Specific heat relaxation of an alcohol and implications for dielectric comparison
Anno: 2009
Autori: Tombari, E., Ferrari C., Salvetti G., Johari G.P.
Affiliazione autori: Istituto per i Processi Chimico-Fisici, CNR, Via G. Moruzzi 1, 56124 Pisa, Italy; Department of Materials Science and Engineering, McMaster University, Hamilton, ON L8S 4L7, Canada
Abstract: The dynamic and the apparent specific heats of 5-methyl-2-hexanol were measured in its vitrification temperature range during its cooling and then heating at the same and exceptionally slow rates of 12 K/h and 60 K/h. The relaxation time determined from dynamic measurements is 48 s at 149.8 K. The relaxation time estimated from the onset of the apparent C(p)-endotherm measured on heating is found to be inconsistent with that determined from dynamic C(p) measurements. The fitting of a nonexponential nonlinear relaxation model to the C(p,app) data shows that beta varies slightly with the heating rate, and this is attributed to contributions to temperature-dependent energy from change in the hydrogen-bond population. The unrelaxed C(p) of the ultraviscous liquid is closer to that of its glassy state, thus showing that the vibrational part of C(p) does not increase in a sigmoid-shape manner when the glass structure kinetically unfreezes on heating. The results have implications for use of calorimetry in inferring the dielectric relaxation mechanism.
Giornale/Rivista: JOURNAL OF CHEMICAL PHYSICS
Volume: 130 (12) Da Pagina: 124505 A: 124505
Parole chiavi: dielectric relaxation; hydrogen bonds; specific heat; vitrification; DOI: 10.1063/1.3100188Citazioni: 8dati da “WEB OF SCIENCE” (of Thomson Reuters) aggiornati al: 2024-04-21Riferimenti tratti da Isi Web of Knowledge: (solo abbonati) Link per visualizzare la scheda su IsiWeb: Clicca quiLink per visualizzare la citazioni su IsiWeb: Clicca qui