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New Magnesium-Alloy Foam From NYU's Nikhil Gupta Floats On Water
Jason Koebler writes: A new class of magnesium-alloy syntactic foam, which is made out of hollow particles to lower its weight and density is one of the strongest metals for its weight and density ever developed, which makes it ideal for use in boats. Developed by Nikhil Gupta at NYU Polytechnic University, the alloy is 44 percent stronger than similar, aluminum-based foams, and each individual sphere within the foam can withstand pressure of more than 25,000 pounds per square inch before breaking, which is roughly 100 times the pressure exerted by water coming out of a firehose. Gupta's foams are currently used by the Navy and he suspects this one will be ready for use in warships within three years.
"magnesium alloy"
As a comparison, Inox, or "stainless steel" is a steel alloy. Steel is very incompatible with water, and could corrode away very quickly if it got wet. And yet, add that chromium to create a new alloy, and suddenly you've got a slightly softer metal that doesn't oxidize.
See also: transparent aluminium, silicon vs silicone, etc.
Science fact: magnesium != magnesium alloy
There are two types of people in the world: Those who crave closure
Interesting question. It looks like it isn't air-in-magnesium - it's hollow air-filled SiC beads inside magnesium.
(TFA doesn't mention the SiC part directly, but you can find more info in the linked research paper from TFA.)
retrorocket.o not found, launch anyway?
Syntactic foams have many very good properties. They use hollow ceramic beads embedded in a metal matrix. The beads are usually filled with an inert gas, most commonly nitrogen, often at far higher than 1 atm pressure. They are not particularly flammable, because the ceramic doesn't burn, and the pressurized N2 released during combustion retards the flame. It is also possible to embed halogenated frame retardants in the beads. They are strong in compression because the foam can absorb shock. They handle compression, tension, and shearing well because the beads inhibit crack propagation, sort of like how a missing link stops a zipper from unzipping. They resist heat conduction and melting better than solid metals. And, of course, they are light.