Cang Yu, Liu Bohai, Das Sudatta, Xu Xiangfan, Xie Jingli, Deng Xu, Fytas George
School of Aerospace Engineering and Applied Mechanics, Tongji University, 100 Zhangwu Road, 200092, Shanghai, China and Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany.
Center for Phononics and Thermal Energy Science, School of Physical Science and Engineering, Tongji University, Shanghai, 200092, China.
Phys Chem Chem Phys. 2021 Feb 19;23(6):3707-3715. doi: 10.1039/d0cp05377e.
Granular materials are often encountered in science and engineering disciplines, in which controlling the particle contacts is one of the critical issues for the design, engineering, and utilization of their desired properties. The achievable rapid fabrication of nanoparticles with tunable physical and chemical properties facilitates tailoring the macroscopic properties of particle assemblies through contacts at the nanoscale. Models have been developed to predict the mechanical properties of macroscopic granular materials; however, their predicted power in the case of nanoparticle assemblies is still uncertain. Here, we investigate the influence of nanocontacts on the elasticity and thermal conductivity of a granular fiber comprised of close-packed silica nanoparticles. A complete elastic moduli characterization was realized by non-contact and non-destructive Brillouin light spectroscopy, which also allowed resolving the stiffness of the constituent particles in situ. In the framework of effective medium models, the strong enhancement of the elastic moduli is attributed to the formation of adhesive nanocontacts with physical and/or chemical bondings. The nanoparticle contacts are also responsible for the increase in the fiber thermal conductivity that emphasizes the role of interface thermal resistance, which tends to be ignored in most porosity models. This insight into the fundamental understanding of structure-property relationships advances knowledge on the manipulation of granular systems at the nanoscale.
颗粒材料在科学和工程学科中经常遇到，其中控制颗粒接触是设计、工程化以及利用其所需特性的关键问题之一。可实现的具有可调物理和化学性质的纳米颗粒的快速制造，有助于通过纳米级的接触来定制颗粒组件的宏观性质。已经开发出模型来预测宏观颗粒材料的力学性能；然而，它们在纳米颗粒组件情况下的预测能力仍然不确定。在这里，我们研究了纳米接触对由紧密堆积的二氧化硅纳米颗粒组成的颗粒纤维的弹性和热导率的影响。通过非接触和非破坏性的布里渊光谱实现了完整的弹性模量表征，这也使得能够原位解析组成颗粒的刚度。在有效介质模型的框架内，弹性模量的强烈增强归因于具有物理和/或化学键合的粘性纳米接触的形成。纳米颗粒接触也是纤维热导率增加的原因，这突出了界面热阻的作用，而在大多数孔隙率模型中往往忽略了这一点。这种对结构-性质关系的基本理解的深入见解推进了对纳米尺度颗粒系统操纵的认识。
