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摘要
By determining the fictive temperature, T(f), in two ways from the same C(p) data, we investigate whether the residual entropy, S(res), of a glass could be an artifact of using the C(p) d ln(T) integral in the glass-liquid temperature range. Although the integral gives only the upper and lower limits of the real entropy change, it is still useful and is distinguished as Delta sigma. We determine T(f)(sigma) from Delta sigma and the usual T(f)(H) from the C(p) dT integral for two metal alloy glasses, a basalt composition glass and a spray-quenched propylene glycol glass from the available data, and find that T(f)(sigma) is about the same as T(f)(H) within errors. To substantiate it, we report a differential scanning calorimetry study performed during cooling of the Mg(65)Cu(25)Tb(10) and Pd(40)Ni(10)Cu(30)P(20) melts and on heating their glassy states at the same rates. In addition, we simulate C(p)-T plots from a known model for nonexponential, nonlinear relaxation and analyze the data. The quantity Delta sigma on cooling the liquid and heating the glass differs negligibly; that is, net change in a temperature cycle between glass and its melt is close to zero, a characteristic of a nearly reversible change. We conclude that spontaneous enthalpy release has little effect on the entropy change determined from the C(p) d ln(T) integral and, contrary to recent suggestions, Sres is real.
- 出版日期2010-7-29
