Topic
Differential scanning calorimetry
About: Differential scanning calorimetry is a research topic. Over the lifetime, 50315 publications have been published within this topic receiving 1152335 citations. The topic is also known as: DSC.
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TL;DR: In this article, the first reported crystalamorphous phase transition induced by ball-milling in a pure element: a silicon powder is presented, and the influence of the ballmilling conditions on the dynamic equilibrium between the crystalline and the amorphous phases has been studied.
Abstract: We present an experimental study of the first reported crystalamorphous phase transition induced by ball-milling in a pure element: a silicon powder. Scanning electron microscope observations show some particular spherical particles with smooth shapes. Only minor contamination with iron and chromium (less than or equal to 0.2 at.%) has been determined by chemical EDX microanalyses. The analyses of the X-ray patterns reveal the coexistence of silicon microcrystallites and an amorphous phase. Transmission electron microscope investigations (selected area diffraction patterns) show that such mixing is on the micrometer scale. The various enthalpic evolutions which have been studied by differential scanning calorimetry experiments reveal three major contributions which may be successively interpreted starting from room temperature up to 725°C as a release of the strain energy (exothermic event), followed by an equilibration between the in situ differential scanning calorimetry annealed silicon crystallites and the amorphous phase (endothermic effect), and subsequently by the crystallization of the amorphous phase (exothermic contribution). The influence of the ball-milling conditions on the dynamic equilibrium between the crystalline and the amorphous phases has been studied.
195 citations
TL;DR: In this paper, a nanocomposite of conducting polyaniline (PAN) with inorganic Na+−montmorillonite (MMT) clay was synthesized by the emulsion polymerization method.
Abstract: Nanocomposites of conducting polyaniline (PAN) with inorganic Na+−montmorillonite (MMT) clay were synthesized by the emulsion polymerization method. The dodecylbenzenesulfonic acid (DBSA) was used for both dopant and emulsifier. Analyses of X-ray diffraction patterns demonstrated that conducting PAN-DBSA was intercalated between inorganic clay layers at the nanoscale level (<10 A). We observed that the clay induced more disordered state in PAN-DBSA/clay nanocomposites. From the temperature-dependent dc conductivity [σdc(T)] experiments, we investigated charge transport mechanism of the PAN-DBSA and PAN-DBSA/clay systems. The interaction between the intercalated PAN-DBSA and the clay layers was observed by FT-IR spectra. The results of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) showed the improved thermal stability of the nanocomposite materials. The σdc of these systems was 101−10-2 S/cm at room temperature, varying with dopant molar ratio. The σdc(T) of the nanocomposite...
195 citations
TL;DR: In this paper, an advanced isoconversional method has been applied to the data in order to evaluate a dependence of the effective activation energy on the extent of conversion of diglycidyl ether of bisphenol A (DGEBA) with m-phenylenediamine (m-PDA) using dynamic rheometry and temperature modulated DSC.
Abstract: The kinetics of curing of diglycidyl ether of bisphenol A (DGEBA) with m-phenylenediamine (m-PDA) has been studied by using DSC under isothermal and non-isothermal conditions. An advanced isoconversional method has been applied to the data in order to evaluate a dependence of the effective activation energy on the extent of conversion. The method has been applied to the stoichiometric system as well as to the system with an excess of the amine. The nonstoichiometric system demonstrates an effective activation energy that is practically independent of the extent of conversion. The resulting value (≃ 55kJ.mol -1 ) provides an estimate for the curing reaction of the primary amine. The stoichiometric system demonstrates a decreasing activation energy for both isothermal and nonisothermal cures. The value varies from ≃ 55kJ.mol -1 to as low as ≃ 20kJ.mol -1 . The decrease is explained by shifting the rate determining step from a kinetic to a diffusion regime. The diffusion control is associated with the processes of pgelation and vitrification that occur on curing and cause a dramatic decrease in molecular mobility. Dynamic rheometry and temperature modulated DSC have been employed to study these processes.
195 citations
TL;DR: The elevated aggregation levels induced by salt, low pH, and high protein concentrations could be successfully predicted by this thermal stability screening and could be widely applied in the biopharmaceutical industry for formulation and process development, and characterization.
195 citations
TL;DR: Differential scanning calorimetry was used to determine the thermal transitions in fresh and freeze-dried strawberries and the moisture dependence of these transitions in this article, and the melting of ice in strawberries was similar to that in sugar solutions and fruit juices.
Abstract: Differential scanning calorimetry was used to determine the thermal transitions in fresh and freeze-dried strawberries and the moisture dependence of these transitions. The freeze-dried strawberry samples had a glass transition at 30-6O”C, and the melting endotherm of the dried products was similar to that for freeze-dried sugars. The glass transition temperature of humidified samples was a linear function of the water activity; it decreased with increasing moisture content. Ice was found to melt at a moisture content of 21.4% or above. The melting of ice in strawberries was similar to that in sugar solutions and fruit juices.
194 citations