Visualizing the Toughening Mechanism of Nanofiller with 3D X-ray Nano-CT: Stress-Induced Phase Separation of Silica Nanofiller and Silicone Polymer Double Networks

Abstract

Adding silica nanofiller in silicone rubber can toughen the matrix 3 orders in terms of fracture energy, which is far larger than most other nanofiller–rubber systems. To unveil the astonishing toughening mechanism, we employ in situ synchrotron radiation X-ray nanocomputed tomography (Nano-CT) technique with high spatial resolution (64 nm) to study the structural evolution of silica nanofiller in silicone rubber matrix at different strains. The imaging results show that silica nanofiller forms three-dimensional connected network, which couples with silicone chain network to construct a double-network structure. Stress-induced phase separation between silica nanofiller and silicone polymer chain networks is observed during tensile deformation. Unexpectedly, though the spatial position and morphology of nanofiller network changes greatly at large strains, the connectivity of nanofiller network shows negligible reduction. This indicates that nanofiller network undergoes destruction and reconstruction simultaneously, during which silica nanofiller serves as reversible high functionality cross-linker. The reversible bonding between silica nanofiller and silicone rubber or between nanofiller particles can dissipate mechanical energy effectively, which may account for the 3 orders enhancement of toughness.

Hierarchical Interface Engineering for Advanced Nanocellulosic Hybrid Aerogels with High Compressibility and Multifunctionality

“…[ 21b ] Cross sections (Figure S9, Supporting Information) of the BC–PMSQ aerogel created by X‐ray are used to rebuild a 3D virtual model in a nondestructive way (Figure 2g). [ 22 ] Owing to the sensitivity of X‐ray to the density of materials, the macropores and frameworks of the aerogel sample are separated, where the constituent of pores is made transparent while BC–PMSQ nanocomposite framework is colored with blue (Figure 2h). After the extraction of the pore phase, an axially aligned cellular framework is presented in Figure 2i.…”

“…After analysis of the tomograms using Avizo software, the spatial distribution of mass density of fibrous network can be extracted. [ 22a ] Figure 3d‐(iii) gives a representative 3D imaging of the filamentous composite, where the components with higher mass density is made yellow and the remaining counterpart is colored with red. The observed high mass density at the crossjunction indicates that the composite components of BC nanofibers and PMSQ are accumulated in this area.…”

Correlative Laboratory Nano‐CT and 360° Electron Tomography of Macropore Structures in Hierarchical Zeolites

“…Lab Nano‐CT reaches almost the same spatial resolution as synchrotron Nano‐CT. However, the latter technique enables shorter acquisition times, which are beneficial for in situ and operando experiments like in situ X‐ray ptychography, [ 5d,40 ] operando Micro‐CT of Li‐ion battery materials, [ 16b,41 ] interrupted in situ Nano‐CT of mechanical testing, [ 42 ] in situ and operando Nano‐CT of fuel cell electrodes [ 43 ] or environmental in situ Nano‐CT of a fuel cell. [ 44 ] Similar experiments can also be realized on lab Nano‐CT instruments, albeit at lower temporal resolution or by interrupted in situ experiments, where before and after an experiment, e.g., mechanical testing [ 45 ] or in situ heating, [ 46 ] Nano‐CT datasets are collected.…”

Nanoparticle self-assembly: from interactions in suspension to polymer nanocomposites

“…When suspensions are dried, capillary forces may affect the dispersion, and induce additional aggregation, which was not present in the original suspension. Only a few tomographic approaches with electrons 15 or X-rays 16 have been developed to avoid the projection problem into two dimensions. In particular, Dalmas et al 17 proposed an optimised procedure for the segmentation of TEM tomograms in order to isolate nanoparticles.…”