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| Metallic glass: a drop of the hard stuff |
| 2005-04-05 |
| I thought this was cool. IN THE movie Terminator 2, the villain is a robot made of liquid metal. He morphs from human form to helicopter and back again with ease, moulds himself into any shape without breaking, and can even flow under doorways. Now a similar-sounding futuristic material is about to turn up everywhere. It is called metallic glass. In the past year, researchers have made metallic glass three times stronger than the best industrial steel and 10 times springier. Almost a match for the Terminator, in other words. Metallic glass sounds like an oxymoron, and in a way it is. It describes a metal alloy with a chaotic structure. While metal atoms normally arrange themselves in ordered arrays, or crystals, the atoms in a metallic glass are a disordered jumble, rather like the atoms in a liquid or a glass. And although strictly speaking a metallic glass isn't a liquid, because the atoms are fixed in place, one company is already marketing the stuff as "liquid metal". It is the unusual structure that makes metallic glass so promising. In crystalline metal alloys, the atoms are ordered within regions called "grains", and the boundaries between the grains are points of weakness in the material. Metallic glasses, however, have no grain boundaries, so they are much stronger. Hit a crystalline metal with a hammer and it will bend, absorbing some of the energy of the blow by giving way along grain boundaries. But the atoms in an amorphous metal are tightly packed, and easily bounce back to their original shape after a blow (see Diagram). These materials lack bulky crystalline grains, so they can be shaped into features just 10 nanometres across. And their liquid-like structure means they melt at lower temperatures, and can be moulded nearly as easily as plastics. |
| Posted by:phil_b |
| #19 Phil is correct. In olden days, the process for making panes of glass was imperfect and tended to create panes that were thicker at one end. There are a number of basic technologies that we take for granted, like glass panes, or wire making, that were very important when discovered. My brother's senior thesis demonstrated that the strongest point in a cracked pane of glass is at the exact point of the crack. Interestingly odd. I have to wonder about all this. The structure of metal gives it its strength. Mercury, after all, is a liquid metal, at room temperature. |
| Posted by: Chuck Simmins 2005-04-05 8:57:36 PM |
| #18 Itn's flow allright Db ima hope thisn make a good slinky |
| Posted by: half 2005-04-05 7:15:31 PM |
| #17 Deacon, apparently old glass flowing is a myth. A possible explanation for what you and others have seen is the glass panes were unevenly manufactured and the thinner end would be installed at the top becuase this would let in more light which is after all the purpose of a window. |
| Posted by: phil_b 2005-04-05 5:19:47 PM |
| #16 Robert, what I should have said is OLD glass. Modern glass doesn't flow but if the glass is old enough and has been in a verticle position long enough it will pool at the bottom, not much,but it will. This is only true of very old, and probably poorly made, glass. When I was practicing Architecture and renovated several buildings over 100 years old nearly all the panes were like that. They weren't formed like that. The glass had actually slightly bulged over the stops at the bottom. Very interesting phenomanon. |
| Posted by: Deacon Blues 2005-04-05 3:32:32 PM |
| #15 What use is a glass knife? Same as any knife - cutting things. |
| Posted by: mojo 2005-04-05 3:17:17 PM |
| #14 What use is a chocolate-covered manhole cover? Survival rations on an alien planet, of course. Jackal -- that's odd. I actually managed to find the story with Google using my mis-remembered version of the title. Deacon -- glass doesn't flow: http://tafkac.org/science/glass_flow.html |
| Posted by: Robert Crawford 2005-04-05 12:49:03 PM |
| #13 JFM - But, but, but, the hippie sandal wearing Archeo-astronomy professor in college told me that they were deadly warriors! Could he have been wrong? ;) |
| Posted by: Laurence of the Rats 2005-04-05 12:41:39 PM |
| #12 Mrs. Davis, glass is technically a liquid. If you ever visit a house that is more than 80 or 100 years old look at the bottom of the window panes. The glass will be thicker at the bottom because gravity has caused the glass to flow downward. |
| Posted by: Deacon Blues 2005-04-05 12:32:01 PM |
| #11 What use is a glass knife? Its more useful than the glass hammer ! |
| Posted by: MacNails 2005-04-05 12:07:24 PM |
| #10 Here is what the Aztecs have been waiting for! They managed to be pretty deadly with glass knives (obsidian). No they weren't (read the chapter about Cortez in Victor David Hanson's "Carnage and Culture"). In fact while obsidian flakes increased the lethality of their weapons they could not inflict deep wounds with them even against unarmored or lighthly armored (padded cloth) indigenous opponents, let alone against the iron armor of the Spanish. They simple weren't in the same league than the Spanish swords who could pierce a man side to side or cut members and heads in a single blow. Whenever possible the Aztecs used weapons abandonned by the Spaniards. In fact the main danger for the Spanish was not Aztec's weapons but exhaustion who allowed the Aztecs to overpower and capture them. At Otumba the Aztecs were 200 to one against the Spanish and were still crushed. |
| Posted by: JFM 2005-04-05 11:52:43 AM |
| #9 What use is a chocolate-covered manhole cover? |
| Posted by: mojo 2005-04-05 11:09:56 AM |
| #8 I keep thinking of Star Trek's Transparent Aluminum |
| Posted by: mmurray821 2005-04-05 11:01:03 AM |
| #7 IN THE movie Terminator 2, the villain is a robot made of liquid metal. He morphs from human form to helicopter and back again with ease... He didn't morph into a helicopter. Sheesh... |
| Posted by: Dar 2005-04-05 10:38:13 AM |
| #6 RC: Is What good is a glass dagger what you meant? Cool story. Thanks, phil_b; though I went into EE instead, I found metallurgy quite interesting. |
| Posted by: Jackal 2005-04-05 10:20:16 AM |
| #5 *sigh* "What Use is a Glass Knife" is the title of a short story by Larry Niven. |
| Posted by: Robert Crawford 2005-04-05 10:16:14 AM |
| #4 By pouring molten metal onto a cold, rapidly rotating copper cylinder, he could make sheets of "superfrozen" amorphous metal. I helped do this for a summer in grad school. It was a most impressive display. The molten metal would be in contact with the wheel for just a second or so, then it would fly up into the air, still glowing, and onto the floor, where you'd have to pick it up with tweezers. Needless to say, we weren't to the point of making golf clubs. I wasn't too surprised (reading the article) that they found this stuff was brittle; while crystalline materials can shear on the crystal boundaries, they tend to be tough in other directions. Another form of the material has a crystalline structure in one direction, but is "glassy" in the others. These are quasicrystals, which is what we were working on. The editorial comments in this article are way over the top; metallic glasses are neither liquid nor transparent. |
| Posted by: Angie Schultz 2005-04-05 9:59:57 AM |
| #3 #1 What use is a glass knife? Depends on whether a metal detector picks it up. I thought glass was a liquid. |
| Posted by: Mrs. Davis 2005-04-05 9:56:54 AM |
| #2 RC -Glass knives! Here is what the Aztecs have been waiting for! They managed to be pretty deadly with glass knives (obsidian). Made swords, even, by putting flakes between layers of wood. :) |
| Posted by: Laurence of the Rats 2005-04-05 9:45:44 AM |
| #1 What use is a glass knife? |
| Posted by: Robert Crawford 2005-04-05 9:32:08 AM |