Talk:Aerogel/Archive 1

Archive 1

Untitled

Delisting from GA because the article has no statement of references, which his a required thing in order to become a GA. AndyZ 00:20, 7 January 2006 (UTC)

Strength

Quote from the article: Aerogel can support 2000 times its own weight without collapsing

What does that mean? If something made of aerogel is high enough it will collapse due to its own weight. 193.171.121.30 13:09, 1 Sep 2004 (UTC)

It means that Aerogel is as strong as... paper! ...Unwrap and stack 5 reams of paper. The bottom sheet is holding up 2499 other sheets of paper, without collapsing. 69.134.202.192 17:30, 4 November 2005 (UTC)

Indeed. 193.171.121.30 14:20, 13 January 2006 (UTC)

It should quote compressive strength instead. 193.166.173.23 12:41, 25 July 2006 (UTC) Hmm not signed in, User:Santtus

The thing with that is, paper is much denser material and you'd expect something mainly made of low-pressure air (vs, say, a pressurised, thick walled car tyre...) to be just a wee bit more fragile. Not able to hold up a heavy brick. 193.63.174.10 (talk) 17:09, 19 November 2008 (UTC)

Edited this, but I had to revert it back after fact-checking:

An often quoted anecdote tells that its able to hold over 2000 times its own weight; more spefically, silica aerogal has a specific compressive strength of 3.89*10^5 Nm/kg.

This applies for Isocyanate-crosslinked Nanostructured Silica Aerogels, not all aerogels - http://coeweb.eng.ua.edu/aem/people/samit/aerogel.htm

I'll try to edit this for the better when I have time. Santtus 13:29, 25 July 2006 (UTC)

http://www.cement.ca/cement.nsf/e/4366443DA425F3C3852568A8007B9157?OpenDocument Most general-use concrete has a compressive strength between 20 and 35 MPa. High-strength concrete by definition, has a compressive strength of at least 70 MPa. Compressive strengths up to 140 MPa have been used in special bridge and high-rise building applications.

Now the absurd statement about supporting 2000 times its own weight made it to the main page. It really should be removed, or replaced by something meaningful. As hinted by 69.134.202.192 above, paper can do this too - four sheets of standard xerox paper weigh about 22 g; an elephant shot in 1956 weighed about 12 000 kg, which is more than half a million times as much. If you stood that elephant with one leg on each sheet, the paper would be supporting 500000 times its own weight. But if you built a pillar of any material, e.g. the strongest steel, once it got tall enough, it would collapse under its own weight.--Niels Ø (noe) 14:05, 19 May 2007 (UTC)

I have removed the statement from the article; here it is:

, able to hold over 2000 times its own weight; a new aerogel developed in India reportedly held over 500,000 times its own weight, ref Scientists develop aerogel, India Times

The source seems to be a journalist (not an appropriate source for a dubious statement of a technical nature), and it only mentions the value 500 000, not 2000.

Buying aerogel

Anyone got any idea where one could buy samples of aerogel? Even ebay failed me. --80.136.211.137 11:39, 19 Dec 2004 (UTC)

According to [1], it's possible to order from a few companies, but costs $1,000 a liter. They say to Google.

[www.cabot-corp.com], if you are willing to live with granules and not chunks.

I wonder how much does 1kg of aerogel cost?

-Probably a crapload of money, since aerogel weighs next to nothing and 1 liter costs $1,000. —Preceding unsigned comment added by 72.224.32.11 (talk) 01:17, 8 March 2010 (UTC)

you can buy some [[2]] <--there (though its out of stock)12.74.208.248 (talk) 01:27, 13 August 2008 (UTC)

---

I found some at [3], and [4], but they're quite expensive and in small pieces. I wasn't able to find largish chunks (like in the NASA photos) at anything but astronomical prices... chihowa 01:28, 18 Apr 2005 (UTC)

United Nuclear has some small pieces of Aerogel here :http://www.unitednuclear.com/aerogel.htm Mariushm 12:30, 4 January 2007 (UTC)

You can obtain samples of aerogel composites (fiber reinforced aerogel materials) from Aspen Aerogels at no cost. [5]

How much would it cost to buy a ping-pong ball (or something similar) made of aerogel? One can't help but wonder... toys made of aerogel would be pretty awesome. —Preceding unsigned comment added by 72.224.32.11 (talk) 01:20, 8 March 2010 (UTC)

Aerogel Samples can be purchased inexpensively at http://www.buyaerogel.com . Larger samples will be available in the near future (spring 2011). —Preceding unsigned comment added by 69.126.74.143 (talk) 20:05, 21 September 2010 (UTC)

---

Other useful information about its thermal conductivity as R value is not given in the article. U wonder if this material is not available for any sensible use what is the sense in discussing about it. Some company should make it available for refrigeration industry and for that a cheap and plausible method for mass producing it be developed. As power saver this material is of immense importance. Pathare Prabhu (talk) 04:41, 5 May 2011 (UTC)

Colour

It appears bluish because the silicon dioxide scatters shorter wavelengths

Shouldn't this read that is scatters longer wave lengths, blue light is at the short end of the spectrum, it would have to scatter the red light out to appear blue. Change it if you agree.

No, it is correct that it scatters shorter wavelengths - think about it, you only see the blue light because it has been scattered! Same thing with the sky - the sky appears blue because the blue light is scattered in all directions, including into your eyes. As the aerogel FAQ linked in the article says, if you look through a piece of aerogel directly at a white light source, you will see that the light appears yellow, because the blue light is scattered out of the way. It is the same phenomenon as the same way that the sun appears yellow/orange/red, especially at sunrise/sunset when you are looking through a greater depth of atmosphere. See [6] for example, for confirmation that it is scattering of shorter (blue) wavelengths that gives the blue appearance. Also NASA's aerogel FAQ [7] - "The very small particles that compose the aerogel scatter blue light, the same as our atmosphere scatters blue light." 143.252.80.124 13:15, 28 July 2005 (UTC)

By the same analogy, one would expect it to look reddish or yellowish if lit directly from behind (think of sunset). But does it? Zaha 11:21, 14 January 2006 (UTC)

It certainly does! Just look at the photo in the article. The lighter background shows up as red/orange when viewed through the aerogel, whereas the light that is scattered by the aerogel from the photography lights (you can't see them in the picture) is light blue. Robotbeat 20:09, 17 February 2006 (UTC)

... That it looks like a piece of smoke cut out of the air makes it curiously similar to Marvel Comics' "Hydrogel" fictional substance, which came out -years- earlier if I'm not mistaken.

Earlier than 1931??? http://www.nature.com/doifinder/10.1038/127741a0 <<< Link 2 in the main article's cite list. 193.63.174.10 (talk) 18:46, 19 November 2008 (UTC)

Dendritic link

Should

• a highly dendritic structure

actually link instead to Dendrite (metal)? --Malcohol 08:46, 14 September 2005 (UTC)

"Liquid carbon dioxide"

It's a while since I did any chemistry but doesn't carbon dioxide sublime directly from solid to gas?

• Answering my own question:

"Liquid carbon dioxide forms only at pressures above 5.1 atm; at atmospheric pressure, it passes directly between the gaseous and solid phases in a process called sublimation."

Should silica aerogel be separated into its own section? It is currently so intermingled with the rest of the discussion that it is hard to tell the difference between aerogel and silica aerogel.

Use as Capacitors

"Due to their extremely high surface area (about 800 m²/g), carbon aerogels are used to create supercapacitors, with values ranging up to thousands of farads. The capacitances achieved were 104 F/g and 77 F/cm₃."

The first sentence refers to general use of aerogels as capacitors, but the second seems to refer to a specific case of a capacitor made using aerogels. Which source is this from? This paragraph should either be reshaped to refer to the specific example from the second sentence (perhaps with more details) or generalized. I'm not sufficiently familiar with the subject matter to have much to contribute.

to the touch

There are several highly technical descriptions of the properties of aerogel on this page but very little of what it's like to actually hold it. It's obviously very light but there's more then that. Currently all the article says is "it feels like hard plastic foam" but foam doesn't shatter like glass as this is excerpt from nasa's site notes:

"What happens if I touch it? Silica aerogel is semi-elastic because it returns to its original form if slightly deformed. If further deformed, a dimple will be created. However, if the elastic limit is exceeded, it will shatter catastrophically, like glass."

Should this be included as a quote, rephrased, or has someone actually held aerogel and can do better? Vicarious 15:18, 22 November 2005 (UTC)

I added some additional text on handling the material (I've got quite a few chunks of it in my lab and office, as well as granules and powder. I work with it all the time as a thermal insulation material). If I give a chunk of it to someone, the first thing they always do is squeeze it, which makes it break up into a gazillion tiny shards which disappear forever in my carpet.

If someone has a good idea for pictures I could take of aerogel, I can upload something -- Kaszeta 16:15, 22 November 2005 (UTC)

Perhaps the shards of the material, with detail of the fracture surfaces? Or a picture of a laser pointer beam going through the material? --Shaddack 21:18, 22 November 2005 (UTC)

All good ideas. I'll see what I can do. -- Kaszeta 04:03, 23 November 2005 (UTC)

The laser experiment wasn't all that good, I need a stronger laser. And it's very, very hard to get good images of the fracture surfaces. But the images I did get are available here if someone wants them (and let me know if any of them need relicensing. -- Kaszeta 19:26, 15 May 2006 (UTC)

I noticed your captions state it's a 4kg block of granite on a .5g piece of aerogel. Currently the article says aerogel can hold over 2000 times it's own weight, but it appears you did 8000 times without incident. Do you have any ideas what the threshold is likely to be? Is it near 16,000 times? The article currently isn't wrong, but it seems excessively modest also. Vicarious 23:45, 15 May 2006 (UTC)

I think the article is giving typical values. The 8000x loading I show in that picture is very close to the threshold (looking at the block, I scalloped off some of the edges). Really, it depends on a lot of factors how much you can load it; I've got the stuff in powdered form and you can grind in a mortar and pestle without it losing volume (i.e. once the particles get small enough, their specific strength is enough to keep them from getting ground down further). On the flip side, it's very difficult to handle the stuff without chipping corners off of it. Strong for it's weight doesn't mean strong... -- Kaszeta 13:12, 16 May 2006 (UTC)

Maybe I'm confused here, but are ALL aerogels supposed behave in a similar fashion to what is written? Because I have some CdSe aerogel sitting right in front of me that is so delicate that it will crumble if you blow on it. Rather than have a feel similar to Styrofoam, it has the feel of ash. It seems the article is written with a specific material in mind, but is treated as though all aerogels have the same physical properties. I think that all of the text referring to how aerogels "feel" to the touch and how they react to pressing on them should be removed or at least be edited to specify which aerogels specifically are being described. The_spacemonkey

CdSe aerogel?! Wow! What is it used for? How is it handled, to avoid damaging it? Can I see photos of it? What colour is it? Thanks --DaveDodgy (talk) 18:17, 8 April 2008 (UTC)

Hi Dave, check out this publication for info on CdSe Aerogel. J. Am. Chem. Soc., 130 (15), 5054–5055, 2008 The_spacemonkey —Preceding unsigned comment added by The spacemonkey (talk • contribs) 14:17, 7 July 2008 (UTC)

Carbon aerogels

hmm, where are things like carbon aerogels? A bit too focused on silicat aerogels and a bit too much razzle-dazzle with nice numbers (which are wrong if you want to define the subject and right if you want to give some "extremes" as an example). --Saperaud 19:05, 13 September 2005 (UTC)

Under "Applications," this does not seem like a true aerogel: "In aircraft de-icing, a new proposal uses a carbon nanotube aerogel. A thin filament is spun on a winder to create a 10 micron-thick film, equivalent to an A4 sheet of paper. The amount of material needed to cover the wings of a jumbo jet weighs 80 grams (2.8 oz). Aerogel heaters could be left on continuously at low power, to prevent ice from forming." -- Sean (talk) 14:24, 29 January 2014 (UTC)

I put it there. The source calls it that. Unless another source says otherwise... Lfstevens (talk) 18:01, 29 January 2014 (UTC)

Major revamp

Although this is a "good article" I think it needs a significant remodel, which I have already begun. The portion before the table of contents was far too long and specific. I reorganized a little but I think the current section Silica aerogel needs to be split into two categories, the second being titled Silica aerogel and the first being titled properties, where silica aerogel only mentions the aspects that are unique to the silica variety. I also think the intro needs to be a little bit larger then I have made it.

Much of the Silica aerogel section includes uses which as much as possible should be moved to the uses section.

There's a bit too much esoteric lingo in my opinion such as diaphanous and hygroscopic. I wikified hygroscopic and replaced diaphanous with the synonymous but more readable translucent, but there are still many more difficult words.

I also noticed one glaring problem that became more obvious when I rearranged some paragraphs. "Carbon aerogels were first developed in the early 1990s." "Kistler's work involved aerogels based on silica, alumina, chromia, tin and carbon." Kistler died in 1975 so unless he developed carbon aerogels 15 years after his death this discrepancy needs rectified. Vicarious 15:41, 6 December 2005 (UTC)

In responce to Vicarious

I have never heard of Kistler making any form of carbon aerogel. it is neither mentioned in either his nature or J. Phys. Chem. paper. although interestingly he made aerogel from egg white.

• I changed the article to reflect this but I would much prefer that someone find a source that says carbon aerogels were invented in the 90's. Vicarious 03:51, 9 January 2006 (UTC)

15 Guinness Records?

I've seen this statement many times related to aerogel (including in this Wiki):

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

But I have yet to find what records it holds other than the two mentioned. Is this just a myth? What are the 13 others?

I have trouble with the claim that it's the lowest density solid. To my understanding, the silica aerogel is a mixture of silicon dioxide and air, so can it really considered a solid in the chemical sense? It seems like it should be more like "lowest density solid material" where solid is an adjective describing a property. Then again, I could be completely wrong. Can anybody who knows lots of chemistry sort this out? 63.226.241.188 09:35, 12 August 2006 (UTC)

I'd guess Guinness interprets "solid" as "solid material", and not in the scientific sense of the word "solid".

I added a fact tag to the "15 records" claim. While Guinness' terminology may be imprecise, there is a citation for its holding the lowest-density solid record. I also removed the subsequent sentence, fact-tagged last month, saying it would protect a hand from a point blank blowtorch; likely sources is MSNBC's Space chemist cooks up ‘solid smoke’, but without stating the thickness of the aerogel, it's a scientifically meaningless claim. -Agyle 17:35, 7 August 2007 (UTC)

Are you looking in the book? Bear in mind the online site only has a few of the records, as it says itself Nil Einne 05:13, 13 August 2007 (UTC)

I'm guessing they mean "lowest density thing you could build a house with", or lowest density continuous material (because a load of sand thrown into the air would be less dense, but has no structural integrity). You'd count Polystyrene as "solid", surely, and that's most of the way to aerogel. Just with thicker structural bits and less air. 193.63.174.10 (talk) 17:05, 19 November 2008 (UTC)

Aerogel as the most expensive commodity by weight?

This web page [8] makes the sugestion that it may be world's most expensive commodity by weight (assuming he meens avalable for private indivuals) at $US2083 per gram. I have to assume the web page author is talking about silica aerogel. It may make a good additon if some way was found to verify/reference it. Any thoughts?--Blue520 10:39, 27 March 2006 (UTC)

Not really sure if it can be seen as commodity but manny products used in biochemistry easilly cost more then that for example the chemical Ethylidenecyclooctane at 3086€/gram or some Protein Phosphatase substrates like PP2A2 at 444600€/gram (sold per micro-gram for obvious reasons). But I think they can be classified as commodities because there is a bigger market for these things then for pure aerogel wich can't be bought "en masse" from internet and these can for example. (source is a MP catalog)

According to Nuclear isomer, "Ta-180m is also one of the most expensive substances to procure in the world: It costs approximately $17 million per gram". So that far beats even biochemical examples. However, it is questionable whether you can classify it as a commodity, since I doubt its easy to acquire a gram of it even if you had $17m to spare. --SJK (talk) 00:10, 23 March 2008 (UTC)

Question aerogel thermal conductivity claim ...

Could an expert please verify/comment on the extremely low claimed thermal conductivity:

0.003 W/m.K - best insulator in Guiness Book of World Records - for SEAgel. (The SEAgel Wikipedia page doesn't repeat this claim.)

The explanation given for it being a good conductive insulator is:

"Silica aerogel is a good conductive insulator because silica is a poor conductor of heat" Yet a Google search returns an unremarkable thermal conductivity for silica, as might be expected: http://www.azom.com/details.asp?ArticleID=1114 reports 1.3 (1.4) W/m.K for quartz (fused silica).

Since the aerogel is mostly air, a reasonable expectation would be a heat conduction value

similar to air, as I understand is the case with the best (i.e. closed cell) insulators based on air. The Wikipedia thermal conductivity article states the conductivity of air to be 0.0262 W/m.K and the Engineering Toolbox, http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html, gives it as 0.024 as well as giving a generic entry "Insulation materials 0.035 - 0.16".

If I could hazard a guess, would it be possible that someone somewhere has inadvertantly stuck

in an extra zero in the the SEAgel conductivity and this error has been propagated? (Compare with the iron content of spinach, which I understand used to be a factor of 10 too high in many nutrition tables.) Or could there instead be some valid physical reason why SEAgel does an order of magnitude better than its dominant constituent, air?

Expert comments would be much appreciated ...

Thanks, 202.74.220.117 02:19, 30 March 2006 (UTC)Bruce P.S. I have also put this comment in the thermal conductivity page, where the low value (0.003) also appears and it was noted in the comments that it had been reduced to this from 0.017.

The page currently has the thermal conductivity listed as 0.03 w/mk versus a value listed as 0.003 in the thermal conductivity page. One or both of these should be fixed. --Jsnow 06:27, 22 May 2007 (UTC)

Further on querying aerogel's record low thermal conductivity

Thanks to njh and Kjkolb for very helpful replies to my query that are given on the comments page for http://wiki.riteme.site/wiki/Thermal_conductivity . To add further information, Google returned a reference http://eetd.lbl.gov/ECS/aerogels/satcond.htm that quotes a typical total conductivity of 0.017 W/m.K for silica aerogels (i.e. the original value in the table that agrees well with the 0.016 recommendation of Kjkolb, and that was replaced by the value 0.003 W/m.K that I query). This is actually a well written and informative article on the thermal conductivity characteristics of aerogels and is part of an excellent more general write-up on aerogels, http://eetd.lbl.gov/ECS/aerogels/satoc.htm , that I would recommend as a reference for this topic, http://wiki.riteme.site/wiki/Aerogel . At the risk of complicating this discussion, the thermal article also hints at another way that a thermal conductivity of 0.003 W/m.K might conceivably have been reported: they themselves report a similar minimum value for a silica aerogel with added carbon of ~0.0042 W/m.K . Crucially, however, this is by *evacuating* the aerogel - which is clearly not legitimate for a thermal conductivity table. (To show how absurd this would be, the record-holder for insulating materials in the Guinness Book of Records would then have to be for the trace gases in an ultra-high vacuum and that thermal conductivity would be dominated by radiative transfer and would depend on the temperature and emissivity of the vacuum walls rather than the thickness of the vacuum - in short, the coefficient of a total thermal conductivity with units of W/m.K ceases to make much sense for vacuum environments.) To give a second recommendation, I agree with Kjkolb that the entry in the table could be 0.016 or 0.017 W/m.K for a "typical silica aerogel". Or instead it could be left out of the table since the table doesn't yet even include such common and important substances as water: the value for water is 0.58 W/m.K, given in http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html . This is a good comprehensive reference and my third recommendation is to add this to the general references for http://wiki.riteme.site/wiki/Thermal_conductivity . Regards, 202.74.218.111 11:32, 30 March 2006 (UTC)Bruce P.S. I have also posted this on the comments page for http://wiki.riteme.site/wiki/Thermal_conductivity .

health risks?

I think it would be interesting to know if there are health risks when handling Aerogel. From this photo of the person with the gel, it appears that he has no problem with breathing in some particles. Touching seems to be ok too, except causing dry skin. --84.178.112.91 12:08, 19 May 2007 (UTC)

Melting point

It says that the melting point is 1200 degrees Celsius. It is reasonable to provide only 2 significant digits, since the melting point would vary based on the method used to produce the aerogel and because it is a colloidal suspension it is difficult to define an exact melting point. However, it says 1473 Kelvin and 2192 Fahrenheit, which have 4 significant digits (these would be right if 1200 was exact) and thus a misleading precision. Therefore I propose that it be corrected to 1500 degrees Kelvin and 2200 degrees Fahrenheit. Bbi5291 22:52, 21 July 2007 (UTC)

Or, just maybe, that *is* PRECISELY 1200 'C ? (or precise to the nearest degree) ... it's only a 1-in-100 chance that this would be true after all. Still, clarification needed. 193.63.174.10 (talk) 16:58, 19 November 2008 (UTC)

Costs and other info

http://aerogel.nmcnetlink.com/aerogel-cost-manufacturability.html

That's the company that provides the aerogel for Burton's $550 extreme weather jacket.

History Section?

I know aerogels are fairly new, but some of the items in various sections seems like they could be reformed into a history section. Thoughts? --mariusstrom 16:42, 7 August 2007 (UTC)

I agree that a history section would be useful, as I've read a couple articles which refer to a story about someone placing a bet regarding the ability to replace the water in a water-glass mixture with a gas as the first example the fabrication of silica-aerogel. I'll have a look at some papers I've got and see if I can substantiate this, and maybe provide some material to be placed in a history section. Matthew Rollings (talk) 10:56, 24 October 2008 (UTC)

Fairly new? The Introduction says in the second paragraph that the first aerogel was made in 1931. The first two references are from the 1930s.

I remember seeing an article about aerogels decades ago in a then very old Scientific American in a used bookstore. It could have been dated any year before 1960 or so and may have been from the 1930s. Perhaps someone could track it down or other old references. Aerogels are both old and new in the sense that they are a material that was once a curiosity and can now be combined with other new technologies like rocket chasing comets, microelectronics and sustainable development. The best way to invent new stuff is to combine old and new ideas or ideas from different disciplines to make something even better, after all people were clever even back then --Dgroseth (talk) 17:39, 2 July 2009 (UTC)

"Aerogels" by Jochen Fricke, Scientific American, May 1988, pp. 92-97. SimpsonDG (talk) 14:17, 6 October 2010 (UTC)

updating article

posted link that has some more current information if somebody has primary sources here they could update article. Irate velociraptor 18:32, 19 August 2007 (UTC)

other stuff

What happens if you try to file aerogel or drill into it? how do you cut it? T.Neo 18:48, 11 October 2007 (UTC)

Filing will slough off small particles, similar to rubbing unglazed fired clay pots together. Drilling is difficult, unless the aerogel has been reinforced somehow. Cutting is similarly difficult. In both cases, high speed is best to prevent catastrophic damage. The manufacturing process, however, is extremely friendly to cast-in-place fabrication, so usually drilling isn't needed. Ryanmaloney (talk) 03:25, 26 March 2009 (UTC)

Thermal Conductivity SI units

The thermal conductivity is given as '(0.03 W·m/m2·K down to 0.004 W·m/m2·K)' I believe, referencing wikipedia's own thermal conductivity page and NIST that the corrrect scientific units are Watts per metre kelvin, which would be W/(mK) (or similar, excuse my formatting), is this correct? I have not edited the article. —Preceding unsigned comment added by Cjeam (talk • contribs) 17:50, 21 December 2007 (UTC)

m/m2 = 1/m, so it's just a matter of formatting.

Wouldn't it make sense to format it in the simplest manner possible, regardless? That W-m/m2-K thing does look needlessly convoluted, and as stated, is non-standard. 193.63.174.10 (talk) 17:02, 19 November 2008 (UTC)

Aerogel density

The section on silica aerogels claim that the density is 1 mg/cm3 and that air's density is 1.2 mg/cm3. I looked at the reference cited and the substance is claimed to be 99.98% air so it should be very close to 1.2. I think this is a significant digit issue and should be edited because it appears to claim this substance is ~15% lighter than air, which it is not. Andyjf (talk) 19:17, 24 January 2008 (UTC)

The density reported is for an evacuated sample. For the same density in air, multiply the porosity (usually ~99%) by 1.2 mg/cc and add it to the evacuated density to get around 2.2 mg/cc.Ryanmaloney (talk) 03:28, 26 March 2009 (UTC)

Definition

Article says: Typically, aerogels are composed of 90-99.8% air, Is this by weight or volume?

I'd presume both, given that the huge difference in density between air and anything you'd typically use as the solid substrate would make for only a small disparity in overall mass. Until you get down to/near the 99.8% point, the majority of the mass within is still going to be solid material. Even soap bubbles (the ultimate aerogel) are still noticably heavier than air. And as stated in the article itself, a gel where the bubbles actually enclose vacuum only just manages to be a little lighter than air rather than dramatically so - the much smaller volume of solid very-nearly making up for the large amount of air "missing" from the enclosed space, to the point where you probably couldn't make any kind of enclosed wingless/non-helium-supported aircraft with it as even the thinnest of skins (to ensure the vacuum stays sealed inside and improve the hull integrity) would badly compromise the air-buoyancy. 193.63.174.10 (talk) 16:57, 19 November 2008 (UTC)

Porosities of aerogels are usually given as volume percent. Assuming densities of 1.2 mg/cc for air and 2 g/cc for dense silica, a volume percent porosity of 90% would translate to only about a 20% porosity by weight. (Please excuse any improper formatting - new to wiki and getting the hang of it).Ryanmaloney (talk) 03:22, 26 March 2009 (UTC)

Funny fact request

Wikipedia's funniest fact request ever:

Silica aerogel holds 15 entries^{[citation needed]} in Guinness World Records for material properties, including best insulator and lowest-density solid.

I cannot stop laughing over this. Said: Rursus ☻ 13:49, 7 March 2008 (UTC)

Would a link to the Guinness Records site be sufficient? :) Or to a search engine or online book store? 193.63.174.10 (talk) 16:59, 19 November 2008 (UTC)

Source material

Excellent source document if it's not already been used: Aerogel Research at LBL: From the Lab to the Marketplace, published 2001-04. It gives the early history of development. —Sladen (talk) 12:44, 13 July 2008 (UTC)

Molecular structure of aerogel

Blobs-and-beams. This is recent research using X-ray diffraction. Computational results gave out stronger properties of aerogel than actual samples, so the brave team went on to investigate... source is http://www.sciencedaily.com/releases/2008/07/080731173201.htm Results of the research may help to construct aerogel of greater mechanical strenght--213.158.196.85 (talk) 14:44, 28 August 2008 (UTC)

"Times smaller than"

This syntax seems to have come into use in recent years, apparently because it seems to be less awkward than using terms to describe fractions. However, it is logically absurd (sorry!). Do the numbers: A millimeter is not 10 times smaller than a centimeter. "Times" refers to the first, the original entity described. In this instance, it's a millimeter. Ten times one millimeter is 10 millimeters, or one centimeter. Saying that a millimeter is ten times smaller means that it is one cm smaller than one cm, which is zero!

Matters can become even more interesting if there isn't the coincidence of units in that example. Let's say that something was originally 8 cm wide, and the new version is 2 cm wide. If you say that the newer version is 4 times smaller, and do the numbers, it's 4*8 cm, or 32 cm smaller. That means the newer item has a dimension of -24 cm! Shades of the smile of the Cheshire Cat.

If the original is 10 cm, and the new is 8 cm, it would be correct to say that the new is 0.2 times smaller than the original, but such unfamiliar syntax would be distracting.

One also needs to be careful of "times larger than". "Larger" implies added size, not a scale factor. If a given shelf is one meter wide, and a larger one is 1.2 meters wide, it is 0.2 meters (0.2 times) larger. Again, if one shelf is 1 meter wide, a 3-meter shelf is *two times* larger, that is, larger by a factor of two times its original size. Of course, the larger one is three times the size of the original.

When the ratio of magnitudes is large, such as 100, the difference between 99 and 100 is insignificant if that factor of 100 is just a rough estimate. Nikevich (talk) 16:21, 1 March 2009 (UTC)

No, the phrase is pretty standard, and it is not new by any means. The correct interpretation of "Bob's dinner is 3 times smaller than mine" is "Bob's Dinner = My Dinner / 3". explanation
--128.86.151.126 (talk) 00:52, 4 November 2009 (UTC)

Hygroscopic vs. Hydrophobic

The original reading is correct:

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 skin.

Hydrophobic (water fearing) substances do not act as a desiccant or dry out your skin. Silica gel, a colloidal form of silica is extremely adsorbent (given enough time). Waxes and oils are examples of a hydrophobic substances that won't dry out your skin but keep moisture in. --Dgroseth (talk) 00:23, 18 July 2009 (UTC)