Sergey Vyazovkin | University of Alabama at Birmingham (original) (raw)

Uploads

Papers by Sergey Vyazovkin

Thermochimica Acta, 2011

The present recommendations have been developed by the Kinetics Committee of the International Co... more The present recommendations have been developed by the Kinetics Committee of the International Confederation for Thermal Analysis and Calorimetry (ICTAC). The recommendations offer guidance for reliable evaluation of kinetic parameters (the activation energy, the pre-exponential factor, and the reaction model) from the data obtained by means of thermal analysis methods such as thermogravimetry (TGA), differential scanning calorimetry (DSC), and differential thermal analysis (DTA). The recommendations cover the most common kinetic methods, model-free (isoconversional) as well as model-fitting. The focus is on the problems faced by various kinetic methods and on the ways how these problems can be resolved. Recommendations on making reliable kinetic predictions are also provided. The objective of these recommendations is to help a non-expert with efficiently performing analysis and interpreting its results.

Macromolecular Bioscience, 2007

The advanced isoconversional method can be used to determine the effective activation energy of n... more The advanced isoconversional method can be used to determine the effective activation energy of non-isothermal crystallization of the polymer melts. The method has been applied to DSC data on crystallization of poly(ethylene terephthalate) (PET). The resulting activation energy increases with the extent of crystallization from -270 to 20 kJ mol -1 . The variation is interpreted in terms of the Turnbull and Fisher crystallization theory.

Macromolecular Chemistry and Physics, 2000

Macromolecular Chemistry and Physics, 2006

PVC (M w ¼ 80 000), PBMA (M w ¼ 337 000), and PVP (M w ¼ 58 000) were purchased from Aldrich, Ald... more PVC (M w ¼ 80 000), PBMA (M w ¼ 337 000), and PVP (M w ¼ 58 000) were purchased from Aldrich, Aldrich and Summary: Variations of the effective activation energy E of glass transitions have been determined by applying an isoconversional method to DSC data on the glass transition in PVC, PBMA, PVP, and PEN. A variability parameter D E has been introduced to characterize the rate of decrease in E with increasing temperature. By using the present data and our previous results for PS, PET, and B 2 O 3 , it has been found that D E correlates with the values of dynamic fragility, increasing with the latter in approximately exponential fashion.

Thermochimica Acta, 2000

Part A of this series of papers (Parts B to E follow) presents the data and methods used, as well... more Part A of this series of papers (Parts B to E follow) presents the data and methods used, as well as the results obtained by participants in the ICTAC Kinetics Project. The isothermal and non-isothermal data sets provided were based on a hypothetical simulated process as well as on some actual experimental results for the thermal decompositions of ammonium perchlorate and calcium carbonate. The participants applied a variety of computational methods. Isoconversional and multiheating rate methods were particularly successful in correctly describing the multi-step kinetics used in the simulated data. Reasonably consistent kinetic results were obtained for isothermal and non-isothermal data. There is, of course, no`true' answer for the kinetic parameters of the real data, so the ®ndings of the participants are compared. An attempt has been made to forecast the tendencies for the future development of solid state kinetics. #

. A device and software have been developed to simulate differential scanning calorimetry DSC sig... more . A device and software have been developed to simulate differential scanning calorimetry DSC signals according to a given kinetic law. The heat flow is produced by an electric current passing through a resistor. The needed variation in the heat flow is produced by the software-controlled variation in the voltage applied to the resistor. Both peak area and heat flow calibrations have been applied to measure DSC signals. The effect of these calibrations on the activation energy evaluated by an isoconversional method has been examined. Peak area calibration is found to give rise to a systematic deviation in the activation energy that increases with the heating rate. This undesired effect is eliminated when using heat flow calibration. q

Isoconversional Kinetics of Thermally Stimulated Processes, 2015

Handbook of Thermal Analysis and Calorimetry, 2008

Characterization of Materials, 2002

The Journal of Physical Chemistry B, 2004

... Sergey Vyazovkin* and Ion Dranca. Department of Chemistry, University of Alabama at Birmingha... more ... Sergey Vyazovkin* and Ion Dranca. Department of Chemistry, University of Alabama at Birmingham, 901 S. 14th Street, Birmingham, Alabama 35294. J. Phys. Chem. B , 2004, 108 (32), pp 1198111987. DOI: 10.1021/jp048702o. ...