And they are incredibly rare and labor intensive to mine.
So why not just make them at home?
All it takes is seven or so months, a fume hood, some ethyl alcohol (purer is better), tetraethyl orthosilicate, ammonium hydroxide, a stirrer, water bath, hot plate, resin, a vacuum chamber, and apparently infinite patience.
I apologize for the narration of The Mat Sci Guy. His voice certainly lacks those nice, pear-shaped tones that are so valuable on the radio - or maybe he just needs a better microphone or a decongestant or processing software.
But...his content is interesting and educational, well laid out and thoroughly researched, so I recommend watching the video but maybe not showing it in class.
Today's video sees him exploring the formation, properties, and applications of aerogels in their various forms.
I'm thrilled that I know something about sol-gel chemistry from a summer of research I did at Miami University some twenty five years ago. I wasn't making aerogels, but I did spend the summer making sol-gels and exploring their applications in chromatography columns.
I also have a little experience with aerogels...or at least I did until my favorite coworker shattered my large sample. Now I have multiple, smaller samples.
In the fall of 1995, Professor Arthur B Ellis of UWisconsin came to Wabash College - where I was then a senior chemistry major - and gave a presentation about LEDs. At the time I knew of LEDs as the little red or green light bulbs that were pretty much used as power indicators on electronic devices. I didn't - before his talk - have much of an idea how they worked or how important they would come to be in our world now twenty-five years later.
Coincidentally, Dr Ellis had just written Teaching General Chemistry: a materials science companion, a book that my cooperating teacher bought for me after my student teaching semester later that academic year and that I accidentally re-purchased twenty years or so later. (I realize now that I've told this story on the blog before.)
But I digress...I have come to realize that Dr Ellis's lecture at Wabash really laid out the chemistry of LEDs marvelously well because I watched the above video - showing the LEDs and solar panels are of a kind - and the below video - in which Steve Mould explains the science of LEDs and how they turn electricity into light (and the reverse in solar panels) - and realized that I already knew that information...even down to the P- and N-type semiconductor information.
I've never had a chance to thank Dr Ellis for his lecture, so maybe - if I'm lucky - he'll come across one of these blog posts and realize that he's appreciated.
This might be my prize material science possession. It's three pieces of silicon.
The Lego figure is just there to show some scale. I figure everybody knows how big a Lego minifigure is, especially Margaret Hamilton.
These were sitting in the back room of the original Princeton High School building before it was torn down. During the last year in the building - as we transitioned across the street - we were doing a lot of paring down, preparing to move what we needed and leave the rest behind for a public auction. This was on the shelf of another science teacher's storage room and was clearly bound for the auction. They didn't know what it was, didn't want it, didn't think it had much value.
And I grabbed it with great gusto.
I wasn't letting this one go because I know I'll likely never get another chance at it.
You can see the process of producing mono-crystalline silicon in videos I've posted before. The silicon has to be refined before this (something I got to see done outside of Butte, Montana - but where they didn't allow any photos, sadly). That results in something like the rough chunk in the front, left of the photo. This chunk is roughly small-fist sized.
That chunk - and a bunch more like it - is melted and a single silicon crystal is lowered into the rotating vat of molten silicon. The single crystal is slowly raised from the surface of the molten silicon, rotating in one direction while the vat is rotated in the opposite direction. If the conditions are just right, an single crystal of silicon is raised from the vat. That's what the tower is in the photo above. The final product was likely taller and didn't end in a flat bottom layer but rather a second tapered end.
Check out the process from about 1:00 - 3:00 in the below video.
The tower (technically a pull of silicon) would then be sliced into flat wafers that would then be etched into computer chips.
As to how Princeton High School got the silicon tower and chunks...I'm not entirely sure.
I've heard from a couple of non-PHS teachers that Cincinnati had a silicon wafer production facility that shut down and donated silicon samples to local schools, but I haven't been able to track down any information about that donation. I did find information about two silicon wafer production facilities in the Cincinnati area. One was near Maineville, but that one closed down in 2010. That's too late to fit into our timeline. The other, now known as Milacron, produced silicon wafers in the 1970s-1990s ("by 1984, the Mill had become the world's largest supplier of this type of wafer.) While I don't have any proof, that fits the timeline of a possible donation to Princeton much better. So I'm assuming we have Milacron to thank for this donation.
I've written about aerogel before (and perpetually mention the demise of my one piece).
But I haven't shown a video that uses a FLIR camera (1:00) to show the heat zones as they insulate a chocolate bunny from a bunsen burner using aerogel, where they show the industrial process of making aerogel (5:25), or especially where you actually get to see a supercritical fluid through the window (6:25 - the absolute highlight for a teacher who used to teach phase diagrams in AP chemistry), or where you get to see a mid-process 'wet' aerogel filled with alcohol (4:50).
If you happen to follow both of my blogs, you might see this double posted because of that supercritical fluid bit.
Seriously, Rebecca, you'd have my heart if you bought me some new aerogel.
