New metal matrix foam floats on water
13 May 2015
Researchers from New York University Polytechnic of Engineering have demonstrated a new metal matrix composite that is so light that it can float on water.
Although syntactic foams have been around for many years, this is believed to be the first development of a lightweight metal matrix syntactic foam. The work was carried out by a team of researchers from Deep Springs Technology (DST) and the New York University (NYU) Polytechnic School of Engineering.
Their magnesium alloy matrix composite is reinforced with silicon carbide hollow particles and has a density of only 0.92g/cc. Not only does it have a density lower than that of water, it is strong enough to withstand the rigorous conditions faced in the marine environment.
"This new development of very light metal matrix composites can swing the pendulum back in favour of metallic materials," say NYU's Professor Nikhil Gupta. "The ability of metals to withstand higher temperatures can be a huge advantage for these composites in engine and exhaust components, quite apart from structural parts."
The syntactic foam made by DST and NYU captures the lightness of foams, but adds substantial strength. The material starts with a matrix made of a magnesium alloy, which is then turned into foam by adding strong, lightweight silicon carbide hollow spheres developed and manufactured by DST.
A single sphere's shell can withstand a pressure of over 25,000psi before it ruptures. The hollow particles also offer impact protection to the syntactic foam because each shell acts like an energy absorber during its fracture.
The composite can be customised for density and other properties by adding more or fewer shells into the metal matrix to fit the requirements of the application. This concept can also be used with other magnesium alloys that are non-flammable.