Journal Article

Measuring nonlinear stresses generated by defects in 3D colloidal crystals

Sethna, James P., Bierbaum, Matthew, Schall, Peter, Cohen, Itai, Lin, Neil Y. C.

2016

Overview

Nonlinear stresses surrounding defect cores in three-dimensional colloidal crystals are experimentally determined at the single-particle level. The mechanical, structural and functional properties of crystals are determined by their defects 1 , 2 , 3 , 4 , and the distribution of stresses surrounding these defects has broad implications for the understanding of transport phenomena. When the defect density rises to levels routinely found in real-world materials, transport is governed by local stresses that are predominantly nonlinear 1 , 5 , 6 , 7 , 8 . Such stress fields however, cannot be measured using conventional bulk and local measurement techniques. Here, we report direct and spatially resolved experimental measurements of the nonlinear stresses surrounding colloidal crystalline defect cores, and show that the stresses at vacancy cores generate attractive interactions between them. We also directly visualize the softening of crystalline regions surrounding dislocation cores, and find that stress fluctuations in quiescent polycrystals are uniformly distributed rather than localized at grain boundaries, as is the case in strained atomic polycrystals. Nonlinear stress measurements have important implications for strain hardening 9 , yield 1 , 5 and fatigue 10 .

• Publisher: Nature Publishing Group UK,Nature Publishing Group,Springer Nature - Nature Publishing Group
• Subject: 639/301/119/1002 / 639/301/923/916 / Biomaterials / Chemistry / Condensed Matter Physics / Cores / Crystal defects / Crystal structure / Crystallinity / Crystals / Defects / Dislocations / Grain boundaries / Lattice vacancies / letter / Materials Science / Measurement techniques / Nanotechnology / Optical and Electronic Materials / Physics / Polycrystals / Strain hardening / Stress concentration / Transport phenomena / Variation