200px|thumb|right|[[Bata 2,5 kg nu numpang luhureun sapotong aérojél nu beuratna ukur 2,38 gram.]]
'''Aérojél''' téh bahan padet nu dénsitasna handap, dijieun tina jél anu komponén cairna geus diganti ku gas. Hasilna mangrupa padetan anu dénsitasna kacida handapna kalawan pasipatan anu penting, utamana salaku insulator.

Ieu bahan kadang sok disebut '''haseup beku''' (''frozen smoke''), '''haseup padet''' (''solid smoke''), atawa '''haseup bulao''' (''blue smoke''), dumasar kana watekna anu semi-transparan sarta pendaran cahya dina éta bahan. Tapi, mun dicabak, ieu bahan téh karasa kawas Styrofoam tina polistiréna.

Aérojél munggaran dijieun ku Steven Kistler taun 1931, hasil tumpangan jeung Charles Learned ngeunaan saha nu bisa ngaganti cairan dina selé (jéli) tanpa jadi ngariut.<ref>{{cite journal
| author = Kistler S. S.
| title = Coherent expanded aerogels and jellies
| journal = Nature
| year = 1931
| volume = 127
| issue = 3211
| pages = 741
| doi = 
}} 
</ref><ref>{{cite journal
| author = Kistler S. S.
| title = Coherent Expanded-Aerogels
| journal = Journal of Physical Chemistry
| year = 1932
| volume = 36
| issue = 1
| pages = 52 - 64
| doi = 10.1021/j150331a003
}}</ref>
kromia, jeung timbal oksida. Aérojél karbon mimiti dikembangkeun taun 1990-an.<ref>{{cite journal
| author =  Pekala R. W.
| title = Organic aerogels from the polycondensation of resorcinol with formaldehyde
| journal = Journal of Material Science
| year = 1989
| volume = 24
| issue = 9
| pages = 3221-3227
| doi = 10.1007/BF01139044
}} 
</ref>

== Pasipatan ==
Mun dicabak, aérojél karasa kawas busa nu hampang tapi kaku, antara Styrofoam jeung busa floral héjo nu sok dipaké nata déndritik, nu ngagundukkeun partikel-partikel buleud ukuran 2-5 nm. Gundukan ieu ngawangun tilu-diménsi ranté pori leuwih leutik ti 100 nm. Ukuran jeung dénsitas rata-rata porina bisa ditangtukeun waktu éta aérojél   dijieun.

Aérojél insulator panas anu kacida jétuna, sabab ampir teu bisa ditembus ku tilu cara alih panas (konduksi, jeung radiasi).  Ieu bahan alus pisan salaku inhibitor konvéktif, sabab udara teu bisa asup kana kisina. Aérojél silika hususna alus pisan salaku insulator konduktif, sabab silika sorangan goréng pisan dina ngonduksikeun panas—béda jeung aérojél logam nu sipat insulatorna teu pati alus. Aérojél karbon alus pikeun insulator radiatif, sabab karbon bisa nyerep radiasi infrabeureum nu ngalihkeun panas. Aérojél nu paling insulatif taya lian ti gabungan dua bahan ieu: aérojél silika nu ditambahan ku karbon. 

Kusabab watekna nu higroskopik, aérojél téh garing sarta désikan anu kuat. Jalma nu nyepeng aérojél hadéna mah maké sarung leungeun, ngarah kulit leungeunna teu garing.

Kusabab kandunganana lolobana udara, aérojél katémbong semi-transparan. Kelir anu némbongan taya lian alatan parondok ku wangun déndritik ukuran nano.

Kusabab hidrofilik, aérojél gampang pisan nyerep lembab nu balukarna jadi robah bentuk, kontraksi nepi ka ruksakna. Karuksakan ieu bisa dihulag ku olahan kimiawi, sahingga jadi hidrofobik.
left|thumb|200px|Démo pasipatan insulasi aérojél.

== Tipeu ==
=== Aérojél silika ===
Aérojél silika téh minangka tipeu aérojél paling galib dipaké sarta ditalungtik. Ieu téh mangrupa zat nu bahan dasarna silika, diturunkeun tina jél silika. Padetan anu dénsitasna paling handap nyaéta nanofoam silika (1 mg/cm<sup>3</sup>)<ref name=terms>[http://www.llnl.gov/IPandC/technology/profile/aerogel/Terms/index.php Aerogels Terms].  LLNL.</ref>, ronjatan tina 1,9 mg/cm<sup>3</sup><ref>"[http://www.llnl.gov/str/October03/NewsOctober03.html Lab's aerogel sets world record]". ''LLNL Science & Technology Review''.  Oktober 2003.</ref>, padahal dénsitas udara baé 1,2 mg/cm<sup>3</sup>.
<!--
Aérojél silika bisa nyerep radiasi infrabeureum. It allows the construction of materials that let light into buildings but trap heat for solar heating.

It has extremely low W·m/m<sup>2</sup>·K down to 0.004 W·m/m<sup>2</sup>·K),<ref>Thermal conductivity from the [http://hbcpnetbase.com/ CRC Handbook of Chemistry and Physics], 85th Ed. section 12, p. 227</ref><ref name=terms/> which gives it remarkable insulative properties.  Its melting point is 1,473 K (1,200 °C or 2,192 °F).

Silica aerogel holds 15 entries in the ''Guinness Book of Records'' for material properties, including best insulator and lowest-density solid.

Silica aerogel can protect the human hand from the heat of a blowtorch at point blank range.

=== Carbon aerogels ===
thumb|right|200px|Aerogel held by JPL scientist [[Peter Tsou]]
covalently bonded together. They have very high pyrolyzed. Depending on the density, carbon aerogels may be electrically conductive, making composite aerogel paper useful for electrodes in capacitors or deionization electrodes. Due to their extremely high surface area, carbon aerogels are used to create supercapacitors, with values ranging up to thousands of farads based on a capacitance of 104 F/g and 77 F/cm³. Carbon aerogels are also extremely "black" in the infrared spectrum, reflecting only 0.3% of radiation between 250 nm and 14.3 µm, making them efficient for solar energy collectors.

The term "aerogel" has been incorrectly used to describe airy masses of carbon nanotubes produced through certain chemical vapor deposition techniques—such materials can be spun into fibers with strength greater than kevlar and unique electrical properties.  These materials are not aerogels, however, since they do not have a monolithic internal structure and do not have the regular pore structure characteristic of aerogels.

=== Alumina aerogels ===

Aerogels made with aluminium oxide are known as alumina aerogels. These aerogels are used as catalysts, especially when "metal-doped" with another metal. Nickel-alumina aerogel is the most common combination. Alumina aerogels are also examined by NASA for capturing of hypervelocity particles; a formulation doped with gadolinium and terbium could fluoresce at the particle impact site, with amount of fluorescence dependent on impact velocity.

=== Other aerogels ===
SEAgel is a material similar to organic aerogel, made of agar.

== Mangpaat ==
thumb|right|[[Kebul béntang (spacecraft)|Stardust dust collector with aerogel blocks. (NASA)]]

There are a variety of tasks for which aerogels are used. Commercially, aerogels have been used in granular form to add insulation to skylights. After several trips on the weightless environment can produce particles with a more uniform size and reduce the Rayleigh scattering effect in silica aerogel, thus making the aerogel less blue and more transparent. Transparent silica aerogel would be very suitable as a thermal insulation material for windows, significantly limiting thermal losses of buildings.

Its high surface area leads to many applications, such as a chemical absorber for cleaning up spills (see adsorption). This feature also gives it great potential as a catalyst or a catalyst carrier.  Aerogel particles are also used as thickening agents in some paints and cosmetics.

Aerogels are being tested for use in targets for the National Ignition Facility.

Aerogel performance may be augmented for a specific application by the addition of dopants, reinforcing structures, and hybridizing compounds. Using this approach, the breadth of applications for the material class may be greatly increased.

200px|thumb|right|A 2.5 kg [[brick is supported by a piece of aerogel weighing only 2 grams.]]

 
'''Aerogel''' is a low-density solid-state material derived from thermal insulator. It is nicknamed '''frozen smoke''',<ref Name="Times081907"></ref> '''solid smoke''' or '''blue smoke''' due to its semi-transparent nature and the way light scatters in the material; however, it feels like expanded polystyrene (Styrofoam) to the touch.

Aerogel was first created by jam (jelly) jar with gas without causing shrinkage.<ref>{{cite journal
| author = Kistler S. S.
| title = Coherent expanded aerogels and jellies
| journal = Nature
| year = 1931
| volume = 127
| issue = 3211
| pages = 741
| doi = 
}} 
</ref><ref>{{cite journal
| author = Kistler S. S.
| title = Coherent Expanded-Aerogels
| journal = Journal of Physical Chemistry
| year = 1932
| volume = 36
| issue = 1
| pages = 52–64
| doi = 10.1021/j150331a003
}}</ref>

Aerogels are produced by extracting the liquid component of a gel through chromia and tin oxide. Carbon aerogels were first developed in the early 1990s.<ref>{{cite journal
| author =  Pekala R. W.
| title = Organic aerogels from the polycondensation of resorcinol with formaldehyde
| journal = Journal of Material Science
| year = 1989
| volume = 24
| issue = 9
| pages = 3221–3227
| doi = 10.1007/BF01139044
}} 
</ref>

== Properties ==
right|thumbnail|200px|[[Peter Tsou of NASA's Jet Propulsion Laboratory holding a sample of aerogel]]
To the touch, aerogels feel like a light but rigid foam, something between green floral foam used for arranging flowers. Despite what their name may suggest, aerogels are dry materials and do not resemble a gel in their physical properties but a dendritic microstructure, in which spherical particles of average size 2-5 nm are fused together into clusters. These clusters form a three-dimensional highly porous structure of almost fractal chains, with pores smaller than 100 nm. The average size and density of the pores can be controlled during the manufacturing process.

Aerogels are good thermal insulators because they almost nullify three methods of heat transfer (conduction and radiation). They are good convective inhibitors because air cannot circulate throughout the lattice. Silica aerogel is an especially good conductive insulator because silica is a poor conductor of heat—a metallic aerogel, on the other hand, would be a less effective insulator. Carbon aerogel is a good radiative insulator because carbon absorbs the infrared radiation that transfers heat. The most insulative aerogel is silica aerogel with carbon added to it. 

Due to its hygroscopic nature, aerogel feels dry and acts as a strong desiccant. Persons handling aerogel for extended periods of time should wear gloves to prevent the appearance of dry brittle spots on their hands.

Since it is 99.8% air, it appears semi-transparent. The color it does have is due to Rayleigh scattering of the shorter wavelengths of visible light by the nanosized dendritic structure. This causes it to appear smoky blue against dark backgrounds and yellowish against bright backgrounds.

Aerogels by themselves are hydrophilic, but chemical treatment can make them hydrophobic. If they absorb moisture they usually suffer a structural change, such as contraction, and deteriorate, but degradation can be prevented by making them hydrophobic. Aerogels with hydrophobic interiors are less susceptible to degradation than aerogels with only an outer hydrophobic layer, even if a crack penetrates the surface. Hydrophobic treatment facilitates processing because it allows the use of a water jet cutter.

== Types ==
left|thumbnail|A demonstration of aerogel's insulation properties.
right|thumbnail|Aerogel produced at [[Florida State University by Elliot Schwartz and Robert Palmer.]]

=== Silica aerogels ===
Silica aerogel is the most common type of aerogel and the most extensively studied and used. It is a silica-based substance, derived from silica gel. The world's lowest-density solid is a silica nanofoam at 1 mg/cm<sup>3</sup>,<ref name=terms>[http://www.llnl.gov/IPandC/technology/profile/aerogel/Terms/index.php Aerogels Terms]. LLNL.</ref> which is the evacuated version of the record-aerogel of 1.9 mg/cm<sup>3</sup>.<ref name="llnl03">"[http://www.llnl.gov/str/October03/NewsOctober03.html Lab's aerogel sets world record]". ''LLNL Science & Technology Review''. October 2003.</ref> The density of air is 1.2 mg/cm<sup>3</sup>.<ref http://pdg.lbl.gov/2007/reviews/atomicrpp.pdf>Groom, D.E. [http://pdg.lbl.gov/2007/reviews/atomicrpp.pdf Abridged from Atomic Nuclear Properties]. Particle Data Group: 2007.</ref>

Silica aerogel strongly absorbs infrared radiation. It allows the construction of materials that let light into buildings but trap heat for solar heating.

It has remarkable thermal insulative properties, having an extremely low W/m·K<ref>Thermal conductivity from the [http://hbcpnetbase.com/ CRC Handbook of Chemistry and Physics], 85th Ed. section 12, p. 227</ref> down to 0.004 W/m·K,<ref name=terms/> which correspond to R-factors of 14 to 105 for 3.5 inch thickness. For comparison, typical wall insulation is 13 for 3.5 inch thickness. Its melting point is 1,473 K (1,200 °C or 2,192 °F).

Silica aerogel holds 15 entries in ''Guinness World Records'' for material properties, including best insulator and lowest-density solid.

=== Carbon aerogels ===
covalently bonded together. They have very high pyrolyzed. Depending on the density, carbon aerogels may be electrically conductive, making composite aerogel paper useful for electrodes in capacitors or deionization electrodes. Due to their extremely high surface area, carbon aerogels are used to create supercapacitors, with values ranging up to thousands of farads based on a capacitance of 104 F/g and 77 F/cm³. Carbon aerogels are also extremely "black" in the infrared spectrum, reflecting only 0.3% of radiation between 250 nm and 14.3 µm, making them efficient for solar energy collectors.

The term "aerogel" has been incorrectly used to describe airy masses of carbon nanotubes produced through certain chemical vapor deposition techniques—such materials can be spun into fibers with strength greater than kevlar and unique electrical properties. These materials are not aerogels, however, since they do not have a monolithic internal structure and do not have the regular pore structure characteristic of aerogels.

=== Alumina aerogels ===
Aerogels made with aluminium oxide are known as alumina aerogels. These aerogels are used as catalysts, especially when "metal-doped" with another metal. Nickel-alumina aerogel is the most common combination. Alumina aerogels are also examined by NASA for capturing of hypervelocity particles; a formulation doped with gadolinium and terbium could fluoresce at the particle impact site, with amount of fluorescence dependent on impact velocity.

=== Other aerogels ===
SEAgel is a material similar to organic aerogel, made of agar.

Chalcogels are a type of aerogel made of chalcogens (the column of elements on the periodic table beginning with oxygen) such as sulfur and selenium, platinum, and other elements.<ref>Biello, David [http://sciam.com/article.cfm?chanId=sa003&articleId=044B7489-E7F2-99DF-3433709C76B127DF Heavy Metal Filter Made Largely from Air. ''Scientific American'', 2007-07-26. Retrieved on 2007-08-05.</ref> Research is ongoing, and metals less expensive than platinum have also been used in its creation.

Aerogels made of Cadmium selenide quantum dots in a porous 3-D network have recently been developed for use in the semiconductor industry<ref>{{cite journal
| author = H. Yu, R. Bellair, R.M. Kannan, S. Brock
| title = Engineering Strength, Porosity, and Emission Intensity of Nanostructured CdSe Networks By Altering The Building Block Shape
| journal = Journal of The American Chemical Society
| year = 2008
| volume = 130
| issue = 15
| pages = 5054-5055
| doi = 10.1021/ja801212e
}}</ref>

== Uses ==