SMS_S2016_05

You need to ask questions or I can't digress. Okay, I've heard these lectures before. So the schedule will be: I'm lecturing today, Dr. Belmar will be tomorrow. I'll be in Dallas, and then I'm going to do three days next week. He'll be here on Thursday — that's the day he could do it. I think he may be a fair amount in the next week, but he hasn't given me a schedule because he's been out of town. But we'll try to keep this posted for you. Just to let you know, I think this brings me up to seventy-five percent of the way done by the end of next week for me, and he's going to be at least fifty percent done by the end of next week. So it moves along fairly quickly when you meet every day, and so far as that goes. But you'll appreciate it in May when you don't have a course, right? You don't have to worry about it.

Last time we talked about, there are physical limits to materials properties, basically based on the bond strength of the atoms. I talked about mechanical strength, but it also melting temperature. And the highest bond strengths we have are about three electron volts per atom, which — can't remember — that's around 250,000 joules per mole or something like that. You can work out electron volts per atom to joules per mole — all you have to do is multiply by Avogadro's number, but any hint, convert from electron volts to joules. But in any case, there are limits to the properties of materials, and the Ashby plots kind of show you that. And he usually goes six, or may[be] six, five or six orders of magnitude one way by five or six orders of magnitude the other way, and all materials sort of fall in those ranges.

And if you want to be a materials scientist, we can explain why. Okay, we can explain why many of the ceramics, the ionic and covalent bonded materials, are transparent. They don't have free electrons. No metals are transparent, except for the one transparent metal we know of. There's no Star Wars fans or Star Trek fans? Transparent aluminum — that's what they held the whales in, the Voyage Home. You don't remember Scotty deciding to use transparent aluminum? Okay, anyway, so go watch The Voyage Home. They had to save the whales or something. Anyway, so metals have free electrons and that's why they don't transmit light. They actually absorb light with all those free electrons.

Anyway, so there are limits to the properties of materials. And then Mark Twain once said "rumors of my death are greatly exaggerated," but in fact he was speaking on behalf of metals when he said that. Most people don't know that he was talking on behalf of metals. But in fact, metals are here to stay. I showed you a Speech [Smith?] plot where he predicted the demise of metals because composites and ceramics were going to take over the world, okay, and plastics. Well, that hasn't happened, and believe me, we're going to talk in this course about why it's not going to happen, based on the limits, the properties of the materials. Okay, and it's true — and we haven't talked about this, but this is what we're going to go into today — stone, cement, and steel are the only members of the billion-ton-per-year club. I guess I could show you that right now. Well, I won't show it to you right now, I'll show you a little bit. We'll get to that today.

If we look at something like strength, which is what we're interested in, structural materials versus relative cost — and remember, aside from externalities, which is becoming the number one reason for selection of materials in many cases, we've always had availability and cost as two of the issues. And so this is Ashby's plot on cost. Again, five orders of magnitude if you plot it on a — and so you have to plot it on a log-log scale. But low cost is down this side: brick, stone, concrete, and here's mild steel. And it turns out there is a relationship between the material we use and the cost. Okay, and so here, your steel, brick, and stone and concrete are the billion-ton-per-year club, and nothing else comes really very close. Okay, all the plastics, we'll see, are about 300 million tons per year. Okay, and so the plastics are in here, and they're more expensive, so we use less of them.

The ceramics, the fine ceramics, have tremendous strength. If we plot something else, they're going to be way down at the bottom. What's that other thing we plot? This is the fracture strength. Ceramics have lousy fracture energy, okay, which is zero. So I don't have — that's the wrong plot. Fracture energy is same as toughness, and I'll show you the toughness later. Okay, so it turns out, some of these other things — I mean, ceramics can be fairly inexpensive, but they have lousy toughness, and so therefore we have to be careful how we use them. Although stone and concrete are ceramics, so there's exceptions to every rule, I guess.

Now, there'll be a handout — this comes out of Ashby's book. His chapter 2 is the price and availability of materials. And if you look, he's got a plot in there of the abundance of the elements in weight percent in the Earth's crust. Okay, actually, atmosphere, oceans, and crust. Oxygen is the most abundant, silicon is the second most abundant, aluminum, iron, calcium and magnesium. And it turns out, I'm going to show you, that these actually are in those billion-tons-per-year category.

If you look at the oceans, obviously you have hydrogen and oxygen, and this is weight percent. And it turns out virtually everything is in the ocean. Okay, there's a certain solubility in water for everything. You can mine uranium from the ocean, you can take gold out of the ocean — a little pricey, okay, to extract it, because it's fairly dilute. But the oceans are fairly large, and there's a tremendous amount of most things in the ocean if you want to pay the price.

And of course, we generally know what's in the atmosphere. They never tell you what the five percent component in the atmosphere is. Anybody know what the five percent component gas in the atmosphere is? It's called water. We have rain, clouds, snow. And typically, if you start looking at humidity tables and temperature versus humidity, you'll find down here near the Earth's surface there's about five percent humidity, or five percent water in the air at like 82 degrees Fahrenheit. One hundred percent humidity is five percent water. Now we don't have a hundred percent humidity, but in any case, there's a lot of water up there.

I once wondered — I don't know if you've ever wondered things like this — see, these storms come across the country, dumping all this rain. I thought, how much water is up there? And if you start calculating what the thickness of the atmosphere is — well, the thickness of the atmosphere that has clouds — anybody have an idea? Now, if you were a Howard Hughes fan, you would know this. Howard Hughes developed pressurized airplanes so they could fly above the clouds, so that you wouldn't have to worry about the weather. You can fly through the clouds and get above the clouds, but you have to get to high enough altitudes that you have to have a pressurized aircraft. So one of the things that made Howard — you didn't watch the movie about Howard Hughes? Actually, I'm not sure that's where I got this, but it's true. It turns out he essentially was one of the first people to decide to try to build a pressurized aircraft. Before that, the little biplanes and stuff, they go up a few thousand feet, 5,000 feet or something, and when they had bad weather you couldn't fly. But by going up to 10 or 15,000 feet, you can get above the clouds. Now there are clouds that go even higher — some of the clouds go to 40,000 feet — but if you just take 10,000 feet of space that might have — and the humidity is not five percent, it may only be one percent moisture in the air — and you start thinking about one percent times 10,000 feet, that's a lot of rain. Okay, you can dump feet of water. You know, those clouds still got plenty of moisture when they come from the Pacific all the way to the Atlantic.

So anyway, here's the relative abundance. And there's other numbers for abundance. It turns out, if you look — a geologist would look — whether the Ashbys did the other plot too. But if you look at the abundance in terms of kind of marching across the atomic number, periodic table, if you will. Of course we have a lot of hydrogen in relative abundance, but it decreases as we get to a larger and larger atomic number.

Does anyone know where the elements were formed? In the Big Bang, at the time of the Big Bang, the elements didn't exist. Where are they? Where are the heavy elements formed? They're not formed in the Sun, right? Are we not — there in the core of the Earth? But it turns out, when you have a supernova explosion, it's such an energetic event that that's where nature basically has its atomic reactor, where it has enough energy and things are slamming together so hard that you actually take light elements and make them into heavy elements. Now we can do that at billions of dollars per gram in some reactor here on Earth, but in the heavens, it's basically done in the supernova.

It turns out, if you look here, iron has this sort of interesting peak above and other things around it. Iron and nickel are very high abundance. Meteorites are typically iron and nickel — high in iron and nickel. Does anyone know why this is? Any nuclear engineers in here? Because if you look at the stability of the atomic nucleus, turns out atomic number 56 is the sweet spot for the nuclei. Very stable nucleus. You don't have a lot of problem with radioactivity in iron compounds and stuff. The nucleus is very stable, and as a result, when the supernova occurs, you produce a lot of iron and nickel. This basically is the productivity curve for supernova in producing heavy elements. We don't produce them on Earth, we don't produce them in big stars — we only produce them in big stars when they blow up. Okay.

Now, I talked about the fact that there was a lot of oxygen in the crust. Most of the metals, or most of the elements in the periodic table, are present as either oxide or sulfides because that's more thermodynamically stable. And as a result, one of the problems with metals — which, I think metals are wonderful because I'm a metallurgist, but metals have a very high price to pay to get them into the metallic state. They tend to exist in an oxide or sulfide state. Aluminum oxide is known as bauxite — the ore is called bauxite. It's mostly Al₂O₃ plus OH. Okay, it's got some water and stuff in it, but basically it's very stable. The free energy of formation of aluminum oxide is very high, and it takes about three hundred gigajoules per ton to produce aluminum.

Plastics on the other hand are about a hundred gigajoules per ton, and most of that is the energy content of the plastics. Essentially you could have been using that plastic — you could have turned it into a fuel to burn in your airplane or your car. And a lot of that is the — I guess UK means — to be able to use it as a fuel unless you're recycling it. We can recycle plastics fairly readily by just burning them up, because they are a fuel.

Copper is very high and it's going even higher. Does anyone know why? Something called entropy. Okay, copper ores are not very concentrated. In fact, anyone know the largest copper mine in the world, or actually the deepest one in the world? You fly over it sometimes as you go out of Salt Lake City Airport. It's about two and a half miles deep. Okay, it's the Bingham City mine, or — Bingham Canyon or something. I can't remember. But Kennecott Copper owned it, now owns it. It's been mined for a hundred years — they just kind of keep digging it deeper and deeper. The ore there is less than one percent copper. Okay, I think it's like a half percent copper. There were ores in the Belgian Congo, which is now — as I — year, it was the Belgian Congo in the 1950s, and there were ores that were six percent copper. We've just depleted all those rich copper ore reserves, and so copper takes lots of energy. And we do essentially mine for copper. We get a bauxite that's very rich, we can get iron that's essentially pure iron oxide. Copper is dispersed at very low concentrations, and therefore you got to overcome a lot of entropy to get it.

Zinc is usually — well, now zinc is usually a byproduct of other things. Steel — there's iron ore all over the world, because steel is one of the most abundant elements. Glass, cement, and things. Anyway, there's a list here you'll have, of the energy content. And as a result, people like to think, oh, aluminum will overtake steel. No, not in price, okay.

Student: [inaudible question]

Well, it depends on what property you're talking about. Corrosion resistance — I mean, things that take a lot of energy often give up — well, they will give up a lot of energy to go back to their oxide state, and so sometimes they have corrosion problems. Now, it turns out not to be true in aluminum, because it forms a nice protective oxide skin. Tends not to be true in titanium. It turns out the Achilles heel of iron, of steel, is corrosion. And steel's got, you know, 50 on this scale, okay, whatever the scale is. So zinc, foot working and puts working every now and then. Okay, so there's other factors.

Okay, the only factor I can draw a correlation to is price, because energy is the price. Okay, but there are other correlations. I mean, the Achilles heel of metals compared to ceramics and polymers and plastics is they corrode. Plastics — you know, you throw your plastic baggies away and they'll be floating around in the ocean for the next millennia, okay, or longer, 'cause bugs don't even eat them very well. You throw metal in the ocean, unless it's a very corrosion-resistant metal, it's going to corrode in that environment. You throw cement in the ocean, it'll be there probably a million years from now — well, actually not a million years. But in fact the cement originally came from the ocean. It was formed as limestone in the ocean as a deposit. It precipitated out of the ocean. That's another story. So we actually have to get into the details. I guess I don't have a simple answer to your question, okay, other than there's a price correlation because energy and price are basically fungible. Okay.

Then there's a handout that is the summary of this course. Okay, I don't know if we've — I mentioned this in this class. Anyway, this is a handout that — I was on a committee once in the early two thousand[s], I think this is — I don't remember with the — it's like a 2002 or 2003 copyright. This is National Academy of Sciences report, or National Research Council report of the National Academies, "Materials Research Needs for the Defense Department in the 21st Century." So there were about 40 of us on this committee, and people were talking about all these fancy new materials and how they were going to do all these wonderful things.

And they — might know how the National Research Council works, or the National Academies works, or anything about those things. Okay, so Abraham Lincoln chartered the National Academies of Sciences in 1863. And there were about eight or ten people had this thing, and many of them were politicians but somewhat scientists or whatever at the time. And the National Academies is not part of the government, but they have a charter from the federal government, and their charter is to advise the government, as a quasi — called a quasi-governmental agency, whatever that means. But their job is to advise the government on matters of science and technology, and now medicine. And so the National Academies went plodding along until about the 1950s or 1960s, and then in the mid-60s they form the National Academy of Engineering, a few years later they form the Institute of Medicine. And so the National Academies — National Academy of Sciences — you first of all, you have to be nominated by people who are already in the club, okay.

As Professor Sik Ellie [Suresh? Sadoway?], who's — best way used to say, it's more important to not be in the Academy than to be in the Academy. I mean, once you're elected to the Academy, you really don't have to do anything, although you'll be asked to serve on committees. But even if you're not in the Academy, you'll be asked to serve on some of these committees, and some people serve on these committees because they hope that this will help them get elected to the National Academy. Okay, so the other thing about the National Academy, it is literally an old boys' club. And by that I mean there's less than five percent women. Okay, now they're trying to change that. They actually have quotas, so if you actually happen to be a fairly highly qualified woman, there's a very good chance of being elected to the National Academies. They also have quotas against academics, because it turns out the National Academies are about forty percent, 45-percent academics, and they have a quota — they don't want to be more than thirty percent academics. So to be a white male at a university, the chances of getting elected to the National Academy are near nought. They still — it's an old boys' club, and it's still like a lot of old boys.

In fact, talking about old boys, I think one year the average age of election was like 73, okay, because they have the limitation. They just announced who got elected, like a week ago — it's usually in February for the National Academy of Engineers — and they elected 80 people. Okay, there's a total of, about, in the 22 foreign associates, there's only about 2,000 members of the National Academy of Engineering in the country, and there's about two million engineers, so you're in top one out of a thousand, sort of, whatever that means. But as Professor Kelly says, it's more important — a lot of people are very envious.

For example, I actually was elected when I was department head at age 47. Not the youngest, but I'm one of the younger people to get elected to the National Academy. And when I stepped down as department head, Professor Suresh — who's now president of Carnegie Mellon, and became dean of engineering here, and was a candidate for president of MIT — Professor Suresh would take me to lunch about once every three months for the first year and a half or two years after I stepped down as department head. And at the end of the lunch, the National Academy always came up, because he was not a member yet, okay. And he knew that, to a certain extent, he was afraid that I might blackball him or something. Well, I'm not that type of person to blackball somebody. But it was interesting, when the people have been nominated, when the thing comes out for the first comment, which is in the summer — he kept the schedule. This is all supposed to be very secret, for the nominations and the elections, okay. But he knew it all the time, what was going on. And he took me to lunch in that July or August of 2002 or 2003, whatever it was — and because he knew he'd been nominated. He'd been nominated by my predecessor, the department head, and you have to be nominated by four or five people, and you can't have everybody from the same institution. They did a lot of politics — there's a lot of politics, anyway. And so he took me to lunch, and the National Academy came up just like he did every time. And once he knew that this comment stage — I never got another lunch. He was department head for another five years, but I never got another lunch, okay. But I mean, I got free lunches for every quarter for about a year and a half. Waste of time.

But anyway, so the National Academies also have the National Research Council, which has been around since around 1910 or so, and they do studies for the government. Congress might commission a study, or the Defense Department, someone, some Undersecretary of Defense wanted to know, what are we going to spend our money on in the future, and rather than listening to their own scientists. For example, the US Army about five years before this had spent over a million dollars trying to study what materials — what was the material that the US Army was going to purchase the most of over the next 20 or 30 years. And they came up with the study that I could have told them, and I wouldn't have taken 10 million dollars to study it. You know, it was — it is steel. Why? Well, you don't throw stones at the enemy, okay. You shoot missiles and things, or you bring a big tank in and stuff. And there's a reason why we use steel, and we'll talk about all that.

But anyway, so I was on this committee and they were talking about all kinds of fancy new materials and glamorous technology materials. And they asked us all to write up our stuff, and they have editors down there that will put it together in a big report. And these reports go to Washington — well, they're in Washington — they go to the Capitol Hill, and the congressional staffers read these things and they'll influence the funding and things like that. So it's worth spending some time on these things. But you meet a lot of people. This is a division of engineering and physical sciences. So anyway, I wrote up my stuff, and I basically wrote up what I've been teaching my class, okay, in three or four pages. And it basically said the old traditional materials are important. Well, this is not what they wanted to hear, and it didn't fit into anyone else's talk. So this became an appendix, okay. Doesn't have my name on it, but I'm the only person who contributed to it, okay.

So this is a summary of what I've been teaching, and they called it "Integration of Material Systems and Structures Development." But it's not — it's all of my stuff, impacted [by] stuff I've been learning from other people from time to time. But here's a plot from Jack Westbrook — Westbrook is a graduate of this department. He put this together. He's retired — at that time he was retired from General Electric. I gave a reference as they wanted it. I emailed Jack, and he was already retired then, but he put this together [in] 1962. So these are 1962 dollars. It was an internal memo at General Electric. And it shows structural materials, dollars per pound, versus pounds per year that were used.

And here's stone — I can blow it up for you a little bit — so here's stone up here, the most highly used material in the world, and it has been for millennia. Okay, here's cement, here's carbon steel, he's got alloy steel down here used at about one-tenth the volume. Okay, these are large numbers — 10 to the 11th pounds per year. That's a lot of material. These are also market size, okay. This was a billion-dollar market in 1962, by a hundred billion dollar market today. But in any case. And you come out here in the end, well, diamond is a structural material. You may not build buildings out of it, but it's a structural material. You're using it for mechanical properties or its optical properties. If you — well, I'll have a diamond, but you know, people use it for optical front[s]. But as a structural material, it has important uses. And remember, this is General Electric report, and at the time General Electric had a near monopoly on man-made diamonds 'cause of Tracy Hall among other people, okay, who'd invented the process to make man-made diamonds. Okay, cemented carbides are structural materials, just like diamond. Not used, you know — a hundred dollars a pound. Diamond is — back then was ten thousand dollars a pound. It's about four hundred million dollars a pound now or something like that. Ashby's got some updated prices and stuff. Anyway, you could read this.

But there's also something in here, and I've already told you this other thing that's in here, and that's the value of a pound saved. And the value of a pound saved over the life of the vehicle is twenty cents a pound for ships and railroads. Anybody remember what it is for automobiles? Two dollars a pound. And aircraft, 200. And spacecraft, 20,000. So I've already used those numbers a number of times, and you can sit here and debate — some of these numbers have changed by a factor of two, and we will talk about some of these things.

Two hundred dollars a pound — I remember the first LGM thesis, the LGO thesis. The first round of students, one of them went to Boeing, and they actually got the proprietary Boeing number for the value of a pound saved on an aircraft. It's sort of proprietary, but they somehow got permission — or they didn't get permission, it showed up in their thesis. One hundred eighty-eight dollars a pound was Boeing's number. Pretty close to 200, right? Yes, exactly. I used to use two dollars a pound for automobiles 20 years ago, 25 years ago, and that was when fuel cost — in fact, if you read this article, it was early 2000s, I talked about fuel that, dollar fifty a gallon. We haven't seen that for a while — we might see it again, but you know.

And I gave a talk once about — in fact, I think I reference in here Peter Bridenbaugh, okay, and I do, okay. So, Peter Bridenbaugh, private communication, October 11, 2001. So I went to a conference, okay, and there was Peter — graduate of this department, senior executive vice president [of] Alcoa. He was in charge of all the stuff to make aluminum out — easy without — he okay. And that was all under him. And we were both in the same session, and I got up and gave a talk sort of about this type of stuff, and I said — I knew he's in the audience — so I said, you know, all-aluminum vehicles, automobiles, will not really be economical until gas costs about four dollars a gallon. Because I knew I didn't want to offend him, okay. I was syrup-upping it. I'd used two dollars for four years in the 1990s, but this was early 2000s and stuff. Peter came up to me at the break, he says, no, Tom, it's two dollars a pound. He was using the same number I was, okay, because that's what the real number was back then.

But it does depend on what the price of fuel is, and it could go up to four. But it's not 200 and it's not twenty cents a pound. But you're absolutely right, when you have fuel that's varying by a factor of 2, then this number has to vary by a factor [of] two, because it's based on the price of fuel. For automobiles, it's based on price of fuel and drag in the water or on the railroad tracks. The friction on the railroad tracks, or the drag in the water for — and the price of fuel for ships. And here for aircraft, it's based on the price of fuel, but per hundred thousand hours for a commercial aircraft. And for spacecraft, it's just again, it's sort of the fuel to get a pound in orbit.

And you go look at the numbers back when we were shooting rockets off in the Apollo program. It was costing five to ten thousand dollars a pound in the 1960s to get a pound of payload in orbit. And the purpose — if you go back and read the 1970s documents — the purpose of the Space Shuttle was to drop the price from ten thousand dollars a pound to a thousand dollars a pound. And anybody know what this — I think I said it in here, I know what — if you look at the actual space shuttle in its history of 30 years of use, what its actual cost of a pound of payload in orbit — remember it's supposed to drop the price by a factor of 10, that's why they told Congress when they asked for the program to build a space shuttle. It was about 35[,000] — 30,000, it could have been forty thousand, but because of the Challenger, the disasters and the efficient management we have at NASA and all these other things. The program was supposed to drop the price from ten thousand dollars a pound to a thousand dollars a pound, actually came in at thirty thousand dollars a pound, or 40,000. I don't know what it was exactly. I'm sure it depends on how you do your accounting, right?

Student: [inaudible question about electric vehicles]

The answer is no, but now I'll speculate, okay. First of all, the electric vehicles using electrons — those electrons actually have to come from somewhere. And if I look at the cost of a — they want as either a fossil fuel watt or an electric watt — you know, electric watts cost more, right, by about a factor of 50 to 100 percent more. That's just price of wall plug energy for electrons. So electric vehicles are much more efficient in their use of energy, but they're using a more expensive form of energy, namely with electrons. And it all goes back to what was your source of energy. Hey, if you got solar energy, and you can get solar energy down really cheap — but right now solar energy is still costing twenty cents a kilowatt hour if you're a regular consumer, right? So there's still problems here, and people don't always look at the whole system cost. Okay, so in some ways you can run the math and say electric vehicles are very efficient and cost effective, but if you look at the total cycle price right now, they're more expensive.

Now, I'm rebuilding my house. In fact, if you went to my house right now, they just started digging out the basement, okay. This is 80-year-old home. And if you go up to the first floor, the second floor, you can see right through the house. They took all the walls off — all you see is studs, okay. But as they're rebuilding it, I'm going to have three electrical outlets at my driveway. I don't have an electric vehicle now, and I couldn't buy an electric vehicle because I have to pay one or two thousand dollars to put — in my driveway or my garage. Well, since I'm having the whole house rewired, because I've taken it down to the studs, okay, I'm putting in three of them, as I traditionally own three cars — one for my wife, one for myself, and one to go in the shop. No, it's actually the best of our philosophy. When my kids were around, we had three cars — we don't want to drive them to high school. But now we're empty nesters, I have one so that we can go to the shop.

Anyway, so you can read that article about the price and availability of materials. And I talked about things — did you know how important are materials in terms of manufactured product? Not very. Did you know what the value of materials are in a manufactured product? The most materials-intensive products that I know of are pipelines or big steel transmission towers to carry, you know, 250 kilowatts of energy. Right now kilowatts — kilovolts. And those have about thirty percent of the cost of the project is the material cost. This is all in the thing, okay. So I mean, it's just a slide I've made from stuff that is in there. Automobile or an aircraft, typically materials cost about ten percent. If you're talking semiconductors and spacecraft, your materials cost are nothing, okay. It's mostly cost of — material.

Where that paper will tell you, that if you just kind of average — materials costs as being about ten percent of the value. Then you're going to have another — I might as well read it. Just can't remember it. I had this all worked out once. Here's the table. Raw materials are ten to twenty percent of value [of] manufactured product. Design and engineering is ten to twenty percent, unless you're designing a hula hoop, which doesn't have a lot of design and engineering. Fabrication — forging, machining and all that stuff, those things you mechanical engineers do — that's twenty to forty percent of the manufacturing costs. Non-destructive testing and quality control can be ten to twenty percent. G&A, you know, the accountants and the HR people and everything, is ten percent. And profit, if you add all this up with the ranges up above, is either plus ten percent or minus ten percent. You can either win or lose on this in this game, right? So but those are the approximate numbers.

And so, you know, I'm not really popular with the other faculty in the materials department when I start putting up numbers like this, because it says, gee, materials are only a small fraction of the manufactured cost. When I'm a manufacturing engineer, folks, I'm not really a materials scientist. I'm certainly not [a] materials scientist. I'm somewhat of a materials engineer, but anyway. But anyway, you'll find some principles in there that I think — they sort of go against the grain. And out of the 40 people on this National Research Council committee, well, maybe that's why they don't ask me to be on the committees anymore, okay. I tell them things they don't want to hear, okay. So what can I do? I have a captive class of students, and so you guys have to hear it.

But to give you an example — and I think I reference that example in here — the US Navy was worried about the weight of aircraft carriers. Aircraft carriers gain 250 tons a year — 250 tons a year. I mean, I gained a little weight, but no, hear me, if your spouse is giving you a hard time about, you know, gaining weight, tell — I don't gain as much as an aircraft carrier each year, okay. About aircraft carriers, the Nimitz class started like 60,000 tons and sixty-five thousand tons, and it was up towards 90,000 tons 60 years later. And turns out most of the weight is up at the top. I mean, you know, for me it's in the middle, but it's up at the top. It's only at the top if I'm lying down, I guess. Anyway, in any case, the aircraft carrier gains 250 tons a year, and they needed to make it lighter weight because it was going to cost them 50 million dollars to design the new hull.

And so around 2000 they gave a million-dollar contract to Newport News Shipbuilding to do a feasibility study of, what if they used a 65 ksi strength steel rather than a 36 ksi steel or 50 ksi steel, which was traditional shipbuilding. What if they went to a higher strength steel — how much weight did they save, and what would be the total savings? Well, at that time HSLA-65 steel would cost you about a dollar a pound, two thousand dollars a ton for the plate. And they determined that they could save — it would cost them, manufactured, ten dollars a pound to fabricate the steel. I wish I still had the report. Anyway, lost in my office somewhere. But that's ten percent — the material cost was ten percent. I could have done that for less than a million dollars. I would have given them that report for half a million, right? It's just a rule of thumb, and these rules of thumb are not bad.

Now, if we look at structural materials usage — this is something I put together for this course a couple years ago. It turns out — well, I gave you the future of metals thing the other day, yesterday — but steel right now is about one and a half billion tons a year, and the next closest metal — remember, I said steel is 95 tons out of every hundred tons of metal that was made in the world. The next closest one was aluminum at 1.75 percent. Turns out, here it is, 45 million tons of aluminum is what the Aluminum Association says the worldwide production of aluminum. Go down. The next largest is copper — that was 1.2 percent of the total. And you go down here, and I just picked off some others. If you — I Googled scandium once — worldwide production of scandium is 2,000 tons a year. That — what do you use scandium for? You might know — no one from an aluminum company. Baseball bats, okay. It's an alloying element. The Soviets developed [it] to get very high strength aluminum alloys, and the highest strength aluminum alloys go into baseball bats, okay. That's another story.

But I also estimated, okay — you can actually get off Googling a little bit, you can get the total amount of cement or plastics. Plastics are three hundred million tons, twenty percent of the volume — now, not actually, not twenty percent of the weight of steel, the volume is a lot larger because the density of plastics is a lot less. Actually, weren't we — Pat, well, now I'll pass these around next time when we talk about some other things. I always — forgot to think. But cement is 2.2 billion tons. And stone — this is just my estimate, 'cause stone is used in — it's used in cement, okay, Portland cement. It's used in railroads — put it down as the foundation before they put the ties down and stuff. I mean, a lot of weight goes into all those railroads, okay. They — you know, go look at the Stata Center over here, not the Stata Center, but the new nanotechnology building, go look in there, they're putting stone in the bottom of that. Crushed stone, okay. There's as much weight in stone there as there probably is in concrete right now. But stone's used for lots of things. It's not always the structural material, but it is a structural material. I've estimated there's probably six billion tons a year of stone, okay. It's the cheapest material, which is why we use a lot of it. There is this correlation between price and the amount of material that we use.

Now, there are other relative costs and density. It actually gives you some of these numbers, and what happened to my focus here is — and these things will be in the website if you want — know if I copy them down. If I use iron as my metric for these metals, and for both density — you know, normalize the density and the cost of iron — aluminum, which has three times — or has six times the energy content, has five times the cost. Okay, approximately. You could argue maybe it has six times, but approximately there's the ratio of the energy cost in the material, okay. And it is much lighter. And that's what I was going to pass these around. But we'll pass around — is a bar of aluminum, there's a bar [of] magnesium, there's a bar of zinc, it's about the same — some titanium, nickel and stuff — and you can feel the difference in density. Magnesium is really light, okay.

[Tom passes around sample bars of various metals.]

Yeah, it turns out — I told you it's two hundred dollars a pound for an aircraft. That's for the whole aircraft. Or it's two dollars a pound for an automobile. If I put the aluminum on the sprung weight on the wheels, or on the brake pads, it's worth about ten dollars a pound, okay. And I have a slide that will probably — I'm a put up sometime — the faster something goes, the more valuable saving weight is. And so all this density stuff turns out to be very important, and aluminum is a very important material. It's more expensive than steel, but it has a tremendous advantage over steel in several ways.

If we go back to this stuff: the billion-ton-per-year club due to cost — I've already shown these guys are the lowest cost materials, that's why the billion-ton-per-year club. Availability — well, you know, platinum is a wonderful high-temperature material, but the cost is not so great and the availability is not so great, okay, and those two are related. Strength — we're going to talk about strength, but we have the Ashby plots, and strength can be all over the place. Portland cement's not that strong, but it's cheap enough that you can — toughness. Well, the metals win here, okay. This is why metals are important — 'cause of toughness. Portland cement, it's not very fracture resistant, okay. Steel is recyclable too, okay. Steel is like eighty percent recycled now. Aluminum's like fifty percent recycled, and they're trying to get aluminum up to seventy or eighty percent. What's concrete recycling? Now, almost nothing. And it's 2.2 billion tons. You want to solve a world problem that's coming up? What are we going to do with 2.2 billion tons when it comes back after, you know, useful life? We're going to have some pretty big landfills. Now actually we'll fill in the ocean — we'll have a lot more dry land, right, since all the water is going to rise.

High-temperature capacity. Corrosion resistance — I put this in parenthesis 'cause steel's Achilles heel is, it corrodes. It wants to go back to iron oxide or iron sulfide, and it will, and it does, and it helps us to produce more and more steel each year to replace the junk. Hey, they just dug out my basement and went home yesterday. They just dug it up — cast iron pipes, sewer pipes. Good thing I dug up the basement — I was going to have to do it again sometime in the next ten years, because those pipes have been down there for 80 years. They're not much good, okay. I was discussing whether they should put in plastic, because if I put plastic sewer pipe in, it'll be there 150 years from now, and I may not be alive by that, okay.

So every material has its own niche, and there are multiple niches. But these three materials are used in extremely large volumes because they have an interesting combination of niches. And remember, number one is the externalities, number two is price, number three is availability, and then there's all kinds of other things. And yesterday's conclusion is, material selection is a multi-dimensional problem, okay. And I was going to go through — I have grocery shopping in here, and we're going to talk next time about packaging materials. Can be plastic, can be paper, can be composites, can be aluminum, can be steel. I got some chili with beans in here in the steel can, but they have to paint that can on the inside, because otherwise it would corrode just like my sewer pipes, even faster than every 80 years, okay. So anyways, we'll finish a minute early or two minutes early. And Unseen by has a question. Okay, so Dr. Belmar will be here tomorrow. You got me off my treat, okay. To this day, I'll be back.