Scientia | Giving Vulcan His Hammer

Giving Vulcan His Hammer

By BILL DOCKERY

Tennessee's international leadership grows with work on a neutron beam line devoted to materials research

In classical mythology, Vulcan was the deity of fire and the forge. In the heat and soot of his smithy under volcanic Mount Etna, he beat metals into arms and armor for his fellow Roman divines.

Scientists connected to the Spallation Neutron Source have reached into that culture of myth and magic to give a name to one major SNS component. The experimental station on a beam line devoted to analyzing the mechanical behavior of metals and alloys is named Vulcan, in homage to the blacksmith to the gods. But the product of this 21st-century "forge" won't be swords and body armor; it will be knowledge about new metals and alloys—stronger, more sophisticated, and safer for building increasingly more complex structures.

A team of University of Tennessee materials scientists and their partners at Oak Ridge National Laboratory have been given the job of outfitting Vulcan with the tools that will turn it into the premier facility in the world for studying metallic structure and properties. Peter Liaw and Hahn Choo from UT and Xun-Li Wang and Camden Hubbard from ORNL are the principal investigators on a National Science Foundation award that is supporting the instrumentation. (The late Raymond Buchanan, who died in January 2006, was also a principal investigator in this program.) "Our main focus will be making heavy use of neutrons to probe and understand the microstructure and mechanical behavior of structural metals and alloys," said Hahn Choo, a faculty member in UT's Materials Science and Engineering Department and a Joint Faculty in ORNL's Materials Science and Technology Division.

Scattered Neutrons

At the center of the research station is the Vulcan diffractometer, a large-scale engineering instrument that will aim a beam of neutrons at structural materials under study. The way the neutrons scatter or bounce off a sample of a material can reveal how atoms in the metal or alloy sample are arranged.

"Our team is developing instruments that will allow for in situ and real-time characterization of metals," said Choo, a co-director of the $2.9-million instrumentation project. Hahn and colleagues are designing a load frame for mechanical testing at high temperatures, a vacuum furnace that will reach 1,500° C (2732° F) under load, and an electrochemical cell for observing aqueous corrosion and electrochemical charging. The equipment will allow observations to take place while the material is being stressed rather than after the stresses have eased, simulating realistic processing or service conditions.

Elite Cadre

Giving Vulcan His Hammer Choo came to UT from postdoctoral studies at Los Alamos Neutron Science Center, another of the notable neutron-scattering facilities in the world. Many researchers from the materials science community are advising on the creation and instrumentation of Vulcan, he said. "The researchers in the community interact very closely. Everyone knows everyone." Nonetheless, the university's participation in the instrumentation project has had a positive impact on UT's standing as a center for research in structural materials and metallurgy.

"We're becoming one of the major players in this field in just two or three years," Hahn said. "More and more, we're playing to our strengths; and we're seeing other scientists and postdocs and students coming our way in other research fields as well."

Besides Choo and Peter Liaw, holder of the Racheff Chair of Excellence at UT, UT has attracted Takeshi Egami, a UT–ORNL Distinguished Scientist who has pioneered atomic pair-density function as a way of looking at the localized atomic structure of crystalline materials. His research makes extensive use of both neutron- and electron-scattering techniques, as well as X-ray diffraction. And T. G. Nieh, a specialist in bulk metallic glasses and nanocrystalline alloys, recently joined the UT materials science department.

UT's Prominence

The university's work on Vulcan dovetails neatly with another project NSF chose UT to implement. Early in 2003, UT was one of only three universities in the nation chosen to establish International Materials Institutes for NSF. The IMI program at Princeton focused on collaborations between U.S. and African scientists, the program at Rensselaer Polytechnic Institute (now at Iowa State University) was devoted to combinatorial sciences and materials informatics, and the program at Tennessee sought to foster an international network of researchers and educators in neutron-scattering materials research with a specific emphasis on studies of mechanical behaviors.

UT's 5-year $4.7-million IMI program is called ANSWER (Advanced Neutron Scattering netWork for Education and Research) and has linked six neutron-scattering facilities in North America, three in Europe, and five in Asia and the Pacific. ANSWER is headed by the same team of UT and ORNL scientists that is developing instrumentation for Vulcan. Like the team's work on Vulcan, the institute promotes in situ real-time studies of the mechanical behavior of materials, as well as modeling research.

The ANSWER program has also given the institute a platform for holding tutorials, a "neutron school," and other workshops and conferences that have put U.S. students in international settings and brought international students to U.S. research venues. "ANSWER is facilitating the development of a world-class workforce in neutron science," Choo said. "It is providing U.S. students and researchers access to research programs around the world."

For more information, contact Hahn Choo, (865) 974-3643, or e-mail hchoo@utk.edu.