§1. Graduate school rankings and choosing an advisor [00:07]
Student: [Question about graduate schools in materials.]
The best school happens to be MIT, and there's a good story about that. At MIT, the physics department doesn't like to admit their own undergraduates to graduate school. Richard Feynman didn't get admitted to MIT for graduate school. He went to Princeton and then he ended up at Caltech and then he won a Nobel Prize. He didn't get admitted to physics because there are lots of other good physics departments, and the argument is, why shouldn't you go somewhere else and see the horizon somewhere else?
When I was department head, I would have department heads from other universities say "we encourage our best students to go to MIT, why don't you encourage your best students to come to our university?" And I couldn't say, "because you're second rate." But we really are number one. In the area of materials, in the area of engineering, they just came out with the undergraduate rankings in U.S. News and World Report. Back when I was department head in the late '90s, there were four different rankings of schools, and the materials department was the only one at MIT that came in number one in all four polls. I used to hammer the other department heads at engineering council and tell them, we're the only ones who came in number one. Mechanical engineering came in three out of four. There is a bigger gap in materials between us and the next best school.
Having said that: Northwestern has an excellent program. Colorado School of Mines actually never took the word metallurgy out of their title — neither did University of Nevada Reno, but they're sort of mining and metallurgy. Lehigh University is not bad in metals. Rensselaer Polytechnic's not bad. Berkeley's good in lots of things — Northwestern and Berkeley are in the top five anyway. Stanford, forget them — there's a bunch of electronic-materials-first people. They had one guy, Bill Nix, [I think they] still have him, he's about 85 and he is Mr. Mechanical Metallurgy in the country. But tell me who the next person is. So that's on video and that'll be out for the world to see — Tom Eagar's rankings.
You don't have to believe what I say. But when you go to graduate school, it really gets down in many cases not to what the best school is, but who's the best advisor. There are people at this institution that I would never work for. I won't name them on video, but if you come to me privately I would tell you.
§2. *Science* magazine on the environment and GDP [03:55]
Here are extra copies of everything we've handed out from day one, and my secretary has made enough of the two handouts for today. Everything is also on Stellar. Before we officially begin, here's a little culture for you. Out of Science magazine from August 22nd. Science is the magazine of the American Association for the Advancement of Science, and it's one of the few things I flip through every week. Every month I read National Geographic — I don't read it, I flip through, I like the pictures, ever since I was about six years old. The Economist I look through every week. And Science magazine.
Here's an article on boosting GDP growth by accounting for the environment. The thesis, written by some people from Cambridge Massachusetts and someone from Middlebury College of Vermont, is that they define gross external damages to the environment — the GED — and the cost of that on a national basis, and the environmentally adjusted value added, EVA. They conclude that between 1999 and 2008 the air pollution intensity of the U.S. economic output — the gross environmental damage divided by the gross domestic product — fell by one half, from 6.4 percent to 3.2 percent. Only economists could give you two significant figures on something that we know to half a significant figure, but anyway.
The aggregate gross environmental damage dropped from $589 billion to $351 billion, so that's good. Environmental value added went from about $8.5 trillion to $10.75 trillion. The gross domestic product went from $9 trillion to $11 trillion. Basically, in 2002 we actually added two and a half billion dollars to the gross national product through this. They're arguing that we've actually been doing better, and that represents about 0.02 percent better. It's not a lot, but two and a half billion dollars isn't nothing.
Their argument is that the cleaning up of the environment that we've been doing actually has a positive net economic benefit. People could shoot holes at this, but I'm sure these economists have done a lot to quantify and justify what they're saying. So being green is good business. That's just for culture.
§3. Productivity vs. competitiveness; value of materials [07:42]
I'm going to pass around the sign-in sheet — I now have 34 people on this. If your name's not on it, please check. My secretary wants to make a list of emails, so that if we have to blast the class with an email because I get hit by a truck and won't be there the next morning, you'll know. Next week I'll be lecturing Monday and Tuesday, Dr. Belmar will be Wednesday and Thursday, and I'll give you Friday off — it's actually a student holiday. In the old days it was Yom Kippur, but they don't say anything religious anymore.
What were the takeaways from last Monday? Productivity is everything now. Paul Krugman — anyone know who Paul Krugman is? He writes for the New York Times. He was an MIT graduate student, became a faculty member in economics, did a lot of good work, wrote some books to sort of counter the dean of the Sloan School, who was Lester Thurow at the time, back in the '80s and '90s. Then he went to [Princeton] and won the Nobel Prize. He's now at Columbia or somewhere, writing news stories. He used to say productivity isn't everything but it's nearly everything.
If you can shoot for one thing that's good in the world in terms of manufacturing, being the most productive is the best thing you can do, and over the long haul it's really good. We talked about steel — it went from one person-year per ton to about 20 minutes per ton. Three tons per person-hour. Materials usage changes over time. I gave you the Ashby plot — he goes back to 10,000 BC all the way up to 2020. It came out of a book in the 1980s, and he turns out to have been terribly wrong going forward. There's lots of debates about who said it, but prediction is very difficult, especially if it involves the future. It's always better to predict the past.
Different industries value materials differently. Over the life of a vehicle, a pound saved in the automotive business is worth two dollars; in the commercial airplane business, two hundred dollars; in the aerospace industry, twenty thousand dollars. [Tom shows a piece of the X-33 space plane liquid hydrogen tank.] This is part of the shell — it's one of my prized possessions. This is part of the X-33 space plane liquid hydrogen tank, cost twelve thousand dollars a pound to fabricate, nice and light.
[Tom passes around a turbine blade cross-section.] This is about a thirty-year-old turbine blade — it's been split, they cut filleting just for display. Pratt & Whitney gave me this. It has internal cooling passages. This is a single crystal. If this was a good blade it'd be worth six or seven thousand dollars. It's not much good when you cut it open. It's an electron-beam hole drilled at different angles, and we'll talk a little bit more about that.
On the other hand, we have railroads and shipping, where things are worth about 20 cents a pound to transport. [Tom shows a refrigerator hinge.] This is part of a Sub-Zero refrigerator. Anybody have a Sub-Zero refrigerator at home? Only cost $11,000. Nice refrigerator, keeps the lettuce crisp because it has separate humidity control top and bottom. My son has one — he bought a house that had one. That's the hinge — just plain old carbon steel. You can't spend very much on refrigerators. In fact General Electric just sold Appliance Park — anybody see that in the news earlier this week? Appliance Park, outside of Cincinnati Ohio, is General Electric's huge appliance manufacturing facility — they've had it for 40 or 50 years. They make Sears Kenmore, they make all kinds of brands, but it's all General Electric at that plant. General Electric essentially manufactures for buy by everybody else. So there's a wide range in the value of materials.
You don't think of aluminum as a new material in aircraft — we've been making aluminum aircraft since the 1940s. Actually the engine in the Wright Brothers' aircraft was an aluminum-copper alloy casting. They were using aluminum on the first flight. And certainly by the 1940s many of the military aircraft were mostly made out of aluminum. It was a big deal in the 1990s, only 20 years ago, when Audi came out with all-aluminum vehicles. Was that really a big deal? I could show you pictures of Andrew Mellon, of Carnegie Mellon Bank fame, in the 1930s with his all-aluminum Pierce-Arrow. He could have Pierce-Arrow build him an aluminum Pierce-Arrow because he was the investor for Alcoa. He made a lot of money off the aluminum business.
So it wasn't that we didn't know how to make aluminum automobiles. We didn't know how to make them cheaply. In fact we still don't know how to make an all-aluminum Ford Taurus. Actually we do know how to do it, we just can't afford to do it. Any fool can make an all-aluminum hundred-thousand-dollar car. Making a twenty-thousand-dollar all-aluminum car is a much bigger challenge.
Who can tell me, to finish up our economics lectures, the difference between productivity and competitiveness? If you don't know, it's okay — I went to a review committee about two or three years ago at the National Institute of Standards and Technology, which is in Gaithersburg Maryland. NIST is the Department of Commerce's laboratory. It's one of the best federal laboratories in the United States — we have over 700 federal laboratories and I consider NIST to be one of the top two or three. We were reviewing their manufacturing programs and they got up the first morning and told us that they are the laboratory for competitiveness in U.S. industry. After the talk I said, "do you mean competitiveness, or do you mean productivity?" "Oh no, we mean competitiveness." I said, "then I don't believe you," in front of all these people. That's typical me.
They said, "what do you mean?" I said, competitiveness means things like foreign exchange rates — you guys are interested in doing research on foreign exchange rates? How many yen to the dollar, how many euros to the dollar, is that what you're doing? Because competitiveness involves things like that — it involves all kinds of externalities. Productivity is how efficiently you can make something. How many dollars per pound, dollars per unit. Competitiveness has all these political, social, economic externalities. They maintained all through that morning and the break, when I tried to politick and say "you guys — are you sure?" — they still maintained when I left two days later that they were the United States laboratory doing research on competitiveness. All I could say when they asked me to draft my report was that they didn't understand competitiveness. So if you didn't understand the difference between productivity and competitiveness, that's fair. But you should know that there is a difference.
§4. Containers and the Achilles heel of each material [18:01]
Now, competition among materials. If I talk about containers for holding liquids — there's a liquid and there's a liquid, there's a liquid and there's a solid. [Tom lays out an array of containers.] If I look at different types of containers, I could think of about six of them, most of which we are still using. We make steel — they used to call them tin cans. Aluminum — there's a Sprite can right there. Glass — you can have a bottle of beer. Ceramic. Plastic. And composite — these are juice boxes. These are water bottles, plastic soda bottles. Which is the one that's hardly ever used anymore? It was actually the first one used.
Ceramic. What's the Achilles heel of ceramic as a container? Very brittle. It's also sort of heavy. You see thin-walled ceramic stoneware in museums now, but they're heavy. What's the Achilles heel of steel? It's true of everything I say good about steel — you can always throw it back at me and say, but it corrodes. The reason they had to make tin cans is they would take a very expensive element, tin, and put a very thin plating on the surface to give the steel any corrosion resistance. You put food in bare steel, you wouldn't want to eat it after a day, it'd be all rusty. Not that it would be harmful — iron oxide is non-toxic, they use it as the non-toxic control in rats when they do laboratory studies. You can breathe iron oxide, you can eat it. But it does corrode.
Aluminum — what's the Achilles heel of aluminum? It's more expensive than steel. It actually is one of the best — it doesn't corrode very much, that's why we make how many — a trillion aluminum cans each year? It's a material of choice for containers. Aluminum is the fifth most abundant element in the earth's crust, so there's no scarcity of aluminum. But it does take a lot of energy, and that's why it's three times the cost of steel — because it has six times the energy content. Aluminum is sometimes called canned electricity.
A couple of my associates just got back from Iceland, where Alcoa put in a great big aluminum plant. Why would you put a great big aluminum plant in Iceland? Because they have a lot of hydroelectric power, and you can't get it out of Iceland any other way. The whole aluminum industry had a tremendous problem 25 years ago because the former Soviet Union broke up. They were making a tremendous amount of aluminum, which they weren't really sharing with the rest of the world. They were making it in Siberia. They needed foreign exchange, so what was the way to get all their hydroelectric power out of Siberia? Make aluminum. So they flooded the world market, and all of a sudden Alcoa and Alcan and Péchiney — the French company, the big company started by the other founder of how to make aluminum cheaply back in the 1880s — and all the other aluminum companies started closing production facilities, because the Soviets flooded the market with cheap aluminum. Otherwise all that hydroelectric power was going to go down the river and into the ocean. There's an opportunity cost there. These are kind of externalities. But aluminum is a great material for storing things.
Glass — what's the Achilles heel of glass? It actually has two: it's heavy, like ceramic, and it's fragile like ceramic. But it still is a material of choice for some containers, like bottled beer. Why? It has low thermal conductivity, but the real thing is it doesn't react with the product. It doesn't change the taste. Less than any of these others — it's very non-reactive, very stable.
Plastic — what's the Achilles heel of plastic? It doesn't have any thermal capability. It also is expensive — it's lighter, even lighter than aluminum, but it's got twice the energy content per pound as steel. They make it thinner and thinner. They make how many trillion bottles out of plastic each year.
Composite — what do I mean by composite? Juice boxes — seven layers of material, plastic, aluminum foil. If you try to peel these things apart, you can't, they're bonded together. The Achilles heel is recyclability. You either burn them or you put them in a landfill, that's it. You cannot recycle those materials other than to burn them up or bury them. So juice boxes are environmentally not so hot. One advantage: you can make them rectangular, and you can stack them close together, you don't have a lot of air in between.
The one that came first in society was ceramic. Second was glass. Third was steel. Aluminum came fourth, plastic came fifth, and composites came sixth. There's the rank ordering chronologically. Steel goes back to the 1880s. There's an MIT person, Samuel Prescott — anybody know who Samuel Prescott is? If you walk from Building 8 to Building 16, I think there's a big placard there that everybody ignores. It talks about Samuel Prescott. He was one of the guys who perfected canning of foods in the 1880s. When I was a student, MIT had a food nutrition department. He got killed by a provost who didn't make president because he killed this department without bothering to tell them he was going to do it. He was sort of John Deutch — a loose cannon, later head of the CIA.
Steel goes back 125 years. Aluminum as a container material goes back to probably the 1930s. Plastics, really the last 30 years is when it's big — we had them probably 40-50 years ago — and composites for the last 25 years or so. If you plotted the different materials over time, we are in this age of exploding numbers of materials and choices, which is why I can teach a course on materials selection. If I was teaching this course in 5000 BC, I'd be telling you about ceramics, maybe glass, and certainly stone. The choices were not so great. Now we have all kinds of choices, and people are always trying to up one another. The aluminum cans are a lot thinner today than they were before. When you pop this and take the pressure out, all of a sudden it becomes almost as flimsy as a plastic water bottle. [Tom holds up a juice box.] This is a composite, by the way — I just didn't have a juice box.
§5. Cost as the number-one driver; the Westbrook plot [27:12]
Beyond externalities, which may be the deciding factors in selection of a material — [Tom holds up a broken plastic specimen.] I broke this at the end of class. This is a piece of plastic — if you want you can fit it back together. It broke down here at the stress concentration where it changes width. It also broke with what we call a shear lip — a negative shear lip here and a positive shear lip here. It's a brittle material. You can tell it's a brittle material because you can put it back together without lots of space in between.
What is the number one driver, when we get to technology of materials, in our selection of material? You might say, well, this isn't a technological thing — it's cost. [Tom locates a chart.] This is out of the Materials Research for the 21st Century paper. This is not my plot, this is a 1962 plot by Jack Westbrook, who was an MIT grad of this department, went off to General Electric Research, and he's now retired somewhere in New England. Jack was looking at structural materials for General Electric and trying to give a big overview of what would be the structural materials for the future. He put together this plot in pounds per year versus dollars per pound. This is in 1962 dollars and pounds.
What's number one? Stone, cement, wood, brick, carbon steel — these are up here. Alloy steel is down here. Rubber, polyethylene, aluminum right here. This is a log scale, so yes, it's a factor of 50 difference between carbon steel and aluminum in volume. But steel's nothing compared to stone. Actually cement has passed steel in tonnage since 1962, and there are some reasons for that having to do with the third world.
Come down here to a structural material — diamond is a structural material. [Tom passes a diamond pad around.] This is a pad conditioner. If you're going to make semiconductors and you lay down different layers, after a while you've laid down different layers of everything and done etching, and the thing is not flat anymore. You need to planarize the semiconductor, so you take one of these diamond pads and you grind away some of the silicon that you just deposited with the copper and everything else.
[Tom shows a brazed diamond tool.] These are man-made diamonds, not natural diamonds. Man-made diamonds are better structurally than natural diamonds. We don't really have a shortage of diamonds in the world. Diamonds are expensive — anybody know why they're expensive? It's an externality thing. Most people want them to be expensive — the people who sell them. The people who buy them think they'd like them to be cheaper, but no, they don't really — they want them to be exclusive. De Beers has a world monopoly on diamonds. They have vaults in London full of diamonds, but they only let them out at a certain rate, because they've done all the economic studies of how to get the maximum profit. With enough supply they'd drop the price and De Beers would make less money. So De Beers is controlling the diamond market. They were really concerned when the Soviet Union broke up because the Soviet Union has some pretty good resources for diamonds. But they couldn't do much because people just steal them — they're too small and too easy to steal. Man-made diamonds are actually stronger structurally because they don't have the defects that natural diamonds do.
Anybody know the four C's of diamonds? Cut, carat, clarity, and — color. Carat is how big it is. Cut is how well they make the facets — if they kind of missed it, it doesn't sparkle as much. Clarity is how many pores and inclusions, all those other things that materials scientists know about. Color is the fourth. So diamonds are a structural material and they're pretty pricey. This plot bends over probably because of De Beers — you'd probably be down here automatically to be cheaper if we didn't have the externality of De Beers. The interesting thing about this plot is the iso-market-size lines.
I never have been able to quite reproduce this plot over the last 10 or 15 years, but the usage slope is steeper than the iso-market slope. What does that mean in the long term? Productivity is almost everything according to Krugman — Tom Eagar, it's everything, because I don't understand the "almost." If you can reduce your cost by a factor of two, you will increase your volume of sales in the long run by a factor of four, if you look at these slopes. Your market just became twice as big, if you can cut your cost by half. So productivity is worth something in the long run. In the short run it can do you damage.
In the short run, I told you the story about the worldwide steel industry. Their productivity shot up from the 1960s into the 1990s by a factor of six or seven, and their employment went down. When you're eating 600 million tons of steel a year, you can't convince people to eat twice as much. So you end up with an oversupply. You get into these other externalities which have to do with competitiveness, which I don't know anything about, but I know it's important. All the gurus on Wall Street said the steel industry is dying. Well, who's dying, you idiots? It was a wonderful business. And this guy in India, [Lakshmi] Mittal, goes around buying up steel companies for a song, because everybody says oh, the industry's dead.
Ned Thomas, who was my associate head and a polymer guy the whole time I was department head — he'd say, oh, metallurgy's dead. When Chris Schuh became a young faculty member here 14 years ago, I said, what's your specialty? He says, I'm a metallurgist. I said, oh, don't say that, the Dean will just hate that. Because people like Ned Thomas — idiots like Ned Thomas, I said that on tape — he's Dean at Rice University now, that was MIT's gain and Rice's loss when he left here to go to Rice. He thought that steel was dead, and he used to go around preaching this. Was he right? No, he was wrong. Any idiot who thinks about it would have known he was wrong. I told him he was wrong. He didn't like that.
I wrote the "Future of Metals" paper. It turns out the people in the steel industries were being beat up so badly by all the people in Wall Street, that when I wrote that paper in the early '90s they asked me at U.S. Steel Research to come and give my talk. I was the first outside person to give this type of lecture — it was always internal people, which says something about the ingrown, inbred, not-invented-here nature of U.S. Steel Research. I gave this talk about why steel was important. I thought, why do I have to go to U.S. Steel Research to tell them why steel is an important material? About two years later I was invited to the big conclave of the American Iron and Steel Institute — steel company presidents — down in Orlando. I'd never been to a place like this before. This was a gated resort center, palatial. Golf course right there. This is where the presidents of the American Iron and Steel companies would go to confer with each other — to collude, I mean, no, it's illegal. I had to give a talk on the future of metals. I thought, this really is silly, that I'm a professor at MIT and I have to go talk to the presidents of the U.S. steel companies to tell them why steel is an important material. But it's a true story. At that point it reinforced why I decided early in my career that it was time to get out of the steel industry.
§6. *Out of the Fiery Furnace*: the British wood crisis [38:13]
Let me give you a history lesson. I mentioned before Out of the Fiery Furnace — this is a PBS special. I'll read some of it to you. The problem was the shortage of wood. The effects were felt all over Europe, but the first country to reach crisis over the shortage of wood and charcoal was Britain, for two main reasons. They had limited area on an island. They also had a fairly robust economy, and there were two uses of wood: to make iron — you needed charcoal to run your cast iron furnaces, to make gun barrels and cannons — and to make ships of the line.
The iron industry grew, and it generated not only trade but conflict. The forests of Britain had long been admired for their most celebrated inhabitants — slow-growing and long-lived, these were the mighty oaks. For centuries they had provided the wooden walls of old England, and the castles. The Royal Dockyard was in Portsmouth. To make the H.M.S. Victory, Nelson's flagship at Trafalgar, took 2,100 tons of oak — and that's the final product, it probably took twice that — and that's just what went into the ship. It probably took two or three times that for all the shavings you had to cut away to make things the right shape. A whole forest. So the two uses of oak were in conflict — to make charcoal and to make ships. And now a third industry came along — glass-making. To make glass you need a very clean source of fuel, which means you need more charcoal — you need to cut down more forests.
I told you about how Saugus Ironworks came into being. In 1558 a law was passed — this is before Saugus Ironworks, before the 1600s — forbidding the felling of trees to make coals for the burning of iron, but the Weald of Kent and Sussex was exempted. What's the Weald of Kent and Sussex? That's where the big forests were, with the big trees. So the politicians haven't changed over four or five hundred years — they pass a law and then they exempt what they're really trying to protect. And still the price would continue to climb. In 1559 a writer complained that the price had risen from a penny to two shillings, by reason of the iron mills. The shortage of wood was so serious that a further act was passed forbidding the felling of trees within 22 miles of the Thames River, within four miles of the great forest of the Weald, and within three miles of the coastline anywhere. Because those big trees — they didn't have big tractor-trailers and big interstate highways to bring them down the roads. They had to carry those by horse and mule and oxen.
The decree effectively wiped out iron-making industries in the Weald. By 1615 England was facing an energy crisis. A royal proclamation that year lamented the disappearance of the kind of wood "which is not only great and large in height and bulk but hath also that toughness of heart, as it is not subject to rive and cleave, and therefore of excellent use for shipping." So even then they knew about the difference between strength and toughness. We lost that knowledge for about 350 years — we're going to talk about that today. That was 1615 they were talking about that. What did they do in the early 1620s? They came and built Saugus Ironworks, because we had lots of trees. So things have not changed that much over the years.
Until they actually started picking up coal. [Tom shows a piece of anthracite.] There's a piece of coal from the MIT forge — that's anthracite, that's good coal. The kind we don't have much of, but it burns very clean, very low volatiles. Basically they started picking up sea coal — sea coal is when a coal seam comes up to the ocean, exposing it, and the coal is light, it would float, and get washed up on the beach. So you had people walking up and down the beach picking up coal. Then they decided they'd dig into some of those seams, and they got deeper, and they started getting water in because they went below the water table. So they had to build pumps.
There was a guy named James Watt who basically started studying the efficiency of pumps, for all you mechanical-engineering types. He wanted to know — because the owners of the coal mines wanted to know — whether they were spending more money on the pumps to get the water out than the coal they're bringing out. What's your efficiency factor? This was the beginning of thermodynamics. They call it the "revolution of necessity." Because they didn't have any wood, they went to coal. Because they had to mine coal efficiently and be productive about it — productivity again — they had to have water pumps. Because they had water pumps they had to understand the thermodynamics of engines. I don't know if I follow all that, but it's a nice story, and it made a good PBS special.
§7. Tonnage structural materials and the periodic table [44:03]
There are a number of structural materials. But the real tonnage structural materials — the ones that are a billion tons or more a year — stone, steel, that's about it. Here they are in the periodic table, highlighted in yellow. It's not very much of the periodic table that we really use for structural materials, if you're talking billion-ton quantities per year. There's carbon, that's called wood. There's silicon, that's called stone. There's aluminum, which is stone — it doesn't quite make it in the metals category for a billion tons a year, but it's there because it's part of stone. Iron is a billion tons. Calcium and magnesium, that's called cement. And that's it — count them on a little more than one hand.
§8. Functional materials: silicon, sapphire, magnets, turbine blades [45:05]
How valuable is all this stuff? [Tom shows a polycrystalline silicon sample.] This is polycrystalline silicon, heated and cooled over a six-week period in a furnace to make very large grain size. They make a boule of it that's about this big, and they cut it up into little chunks and make solar cells out of it. All this technology was developed right here in New Hampshire, by a company. They make the equipment, and they sold several hundred of these machines to China, because the government of China decided to invest 30 billion dollars in solar cell technology. That's not structural material, that's a functional material. Once you saturated China with the equipment, that's going to cause them to knock our socks off in competitiveness. Right now all the solar cell companies in the United States are going out of business.
[Tom shows a sapphire sample.] That's sapphire — aluminum oxide, just another form of aluminum oxide, fifth most abundant element in the earth's crust. The silicon is done at 1600 °C; sapphire is done at 2100 °C — it gets a little hotter, it's a bigger furnace. They make a boule about this big, which is worth about a hundred thousand dollars, and they cut it up into little substrates, just like the silicon for semiconductors. Anybody know what those Al₂O₃ sapphire substrates are used for? LEDs. Every little LED has a little piece of sapphire. They also use sapphire — [Tom indicates a watch face.] this is sapphire, that watch face. They were going to bring out the iPhone 6 with a sapphire cover, and they haven't done it yet, it's just a little too pricey to get something that big in sapphire. But it won't scratch. Why? Aluminum oxide, also known as corundum, is right below diamond on the hardness scale. Super hard, scratch resistant — it'll scratch almost anything else.
Most of you haven't even thought why your watches don't scratch. In the '50s and '60s, if I had a watch, it would get scratched up because it was glass, and it would break. They switched to sapphire. Sapphire is actually pretty cheap. That little chunk of sapphire, if you weren't going to make it into a bunch of LED substrates, is probably worth a dollar or two. All you have to do is melt it and cool it over about a two-month period — you get big grain size.
So there is a difference between structural materials, which I want to talk about in this course — this is a long introduction — and functional materials. Structural materials are usually huge volumes. That makes them different than silicon boules for solar cells, or single-crystal silicon for semiconductor chips, or sapphire boules to make LED lighting chips. Those are functional materials — they have certain properties: coefficient of thermal expansion in the case of sapphire, scratch resistance in terms of sapphire for watch faces. Structural materials mostly just need to have mechanical properties — that's why a number of people in here are mechanical engineers, you're interested in structural materials. Structural materials are still important, in spite of what Wall Street or the Wall Street Journal think. Large volumes, millions of tons. Tensile, compressive, shear, creep, corrosion, ductility, toughness, fatigue.
Functional materials, on the other hand, have every type of property you can think of. Chemical, electrical, thermal, optical. And then you start putting properties together, like piezoelectric, which is mechanical and electrical. Or magnetothermic, or thermoelectric, or electrochemical. There are a host of functional materials, and we always hear about these things — Moore's Law and silicon — where the functionality growth has been tremendous.
[Tom shows optical fibers.] This is optical fibers. This was put together by Bell Labs 25 years ago — they showed the optical loss in decibels per kilometer. Egyptian glass was sort of green and smoky. Phoenicians did a better job by a couple orders of magnitude in transmissivity of light. Optical glass by the time of Leeuwenhoek — you could actually look through them and wear glasses. Then in the 1960s, glass fibers. We go here over eight orders of magnitude in transmissivity, and so now we can have light going down optical fibers most of the way across the ocean.
We can look at magnetic properties — I already passed around my magnets. This came out of a book created by Professor Flemings, when he was head of the department called Materials Science and Engineering, in the 1990s — this book came out around 1991. This is the BH product, the magnetic field squared. Here's your samarium cobalt magnet, neodymium iron boron's way up here above 40. Tremendous growth.
What does it mean? If I look at the old Alnico magnets from the 1930s, in order to have a certain magnetization — this is a thousand gauss at five millimeters from the pole face — you have to have eleven, twelve cubic centimeters of Alnico. Alnico 9 is a little better. You get up to neodymium iron boron — you never see them as big fat long magnets, because you don't need it geometrically. You have a drop of a factor of 50 or so in volume. So now all of your motors and things like that — when the Sony Walkman first came out in the 1980s, he had changed the batteries about every two or three hours. Now who would listen to an MP3 player if the battery lasted two or three hours? You get lots of time out of these things now.
§9. Turbine blade alloys and the GTD-111 patent story [53:06]
This is actually a structural material — the firing temperature of engines. I've got my turbine blade going around there somewhere. This is firing temperature versus time — the higher the temperature, the more efficient the engine. These are the materials capabilities. Here's an interesting one, GTD-111. [Tom shows a broken fan blade.] Here's a broken GTD-111 fan blade. This is directionally solidified GTD-111. General Electric came up with this alloy in the 1980s — it was an improved alloy. Then we got single-crystal blades like I'm passing around. The firing temperature of the engine goes up. But finally they couldn't get any better until they went to air cooling — those air passages through that blade — and you had a tremendous jump.
Every 50 degrees here is two billion dollars a year in fuel savings for the airlines. So there's a lot of impetus to come up with better alloys. But we've sort of hit a brick wall. Back in the 1950s, Nick Grant — he was a professor here, he's the one who taught me creep and high-temperature materials when I was a student. He was one of the guys helping to develop these alloys. They're graduates of this department, or assistant professors who went off to [Pratt &] Whitney or General Electric and developed these alloys. But they sort of ran out of steam, literally.
GTD-111 is a very interesting material — there's an interesting externality about it. When General Electric first came out with it, the composition just wasn't patentable, so General Electric didn't patent it. However, in about 1986 they filed a patent for a heat treatment of it that gave it the best properties. The patent office refused it. In the meantime, everybody else started using it — it was one of the best alloys. By 1997 or so, everybody had incorporated this GTD-111. This is in land-based turbines — that turbine blade is a little heavy to fly. They incorporated it in all kinds of turbine designs, and lo and behold, 20 years after they filed for this patent — or 15 years — the patent office finally allows this heat treatment option, and everyone else is now infringing on General Electric's patent.
There was a big scramble to figure out what to do, because you designed your whole turbine around the properties of this material, and now General Electric is going to be asking you for royalties. I had a student do a master's thesis on this, for a company that refurbishes engines. We found that if you did hot isostatic pressing, you could take an old blade and rejuvenate it with a fancy heat treatment. So it didn't become as big a problem as some people thought, but when that patent first issued, there were a lot of scared competitors to General Electric, because they'd been using this alloy for 15 years. I'll be here tomorrow, and I'm now only about one full class, or class and a quarter, behind. But it doesn't really matter.