Mechanical properties of silica aerogels

Parmenter, Kelly E.; Milstein, Frederick

doi:10.1016/s0022-3093(97)00430-4

Cited by 242 publications

(140 citation statements)

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“…One of the ways for improving this disadvantage is an application of dispersed reinforcement, such as short fibres or directional reinforcement in the form of the mats [1,2]. In the literature, little attention is paid to the application of short carbon fibres as silica aerogel reinforcement.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and characterisation of silica aerogel/carbon microfibers nanocomposites dried in supercritical and ambient pressure conditions

Ślosarczyk

Barełkowski

Niemier

et al. 2015

J Sol-Gel Sci Technol

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Experimental results on the physical and chemical properties of silica aerogel and its composites with carbon microfibers are reported. The aerogels and silica aerogel/carbon microfibers nanocomposites were prepared via the sol-gel process of organosilicon compound followed by successive washing and drying in different conditions. Part of nanomaterials was surface modified in TMCS/n-hexane mixture in 50°C and dried in ambient pressure. Simultaneously, the supercritical drying of aerogels and its nanocomposites in CO 2 atmosphere was carried out. The carbon microfibers before usage in silica aerogel composites were chemically treated in nitric acid. The physical properties of silica aerogels were studied by measuring the bulk density, volume shrinkage, porosity, pore volume and thermal conductivity. In the case of pure aerogels dried via supercritical conditions, the structure presented much less contraction during drying and was more resistant to higher temperature. However, the properties of silica aerogels composites with carbon microfibers drying in ambient pressure were better than corresponding composites subjected to supercritical drying. It was shown that simultaneous oxidation of carbon fibres and chemical modification of silica aerogel in TMCS/n-hexane mixture contributed to the stable mesoporous structure of composite with very good physical properties, especially lower shrinkage.& Agnieszka Ś losarczyk agnieszka.slosarczyk@put.poznan.pl

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Section: Introductionmentioning

confidence: 99%

Synthesis and characterisation of silica aerogel/carbon microfibers nanocomposites dried in supercritical and ambient pressure conditions

Ślosarczyk

Barełkowski

Niemier

et al. 2015

J Sol-Gel Sci Technol

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“…Presentan diversas aplicaciones, de las que se pueden destacar su uso como aislante térmico y acústico (3), como detector de micrometeoritos (4) y también de partículas subatómicas como detectores Cherenkov (5). Sin embargo, sus principales limitaciones son su extrema fragilidad y su alta higroscopicidad (6).…”

Section: Introductionunclassified

Propiedades mecánicas de aerogeles híbridos de sílice

Piñero¹,

Fox²,

Flórez³

et al. 2005

Bol. Soc. Esp. Ceram. Vidr.

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Se han obtenido aerogeles híbridos de sílice orgánico-inorgánico por aplicación de ultrasonidos de alta potencia en los precursores líquidos y posterior secado del gel húmedo en condiciones supercríticas en etanol. Las cadenas orgánicas no se degradan térmicamente y aceleran el proceso de contracción de la red por activación térmica. Los ultrasonidos inducen un entrecruzamiento de cadenas orgánicas que unen los cúmulos de sílice porosa y evitan su ciclidación. Los ensayos de ruptura en compresión uniaxial indicaron un aumento del módulo de ruptura, pasando de 8 MPa para el aerogel de sílice pura hasta 24 MPa para un aerogel de 50% en peso de contenido de polímero. Se observa asimismo una disminución continua en el módulo de Young con el contenido de polímero (de 100 a 56 MPa). Estos aerogeles híbridos se comportan como elastómeros con deformaciones de hasta el 50%, mostrando una disminución del módulo de relajación viscoelástica.Palabras clave: Aerogel de sílice, elastómeros, módulo de ruptura, compresión y relajación viscoelástica. Mechanical properties of silica hybrid aerogelsHybrids silica aerogels have been obtained by means the high power ultrasounds application in the precursor liquid and the drying of the wet gel under the supercritical condition of ethanol. The organic chains don't degrade thermally and accelerate the network shrinkage process by thermal activation. The ultrasounds induce an organic chain crosslinking bonding to the porous silica clusters and avoid its cyclidation. The failure tests by uniaxial compression show an increase of the rupture modulus, passing from 8 MPa for a pure silica aerogel to 24 MPa for an aerogel with a 50 weight % of polymer content. It is also noted a continuous decrease of the Young's modulus with the polymer content (from 100 to 56 MPa). These hybrid aerogels behave as elastomers with up to a 50% strain, showing a decrease in the relaxation viscoelastic modulus.Keywords: silica aerogel, elastomers, failure, compression and relaxation viscoelastic modulus. INTRODUCCIÓNLos aerogeles de sílice son materiales transparentes y químicamente inertes, su densidad puede variar desde 0.003 g cm -3 hasta 0.9 g cm -3, con una alta porosidad de aproximadamente 90% que se modula en el intervalo de poros de tamaño nanométrico, con superficies específicas entre 600 y 1000 m 2 g -1 y que mantiene una composición idéntica al vidrio de sílice pura (1, 2). A pesar de ser un material tan ligero, el entramado polimérico de sílice mantiene unas buenas propiedades mecánicas. Presentan diversas aplicaciones, de las que se pueden destacar su uso como aislante térmico y acústico (3), como detector de micrometeoritos (4) y también de partículas subatómicas como detectores Cherenkov (5). Sin embargo, sus principales limitaciones son su extrema fragilidad y su alta higroscopicidad (6).Las propuestas para superar tales inconvenientes implican la introducción de polímeros orgánicos hidrófobos que además modifican la red polimérica de la sílice inorgánica (7), tratando al mismo tiempo de aumentar ...

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“…One approach is through incorporating silica fibres into the aerogels. Tests have indicated that when 10% by weight of these fibres are introduced, the elastic modulus and strength are increased by 85% and [89]. In addition, the compressive modulus and tensile strength of aerogels can be improved by three and five times correspondingly, if 5% by weight of carbon nanofibres are implemented into the lattice structure [90].…”

Section: Mechanical Propertiesmentioning

confidence: 99%

Flexible and Transparent Silica Aerogels: An Overview

Parale¹,

Lee²,

Park³

2017

J. Korean Ceram. Soc

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Aerogels are highly porous structures prepared via a sol-gel process and supercritical drying technology. Among the classes of aerogels, silica aerogel exhibits the most remarkable physical properties, possessing lower density, thermal conductivity, refractive index, and dielectric constant than any solids. Its acoustical property is such that it can absorb the sound waves reducing speed to 100 m/s compared to 332 m/s for air. However, when it comes to commercialization, the result is not as expected. It seems that mass production, particularly in the aerospace industry, has dawdled behind. This paper highlights the evolution of aerogels in general and discusses the functions and significances of silica aerogel in previous astronautical applications. Future outer-space applications have been proposed as per the current research trend. Finally, the implementation of conventional silica aerogel in aeronautics is argued with an alternative known as Maerogel.

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Mechanical properties of silica aerogels

Cited by 242 publications

References 7 publications

Synthesis and characterisation of silica aerogel/carbon microfibers nanocomposites dried in supercritical and ambient pressure conditions

Synthesis and characterisation of silica aerogel/carbon microfibers nanocomposites dried in supercritical and ambient pressure conditions

Propiedades mecánicas de aerogeles híbridos de sílice

Flexible and Transparent Silica Aerogels: An Overview

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