SMS_F2013_14

Of presentations — this is a flexible schedule in the sense that if there's a conflict, I'm handing it out now. If there's a conflict, we can barter and trade as far as that goes. I've got an extra day scheduled because something will come up and someone won't be able to do it one day. I'm also scheduling 8:32 to 10. Okay, we had the 9 to 10 slot, and you know, if some of you can only — can't be here 9:30 to 10 — and if I put you in that slot, we'll just switch it around. Let me know okay. It's also flexible, and if some travel schedule comes up for me, we got an extra day scheduled already and I might have to move some people. But hopefully we don't do that. I put it down my schedule and I'll try to hold the days. I have no guarantees. My life is not that simple, okay.

Um, any questions from before? If not, then let me just — this is another thing out of a magazine from a couple years ago. Magnesium replaces plastic in die cast fishing reel frame. Okay, well okay, this is nice, but you're not going to get rich, you know, making magnesium — substituting magnesium for plastic. It actually probably is maybe lighter than the plastic, and it's certainly stronger because typical plastic strengths — the highest strength plastics, unless they're super-duper four-hundred-pound aviation type of plastics — the highest strength plastics are about 10 ksi. You can get 20 ksi out of magnesium, so it can be stronger and stuff. But you know, I look at these things in these materials trade organization magazines, and I think — I always think, well okay, these are the boutique applications or the boutique materials.

I did want to take in this last time, go through what are structural materials and what are the materials that we use. The very beginning of class I handed out this paper where I told you that 95% of all metal is iron and steel, and number two was aluminum, and copper and zinc. Well, it turns out — I actually spent the last 45 minutes looking on the web, and came up with this, which the numbers actually work out pretty close to what I had talked about, been talking about all term. And that is that of structural materials production, steel is about 1.5 — I've been saying one billion tons, it's 1.5 billion officially now. Cement is 2.2 billion. I've been saying two billion, it's 2.2 billion, is growing rapidly. It's growing rapidly. I had a student do a bachelor's thesis on some of this type of stuff about eight or ten years ago. It was like 1.6 billion for cement, and it was — I think two billion tons for — so at that time it was 1.6 billion tons for cement and it was 800 or 900 million tons for steel. And they've been growing fairly rapidly.

What shocked me when I looked this up this morning is the country that produces two billion tons of cement, 90% of the world's cement, is China. Okay, and obviously they weren't producing that much cement before. Obviously, if you go to China, they're building lots of cement buildings and roads and dams and everything else. So anyway, aluminum is 45 million tons, copper is 15 million tons. If you went back to this graph that I gave you the beginning of the semester — and hopefully some of this puts things into perspective — not all these are structural materials. Lead was a structural material. In fact, in the middle ages lead was one of the most produced metals. We didn't have a steel industry or an aluminum industry, and the copper industry was very small. But lead was one of the easiest things to get from its ore, as was zinc, and so these were some of the primary metals back three hundred years ago.

Nickel — I mean, our whole aerospace engine technology and a lot of our corrosion resistance and nuclear reactors and things depend on nickel. Two million tons a year. I remember when I was an engineer working in this industry and they were talking about building a pipeline from Alaska — this wasn't — they were already building the Alaska pipeline at that time, or it was about to go into service, but they were talking about another pipeline. And it had — I guess it was the gas pipeline they wanted to build — had to have excellent toughness, and International Nickel came up with this new alloy steel to make the pipe out of. And it had one and a half percent nickel. And then someone did the calculation, there wasn't enough nickel in the world to supply that pipeline in an annual production, okay. So that didn't work out very well.

Now, they did take that steel — it was a precipitation-hardened copper nickel steel okay. It had fantastic mechanical properties. It just blew away most other steels in that strength range and stuff. But they found niche applications as crack stoppers. A problem with steel — you know, I'm not saying steel is the most wonderful material in the world, it's just the largest used structural material — but they have had brittle fractures in pipelines that run for thirty miles. You know, get a crack in it, if it's a gas pipeline okay. An oil pipeline doesn't do that because an oil pipeline is pressurized hydraulically, and the decompression wave in the oil, or in the liquid, is faster than the crack runs. But in a gas, it turns out the decompression wave in the gas is slower than the crack — a brittle crack will grow at half the speed of sound, which is maybe fifteen hundred, two thousand meters per second. Okay, it sounds like a rifle shot, you know. When that crack starts to go, it's a big bang, and it's moving at let's say 1500 meters a second. What's the velocity of sound in air at sea level? Sea level. 346 — 343.6 meters per second at STP. I remember that from my high school physics. So 300 meters versus 1500 meters — it means the crack is always under tension as it's growing, as it's running.

And gas pipelines had — there had been one where a crack started and ran in a brittle steel and ran for thirty miles before it stopped. So they decided they were going to use the super-duper steel and put little one-foot rings in there about every mile so that if the crack started running, it would hit one of these rings and it would stop. Okay, you know, ductile material. So they were going to use it for that. Later on, the US Navy decided it was a good steel for submarine hulls okay. So they did find an application.

In any case, magnesium, we said is 250,000 tons. Tin, which is not a structural material, is also 250,000 tons. I put it on there because it was on this list, this little graph that I had stolen from someplace okay. They had tin on here. Titanium — one of the wonder metals, kind of first developed over here at Watertown Mall, actually it was the Army Research Center at the time. It's now a mall. If you go over there — Home Depot, you know, TJ Maxx. But titanium is essential to the aerospace industry, but it's only 60,000 tons per year. I did learn that the B-1 bomber uses about 100 tons of magnesium — or B-2 bomber uses about 100 tons of magnesium to produce — that's not the weight of the aircraft. They're only maybe 10% of that weight actually gets into the aircraft, but you have to produce about 100 tons in order to get the parts, to produce parts.

Neodymium, which is obviously not a structural material but we've talked about, is 7,000 tons. Zirconium, which we'll talk about in a second, 3,500 tons. Scandium, which we talked about for baseball bats — it's basically an alloying element, aluminum is about the only application I know of — 2,000 tons. And I actually started doing it — lithium is 600,000 tons, obviously not a structural material, but its growth has grown by a factor of six in the last ten years for battery applications. Silicon, seven million tons. Okay, silicon metal — we're not talking semiconductor, well actually we could be talking semiconductor grade, but 80% of all that silicon goes as an alloying element into steel okay. And another 20%, or 19% or whatever number, goes in as an alloying element for aluminum. Okay, so most of the silicon — silicon metal we make, a very small fraction goes into semiconductors. Because obviously you can put a lot of power on a little chip that doesn't weigh much. Most of the silicon goes into making steel and aluminum as an alloying element.

I looked up beryllium — 200 tons. Beryllium market's dying. It went from 350 tons a year to 200 tons just in the last few years. Sodium, um — I mean, I'm kind of going down the periodic table now. And actually I had thought once upon a time, of rather than doing presentations, if I had a big class, I was going to give each person an element on the periodic table and have them do a presentation or a paper on the element and how it's used. I always thought that would be a fun course. I don't know who would ever sign up for it, so I teach it anyway — I just call it Structural Materials. Okay, I'm sandbagging you and giving you the course I always wanted to teach but no one would ever sign up for.

So if I look at this — this is a periodic table — and we kind of went through, and I put in yellow the real structural materials that we use in the world. There's iron, there's aluminum, but more importantly there's crushed stone. Silicon — most of the stone — I mean, some of the stones, limestone, is calcium. Portland cement is over here with calcium. So the ceramic materials are actually the most highly used, followed by iron, followed by aluminum. Magnesium — a large fraction of the magnesium goes into anodes. Only a relatively small fraction, like 25%, goes into structural materials, castings usually. Because one of the problems with magnesium, aside from the fact it's hexagonal close-packed and you can't roll it very easily because it doesn't have enough deformation systems — and you try to make a — try to deform it to get a general shape change, and because of the lack of slip systems — you learn about dislocations and things, well they only work in certain materials like cubic metals — and magnesium is not a cubic metal, it's hexagonal close-packed. It deforms by twinning, and you will crack it if you try to give it a general shape change.

Yes? [Student question, inaudible.] At low temperatures. But at high temperatures it becomes BCC. So when you make titanium sheet, you alloy it to get rid of that pesky old HCP phase okay. But then you also do heat treatments to bring it back, because that pesky old HCP phase actually has some good strength and other properties. So titanium and steel have this advantage, that they're allotropic — they have a different crystal structure at high temperatures, low temperatures, and you can do all kinds of things to get interesting microstructures. And I haven't been talking about microstructures in this class. You know, I did my doctoral work in physical metallurgy, but I ended up becoming more of a process metallurgist. But there's really interesting stuff. Titanium, you can cycle through this allotropic phase transformation from one temperature to a lower temperature — oh, I think it's around 800 or 900 degrees centigrade — you cycle between that and you can get nucleation, growth, nucleation and growth, you get finer and finer grain size, and you can end up forming a superplastic alloy that allows you to do fantastic processing. And if you take the deformation processing module, I spent a little time talking about superplasticity. And we wouldn't — superplastic forming of titanium really — I don't know if I want to say it transformed the aircraft engine business, but it sure made aircraft engines a lot cheaper than they would be otherwise. We can make structures out of titanium for jet engines that we never could have made any other way.

So some of these things have very interesting properties. You could give a whole course on any one of these elements as a structural material. Well, not any one of them as a structural — well, of the ones in yellow, yes you can. Carbon is there because plastics — 300 million tons of plastics. But that's all plastics. And you say, well, professor, you didn't mention much about plastics, and it's a pretty important structural material. It is. I'll tell you everything you need to know about plastics: they don't go above 500 degrees Fahrenheit, okay. But below that, they're easy to form, if you get the right one. It has the right corrosion resistance in that environment — don't put it in another environment, okay.

Yes? [Student question about wood.] You know, I was going to look that up, but I kind of ran into class time. You know, I was actually thinking of spending part of my weekend kind of looking at more. So easy to do research on the web now, right. Wood production — if I went back to my little plot, it's right up there underneath stone okay. But the problem with wood production — what fraction of it is structural material? I mean, you can go find how many board feet of timber and maybe that's — but there's a lot of wood that goes into wood chips, you know. And most of the wood in the world is destroyed by bugs okay. We just let it rot okay, in the forest, because it's so difficult to harvest okay. Except we find a good stand of it and we want to harvest the whole thing every one, so we can just denude the landscape and you know, destroy the environment and everything. But wood always has been a fantastic material, and people still pay a premium to make things out of wood. I mean go look in my office with my bookcases. I designed those okay, and I had someone build them for me. It's wood, you know. Metal would have been much cheaper, but I kind of like the cherry. You know, it looks — you know, a metal bookcase looks sort of industrial, right.

Anyway. So wood is a huge number, but the problem is, it's used for so many different things that are non-structural, which is one of the problems with some of these others. Magnesium — I may put down 250,000 tons, but only 25% is structural. Silicon — well, metallic silicon, 99% of it is used for alloying in steel or aluminum, and 1% of it is put into this huge profitability on value-added. You take a little chip of silicon, just happens to be a single crystal, and you can turn it into something that's worth five hundred dollars on a per-pound basis. That blows away any of our structural materials.

There's a good reason for that: structural materials are used in very large volumes, and therefore you have to consider cost. And I've been beating cost into you since day one, right. But why am I beating it into you? Did I tell you the story about — it's about twenty years ago — a very prominent faculty member in our department now, by the time — he was an untenured associate or something — and we were walking across campus, we were right there in front of the Great Sail — I remember he says, well, did you see Professor Clark's paper in the Journal of Metals this month? I said yeah. He says, you know, I never thought about it before, but cost really is important. And I thought — what, you're an engineer and you didn't know that? Cost — he'd been an MIT undergraduate, graduate student, he's now a professor, and he didn't know that cost was an important criteria. And now he's made millions of dollars in his company spin-off, okay. I think he knows about cost now. But he learned it from Joel Clark, by reading one of Joel Clark's articles, okay.

I guess I could tell you another story. Your MIT education is actually a very good education for many reasons. I think I may have told you, I consider an MIT undergraduate degree to be second only to Princeton as a general undergraduate degree in the United States. But if you're interested in science and engineering, I actually think MIT is better, okay. We could talk about that, but — so MIT is a great place to learn, and it gives you a lot of the tools, the attitudes and things. But it doesn't give you a very practical knowledge, right. And so some things — by telling you some of the stories I give you, try to give you some ideas of practical knowledge.

So when I was a senior — uh, Professor Flemings — I'd worked in his lab, and he kind of liked me at that time, he hates me now, but he liked me at that time. And he was the Foundry Educational Foundation professor — they have professors at each school, and they controlled certain scholarships. And he saw me kind of walk down the hallway once when I was a junior, and I sort of dejected, and he said well, you look so sad. I said, well, I just got my financial aid package for next year, it's 90% loan and you know 10% scholarship or something. And he says oh. The next thing I know, I get a letter from the scholarship office and it turns into 100% scholarship from the Foundry Educational Foundation. Well, I wonder how that happened, okay. So Professor Flemings did me a nice little favor.

Well, when I started out in senior year, he had the opportunity to send a student to the Foundry Educational Foundation conference. These are people in the foundry industry — want to hire MIT students, right. So they would take — the FEF professor would find a student that they thought was a good student, be good for the foundry industry, and they sent them off to this conference. You stay at the Drake Hotel in Chicago, a very fancy, very snooty hotel. First place I ever went into had real cloth in the restrooms, you know, for, rather than paper towels. I've seen those places since then, but they're kind of four or five hundred, six hundred dollar a night hotels. And it was right across the street from the Playboy Club, which I guess I shouldn't be saying nowadays, but that was also probably a draw back in those days when it was 95% males MIT and stuff.

Anyway, so I actually just boldly said, well, why don't you send Harvey, why don't you send two of us — and Harvey Cohen. So he did. So Harvey and I both — I mean, Harvey probably wouldn't have gotten an invitation, but Professor Flemings controlled enough money. So what was that — why is it telling you that about — oh, so we go to the FEF conference, and these are all practical guys who are sitting there in their labs, they're ramming sand molds and casting things and stuff. And they tell this joke about the ignorant foundryman who didn't know the difference between a cope and a drag. Now, how many of you know what a cope and a drag are? See, you're MIT students, you don't know.

Well, the joke — I'd heard it before, but I had heard it about the ignorant Navy captain who didn't know port and starboard, which was right and which was left. Port is left and starboard is right, by the way. And, you know, someone found this out once because — one morning he had looked like he was meditating at his desk, and in fact, someone was standing over him once and he pulled out the drawer and said, "port is left, starboard is right." He had a little crib sheet in there, okay. Well, they told the same joke with cope and drag. Okay, the cope is on top and the drag is on the bottom, these are the two halves of the sand mold okay. And Harvey and I looked at each other — we didn't want to open — [trails off] — and they were telling this, you know, how ignorant a foundryman would be not to have learned that.

So part of your MIT education is to learn nothing practical, but to learn the fundamentals. And you will find that you can learn these other things — like copes and drags, port and starboard — you can pick that up off the street okay, in about two weeks. But you can't pick up Fourier's first law. You had to learn that somewhere okay. It's not intuitive. So there is an advantage to an MIT education, but you will be made fun of when you get out there in the real world, when you pull some of these boners, like you don't know what a cope and drag is. What's a drag?

Anyway, so we've got all these structural materials, or these elements in the periodic table. We've now talked about magnesium. Carbon is for plastics. Silicon is for stone — and they are structural materials. Scandium we've talked about, and go look up, but about the only application of scandium I know is alloying in aluminum. Yttrium — what's yttrium used for, anybody know? Stabilizes zirconium. Adam Powell yesterday said they got a problem — there's only so much yttrium in the world. I didn't look it up. But anyway — actually I did look it up somewhere, but I didn't write it down, did I? No, I didn't. Anyway, so there's only so much yttrium. It's also used as an oxide growth promoter on turbine blades. Iron, chrome, aluminum, yttrium — chrome — okay, I got that back okay. Cobalt, chrome, aluminum, yttrium. If you want to have the absolute best high temperature oxidation resistance, you put a little yttrium in with the cobalt-chrome-aluminum that you may have in your nickel-based superalloy. Or if you don't have any cobalt because it's expensive, you put — you have iron in there — and you will grow an oxide on the surface that has about 200 degree higher temperature capability of oxidation resistance. And so most of our turbine blades out there in the world are CoCrAlY or FeCrAlY alloy. You have to have like a thousand parts per million or less of yttrium, but you need yttrium okay.

Lanthanum — I don't know any use of lanthanum except to make lanthanum hexaboride filaments for scanning electron microscopes and things like that. It's the lanthanide series, so it's famous for that. Titanium — 60,000 tons. Titanium is a fantastic metal in many ways. I meant to bring — I have a little pacemaker can from forty years ago. Uh, pacemaker that you put in your heart, you know, to signal your heart with a pump and stuff. They've been making them out of titanium for, you know, fifty years, because titanium just doesn't corrode in the body. It also doesn't corrode in heat exchangers. It's got good high temperature capability. Aluminum — you know, the Concorde flies on temperatures — the SST — well, the SR-71 Blackbird had a titanium skin. It was one of the first titanium aircraft. Didn't have any aluminum — aluminum wouldn't make it to 90,000 feet okay. And the temperatures you get from the frictional heating at the speeds those things go, which are like Mach 3 or 4 or something okay at those altitudes. Uh, the B-2 bomber, you know, is mostly titanium in terms of its skin and things.

So aerospace — it's relatively lightweight. It's not as light as aluminum, but in terms of melting point and temperatures — and because it's lightweight, and because it can be superplastically formed, we use it on the compressors of jet engines. We can make extremely complex structures okay. But it is very reactive. And if you get above 900 degrees centigrade — it's very corrosion resistant, it has reasonably good oxidation resistance up to 900 degrees, but above 900 degrees it will dissolve its own oxide, and all of a sudden it catches fire. It's like a great big magnesium flare. And they've had engines go — you know, just a great big ball of fire — and just end up with a burned-out engine, okay. Completely burned out. Not a good day. That's why you have multiple engines, okay. It's also why you should control the way you operate the engine, so they're not designed to get to those temperatures. But some good old Air Force pilots have been able to do it.

Zirconium — primary uses of zirconium, there's only two I know of. Anybody know one? They're both structural ones. Reactor fuel cladding. So you got this uranium or plutonium oxide pellet or whatever, and you put it inside a zirconium tube. I meant to bring one — I have a little piece of zirconium tube. Goes for about a hundred bucks a foot okay. It's also a hexagonal close-packed metal. It's not the easiest thing to form. Beautiful metallography. I mean, you can anodize and you get these wonderful colors. I mean, it's like — look out there on the floor of that thing and all the colors — that could be — you know, change it a little bit to make grain size and it'll be the color of a zirconium metallography. But that's not a good reason to buy it. So why is it good for nuclear reactor fuel cladding? It's neutron-transparent. It has one of the lowest neutron cross sections. Neutrons — like it doesn't exist to neutrons. It's measured in barns, right. Okay, whatever a barn is, but it's some measure of neutron flux.

There's another material on this periodic table that I've skipped: boron. Okay, is a neutron poison. It accepts neutrons very well. Put a little borax in your water in your nuclear reactor, and you can stop that reaction very quickly. So boron is a great material. Gadolinium is another wonderful material. They've actually made stainless steel alloys out of GE with a little gadolinium in them. Here's gadolinium down here. Other than that, gadolinium's claim to fame — it's one of the few ferromagnetic metals or elements. There's only about four or five of them. Iron, nickel, cobalt, and gadolinium are the four ferromagnetic elements, at least at room temperature. And gadolinium just barely made it okay. It's got a Curie temperature only a few degrees above room temperature.

But in any case, so there are these nuclear materials. Zirconium, boron, having opposite effects. Turns out hafnium is — it's not really a neutron poison, but it's got a big neutron cross section. So in order to make zirconium fuel cladding, they had to get very low hafnium zirconium, very low impurity. And frankly, these things right here in these columns of the periodic table, they tend to be found together in nature, okay. If you have a zirconia ore, it's going to have lots of hafnium, or vice versa. Same thing about niobium and tantalum okay. Two Greek gods. Sadoway told me once — Professor Sadoway — that they're called Niobus and Tantalus because they were Greek twins. I looked that up once, I'm not sure they were twins, but they have something to do with Greek mythology, and they were named that because it was so difficult to separate them. They're found in the same ores, and it's difficult to separate them. That was what his doctoral thesis was about.

Vanadium — well, so we did hafnium. Well, hafnium is used in some very high melting ceramics, but it's very pricey. It's not really a structural material. One application I know of is in plasma torches — air plasma torches. Rather than tungsten electrodes, they have hafnium electrodes. Because when it oxidizes, the hafnium oxide actually still conducts enough electrons that you can still get the electric current through in your plasma torch. So rather than having a tungsten electrode, they have a hafnium electrode, which you expect to oxidize, and it will keep working — you know, just like the Energizer Bunny or something keeps on going. But that's about the only application I know of hafnium.

Vanadium is used mostly as an alloying element for steel okay. Not very large quantities — a tenth of a percent. You can get grain refinement, because vanadium forms carbides. Vanadium is called vanadium because, after the Greek god of vanity, Vanadis. Okay, vanadium forms beautiful colors in its salts — sulfides, oxides, chlorides. And it has lots of them. It has almost every valence in the periodic table, vanadium, and it has all these different salts. It's considered a vain metal okay. That's why you call it vanadium.

Tantalum — number two after gold basically in corrosion resistance, okay. Fantastically stable oxide. Used to make the best capacitors in the world. If you own a computer, you got some — sometime you purchased some tantalum with it. Very small amount, but it forms a very strong oxide and you can make these very fine porous powder metallurgy structures that you then anodize to form an oxide skin, and that becomes your capacitor okay. So tantalum — kind of pricey, about the price of silver. But you don't use much, and if it's a medical thing, who cares? I mean, you know, doctor's making a fortune, who cares about the cost of metal.

Chromium — actually is seven million tons. I looked it up. Just like silicon — metallic silicon — chromium is in here with lead. I mean, it's one of the most used metals so far as that goes. But it's almost all ferrochrome for making steel, stainless steel. The other application is chrome plating. And I actually found, as I was doing this on Wikipedia — if you can believe Wikipedia — apparently they found brass objects that people put chromium oxide on thousands of years ago. So they dig this brass out of the ground and it's not tarnished, because it's got a chromium oxide skin, just like stainless steel. Chromium is essential for all our high temperature alloys. Either chrome or aluminum are what give nickel alloys and cobalt alloys and iron alloys their high temperature corrosion resistance. It's not the iron, nickel and stuff. It's the chrome oxide.

Chromium is not a very good structural material by itself. It melts at over 2000 degrees, makes it a little pricey to process. But it's brittle by itself as a metal. You can take a hammer to it — no fracture — as far as that goes. But it's a very important metal. It only comes from a few places in the world. Back, well, before you were born, there's all kinds of problems in Rhodesia, and Rhodesia has a chromite ore that you don't even have to clean up. You can just take that rock out of the ground and throw it in a steel blast furnace, or the steel melting furnace. And so there was an embargo on Rhodesian chrome. You've heard of blood diamonds nowadays, you know, these war diamonds. And what are the other elements that — there's a certain type of elements where some country has sort of a control, and then they have a civil war. There's the diamonds in Angola, but before that, it was the chromium in Rhodesia. And they had a worldwide embargo on Rhodesian chrome, except it was all leaking and getting to the steel mills anyway. And everybody knew it was Rhodesian chrome. It might have come through some other country and was laundered through some other country, but you could tell — no one else in the world had that quality of chromite ore okay. But it comes from India and it comes from parts of Russia. It's a strategic material in the sense that we don't have any good US source. We actually have lots of minerals, but we can't extract it cheaply enough compared to these other good deposits.

Niobium is also used with vanadium as an alloying element for steel. We've kind of covered those. Molybdenum is — well, it's close to tungsten in a lot of its properties. Very high melting. But it's used as an alloying element. Stainless steels — it's used as an alloying element in alloy steels. It does have a few — uh, space — structural material applications, because it has a very low coefficient of thermal expansion. So if I'm trying to build some telescope in space and when the sun hits it, it can't thermally expand too much or it'll mess up my optics and stuff — they might use molybdenum in that spacecraft, even though it's very heavy, very dense. It's got very good thermal conductivity.

There are some molybdenum-rhenium alloys okay, that have — a lot of these high temperature alloys will be molybdenum-rhenium. Rhenium is used for moly-rhenium alloys. But it's a refractory — it's a platinum group metal okay. These are the platinum group metals along here. Not — far from tungsten. But ruthenium and rhodium, those guys all make the what they call the platinum group metals. We're getting the rhenium out of turbine blades. But I don't know if I told you the story that when I took my creep course from Professor Grant, who had developed a lot of these alloys, first question in his class was, what's the best material for making a high temperature turbine blade? And we all guessed, you know, nickel or cobalt and stuff. He says, no, platinum. Doesn't oxidize in the air, goes to 1700 degrees C, has excellent strength, easy to form. Only problem is, it costs too much. Well, rhenium was one of the cheaper platinum group metals, and they ended up putting — within the last, let's say around 2000 — we were getting to 6% rhenium for those turbine blades, which is why those turbine blades cost six, seven, eight thousand dollars a piece. Made 6% of them platinum group metal. But in any case — but getting back down, they're learning to take the rhenium out.

Ruthenium — the only application I've ever heard, hexagonal close-packed. A guy came to me once, even wanted to make ruthenium BBs, basically, for ballpoint pen tips okay. It's hexagonal close-packed, so I had to show them how to melt it — to make in surface tension would make it spherical. Osmium — I know of no application of osmium except among the biologists. They use it to stain — osmium tetroxide, to stain cells. But when you get to osmium and iridium, these things are produced in hundreds of ounces per year in the world. They're not exactly something you're going to choose for structural material. Although iridium is used for structural material. The Voyager spacecraft, that's heading out of the solar system now — is officially headed out of the solar system after, what, 30 or 35 years going out there — it's powered by plutonium in a thermoelectric generator. There's not enough — sun's radiation, when you get that far away from the sun, to provide the energy to go beaming back the signals and stuff. And so the Voyager spacecraft was plutonium in an iridium sphere. And it really melts at a high temperature. And if you add a little tungsten, some other things to it, you'll have ductility. And so when I was — I had been interviewed by Oak Ridge when I was graduating, and they offered me a job. But I saw a file cabinet down in Oak Ridge, Tennessee, that had about 50% of the world's supply of iridium, because they were making these little things for things like for NASA — uh, for the Voyager spacecraft. Iridium is also good for platinum jewelry. Made my wife's engagement ring out of platinum-iridium. Electron beam melted it.

Tungsten — I sort of skipped. You know what tungsten's used for. Light bulbs okay. This is what made Thomas Edison a rich man. [Pauses on Coolidge's first name.] Coolidge was Coolidge's first name. Anyway, Coolidge became one of the directors of research at General Electric, but he was an MIT grad. And in fact he became a wealthy man, and he gave 350 acres or something to MIT, up in — [searches] — begins with the T, it's up here on the North Shore. But at one time they thought of moving MIT from Cambridge up to these 350 acres up there because Cambridge was such a pain today to live in — not for the students necessarily, but for dealing with the politics here okay. But anyway, they finally decided to stay in Cambridge. But — caught the — anyway, oh, that's a different Coolidge for the X-ray tube. But anyway, the Coolidge process for making tungsten wire was the thing that made the light bulb possible. And the Cleveland wire plant of General Electric — they used to say, if you want to be a metallurgist, just go to the Cleveland wire plant and you get burned out. Because metallurgists would go there and the only thing you could work on was controlling grain size in tungsten okay. That's what gives tungsten light bulbs — incandescent light bulbs — their life: making it resistant to grain growth.

Cobalt. Cobalt's hexagonal close-packed and it has interesting property — has ten times lower wear than any other metal. Because they say it's because of hexagonal close-packed. But just empirically, if you have a wear problem, do a cobalt overlay weld, overlay, and you may get around the problem okay. You get ten times better wear resistance with cobalt alloys. Those $300 scissors — they had a cobalt insert okay, to keep them sharp.

[Student question about cobalt tools.] Maybe — I don't know, the Cobalt Tool Company. Oh no, that's — I think that's — well, I'd have to go back and see okay. I have seen cobalt tools. Oh, there's a — they have the big blue, yeah. Okay, that type of, um — I don't know okay. You don't hear me say that very often, but I don't know, okay. I don't think it is. But certainly Kennametal, and some other companies that specialize in carbides and stuff, did kind of start with some of the cobalt alloys and their wear resistance.

Cobalt has excellent high temperature properties for turbine blades and stuff. But what happened is, most of the world's cobalt comes from the old Belgian Congo, which is Zaire now. And that's in the middle of a civil war most of the last 50 years. And so the supply of cobalt is not reliable. People are concerned about that. Nickel alloys — well, nickel alloys are interesting. Just like the stainless steels — when you need more alloy capability than, or corrosion resistance than, stainless steel can give you, go to nickel rather than iron base. Although the metallurgy is similar, and the alloying elements are still chrome and moly and stuff. This is nickel content versus molybdenum content, chloride ion stress corrosion cracking. And you got down here some of your alloy 800, alloy 600 and 601 — those are nearly pure nickel. Like 80% nickel and zero molybdenum, which is expensive. 304 stainless is right here, 316 stainless is right here. And you keep on going up — in these, Inconel 825, Alloy 25-6, which is a super — it's probably a super ferritic for me — [corrects] this is super austenitic, I have to go back and look. Alloy 625 used in a lot of pressurized water reactors. C-276 used in really severe corrosion in oil refineries and things like that. But look at it — 16% chrome moly, and 16% nickel. This is not a cheap alloy okay, as far as that goes.

As I'm doing that, I also realized that I — oh well, let me show you something else about the nickel alloys, in terms of comparison with the stainless steels. Here's the cyclic exposure for oxidation versus mass loss. 304 steel bites the dust in two or three hundred hours, at 2000 degrees Fahrenheit. So if you're talking oxidation resistance, you get to the nickel alloys, and all of a sudden — here's your super — the highly alloyed heat resistant stainless steels. Here's your 800 series Inconels, here's your 600 series Inconels, and you can go for much longer times at very high temperatures. So again, if you're willing to start paying sixty to a hundred thousand dollars a ton, then you can get fantastic properties. But one of the reasons we don't use so much nickel in the world is because it's kind of pricey. But it has great properties. If nickel was as cheap as iron, steel would not be important okay. It's almost a one-to-one substitute in many alloys.

But the price of nickel has fluctuated a lot. One of the times — Bob Rose, my thesis advisor, used to like to tell the story of one of his former students from MIT was working for International Nickel, and the price of nickel shot up. And so they came to him — he was in the research labs — and his manager said, well, we need a replacement for nickel. And so he had to go off and — you know, he thought this is stupid, I mean, gonna replace elements in the periodic table — so he came back and he said, well, palladium works well. Palladium's a platinum group metal okay, it's more expensive than nickel. Palladium — now at that time palladium didn't have a big application. What's the big application for palladium now? 80, 90% catalytic converters for cars. Okay. The only thing that works to burn carbon at low temperatures, to oxidize carbon monoxide to carbon dioxide, is either platinum, or palladium, or rhodium, which is even more expensive. Rhodium and iridium actually have applications as catalysts themselves in production of acetic acid. They are the catalyst. But in fact, as one chemical engineer told me once, when you're running an acetic acid plant, you're not really producing acetic acid, you're running an iridium or platinum recovery plant. Because you can't afford to have any rhodium or iridium end up in that acetic acid and being used, you know, as an impurity. I mean, it's just — this stuff is too expensive. You know, $2000 an ounce okay.

I didn't tell you the second application for zirconium. We talked about nuclear fuel cladding. The second application is, if you want to make acetic acid, you can either make it out of a nickel-molybdenum alloy, which is Hastelloy B-3, okay, alloy, which is pretty pricey, or you can make it out of zirconium, which is even pricier. Hastelloy B-3 will last for 30, 40 years, and your plant will be good for 30 or 40 years before you have to scrap the 100 million dollar plant. Make it out of zirconium, it'll last for centuries okay. And you can make it out of titanium, the only problem is, every now and then you get hydrogen into your titanium and the plant explodes okay. But aside from that, titanium is very good in acetic acid, except it sometimes will pick up hydrogen.

You know, I haven't done copper, silver and gold. They're kind of known historically. Copper is one of the most used metals, and I can tell you some stories on copper. Zinc — use is 12 million tons okay. Zinc is, of the ones I came up with here, it's number four in worldwide production of metals. But most of it goes as a sacrificial anode to make galvanized steel okay. It's been around for centuries okay. Zinc, lead and tin have been used for centuries. Copper-tin was where the bronzes of thousands of years ago — we learned to make zinc the last four or five hundred years by carbothermic reduction. And we do make zinc — back when I was your age, the door handles on cars might be a zinc die casting. Nowadays, they've made stronger plastics, and they make them out of plastic and they put a chrome plate on them okay. So they used to be zinc with a chrome plate, so far as that goes.

Anyway, anything else that we ought to — we kind of marched across. You start getting over here, and these are low melting alloys. You get over here, these are sort of — they're not metals — or they're gases. And they tend to be impurities in metals. Cadmium has lots of good properties for corrosion resistant coatings, but it's got a low vapor pressure, and it's great for silver solders. Anyway, if you go back to it, to kind of go back to my original theme here, if we're talking about structural metals, there's only a few of them. Steel, aluminum, some applications of copper, some applications of zinc — lead is — we're trying to get lead out of the world right now — nickel, essential for high temperatures. Magnesium — the hope for the future, has been for the last 50 years and probably will be for the next 30 or 40, in spite of what Adam Powell hopes. Titanium is just too pricey. Takes too much energy to produce it. The US government had a huge program a few years ago to try to make low-cost titanium for armor. But you got to get it down below ten dollars a pound, and they couldn't do it. It's around a hundred a pound okay.

And then we have these other elements, niche applications. Zirconium, it has this nuclear cross section, or it has this corrosion resistance, and some of these things. But we're getting down to things where we're in thousands of pounds a year, and it doesn't matter, you know. Dysprosium — Adam talked about dysprosium. You want to talk really big volumes — well, there's cement and there's stone. I had to estimate that — I did get from the — United States uses 1.72 billion pounds — or tons of stone. And if you know that the United States is about 25% of the world's economy, stone is probably even more than this, but I just put six billion. Sound dwarfs everything else. If you're in civil engineering, they teach a whole course on cement and the chemistry of cement and properties of cement, and because the concrete is a composite.

Plastics, you know — plastic is replacing a lot of things. This is just simple polyethylene, but it's gas pipe. We used to make the pipe out of steel. Before we made it out of steel, we made the pipes out of wood. We used to take trees and drill them out and bury them in the ground and put some mastic around the joints, and that's how they transported the gas to make this for the street lights okay, in the 1880s. I mean I've seen old wooden pipes that were dug out of the ground in Boston that were part of the old street light system of 150 years ago. Now we're going to plastic. And plastic — there are so many plastics that you need a whole course just to talk about all the different plastics.

But plastics — they always tell you they're corrosion resistant. They are, in the right environment. And they don't corrode the same way metals do, but going back to their oxides — but they coined another term, the — because the plastics people say plastics don't corrode, and the corrosion engineers knew that wasn't true. But they were looking for a better name than corrosion, or, you know, hot corrosion — I always call hot rot okay. It's corrosion — sort of a dirty term. They now caught — call it environmental degradation of materials. So if you want to talk about environmental degradation, certain environments will just destroy plastics okay. And it doesn't have to be a very sophisticated one.

I don't have a piece of Delrin here, but DuPont — did I tell you the Delrin story? Polyacetate okay, probably acetal — but it's basically a very simple polymer. And DuPont came out with polyacetal, which they called Delrin as their trade name, D-E-L-R-I-N, in 1958. There's a paper has 200 different solvents, and they said this is the plumbing material of the future. And they had 200 different solvents that it was resistant to. So you could pour any organic you wanted, any solvent you wanted down the sink, and nothing in your food was going to touch it. The one solvent they didn't check — water. I'm not kidding. You read this paper, they never checked water okay. And it turns out, if it's very pure water — in nuclear reactor water would be great, Delrin would last forever. But if it has half a part per million chlorine, it will start to decompose, and it will crack.

And so about ten years ago, there were — well, first of all, Hoechst Celanese, who made — had a large part of the market, not as big as DuPont — they had a 900 million dollar class action settlement. DuPont had a class action settlement, but it's classified okay — or it's not classified, but secret, confidential — but we know it had to be above a billion dollars, for all these plumbing applications of Delrin okay. But a half a part per million chlorine would cause the stuff to decompose. And people would talk about the exploding toilets. Well, they weren't exploding, but they would make — the valve that, you know, when you flush the toilet, the water closet — you know, all the water rushes in and flushes the toilet, and then you have to have this valve that lets more water in, you have the little float that stops everything. That valve used to be made out of Delrin. And most water — EPA standards, it's not potable water if it has more than 100 parts per million chlorine. Cambridge water is like 5 ppm chlorine — ten times what Delrin can support. You know those little blue tablets that they put in the toilets? They're basically salt tablets full of chlorine, and you put one of those in, you start seeing the blue color, and it's probably 3000 ppm chlorine, and those things will just destroy the Delrin within months.

And so what would happen is, the valve would crack, and they get 60 psi water shooting straight up against the top of the ceramic lid, and it would push the ceramic lid off, and they come crashing to the floor. People would hear this big crash and they called them exploding toilets. They weren't exploding, it was just the water pressure was knocking the ceramic cap off, and the ceramic was falling to the ground and crashing. Anyway, lots of floods. I made a lot of money off that.

Anyway, so when they tell you plastics are corrosion resistant, I always say, in what environment, okay. The corrosion engineers now define themselves as environmental degradation of materials. Metals corrode, but plastics and ceramics environmentally degrade depending on their environment. Everything will corrode over time, except gold — we find it in nature — platinum is usually pretty good. But if you look at just the earth, and you go to places that have been weathering away for a billion years, you don't find much except old worn-out stones.

Anyway, I look forward to your presentations. You can come and see me if you have some problems. If you got here a little bit late, here's the schedule for the presentations. Pick it up so you'll know when you're doing it. I'm sure I'll have Jerry email it around. A few of you haven't given me topics yet. I would like to know. You're at the later end of some of these presentations because you haven't picked the topic, you told me yet. But I'll see you. Simone will be here.