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An atomic examination of the films used to protect the metal from corrosion could lead to more efficient films in the future for a variety of metal-based objects such as building materials, high-tech batteries and turbine engines.
A research collaboration of scientists from Northwestern University, the University of Virginia, and the University of Wisconsin-Madison found that protective films to prevent metal corrosion develop new structures and compositions based on the growth rate of the oxide.
"That changes a lot of things about how we understand these oxide films and opens the door to radically new methods of protecting metals," said Laurence Marks, professor of materials science and engineering at the McCormick School of Engineering in Northwestern, in a statement. . "We now know that there are ways to predict the chemical composition of these films, which we can exploit to make protective films last much longer."
To look deep into the oxides used in protective films, the team used experimental techniques and advanced theoretical modeling that allowed them to analyze oxide films at the atomic level and to decipher the way atoms are finally organized.
The researchers focused on oxides formed on alloys composed of nickel and chromium, widely used in many applications such as the heating elements of a toaster or aircraft engines, as well as in applications where water is present, such as dental implants. .
Scientists have known for a long time that these oxides work hot and resist corrosion. However, it was also thought that nickel formed a separate oxide or dissolved.
The researchers found that this theory was incorrect and that the oxide contained a substantial amount of nickel atoms that could not escape the oxide in time and become captured in the interior.
The fraction of nickel captured depends on the rate of growth of the oxide, which occurs when metals react with oxygen in the air at high temperatures, as well as when they react. with water.
The atoms captured in the oxide modify many properties of the film.
With this information, researchers can design a method to deliberately trap atoms into oxides in new ways and modify their behavior.
"We are close to the limits of what we can do with aircraft engines, for example," said John Perepezko, IBM-Bascom Professor of Materials Science and Engineering at the University of Wisconsin-Madison. and in another author of the study. A declaration. "This new vision of protective oxide formation opens up many new ways to build better engines.
The study was published in Letters of physical examination.
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