Why fumed and precipitated silica have different mechanical behavior: Contribution of discrete element simulations

Guesnet, Étienne; Benane, Belynda; Jauffrès, David; Martín, Christophe; Baeza, Guilhem P.; Foray, Geneviève; Meille, Sylvain; Olagnon, C.; Yrieix, Bernard

doi:10.1016/j.jnoncrysol.2019.119646

Cited by 10 publications

(7 citation statements)

References 41 publications

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“…The challenge here, however, is the production of the cores, since the mechanical stability of the compacts during production can only be guaranteed to a limited extent. 40 Possibly contrary to the intuitive assumption, a particularly large spread between minimum and maximum values is not obtained for switchable VIPs at high porosities, but rather at low ones. Although the switchable fraction, namely the gas phase, is volumetrically larger at higher porosities, the number of particles and thus the number of contact points is smaller.…”

Section: Core Materials For Different Applicationsmentioning

confidence: 77%

Silica‐based core materials for thermal superinsulations in various applications

Sonnick

Nirschl

Rädle

2022

Intl J of Energy Research

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Summary Vacuum insulation panels (VIP) are usually manufactured using standardized manufacturing processes based on empirical values and in most cases with any fumed silica as the main component of the core material. However, not all applications have the same requirements in terms of thermal conductivity and service life. Therefore, it is useful to adapt the kind of core materials and their product specifications, such as particle size and porosity, to the different applications. Furthermore, in some applications cheaper core materials, like precipitated silica, would be a reasonable alternative. To replace the time‐consuming series of measurements for this purpose, this work offers comprehensive parameter studies to determine the optimum product properties of precipitated silica, fumed silica, silica gel, and glass spheres for use in the building sector, in transport boxes, as a superinsulation at atmospheric pressure, and as a switchable VIP. As a result, not only the preferred materials but also their porosities and particle sizes are presented. For atmospheric pressure and construction applications, fumed silica has to be preferred. For the transport sector and switchable VIPs as well as certain special applications, precipitated silica and silica gel may well be reasonable alternatives.

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Section: Core Materials For Different Applicationsmentioning

confidence: 77%

Silica‐based core materials for thermal superinsulations in various applications

Sonnick

Nirschl

Rädle

2022

Intl J of Energy Research

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“…The volume shrinkage measurements on drying are 0.05 and 0.09 for the T and X binders, respectively. Previous studies reached those densities with aerogel granules using a permanent uniaxial pressure [ 42 , 43 ], and proved their thermal efficiency.…”

Section: Resultsmentioning

confidence: 93%

X-ray Tomography Coupled with Finite Elements, A Fast Method to Design Aerogel Composites and Prove Their Superinsulation Experimentally

Foray

Randrianalisoa

Adrien

et al. 2022

Gels

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Composite aerogels can include fibers, opacifiers and binders but are rarely designed and optimized to achieve the best thermal/mechanical efficiency. This paper proposes a three-dimensional X-ray tomography-based method for designing composites. Two types of models are considered: classical and inexpensive homogenization models and more refined finite element models. XrFE is based on the material’s real three-dimensional microstructure and/or its twin numerical microstructure, and calculates the effective conductivity of the material. First, the three-dimensional sample is meshed and labeled. Then, a finite element method is used to calculate the heat flow in the samples. The entire three-dimensional microstructure of a real or fictitious sample is thus associated with a heat flow and an effective conductivity. Parametric studies were performed to understand the relationship between microstructure and thermal efficiency. They highlighted how quickly a low volume fraction addition can improve or ruin thermal conductivity. A reduced set of three formulations was developed and fully characterized. The mechanical behavior was higher than 50 KPa, with thermal efficiencies ranging from 14 to 15 mW·m·K−1.

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“…It was originally designed for the study of granular materials [37] but is also adapted for continuous materials [23,38,39,40,24,41]. Using DEM to study low-stiffness and brittle materials like silica aerogels was successfully carried out in several other studies [26,27] with discrete elements representing primary silica particles, i.e. the silica particles forming the nanoscale pearl-necklace network of aerogels.…”

Section: Discrete Element Methods Modelmentioning

confidence: 99%

“…The mechanical tests were paired with density measurements and X-ray tomography in order to link the measured properties to the possible density variation and the presence of process induced cracks. The Discrete Element Method (DEM), particularly wellsuited to simulate damage and crack propagation [23,24,25], has already been applied to silica aerogels [26,27]. Here, it is used to simulate particle compression and contribute to the analysis of experimental results.…”

Section: Introductionmentioning

confidence: 99%

Mechanical properties of milimetric silica aerogel particles produced through evaporative drying: A coupled experimental and discrete element approach

Hamelin

Jauffrès

Martín

et al. 2021

Journal of Non-Crystalline Solids

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Why fumed and precipitated silica have different mechanical behavior: Contribution of discrete element simulations

Cited by 10 publications

References 41 publications

Silica‐based core materials for thermal superinsulations in various applications

Silica‐based core materials for thermal superinsulations in various applications

X-ray Tomography Coupled with Finite Elements, A Fast Method to Design Aerogel Composites and Prove Their Superinsulation Experimentally

Mechanical properties of milimetric silica aerogel particles produced through evaporative drying: A coupled experimental and discrete element approach

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