Nonlinear thermal response at the glass transition
Nonlinear thermal response at the glass transition
复制标题
玻璃化转变的非线性热响应
DOI：
10.1063/1.479545
复制
发表时间：
1999
影响因子：
4.4
通讯作者：
A. Hensel
中科院分区：
文献类型：
--
作者：
C. Schick;M. Merzlyakov;A. Hensel
在线性响应中，复热容等于熵柔度除以温度。涨落耗散定理给出了熵涨落与相关函数（时域）或谱密度（频域）的关系。玻璃化转变时频率相关热容的另一种正式描述是基于结构恢复的Tool-Narayanaswamy-Moynihan方法。在小温度扰动的极限下，两种模型都能描述测量到的复热容。当非线性首次出现时，我们测量了中温振幅下的响应，并将结果与两种方法的预期行为进行了比较。我们研究了0.1 - 15k温度幅值范围内的高次谐波。在聚醋酸乙烯酯（PVAc）的玻璃化转变中，我们在温度振幅为1k时观察到1%的高次谐波。偶次谐波可以用一次谐波（热）的温度依赖性来定量描述。
In linear response, the complex heat capacity is equal to the entropy compliance divided by temperature. The fluctuation dissipation theorem gives a relation to the correlation function (time domain) or spectral density (frequency domain) of entropy fluctuations. Another formal description of frequency dependent heat capacity at the glass transition is based on the Tool–Narayanaswamy–Moynihan approach of structural recovery. In the limit of small temperature perturbations both models are able to describe measured complex heat capacity. We have measured the response at medium temperature amplitudes, when first nonlinearities appear, and have compared the results with the behavior expected from both approaches. We have studied higher harmonics in the temperature amplitude range 0.1–15 K. At the glass transition of poly(vinyl acetate) (PVAc) we observe 1% of higher harmonics at temperature amplitudes of 1 K. Even harmonics can be described quantitatively by the temperature dependence of first harmonic (heat ...