Compression of aerogels

Scherer, George W.; Smith, Douglas M.; Qiu, Xiaomei; Anderson, Jeffrey C.

doi:10.1016/0022-3093(95)00074-7

Cited by 174 publications

(115 citation statements)

References 5 publications

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“…Since no mercury intrusion occurs, the compression modulus (K) can be related to the volume density (φ) according to Eq. 4., following to Scherer's methodology [33]. The volume density φ at the pressure of mercury P, defined as the ratio between the volume of the skeleton and the total volume of the sample, can be expressed by Eq.…”

Section: Mechanical Propertiesmentioning

confidence: 99%

“…One symbol was added as label on each data set Combination of the results obtained from the mechanical compression tests, on the dried samples, and the mercury porosimetry measurements allows obtaining the Poisson ratio, ν, according to Eq. 6 [33]. Last column of Table 2 shows the values of the Poisson ratio corresponding to the dried state of the samples, i.e.…”

Section: Mechanical Propertiesmentioning

confidence: 99%

“…For this material, the pore size distribution cannot be obtained in a straightforward manner due to the collapse of the sample under mercury pressure [32]. Nevertheless the data allow to determine the compression modulus of the network according to Scherer's methodology [33]. This parameter has been shown to be related to the microstructure [28].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Evolution of mechanical properties and final textural properties of resorcinol–formaldehyde xerogels during ambient air drying

Léonard

Blacher

Crine

et al. 2008

Journal of Non-Crystalline Solids

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Porous carbon xerogels can be obtained by convective drying of resorcinol (R)-formaldehyde (F) hydrogels, followed by pyrolysis. Drying conditions have to be carefully controlled when crack-free monoliths with well-defined shape and size are required. The knowledge of the mechanical properties of the RF xerogels and their evolution with water content is essential to model their thermo-hygro-mechanical behaviour during convective drying and avoid mechanical stresses leading to deformation and cracking of the sample. The shrinkage behaviour and the mechanical properties of RF xerogels obtained with R/C ratio ranging from 300 to 1500 were investigated. R/C greatly influences the shrinkage and mechanical properties of the wet gel, on the one hand, and the mechanical and textural properties of the dried gel, on the other hand. The smaller the R/C, the higher the shrinkage, the stiffening, and the viscoelastic character of the xerogels. Water content has an influence on both the stiffness of the gels and the viscoelastic response. Generally, samples lose their mechanical viscous character and become more rigid when they are dried. Finally, mercury porosimetry measurements showed that the gels exhibit a marked lowering of 2 their stiffness upon compression, interpreted as a result of the heterogeneity of the microstructure.

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Section: Mechanical Propertiesmentioning

confidence: 99%

Section: Mechanical Propertiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Evolution of mechanical properties and final textural properties of resorcinol–formaldehyde xerogels during ambient air drying

Léonard

Blacher

Crine

et al. 2008

Journal of Non-Crystalline Solids

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show abstract

“…However, the samples must be strong enough to withstand high mercury pressure without deforming. When it is applied to fragile materials, such as those synthesized by sol-gel process, the samples are crushed by mercury rather than intruded [3,4]. As a consequence, the information obtained by this technique is purely mechanical.…”

Section: Introductionmentioning

confidence: 99%

Compressing some sol-gel materials reduces their stiffness: a textural analysis

Gommes

Job

Blacher

et al. 2007

Studies in Surface Science and Catalysis

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The mechanical behaviour of two series of silica and of resorcinol xerogels is analyzed by mercury porosimetry. The data are expressed as pressure-density curves, which enables textural information to be obtained. In particular, it is shown that some of the analyzed samples exhibit a marked lowering of their mechanical stiffness upon compression. This observation is analyzed in terms of the collapse of the sample's porosity and of the heterogeneity of the microstructure.

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“…Therefore nitrogen cannot penetrate into the compressed pores leading to lower specific surface areas and pore volumes. [39][40][41] An indicator for this phenomenon is the open hysteresis loops for samples with higher loadings of functional organic moieties (over 10 molar%). If the slit-like pores are compressed during the course of the nitrogen sorption measurement, nitrogen cannot escape from the pores.…”

Section: Influence Of Chemical Functionalization On Micro- Macrostrumentioning

confidence: 99%

Flexible organofunctional aerogels

et al. 2017

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Flexible inorganic-organic silica aerogels based on methyltrimethoxysilane (MTMS, CH 3 Si(OCH 3 ) 3 ) can overcome the drawbacks of conventional silica aerogels by introducing high mechanical strength, elastic recovery and hydrophobicity to monolithic materials. In this work, MTMS is co-condensed with organofunctional alkoxysilanes RSi(OMe) 3 (R = vinyl, chloropropyl, mercaptopropyl, methacryloxypropyl, etc.) yielding aerogels that are not only flexible but also contain reactive functional groups. Sol-gel parameters, such as the MTMS/RSi(OMe) 3 ratio, have been systematically investigated in terms of gelation behavior, complete/incomplete incorporation of the functional organic groups (confirmed by FTIR-ATR and Raman spectroscopy) and flexibility of the resulting gel. Sterically more demanding functional moieties lead to macroscopic phase separation; however, this problem was overcome by the employment of surfactants. Functional aerogels dried by supercritical extraction with carbon dioxide showed promising results in uniaxial compression tests and had an elastic recovery up to 60%. Furthermore, the accessibility of the functional groups was demonstrated by simple reactions, e.g. conversion of the chloro into azido groups via a nucleophilic substitution reaction with NaN 3 followed by click reactions.

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Compression of aerogels

Cited by 174 publications

References 5 publications

Evolution of mechanical properties and final textural properties of resorcinol–formaldehyde xerogels during ambient air drying

Evolution of mechanical properties and final textural properties of resorcinol–formaldehyde xerogels during ambient air drying

Compressing some sol-gel materials reduces their stiffness: a textural analysis

Flexible organofunctional aerogels

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