Ambient-temperature supercritical drying of transparent silica aerogels

Tewari, P. H.; Hunt, Arlon J.; Lofftus, Kevin

doi:10.1016/0167-577x(85)90077-1

Cited by 267 publications

(140 citation statements)

References 3 publications

Supporting

Mentioning

135

Contrasting

Unclassified

Order By: Relevance

“…Supercritical drying (SCD) is the first and most commonly used method for silica aerogels: Two different SCD methods can be distinguished: High temperature supercritical drying (HTSCD) [42] and low temperature supercritical drying from carbon dioxide (LTSCD) or the Hunt Process [74]. The method of HTSCD is not relevant for aerogels for building applications, though will be described to give a complete image and allow comparison.…”

Section: Supercritical Dryingmentioning

confidence: 99%

See 1 more Smart Citation

Aerogel insulation for building applications: A state-of-the-art review

Bætens

Jelle

Gustavsen

2011

Energy and Buildings

952

465

View full text Add to dashboard Cite

Aerogels are regarded as one of the most promising high performance thermal insulation materials for building applications today. With a thermal conductivity down to 13 mW/(mK) for commercial products they show remarkable characteristics compared to traditional thermal insulation materials. Also the possibility of high transmittances in the solar spectrum is of high interest for the construction sector. With the proper knowledge they give both the architect and engineer the opportunity of re-inventing architectural solutions. Within this work, a review is given on the knowledge of aerogel insulation in general and for building applications in particular.

show abstract

Section: Supercritical Dryingmentioning

confidence: 99%

“…The process of LTSCD [74] is similar to that of HTSCD and is also carried out in three steps: Firstly, the aged gel is placed in an autoclave, but now filled with the saver, non-flammable liquid carbon dioxide (i.e. T cr = 304.2 K, P cr = 72.786 atm [45]) at 4 to 10°C until 100 bar to replace the solvent in the pores of the gel.…”

Section: Supercritical Dryingmentioning

confidence: 99%

Aerogel insulation for building applications: A state-of-the-art review

Bætens

Jelle

Gustavsen

2011

Energy and Buildings

952

465

View full text Add to dashboard Cite

show abstract

“…Alternatively, one can perform a set of exchanges and replace the alcohol solvent with liquid carbon dioxide, which has a low supercritical temperature (~31 °C). The extraction can then be performed at relatively low temperature 8,9 , albeit at high pressure. Freeze drying methods 10,11 first freeze the wet gel at low temperature and then allow the solvent to sublimate directly to a vapor form, again avoiding crossing the liquid-vapor phase line.…”

Section: Si(och 3 ) 4 + H 2 Omentioning

confidence: 99%

Preparing Silica Aerogel Monoliths via a Rapid Supercritical Extraction Method

Carroll

Anderson

Gorka

2014

JoVE

View full text Add to dashboard Cite

A procedure for the fabrication of monolithic silica aerogels in eight hours or less via a rapid supercritical extraction process is described. The procedure requires 15-20 min of preparation time, during which a liquid precursor mixture is prepared and poured into wells of a metal mold that is placed between the platens of a hydraulic hot press, followed by several hours of processing within the hot press. The precursor solution consists of a 1.0:12.0:3.6:3.5 x 10 -3 molar ratio of tetramethylorthosilicate (TMOS):methanol:water:ammonia. In each well of the mold, a porous silica sol-gel matrix forms. As the temperature of the mold and its contents is increased, the pressure within the mold rises. After the temperature/ pressure conditions surpass the supercritical point for the solvent within the pores of the matrix (in this case, a methanol/water mixture), the supercritical fluid is released, and monolithic aerogel remains within the wells of the mold. With the mold used in this procedure, cylindrical monoliths of 2.2 cm diameter and 1.9 cm height are produced. Aerogels formed by this rapid method have comparable properties (low bulk and skeletal density, high surface area, mesoporous morphology) to those prepared by other methods that involve either additional reaction steps or solvent extractions (lengthier processes that generate more chemical waste).The rapid supercritical extraction method can also be applied to the fabrication of aerogels based on other precursor recipes. Video LinkThe video component of this article can be found at

show abstract

“…But the process was not safe yet to attain mass production. Hunt continued to investigate for improvements and came up with the idea of replacing the alcohol within the gel by liquid carbon dioxide before supercritical drying because CO 2 is inflammable and requires a lower temperature and pressure to become supercritical [26]. This would reduce any hazard risks and increase the energy efficiency, hence resulting in a cheaper manufacturing cost.…”

Section: Evolution Of Aerogelsmentioning

confidence: 99%

Flexible and Transparent Silica Aerogels: An Overview

Parale¹,

Lee²,

Park³

2017

J. Korean Ceram. Soc

View full text Add to dashboard Cite

Aerogels are highly porous structures prepared via a sol-gel process and supercritical drying technology. Among the classes of aerogels, silica aerogel exhibits the most remarkable physical properties, possessing lower density, thermal conductivity, refractive index, and dielectric constant than any solids. Its acoustical property is such that it can absorb the sound waves reducing speed to 100 m/s compared to 332 m/s for air. However, when it comes to commercialization, the result is not as expected. It seems that mass production, particularly in the aerospace industry, has dawdled behind. This paper highlights the evolution of aerogels in general and discusses the functions and significances of silica aerogel in previous astronautical applications. Future outer-space applications have been proposed as per the current research trend. Finally, the implementation of conventional silica aerogel in aeronautics is argued with an alternative known as Maerogel.

show abstract

Ambient-temperature supercritical drying of transparent silica aerogels

Cited by 267 publications

References 3 publications

Aerogel insulation for building applications: A state-of-the-art review

Aerogel insulation for building applications: A state-of-the-art review

Preparing Silica Aerogel Monoliths via a Rapid Supercritical Extraction Method

Flexible and Transparent Silica Aerogels: An Overview

Contact Info

Product

Resources

About