Lightweight metal composite floats on water
In a development that could mean big things in the automotive andmarine industries, researchers from Deep Springs Technology (DST) and the NewYork University Polytechnic School of Engineering have created a new metalmatrix composite that is so light it can float on water.
The magnesium alloy matrix composite is what is known as asyntactic foam: a type of composite material created by filling a metal,polymer or ceramic matrix with hollow particles. In this case, a magnesiumalloy matrix is reinforced with hollow particles of silicon carbide, resultingin what the researchers claim is the world's first lightweight metal matrixsyntactic foam.
This structure helps give the material a density of 0.92 grams percubic centimeter, which is less than the 1 g/cc density of water, therebygiving it the ability to float on water and potentially be used in theconstruction of marine vessels that stay afloat even after experiencing damageto their structure. Furthermore, the researchers say it is also strong enoughto withstand rigorous marine conditions.
Additionally, the material also boasts heat resistance propertiesthat would make it a viable alternative to the lightweight polymer matrixcomposites that have been the focus of much research and development for use inboth marine vessels and automobile components as a replacement for heaviermetal-based components.
"This new development of very light metal matrixcomposites can swing the pendulum back in favor of metallic materials," saysNikhil Gupta, an NYU School of Engineering professor in the Department ofMechanical and Aerospace Engineering and the study’s co-author. "The abilityof metals to withstand higher temperatures can be a huge advantage for thesecomposites in engine and exhaust components, quite apart from structural parts."
The material starts out as a matrix made of magnesiumalloy, which is turned into a foam through the addition of silicon carbidehollow spheres developed by DST. These lightweight spheres are extremelystrong, with the shell of a single sphere able to withstand over 25,000 PSI ofpressure before rupturing. As well as adding strength, the spheres also offerimpact protection by acting like an energy absorber.
Modifying the amount of spheres that are added to thematrix allows the composite's density and other properties to be customized tosuit different applications. Just a few potential applications"floated" by the researchers include boat flooring, automobilecomponents, buoyancy modules and vehicle armor. This last example may be related to the fact that the US Army Research Laboratory collaborated on the research.
The team says the material could be in prototypes for testing within three years.
The team's study appears in the International Journalof Impact Engineering.