Researchers from Binghamton University (Binghamton, New York, USA), the University of Pittsburgh (Pittsburgh, Pennsylvania, USA), and the Brookhaven National Laboratory (Upton, New York, USA) have collaborated on a project to study the structural and functional properties of metals and the process of making “green” steel. Their latest research was recently published in the journalScience Advances.
When water vapor meets metal, the results include corrosion and the formation of a thin inert layer, through the passivation process, that acts as a barrier against further deterioration. Although the exact chemical reaction isn’t well understood on an atomic level, researchers are relying on a technique known as environmental transmission electron microscopy (TEM) that allows them to direct view molecules interacting on the tiniest possible scale.
The research team introduced water vapor to clean aluminum samples and observed the surface reactions. One member of the team, Prof. Guangwen Zhou — a faculty member at Binghamton University’s Thomas J. Watson College of Engineering and Applied Science — has been probing the secrets of atomic reactions since joining the Department of Mechanical Engineering in 2007.
“This phenomenon is well-known because it happens in our daily lives,” says Zhou. “But how do water molecules react with aluminum to form this passivation layer? If you look at the [research] literature, there’s not much work about how this happens at an atomic scale. If we want to use it for good, we must know, because then we will have some way to control it.”
The researchers discovered something that had never been observed before. In addition to the aluminum hydroxide layer that formed on the surface, a second amorphous layer developed underneath it, which indicates there is a transport mechanism that diffuses oxygen into the substrate.
“Most corrosion studies focus on the growth of the passivation layer and how it slows down the corrosion process,” Zhou says. “To look at it from an atomic scale, we feel we can bridge the knowledge gap.”
The cost of repairing corrosion worldwide is estimated at $2.5 trillion a year, which is more than 3% of the global GDP, so developing better ways to manage oxidation would be an economic boon. Additionally, understanding how a water molecule’s hydrogen and oxygen atoms break apart to interact with metals could lead to clean-energy solutions, which is why the U.S. Department of Energy (DOE) funded this research and Zhou’s similar projects in the past.
“If you break water into oxygen and hydrogen, when you recombine it, it’s just water again,” Zhou says. “It doesn’t have the contamination of fossil fuels, and it doesn’t produce carbon dioxide.”
Because of the clean-energy implications, the DOE has regularly renewed Zhou’s grant funding over the past 15 years.
“I greatly appreciate the long-term support for this research,” he says. “It’s a very important issue for energy devices or energy systems, because you have a lot of metallic alloys that are used as structural material.”
Source: Bing U News, www.binghamton.edu.