This Floating Metal Will Make Feather-Light Warships

Illustration for article titled This Floating Metal Will Make Feather-Light Warships

No, that's not a sponge. It's a piece of metal that's light enough to float. Researchers at New York University, who invented the substance, say it's also strong enough to build boats with.

This metal is called a syntactic foam. It's a magnesium alloy riddled with hollow silicon carbide spheres, a bit like metallic Swiss cheese. Though it's slightly lighter than water, it's strong enough to withstand pressures of 25,000 pounds per square inch (about ten times the pressure you’d feel one mile deep in the ocean).

Many modern boats are already built out of metal, so what’s the big deal? Consider that a square chunk of steel won’t float; boats are shaped the way they are so that their hulls will displace enough water to make the boat buoyant. But materials scientist Nikhil Gupta's syntactic foam is lighter than water, so it floats on its own. Ship designers using the new material would still have to reckon with the weight of crew, cargo, and onboard systems, but the hull itself would no longer weigh the ship down.


Gupta told Vice that the new material will be ready for production in about three years, and he expects to see the first Navy prototypes around that time. He published his work in the current issue of the International Journal of Impact Engineering.

Syntactic foam isn’t a new idea. Since the 1960s, polymer foams filled with glass or ceramic spheres have been used in buoys, submersibles, and some aerospace applications. Metal syntactic foams are more recent. One of the most common is aluminum foam filled with ceramic spheres, but engineers have also developed magnesium, steel, and titanium foams. Not only are these foams lighter than a solid block of the metal, they’re also better at absorbing impact energy, which is a useful trait in something like a warship hull.

[Vice, IJIE]

Image: NYU via Science 2.0


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People have been looking into MMC’s for structural applications for a while. The fact that it is a magnesium alloy isnt necessarily a problem as far as combustion goes: Magnesium alloys have been used for quite a while in the automotive and aerospace markets. The alloy they are using does have a flammability hazard, and reacts with water aggressively (like all Mg alloys). Here is the MSDS for the alloy they are talking about:

It also makes note that we arent talking about using JUST the alloy; the SiC is permeated throughout the matrix. If you have enough of the SiC, you can significantly dampen the effects of the exothermic oxidation of the magnesium or actually prevent the chain reaction. I worked for a company that used thermite to test for thermal shock in the silicon carbide ceramics, and with enough non-reactive material (I.E. refractory ceramics), the thermite wouldnt even light. You still need enough metal to start that chain reaction, and depending on how much SiC you have int he composite, you might actually mitigate those concerns. The article published doesnt go into any detail about the flammability of the composite though, just says that:

“Magnesium is a promising low density metal, but its applications have been limited to high-end automobiles, in-part due to its flammability and difficulty in processing. Development of new alloys and processing methods has resulted in mitigating the limitations of magnesium such as flammability and corrosion, enabling applications in a variety of weight sensitive structures.”

There are quite a few factors that go into whether something will ignite and damning it just because the pure element and un-modified alloy can ignite is a bit unfair. It isnt JUST a magnesium alloy any more. Still though, I would like to see how it reacts to an aqueous environment and to ignition-level heat/impact.