Authors:A. Foppoli, L. Zema, A. Maroni, M. Sangalli, M. Caira, and A. Gazzaniga
hydrated form of theophylline-7-acetic acid obtained by recrystallization from water. In particular this study is aimed towards the characterization of the new form as well as providing information on its physical stability and dehydration kinetics
), (c) melting–recrystallization–remelting mechanism during the DSC heating process, (d) physical aging or/and relaxation of the rigid amorphous fraction, (e) different molecular weight species, and (f) orientation effects and so forth.
Authors:M. Gazzano, M. Soccio, N. Lotti, L. Finelli, and A. Munari
as the result of the melting of crystals of higher stability and perfection, grown during the heating run as a consequence of recrystallization or reorganization of crystals initially formed during isothermal crystallization. Finally, in the case of
Authors:Stefano Gialanella, Fabrizio Girardi, Gloria Ischia, Ivan Lonardelli, Maurizio Mattarelli, and Maurizio Montagna
slightly. This would indicate that at least two different kinds of defects are present. As observed in TEM images, at 1,000 °C, hematite grains are fully recrystallized and partially sintered ( Fig. 7 ). The intensity of the 660 cm −1 peak is influenced by
Authors:Christelle Herman, Tom Leyssens, Valérie Vermylen, Véronique Halloin, and Benoît Haut
successively recrystallizes into stable form II crystals; this phenomenon, called beta-recrystallization, is characterized by the (exothermic) peak numbered 3 in Fig. 5 [ 13 ]. The last (endothermic) peak (numbered 4 in Fig. 5 ) corresponds to the melting of
increase with the increase in cooling rate. In Fig. 1b , there exist exothermic peaks of re-crystallization in the DSC traces of P4MP1 after 2.5, 5, 10, 20 K min −1 . At a same heating rate of 10 K min −1 , the re-crystallization makes the X c almost
The DSC characterisation of the morphology of the metastable a phase of stoichiometric nickel sulphide was carried out using
two calorimeters; a TA Instruments 2920 MDSC and a Perkin Elmer DSC-7, and two quenching histories. Based on these quenching
histories, significant differences were observed in the heat flow curves, including the observation of a second exothermic
peak which is tentatively assigned to be a metastable phase to metastable phase transformation. The kinetic constants for
the a to b recrystallisation were determined as a function of degree of conversion using a mechanism free isoconversional
model. Variations in the values of the kinetic constants were also ascribed to the quenching histories. Although the differences
in morphology observed were ascribed to the processing history, the shift in the position of the a to b recrystallisation
peak was partially attributed to the thermal resistances of the instruments used.
Thermal properties of food systems are important in understanding relationships between food properties and changes in food quality. Concentrated food systems (low-moisture and frozen foods) are seldom in an equilibrium state and they tend to form amorphous, non-crystalline structures. Several glass transition-related changes in such foods affect stability, e.g., stickiness and caking of powders, crispness of snack foods and breakfast cereals, crystallisation of amorphous sugars, recrystallisation of gelatinised starch, ice formation and recrystallisation in frozen foods and rates of non-enzymatic browning and enzymatic reactions. Relationships between glass transition, water plasticisation and relaxation times can be shown in state diagrams. State diagrams are useful as stability or quality maps and in the control of rates of changes in food processing and storage.
Authors:P. Šimon, P. Thomas, J. Okuliar, and A. Ray
An incremental integral isoconversional method for the determination of activation energy as a function of the extent of conversion
is presented. The method is based on the treatment of experimental data without their transformation so that the resulting
values of activation parameters should not be biased. The method was tested for recovering the activation energies from simulated
data and employed for the treatment of experimental data of the NiS recrystallisation.