Synthesis and characterization of silica aerogels by a novel fast ambient pressure drying process

Shi, Fei; Wang, Lijiu; Liu, Jingxiao

doi:10.1016/j.matlet.2006.03.095

Cited by 210 publications

(119 citation statements)

References 16 publications

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“…During the reaction of EtOH/TMCS/hexane solution with wet gel, a similar phenomena as illustrated in literature [15] can be observed: transparent yellow liquid (the aqueous HCl phase) coming out from the wet gel and staying in the hexane phase, while the resulting modified wet gels floated to the top of the derived solution of aqueous HCl phase mainly consisting of water extruded from the pores of wet gels and the formed HCl. The major reactions involved with surface modification were as follows [14]:…”

Section: Mechanism Of Solvent Exchange/surface Modificationmentioning

confidence: 99%

“…From the preliminary experiments, the optimum molar ratio of pore water/TMCS/EtOH/hexane was 2.5/0.8/1/1 for silica surface modification [16]. This modification mechanism has been applied by Schwerfeger's et al [15] and Shi et al [14]. After the modification process, the hydrophilic property of the internal surface was modified to hydrophobic by isopropoxytrimethylsilane and TMCS that react with the -OH of the internal surface.…”

Section: Mechanism Of Solvent Exchange/surface Modificationmentioning

confidence: 99%

“…Recently, a new ambient pressure drying (APD) technique has been developed to overcome the disadvantages of conventional supercritical aerogel process, and made the manufacture and application of silica aerogel in large scale possible [12][13][14][15]. The key steps of this novel preparation method were solvent exchange and surface modification before the APD treatment.…”

Section: Introductionmentioning

confidence: 99%

“…Schwertferger et al [15] developed a process in which one-step solvent exchange and surface modification were simultaneously progressed by using a HMDSO (hexamethyldisiloxane)/TMCS (trimethylchlorosilane) solution for modification of the wet gels. Recently, Shi et al [14] also synthesized silica aerogels via one-step solvent exchange/surface modification of wet gels using an ethanol/TMCS/heptane solution.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Preparation and characterization of a novel silica aerogel as adsorbent for toxic organic compounds

Liu

Sha

Cooper

et al. 2009

Colloids and Surfaces A: Physicochemical and Engineering Aspect

108

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a b s t r a c tHydrophobic and hydrophilic silica aerogels were prepared from cheap waterglass precursors via surface modification of wet gels, ambient pressure drying (APD) route and calcination treatment. Xerogel was also synthesized as a comparison to test the influence of microstructure on the adsorption behaviours. Ethanol (EtOH)/chlorotrimethylsilane (TMCS)/hexane solution was employed to replace the surface silanol groups (Si OH) with alkyl, and to prevent the condensation and shrinkage of the gel structure during the APD process. The synthesized silica aerogels, characterized by using Fourier transform infrared spectra (FTIR), nitrogen adsorption/desorption measurement, element analyses and differential scanning calorimeter (DSC), etc., are porous and translucent solids with surface area of 546-907 m 2 /g. The transition temperature from hydrophobic to hydrophilic was tested around 395 • C, which corresponds to the disappearance temperature of the CH 3 peaks in FTIR. The materials were tested for adsorption capacities on rhodamine B (RhB) and dieldrin, which represented soluble and slightly soluble organic compounds, respectively. Results showed that the hydrophobic silica aerogel exhibited strong adsorption capacity on slightly soluble organic compounds while hydrophilic silica aerogel was much more effective on adsorbing soluble compounds from aqueous solution. Adsorption properties of the silica aerogel remain stable after 5 adsorption/desorption cycles.

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Section: Mechanism Of Solvent Exchange/surface Modificationmentioning

confidence: 99%

Section: Mechanism Of Solvent Exchange/surface Modificationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Preparation and characterization of a novel silica aerogel as adsorbent for toxic organic compounds

Liu

Sha

Cooper

et al. 2009

Colloids and Surfaces A: Physicochemical and Engineering Aspect

108

View full text Add to dashboard Cite

show abstract

“…This can be obviated by supercritical drying, that is, by drying in the absence of a vapor-liquid interface [9]. The use of surface modification agents can modify mechanical properties of wet gels in order to circumvent destruction of pore structure during drying under atmospheric or subcritical conditions [10], [11]. However, this has a drawback that the surface modification chemicals are carcinogenic and expensive.…”

Section: Introductionmentioning

confidence: 99%

A Simple Process to Prepare Silica Aerogel Microparticles from Rice Husk Ash

Kumar¹,

Vinjamur²,

Mukhopadhyay³

2013

IJCEA

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Abstract-Biocompatible silica aerogel microparticles are promising drug delivery vehicles because of their large surface area and open pore structures. A simple process has been developed in this work to prepare silica aerogel microparticles from rice husk ash, using water-in-mineral oil emulsion for sol-gel, followed by aging in ethanol to strengthen gel network and drying with scCO 2 . This process obviates drawback of current methods for silica aerogels. The effects of speed of agitation of water-oil mixture, sol-to-oil ratio and surfactant concentration have been investigated on particle size and size distribution, BET surface area, cumulative pore volume and pore diameter. A surface area of 654 m 2 /g, higher than the values reported for similar materials, could be obtained.Index Terms-Rice husk ash, silica aerogel microparticles, supercritical carbon dioxide, water-in-oil emulsion.

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Aerogel Spring‐Back Correlates with Strain Recovery: Effect of Silica Concentration and Aging

et al. 2021

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Silica aerogels display exceptional properties and great application potential, with a mature market in thermal insulation. Both supercritical drying (SCD) and ambient pressure drying (APD) routes are implemented industrially. Herein, how aging and silica content affect the mechanical properties, and how these in turn determine the shrinkage, spring back, and density during APD are systematically investigated. The APD densities display a U‐shaped dependence of density w.r.t. silica concentration. At low silica concentrations, the gels cannot withstand the capillary forces during APD and dense xerogels are obtained. At intermediate to high concentrations, APD shrinkage is strongly reduced and density increases with silica concentration. A series of cylinders are prepared by SCD and investigated by uniaxial compression and their strain recovery is determined systematically. The mechanical responses are plastic, viscoelastic, and brittle in nature for low, intermediate, and high silica concentrations, respectively. The strain recovery of the SCD cylinders correlates to the degree of spring back during APD. The viscoelastic response of SCD aerogels having 6 wt% corresponds to the silica concentration where a minimum in APD aerogel density is observed. The importance of gel mechanics for silica aerogel spring back during APD, in addition to surface modification and hydrophobization is highlighted.

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Synthesis and characterization of silica aerogels by a novel fast ambient pressure drying process

Cited by 210 publications

References 16 publications

Preparation and characterization of a novel silica aerogel as adsorbent for toxic organic compounds

Preparation and characterization of a novel silica aerogel as adsorbent for toxic organic compounds

A Simple Process to Prepare Silica Aerogel Microparticles from Rice Husk Ash

Aerogel Spring‐Back Correlates with Strain Recovery: Effect of Silica Concentration and Aging

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