Monash Centre for Electron Microscopy, Monash University, Clayton, 3800, VIC, Australia;
School of Physics and Astronomy, Monash University, Clayton, 3800, VIC, Australia.
Proc Natl Acad Sci U S A. 2017 Sep 26;114(39):10344-10349. doi: 10.1073/pnas.1707198114. Epub 2017 Sep 13.
Local structure and symmetry are keys to understanding how a material is formed and the properties it subsequently exhibits. This applies to both crystals and amorphous and glassy materials. In the case of amorphous materials, strong links between processing and history, structure and properties have yet to be made because measuring amorphous structure remains a significant challenge. Here, we demonstrate a method to quantify proportions of the bond-orientational order of nearest neighbor clusters [Steinhardt, et al. (1983) 28:784-805] in colloidal packings by statistically analyzing the angular correlations in an ensemble of scanning transmission microbeam small-angle X-ray scattering (SAXS) patterns. We show that local order can be modulated by tuning the potential between monodisperse, spherical colloidal silica particles using salt and surfactant additives and that more pronounced order is obtained by centrifugation than sedimentation. The order in the centrifuged glasses reflects the ground state order in the dispersion at lower packing fractions. This diffraction-based method can be applied to amorphous systems across decades in length scale to connect structure to behavior in disordered systems with a range of particle interactions.
局部结构和对称性是理解材料形成方式和随后表现出的性质的关键。这既适用于晶体，也适用于非晶态和玻璃态材料。在非晶态材料的情况下，由于测量非晶态结构仍然是一个重大挑战，因此尚未建立加工与历史、结构和性能之间的紧密联系。在这里，我们展示了一种通过统计分析扫描透射微束小角 X 射线散射（SAXS）图案的整体角相关性来量化胶体堆积中最近邻团簇的键取向有序比例的方法[Steinhardt 等人，（1983）28：784-805]。我们表明，通过使用盐和表面活性剂添加剂来调节单分散、球形二氧化硅胶体颗粒之间的势能，可以调节局部有序性，并且离心比沉降可以获得更明显的有序性。离心玻璃中的有序性反映了较低堆积分数下分散体中的基态有序性。这种基于衍射的方法可以应用于非晶态系统，跨越几十年的长度尺度，将无序系统中的结构与行为联系起来，其中涉及各种粒子相互作用。
