Self-healing metal oxides could protect against corrosion. Researchers find an ultrathin layer of aluminum oxide, though solid, can flow like a liquid instead of cracking.
Researchers have found that a solid oxide protective coating for metals can, when applied in sufficiently thin layers, deform as if it were a liquid, filling any cracks and gaps as they form.
The thin coating layer should be especially useful to prevent leakage of tiny molecules that can penetrate through most materials, such as hydrogen gas that could be used to power fuel-cell cars, or the radioactive tritium (a heavy form of hydrogen) that forms inside the cores of nuclear power plants.
Most metals, with the notable exception of gold, tend to oxidize when exposed to air and water. This reaction, which produces rust on iron, tarnish on silver, and verdigris on copper or brass, can weaken the metal over time and lead to cracks or structural failure. But there are three known elements that produce an oxide that can actually serve as a protective barrier to prevent any further oxidation: aluminum oxide, chromium oxide, and silicon dioxide.
Ju Li, a professor of nuclear engineering and science and of materials science and engineering at MIT and senior author of a paper describing the new finding, says “we were trying to understand why aluminum oxide and silicon dioxide are special oxides that give excellent corrosion resistance.” The paper appears in the journal Nano Letters.