Department of Material Science, Glass and Ceramics-WW3, University of Erlangen-Nuremberg, Martensstrasse 5, 91058 Erlangen, Germany.
J Chem Phys. 2011 May 28;134(20):204502. doi: 10.1063/1.3593399.
We report on Brillouin and in situ small angle X-ray scattering (SAXS) analyses of topological heterogeneity in compressed sodium borosilicate glasses. SAXS intensity extrapolated to very low angular regimes, I(q = 0), is related to compressibility. From Brillouin scattering and analyses of the elastic properties of the glass, the Landau-Placzek ratio is determined and taken as a direct reflection of the amplitude of frozen-in density fluctuations. It is demonstrated that with increasing fictive pressure, topological (mid- and long-range) homogeneity of the glass increases significantly. Heating and cooling as well as isothermal scans were performed to follow the evolution of density fluctuations upon pressure recovery. For a sample with a fictive pressure p(f) of 470 MPa, complete recovery to p(f) = 0.1 MPa was observed to occur close to the glass transition temperature. The values of fictive and apparent fictive temperature, respectively, as obtained via the intersection method from plots of I(q = 0) vs. temperature were found in good agreement with previous calorimetric analyses. Isothermal scans suggest that mid- and long-range recovery govern macroscopic density relaxation.
我们报告了在压缩的硼硅酸盐钠玻璃中拓扑异质性的布里渊和原位小角 X 射线散射（SAXS）分析。SAXS 强度外推到非常低的角度范围，I(q=0)，与可压缩性有关。从布里渊散射和玻璃弹性性质的分析中，确定了朗道-普拉克泽比，并将其作为冻结密度涨落幅度的直接反映。结果表明，随着虚拟压力的增加，玻璃的拓扑（中程和长程）均匀性显著增加。通过加热和冷却以及等温扫描来跟踪压力恢复时密度涨落的演化。对于具有虚拟压力 p(f)为 470 MPa 的样品，观察到在接近玻璃化转变温度时，完全恢复到 p(f) = 0.1 MPa。通过从 I(q=0)与温度的关系图中的交点方法获得的虚拟和表观虚拟温度的值与先前的量热分析吻合良好。等温扫描表明，中程和长程恢复控制着宏观密度弛豫。
