Posted on 06/03/2004 1:11:55 AM PDT by LibWhacker
Scientists at Texas Tech University, US, have made a nanocomposite of aluminium and iron oxide that reacts exothermically when ignited. The material could have applications in explosives or as an energy source in MEMS devices or in space.
“Research in nanoenergetics is at a very early stage,” Texas Tech researcher Latika Menon told nanotechweb.org. “Nanoscaled energetic materials are expected to be far superior to existing bulk energetic materials due to an increased reaction interface area and drastically decreased distances between reactants, leading to much faster diffusion-limited processes.”
Techniques for making nanoscaled energetic composites currently include sol-gel processing, which results in nanoscale fuel particles “suspended” in an oxidizer matrix, and powder methods - mixing ultrafine powders of the fuel and oxidizer components. According to Menon, both these methods produce high stored energy densities but are limited by the fact that the particles have different sizes and are separated from each other by a range of distances. This can locally separate the fuel and oxidizer and inhibit self-sustaining processes.
With this in mind, Menon and colleagues used a nanotemplate approach to create a nanocomposite consisting of Fe2O3 nanowires embedded in a thin aluminium film. “If we could create a fuel-oxidizer combination in which the honeycomb was fuel and the pores were oxidizer, or vice versa, then every volume of fuel would have the same oxidizer available and the reaction volumes could be controlled over a certain range,” said Menon. “In principle, this is far superior to the powder and sol-gel methods.”
The researchers made a honeycomb-like alumina template by electrochemical anodization of an aluminium foil in an acid. They were able to tailor the diameter of the template’s pores by altering the voltage and the acid used, producing pores between 10 and 150 nm in size.
The team then electrodeposited iron inside the template pores, which they later oxidized to make Fe2O3 nanowires. After various additional steps, the researchers added a 50 nm layer of aluminium on top of the nanowires, forming a structure in which the nanowires were partially embedded in the aluminium layer.
“Aluminium oxidizes rapidly when exposed to oxygen, so we needed to discover a procedure that would place the iron oxide in direct contact with aluminium without having the aluminium in air or water,” said Menon. “We tried several approaches before learning that by making iron oxide nanowires in the templates, exposing them by chemical etching, then coating them with aluminium in an ultrahigh vacuum chamber, we could obtain iron oxide in direct contact with aluminium without aluminium oxide forming.”
Igniting samples of the nanocomposite using a butane flame, resistive heating element or a laser caused them to burn with a flame temperature of around 4000 °C, a value that did not depend on the ignition temperature. The scientists reckon that the energy released was about 0.4 J/sq. cm - around a thousand times higher than the amount released by a purely surface reaction, as for a planar film.
Now, the researchers are studying the reaction mechanism, thermodynamics and kinetics of the ignition process. “The reactions are scientifically interesting, since they are based on interdiffusion and are highly energetic,” said Menon. “We are also interested in exploring other material combinations and improved fabrication approaches that promise greater energy release upon ignition. The interdiffusion reaction also leads to incomplete reaction and possibly to new materials, which need to be investigated.”
Hmm. Is this a kind of mega-thermite reaction?
I'm no chemist, but it kind of looks like it, doesn't it? Imagine a 2,000 pound bunker buster with the explosive force of a 1 kiloton mini-nuke, without the radiation. Hope they keep a lid on the R&D details. Hate to see it turn up in the hands of terrorists 20 years from now.
Tooks the words right out of my mind. Same formula, same reaction, just micro scale. (Nanoscale I guess to sound different.) Just think, maybe they'll stumble onto using magnesium to create nanoflares.
Bombs that can burn aren't a desirable safety feature.
Forget the Daisy Cutter. We're taking about taking a tank out or just about anything else more that matter with a single, bullet sized object.
Hmmm... I wonder what the detonation velocity was. Imagine a small sphere of such a material surrounding a miniature plutonium pit. That could send Jihadis off to meet their virgins by the boxcar load with little in the way of colateral damage.
> Is this a kind of mega-thermite reaction?
Yes. This is just an ultra-fast burning thermite.
From a chemist's standpoint, it is not going to release more energy than the same mass of regular thermite, but it will react completely within microseconds.
From a chemical energy standpoint, nothing should beat beryllium reacted with ozone. That combination has the highest known energy per unit mass. Rocket scientists have been unable to find a way to make them combine efficiently, though.
This may also help improve the thrust of Solid Rockets.
Imagine 2-4 times as many Trident missiles in a Sub with the same range because the Solid rockets are much smaller.
Not to mention what it could do for privatizing space travel, by simply changing the fuel Rutans SS1 can achieve the altitude for the X-prize plus more with the same size vehicle.
Interesting possibilities.
The old Boys anti-tank rifles will once again be used on a battlefield...
The reaction is deflagration not detonation, so we are talking about burning, not booming. No daisy cutters, but propellants, anti-tank, and metal cutting.
4000 °C bump
What an awesome, sobering read by Lev Navrozov you posted in that link. Please post that as a FR article.
Wonder when they're going to start making fireworks out of this!
Semper Fi
Like most high energy density innovations, the major problem will be safety and reliability. I vividly remember a slide show years ago where a scientist showed me the before and after slides of his lab when a 10 MILLIGRAM sample of a flourine compound "decomposed" spontaneously. The lab was leveled and an assistant lost an arm. This stuff really wants to go BOOM and its hard to restrain it.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.