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Starting in NPRE at Illinois this fall as an assistant professor, material physicist Yang Zhang adds expertise to the department's strong materials group.
“We are extremely fortunate to have attracted these new faculty members who will vastly strengthen and broaden our research and teaching missions,” said NPRE Department Head Jim Stubbins. “Our plans are to grow the faculty even more in the near future.”
The principle focus of Zhang’s research is to understand the physics of disordered materials through integrated microscopic experimental probes and predictive computational modeling.
“The structure and dynamics of these materials are either inherently complex or driven far from equilibrium by extreme conditions – rapid change of temperature or pressure, intense irradiation, high mechanical load, and so on,” Zhang said. “Because of the harsh nurturing conditions, there is a hope for these disordered materials to survive under extreme environments.”
“Examples include some of the most popular and promising engineering materials: amorphous and high-entropy alloys, liquids and glasses, cement and asphalt concrete, and innumerable bio and soft materials,” he continued. “Such studies will shed light on a class of fundamental and technical problems involving phenomena emerged from rare events, frustrations and ergodicity breaking, and lead to countless pivotal applications in nuclear systems.”
Zhang points to his graduate work at the Massachusetts Institute of Technology and his continuation work at Oak Ridge National Laboratory (ORNL) as among his best achievements to date. His experiments using neutron scattering showed that water supercooled below its normal freezing point – at about minus 60 degrees Celsius and more than 2,000 bars – can transform from one liquid phase to another liquid phase with very different densities.
A homemade experiment of metastable supercooled water. However, the lower the temperature, the more difficult to avoid the freezing. Using the simple method demonstrated in this video, bulk water cannot be supercooled below the so-called homogenous nucleation temperature at around -38C. Zhang and his collaborators have gone beyond this limit by loading water into nanopores, and achieved deeply supercooled water.
He was able to do this by using nanometer-sized tubes of silica, in which the molecules of water were tightly confined so that they were unable to crystallize into ice. The tight confinement made it possible to maintain water in liquid form far below its normal freezing point. Zhang probed the density of the supercooled water molecules using a neutron beam from a reactor at the National Institute of Standards and Technology, and found a difference in water’s density by approaching the expected transition temperature from opposite directions, proving previous theories.
Zhang comes to Illinois from the Spallation Neutron Source at ORNL, where he was named the Clifford G. Shull Fellow in 2010. At the national lab, he investigated the physics of liquids, glasses, and soft condensed matters using both neutron scattering techniques and computer modeling and simulation.
He earned a PhD in nuclear science and engineering from MIT in 2010 and a bachelor’s degree in electrical science and technology from the University of Science and Technology of China in 2004.
Zhang has more than 20 publications, including book sections and peer-reviewed articles in high impact journals.
He envisions that he will be collaborating with NPRE Profs. Jim Stubbins and Brent Heuser, as well as research groups in several other departments and labs in the College of Engineering and across campus. “I look forward to in-depth collaborations with the research groups at Illinois. With the collective effort, we may be able to make a huge impact in the understanding of materials performance under extreme environments,” Zhang said.