Hydrophobic and low density silica aerogels dried at ambient pressure using TEOS precursor

Gurav, Jyoti L.; Rao, A. Venkateswara; Bangi, Uzma K.H.

doi:10.1016/j.jallcom.2008.03.076

Cited by 55 publications

(13 citation statements)

References 14 publications

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“…The obtained WCA are reported in Table 1 . It is well known that the hydrophobicity of a sample is strongly dependent on the chemical properties of the surface [ 27 , 28 ]. Since the samples were subjected to a surface modification step with a silylation agent (HMDZ), the modified materials are hydrophobic or even superhydrophobic in some cases, with contact angles ranging from 137° to 156°.…”

Section: Resultsmentioning

confidence: 99%

Optimization of Polyamide Pulp-Reinforced Silica Aerogel Composites for Thermal Protection Systems

et al. 2020

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The present work describes for the first time the preparation of silica-based aerogel composites containing tetraethoxysilane (TEOS) and vinyltrimethoxysilane (VTMS) reinforced with Kevlar® pulp. The developed system was extensively investigated, regarding its physical, morphological, thermal and mechanical features. The obtained bulk density values were satisfactory, down to 208 kg·m−3, and very good thermal properties were achieved—namely a thermal conductivity as low as 26 mW·m−1·K−1 (Hot Disk®) and thermal stability up to 550 °C. The introduction of VTMS offers a better dispersion of the polyamide fibers, as well as a higher hydrophobicity and thermal stability of the composites. The aerogels were also able to withstand five compression-decompression cycles without significant change of their size or microstructure. A design of experiment (DOE) was performed to assess the influence of different synthesis parameters, including silica co-precursors ratio, pulp amount and the solvent/Si molar ratio on the nanocomposite properties. The data obtained from the DOE allowed us to understand the significance of each parameter, offering reliable guidelines for the adjustment of the experimental procedure in order to achieve the optimum properties of the studied aerogel composites.

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Section: Resultsmentioning

confidence: 99%

Optimization of Polyamide Pulp-Reinforced Silica Aerogel Composites for Thermal Protection Systems

et al. 2020

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“…All Nuclear Magnetic Resonance (NMR) spectra were collected with magic angle spinning (MAS) on a Bruker Avance III system equipped with a wide-bore 9.4 T magnet, corresponding to Larmor frequencies of 400.2 MHz for 1 H and 79.5 MHz for 29 Si.…”

Section: Nmr Ftir and Elemental Analysismentioning

confidence: 99%

“…1 He 29 Si cross polarization MAS NMR spectra were recorded with a MAS rate of 4 kHz in 7 mm zirconia rotors to maximize the sensitivity. All spectra were processed with matNMR [65] and calibrated according to a previously described procedure [34,66] ( Fig.…”

Section: Nmr Ftir and Elemental Analysismentioning

confidence: 99%

Effect of aging on silica aerogel properties

Iswar

Malfait

Balog

et al. 2017

Microporous and Mesoporous Materials

138

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Silica aerogels' unique physical and chemical properties make them fascinating materials for a wide variety of applications. In addition to hydrophobization by silylation, aging is very important in the synthesis of silica aerogel by ambient pressure drying. Here we systematically study the effect of aging on the physico-chemical properties of silica aerogel with emphasis on ambient dried materials. Silica gels were aged for different times and at different temperatures in their gelation liquid (without solvent exchange), hydrophobized in hexamethyldisiloxane and subsequently dried either at ambient pressure or from supercritical CO 2 . Dynamic oscillatory rheological measurements demonstrate that aging reinforces the alcogels, particularly at high strain. The specific surface area decreases with increasing aging time and temperature as a consequence of Ostwald ripening processes during aging. With increasing aging time and temperature, the linear shrinkage and bulk density decrease and the pore size and pore volume increase for the ambient dried gels, but remain nearly constant for supercritically dried gels. Small-Angle X-ray scattering does not detect significant structural changes at length scales smaller than about hundred nanometers, but hints at systematic variations at larger length scales. The findings of this study highlight the importance of aging to increase the ability of the gel particle network to withstand irreversible pore collapse during ambient pressure drying.

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“…In the present work, silica aerogel and hybrid silica aerogels/pseudowollastonite materials were obtained by ambient pressure drying (14,15) to eliminate the supercritical drying step. The materials received a surface treatment that induces the formation of a bioactive apatite layer on silica aerogel and hybrid silica aerogels/pseudowollastonite composites through a particular immersion method.…”

Section: Characterization Methodsmentioning

confidence: 99%

Novel bioactive materials: silica aerogel and hybrid silica aerogel/pseudowollastonite

Reséndiz-Hernández¹,

Cortés-Hernández²,

Saldívar-Ramírez³

et al. 2014

Bol. Soc. Esp. Ceram. Vidr.

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Hydrophobic and low density silica aerogels dried at ambient pressure using TEOS precursor

Cited by 55 publications

References 14 publications

Optimization of Polyamide Pulp-Reinforced Silica Aerogel Composites for Thermal Protection Systems

Optimization of Polyamide Pulp-Reinforced Silica Aerogel Composites for Thermal Protection Systems

Effect of aging on silica aerogel properties

Novel bioactive materials: silica aerogel and hybrid silica aerogel/pseudowollastonite

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