MSE_F2016_03

Could be polycrystalline, unidirectionally solidified, or single crystal. Okay, and then you put a bond coat on, which is a porous spongy that has a lot — and if you listen to my welding lecture on solid state welding or solid state joining, adhesive bonding, you like a nice porous surface to bond to, to get mechanical interlocking. Well, they do the same thing, and so you grade the layer from let's call it single crystal to porous metal powder that's sintered on there, um, and maybe several layers to um vapor depositing the ceramic that gets down in those pores and sticks on, so hopefully it doesn't flake off. If it starts flaking off very badly you're going to lose your blade. But you can lose one or two blades and usually you don't lose the engine. You know, it's not good, it's expensive repair, but it's not good to lose an engine.

Okay, other questions? So where did you work? I worked at Virgin Galactic. Okay, I work on rock— So we do just the spray because we wouldn't want to spend $2 million for something that we were going to throw away after one use anyway, one use in over, you know, less than an hour's use, right? Or — well yeah, hopefully you're only using it for like three and a half minutes when it's using it. It's the four or five tests that you do to make sure that that's okay that get life. So we just do the spongy kind of white circ— Andra, I haven't ever worked on them but it's my understanding that cruise missile rocket motors are made out of carbon composites.

And speaking of carbon composites, here's a tube of carbon composite. [Tom produces a tube of carbon composite.] This was designed as a filter, I'll talk about that, but they make it out of carbon composites because the motor only has to last for two hours. It blows itself up at the end if it's successful, right? So this is a carbon composite that was made by Coke [Koch] Industries in the research project. Carbon has the best corrosion resistance of any material, okay. It's impervious to most metals, and this was going to be a way to recover precious metal catalysts from baths of sulfuric acid. So sulfuric acid won't touch it. Basically what they did is they would take a piece of — and you can see it has a surface sort of like woven fiber or woven cloth — it starts out as a polyacrylonitrile, which is just a polymer blend, and you wrap it around a mandrel as a cloth, plastic cloth. You stick it in a furnace at 1,000° centigrade and decompose the polyacrylonitrile to carbon. But it's not really good carbon until you basically eventually get it to about 2,000° centigrade and burn off everything except the carbon, and you end up with this. And that's how you make a carbon composite. And it has some directionality because you had the original fibers of plastic that — uh, so you can see the fiber shape. They also then put on the inside some nano powder to make a porous layer so they could grade and have a filter. They wanted to squirt the sulfuric acid with the catalyst inside, and have the sulfuric acid under pressure go out one way, and they'd recover the catalyst.

And there's a lot of applications for things like this. It turns out the largest — um, if you're a chemical engineer, the inorganic acids, the most widely used — this has nothing to do with structural materials, the filter does have to do with structural materials, but the most widely used acid is sulfuric acid, okay. Use it in lots of chemical plant applications, precursors, it's a catalyst for gasoline, okay, production of gasoline. Because the nice thing about sulfuric acid, it will absorb water very — it's very, uh, hydrophilic, okay, it loves water.

In fact, an example I used to do — I don't do it in class anymore, I did it in class once but never again. Um, if you take about one inch of table sugar and put it in a beaker about six inches tall, and you pour — now do this in a hood. I did it in the classroom down the hall once about twenty-five years ago. Um, I told the students to set this up because I had done it before, and I had done it in the hood in the lab, and I decided I wanted to do it in the classroom. And I said, then you take concentrated sulfuric acid and you pour about an inch of sulfuric acid on top of the sugar, so it's about a fifty-fifty split. Anybody know the composition of sucrose? C12 H22 O11. If I take the H2Os out, what am I left with? Carbon. It turns out sulfuric acid is a wonderful desiccant. It will strip all the H2Os out of here and leave carbon. And so if you do this you'll see the sugar — when you pour the sulfuric acid in, it turns a little gray, and then it gets blacker, forms kind of a black liquid, and then you see this big black mass that grows by about to about six inches high, you know, triples its volume. It also gives off sulfurous acid fumes.

So we canceled class about five minutes early that day. The classroom was a little — had a little odor to it anyway, pungent, I mean, no one died, I mean, it was that bad. And afterwards I went to the students — I said, I mean, I told the students set this up so I can do this in the classroom. And I come back the next day and there's like ten of these masses of carbon. They just thought this was so neat, they just — they were doing — and sugar's cheap, sulfuric acid you — and I went, I said, didn't you guys — did you guys have fumes come off? Oh yeah, it smelled terrible, we had to put the hood down, the cover down in the hood. Oh, well, okay. So next time I'll videotape and go to the class if I teach uh sophomore thermo again. Anyway.

But so sulfuric acid is the most common. The second most — or the most common organic acid is acetic acid. They make acetate, you know, polyacetate sheet and other things out of it. Turns out to make acetic acid, you take carbon monoxide, and carbon monoxide, you got to have some — I can't remember what the other — you can look it up on Google. Anyway, it's carbon monoxide and water or something, I don't remember. Anyway, you make acetic acid, but you have to have a catalyst which is either rhodium or iridium. And it turns out you're not really making acetic acid, you're making — as one chemical engineer told me, you're making a catalyst recovery unit. Because if you don't recover all of this fine powder catalyst of iridium or rhodium you lose your shirt. If you sell that with your acetic acid you're going to lose all your profit, because all your money is in the catalyst. So that's what that uh that carbon composite is.

Other questions? Okay then we'll get back to what we're supposed to be talking about. Um, so we had talked about aluminum being canned electricity, and then I mentioned last time that China has been in recent years, in the last six years, has increased their aluminum capacity by 250%. And the rest of the world has been increasing — this is the world and you can subtract China from that, but you can see the rest of the world's not going up that fast. Some of this is because Ford is now making an F-150 out of aluminum, and so people are saying oh we're going to start making aluminum automobiles, and we'll get to that in a little bit. But I have concluded that really China has decided they don't mind being the country that creates all the pollution and essentially is killing their own citizens with pollution and stuff. But they have lots of coal and they're going to export it, and the way they're going to export it is by selling aluminum dirt cheap on the world market, which is hurting a lot of the aluminum companies right now.

Okay so the new material is basically — uh another economic lesson — the principal monetary exchange product. Because really money has really little value, I mean, the old days, you know, thousands and thousands of years ago it was all barter, right. You got some firewood and I got some grain and we'll trade. But they came up with money as an easier exchange method. And the primary thing before 1870, people were working for food, okay. And at the time of the American Revolution, 97% of the American workforce was in agriculture. 97%. Only 3% were Ben Franklin and Thomas Jefferson and politicians. So we had 3% politicians and 97% farmers. Today we've reversed that, right. Um, but in any case, and then in 1870 to 1970, for about a hundred years, the primary material was steel. And that's because of Henry Bessemer in 1856 discovering a way to make steel in bulk, and Andrew Carnegie came along, became the richest man in the world. In constant dollars, richer than Bill Gates ever has been. Andrew Carnegie made more money than anybody else, okay, in his lifetime. And steel was the method of determining the world's economic value.

I remember in 1962, I was twelve years old, I don't remember much about it but I could read the paper. And President Kennedy stood down US Steel. US Steel wanted a 10% increase in the price of steel, and Kennedy says roll it back, we're not going to let you have it. And US Steel says we're a private company, go pound sand. They didn't actually use that phrase back in 1962, but they basically had this big fight in the world press. And at that time the US steel industry controlled the world market, because after World War II the United States had 75% of the world's steel making capacity, okay. Does anybody know why? They had bombed out all the competition. There's nothing better than having a war that's not on your property and bombing out all your competition. And these managers thought they were the brightest guys in the world, because they can compete with people who had plants that just had a hundred tons of bombs dropped on them. Oh, they're so bright, okay.

We have the same type of management today. Um, we have American managers who think they're so bright because they can beat the Europeans. Well, you can beat the French because the French have laws that don't allow you to hire anybody unless you're going to keep them on the payroll for thirty-five years until they retire. I mean the laws in France are such that they have no flexibility to hire other workers, to hire workers unless you want them for thirty-five years. Uh, there's things like that in Japan. Uh, we got to compete with people who decide they want 30% of their populace in agriculture for historical reasons, and so the price of rice in Japan is ten times the world market price. I remember when I lived in Japan, I thought, oh, what a wonderful gift, I'll bring in wild rice. The Japanese didn't have wild rice — at the time it wasn't cultivated, you could only get it from Minnesota or North Dakota, and the Indians would go out there and collect it, it grew wild, and no one had ever successfully cultivated it. They have, since, in the last ten years or so, fifteen years, but no one could cultivate wild rice. I was told, you're going to go to jail if you bring rice into Japan, okay. Why? It might have been black wild rice, but the Japanese, just like the Eskimos have something like fifty words for snow, the Japanese have about fifty words for rice, okay.

In fact they revere rice so much, and they revere the economic power of the United States. Um, do you know what the Japanese call the United States, aside from America? Beikoku, which means rice country, okay. If you look at the kanji, the bei is rice, koku means country, and bei means rice. Um, but the Japanese are very impressed with our economic production. So anyway, in '62 Kennedy forced US Steel to roll back prices. Some people in the steel industry would say that was the beginning of the decline. They didn't have enough profitability to add new capacity, uh, production capacity. That's really not why they went down, in my opinion, but that's another story.

Um, starting in the early '70s after the first oil crisis in '72, all of a sudden oil became the commodity, okay. Before that the Saudis could pump oil for $2 a barrel. I remember buying gasoline, or going with my parents back in the 50s and 60s, and gasoline was 24 cents a gallon at the pump, okay. And even until — I don't know if it's still true but even ten or fifteen years ago in Saudi Arabia I'm told you just pay a fixed price when you come fill up your car, you might pay a buck fifty to fill up your tank, okay. Because it's like they got more oil than they got water, okay. In fact water is more expensive than oil even in the United States today.

Um, so from 2000 to the present it's really energy. And it's not just oil, we have learned, whether it's solar or wind or coal or whatever — the energy is fungible. Um, we used to like to price everything on oil, but the world market really is trading on energy today, okay. And there's competition among the different types of energy. So what difference does this make? Well, it turns out if you are the country that sells in your monetary system, the price is based on, okay — when they say the oil price today is, I don't know what it is, $36 a barrel for Brent crude, they're quoting it in dollars per barrel, right. They're quoting gold in dollars per ounce. Because the dollar is the international standard for international marketing. Uh, if a country is having hyperinflation or something, what do — Argentina do — they'd make the dollar bill, the US dollar bill, their currency, okay. Because now it's pegged to a country that's considered to have strong economic stability.

Well, what does all that mean? Well when I lived in Japan in '84 and '85 it was 240 yen to the dollar. Anybody been to Japan recently, in the last twenty-five years? Yeah, what's the exchange rate? Yeah, it's 40% of what it was before. I mean, you know, a 10,000 yen, an ichiman note, 10,000 yen note, was a $40 bill, okay. Now it's a — uh, 100,000 — uh, it's a $100 bill, right. It's two and a half times as much. And what happened there? Well, the Japanese borrowed — loaned us money. They sold us Toyotas, they loaned us the money to buy the Toyotas, and also to bankrupt the Soviet Union in Star Wars, you know, in a military thing to bankrupt the Soviet Union. And today we're paying them back hundreds of billions of dollars, and we're paying them back at 40 cents on the dollar. Pretty good, huh? You borrow money at a dollar and you give them back the same amount of yen at 40 cents, okay, for every dollar you got.

Now, who are we doing this to today? What country? Yeah, China, exactly. Only China is holding the line, they're going to hold an artificial price on the international exchange rate for their renminbi, or yuan, or whatever. Renminbi is the foreign version and yuan is the internal version of Chinese money, or whatever. And we're going to end up paying them back at 20 cents on the dollar. Because someday the Chinese government will not be — they're going to find they cannot eat dollars. You eat food, you wear clothes, you buy computers — or, well, maybe we buy the computers from them, well, nonetheless, but we design the computers for them, okay. But we're going to pay them back at 20 cents on the dollar. How much cash in dollars does the Chinese government have right now? $2 trillion, okay. And they're getting to the point where they're getting tired of dollars.

And as long as we are the country that determines the price of the monetary exchange — and certainly it's in energy right now, is priced in dollars — when these other countries have inflation or deflation, but when they have inflation in their cases we get a discount on what we borrow from them. So you hear about the exchange rates and all this other stuff and how the United States is always got a bad balance of trade. Yeah, it's because we're only going to pay you back at 20 or 40 cents on the dollar. Not a bad deal. I mean, I wish I could go to the bank and do that but I can't. This is international finance, okay. Uh, what else do I want to say about that? Something else I wanted to say, I don't remember. Okay, well, whatever.

Okay, if we start looking — we were supposed to be talking about cost and availability of materials. The energy content in megajoules per kilogram: aluminum, when we start with bauxite, the aluminum ore, takes 250 megajoules per kilogram of aluminum metal produced. If we recycle it only takes 15 megajoules. And if this can be converted almost directly to dollars, you can see that it's much more efficient to recycle. Plastics — well, these were numbers that were probably based on $80 a barrel oil, but in any case, plastics are going to be somewhere around uh 60 to 110. Copper is — anybody know why copper is so expensive in energy content? It's actually fairly easy to reduce, it was one of the first ones that cavemen used to reduce back thousands of years ago. It's because it's not very highly concentrated.

Anyone fly out of Salt Lake City and go over the Bingham mine? The world's deepest open pit mine, okay. If you — sometimes depending on how the plane takes off out of the Salt Lake airport, you'll look down, you'll see this big hole in the ground, goes down for over a mile deep as an open pit mine. It's the Kennecott copper, copper mine. And it turns out they're mining ore there that's only about a half percent copper. You get one pound out of a ton of rock, okay. And that's part of the problem. That's why it's so energy intensive. Yeah? So this is the energy that needs to go into producing these materials? Yep, to go from the ore to the metal, just bulk metal, okay. Doesn't tell us anything — you can't go the other direction, right? Once you made this — oh, we go the other direction, it's called corrosion when we go the other direction, okay. And it's actually cost us a lot, but anyway. We're not trying to go the other way.

But — well, you can. If aluminum's canned electricity, you can get almost 250 megajoules per kilogram. In fact, there's a student who took this class a couple years ago, Johnny Slocum. His dad's a faculty member of mechanical engineering. Johnny's a graduate student of mechanical, but when he was an undergraduate he started — he found a way to take treated little aluminum spheres and drop them in water. You treat them with tin and gallium — and people have been doing this for years, but Johnny found a way to do it reproducibly and quickly. He brings it into my office and he drops it in, and within 15 seconds the entire 5 mm sphere of aluminum has consumed itself and generated all kinds of hydrogen.

So we want to have a hydrogen economy. You want to fuel your car with hydrogen. People are trying to figure out how to store the hydrogen in your car. The federal government is spending hundreds of millions of dollars figuring out some way to store compressed hydrogen economically, lightweight, and do it. And you go to the pump — and when I heard this, when President Obama announced this eight years ago, I said, oh yeah, we're going to have a hydrogen economy. You know what a hydrogen flame looks like? Yeah, what does it look like? You can't see it. Most flames you can see because of the carbon soot, which glows yellow in the heat of the flame. So when you see a flame — now a natural gas flame, if you burn it near stoichiometry, is blue, and there's some carbon there, but mostly you're burning it up to carbon monoxide and carbon dioxide. But a poorly combusted flame is uh yellow.

But a hydrogen flame — and they have them around chemical plants all the time, they do hydrogen sparging, when you have a — I mean steam sparging — if you have a hydrogen leak at a chemical plant, rather than fix it because you have to shut down the whole plant, they actually will just put a steam line right there and they'll just spray or just release steam to dilute the hydrogen so it won't become explosive, okay. But the other reason they have to do this even for smaller flames is because people have walked right through a burning hydrogen flame. And you're going to go fill up your car at some gas station with hydrogen, and if there's a flame there, they're going to be people walking through flames all the time when they — because they ignite and there's no soot to give the flame a color. You can add carbon, but now, you know, you're sort of defeating some of the other purposes. Well, anyway, plus, where you going to get the hydrogen? Well, you can get it from a nuclear reactor, or you can get it by burning coal — that doesn't exactly get rid of the carbon dioxide, but anyway. Uh, there are all kinds of problems with this idea of a hydrogen economy. But if you had to fill up your car, and you would basically go and get a bunch of aluminum pellets and fill up with a tank of water, because that's all it takes to generate — I think Johnny's getting like 87% efficiency in generating hydrogen. So your question was, can you go the other way? Yeah, people are trying to do it, okay.

Now there's a little problem, that you have to treat it with gallium and with tin, and that's kind of what he's learned how to do. And there's some interesting metallurgy about gallium and aluminum not being miscible, and the gallium causes liquid metal embrittlement of the aluminum, and it's — anyway, that's metallurgy, okay. I guess that's what this course is supposed to be about anyway, we could talk about that.

Anyway, so copper, it's all energy content in the beneficiation, getting the ore to a high concentration. We used to have 6% copper ores in the Belgian Congo, or what we now call Zaire, but we used them all. The rest of the world, the richest ores in the world now are only around 1 or 2% copper, okay. And the Bingham mine is still — has been operating for like 80 years at half percent copper, six-tenths percent, or whatever. Steel actually has one-fifth the energy content of aluminum, and on the next slide you're going to see that affects the price. Oil — I guess this chart is based on $45 a barrel oil, okay. Sorry, I had oil on here. Coal $30 a ton — or actually that's not per ton, that's megajoules per kilogram. That's actually 40 — not, that's megajoules per kilogram, not dollars per barrel, okay. Cast iron is nice and cheap, glass is cheap, cement's even cheaper, wood's cheap, and stone is dirt cheap. Actually, it's stone cheap, okay. But recycled, the energy cost is much less. And that's why recycling is good.

The problem with recycling — well, actually it's not a problem with recycling, the point here is we used to use virgin material for almost everything. When the industrial revolution started — and these plots go back, goes back to 1870, 1900 — I couldn't find all these on the same scale yesterday when I created this plot, but there's sort of an exponential growth of steel, exponential growth of copper. This is US aluminum production, I couldn't find a good plot for world aluminum production — I could but it was all screwy. What happened here is — um, this is US production, but in around 1970 all of a sudden the Venezuelans, the Paraguayans [Paraguay], uh, the Canadians, and the Norwegians, they all started big hydroelectric plants, okay. A lot of our aluminum production was in big hydroelectric plants. Um, the TVA and Alcoa Tennessee and uh the Pacific Northwest and the Grand Coulee Dam and things like that. Um, so they situate aluminum, which is canned electricity, near hydroelectric plants because you can't get it out of where all the water flows. I mean, James Bay in Canada is close enough to New England but just barely to economically transport it as electricity to New England, can't get it to Pennsylvania, you're going to lose too much in transmission, unless they start building DC transmission lines through New York. You think people in New York are going to allow that? People in Vermont won't allow it. Anyway.

The point is tremendous growth, but what I really want you to look at is the integral underneath these curves. We've recycled steel, and today we recycle 70 to 80% of the steel we use, okay. If you look at how much steel we produce in a year and how much we recycle, a lot of that is what they call home scrap, where you have stuff left over at the steel mill and it never goes beyond the fence of the steel mill, it just gets — it's home scrap, it just gets remelted into the next process.

Um, but the real thing here is, since 1900 or so, we put an awful lot of steel, copper, and aluminum into the environment. We didn't put any aluminum into the environment to speak of before 1880, when Charles Martin Hall and um Paul Héroult developed the process for making inexpensive aluminum. Um, aluminum was a precious metal before that. The um — I didn't bring it with me, there's a nice picture in the book on the history of aluminum by Alcoa that has the royal French baby rattle was made out of aluminum, okay. The royal French dinnerware was made out of aluminum because it was lightweight. Uh, and aluminum was more expensive than gold, okay, because they didn't have a cheap way to make it. And then all of a sudden these two guys come along and form Alcoa and Pechiney, and they have an easy way to make aluminum. Um, we had um Henry Bessemer come along here, and copper was basically just mining, uh, increased mining and stuff. But we have been putting all this steel into the environment.

And it comes back. Every few years we build a structure and it comes back forty, fifty years later as scrap. And after a while you've got so much steel in the environment — and I can't remember, I did an estimate once, I think it was 5 trillion tons of steel have gone into the American economy over the last 100 years. And so we get back 50, 60 — or no, we get back actually over 100 million tons of steel in scrap, which — we actually export scrap to the rest of the world, okay. So it turns out there's going to be a little blip in here, and these things, although they're going up exponentially, they're going to start coming down in terms of virgin material. The use is going up but the amount of virgin material we have versus recycle is going to go way down. You're not going to need to do as much mining of the virgin ore, and you're not going to pay 10, 20, 50 times as much to process it into metal when all you have to do is remelt it. But it's not quite that simple.

Um, there are a couple of examples I've got. One has to do with um steel and recycling of steel. A few years ago they wanted to get — guess both of these have to do with lead, okay. They wanted to get the lead out of the solder in the connectors because lead's toxic and whatnot. So they're going to replace lead-tin solders with bismuth-tin solders. And the steel companies almost had a fit. Because you start putting bismuth-tin solders in automobiles, which is a major part of the recycling of steel scrap, and you make all of the scrap worthless. If you get 10 parts per million bismuth in a steel ingot, you can — it's just a big paperweight, okay. You cannot roll it, you cannot — I mean it's just brittle, okay. It goes to the grain boundaries and there's no way to get it out. You can't oxidize it out, you have to go back to the ore, okay. Then you can purify it out of the ore, but you can't get it out by just remelting the steel. There is no way to do it.

And so I remember twenty-five years ago I'd go to these conferences and people would — oh, we're going to replace lead-tin solder with bismuth-tin solder, and we're going to save the world from all the lead-tin solder. And I said, have you considered the fact that you will no longer be able to recycle steel? And they say, what? I said, well, do you know what happens if bismuth gets in steel, okay? And no, they didn't know. But you haven't seen bismuth-tin on the market because the steel companies know what happens if you get bismuth in steel.

Did you have a question? Yeah, actually, um, so when you say that we cannot recycle the steel by melting them, but isn't — Oh, we can, as long as we don't have bismuth impurity, right. If there is bismuth impurity, uh — wouldn't it be so originally how do you, when you have a — uh, well, how do you, like — Well, we don't use ores that have bismuth impurity. There's lots of iron ore in the world, and bismuth and iron are not generally compatible in nature. And so when we use iron ores, we — I mean, you produce virgin steel from iron ore, and you'll have less than one part per million bismuth. It's when you get to 10 parts per million bismuth, when you start recycling and man starts mixing other things in that nature didn't put these two things together, that you have to be careful when you say, oh, I'm just going to go into the recycling business. I guess — Question is, how do you obtain iron from an iron ore? Do you just not — do you not just like melt them? Well, you take carbon, actually — I'm going to talk about that uh in about two weeks when we get to really talking about steel per se. Uh, I will actually get down to some specific material systems. This is a longer introduction — in fact, Dr. Belar [?] was sort of criticizing me earlier this week for extending my material selection introduction into about half the class, half my module. But in any case.

Um, we don't — we avoid using ores — but the way you do it, traditionally we've always used carbon to reduce the oxides, okay. When we drive it off as carbon monoxide which becomes CO2, which now is an environmental concern for global warming. And when you have one and a half billion tons of steel each year, that's a lot of CO2, and it does have an effect on the total CO2 of the world. Um, but we've always been very careful about certain impurities, and there are certain impurities that are very bad. Bismuth is one of the worst, okay. And so, uh, I think the word has sort of gotten out, but I remember twenty-five years ago these people thought, oh, they were just stearing — soldering — and they didn't look at the whole systems problem of what does this mean downstream for recycling automobiles, because you're still going to have electrical wires and solder joints in automobiles. And you can take some of them out but you can't afford to take the whole thing apart, okay.

Uh, so that's that. Um, the other story comes from aluminum. Turns out lead itself is very harmful to aluminum. About seven parts per million lead in aluminum makes the lead brittle — or the aluminum brittle. They don't mix, the lead goes to the grain boundaries, it makes the aluminum brittle. So Alcoa Tennessee was having a problem thirty years ago. They were getting aluminum cans back, um, that had lead impurities. They would melt everything, they do the analysis, they find too much lead, they got scrapped. They got to send this back to the refinery, okay, they couldn't just simply remelt it and recycle it. So they thought, well, maybe people were — since they buy the scrap by the ton, they thought some people were slugging this thing with lead, which has eight times the density of uh of aluminum. And they checked, and they — it's easy, just x-ray the bundle and you'll see if there's a slug of lead in there, okay. Aluminum is not very x-ray dense, and lead is. Uh, they did, they did it. They couldn't find people slugging it with lead, which was the first hypothesis.

They started checking uh some smaller things, they'd melt just a bundle or whatever, and they found it was stuff coming from Mexico. And so they started looking, and they found that the problem is Mexico still had at that time leaded gasoline. And they did a plot along the side of a highway in Mexico — and Mexico didn't have a five-cent deposit on the bottles or the on the beer, the beverage cans — and you could plot the lead concentration away from the highway going out about a hundred yards, and it just dropped off. And this was just the fumes from the exhaust of the automobiles falling on the cans that people were throwing along the side of the road. And people would go collect the cans, and they would be coated with a very thin layer of lead, but it was enough to contaminate it. And I said, well, what do you do? They said, we quit buying scrap from Mexico, okay. I mean, that was their solution, okay.

So recycling is not always easy. There are more sophisticated uh concerns. Like, you have to grade your scrap, um, you can't use uh — you can't mix 6000 series with 5000 series because of the different alloy content and things like that, so you have to be careful about that. Usually end up downgrading the alloy from some of your better stuff. And some critical applications, like, uh, turbine blade alloys um and stuff, you'll find the spec will say, must use virgin material, okay. You can't use recycled because they don't know what's going to be in recycle, okay. Can be all kinds of things. So that's one of the concerns, okay. But my point of this is, we're going to be using more and more recycle in the future, we're going to be using a smaller fraction of virgin material in the future, because we have this tremendous resource out there of scrap coming back. We don't have that for certain materials like concrete, because we don't recycle concrete, which is a big problem we'll talk about later.

So this is an Ashby plot. Did we talk about Ashby plots yet? Did we? Anyway, it's — Materials and Mechanical Design, Material Selection and Mechanical Design — Mike Ashby was professor at Harvard [Cambridge], I think, I mentioned him before. Oh yeah, I showed his plot of materials uses through the ages a couple of days ago. But he also came up about 1980 with what are now called Ashby diagrams or Ashby plots, where he plots the property of a material over about four, five, or six orders of magnitude versus some other property of the material. He has a program, a company, that for $50,000, called Granta, you can get a 10-dimensional plot in the computer and you plug in what you want and it will pop out and tell you what the potential materials you can use to select. And if you believe that's a worthwhile thing to do, I got a bridge in Brooklyn for you. But, um, nonetheless, if you want a really coarse cut at something, yeah, it'll tell you. But if you really want to get down to the fine detail, Ashby plots might get you in the ballpark, and they're very useful for understanding the properties of materials. We're going to talk about — there are limits to the strength of materials. Here at about 1,000 megapascals is the ultimate strength of materials, um, the energy content is over a number of orders of magnitude. Foams obviously have a uh um low strength and low energy content um so far as that goes. We'll see different Ashby plots as we go along.

Um, strength versus temperature. Okay, this was one that came up in the last two weeks. I was down — I missed a day last week, had to be down at some inspection of an aircraft or something, and one guy told a story about the problem of bird strikes. And so Monday night my wife had wanted to go see Sully, the movie Sully, because my daughter had seen it and said it was worth seeing. It's not a bad movie. Anybody seen Sully? No. It's not a bad movie. It has nothing to do with reality. The NTSB was made a bad guy by Clint Eastwood. They were not a bad guy in the real world, okay. But they made him a bad guy. Clint Eastwood had to sell tickets. And, but it's an entertaining movie, think of as fiction, not — okay, based on fact. The guy really did land a plane in the Hudson River. That's about as far as the fact goes. Anyway, it was a bird strike, and he lost both engines at 2,800 feet and uh had to land in the Hudson River. And he was successful, 155 people all survived.

So here's a bunch of birds around a British air — a flock of birds. Uh, this is an F-111, and this is the composite radar dome, the nose of the aircraft, to hit a bird. And, you know, brittle composite just breaks up into a bunch of little fibers. This is a Pratt & Whitney engine after they get a bird strike. This is actually the leg of a bird sitting on the back of a tail wing, okay. There's a bird here, um. And in fact they have to uh test the engines, and I think it's a two-and-a-half pound chicken, okay. And back years ago, um, they'd come up with this spec and the British were having a hard time passing the thing. Well, Pratt & Whitney is having no problem. So they uh — the British sent over a guy from England to watch the bird strike tests that they would do. They take a real engine, you know, $5 million engine, they throw a bird in it. Now it's a dead bird, okay. Uh, I got a story about live birds, but that's another story.

Um, uh, the story on the birds was this guy watched the test, and Pratt & Whitney was having no problems passing the test. And the guy left. As he was walking out, he says, fresh, not frozen, okay. The British were throwing in frozen two-and-a-half pound chickens, okay. And the point is, as a function of temperature, when you get below 32 degrees, chickens get a lot stronger even if they're dead.

Okay, so maybe I should tell the story, I like to tell stories. So this other story was, there was a test lab down south of here, it's out of business now, but these guys did — had a metallurgical test firm, and I ended up in around 1979 or so becoming their metallurgist, because I was trying to pay for my house, and so I became a consultant. And I would go down there and I would do 500 failure analyses a year down there. And these guys also, they did non-destructive testing, uh, that was their business. I think they all graduated from high school, but none of them had any real college or scientific background or anything. So they um — they were always trying to figure out some way to get rich. And they found — they read an article about some tornado went through Kansas and all the chickens were plucked alive in the tornado. So they decided it must be the low pressure. And so they had a little vacuum chamber, and so they — you go get a dead chicken and they throw it in there and they pump it down and they take it out and the feathers are still on it. So these guys decided it had to be a live chicken, okay.

So they got a live chicken and they put it in the vacuum chamber and they started pumping it down. And they opened it up, and this chicken — I wasn't there, if I had been there I would have stopped this, okay — this chicken kind of stumbles out, and, anyway, his entrails were coming out the other side and everything. But, uh, you get pressure — this is no worse than women drying off their cats, grandmothers drying off their cats in the microwave, okay. Haven't you heard those stories? That had — when microwaves first came out, that was very common, okay. I'll see you tomorrow.