Advanced three dimensional characterization of silica-based ultraporous materials

Abstract

conditions. Such a low value requires reducing air molecule mobility in highly porous materials, and silica-based superinsulation materials (SIM) made of packed nanostructured silica or aerogel are good candidates for this purpose. However, the native nanostructure of silica has never been imaged or characterized up to now, making SIM optimization quite difficult. In this paper, three nanostructured commercial silica samples prepared by different synthesis methods were analysed and quantified using advanced electron tomography, N 2 physisorption, mercury porosimetry and helium pycnometry. It was demonstrated that 3D images yield a much finer description of the microstructure (particle, aggregate and pore) compared to global measurements. For the samples studied, silica particle size is dependent on the synthesis method, increasing with pore diameter size. The smallest silica particles were obtained by the sol-gel method which also provides the smallest pore diameters, the smallest and rather spherical aggregates, and the lowest thermal conductivity. The pyrogenic and precipitated samples studied presented bigger silica particles with higher pore diameters and thus higher thermal conductivities. 3Dimage driven characterization opens up new synthesis opportunities for silica.

Nanocompression of secondary particles of silica aerogel

“…The resulting density and characteristic porosity size are 250 kg.m −3 (equivalent to a 90% porosity structure) and 10 nm, respectively. This density is particularly relevant for comparison with experiments as its pore size distribution [13] matches electron tomography observations [1]. More details on the bulk silica nanoporous structure generation can be found in [13].…”

“…Recently, the use of a van Beest, Kramer and van Santen (BKS) pair potential optimized for larger timescale simulations (without long-range interactions) and transferable to surface properties [12], opened the possibility to explore nanoporous structures with surface/volume ratio that are very close to experimental silica aerogels [13]. Large volumes (up to 100 3 nm 3 ) were modeled with pores that match satisfactorily experimental observations [1]. The elasticity and strength of these volumes have shown a marked asymmetry in tension-compression that originates from the substantial preexisting compressive capillary-driven stress that silica ligaments are subjected to [13].…”

The effect of viscosity and surface tension on inkjet printed picoliter dots

“…The mean pore diameter and the porosity were evaluated with a mercury intrusion porosimetry, a common technique to characterize microscale pore size distributions. [53][54][55] We used an Autopore IV 9500 instrument from Micromeritics Instrument Corp. 56 The roughness was measured according to Bendtsen Fig. 3 Measurement principle of the print through test.…”

Sol‐Gel and Porous Glass‐Based Silica Monoliths with Hierarchical Pore Structure for Solid‐Liquid Catalysis

“…For example, the location, size, distribution, and loading of metal nanoparticles in mesoporous solids has been determined, but also the support structures themselves have been investigated. On the other hand, studies that report quantitative morphological data of disordered mesopore networks for silica-based materials are still scarce [95,114,115]. Figure 16.…”