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Investigating the microstructure of soft, microporous matter with synchrotron X-ray tomography

DOI: 10.1016/j.matchar.2021.111408 DOI Help

Authors: Lorenzo Metilli (University of Leeds) , Malte Storm (Diamond Light Source) , Andrew J. Bodey (Diamond Light Source) , Kaz Wanelik (Diamond Light Source) , Arwen I. I. Tyler (University of Leeds) , Aris Lazidis (Nestlé Product Technology Centre) , Stephanie Marty-Terrade (Nestlé Research) , Elena Simone (University of Leeds)
Co-authored by industrial partner: Yes

Type: Journal Paper
Journal: Materials Characterization

State: Published (Approved)
Published: August 2021
Diamond Proposal Number(s): 21081 , 24233

Abstract: Soft porous matter is commonly encountered in artificial tissue applications, pharmaceuticals delivery systems and in cosmetic and food products. These materials are typically opaque and tend to deform under very small levels of shear; this makes the characterization of their microstructure very challenging, particularly in the native state. Air-in-oil systems (oleofoams) are an emerging type of soft material with promising applications in cosmetics and foods, which contain air bubbles stabilized by Pickering fat crystals dispersed in a liquid oil phase. Synchrotron radiation X-ray computed tomography (SR - XCT) is a non-invasive, non-destructive technique increasingly used to investigate multiphasic, porous materials, owing to its high flux which enables sub-micron resolution and significant statistics at rapid acquisition speed. While the penetration of high energy X-rays can provide high resolution images and allows the reconstruction of the 3D structure of samples, the experimental setup and measuring parameters need to be carefully designed to avoid sample deformation or beam damage. In this work, a robust methodology for investigating the 3D microstructure of soft, porous matter was developed. Sample preparation and experimental setup were chosen to allow synchrotron tomographic analysis of soft oleofoams with a low melting point (<30 °C). In particular, the use of cryogenic conditions (plunge-freeze in liquid nitrogen) provided stability against melting during the acquisition. Additionally, an image processing workflow was designed for analysing the 3D microstructure of the samples using ImageJ. Hence, the size and shape distribution of the air phase, as well as the thickness of the continuous gel phase could be determined for samples with significantly different microstructures (fresh vs. heated). Furthermore, the use of time-resolved X-ray radiography (XRR) allowed to study dynamic changes in the microstructure of the samples during thermal destabilization, visualizing bubble coalescence and growth in optically opaque foam samples with a sub-second timescale.

Journal Keywords: X-ray tomography; Oleofoams; Image analysis; Bubble; Soft porous matter

Subject Areas: Materials

Instruments: I13-2-Diamond Manchester Imaging

Added On: 31/08/2021 09:31

Discipline Tags:

Soft condensed matter physics Materials Science

Technical Tags:

Imaging Tomography