Multi-layer reactive foil: no fuel, no oxygen, tons of heat

today on applied science I'd like to show you an unusual material this is a tiny little piece of sheet metal it's very thin about 60 microns thick and if we take this and just use a couple batteries connected to some wires and strike them to make a little Spark you can see it releases a ton of heat nearly melting itself in the process and what we're left with is this very brittle sort of transformed piece of metal let's see that in close up I also used my trusty Kronos high speed camera to get some high-speed video of the reaction taking place and you can see that there's like a front moving through the metal it's really cool apparently it's moving about eight meters per second here let's set off another one it's actually very um easy to set off with the with just a little bit of electricity but note that the electricity has nothing to do with it it's just the heat of the spark that does it so you can actually set these off with a hot soldering iron or a laser pulse even so where is all this energy coming from well the sheet metal is made up of hundreds of layers alternating layers of aluminum and nickel and they have to be really thin so the metals can react with each other the aluminum is maybe about 60 nanometers thick and the nickel is about 40 nanometers thick I think I don't actually have the specs for this commercial product but the reason that the aluminum is a little bit thicker is to compensate for its lower density because what we eventually want is this inner metallic compound nickel aluminide and I think it's one to one I'm actually not positive about this but you basically want one atom of nickel and one atom of aluminum and as it turns out that compound has less energy it's in a lower energy State than the materials by themselves do which seems a little counterintuitive obviously if you had a big chunk of aluminum and a big chunk of nickel and you put them together it's not like you get any heat at the interface but again it's because that the materials have to be really well mixed with each other at the nanometer scale to get this thing started and as we saw it only takes a little bit of heat so as if a tiny Speck of this starts reacting it releases enough heat to keep the reaction going and that's why you have this reaction front that moves through the material basically starting wherever this spark or laser pulse and ignited it it's not really ignited it's initiated it and then this front moves through because this is a reaction between two metals there isn't really a fuel or an oxidizer meaning this works in vacuum or underwater or any sort of circumstance and another interesting outcome of that is that it doesn't release anything unlike most you know detonations or explosions or whatever there's no gas that's being released and that is in fact one of the properties that really makes this a commercial product this is made by the indium corporation which makes all kinds of interesting soldering equipment and these are specially made to solder difficult to solder things because it releases the heat so fast and there's no gas that's going to push the materials part so the ways these things are used is to assemble two very thin sheets of solder next to the energetic sheet metal the nickel aluminum alloy and you put all this stuff in a press and then start you know initiate the energetic material and it melts the solder and creates a solder joint all within milliseconds so we're going to give that a shot here okay this is the first time I've tried this but I'm going to attempt to solder something to this beefy chunk of bronze here and if normally if you were going to solder something to this you'd have to heat the whole thing up to soldering temperature because this is going to Wick heat away so fast that's the beauty of this system here is that the heat is released so quickly that the surface is soldered before the base material even has time to heat up so the first thing we need is a really thin piece of solder it hadn't it has to be a uniform little sheet of solder and I made this by melting some solder and pressing it between two glass microscope slides and I used a microscope cover slip as the spacer so this is 150 microns thick which I think is still way too thick I think it should be an even thinner layer but I couldn't I couldn't get it to work I couldn't squeeze it out much thinner so we'll start with one piece of solder there and then we'll put in the energetic compound and then we will put in another piece of solder and what I'm going to solder to this large block there is this brass pipe fitting and I've sanded down the hex flat so that it should give a nice a nice surface right there and then we apply some pressing Force wow okay so it didn't stick at all uh let's try changing a few things all right well we got plenty of um squeezed out so as it turns out the planarity you know not surprisingly is pretty important and after reducing the thickness of the solder and getting everything really planar and turning the parts on the lathe so that the Finish is really nice it seems to be kind of working it's still not really so great you can see we got some amount of um of contact I mean the solder didn't wet the surface fully I've done a little bit more reading and it's it turns out that if you want to solder something that's really heat sinking like this bronze you might need a thicker layer of energetic material so this stuff is intended for bonding sputtering targets which may not be quite as conductive or as massive as this piece that we're trying to solder but as you can see it's it's starting to get there it actually did wet the surface a little bit so anyway I just wanted to make a quick video kind of showing you this thing and maybe it'll appear in a project later on all right I hope you found that interesting see you next time bye

Channel: Applied Science

Views: 220,759

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Id: eGj4jfYhDxA

Length: 6min 8sec (368 seconds)

Published: Sun May 28 2023