Department of Materials Science & Engineering, University of California at Davis, Davis, California 95616, United States.
Science & Technology Division, Corning Inc., Corning, New York 14831, United States.
J Phys Chem B. 2021 Mar 18;125(10):2754-2760. doi: 10.1021/acs.jpcb.0c11278. Epub 2021 Mar 5.
The kinetic and calorimetric fragility indices of binary As-Se and Se-Te chalcogenide liquids with a wide range of fragility are determined using a combination of parallel plate rheometry, beam bending viscometry, and conventional differential scanning calorimetry (DSC). It is shown that both sets of measurements lead to consistent values only if the validity of the assumptions often implicit in the methodology for the estimation of are considered. These assumptions are (i) the glass transition temperature corresponds to a viscosity of ∼10 Pa s and (ii) enthalpy and shear relaxation time scales τ and τ are comparable near . Both assumptions are shown to be untenable for highly fragile liquids, for which modulated DSC studies demonstrate that τ ≫ τ near . In these cases, the above-mentioned assumptions are shown to lead to consistently higher values for the kinetic fragility compared to its calorimetric counterpart.
使用平行板流变仪、梁弯曲粘度计和传统差示扫描量热法（DSC）组合，测定了具有较宽脆性范围的二元 As-Se 和 Se-Te 硫属玻璃液体的动力学和量热学脆性指数。结果表明，只有在考虑到用于估计的方法中经常隐含的假设的有效性时，这两组测量才会得出一致的值。这些假设是：(i)玻璃化转变温度对应于约 10 Pa s 的粘度；(ii)焓和剪切松弛时间尺度 τ 和 τ在附近具有可比性。对于高度脆弱的液体，这两个假设都被证明是站不住脚的，因为调制 DSC 研究表明，在附近，τ ≫ τ。在这些情况下，与量热法相比，动力学脆性的上述假设导致其值始终更高。
