Hydrophobic and physical properties of the ambient pressure dried silica aerogels with sodium silicate precursor using various surface modification agents

Rao, A. Parvathy; Pajonk, G.M.

doi:10.1016/j.apsusc.2006.12.117

Cited by 254 publications

(104 citation statements)

References 31 publications

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“…• C corresponding to the oxidation of -Si(CH 3 ) 3 groups and residual groups [23]. Thus, it is clear that the silica aerogels have high heat resistance up to approximately 435…”

Section: Thermal Stability Of Hydrophobic Silica Aerogelsmentioning

confidence: 95%

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A new route for preparation of sodium-silicate-based hydrophobic silica aerogels via ambient-pressure drying

Bangi

Rao

2008

Science and Technology of Advanced Materials

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An in-depth investigation into the synthesis of hydrophobic silica aerogels prepared by the surface derivatization of wet gels followed by subsequent drying at ambient pressure is reported. The following sol-gel parameters were examined for their effect on the physical properties of the derived aerogels: number of gel washings with water, percentage of hexane or methanol in silylating mixture, molar ratio of tartaric acid: Na 2 SiO 3 , gel aging period, weight% of silica, trimethylchlorosilane (TMCS) percentage, and silylation period. These parameters were varied from 1 to 4, 0 to 100%, 0.27 to 1.2, 0 to 4 h, 1.5 to 8 wt.%, 20 to 40% and 6 to 24 h, respectively. The properties of hydrophobic silica aerogels synthesized by this new route were investigated in terms of bulk density, percentage volume shrinkage, percentage porosity, thermal conductivity and contact angle with water, and by Fourier transform infrared spectroscopy (FTIR). The as-prepared hydrophobic silica aerogels exhibited high temperature stability (up to approximately 435• C) as measured by thermogravimetric/differential thermal analysis (TGA-DTA). The optimal sol-gel parameters were found to be a molar ratio of Na 2 SiO 3 : H 2 O : tartaric acid : TMCS of 1 : 146.67 : 0.86 : 9.46, an aging period of 3 h, four washings with water in 24 h and the use of a 50% hexane-or methanol-based silylating mixture. Aerogels prepared with these optimal parameters were found to exhibit 50% optical transparency in the visible range, 84 kg m −3 density, 0.090 W mK −1 thermal conductivity, 95% porosity and a contact angle of 146• with water.

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“…• C corresponding to the oxidation of -Si(CH 3 ) 3 groups and residual groups [23]. Thus, it is clear that the silica aerogels have high heat resistance up to approximately 435…”

Section: Thermal Stability Of Hydrophobic Silica Aerogelsmentioning

confidence: 95%

“…Kang and Choi [17], Jeong et al [18] and Wei et al [19] have prepared silica aerogels by employing surface modification and drying at ambient pressure. Kim and Hyun [20] as well as our group [21][22][23] have synthesized the silica aerogels employing the similar method.…”

Section: Introductionmentioning

confidence: 99%

A new route for preparation of sodium-silicate-based hydrophobic silica aerogels via ambient-pressure drying

Bangi

Rao

2008

Science and Technology of Advanced Materials

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“…The FT-IR spectrum represents a broad band at around 3500 cm −1 and a peak at around 1600 cm −1 , which can be attributed to O-H groups [24]. The peaks at around 1100 and 800 cm −1 are due to asymmetric and symmetric modes of SiO 2 [25]. The peaks at 2980 and 1450 cm −1 are assigned to C-H bonds, while the peak at 840 cm −1 is attributed to Si-C bond.…”

Section: Characterization Of Carbon-silica Aerogel Compositesmentioning

confidence: 99%

Adsorption and desorption performance of benzene over hierarchically structured carbon–silica aerogel composites

Dou

Wang

et al. 2011

Journal of Hazardous Materials

105

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a b s t r a c tHierarchically structured carbon-silica aerogel (CSA) composites were synthesized from cheap water glass precursors and granulated activated carbon via a post-synthesis surface modification with trimethylchlorosilane (TMCS) and a low-cost ambient pressure drying procedure. The resultant CSA composites possess micro/mesoporous structure and hydrophobic surface. The adsorption and desorption performance of benzene on carbon-silica aerogel composite (CSA-2) under static and dynamic conditions were investigated, comparing with pure silica aerogel (CSA-0) and microporous activated carbon (AC). It was found that CSA-2 has high affinity towards aromatic molecules and fast adsorption kinetics. Excellent performance of dynamic adsorption and desorption observed on CSA-2 is related to its higher adsorption capacity than CSA-0 and less mass transfer resistance than AC, arising from the well-developed microporosity and open foam mesostructure in the CSA composites.

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“…At the reaction temperature of 30 , the esterification conversion was 42.8 , which improved gradually to 71.8 while the reaction temperature increased to 70 . Generally, if the increasing of the reaction temperature, the liquid methanol vaporized into the gas phase, probably resulting in a lower conversion 23,24 . Considering energy consumption, the best temperature was chosen to be 70 .…”

Section: Effect Of Reaction Time On Oleic Acid Conversionmentioning

confidence: 99%

Biodiesel Production by Catalytic Esterification of Oleic Acid over Copper (II)–Alginate Complexes

et al. 2017

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Hydrophobic and physical properties of the ambient pressure dried silica aerogels with sodium silicate precursor using various surface modification agents

Cited by 254 publications

References 31 publications

A new route for preparation of sodium-silicate-based hydrophobic silica aerogels via ambient-pressure drying

A new route for preparation of sodium-silicate-based hydrophobic silica aerogels via ambient-pressure drying

Adsorption and desorption performance of benzene over hierarchically structured carbon–silica aerogel composites

Biodiesel Production by Catalytic Esterification of Oleic Acid over Copper (II)–Alginate Complexes

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