Okay so this lecture's gonna be talking about ceramics and glasses. So when you think about a ceramic and you just describe a ceramic, you're probably thinking about something that hard, waterproof, brittle, possibly opaque if you're thinking about dishware or dinnerware and when you think of a glass, you probably have similar properties. It's hard, it's brittle, it might be transparent, all right? And so ceramics and glasses are very similar materials, they're basically inorganic, nonmettalic solids, so that means that they're not based on organic compound, and they're not based on a metal, all right? But it's that it's actually an oxidized form of a metal, and the brittleness of this material comes from the fact that the way that these atoms want to arrange. They're bonded so tightly that dislocations or imperfections in the material cannot pass through the material, and a dislocation is what gives a metal its ductility but because the dislocations don't pass easily through a ceramic they tend to be very brittle. The difference between a ceramic and a glass is really primarily based on its crystallinity. We define a ceramic as a material that is based on this metal or non-metalloid forming an oxide or some form of an inorganic compound that has crystallinity varying from something that could be perfectly crystalline. So you might know, for example, quartz is a crystalline form of a ceramic, or it could even be amorphous. Now a glass, on the other hand, is defined by the fact that is has no long range order. It only has short range order. The classic glass would be your glassware that you would use, for example, in your window pane but glassware as we'll find out glasses can also exist in other materials for example even metals. When we start thinking about this things and we wanna look at the structure. What did we mean by crystalline versus amorphous? So crystalline material serve for example like I said quartz, has this long range ordering of the atoms. So I know is I go from one atom to the next atom to the next atom, where each one's gonna be placed. So it occurs on a regular lattice, we call that a crystal lattice. Glass, on the other hand, is a material that has no long range order, and so it is by definition amorphous, and it doesn't have a single melting point. It has what we call a glass transition temperature. So, ceramic is a term that comes from the Greek work keramos, which means pottery, and that makes sense, because the obvious application of early ceramics was in the making of pottery. We talked a little bit in the clay lecture about using kaolinite clay to form porcelain. Porcelain is the ceramic that forms when you fire kaolinite clay above 1,000 degrees C. What you are doing if you look at the clay structure is that as you fire it at very high temperatures, those layers of clay that had the water between them, the water is driven off and the layers actually form a chemical bond, usually a bridging bond, between silicon and oxygens across those layers and so, you're actually centering, or forming or a new compound. Now, this is an irreversible reaction. You can't go back once you do it. You can't add water and take a ceramic and turn it back into a clay and so, but it was in a very valuable reaction, and it was used to make all sorts of earthenware, and stoneware and we've used it, and we continued to use that reaction extensively in cookware. Okay, so in addition to ceramics being used in the home environment, ceramics are also used in technical applications. We call these technical ceramics. So for example, I might use a quartz crystal as an oscillator in a radio or a watch. I might use alumina or ceria as a compound to grind a surface, Zirconia. You could also have non-oxides. So for example, carbides or nitrides or silicides. A silicide is used commonly as the contacting material in microelectronic devices. Nitrides are used as a protective coating in microelectronics and then you could also have functional ceramics, things that are electroactive, multiferroic, piezoelectric. Those are big words and we're gonna talk about those in the future but those new applications of ceramic that have tremendous possibilities for harvesting energy, and converting energy from one form, say a waste form of heat into a useful form, say electricity. And glasses, now, glasses are very different materials. Glasses, as I said, are amorphous solids and they can be polymers, borides, oxides, it can even be metals. They all have a non-crystalline structure. The most common form of glass that you're familiar with is SiO2 or silicon dioxide. That's your window pane or your glass rods here and again if I take a glass rod that has just SiO2, that's what this is all right. The glass rod pure SiO2. It doesn't have a very low melting point. So for example if I took sand and I decided to build a fire in the sand and I came back in the morning, I don't have a big bowl of glass sitting there right. I still have sand and the reason for that is cuz the melting point of SiO2 is up around 1700 degrees C. Now my flame here that I'm hitting this with but it's only getting to 1000 degrees. It's not hot enough to actually melt this and so this SI02 doesn't do anything. Well that was the problem that the ancient Egyptians and everybody else faced was is that they had lots of sand around them, they had lots of SI02 but they couldn't do anything with it because they didn't have temperatures that were hot enough to actually melt it. So, the early forms of clay were in the form of obsidian. Obsidian is a volcanic form of glass. This is chunk of obsidian. It's very opaque. It has a lot of impurities in it. An obsidian was very useful man. They used it a lot for making spear points and other objects. It's very brittle, but it had a knack for taking a very, very sharp edge and so, you got tradesmen and became very good at knowing exactly how to flake obsidian to make beautiful spear points for hunting but again, this is a natural form of glass. They couldn't actually make the glass. They could just use it if they found a volcano. So if you go on to other forms of glass then you might say, well what other source of energy do I have that might make glass? And so the natural thing to think of might be lightning. Lightning can make glass, it makes what we call a fulgurite. So if lightning strikes the ground, it will actually make a fulgurite. This is a fulgurite. You can see it's a tube that was formed when lightning struck the ground and the ground melted. Now, what happens however, is that, as you can see, this is a really rough outside, so where the sand didn't quite melt and the inside is quite smooth where it all melted and it's hollow. This is actually what a fulgurite looks like when it's formed out of lightning strikes. Not quite like the Sweet Home Alabama version that Hollywood had of some nice little glass sculpture. So, that was another way in which glass could be made. There was a third way that glass could be made, by nature, that happened and that was if you had a meteor impact. A meteor impact, might get so hot, that it would actually form a glass and that was what was found for example, and the necklaces that were found in King Tut's tomb. All right. They had a glass bead in the middle of the broach. And it was that glass bead was determined to be several million years old, from a meteor strike that had happened in the desert. And it was dug up and the ground into glass. So, what made glass making possible? Well, what happened was is that in the Nile there's a sediment and it's called Natron. It's a sodium carbonate. And when you add sodium to glass, what happens is is that if I take that structure of SI and O and SI all the way down, that you have that network structure, that makes quartz so high melting point and very strong. If I add sodium in there, what happens is it actually modifies that network, it attaches to one of the sites and it stops the network from forming, because sodium just wants to form one bond with oxygen. At that point I've terminated all my bonds so my material becomes extremely low melting point. It will drop the melting point to 850 degrees C if I just add lots of sodium carbonate to it. Now, that's what they would do in ancient times is they would add sodium carbonate onto the surface of something that they had formed with glass and they would melt it onto that surface at temperatures, and that was called a faience. And it wasn't actually melting into an object of glass, but it was actually producing a coating that was a glass like coating on the surface. The way sodium carbonate work is that when you heat it up, sodium carbonate dissociate, it loses the CO2, and it becomes sodium oxide, and then that sodium oxide reacts would be silicon dioxide that form a soda glass. Now, that soda glass, actually has a really bad property, in that it's actually soluble in water. It breaks up the network so much, that it dissolves in water, and then it becomes basically useless. So, the Egyptians also figured out that they added calcium oxide, which is lime, so if you take lime stone and you heat it up. Right? Here's an example of limestone. If I take this limestone and I heat it up, then I'll make calcium oxide. If I added that to the glass, then all of a sudden I have this ability to make a soda lime glass. And what happens is the lime, the calcium oxide wants to form two bonds with the oxygen, rather than one like the sodium, and that adds a little bit of strength back to the network, enough that now it melts at a temperature which you can achieve in a fire, which is 1000 degrees C, but it also had the ability to not dissolve in water. So for example this is soda-lime glass, now how would I know that this is soda-lime glass and not quartz? They look very similar, they're both transparent and you wouldn't know it. Sodium has a weird property in that if you get it very hot, it turns yellow. So if the atoms get excited and they drop their electron back down again they give off a yellow light. So you will notice that when I was hitting this thing it had just a little bit of a touch of yellow, but not much on that flame. Right? Now watch what happens when I heat the soda-lime glass, what's going to happen is is that that thing is going to turn bright yellow, and that's because of all the sodium in there. Now it's all that sodium and all that lime that gives it the ability to then become molten. So, if I leave this flame on for a little bit of time you'll start to see that it's actually going to want to start to droop. And then it's actually going to start to drop, so I'm not melting the glass and that was the key as I actually drop that temperature down to a low enough temperature that I can melt the glass finally. And that ability to melt glass meant that they could finally start to manipulate glass. And so, I'm going to put this in water to make sure that it doesn't, all right, so. You've now seen the difference during solid lime glass and quartz. So, what's the history of all these? Well, around 3000 BC, they started making these glazes with faiences, and then somewhere around 1600 BC, they started with core wound vessels, so you can see in this image a picture of core wound vessel. Alright, now then around 1500 BC, by then we had glass in Asia, Western Asia, Crete, Egypt, Greece, all over the place. Somewhere around 900 to 600 BC, they started developing new methods in Greece for manipulating glass. So for example, you would take slum glass, that's where you put glass over a surface, and you heat it up and you allow it to melt into a mold. Or you would do a thousand flower method. And a thousand flower method, as you can see in this pot, is where you actually had a long tube of glass and you chopped it up, and then you laid down those pieces onto a surface and then you melted it all into a plate. And it came in the very beautiful form of a plate. Around, somewhere around 100 BC, glass blowing was developed in Syria and Palestine area, and the ability to do glass blowing meant that you could now rapidly produce lots and lots of vessels, because you could blow it into a mold and then you could take it out. Blow it into a mold, take it out, and you could start making lots of stuff. Well, the Romans took this idea and they love glass. So couple of things that they did, was one, it was discovered in Alexandria, that around 100 AD, that you can add manganese oxide the glass and that would make it colorless. So, it no longer had this really dark green color to it, and so the first thing they started with of course was to make lots of drinking vessels. And what's the interesting application there is if you think about it, before they did that, they had no ability to actually see what they were drinking. So you always looking into a solid ceramic cup you had no idea what it looked like, now all of a sudden you can see through it, and so this contributed to a great appreciation of wine by the Romans. The Romans loved glass so much that they made glass souvenirs that they gave out and were sold at the Colosseum during the gladiator fights, it became their form of plastic. They were the first to make windows out of glass, in which case they couldn't make a sheet of glass. So what they did was make a big bubble and pop it. And so every glass windowpane had a point on it where you could see where the glass rod was being made in that bubble form. They also made the first mirrors, and the reason they did that was for a corrosion reason. It turned out the ancient mirrors were metals, and they had a natural tendency to corrode. So when you first got a metal mirror, it looked okay, it was shiny. And then as you used it, it would corrode and it would look worse and worse. They discovered that if they put a glass coating over it, that prevented the corrosion of the metal, and so now the mirror lasted longer. And then they started looking at it further and further, and said well, we don't really need all this metal. And so they started just putting thinner and thinner layers of metal on the backside. And so, that became the very first mirrors is when you have a glass sheet with a very thin layer of metal on the back. So now if we go forward from the Roman times, then what you find out is that the glasses actually start to make a presence in Europe around 700 AD in the form of stained glass windows. And stained glass windows of course were part of the church system in the sense that it was a very inspiring environment to go into. They would color these glasses with different ways, and the early forms of stain glass were very crude. But then as time went on, they got much more developed in their ability to not only manipulate the shapes of the glass, but also the color of the glass. And as we'll see when we talk about gold, this was actually the very first application of nanotechnology, because they used gold nanoparticles to make the red color in stain glass. And then if you go further forward, what you find is is that around the 1300's and 1400's, Murano glass became very popular in Europe. And this was a glass that came from Murano, Italy, a little island near Venice, and the beautiful thing about that is they had access to extremely pure silica pebbles, and that's what they used to make their glass vessels, and so people fell in love with Murano Glass. So moving forward in history, there's an interesting speculation that the printing press, when it was invented, actually spurred people to start to question whether or not they actually had good eyesight because before that they didn't have to read anything. And so eyeglasses became developed in the 1500s, and that naturally led to the development of microscopes and telescopes since Galileo and Leeuwenhoek and all their off shoots from that glass innovations were incredibly important in our understanding of not only outer space, but also how bacteria and what not work on Earth. In fact in 1608 in Jamestown, the very first export by the Pilgrims back to England was glass beads that they were making there in 1608. When you go forward there's been a lot of interesting innovations in glass over the last several hundred years. Probably one of the most important things happened in 1959 when they actually invented a way to make float glass. Now float glass is where you take a molten bath of tin and you pour the SO2, the soda lime glass on top of it. And the advantage to that is that you get an extremely flat surface and you can make very large surfaces of it. And so this has been utilized in all your window panes. So the window panes that you have now are all based on float glass. In the 1970s there was a really strong push to figure out how to reduce the impurities in glass. The driving force behind this was the idea that we wanted to try to use fiber optics to communicate. So fiber optics is a cable of glass. It's a very thin hairlike fiber of glass, and it had to have transmission capacity of about 95%. Now if you think about it a window pane, right now that's an eighth of an inch thick has a transmission of about 95%. So that's great. However, with a fiber optic cable, you had to make that cable 16 kilometers long, and still have 95% transmission. That required you to make it extremely cured. If you've ever sat down and said, you're at the dinner table with your parents and you look at their glass table from the side, it looks green. And the reason it looks green is because the glass has got a lot of impurities in it, primarily iron, and that's causing it to be opaque. By removing those impurities the glass can suddenly transmit light over much longer distances without the attenuation due to the impurities. So there was a lot of work done in the 70's to manipulate glass by making it into a chemical and distilling it and then purifying it that way and then turning it back into an oxide and then making your glass fibers. And that had a big, huge impact on the ability to have the internet and what we know today about modern manipulation of materials for telecommunications. So one of the challenges with glass has always been, we knew it had high temperature melting points and it could be manipulated for those applications. But how do we make it strong? It's always inherently brittle. Well glass is actually very strong in compression. So if you can find a way in which you can put the glass into a state of compression or the ceramic into a state of compression, then it would be very strong. And so for example, that's exactly what you do with a corning ware plate, where you actually have the inside of the corning ware plate shrink faster than the outside, and that puts the state of the outside into a state of compression and makes the plate very strong. Another way that people like to manipulate glass is to change its color. So for example, if you add different impurities to glass it will make it different colors. For blue, you could use cobalt. For red you can use Metallic Gold or Copper. If you want to make it yellow, then you might use Silver Nitrate. Even Uranium was used to make it yellow, of course it has its drawbacks if you have radioactive glass. If you wanted to make it white, then you might add Tin Oxide with Ammonium or Arsenic oxides, and that tended to make it colorless. So there are lots of ways in which people learn to manipulate glass for its color. The other thing that people would do is that they would manipulate the properties of the glass. So, for example, if I want a glass that doesn't have much thermal expansion. Right? Then I might add Boron Oxide, all right? And that's what we call Pyrex. And the advantage to that is is that when I heat it up or cool it down, this is made out of Pyrex, it doesn't expand very much or shrink very much. And that means that I can actually expose it to very large temperature differences without shocking it to the point where it breaks, right? So we like Pyrex very much for cooking applications, or places like that. So people would actually add lead oxide to glass and the advantage there is that it increases the dispersion and so it makes it look very sparkly and so we like leaded glass for goblets or for chandeliers. Other ways in which you manipulate glass might be, you would add lanthimum oxide to the glass and what that does, is that's a rare earth. And it's used for camera lenses and for telescopes. And it again, changes the optical properties to make it ideal for taking pictures with, or for observing through a telescope. So as you can see, there's lots of different forms of glass, even aluminum oxide is a glass, and that's the glass that you see every day when you deal with something that has fiberglass in it. What you're going to learn more about is that glass can be manipulated not only for its structure and its properties as a material for fiber optic cables and things like that, but it also can be used for energy harvesting. So there's new, functional forms of ceramics -- these are not glasses, these are crystalline materials -- that can be used to manipulate or convert energy from one form to another. We call that a transducing action. So even though glass has got a long history of being used, the future for ceramics is incredibly bright as we go forward because of these new applications for glasses and ceramics.