determination by single crystal X-ray diffraction, confirmed that allylated mannose forms a true rac…
Crystallization kinetics of iPP: Influence of operating conditions and molecular parameters
2007
An analysis of the crystallization kinetics of different grades of isotactic polypropylene (iPP) is here presented. To describe the crystallization kinetics as a function of molecular and operating parameters, the methodological path followed was the preparation of quenched samples of known cooling histories, calorimetric crystallization isotherms tests, differential scanning calorimetry cooling ramps, wide angle X-ray diffraction (WAXD) measurements, and density determination. The WAXD analysis performed on the quenched iPP samples confirmed that during the fast cooling at least a crystalline structure and a mesomorphic one form. The diffractograms were analyzed by a deconvolution procedur…
Characterization of Dielectric Anomaly in Solid Solution Based on BaTiO3
2011
The influence of Zr doping on a structure and dielectric properties of Ba0.8Sr0.2TiO3 were studied. For this purpose Ba0.8Sr0.2Ti0.75Zr0.25O3 ceramics were obtained by a conventional method and were determined by an X-ray diffraction (XRD) and scanning electron microscopy (SEM) for crystallographic, surface morphological and compositional studies. The temperature and frequency dependence of dielectric permittivity were studied in the temperature range from 150 to 500 K and the frequency between 20 Hz and 1000000 Hz. The thermal behavior of the Ba0.8Sr0.2Ti0.75Zr0.25O3 ceramics were also studied using Differential Scanning Calorimetry. A diffusivity coefficient γ was calculated.