1 00:00:16,015 --> 00:00:19,786 This is a great day. 2 00:00:19,786 --> 00:00:23,523 We're having our second lecture on glass, 3 00:00:23,523 --> 00:00:25,725 and we've got a demo-- 4 00:00:25,725 --> 00:00:28,561 where did Peter go? 5 00:00:28,561 --> 00:00:31,731 So we've got a demo coming up for you 6 00:00:31,731 --> 00:00:35,068 from the director of the glass blowing lab here at MIT. 7 00:00:37,837 --> 00:00:39,973 And now before we start, I just want 8 00:00:39,973 --> 00:00:42,575 to mention, so next Monday-- 9 00:00:42,575 --> 00:00:43,843 so we're going to talk today-- 10 00:00:43,843 --> 00:00:46,413 we're going to continue what we started, which 11 00:00:46,413 --> 00:00:49,516 is the chemistry of glass, and we'll 12 00:00:49,516 --> 00:00:55,355 talk about that cooling curve or the effects of different things 13 00:00:55,355 --> 00:00:58,925 on the glass formation and then how to engineer 14 00:00:58,925 --> 00:01:01,194 the properties of the glass. 15 00:01:01,194 --> 00:01:05,098 Before I start, I just want to mention that next Monday we 16 00:01:05,098 --> 00:01:06,900 have something called the Wulff Lecture. 17 00:01:06,900 --> 00:01:10,670 And this is a lecture that is open to the public. 18 00:01:10,670 --> 00:01:12,338 It's geared towards freshmen. 19 00:01:12,338 --> 00:01:14,441 It's put on by the Department of Materials Science 20 00:01:14,441 --> 00:01:18,244 and Engineering every year, and it's usually 21 00:01:18,244 --> 00:01:22,248 some sort of really interesting, exciting topic and usually 22 00:01:22,248 --> 00:01:24,283 a very dynamic lecture. 23 00:01:24,283 --> 00:01:27,120 And in this case it's one of our very own, Sam Shames, who 24 00:01:27,120 --> 00:01:34,060 graduated in 2014, and he'll be talking about his adventures 25 00:01:34,060 --> 00:01:36,963 as a material scientist and how he's 26 00:01:36,963 --> 00:01:42,168 used that knowledge in his life and also in the company 27 00:01:42,168 --> 00:01:44,904 that he founded which is now selling products in over 70 28 00:01:44,904 --> 00:01:48,475 countries around the world. 29 00:01:48,475 --> 00:01:50,443 So I think that will be a lot of fun. 30 00:01:50,443 --> 00:01:56,282 If you can make it, it's next Monday from 4:00 to 5:00 PM. 31 00:01:56,282 --> 00:01:59,652 All right, now the second point I want to make 32 00:01:59,652 --> 00:02:06,726 is that there's a mistake on tomorrow's quiz, 33 00:02:06,726 --> 00:02:07,594 just in the schedule. 34 00:02:07,594 --> 00:02:10,497 So quiz number eight will be given 35 00:02:10,497 --> 00:02:12,499 at the beginning of class. 36 00:02:12,499 --> 00:02:21,674 Quiz eight is at beginning of class, not the end. 37 00:02:21,674 --> 00:02:24,978 I think it might mistakenly say the end. 38 00:02:24,978 --> 00:02:29,115 So you might notice sometimes the quiz-- 39 00:02:29,115 --> 00:02:36,523 so tomorrow the quiz is going to cover defects and then whatever 40 00:02:36,523 --> 00:02:40,126 was covered up until Monday's lecture and Tuesday's 41 00:02:40,126 --> 00:02:42,629 recitation, which includes the beginning of what 42 00:02:42,629 --> 00:02:43,363 we talked about-- 43 00:02:43,363 --> 00:02:43,863 [DINGING] 44 00:02:43,863 --> 00:02:46,499 OK, let's not do that. 45 00:02:46,499 --> 00:02:47,300 Let's turn that off. 46 00:02:50,570 --> 00:02:53,373 And we had an exam on a Monday, and so we didn't want 47 00:02:53,373 --> 00:02:54,574 to give you a quiz that week. 48 00:02:58,111 --> 00:03:01,047 So we're doing defects tomorrow even though we covered defects 49 00:03:01,047 --> 00:03:03,283 last week. 50 00:03:03,283 --> 00:03:07,220 And then we didn't want to give you a quiz right 51 00:03:07,220 --> 00:03:09,822 before or on Thanksgiving. 52 00:03:09,822 --> 00:03:11,224 That didn't seem right. 53 00:03:11,224 --> 00:03:15,295 So for the next quiz what we're doing is 54 00:03:15,295 --> 00:03:17,263 we're still making a quiz for you to have, 55 00:03:17,263 --> 00:03:19,065 and we're going to give it to you next week 56 00:03:19,065 --> 00:03:20,966 but we're not going to count it. 57 00:03:20,966 --> 00:03:22,669 So next week you will still get a quiz 58 00:03:22,669 --> 00:03:28,775 that you have for your studying because I know you'll miss it. 59 00:03:28,775 --> 00:03:31,344 But in case you're not here or you 60 00:03:31,344 --> 00:03:33,813 don't want to do the quiz over your turkey, 61 00:03:33,813 --> 00:03:35,248 we're not going to count that one. 62 00:03:35,248 --> 00:03:38,251 So quiz nine won't be counted. 63 00:03:38,251 --> 00:03:40,954 All right, so that's the quizzes. 64 00:03:40,954 --> 00:03:44,390 Now, where were we? 65 00:03:44,390 --> 00:03:45,525 Here we are. 66 00:03:45,525 --> 00:03:50,730 Speaking of quiz material and thinking about glass 67 00:03:50,730 --> 00:03:56,168 as a potential problem on tomorrow's quiz, yes. 68 00:03:56,168 --> 00:03:58,137 You might want to know about some of the things 69 00:03:58,137 --> 00:03:58,905 we talked about Monday. 70 00:03:58,905 --> 00:03:59,839 Here's an example. 71 00:03:59,839 --> 00:04:01,975 OK, here's a question. 72 00:04:01,975 --> 00:04:03,209 I have two glasses. 73 00:04:03,209 --> 00:04:05,044 They form from liquids, and they're cooled 74 00:04:05,044 --> 00:04:06,879 to some temperature I call T1. 75 00:04:06,879 --> 00:04:08,514 And I tell you that T1 is greater 76 00:04:08,514 --> 00:04:11,317 than Tm, which is the melting point of the material. 77 00:04:11,317 --> 00:04:15,855 Now remember, the melting point is the same. 78 00:04:15,855 --> 00:04:17,123 It's a number. 79 00:04:17,123 --> 00:04:21,327 The melting point of silica, that's a number. 80 00:04:21,327 --> 00:04:26,466 But when the material forms a glass can vary. 81 00:04:26,466 --> 00:04:28,701 Why does a glass form? 82 00:04:28,701 --> 00:04:30,703 Well, a glass forms-- 83 00:04:30,703 --> 00:04:32,272 this is what we covered on Monday-- it 84 00:04:32,272 --> 00:04:35,775 can form because of three different things, right? 85 00:04:35,775 --> 00:04:38,177 One is the crystal complexity. 86 00:04:41,147 --> 00:04:43,616 That's important. 87 00:04:43,616 --> 00:04:49,255 Another is the viscosity. 88 00:04:49,255 --> 00:04:51,691 And the third is the cooling rate. 89 00:04:55,795 --> 00:04:58,731 Those are the three things that we covered 90 00:04:58,731 --> 00:05:04,103 on Monday for reasons why a glass might form, 91 00:05:04,103 --> 00:05:07,473 and then we started kind of talking about the cooling rate. 92 00:05:07,473 --> 00:05:09,275 That's what we need to understand 93 00:05:09,275 --> 00:05:11,077 to answer this question. 94 00:05:11,077 --> 00:05:14,213 So, OK, two glasses forming liquids. 95 00:05:14,213 --> 00:05:15,048 One glass is formed. 96 00:05:15,048 --> 00:05:18,017 Plot the molar volume versus temperature. 97 00:05:18,017 --> 00:05:20,320 All right, so now, let's see. 98 00:05:20,320 --> 00:05:21,354 How about this? 99 00:05:21,354 --> 00:05:26,326 Could this be the volume per mole versus temperature? 100 00:05:26,326 --> 00:05:27,827 So I'm going to try it out here. 101 00:05:27,827 --> 00:05:29,095 I'm going to go like this. 102 00:05:29,095 --> 00:05:34,167 I'm going to go like this, and that looks like the liquid, 103 00:05:34,167 --> 00:05:35,868 maybe. 104 00:05:35,868 --> 00:05:40,740 And then I'm going to go like this and maybe this, 105 00:05:40,740 --> 00:05:44,477 and we'll call that T1. 106 00:05:44,477 --> 00:05:47,714 Does that look right? 107 00:05:47,714 --> 00:05:51,217 No, this can't be right. 108 00:05:51,217 --> 00:05:55,755 This can't be right because, you see, I said that T1, 109 00:05:55,755 --> 00:06:00,760 this is a glass transition. 110 00:06:00,760 --> 00:06:02,028 That's a glass transition. 111 00:06:02,028 --> 00:06:04,230 That's a Tg. 112 00:06:04,230 --> 00:06:06,065 That's another Tg. 113 00:06:06,065 --> 00:06:11,704 But I've said in the question T1 is greater than Tm. 114 00:06:11,704 --> 00:06:13,339 T1 is greater than Tm. 115 00:06:13,339 --> 00:06:18,711 Well, so this can't be true because Tm has to be out here. 116 00:06:18,711 --> 00:06:21,948 Tm is out here where there's a different transition that 117 00:06:21,948 --> 00:06:24,650 occurs, and it turns into a crystal. 118 00:06:24,650 --> 00:06:28,955 So this couldn't be right, T1 greater than Tm. 119 00:06:31,924 --> 00:06:33,092 So what about another one? 120 00:06:33,092 --> 00:06:34,659 Let's try another one. 121 00:06:34,659 --> 00:06:36,195 So how about if I-- 122 00:06:36,195 --> 00:06:38,865 OK, volume per mole. 123 00:06:38,865 --> 00:06:40,666 Now I'm going to go like this. 124 00:06:40,666 --> 00:06:42,568 So I'm going to go like this. 125 00:06:46,372 --> 00:06:51,878 So now here comes one, and here comes the other. 126 00:06:55,248 --> 00:07:01,154 And OK, so I'm going to put now T1 maybe-- 127 00:07:01,154 --> 00:07:08,461 let's try T1 is going to be out here, and Tm would be-- 128 00:07:08,461 --> 00:07:10,129 actually, let me do it differently. 129 00:07:10,129 --> 00:07:10,997 Sorry. 130 00:07:10,997 --> 00:07:14,100 I'm going to go like this. 131 00:07:14,100 --> 00:07:19,705 I'll just connect-- how do I want to do this? 132 00:07:19,705 --> 00:07:21,841 I want it to join these up there. 133 00:07:21,841 --> 00:07:24,377 Yeah, that's another good mistake. 134 00:07:24,377 --> 00:07:26,379 I'm making mistakes on purpose. 135 00:07:28,981 --> 00:07:31,818 And let's make T1 be out here. 136 00:07:31,818 --> 00:07:36,289 So T1 is here, and then Tm could still be there. 137 00:07:36,289 --> 00:07:38,457 This could be Tm. 138 00:07:38,457 --> 00:07:41,494 And then maybe is that right? 139 00:07:41,494 --> 00:07:43,362 Is that a possible curve? 140 00:07:43,362 --> 00:07:46,232 Well, that fixed the T1-Tm problem 141 00:07:46,232 --> 00:07:50,837 because T1 is now greater than Tm like I said in the question, 142 00:07:50,837 --> 00:07:53,773 but what is going on here? 143 00:07:53,773 --> 00:07:55,107 What is going on? 144 00:07:55,107 --> 00:07:59,078 You say, well, but I cooled one faster than the other. 145 00:07:59,078 --> 00:08:00,947 Isn't that kind of what's happening here? 146 00:08:00,947 --> 00:08:04,183 Maybe I started changing the curve? 147 00:08:04,183 --> 00:08:05,051 No. 148 00:08:05,051 --> 00:08:08,821 That's not what this is, so don't make that mistake. 149 00:08:08,821 --> 00:08:17,230 You see, remember, the slope is equal to the thermal expansion 150 00:08:17,230 --> 00:08:20,533 coefficient-- 151 00:08:20,533 --> 00:08:23,836 thermal expansion coefficient. 152 00:08:23,836 --> 00:08:27,206 And those slopes are the same for the different glasses. 153 00:08:27,206 --> 00:08:30,142 Just because I've cooled one differently, 154 00:08:30,142 --> 00:08:31,944 they're not going to have different slopes. 155 00:08:31,944 --> 00:08:34,847 And this is the fundamental challenge. 156 00:08:34,847 --> 00:08:36,582 This is the fundamental confusion point 157 00:08:36,582 --> 00:08:40,620 that happens which is that this is not time. 158 00:08:40,620 --> 00:08:44,123 This axis is not time. 159 00:08:48,528 --> 00:08:50,396 So this is wrong to. 160 00:08:50,396 --> 00:08:53,699 What we're doing is we're talking about something 161 00:08:53,699 --> 00:08:56,469 involving time, cooling rate. 162 00:08:56,469 --> 00:08:58,704 But we're plotting it on something 163 00:08:58,704 --> 00:09:01,374 that doesn't involve time, and that can lead to confusion. 164 00:09:01,374 --> 00:09:02,742 So I wanted to point that out. 165 00:09:02,742 --> 00:09:04,176 You say, well, shouldn't the slope 166 00:09:04,176 --> 00:09:06,946 be different because you're cooling it slower or faster? 167 00:09:06,946 --> 00:09:08,881 No, that's not what this slope is. 168 00:09:08,881 --> 00:09:11,250 This slope is a thermal expansion coefficient. 169 00:09:11,250 --> 00:09:15,421 So the right answer to this must be 170 00:09:15,421 --> 00:09:22,528 that you have your nice liquid phase 171 00:09:22,528 --> 00:09:25,665 and you've made your two glasses. 172 00:09:25,665 --> 00:09:28,301 So here's one. 173 00:09:28,301 --> 00:09:31,671 This has cooled faster. 174 00:09:31,671 --> 00:09:32,305 This is slower. 175 00:09:36,242 --> 00:09:38,177 This would be Tg. 176 00:09:38,177 --> 00:09:43,349 This would be another Tg, maybe Tg1, Tg2. 177 00:09:43,349 --> 00:09:50,022 And the Tm would come down and have-- 178 00:09:50,022 --> 00:09:53,459 well, I've run out of room here, but Tm 179 00:09:53,459 --> 00:09:55,394 might come down like this. 180 00:09:55,394 --> 00:09:58,364 And so T1 must be somewhere up here. 181 00:10:00,933 --> 00:10:03,636 That would be a correct plot for that question. 182 00:10:03,636 --> 00:10:04,570 So does everybody see? 183 00:10:04,570 --> 00:10:07,740 I just want you to get a feeling for this plot. 184 00:10:07,740 --> 00:10:09,642 We introduced it Monday, and I really 185 00:10:09,642 --> 00:10:13,412 want you to feel your oneness with this plot 186 00:10:13,412 --> 00:10:14,847 because it's a very important plot 187 00:10:14,847 --> 00:10:18,451 to understand why glasses form. 188 00:10:18,451 --> 00:10:23,356 All right, now moving on, there's 189 00:10:23,356 --> 00:10:25,825 a lot of properties of glasses, and here I'm 190 00:10:25,825 --> 00:10:27,693 talking about oxide glasses, so silica. 191 00:10:27,693 --> 00:10:32,732 Remember, silicon oxide, oxide, silica, alumina. 192 00:10:32,732 --> 00:10:35,868 These are, oh, oxide. 193 00:10:35,868 --> 00:10:37,169 We talked about that. 194 00:10:37,169 --> 00:10:39,071 Chemically inert, electrically insulating, 195 00:10:39,071 --> 00:10:41,307 mechanically brittle, optically transparent, 196 00:10:41,307 --> 00:10:43,676 visually arresting-- 197 00:10:43,676 --> 00:10:45,678 I like that one-- 198 00:10:45,678 --> 00:10:48,914 these are the properties that we know 199 00:10:48,914 --> 00:10:50,750 about these kinds of glasses. 200 00:10:50,750 --> 00:10:51,617 We already know them. 201 00:10:51,617 --> 00:10:53,085 But what I want to talk about today 202 00:10:53,085 --> 00:10:56,455 is how they can be engineered. 203 00:10:56,455 --> 00:11:02,128 And this plot is a basis for understanding that. 204 00:11:02,128 --> 00:11:06,699 And so is spaghetti, and that's what we're going to talk about. 205 00:11:06,699 --> 00:11:09,068 So the very first one-- which we'll set up 206 00:11:09,068 --> 00:11:11,237 our demo in just a few minutes. 207 00:11:11,237 --> 00:11:13,806 The very first one that I want to talk about 208 00:11:13,806 --> 00:11:15,141 is the mechanical properties. 209 00:11:15,141 --> 00:11:17,777 We know glass to be very brittle, 210 00:11:17,777 --> 00:11:20,079 but could we change its mechanical properties? 211 00:11:20,079 --> 00:11:23,516 Could we do something about the mechanical properties? 212 00:11:23,516 --> 00:11:26,352 And by the way, if those are the things that 213 00:11:26,352 --> 00:11:28,154 dictate whether a glass forms or not, 214 00:11:28,154 --> 00:11:29,922 then those are the things that you 215 00:11:29,922 --> 00:11:33,025 might think we might try to engineer if we want to change 216 00:11:33,025 --> 00:11:34,360 the properties of glass. 217 00:11:38,431 --> 00:11:42,401 You can imagine I'm a silica-- oh, you got to pass this out. 218 00:11:42,401 --> 00:11:46,906 I'm a big silicate, an SiO4, and I'm 219 00:11:46,906 --> 00:11:49,040 connected to these other silicate groups 220 00:11:49,040 --> 00:11:56,649 through this shared bridged oxygen. And I'm a bulky thing, 221 00:11:56,649 --> 00:12:01,420 and I'm trying to move around in the liquid, crystal complexity. 222 00:12:01,420 --> 00:12:04,190 I'm cooling down, and I'm trying to move around. 223 00:12:04,190 --> 00:12:06,492 And [INAUDIBLE] told me to go that way, 224 00:12:06,492 --> 00:12:08,928 but it's actually over there, or there's no building there 225 00:12:08,928 --> 00:12:10,129 and I don't know where to go. 226 00:12:10,129 --> 00:12:11,797 Where is the lattice site? 227 00:12:11,797 --> 00:12:13,232 It's complicated. 228 00:12:13,232 --> 00:12:14,900 Glass could form. 229 00:12:14,900 --> 00:12:16,102 Glass could form. 230 00:12:16,102 --> 00:12:18,104 Or maybe I'm a silicate group and I'm like, hey, 231 00:12:18,104 --> 00:12:19,538 could you please get out of my way? 232 00:12:19,538 --> 00:12:21,207 You're really slowing things down, 233 00:12:21,207 --> 00:12:24,443 you other silicate group that I'm attached to. 234 00:12:24,443 --> 00:12:26,412 Viscous, get out of my way. 235 00:12:26,412 --> 00:12:29,014 No, I can't, viscous. 236 00:12:29,014 --> 00:12:31,450 Or maybe you're a silicate group and you're cooling down 237 00:12:31,450 --> 00:12:35,755 and you're like, that was very sudden. 238 00:12:35,755 --> 00:12:37,823 I didn't even realize that happened. 239 00:12:37,823 --> 00:12:41,627 All of a sudden I'm supposed to be a solid? 240 00:12:41,627 --> 00:12:42,928 This is what's happening. 241 00:12:42,928 --> 00:12:47,665 And so instead of getting into this beautiful quartz crystal 242 00:12:47,665 --> 00:12:49,568 it doesn't get there. 243 00:12:49,568 --> 00:12:51,003 It doesn't get there. 244 00:12:51,003 --> 00:12:55,875 A supercooled liquid wants to be a solid. 245 00:12:55,875 --> 00:13:01,847 It wants to, but it can't for some reason, for some reason 246 00:13:01,847 --> 00:13:06,252 that has to do with those. 247 00:13:06,252 --> 00:13:08,187 So let's just have this in our hands 248 00:13:08,187 --> 00:13:10,956 while we're listening and thinking about things, 249 00:13:10,956 --> 00:13:15,628 and let me just tell you about this one way-- 250 00:13:15,628 --> 00:13:17,563 if I take a piece of glass-- 251 00:13:17,563 --> 00:13:21,767 if I take a piece of glass, and now imagine 252 00:13:21,767 --> 00:13:24,703 that I take some part of it, like this part here. 253 00:13:27,473 --> 00:13:33,846 And in this part I'm going to cool faster, 254 00:13:33,846 --> 00:13:40,186 and in this part here I'm going to cool slower. 255 00:13:40,186 --> 00:13:47,226 So imagine it's a slab of glass, and it's like the edges are 256 00:13:47,226 --> 00:13:49,528 cooled at a different rate. 257 00:13:49,528 --> 00:13:51,664 That's actually exactly why a car window, 258 00:13:51,664 --> 00:13:54,099 if you look at it through polarized glasses, 259 00:13:54,099 --> 00:13:56,168 has spots on it. 260 00:13:56,168 --> 00:13:59,138 Those spots, some of you may have seen these. 261 00:13:59,138 --> 00:14:03,475 Those spots are changes, purposeful changes 262 00:14:03,475 --> 00:14:06,979 in the mechanical properties of the glass to keep you safe. 263 00:14:06,979 --> 00:14:09,815 Why? 264 00:14:09,815 --> 00:14:14,987 If you call it slower, then you might have some volume 265 00:14:14,987 --> 00:14:16,822 that you want. 266 00:14:16,822 --> 00:14:23,295 The volume here, let's call this Vb and let's call this Va. 267 00:14:23,295 --> 00:14:27,967 That goes along with the graph we used before, b and a. 268 00:14:27,967 --> 00:14:32,838 So it wants V-- 269 00:14:32,838 --> 00:14:34,373 what did I do-- b. 270 00:14:34,373 --> 00:14:36,040 This wants Va. 271 00:14:36,040 --> 00:14:37,076 But look at what happens. 272 00:14:39,645 --> 00:14:42,982 If I purposely cool the top really fast or maybe 273 00:14:42,982 --> 00:14:47,887 I make spots that I cool fast, then what happens? 274 00:14:47,887 --> 00:14:52,224 Well, this wants to have volume a inside. 275 00:14:52,224 --> 00:14:56,729 This wants to have volume-- well, this cools first. 276 00:14:56,729 --> 00:14:58,230 So this cools first. 277 00:14:58,230 --> 00:15:01,433 So inside, so what happens? 278 00:15:01,433 --> 00:15:07,406 As I cool it now, I have this. 279 00:15:07,406 --> 00:15:11,043 This is now a glass. 280 00:15:11,043 --> 00:15:13,178 This is now a solid. 281 00:15:13,178 --> 00:15:18,417 And I should say glass solid, so it's solidified. 282 00:15:18,417 --> 00:15:24,223 And this wants to have a lower volume-- 283 00:15:24,223 --> 00:15:27,226 lower volume. 284 00:15:27,226 --> 00:15:29,428 It wants a lower volume, but that's 285 00:15:29,428 --> 00:15:33,599 been frozen at a higher volume. 286 00:15:33,599 --> 00:15:34,199 Why? 287 00:15:34,199 --> 00:15:35,634 I cooled it faster. 288 00:15:35,634 --> 00:15:36,602 That's it. 289 00:15:36,602 --> 00:15:40,072 I cooled it faster, and now the inside is like, wait a second, 290 00:15:40,072 --> 00:15:41,807 I'm not cooling so fast. 291 00:15:41,807 --> 00:15:43,642 I don't need such a high volume. 292 00:15:43,642 --> 00:15:45,911 Can I please get a smaller volume out of this? 293 00:15:45,911 --> 00:15:49,081 And the top is like, well, I'm already stuck. 294 00:15:49,081 --> 00:15:50,449 I'm already a solid. 295 00:15:50,449 --> 00:15:52,351 And what happens is it pulls. 296 00:15:56,322 --> 00:16:06,131 And so what you get is wants lower volume pulls 297 00:16:06,131 --> 00:16:11,870 on the surface, and that means that this is going 298 00:16:11,870 --> 00:16:16,175 to be the top, if I'll just draw it one more time, 299 00:16:16,175 --> 00:16:18,310 will be under compression-- 300 00:16:21,046 --> 00:16:25,017 under compression, and the inside 301 00:16:25,017 --> 00:16:26,852 will be under tensile stress-- 302 00:16:30,289 --> 00:16:31,523 under tensile stress. 303 00:16:31,523 --> 00:16:33,025 You can kind of imagine this, right? 304 00:16:33,025 --> 00:16:34,226 You can see it. 305 00:16:34,226 --> 00:16:36,729 I've frozen the top because of cooling rate. 306 00:16:36,729 --> 00:16:38,263 It's right here. 307 00:16:38,263 --> 00:16:39,999 I just cooled the top faster. 308 00:16:39,999 --> 00:16:41,633 The inside isn't cold yet. 309 00:16:41,633 --> 00:16:44,536 It starts to cool, and it tries to solidify 310 00:16:44,536 --> 00:16:45,571 at a different volume. 311 00:16:45,571 --> 00:16:46,905 It pulls it in. 312 00:16:46,905 --> 00:16:51,043 But see, that changes the mechanical properties 313 00:16:51,043 --> 00:16:52,578 of the surface. 314 00:16:52,578 --> 00:16:54,179 That's called tempering. 315 00:16:54,179 --> 00:16:56,148 That's called tempered glass. 316 00:16:56,148 --> 00:17:00,152 This is tempered glass, and there is no better example 317 00:17:00,152 --> 00:17:05,723 of temporal glass than the Prince Rupert's drop, which is 318 00:17:05,723 --> 00:17:08,493 the demo that Peter has come. 319 00:17:08,493 --> 00:17:09,194 Here's Peter. 320 00:17:09,194 --> 00:17:11,696 There's Peter blowing some glass. 321 00:17:11,696 --> 00:17:14,665 This is what he does in his free time. 322 00:17:14,665 --> 00:17:17,236 He just throws these big glass-bowling parties. 323 00:17:17,236 --> 00:17:19,471 He also happens to be the director of the glass lab, 324 00:17:19,471 --> 00:17:21,205 like I said. 325 00:17:21,205 --> 00:17:24,877 He also teaches the classes, the glass-blowing classes. 326 00:17:24,877 --> 00:17:27,546 There's one for freshmen during IAP, 327 00:17:27,546 --> 00:17:29,948 and there's another one in the spring. 328 00:17:29,948 --> 00:17:30,983 They're very popular. 329 00:17:30,983 --> 00:17:35,654 But because you're in 3091, he'll get you in. 330 00:17:35,654 --> 00:17:39,491 He doesn't like it when I say that because it's not true. 331 00:17:39,491 --> 00:17:41,960 [LAUGHTER] 332 00:17:41,960 --> 00:17:44,463 But come talk to him. 333 00:17:44,463 --> 00:17:48,067 He's right here, and I think you've got a demo for us. 334 00:17:48,067 --> 00:17:50,436 So I'm going to let Peter take the stage 335 00:17:50,436 --> 00:17:55,174 and show you the best example of tempered glass you can do. 336 00:17:55,174 --> 00:17:58,444 And if you want to use the mic-- 337 00:17:58,444 --> 00:17:59,278 if you want to talk. 338 00:17:59,278 --> 00:18:06,585 --a little kit out 339 00:18:06,585 --> 00:18:08,654 And one year Professor Cima, when 340 00:18:08,654 --> 00:18:12,691 he was teaching this class, told the class 341 00:18:12,691 --> 00:18:15,094 that they had to come to the lottery for the glassblowing 342 00:18:15,094 --> 00:18:18,864 class, and it's a big class. 343 00:18:18,864 --> 00:18:21,767 And so dutifully everyone came to the lottery, 344 00:18:21,767 --> 00:18:25,971 and we already have about 150 students plus 3091. 345 00:18:25,971 --> 00:18:28,674 And the lottery was in room 6120, 346 00:18:28,674 --> 00:18:32,511 so we overflowed it by a lot. 347 00:18:32,511 --> 00:18:36,014 So I told Michael, don't ever do that again, please. 348 00:18:36,014 --> 00:18:38,817 Which is why I do it every year. 349 00:18:38,817 --> 00:18:40,452 But we like 3091 students. 350 00:18:40,452 --> 00:18:42,688 We'll try to give them preference. 351 00:18:42,688 --> 00:18:44,056 [LAUGHTER] 352 00:18:44,056 --> 00:18:46,024 Trying to work it for you. 353 00:18:46,024 --> 00:18:46,992 He says that. 354 00:18:59,204 --> 00:19:02,908 How many of you have seen Prince Rupert drops before? 355 00:19:02,908 --> 00:19:03,709 Some people, yeah. 356 00:19:03,709 --> 00:19:08,247 There's a lot of online stuff about them, 357 00:19:08,247 --> 00:19:09,815 but you get to see a live one today. 358 00:19:14,219 --> 00:19:17,122 So what's the difference between a Prince Rupert drop 359 00:19:17,122 --> 00:19:21,660 and tempered glass like the type [INAUDIBLE]?? 360 00:19:21,660 --> 00:19:25,230 Anybody want to take a guess at that? 361 00:19:28,333 --> 00:19:30,035 They're both under stress, but the stress 362 00:19:30,035 --> 00:19:32,337 is generated in a different way. 363 00:19:32,337 --> 00:19:34,907 So the dots that were on that windshield 364 00:19:34,907 --> 00:19:36,375 are formed by air coolant. 365 00:19:36,375 --> 00:19:37,943 That's how tempered glass is made. 366 00:19:37,943 --> 00:19:40,879 It goes through what's called a [? lear ?] or a rolling 367 00:19:40,879 --> 00:19:43,649 conveyor, and it's heated up very, very quickly, 368 00:19:43,649 --> 00:19:45,417 and then it's cooled very quickly. 369 00:19:45,417 --> 00:19:49,054 And it's cooled by this array of compressed air jets 370 00:19:49,054 --> 00:19:52,491 on both sides that take it from almost the transition 371 00:19:52,491 --> 00:19:53,792 temperature-- 372 00:19:53,792 --> 00:19:55,994 it just about wants to move but doesn't 373 00:19:55,994 --> 00:20:00,999 quite, down to room temperature in three minutes or so. 374 00:20:00,999 --> 00:20:05,604 And that super-rapid cooling is what generates that stress 375 00:20:05,604 --> 00:20:06,371 on the-- 376 00:20:06,371 --> 00:20:08,006 the difference between the inside 377 00:20:08,006 --> 00:20:10,409 and the outside temperature in the glass. 378 00:20:10,409 --> 00:20:12,444 And so it's air cooled, but Prince Rupert 379 00:20:12,444 --> 00:20:16,582 drop is cooled by-- anyone want to guess? 380 00:20:16,582 --> 00:20:17,416 Water. 381 00:20:17,416 --> 00:20:19,051 Yeah, by water. 382 00:20:19,051 --> 00:20:22,020 So water is a better coolant, right? 383 00:20:22,020 --> 00:20:25,691 So as a result, you get a lot more stress 384 00:20:25,691 --> 00:20:28,560 embodied with the glass, a lot more stress. 385 00:20:28,560 --> 00:20:30,996 And so that's relevant because you 386 00:20:30,996 --> 00:20:34,233 don't want to make a window that breaks with that kind of energy 387 00:20:34,233 --> 00:20:37,636 and so you get explosive energy all over the place. 388 00:20:37,636 --> 00:20:40,372 So tempered glass is engineered to fail. 389 00:20:40,372 --> 00:20:43,442 It's very strong, but it's engineered 390 00:20:43,442 --> 00:20:46,278 to fail so that when it breaks, it breaks into small pieces 391 00:20:46,278 --> 00:20:50,382 so that if you're walking along the sidewalk and a skyscraper 392 00:20:50,382 --> 00:20:53,752 blows out a window, you don't get huge shards of glass 393 00:20:53,752 --> 00:20:56,121 falling down and hurting people. 394 00:20:56,121 --> 00:20:58,423 You get little pellets gently raining down, 395 00:20:58,423 --> 00:21:00,359 which isn't such a bad thing. 396 00:21:00,359 --> 00:21:01,793 [LAUGHTER] 397 00:21:01,793 --> 00:21:04,763 So I've got two kinds of Prince Rupert drops that I made here 398 00:21:04,763 --> 00:21:08,800 and a vessel in which to demonstrate here. 399 00:21:13,372 --> 00:21:15,374 So first I'm going to show you-- 400 00:21:15,374 --> 00:21:19,711 they both cool rather quickly, but one was cooled in air. 401 00:21:19,711 --> 00:21:22,881 One was cooled in water. 402 00:21:22,881 --> 00:21:27,119 This is the one that's cooled in air. 403 00:21:27,119 --> 00:21:29,688 And by the way, I used to give a demo in the Glass Lab 404 00:21:29,688 --> 00:21:32,824 where I would take the Prince Rupert drop, 405 00:21:32,824 --> 00:21:35,227 put it on a sealed table that we call the marver, 406 00:21:35,227 --> 00:21:37,329 and hit it with a hammer as hard as I could. 407 00:21:37,329 --> 00:21:40,432 I was never able to shatter this head with a hammer. 408 00:21:40,432 --> 00:21:42,734 In fact, I dented the marver so many times 409 00:21:42,734 --> 00:21:45,170 that I stopped doing that demo. 410 00:21:45,170 --> 00:21:48,907 So I have a different way of doing it now which is-- 411 00:21:48,907 --> 00:21:50,509 I won't do that today, but usually I'll 412 00:21:50,509 --> 00:21:52,778 have a student come and try to break the Prince Rupert 413 00:21:52,778 --> 00:21:53,879 drop in their hands. 414 00:21:53,879 --> 00:21:55,080 It's really hard to do. 415 00:21:55,080 --> 00:21:56,581 Most people can't do it. 416 00:21:56,581 --> 00:21:59,351 But the air-cooled Prince Rupert drop 417 00:21:59,351 --> 00:22:01,019 doesn't have the same kind of strength. 418 00:22:01,019 --> 00:22:02,487 So watch what happens. 419 00:22:06,958 --> 00:22:10,429 Not much. 420 00:22:10,429 --> 00:22:11,797 Well, let's try down farther. 421 00:22:11,797 --> 00:22:13,131 Maybe there's more stress there. 422 00:22:15,801 --> 00:22:17,502 Nope, not [INAUDIBLE]. 423 00:22:20,605 --> 00:22:23,241 Let me try one more time. 424 00:22:23,241 --> 00:22:25,610 Maybe where it's thicker maybe there will be more stress. 425 00:22:29,548 --> 00:22:33,018 Maybe a little. 426 00:22:33,018 --> 00:22:34,853 So, here's the one that's water cooled. 427 00:22:44,896 --> 00:22:47,332 OK, don't blink. 428 00:22:47,332 --> 00:22:52,170 Five, four, three, two, one. 429 00:22:58,143 --> 00:23:01,480 That's the speed of sound in glass, 430 00:23:01,480 --> 00:23:04,015 which is, I think, about three times faster than the speed 431 00:23:04,015 --> 00:23:05,884 of sound in air. 432 00:23:05,884 --> 00:23:07,486 So you can't see it. 433 00:23:07,486 --> 00:23:09,921 But there is some great high-speed video-- 434 00:23:09,921 --> 00:23:12,157 maybe some of you have seen that online-- 435 00:23:12,157 --> 00:23:14,693 of Prince Rupert drops exploding. 436 00:23:14,693 --> 00:23:16,661 And actually up in the Edgerton Center 437 00:23:16,661 --> 00:23:19,364 they have a camera that can catch that, 438 00:23:19,364 --> 00:23:21,867 and they've got some really cool video. 439 00:23:21,867 --> 00:23:22,868 I'm going to leave this. 440 00:23:22,868 --> 00:23:24,469 This is a very cool fragment that 441 00:23:24,469 --> 00:23:27,739 shows the fracture, the failure pattern, which 442 00:23:27,739 --> 00:23:28,673 is really interesting. 443 00:23:28,673 --> 00:23:31,276 It fails from the center of the drop 444 00:23:31,276 --> 00:23:33,812 radially out at an angle that looks 445 00:23:33,812 --> 00:23:36,314 to be about a 45-degree angle. 446 00:23:36,314 --> 00:23:37,582 You can probably explain that. 447 00:23:37,582 --> 00:23:38,950 That will be on the quiz tomorrow. 448 00:23:38,950 --> 00:23:41,686 [LAUGHTER] 449 00:23:42,187 --> 00:23:44,055 45 degree [INAUDIBLE]? 450 00:23:44,055 --> 00:23:45,824 Was there a question? 451 00:23:45,824 --> 00:23:48,760 I'm going to do one more just in case anybody blinked, 452 00:23:48,760 --> 00:23:52,330 and then I'm going to be on my way. 453 00:23:52,330 --> 00:23:53,965 By the way, Jeff mentioned that we 454 00:23:53,965 --> 00:23:58,503 had an IAP pass that starts during IAP for freshmen 455 00:23:58,503 --> 00:24:02,007 and a spring class that's open to everybody at the institute. 456 00:24:02,007 --> 00:24:05,010 So if you're not a freshman, you can come to the lottery. 457 00:24:05,010 --> 00:24:07,412 The lottery is for all of our classes, 458 00:24:07,412 --> 00:24:09,581 are shown on the Glass Lab website. 459 00:24:09,581 --> 00:24:11,049 And I think we're going to be doing 460 00:24:11,049 --> 00:24:14,386 the lottery for the spring for the IAP class in November 461 00:24:14,386 --> 00:24:19,157 late this month, and then the spring class will probably 462 00:24:19,157 --> 00:24:22,527 be sometime in January, and it starts in March. 463 00:24:22,527 --> 00:24:23,528 OK, ready? 464 00:24:23,528 --> 00:24:28,567 Five, four, three, two, one. 465 00:24:28,567 --> 00:24:32,037 [INAUDIBLE] will even have some more energy. 466 00:24:35,941 --> 00:24:36,675 Thanks, Peter. 467 00:24:36,675 --> 00:24:40,679 [APPLAUSE] 468 00:24:47,519 --> 00:24:49,488 That was awesome, and I actually do 469 00:24:49,488 --> 00:24:52,991 have a high-speed video of it, so I'll show that to you now. 470 00:24:52,991 --> 00:24:56,962 And again, so if you have questions about glass, 471 00:24:56,962 --> 00:24:57,863 if you want to watch-- 472 00:24:57,863 --> 00:25:02,601 Peter can make animals for you, I think, on request. 473 00:25:02,601 --> 00:25:05,871 Oh, this guy. 474 00:25:05,871 --> 00:25:08,006 But anyway, thanks a lot, Peter, for coming by. 475 00:25:10,775 --> 00:25:16,081 As you know, I'm a big believer in hands on, seeing things. 476 00:25:16,081 --> 00:25:17,849 Can we pass-- is this-- 477 00:25:17,849 --> 00:25:18,617 no. 478 00:25:18,617 --> 00:25:20,051 Well, your call. 479 00:25:20,051 --> 00:25:23,655 Just don't eat it. 480 00:25:23,655 --> 00:25:28,293 So now you know on parent's day, when we have parents here, 481 00:25:28,293 --> 00:25:29,594 we had the two sheets of glass. 482 00:25:29,594 --> 00:25:30,795 One is called annealed. 483 00:25:30,795 --> 00:25:34,199 It just means it's not tempered, and the baseball 484 00:25:34,199 --> 00:25:36,668 was supposed to break it. 485 00:25:36,668 --> 00:25:38,837 It didn't. 486 00:25:38,837 --> 00:25:40,539 Peter's got very good annealed glass. 487 00:25:40,539 --> 00:25:43,008 He's the one that gave us those big sheets. 488 00:25:43,008 --> 00:25:46,444 And it breaks into these huge, dangerous shards. 489 00:25:46,444 --> 00:25:47,045 Thanks, Peter. 490 00:25:47,045 --> 00:25:49,080 Take care. 491 00:25:49,080 --> 00:25:50,515 Oh yeah, thank you. 492 00:25:50,515 --> 00:25:53,885 [APPLAUSE] 493 00:25:57,289 --> 00:26:01,593 If you notice, the tempered glass, we tried to break it. 494 00:26:01,593 --> 00:26:03,495 It also doesn't break. 495 00:26:03,495 --> 00:26:06,097 It was supposed to be the only one that didn't break. 496 00:26:06,097 --> 00:26:08,266 But then you take a little hammer at the edge 497 00:26:08,266 --> 00:26:11,102 and you just lightly tap the edge and the whole thing 498 00:26:11,102 --> 00:26:11,603 breaks. 499 00:26:11,603 --> 00:26:12,203 Why? 500 00:26:12,203 --> 00:26:15,907 Because it's got so much built-in stress. 501 00:26:15,907 --> 00:26:18,310 It's got all this compressive stress, 502 00:26:18,310 --> 00:26:21,680 and the edge isn't protecting that. 503 00:26:21,680 --> 00:26:24,749 The edge of that tempered glass isn't protecting the stress. 504 00:26:24,749 --> 00:26:26,785 So when I just dig in a little bit, 505 00:26:26,785 --> 00:26:30,722 it's able to all crack and release that stress. 506 00:26:30,722 --> 00:26:32,591 So that's what happened on family day. 507 00:26:32,591 --> 00:26:33,825 Here's a high-speed video. 508 00:26:33,825 --> 00:26:35,660 These are two guys from Corning. 509 00:26:35,660 --> 00:26:37,762 And we can listen to this. 510 00:26:37,762 --> 00:26:38,430 [VIDEO PLAYBACK] 511 00:26:38,430 --> 00:26:39,731 They're actually pretty cool. 512 00:26:39,731 --> 00:26:42,801 - So there's a few things going on here. 513 00:26:42,801 --> 00:26:46,671 The cold water rapidly cools the exterior surface of the glass, 514 00:26:46,671 --> 00:26:48,873 hardening it almost immediately. 515 00:26:48,873 --> 00:26:52,344 The interior, still molten, cools more slowly. 516 00:26:52,344 --> 00:26:55,513 As it cools, it contracts and attempts to pull the surface 517 00:26:55,513 --> 00:26:57,449 in with it, but it can't-- 518 00:26:57,449 --> 00:26:58,950 well, not very much. 519 00:26:58,950 --> 00:27:00,619 The surface has already hardened, 520 00:27:00,619 --> 00:27:03,622 so it gets pulled in only a little, compressing it, 521 00:27:03,622 --> 00:27:07,158 while also creating an internal layer that remains forever 522 00:27:07,158 --> 00:27:09,227 under tension. 523 00:27:09,227 --> 00:27:10,929 It is this action that gives the glass 524 00:27:10,929 --> 00:27:12,897 its uncharacteristic strength. 525 00:27:12,897 --> 00:27:16,334 We call it compressive strength. 526 00:27:16,334 --> 00:27:17,802 - It sounds like the same principle 527 00:27:17,802 --> 00:27:20,972 as how an arch provides strength in structural engineering. 528 00:27:20,972 --> 00:27:22,040 - Yes, kind of. 529 00:27:22,040 --> 00:27:23,842 Now, Jamie, I'm going to ask for your help. 530 00:27:23,842 --> 00:27:26,277 We're going to attempt to destroy this Prince Rupert 531 00:27:26,277 --> 00:27:26,978 drop. 532 00:27:26,978 --> 00:27:30,081 I just want you to tip that hammer past its center point. 533 00:27:30,081 --> 00:27:30,615 Go ahead. 534 00:27:34,219 --> 00:27:35,720 That's what Peter was talking about. 535 00:27:35,720 --> 00:27:37,322 So you can hit it really hard. 536 00:27:37,322 --> 00:27:39,324 - Now I feel like we've been swindled. 537 00:27:39,324 --> 00:27:40,458 - Swindled not. 538 00:27:40,458 --> 00:27:41,526 We have just experienced-- 539 00:27:41,526 --> 00:27:42,627 That's good writing. 540 00:27:42,627 --> 00:27:43,461 That's good writing. 541 00:27:43,461 --> 00:27:45,030 - --the power of compressive strength. 542 00:27:45,030 --> 00:27:46,831 It does, however, have an Achilles heel. 543 00:27:46,831 --> 00:27:51,803 Take those nippers right there and nip the backside 544 00:27:51,803 --> 00:27:53,805 of the tail of this Prince Rupert drop 545 00:27:53,805 --> 00:27:54,773 and watch what happens. 546 00:27:54,773 --> 00:27:56,474 Wait, wait, wait, cue the high-speed camera. 547 00:27:56,474 --> 00:27:57,175 OK, here we go. 548 00:28:01,579 --> 00:28:02,080 - Oh! 549 00:28:05,216 --> 00:28:05,784 Here it comes. 550 00:28:11,022 --> 00:28:13,558 - That was even cooler than I thought it would be. 551 00:28:13,558 --> 00:28:14,526 [END PLAYBACK] 552 00:28:14,526 --> 00:28:16,795 So that's what you just saw live. 553 00:28:16,795 --> 00:28:20,198 And what that is is it's a relief of-- 554 00:28:20,198 --> 00:28:21,499 thank you, or not. 555 00:28:21,499 --> 00:28:22,467 [APPLAUSE] 556 00:28:22,467 --> 00:28:23,068 Yeah, sure. 557 00:28:26,571 --> 00:28:28,640 As Peter said, tempered glass like in your car, 558 00:28:28,640 --> 00:28:30,642 it's done with air cooling. 559 00:28:30,642 --> 00:28:33,244 That's literally what those circles are. 560 00:28:33,244 --> 00:28:34,846 If you cool it even faster-- 561 00:28:37,482 --> 00:28:39,250 bam, faster cooling. 562 00:28:39,250 --> 00:28:42,253 You now know, what does faster cooling mean? 563 00:28:42,253 --> 00:28:44,355 Well, if it's going to form a glass 564 00:28:44,355 --> 00:28:47,459 you might be all the way near the melting point, 565 00:28:47,459 --> 00:28:50,929 and you're going to have an even-higher volume per mole 566 00:28:50,929 --> 00:28:53,398 which is going to cause even more stress within the glass 567 00:28:53,398 --> 00:28:55,767 which is going to make the surface very 568 00:28:55,767 --> 00:28:59,003 strong because it's all compressed, 569 00:28:59,003 --> 00:29:01,206 but it's also going to have a lot of energy in it 570 00:29:01,206 --> 00:29:02,273 that it wants to release. 571 00:29:05,810 --> 00:29:06,511 Let's see. 572 00:29:06,511 --> 00:29:08,880 We were here on Monday, and because I 573 00:29:08,880 --> 00:29:11,616 was talking about other ways to change the properties-- 574 00:29:11,616 --> 00:29:14,185 in fact, remember, I showed you a couple of different examples 575 00:29:14,185 --> 00:29:17,722 of glass, right, a glass cup and a glass bottle, 576 00:29:17,722 --> 00:29:21,693 and it turns out there is not just silica in it. 577 00:29:21,693 --> 00:29:23,328 There's all these other things in it, 578 00:29:23,328 --> 00:29:25,730 and there's many, many kinds of glass. 579 00:29:25,730 --> 00:29:26,998 And I listed a few here. 580 00:29:26,998 --> 00:29:28,900 This was from Monday, so I'm showing it again. 581 00:29:28,900 --> 00:29:31,236 And going all the way back to glass made in ancient Rome 582 00:29:31,236 --> 00:29:35,373 you'll find that it's got these other ingredients. 583 00:29:35,373 --> 00:29:36,174 Why? 584 00:29:36,174 --> 00:29:39,444 So that's what I want to talk about next. 585 00:29:39,444 --> 00:29:40,979 Well, let's use this. 586 00:29:40,979 --> 00:29:45,850 So if you notice-- 587 00:29:45,850 --> 00:29:47,452 and this is where we left off Monday-- 588 00:29:47,452 --> 00:29:50,822 if you notice something like calcium oxide, well, 589 00:29:50,822 --> 00:29:55,794 it's going to go to Ca2+ and O2-. 590 00:29:55,794 --> 00:29:58,096 Let's look at Na2O. 591 00:29:58,096 --> 00:30:04,469 Na2O is going to go 2Na+ plus O2-. 592 00:30:04,469 --> 00:30:05,470 How about alumina? 593 00:30:05,470 --> 00:30:08,873 That's on there, Al2O3. 594 00:30:08,873 --> 00:30:18,049 Well, that's going to go to 2Al3+ plus 3O2-. 595 00:30:18,049 --> 00:30:20,952 Notice a pattern. 596 00:30:20,952 --> 00:30:22,754 The pattern is you get O2-. 597 00:30:28,026 --> 00:30:30,995 We can understand why O2- minus has 598 00:30:30,995 --> 00:30:34,432 been used, why chemistry has been 599 00:30:34,432 --> 00:30:40,138 used to change the properties of glass for millennia. 600 00:30:40,138 --> 00:30:43,474 And the reason goes back to the pictures 601 00:30:43,474 --> 00:30:45,844 that we drew on Monday where we started 602 00:30:45,844 --> 00:30:49,681 by talking about the chemistry of the silicate group. 603 00:30:49,681 --> 00:30:52,150 So remember Si? 604 00:30:52,150 --> 00:30:53,952 Remember this? 605 00:30:53,952 --> 00:31:00,058 An SiO4 is happy if it's got four minus charges. 606 00:31:00,058 --> 00:31:02,527 Remember that? 607 00:31:02,527 --> 00:31:05,296 We started with Lewis and it satisfies the octet. 608 00:31:05,296 --> 00:31:08,700 But then in glass what happens is you bridge. 609 00:31:08,700 --> 00:31:10,869 And so you have this. 610 00:31:10,869 --> 00:31:13,271 And I won't draw all of them. 611 00:31:13,271 --> 00:31:15,707 I'll just draw it the way we drew it before. 612 00:31:18,509 --> 00:31:21,713 And you have these bridges, and all of these oxygens 613 00:31:21,713 --> 00:31:27,318 are bridges in glass. 614 00:31:27,318 --> 00:31:29,721 So now I'll say, well, what if I wanted-- 615 00:31:29,721 --> 00:31:36,027 and remember, these are forming these long, viscous chains. 616 00:31:36,027 --> 00:31:40,265 What if I wanted to make them flow a little more easily? 617 00:31:40,265 --> 00:31:43,167 What if I wanted them to form shorter chains? 618 00:31:43,167 --> 00:31:47,472 What if I wanted to cut the pasta? 619 00:31:47,472 --> 00:31:49,240 Don't do it in Italy. 620 00:31:49,240 --> 00:31:51,509 They'll get really upset. 621 00:31:51,509 --> 00:31:53,411 But Americans are OK with it. 622 00:31:53,411 --> 00:31:56,547 If you need to cut the pasta, it's OK in this country. 623 00:31:56,547 --> 00:32:00,318 But if I need to cut the pasta in chemistry and it's glass 624 00:32:00,318 --> 00:32:04,589 that I'm cutting, O2- is my knife. 625 00:32:04,589 --> 00:32:07,625 It's my chemical scissors. 626 00:32:07,625 --> 00:32:11,930 Chemical scissors, I like that-- chemical scissors. 627 00:32:15,099 --> 00:32:15,566 Why? 628 00:32:15,566 --> 00:32:18,036 Well, you can see because I go back. 629 00:32:18,036 --> 00:32:19,437 What did the oxygen do? 630 00:32:19,437 --> 00:32:23,675 By bridging it didn't need that extra electron. 631 00:32:23,675 --> 00:32:27,879 But if I bring now something like Na2O-- 632 00:32:27,879 --> 00:32:29,380 so I've got an O2-. 633 00:32:29,380 --> 00:32:32,350 Now I'm going to add an O2-. 634 00:32:35,086 --> 00:32:38,957 Then what will happen is you're going to cut this. 635 00:32:38,957 --> 00:32:42,293 So now I'll just draw the-- 636 00:32:42,293 --> 00:32:43,695 I'll see if I can-- 637 00:32:43,695 --> 00:32:48,399 OK, so now I've added not just an oxygen atom but the two 638 00:32:48,399 --> 00:32:53,037 charges that each of them needed before they bridged, you see, 639 00:32:53,037 --> 00:32:54,973 to be happy? 640 00:32:54,973 --> 00:32:57,675 And so now this can have one of those charges, 641 00:32:57,675 --> 00:33:03,181 and over here you can have another one, 642 00:33:03,181 --> 00:33:07,018 and so on and so on. 643 00:33:07,018 --> 00:33:09,887 But see, now I've cut. 644 00:33:09,887 --> 00:33:14,292 I've cut the glass pasta, and I've done it chemically 645 00:33:14,292 --> 00:33:16,027 and I've done it from understanding 646 00:33:16,027 --> 00:33:18,296 of octet and Lewis, from basic chemistry 647 00:33:18,296 --> 00:33:20,164 principles that we've learned. 648 00:33:20,164 --> 00:33:21,065 Where's the sodium go? 649 00:33:21,065 --> 00:33:22,967 Well, they'll be like a sodium. 650 00:33:22,967 --> 00:33:25,970 They'll want to hang out close by these. 651 00:33:25,970 --> 00:33:27,572 There will be these ions in there. 652 00:33:27,572 --> 00:33:29,907 These sodium ions will be in there still, right? 653 00:33:29,907 --> 00:33:34,078 If it was Na2O, if it's something else 654 00:33:34,078 --> 00:33:36,547 and it's a different kind of ion that might be leftover, 655 00:33:36,547 --> 00:33:39,951 but the main thing is I've delivered the chemistry 656 00:33:39,951 --> 00:33:41,152 needed to cut this. 657 00:33:41,152 --> 00:33:43,554 And this is called chain scission. 658 00:33:43,554 --> 00:33:50,828 There's a term for it, chain scission, the technical term 659 00:33:50,828 --> 00:33:54,232 for cutting glass pasta. 660 00:33:54,232 --> 00:33:55,700 Well, this is powerful. 661 00:33:55,700 --> 00:33:59,404 This is very powerful because if I can cut this-- 662 00:33:59,404 --> 00:34:01,873 those are the silicate groups, right? 663 00:34:01,873 --> 00:34:06,310 And if I can cut them, then I can change another property. 664 00:34:06,310 --> 00:34:09,813 Look, I can change the viscosity. 665 00:34:09,813 --> 00:34:15,719 I've hit another one of those three reasons why glass forms. 666 00:34:15,719 --> 00:34:18,089 And so I'll show you a slide in a minute that 667 00:34:18,089 --> 00:34:19,690 shows you the change in the viscosity, 668 00:34:19,690 --> 00:34:24,195 but just to give you a sense of what can happen, 669 00:34:24,195 --> 00:34:26,397 how does that impact? 670 00:34:26,397 --> 00:34:27,264 How does that impact? 671 00:34:27,264 --> 00:34:35,572 Well, for silica crystal, the melting point 672 00:34:35,572 --> 00:34:54,458 is greater than 1,200 C. For Tg of soda-lime glass, it's 500 C. 673 00:34:54,458 --> 00:34:59,063 So you can imagine now I've got another mechanism. 674 00:34:59,063 --> 00:35:01,899 I've got another way, not just processing, 675 00:35:01,899 --> 00:35:06,137 not just cooling rate, but chemistry 676 00:35:06,137 --> 00:35:08,406 to mess with this curve. 677 00:35:08,406 --> 00:35:10,208 Because you can imagine now that I 678 00:35:10,208 --> 00:35:15,046 might be able to get to lower and lower transition points. 679 00:35:15,046 --> 00:35:15,713 You see this? 680 00:35:15,713 --> 00:35:18,382 I might be able to get to lower and lower transition points 681 00:35:18,382 --> 00:35:23,988 if these things can move faster and not get locked into a solid 682 00:35:23,988 --> 00:35:30,228 as easily if I add more and more of these chemical scissors. 683 00:35:30,228 --> 00:35:34,465 So maybe this one, now instead of being cooled slower, maybe 684 00:35:34,465 --> 00:35:40,972 this one had more soda than this one. 685 00:35:40,972 --> 00:35:42,907 Maybe now they're cooled at the same rate 686 00:35:42,907 --> 00:35:46,777 but I've changed the amount of impurities, 687 00:35:46,777 --> 00:35:51,182 the amount of oxygen, O2- very specifically, that I've put in. 688 00:35:51,182 --> 00:35:57,555 So it's another way now to change this curve. 689 00:35:57,555 --> 00:36:01,058 Now, these are called-- 690 00:36:01,058 --> 00:36:03,261 the thing that forms the glass-- and we're 691 00:36:03,261 --> 00:36:05,796 really only talking about silica as our glass. 692 00:36:05,796 --> 00:36:09,567 You can make other types of glass not made from silica. 693 00:36:09,567 --> 00:36:11,269 We're talking about silica in this class. 694 00:36:11,269 --> 00:36:15,973 So silicon is the atom that is making those long spaghetti 695 00:36:15,973 --> 00:36:19,010 strands, and it's called the network former. 696 00:36:19,010 --> 00:36:21,078 Silicon is called the network former. 697 00:36:21,078 --> 00:36:24,582 And then the thing that I put in there-- 698 00:36:24,582 --> 00:36:27,451 the thing that I put in there that modified the network 699 00:36:27,451 --> 00:36:29,420 is called the network modifier. 700 00:36:29,420 --> 00:36:34,125 So you can see on this graph that what you've got 701 00:36:34,125 --> 00:36:38,296 is your bridging, the bridging there 702 00:36:38,296 --> 00:36:41,499 that's going between two network formers. 703 00:36:41,499 --> 00:36:45,036 And then you've got these atoms that 704 00:36:45,036 --> 00:36:48,639 are hanging out near a place where you've broken a bridge. 705 00:36:48,639 --> 00:36:50,208 So those would be modifiers. 706 00:36:50,208 --> 00:36:51,676 Those are called network modifiers. 707 00:36:51,676 --> 00:36:54,745 These are just terms that you will hear and see 708 00:36:54,745 --> 00:36:57,782 when you think about glass-- 709 00:36:57,782 --> 00:37:00,451 network formers, network modifiers. 710 00:37:00,451 --> 00:37:02,987 The chemistry that you introduce is modifying the network, 711 00:37:02,987 --> 00:37:06,691 and it's what is done in many, many different ways 712 00:37:06,691 --> 00:37:08,960 with many, many different [INAUDIBLE] 713 00:37:08,960 --> 00:37:11,529 to change the properties of glass. 714 00:37:11,529 --> 00:37:13,231 And so here's the curve that shows 715 00:37:13,231 --> 00:37:17,168 you another kind of important way of looking at this. 716 00:37:17,168 --> 00:37:19,470 And I don't need you to remember all of these terms, 717 00:37:19,470 --> 00:37:20,938 but I want to show you because this 718 00:37:20,938 --> 00:37:22,907 is how glass is engineered. 719 00:37:22,907 --> 00:37:27,144 Remember, today the topic is how do we change the properties? 720 00:37:27,144 --> 00:37:28,512 We talked about the cooling rate. 721 00:37:28,512 --> 00:37:31,682 Now we're talking about adding chemicals. 722 00:37:31,682 --> 00:37:34,518 And so now you're going to work with the glass 723 00:37:34,518 --> 00:37:37,054 to do something with it. 724 00:37:37,054 --> 00:37:39,457 If you're going to do that, this is one of the first plots 725 00:37:39,457 --> 00:37:41,726 you'll look up. 726 00:37:41,726 --> 00:37:43,728 And it shows you-- it plots the temperature. 727 00:37:43,728 --> 00:37:46,497 This really doesn't work at all-- 728 00:37:46,497 --> 00:37:49,233 the temperature on one axis-- so that's like the x-axis-- 729 00:37:49,233 --> 00:37:51,202 and on the y-axis is the viscosity because now 730 00:37:51,202 --> 00:37:53,804 that's the property that we're changing, right, the viscosity? 731 00:37:56,641 --> 00:37:58,676 So there's silica up on the upper right. 732 00:37:58,676 --> 00:37:59,710 Can you see that? 733 00:37:59,710 --> 00:38:03,948 So fused silica, that's basically almost quartz. 734 00:38:03,948 --> 00:38:05,783 That's basically quartz. 735 00:38:05,783 --> 00:38:10,321 So you are really close to making a nice crystal, 736 00:38:10,321 --> 00:38:15,293 but notice how high of viscosity you have versus temperature. 737 00:38:15,293 --> 00:38:18,329 Notice that you're at this very, very high value for viscosity. 738 00:38:18,329 --> 00:38:20,865 It's a really thick material. 739 00:38:20,865 --> 00:38:22,833 And people care a lot about viscosity 740 00:38:22,833 --> 00:38:23,901 when they work with glass. 741 00:38:23,901 --> 00:38:24,402 Why? 742 00:38:24,402 --> 00:38:28,472 Because you need to know, for example, 743 00:38:28,472 --> 00:38:30,708 is the viscosity at a point where I can work with it? 744 00:38:30,708 --> 00:38:31,909 Can I shape it? 745 00:38:31,909 --> 00:38:33,110 That's the bottom. 746 00:38:33,110 --> 00:38:35,146 That's the region that says working range. 747 00:38:35,146 --> 00:38:36,314 I can still shape it. 748 00:38:36,314 --> 00:38:37,181 I can make a window. 749 00:38:39,917 --> 00:38:42,119 There it flows under its own weight. 750 00:38:42,119 --> 00:38:45,456 So now I can shape it and it will lose the shape. 751 00:38:45,456 --> 00:38:48,659 That's kind of important to know if I'm making a glass animal. 752 00:38:51,329 --> 00:38:54,665 There its stress can still be relieved. 753 00:38:54,665 --> 00:38:56,267 Remaining stress can still be relieved, 754 00:38:56,267 --> 00:38:58,102 and up there you can rapidly cool it 755 00:38:58,102 --> 00:38:59,970 without introducing new defects. 756 00:38:59,970 --> 00:39:02,807 But look at the tradeoff between the temperature 757 00:39:02,807 --> 00:39:06,143 that you have to go to and the viscosity and the viscosity 758 00:39:06,143 --> 00:39:07,111 that you have. 759 00:39:07,111 --> 00:39:10,381 So if you go now from this almost quartz 760 00:39:10,381 --> 00:39:11,615 all the way down-- 761 00:39:11,615 --> 00:39:14,618 OK, there you take a little bit of stuff and you put it in, 762 00:39:14,618 --> 00:39:16,454 but it's still 96% silica. 763 00:39:16,454 --> 00:39:18,189 And now you go to boiled silicate. 764 00:39:18,189 --> 00:39:23,594 Remember, it's like 75%, 80% silica plus other additives. 765 00:39:23,594 --> 00:39:26,831 And look at how much you've changed the temperature. 766 00:39:26,831 --> 00:39:28,733 So I can now work with this material 767 00:39:28,733 --> 00:39:34,271 below 1,000 C. That has huge consequences for industry, 768 00:39:34,271 --> 00:39:37,308 for actually making different things out 769 00:39:37,308 --> 00:39:40,444 of glass, which we now do regularly. 770 00:39:40,444 --> 00:39:42,713 And the Romans did it too, but they didn't know why. 771 00:39:42,713 --> 00:39:44,949 They said, well, if you add a little bit of this dirt, 772 00:39:44,949 --> 00:39:46,117 something different happens. 773 00:39:46,117 --> 00:39:48,119 Let's try a little bit of that one. 774 00:39:48,119 --> 00:39:49,053 Now we know. 775 00:39:49,053 --> 00:39:50,554 We know why. 776 00:39:53,257 --> 00:39:55,059 And so this curve now is something 777 00:39:55,059 --> 00:39:58,562 that we understand and we understand how to control it. 778 00:39:58,562 --> 00:40:06,270 And if you go back to the example of making glass tough, 779 00:40:06,270 --> 00:40:10,641 I was just showing you these ions, these sodium ions. 780 00:40:10,641 --> 00:40:12,176 They're left in there. 781 00:40:12,176 --> 00:40:16,914 Well, it turns out that you can put ions into glass, 782 00:40:16,914 --> 00:40:19,917 and maybe you're doing it to change the viscosity 783 00:40:19,917 --> 00:40:22,620 so the thing stays liquid for longer, 784 00:40:22,620 --> 00:40:26,357 and you can maybe work with it in different regimes. 785 00:40:26,357 --> 00:40:28,125 But maybe you're putting the ions in there 786 00:40:28,125 --> 00:40:31,395 to do something else. 787 00:40:31,395 --> 00:40:34,965 And so actually there's a whole another thing 788 00:40:34,965 --> 00:40:39,637 you can do once you have ions in the glass like sodium. 789 00:40:39,637 --> 00:40:42,606 You can substitute them out. 790 00:40:42,606 --> 00:40:45,242 Imagine that I have-- that's what 791 00:40:45,242 --> 00:40:46,610 this next picture is showing. 792 00:40:46,610 --> 00:40:50,281 Imagine that I've got a glass in here, 793 00:40:50,281 --> 00:40:53,617 and those red circles are sodium. 794 00:40:53,617 --> 00:40:56,887 But now I've introduced a different ion on the surface. 795 00:40:56,887 --> 00:40:58,889 That's potassium. 796 00:40:58,889 --> 00:40:59,623 What happens? 797 00:40:59,623 --> 00:41:02,893 Well, if I have a high concentration of potassium 798 00:41:02,893 --> 00:41:04,728 and I put it on a surface of glass that 799 00:41:04,728 --> 00:41:07,364 has a bunch of sodium in it, so now 800 00:41:07,364 --> 00:41:12,036 I've got a glass with sodium ions in it. 801 00:41:12,036 --> 00:41:17,942 And I expose it to a potassium bath. 802 00:41:17,942 --> 00:41:22,112 So now I've got potassium up here. 803 00:41:22,112 --> 00:41:25,549 And what happens is if the concentration is high enough 804 00:41:25,549 --> 00:41:27,818 and the conditions are right, I can get potassium 805 00:41:27,818 --> 00:41:31,322 to go in for the sodium. 806 00:41:31,322 --> 00:41:34,391 And so actually now I can substitute. 807 00:41:34,391 --> 00:41:36,560 So these were here. 808 00:41:36,560 --> 00:41:40,064 I can now substitute those for potassium. 809 00:41:42,800 --> 00:41:46,537 Well, but this is a big deal because potassium 810 00:41:46,537 --> 00:41:48,806 is bigger than sodium. 811 00:41:48,806 --> 00:41:53,077 And so if I am able to on the surface, let's say, 812 00:41:53,077 --> 00:41:56,113 put something bigger in there, then you 813 00:41:56,113 --> 00:41:59,316 can imagine that it's pushing the other stuff 814 00:41:59,316 --> 00:42:01,051 into each other. 815 00:42:01,051 --> 00:42:04,221 That's causing the same stress. 816 00:42:04,221 --> 00:42:15,266 K+ plus bigger than sodium, and this causes this huge surface 817 00:42:15,266 --> 00:42:15,766 tension. 818 00:42:18,769 --> 00:42:24,909 Same principle as tempering, but now I've done it chemically. 819 00:42:24,909 --> 00:42:27,144 This is Gorilla Glass. 820 00:42:27,144 --> 00:42:29,780 This is all phone screens. 821 00:42:29,780 --> 00:42:34,018 This is what they do because you can get really, really 822 00:42:34,018 --> 00:42:35,819 hard glass this way. 823 00:42:35,819 --> 00:42:38,255 And if you go back to these guys, they have a little-- 824 00:42:38,255 --> 00:42:39,757 and this is just a very short video. 825 00:42:39,757 --> 00:42:43,093 They've got this sort of longer videos on the Corning website 826 00:42:43,093 --> 00:42:44,929 that talk about this, and they shoot bullets 827 00:42:44,929 --> 00:42:46,297 through Gorilla Glass. 828 00:42:46,297 --> 00:42:48,799 You can make glass really strong with just 829 00:42:48,799 --> 00:42:51,769 chemical substitutions, and all you're thinking about 830 00:42:51,769 --> 00:42:53,103 is atom size. 831 00:42:53,103 --> 00:42:55,739 Because by putting this larger atom in, 832 00:42:55,739 --> 00:42:58,876 you cause this same kind of compressive stress 833 00:42:58,876 --> 00:42:59,743 at the surface. 834 00:42:59,743 --> 00:43:00,411 [VIDEO PLAYBACK] 835 00:43:00,411 --> 00:43:03,180 - Gorilla Glass, it's been refined over time, 836 00:43:03,180 --> 00:43:06,083 but like all Gorilla Glass variants that came before it, 837 00:43:06,083 --> 00:43:08,352 it is compressive-strength glass. 838 00:43:08,352 --> 00:43:10,921 But it's not made in the same way as we just demonstrated, 839 00:43:10,921 --> 00:43:12,022 the rapid-cooling method. 840 00:43:12,022 --> 00:43:15,726 No, instead Corning uses an ion-exchange process. 841 00:43:15,726 --> 00:43:18,028 To break it down simply, the surface ion 842 00:43:18,028 --> 00:43:20,664 particles that naturally form during the manufacture 843 00:43:20,664 --> 00:43:23,334 are replaced with larger ion particles. 844 00:43:23,334 --> 00:43:25,636 Once exchanged, the larger ion particles 845 00:43:25,636 --> 00:43:27,838 create the same sort of inward pressure 846 00:43:27,838 --> 00:43:29,873 that we see on the Prince Rupert drop. 847 00:43:29,873 --> 00:43:33,510 And with this method they are able to control and manage 848 00:43:33,510 --> 00:43:34,378 the resulting-- 849 00:43:34,378 --> 00:43:35,646 [END PLAYBACK] 850 00:43:35,646 --> 00:43:38,082 The resulting what? 851 00:43:38,082 --> 00:43:41,085 What was he going to say? 852 00:43:41,085 --> 00:43:42,686 I don't know actually. 853 00:43:42,686 --> 00:43:43,420 I don't remember. 854 00:43:43,420 --> 00:43:45,689 I have to go watch it now. 855 00:43:45,689 --> 00:43:47,224 So that's just a video showing you 856 00:43:47,224 --> 00:43:49,226 what I just showed you, which is that that's yet 857 00:43:49,226 --> 00:43:52,730 another way of engineering the properties of glass, 858 00:43:52,730 --> 00:43:54,565 and there are so many more. 859 00:43:56,667 --> 00:43:58,268 One of the points I want to make today 860 00:43:58,268 --> 00:43:59,903 about how to engineer glass-- so we're talking 861 00:43:59,903 --> 00:44:01,405 about how to change this curve. 862 00:44:01,405 --> 00:44:04,441 Maybe we change the viscosity by adding O2 863 00:44:04,441 --> 00:44:07,611 which changes the curve here. 864 00:44:07,611 --> 00:44:08,979 Maybe we change the cooling rate. 865 00:44:12,816 --> 00:44:16,620 Maybe I can use additives, ions in different ways. 866 00:44:16,620 --> 00:44:18,122 But it turns out that we have come 867 00:44:18,122 --> 00:44:20,891 to a place where we can engineer every single one 868 00:44:20,891 --> 00:44:22,359 of these properties. 869 00:44:22,359 --> 00:44:25,229 We can make conducting glass, even though it's usually 870 00:44:25,229 --> 00:44:28,399 been and usually is insulating. 871 00:44:28,399 --> 00:44:31,101 We can make chemically active glass. 872 00:44:31,101 --> 00:44:34,805 As you just saw, we can change the mechanical properties. 873 00:44:34,805 --> 00:44:37,408 There are now flexible rolls of glass 874 00:44:37,408 --> 00:44:40,144 that look literally like Saran wrap almost, but they're glass. 875 00:44:43,180 --> 00:44:45,282 And so it all comes down to the pasta. 876 00:44:45,282 --> 00:44:48,352 And so where we are, if we use the pasta analogy-- 877 00:44:48,352 --> 00:44:51,822 which as you, I think, can understand I really like 878 00:44:51,822 --> 00:44:54,992 because I really like pasta. 879 00:44:54,992 --> 00:44:56,860 This is a great analogy for glass 880 00:44:56,860 --> 00:45:00,864 because it's like in the Roman time, 881 00:45:00,864 --> 00:45:04,201 all we had was one sauce, everything. 882 00:45:04,201 --> 00:45:06,003 Just mix it all in-- 883 00:45:06,003 --> 00:45:11,642 meatballs, pesto, red sauce, carbonara. 884 00:45:11,642 --> 00:45:14,044 I can go on. 885 00:45:14,044 --> 00:45:15,045 And that's all they did. 886 00:45:15,045 --> 00:45:17,381 They just didn't know why things were happening. 887 00:45:17,381 --> 00:45:21,118 But now that we know about the electronic structure of atoms, 888 00:45:21,118 --> 00:45:27,124 we can make glass into any delicious pasta dish we want, 889 00:45:27,124 --> 00:45:28,559 right? 890 00:45:28,559 --> 00:45:31,495 OK, don't eat it, but you know what I mean. 891 00:45:31,495 --> 00:45:33,697 And so I'll give you a couple of examples. 892 00:45:33,697 --> 00:45:35,532 So the point is the last 20 centuries, 893 00:45:35,532 --> 00:45:37,267 we were really just getting warmed up 894 00:45:37,267 --> 00:45:38,569 when it comes to this material. 895 00:45:43,240 --> 00:45:46,677 What the recent understanding of how to engineer this material 896 00:45:46,677 --> 00:45:49,947 has led to are real breakthrough ideas. 897 00:45:49,947 --> 00:45:54,284 And so I'll show you just a couple in my why this matters. 898 00:45:54,284 --> 00:45:56,954 Because glass is, after all, made of-- there 899 00:45:56,954 --> 00:45:58,622 it is up there in case you can't see it. 900 00:45:58,622 --> 00:46:03,227 This is the abundance of elements versus atomic number, 901 00:46:03,227 --> 00:46:05,529 and you notice the very top two elements 902 00:46:05,529 --> 00:46:11,268 are silicon and oxygen. And so it would be really nice if we 903 00:46:11,268 --> 00:46:13,403 could make a lot of stuff out of these really 904 00:46:13,403 --> 00:46:14,772 abundant cheap elements. 905 00:46:14,772 --> 00:46:17,174 Think sand. 906 00:46:17,174 --> 00:46:21,178 Could I take sand and make a lot of stuff out of it? 907 00:46:21,178 --> 00:46:22,980 Well, not if I can't control. 908 00:46:22,980 --> 00:46:27,785 Not if I have to heat it up to 3,000 degrees or its viscosity 909 00:46:27,785 --> 00:46:30,354 isn't what I want or it doesn't give me the properties I want, 910 00:46:30,354 --> 00:46:32,322 but that has changed. 911 00:46:32,322 --> 00:46:34,858 That has fundamentally changed. 912 00:46:34,858 --> 00:46:36,994 So we can now look at materials like this, 913 00:46:36,994 --> 00:46:39,229 these super-abundant materials, and we can completely 914 00:46:39,229 --> 00:46:39,830 rethink them. 915 00:46:39,830 --> 00:46:41,431 And I'll give you one example. 916 00:46:41,431 --> 00:46:42,900 It's already a few years old, but I 917 00:46:42,900 --> 00:46:46,069 think it's just a really cool idea, which 918 00:46:46,069 --> 00:46:47,871 is called the Solar Sinter. 919 00:46:47,871 --> 00:46:50,808 And here he's developed this machine 920 00:46:50,808 --> 00:46:52,843 that is entirely solar powered. 921 00:46:52,843 --> 00:46:54,912 They're solar cells for the electricity. 922 00:46:54,912 --> 00:46:59,616 And it's a focused beam of light from the sun that 923 00:46:59,616 --> 00:47:02,519 gets hot enough to engineer the glass. 924 00:47:02,519 --> 00:47:05,522 So he takes sand from the desert that he's in. 925 00:47:05,522 --> 00:47:08,425 He puts it in a container, and he's got a 3D printer 926 00:47:08,425 --> 00:47:09,593 that he's made. 927 00:47:09,593 --> 00:47:11,495 It's entirely solar powered. 928 00:47:11,495 --> 00:47:15,699 There's no fossil fuels, but he can take sand and turn it 929 00:47:15,699 --> 00:47:18,569 into something structural. 930 00:47:18,569 --> 00:47:21,171 And so there's a vase that he's made, 931 00:47:21,171 --> 00:47:22,673 and you can take that out. 932 00:47:22,673 --> 00:47:24,374 And again, that's just the beginning 933 00:47:24,374 --> 00:47:27,010 of rethinking what we could do with these super-abundant 934 00:47:27,010 --> 00:47:27,845 materials. 935 00:47:27,845 --> 00:47:32,449 Here's an example from also a few years ago from an MIT lab. 936 00:47:32,449 --> 00:47:35,686 This is Neri Oxman's lab, and she's in the Mediated Matter 937 00:47:35,686 --> 00:47:40,224 lab here at MIT, and she's developed a 3D printer. 938 00:47:40,224 --> 00:47:40,891 [VIDEO PLAYBACK] 939 00:47:40,891 --> 00:47:42,693 [MUSIC PLAYBACK] 940 00:47:42,693 --> 00:47:47,698 And so there it is printing something with glass. 941 00:47:47,698 --> 00:47:51,368 And she can print lots of different designs now using 942 00:47:51,368 --> 00:47:52,069 glass. 943 00:47:52,069 --> 00:47:54,404 She has a cool video. 944 00:47:54,404 --> 00:47:56,139 And there is the printhead. 945 00:48:03,580 --> 00:48:38,682 And again, 1,900 Fahrenheit. 946 00:48:38,682 --> 00:48:41,618 I'm not sure that I want a 1,900 Fahrenheit 947 00:48:41,618 --> 00:48:44,721 printer on my desktop. 948 00:48:44,721 --> 00:48:48,258 But as you can imagine, what they had to do-- 949 00:48:48,258 --> 00:48:50,594 I'll just give you one more example and then we'll stop. 950 00:48:50,594 --> 00:48:52,429 What they had to do is understand everything 951 00:48:52,429 --> 00:48:53,430 we've just talked about. 952 00:48:53,430 --> 00:48:55,999 How do you engineer the viscosity, the melting point 953 00:48:55,999 --> 00:48:58,235 to make it all work in a 3D printer? 954 00:48:58,235 --> 00:48:59,870 The last point I'll give you is this. 955 00:48:59,870 --> 00:49:00,537 I love this. 956 00:49:00,537 --> 00:49:01,872 This is from a few years ago. 957 00:49:01,872 --> 00:49:04,775 It's a group in Japan that made a glass that 958 00:49:04,775 --> 00:49:08,111 is as strong as steel. 959 00:49:08,111 --> 00:49:10,080 And what they talk about-- this is what I like. 960 00:49:10,080 --> 00:49:12,649 They say just think of a world where your smartphone wouldn't 961 00:49:12,649 --> 00:49:13,150 shatter. 962 00:49:13,150 --> 00:49:14,985 OK, cool. 963 00:49:14,985 --> 00:49:17,921 Buildings could be bolstered against natural disasters, even 964 00:49:17,921 --> 00:49:18,622 cooler. 965 00:49:18,622 --> 00:49:20,257 And then somehow they bring it down. 966 00:49:20,257 --> 00:49:22,292 Wine glasses are reassuringly safe. 967 00:49:22,292 --> 00:49:24,061 [LAUGHTER] 968 00:49:24,061 --> 00:49:25,829 Was that really a problem? 969 00:49:25,829 --> 00:49:27,564 I don't know. 970 00:49:27,564 --> 00:49:30,367 And what they did, fabrication was 971 00:49:30,367 --> 00:49:33,337 conducted using an aerodynamic levitation furnace where 972 00:49:33,337 --> 00:49:36,106 ingredients were floated in the air using oxygen gas 973 00:49:36,106 --> 00:49:38,875 and melted together using CO2 lasers, 974 00:49:38,875 --> 00:49:41,812 and they get a transparent superglass with 50% alumina. 975 00:49:41,812 --> 00:49:45,816 That was so hard to do because the aluminum didn't 976 00:49:45,816 --> 00:49:47,084 want to be a glass. 977 00:49:47,084 --> 00:49:51,421 It wanted to go and become a metal, a crystal. 978 00:49:51,421 --> 00:49:52,889 But by doing it this way, they were 979 00:49:52,889 --> 00:49:56,193 able to capture it in the disorder. 980 00:49:56,193 --> 00:49:57,427 All right, have a great night. 981 00:49:57,427 --> 00:49:59,329 See you guys on Friday.