Nanoindentation on hybrid organic/inorganic silica aerogels

Rosa–Fox, N. de la; Morales‐Flórez, Víctor; Toledo-Fernández, J. A.; Piñero, Manuel; Mendoza-Serna, R.; Esquivias, L.

doi:10.1016/j.jeurceramsoc.2007.02.209

Cited by 50 publications

(25 citation statements)

References 19 publications

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“…Such discontinuity, which sometimes occurs in load-displacement nanoindentation response, can be recognized as a pop-in event. Several studies have cast a light on the origin of pop-in events, which actually occur only in specific materials [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50]. The occurrence of pop-in, for example, has often been associated with localized shear [31][32][33][34][35][36][37][38][39][40].…”

Section: Analytical Analysis Of the Nanohardness Load-displacement Cumentioning

confidence: 99%

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Constitutive analysis for the quantification of hardness decay in a superlattice CrN/NbN hard-coating

Cabibbo

Clemente

Mehtedi

et al. 2015

Surface and Coatings Technology

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Section: Analytical Analysis Of the Nanohardness Load-displacement Cumentioning

confidence: 99%

“…The pop-in events in ZnO single crystal were claimed to be caused by the initiation of slip [38]. Microcracks in pore walls were thought to cause pop-in in silica aerogels [47]. In amorphous ZrCuTi/PdCuSi nano-laminates pop-in was linked to shear localization [48].…”

Section: Analytical Analysis Of the Nanohardness Load-displacement Cumentioning

confidence: 99%

Constitutive analysis for the quantification of hardness decay in a superlattice CrN/NbN hard-coating

Cabibbo

Clemente

Mehtedi

et al. 2015

Surface and Coatings Technology

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“…De la Rosa-Fox et al [20] also studied the mechanical characteristics of hybrid aerogels by using nanoindentation and creep tests. Their samples were prepared using mixtures of tetraethylorthosilicate (TEOS) and polydimethylsiloxane (PDMS or (…”

Section: Structure Of Ch 3 -Added Silica Aerogels and Xerogelsmentioning

confidence: 99%

“…They found that addition of organic components changes the behavior of the material from a brittle solid to a rubber elastomer; a result that was also found by Piñero et al [21] who studied the compressive properties of aerogels produced using the same precursors. From experimental results presented in [20], it is clear that the Young's modulus of the hybrid aerogels is reduced when the amount of organic material added is increased. However, it was also found that the hardness of the samples is reduced as well; a result that contradicts the findings of Martin et al [18].…”

Section: Structure Of Ch 3 -Added Silica Aerogels and Xerogelsmentioning

confidence: 99%

“…The changes of the mechanical properties of hybrid aerogels are due to the reorganization of the internal structure of the material when the amount of organic material is increased. If the structure has a small organic content, the mechanical response is dominated by the brittle inorganic structure, but when the amount of organic material surpasses a certain level an organic matrix is formed and the material becomes rubbery [20,21].…”

Section: Structure Of Ch 3 -Added Silica Aerogels and Xerogelsmentioning

confidence: 99%

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Structural and Mechanical Properties of Silica and Hybrid Aerogels and Xerogels Studied Using Molecular Dynamics Simulations

Murillo¹,

Sandro²

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The structural and mechanical properties of silica and hybrid aerogels and xerogels are studied using Molecular Dynamics simulations. Hybrid samples are created by adding methyl groups (CH 3) to the silica structure. Silica samples are generated expanding a dense silica glass in a simulation box of volume chosen to produce a porous sample of a specified density. The expanded glass is thermally treated using a combination of heating and cooling processes. The heating process increases the kinetic energy of the atoms in the system, which facilitates their movement throughout the system. The cooling process reduces the kinetic energy of the atoms and helps locking them in place forming the desired porous structure. A similar procedure is used to create the hybrid samples, but CH 3 −SiO 2 molecules are randomly inserted in the expanded structure before the thermal treatment of the sample. The structures are characterized estimating the fractal dimension of the samples. It is calculated using its relationship with the decay of the Pair Distribution Function of the samples in the intermediate range of structural arrangement. The fractal dimension of the samples used for this study compares favorably to the values found reported in experimental studies, which validates the preparation processes used here. The mechanical properties of the samples are obtained by modeling a tension test performed by stretching the sample along one direction. The stress vs. strain relationship is estimated for all the samples. The results reproduce trends similar to those reported from physical experiments. The computational models show that the addition of methyl groups reduces the stiffness of the structure allowing it to stretch more easily, and increasing the toughness of the samples. From the stress-strain plots is concluded that as the amount of methyl groups in the structure is increased also does the compliance of the sample, effectively making the nature of the material similar to a rubber-like material. These results are in agreement with physical experimental findings which show that adding methyl groups to silica allows compressing the samples more than 50% without destroying them. To my family, my life support.

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