X-ray nanotomography of dry colloidal packings

Yeseul Kim,Sangsul Lee,Byung Mook Weon,Jun Lim

doi:10.1038/s41598-020-74315-2

Yeseul Kim, Sangsul Lee + Show 2 more

Open Access

https://doi.org/10.1038/s41598-020-74315-2

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Abstract

Random packings are crucial in understanding arrangement and geometry of particles. Random packings of dry small particles may be subject to adhesion or friction, as expected theoretically and numerically. We explore experimentally random packings of dry colloids with X-ray nanotomography that directly provides three-dimensional structural and geometric information of dry colloidal packings. We find that dry colloidal packings, as characterized by contact number and packing density, are quite consistent with adhesive loose packings that significantly deviate from random loose packings for hard spheres. This study may offer direct evidence for adhesive loose packings comprising dry small particles, as proven by X-ray nanotomography.

Highlights

Random packings are crucial in understanding arrangement and geometry of particles
The random packing consisting of the 0.5-μm-diameter colloids were prepared to have the volume fraction φ = 0.499, the global contact number Z = 4.494, and the total number of particles N = 1145, as confirmed by X-ray nanotomography
Following the algorithm successfully used for identifying s pheres[33], we binarized the entire colloids except the two layers of colloidal particles from the boundaries, measured the particle diameters, and identified the positions from the centers of the particles

Summary

Introduction

Random packings are crucial in understanding arrangement and geometry of particles. Random packings of dry small particles may be subject to adhesion or friction, as expected theoretically and numerically. This study may offer direct evidence for adhesive loose packings comprising dry small particles, as proven by X-ray nanotomography. For dry small particles (or dry colloids), without surrounding liquid media, their random packings are expected to deviate from hard-sphere random packings, as suggested n umerically[17,18,19,20,21,22,23,24]. To identify random packings of dry colloids, we adopted X-ray imaging techniques because they are powerful to characterize colloidal structures thanks to high-resolution and high-penetration capabilities of X-ray photons. Using X-ray nanotomographic techniques, we are able to identify 3D structures of random packings from dry colloids and offer direct evidence for the ALP random structures of dry colloids. We quantify contact number and volume fraction of dry colloids with X-ray nanotomographic techniques

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