H.H. Wills Physics Laboratory, Tyndall Ave., Bristol BS8 1TL, United Kingdom.
Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
J Chem Phys. 2022 Jun 7;156(21):214907. doi: 10.1063/5.0089276.
Colloidal dispersions are prized as model systems to understand the basic properties of materials and are central to a wide range of industries from cosmetics to foods to agrichemicals. Among the key developments in using colloids to address challenges in condensed matter is to resolve the particle coordinates in 3D, allowing a level of analysis usually only possible in computer simulations. However, in amorphous materials, relating mechanical properties to microscopic structure remains problematic. This makes it rather hard to understand, for example, mechanical failure. Here, we address this challenge by studying the contacts and the forces between particles as well as their positions. To do so, we use a colloidal model system (an emulsion) in which the interparticle forces and local stress can be linked to the microscopic structure. We demonstrate the potential of our method to reveal insights into the failure mechanisms of soft amorphous solids by determining local stress in a colloidal gel. In particular, we identify "force chains" of load-bearing droplets and local stress anisotropy and investigate their connection with locally rigid packings of the droplets.
胶态分散体被视为理解材料基本性质的模型体系，在从化妆品到食品再到农用化学品等广泛的行业中都具有核心地位。在利用胶体解决凝聚态物质挑战方面的关键进展之一是解决 3D 中的颗粒坐标，从而实现通常仅在计算机模拟中才有可能的分析水平。然而，在非晶材料中，将力学性能与微观结构联系起来仍然存在问题。这使得理解例如机械失效变得相当困难。在这里，我们通过研究颗粒之间的接触和力以及它们的位置来解决这一挑战。为此，我们使用胶体模型体系（乳液），其中可以将颗粒间的力和局部应力与微观结构联系起来。我们通过确定胶体凝胶中的局部应力，展示了我们的方法揭示软非晶固体失效机制的潜力。特别是，我们确定了承载液滴的“力链”和局部各向异性应力，并研究了它们与液滴局部刚性堆积的关系。
