Mechanical Engineering News
Guangwen Zhou published in Proceedings of the National Academy of Sciences
Study: Atom-high steps halt oxidation of metal surfaces
By Karen McNulty Walsh
Published on December 29, 2014
Rust never sleeps. Whether a reference to the 1979 Neil Young album or a product designed to protect metal surfaces, the phrase invokes the idea that corrosion from oxidation — the more general chemical name for rust and other reactions of metal with oxygen — is an inevitable, persistent process. But a new Binghamton University study reveals that certain features of metal surfaces can stop the process of oxidation in its tracks.
The findings, published this week in the Proceedings of the National Academy of Sciences, could be relevant to understanding and perhaps controlling oxidation in a range of materials — from catalysts to the superalloys used in jet engine turbines and the oxides in microelectronics.
The experiments were performed by a team led by Guangwen Zhou, associate professor of mechanical engineering at Binghamton University, in collaboration with Peter Sutter of the Center for Functional Nanomaterials (CFN) at the U.S. Department of Energy's Brookhaven National Laboratory.
The team used a low-energy electron microscope (LEEM) to capture changes in the surface structure of a nickel-aluminum alloy as "stripes" of metal oxide formed and grew under a range of elevated temperatures.
The metal Zhou wanted to study, nickel-aluminum, has a characteristic common to all crystal surfaces: a stepped structure composed of a series of flat terraces at different heights. The steps between terraces are only one atom high, but they can have a significant effect on material properties. Being able to see the steps and how they change is essential to understanding how the surface will behave in different environments, in this case in response to oxygen, Sutter said.
Said Zhou, "The acquisition of this kind of knowledge is essential for gaining control over the response of a metal surface to the environment."
Scientists have known for a while that the atoms at the edges of atomic steps are especially reactive. "They are not as completely surrounded as the atoms that are part of the flat terraces, so they are more free to interact with the environment," Sutter said. "That plays a role in the material's surface chemistry."
The new study, supported by the Department of Energy Office of Science, showed that the aluminum atoms involved in forming aluminum oxide stripes came exclusively from the steps, not the terraces. But the LEEM images revealed even more: The growing oxide stripes could not "climb" up or down the steps, but were confined to the flat terraces. To continue to grow, they had to push the steps away as oxygen continued to grab aluminum atoms from the edges. This forced the steps to bunch closer and closer together, eventually slowing the rate of oxide stripe growth, and then completely stopping it.
"For the first time we show that atomic steps can slow surface oxidation at the earliest stages," Zhou said.
However, as one stripe stops growing, another begins to form. "As the oxide stripes grow along the two possible directions on the crystal, which are at right angles to one another, one ends up with these patterns of blocks and lines that are reminiscent of the grid-based paintings by Mondrian," Sutter said. "They are quite beautiful" and persistent after all.
Still the details and differences of the two types of surfaces could offer new ways scientists might attempt to control oxidation depending on their purpose.
"Oxides are not all bad," Sutter said. "They form as a protective layer against corrosion attack. They play important roles in chemistry, for example in catalysis. Silicon oxide is the insulating material on microelectronic circuits, where it plays a central role in directing the flow of current."
Knowing which kind of surface a material has and its effects on oxidation — or how to engineer surfaces with desired properties — might improve the design of these and other materials.
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Mechanical Engineering graduate students receive Graduate Excellence Award in Research.
Xiaoming Chen – Mechanical Engineering
Xiaoming Chen’s research focuses on investigating the mechanical properties of carbon and boron nitride nanotubes and their polymer nanocomposites, part of a broad effort to develop next-generation, light-weight and high-strength multifunctional engineering materials, particularly for aerospace applications. In collaboration with NASA and the National Institute of Aerospace, and financially supported by the Air Force Office of Scientific Research, he tackles very challenging problems and has made several breakthroughs using state-of-the-art nanomechanical testing techniques. His research findings help to better understand the mechanical strength of nanotube structures and the local stress transfer on the nanotube-polymer interfaces, both critical for design and optimization of innovative nanotube-based material systems. He has first-authored three journal articles and has nine published articles to his credit. He has made nearly 20 conference presentations and holds one patent. His nominator writes that his research achievements clearly show his capability of delivering cutting-edge research in the emerging fields of nanoscience and engineering.
Vadim Bromberg – Mechanical Engineering
Called a truly extraordinary experimentalist by his nominator, Vadim Bromberg plans and executes very complex experiments in the fields of fluid dynamics and materials science, and then processes and interprets the data at a level that is world-class. A complete researcher, he possesses a mature and fundamental knowledge of fluid dynamics and transport science, as well as strong knowledge of chemistry and materials science. He has five peer-reviewed publications, with four more in review or in preparation. Among his projects, he conceptualized and developed a fast, material-efficient and fully scalable “drop-on-demand” inkjet printing process that allows precise deposition of small droplets of functional ink in a variety of patterns on a given substrate surface. This process has exceptional advanced imaging and data acquisition capabilities, with 90 percent improvement over current state-of-the-art inkjet printing capability, and has resulted in one patent filing. His work holds significant potential in the emerging additive manufacturing field.
Taken with permission from http://www.binghamton.edu/inside/index.php/inside/story/7860/2014-graduate-excellence-award-winners/
Dr. Peter Huang Receives TAE Award
A collaborative project between Dr. Peter Huang ( Mechanical Engineering department) and Dr. Tomonari Nishikawa (Cinema department) was funded by the 2013 Health Sciences Transdisciplinary Area of Excellence. Digital technology has expanded the way artists express their ideas, and in cinema most filmmakers today choose digital video as their medium mostly for cost and distribution reasons. Recently, Fujifilm announced its cessation of the production of most motion picture filmstrips, and many film labs have closed down in the last decade. Thus, now is a crucial time to examine the dying film medium with its many artistic values still left unexplored. Through this project, we will create a live-processed film/video installation to re-examine the 3D film material and its uniqueness by combining engineering and artistic filmmaking, an angle that is pursued by very few. The core concept of this project is to reveal the 3D quality of the film medium, an aspect often ignored when we are watching a movie, by using digital technologies and computer programming to create pseudo-3D images. The project exhibit will stimulate the audience's visual sense when the filmstrip's 3D aspect is brought to the forefront of its attention, and the audience will understand more about the film medium.
First place awarded to grad students in Student Research
Mechanical Engineering Chancellor Award recipient, Jin Woo Lee, discusses undergraduate research
Through this experience, I have become fascinated with the potential of using micro and nanotechnology to solve the modern day problems to serve people in need and make a lasting impact in their lives. I not only gained new understandings and concepts outside the classroom but also developed more appreciation for the theories and applications that are taught in classes. The summer experience provided me a clear direction to pursue in future research career. Without the Summer Scholars and Artists program, it would have been hard for me to make the choice to continue on to a graduate school and have a clear goal for the future years."