2002
by
William T. Wood
INTRODUCTION
My buddy, Richard Reed, said aerogels were amazing, and would make a very good science fair project. Late in December of 2001 I decided to start. I got on the internet, searched Google, and found email addresses of researchers and companies. I also looked at and downloaded web pages. I began to send email to as many different sources as I could, seeking help, information, and samples.
As time went by, I found that aerogels are truly amazing. While I read many marvelous tales about them, I wondered what they were really like. With some samples promised, I decided on the following experiments:
1. They say aerogels are so strong a block the size of a man could hold up a whole car. How much weight could a block one square foot in top surface hold up? I could never get a big block, but I could put known weight on a small sample and calculate the weight for a big sample from there.
2. Aerogels are also very fragile. If even weight is not put on them they crack, flake and break. How easy is it to break my samples? We would see in many ways.
3. Aerogels are very light weight. How much do samples of a measured size weigh, and how does that weight compare with figures commonly quoted? I would measure samples and weigh them.
4. It seemed to me that most people did not know anything about aerogels. Was that true? I would survey dozens of people with a variety of ages, education levels, and jobs to discover what knowledge they would have about aerogels, and whether education or jobs made a difference.
5 Aerogels are said to be good insulators. I received a sample of flexible aerogel insulation 1/8th of an inch thick. How well would it shield my hand from freezing ice or from the heat of a burner element after the gas was turned off?
6. Aerogels are expensive. Richard Reed bought me a small sample that, with shipping and tax, cost $17.50. How do their prices compare to expensive things like gold? What are the prices for some real products? Could the prices become much less? I would try to find out.
7. Aerogels come in hydrophilic and hydrophobic forms. What does water, oil, and crazy glue do to both kinds? Can you draw on an aerogel? With what?
8. Can a solid chunk protect from a flame like in the pictures?
BACKGROUND
Aerogels have never been found, and are not known to occur, in nature.1 They were first created by physicist, Steven S. Kistler, of the College of the Pacific in 1931.2 An aerogel is any gel in which the liquid has been replaced by air without the solid part shrinking.
Jello is a gel made from gelatin and water (with added sugar and flavoring, Aerogels have been made from gelatin as long ago as the early research.3 If gels are allowed to dry naturally, as the water evaporates the rest of the water inside pulls the gelatin together with strong force against the tiny threads of gelatin. In my experiments to illustrate this force, I found out that two strips of plastic wet with water would cling together as you pulled the top ends apart.
I also showed that a small rod like a pencil slowly lifted straight out of water would also lift up some water that was clinging to it to a height of 5mm.4 The result in aerogels is a dried or thickened mass that cracks and breaks as it becomes harder.
I made a gel from raspberry Jello. I took a sample that filled a plastic lid 2-1/2" by3/4" and filled it full of the thickened Jello. I let it set out to dry. It shrunk down to1/8th inch.5
Aerogels hold the world records as the solid with the lowest conductivity, lowest solid density, the highest porosity, the highest surface area, and highest dielectric constant.6 I don't know what all these words mean, but they do prove aerogels are unusual.
I downloaded dozens of pages from the internet that I have included in my report. I want to thank Aspen Aerogels, Inc 184 Cedar Hill Street, Marloorough, MA 01752 for most graciously supplying me samples of their blankets, hydrophobic monolithic chunks, and aerogel granules. These were the basis of many of my experiments, and they were used to introduce people to aerogels while I did my survey. I also want to thank Bouvard Hosticka at the University of Virginia for a very generous sample of hydrophillic silica aerogel. I photographed this sample, which was two large halves at shipping and was broken into dozens of fragments on receipt. These samples made the best display pieces to show people, and were necessary to demonstrate the effects of water on hydrophillic aerogels. Special thanks go to my friend, Richard Reed, who suggested aerogels as my project, let me use his computer and internet connection, helped decide which pages might be most interesting, answered phone calls about the project that came in while I was at school, and suggested experiments for my project. He helped me say things correctly in the writing. .He also took the photographs. He bought me my only purchased aerogel sample. He also gathered information a child could not have collected about aerogel pricing.
A Special Note
At first it was my plan to gather all the facts I could about aerogels and present them, with as many samples as I could to educate a very uninformed public about aerogels. However, this year the local policy changed, forcing me to do some experiments on a simple hypothesis. They suggested a wide range of trivial and well-known topics. I then thought I might explore whether aerogels were ready to be a big success. I did not have time to do this. So I settled on discovering, by experiments, the things I could, and that I believed from the things I read. I was supposed to choose and answer a single question with a single variable. I chose a broader question to advance the scientific knowledge of my local community. So I had many sub-questions with different variables in each one. I hope the results prove more useful than a single small fact about aerogels.
I object to restricting projects as was done this year. The first step in the scientific method is to gather and arrange information. My project would have been much more useful if I could have stuck with that objective. Many sciences, and the scientific method associated with them, deal entirely with the collection and classification of information. Paleontology, for example, consists entirely in gathering information and artifacts and arranging them into meaningful groups. I should have the option of a similar scientific approach in my science fair project.
EXPERIMENTS
Experiment #1
Aerogels are reportedly very strong. Reports say that a one pound chunk could hold up a car, as in this artist's picture.7 I have some aerogel samples. Would one of my samples be able to hold up a car?
The first thing to know is that silica aerogels are very fragile and also very brittle. If you try to pick one up by a corner, it will surely break. If you try to pick it up with two fingers at the sides it will probably break or crack until you get the knack of it.8
However, if you apply even pressure on two flat surfaces and squeeze them together they can stand a lot of pressure. I found a small sample among my pieces broken off of the large hydrophilic aerogel. It's smaller surface measured about one square centimeters. It could have been slightly more or less, since the edges were not square or cleanly cut. The top and bottom were both flat and parallel as closely as I could determine without risking breakage.
I decided that a CD box would make a good flat base, and that a 2 liter soda bottle would provide a small, flat lid larger than the top of the aerogel. It would also allow me to adjust the weight if necessary to find the point just below breakage.
I chose a binary method to test the weight in the least number of moves. I went for broke on the first test, and filled the bottle to the same level as a new soda. This would guarantee two liters, which weighs two kilograms, or 4.4 pounds. The weight is a bit higher because of the bottle, which I did not weigh.
Very carefully, to keep the pressure even, I lowered the soda bottle onto the aerogel. It took the whole weight. I carefully removed it and inspected the aerogel. It was OK. I had my friend, Richard Reed,. photograph me. He examined the aerogel to prove that it was not cracked or broken.
I wanted to know how much weight a square foot of aerogel could hold up. Richard has a bunch of unit converter programs on his computer. Quick Convert has a function to change between square centimeters and square feet. I put in one square foot and the answer was 929.03 square centimeters. I used the Windows Calculator program to multiply that times 4.4 pounds. The answer is 4087,732 pounds. One square foot of my aerogel would hold up a fairly big car.
Experiment #2
This experiment does itself. When I got the sample from the University of Virginia the letter said it left there in two halves. When it arrived it had two fairly large pieces and dozens of small ones with hundreds of tidbits.
Aerogels of this type are extremely fragile. When I did the survey I started out with two big chunks with a top surface of about 24.5 square centimeters. After I asked if they had ever seen an aerogel, I asked if they wanted to see one. This made my buddy, Richard, mad, because everyone said yes, and nearly everyone wanted to touch it. Whenever they did, SNAP! I came home with one medium sample and a lot of little ones.
Handling the aerogels for other experiments, I have broken some. Doing some of the tests has caused samples to break
Experiment #3
When I went to Valley Plaza, where I conducted most of my survey, I found a jeweler who was willing to let me weigh my 24.5 cubic centimeter sample and to be photographed doing it.
My sample weighed 1.4 grams. I was told that my aerogel weighed .08 grams to the cubic centimeter. However, using Windows Calculator I found that 1.4/24.5 is only 0,05714 grams to the cubic centimeter. Quick Convert reports that there are 3785.41 cubic centimeters in a gallon. Windows Calculator, using those numbers, says a gallon will weigh about 216.31 grams. Quick Convert says that is 0.48 pounds.
When people talk about aerogels being light weight they often quote the weight of the very lightest ever made. That is .003 grams for a cubic centimeter. That is nineteen times lighter than my sample according to Windows Calculator
Experiment #4
For this experiment I mentioned aerogels to some people. My teacher, for example, had never heard of them. Neither had other people I met. I decided to take a sample of the people in Bakersfield to see how many of them had heard of Aerogels. To find out if I had a general sample, I asked 6 questions: age, sex, education, job, ever heard of aerogels, and ever seen an aerogel. I got 77 responses from people on the street, people at Valley Plaza, people on the bus, and even three people in radio and TV news. Only one person had heard of aerogels, and that one had never seen any.
I put the information in Microsoft Excel. Richard showed me how. I made graphs of a few results to show that my sample population was probably good. I used the chart wizard to make the graphs. Richard showed me what to do. Here is the Excel spreadsheet.
The people had a wide variety of jobs, though a lot were students. The only person who heard of aerogels was a homemaker. I think she must have seen a science update or something like that on one of the educational channels.
Experiment #5 and #8
Testing the insulating power of my samples was easy for the blankets and hard for the chunks. I have two samples of blankets. The first was 1/16" thick. The second was 1/8". When I got the first one I immediately wanted to test it in the fire because of the pictures and stories about aerogels protecting from torch flames.9 I put it over the kitchen gas stove. Oops, it started burning! I did not have the high temperature kind.
I took the thin blanket and wrapped an ice cube inside. I did not feel any cool. It looked like water would flow through this blanket, so I had the ice in a zipper bag.
Later I learned that the blanket was waterproof. I was afraid to test the heat, especially after the sample burned.
When I got the thicker sample, I was braver. I had Richard test the hot temperature. When he found it protected him, I tried it.
I also tried this sample in the fire. Like the first one, it burned. Aspen Aerogels makes three different blanket products. One is designed for only the very coldest conditions. The kind I received, called Polar Bear, is good for clothes and room temperature applications to keep heat or cold in or out. Pyrogel is the kind that can stand very high temperatures.
My monolithic aerogel chunks are all able to handle the stove flames. Nevertheless, I was not able to perform the same tests shown in the common photos of an aerogel keeping a flower from wilting or crayons from melting. In the crayon picture you can clearly see that they angle the flame so the hot air comes up over just one side and cool air is pulled across the crayons by the rising hot air on that one side. I was able to take a picture of the crayon on aerogel over a burner on my home stove, but it was centered over the flame, and by the time I had several pictures, the ends of the crayon had started melting. It did not melt where it sat on my aerogel, showing that the heat did not come through. The tip of the crayon was above the aerogel, and that part melted. From this I concluded that hot air curled up on all sides of the small aerogel piece and was sucked toward the middle as it rose. This was enough to start some air melt at the highest parts of the crayon.
When I heated my hydrophobic monolithic aerogel on the fire, it turned into hydrophilic.
Experiment #6
I could not do any hands on experiments for this. I can show samples of products for sale that I found on the Internet. The Hugo Boss jacket costs $690.00 in US dollars. I thought that might be because it is a high fashion company's product. But when Aspen Aerogels called my house and talked to Richard while I was at school, they reported that the aerogel blanket going into that jacket costs $50.00 a square foot in 10,000 square foot quantities. This means that most of the jacket's cost is the aerogel blanket insulation.
Airglass brand aerogel windows cost about $500 for a 20 inch square window. They have the insulating power of 15 double glass windows stacked together. But most people in America do not need that much insulation. The Airglass window costs about as much as those fifteen double glass windows put together.
Richard bought me a sample of aerogel from Mountain Skies astronomy gift shop. The initial price was $10.00. No quantity was quoted in the ad. When it came , we were disappointed. With shipping and handling, and sales tax, it cost $17.50. The pieces were tiny and very irregular in shape. We measured them at about 1/4 of a cubic centimeter if they were all put together.
They came in a plastic case with a magnifier lid, which might have been about a dollar of the cost. If I assume a $9.00 actual cost for the aerogel, and that the hydrophilic sample weighs a typical .08 gram per cubic centimeter, then Windows Calculator shows that there would be 50 such pieces in a gram. That makes the aerogel cost $450.00 for a gram. Quick Convert says there are 31.1 0 grams in a jewelry (Troy) ounce. Windows Calculator converts that to $13995.00 for an ounce, way way way more than gold.
Marketech Research sells a variety of aerogels in larger quantities.10 If I buy 10 grams of silica aerogel in one to two centimeter chunks, they cost $110. That makes the price about the same as gold. A solid chunk 2x2x.5" costs $200. At .08 grams per cc this chunk weighs a bit more than 2.5 grams, and would cost about 75.00 per gram. The price per ounce would be over $2,300. That is also way more than gold..
When Marketech called while I was at school, Richard asked for prices on one million chunks of that size. They quoted $2.50 each. That would make them cost about $30.00 per troy ounce, which is about 1/10 the price of gold.
There is a set of high fidelity speakers that use aerogel for the cones. One pair recently auctioned on ebay for $1250.00.11
PowerStor makes capacitors using aerogel.12 These are electrolytic, and come in cans like you find in electronic equipment. In this case, because the capacitor values are very high, the cost is in the same range as regular capacitors.
Experiment #7
The first aerogels were hydrophilic. That means they will soak up water, and the pull of the water, when it touches them makes the aerogel fall apart. Later they learned how to add things to the aerogel that makes them resist getting wet. These are called hydrophobic aerogels. I got samples of both kinds.
When I dropped a piece of hydrophilic aerogel in water, it turned white and soaked up the water. It became a regular, very soft gel again. The hydrophobic aerogel just floated on top of the water surface. It did not float in the water. Richard said that is because the surface tension of the water (the water clinging to itself) is greater than the weight of the aerogel pushing into it.
If you put a tiny drop of water on hydrophilic aerogel, it makes a white cloud. After a while that cloud dries into white powder that sticks together. You can carefully scrape out the powder and there will be a hole in the aerogel. The same thing happens with oil on both kinds of aerogel. Crazy glue does it too, but the glue hardens the powder an makes it hard or impossible to get out without breaking the aerogel.
Richard remembers something from many years ago that sold millions. They were called pet rocks. They had faces painted on them, and cost $5.00 each. He thinks a good sized aerogel chunk could be a pet cloud. But can you put a face on it?
I made a happy face by putting on a drop of water for each eye and the nose, and a bunch of little drops in a curved row for the mouth.. I looked at it with the white left in, but because the white was broken up and was almost loose powder, I lifted it out, and it gave the face a kind of ghost look, which is sorta neat..
Next I tried felt tip pens. I wanted to see if a stamp could put a face on the aerogel. I put the flat edge of a highlighter on the aerogel, and I could control how much it affected the aerogel by how long I left it there. This would be a good way to stamp aerogels. See the samples on my display for the results of these tests.
CONCLUSIONS
Aerogels are expensive to make, and that's why they cost a lot of money. This picture shows a pressure chamber used for making aerogels. It has to get very hot and very high pressure inside for it all to work.13 These conditions cause making aerogels to be slow14, so there has to be a lot of equipment to make very much at a time. Because of the high temperature, pressure, and the chemicals used, it can be dangerous. A plant exploded and was completely destroyed in 1984.15
Aspen Aerogel says they have a process for making it very quickly.16 They have won awards for that, and they say that by 2005 the world market will be $10,000,000,000.17 18 But in the same report, published in 2000, they say that by 2007 the projected world market will by $6.6 billion.19 It is impossible that the market would go down across that time, and so the Aspen projections sound more like hopeful guesses. In their advertising they add that these projections apply only with the inflow of large amounts of investment money.
A careers paper, with no interest in promoting aerogel, does not paint such a glowing picture. They say "Except for a few small areas [like NASA], silica aerogel, because of its high cost, is really a solution looking for a problem. The main market thrust is going to be in the carbon aerogel areas because those really have applications that are down to earth."20
On the other hand, my friend, Richard, disagrees with a NASA article that says "The strictly unscientific term for aerogel is 'pet cloud.' In the house of the future, aerogel will not replace other pets."21 He says, "Pet rocks did it a long time ago. The prices I heard for aerogel blocks is about the same when delivered to the store. And aerogels are also rare and unusual." I ask, would you invest $10.00 to have a smiling little pet on your coffee table that could keep conversation going for hours?
Footnote
As far back as December I was promised samples from Airglass and from the University of Oklahoma. They have not yet arrived, so I could not use their special properties for my experiments. The University of Oklahoma sample was especially important because instead of being fragile that aerogel is so strong you need a hammer to break it. It weighs half as much as balsa wood.22 That would make it valuable for model airplanes and other places balsa is used. I could not get information about it in time to explore its properties.
PowerStor capacitors are up to 4,000 times higher cqapacity than regular electrolytics. That makes new uses possible. Mattel toys that sit on a battery charging pack and then go use these capacitors instead of rechargeable batteries. They last much longer, and they hold enough charge to make them fun to play with according to a phone call received from Future Technologies and taken by Richard while I was at school.
There are new developments in aerogels almost every day. It could be that some of them will overcome aerogels' weaknesses and problems, and Aspen might wind up being too low in their guesses about how much aerogels will be sold in five years.
Bibliography
1. "Aerogel Research at LBL: From the Lab to the Marketplace" by Jeffery Kahn, Berkeley Lab Science Articles Archive, Summer 1991 (Pages pg. 17).
2. "Much Ado About Nothing", by Douglas Page, High Technology Careers Magazine, online Feature Presentation (Pages, pg. 8).
3. "A Brief History of Silica Aerogels", by Arlon Hunt and Michael Ayers, internet article from LBL (Pages, pg. 26).
4. Notes, pg. 5
5. Display Board
6. "Aerogel Super-Insulation", by Aspen Systems online information page (Uses, pg. 10)
7. AGPoster 1, University of Virginia, (Pages, pg 1)
8. "Silica Aerogels for Absorbing Kinetic Energy", Web Page, LBL (Uses, pg. 27)
9. Aspen Aerogels, Inc. Advertising, (Uses, pg. 45)
10. Aerogel Products Order Form, Marketech International, Web Page (Pages, pg. 37)
11. Ebay item search for aerogel*, (Pages, pg 64)
12. "PowerStor Aerogel Supercapacitors", Cooper Electronic Technologies, Web Page (Uses, pg. 39)
13. "How Silica Aerogels Are Made", Web Page, LBL (Pages, pg. 14)
14. Ibid. (Pages, pg. 13)
15. Op. Cit. #3, (Pages, pg. 26)
16. "Aspen Systems Aerogel Technology", "NASA Success Story, Web Page (Uses, pg. 34)
17. Ibid. (Uses, pg. 34)
18. "Low Cost Aerogels", Aspen Systems, Inc. (Uses, pg. 63)
19. Ibid. (Uses, pg. 47)
20. Op. Cit. #2, (Pages, pg. 7)
21. "The House of the Future?", Science@NASA, Web Page, (Uses, pg. 31)
22. "Nothing to It" by Phillip Ball, Nature, Science Update, Web Page, (Pages, pg. 23)