Effect of uni-axial loading on the nanostructure of silica aerogels

Nikel, Ondřej; Anderson, Ann M.; Carroll, Mary K.; Keat, William

doi:10.1016/j.jnoncrysol.2011.05.009

Cited by 15 publications

(8 citation statements)

References 22 publications

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“…Aerogels are elastic under small strain but at larger strains undergo plastic deformation and irreversible structural changes . There have been several studies of aerogel bulk modulus, − which is found to depend on the density via a power law K ∝ ρ m with exponent m varying from 3.0 to 3.7 …”

Section: Introductionmentioning

confidence: 99%

Computational Study of Uniaxial Deformations in Silica Aerogel Using a Coarse-Grained Model

Ferreiro-Rangel¹,

Gelb

2015

J. Phys. Chem. B

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Simulations of a flexible coarse-grained model are used to study silica aerogels. This model, introduced in a previous study (J. Phys. Chem. C 2007, 111, 15792), consists of spherical particles which interact through weak nonbonded forces and strong interparticle bonds that may form and break during the simulations. Small-deformation simulations are used to determine the elastic moduli of a wide range of material models, and large-deformation simulations are used to probe structural evolution and plastic deformation. Uniaxial deformation at constant transverse pressure is simulated using two methods: a hybrid Monte Carlo approach combining molecular dynamics for the motion of individual particles and stochastic moves for transverse stress equilibration, and isothermal molecular dynamics simulations at fixed Poisson ratio. Reasonable agreement on elastic moduli is obtained except at very low densities. The model aerogels exhibit Poisson ratios between 0.17 and 0.24, with higher-density gels clustered around 0.20, and Young's moduli that vary with aerogel density according to a power-law dependence with an exponent near 3.0. These results are in agreement with reported experimental values. The models are shown to satisfy the expected homogeneous isotropic linear-elastic relationship between bulk and Young's moduli at higher densities, but there are systematic deviations at the lowest densities. Simulations of large compressive and tensile strains indicate that these materials display a ductile-to-brittle transition as the density is increased, and that the tensile strength varies with density according to a power law, with an exponent in reasonable agreement with experiment. Auxetic behavior is observed at large tensile strains in some models. Finally, at maximum tensile stress very few broken bonds are found in the materials, in accord with the theory that only a small fraction of the material structure is actually load-bearing.

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Section: Introductionmentioning

confidence: 99%

Computational Study of Uniaxial Deformations in Silica Aerogel Using a Coarse-Grained Model

Ferreiro-Rangel¹,

Gelb

2015

J. Phys. Chem. B

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“…Typical values were plotted for silica (1 = 0.1-0.2 g cm À3 ), RF (1 = 0.04-0.08 g cm À3 ), and carbon (1 = 0.08-0.3 g cm À3 ) aerogels. [2,[30][31][32][33] The values for cellulose aerogels were adapted from the literature. [11,12,[20][21][22] .…”

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confidence: 99%

Aerogels with 3D Ordered Nanofiber Skeletons of Liquid‐Crystalline Nanocellulose Derivatives as Tough and Transparent Insulators

2014

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Aerogels of high porosity and with a large internal surface area exhibit outstanding performances as thermal, acoustic, or electrical insulators. However, most aerogels are mechanically brittle and optically opaque, and the structural and physical properties of aerogels strongly depend on their densities. The unfavorable characteristics of aerogels are intrinsic to their skeletal structures consisting of randomly interconnected spherical nanoparticles. A structurally new type of aerogel with a three-dimensionally ordered nanofiber skeleton of liquid-crystalline nanocellulose (LC-NCell) is now reported. This LC-NCell material is composed of mechanically strong, surface-carboxylated cellulose nanofibers dispersed in a nematic LC order. The LC-NCell aerogels are transparent and combine mechanical toughness and good insulation properties. These properties of the LC-NCell aerogels could also be readily controlled.

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“…Typical values were plotted for silica ( ρ =0.1–0.2 g cm −3 ), RF ( ρ =0.04–0.08 g cm −3 ), and carbon ( ρ =0.08–0.3 g cm −3 ) aerogels 2. 30–33 The values for cellulose aerogels were adapted from the literature 11. 12, 20–22…”

mentioning

confidence: 99%

Aerogels with 3D Ordered Nanofiber Skeletons of Liquid‐Crystalline Nanocellulose Derivatives as Tough and Transparent Insulators

2014

View full text Add to dashboard Cite

Aerogels of high porosity and with a large internal surface area exhibit outstanding performances as thermal, acoustic, or electrical insulators. However, most aerogels are mechanically brittle and optically opaque, and the structural and physical properties of aerogels strongly depend on their densities. The unfavorable characteristics of aerogels are intrinsic to their skeletal structures consisting of randomly interconnected spherical nanoparticles. A structurally new type of aerogel with a three‐dimensionally ordered nanofiber skeleton of liquid‐crystalline nanocellulose (LC‐NCell) is now reported. This LC‐NCell material is composed of mechanically strong, surface‐carboxylated cellulose nanofibers dispersed in a nematic LC order. The LC‐NCell aerogels are transparent and combine mechanical toughness and good insulation properties. These properties of the LC‐NCell aerogels could also be readily controlled.

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Effect of uni-axial loading on the nanostructure of silica aerogels

Cited by 15 publications

References 22 publications

Computational Study of Uniaxial Deformations in Silica Aerogel Using a Coarse-Grained Model

Computational Study of Uniaxial Deformations in Silica Aerogel Using a Coarse-Grained Model

Aerogels with 3D Ordered Nanofiber Skeletons of Liquid‐Crystalline Nanocellulose Derivatives as Tough and Transparent Insulators

Aerogels with 3D Ordered Nanofiber Skeletons of Liquid‐Crystalline Nanocellulose Derivatives as Tough and Transparent Insulators

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