Award-winning UH professor selected to organize alloys symposium

06/15/05

Simon Moss receives William Hume-Rothery Award for furthering the science of alloys

HOUSTON, June 15, 2005 As the recipient of the 2007 William Hume-Rothery Award from The Minerals, Metals, and Materials Society (TMS) for his leadership and contributions to the science of alloys, a University of Houston professor has now begun organizing the accompanying symposium for the 136th TMS Annual Meeting in 2007.

In addition to being invited to arrange the Hume-Rothery Memorial Symposium held in conjunction with the annual meeting Feb. 25 through March 1, 2007, in Orlando, Fla., Simon C. Moss, M.D. Anderson Distinguished Professor of Physics at UH, will give a keynote address and present a paper.

TMS is an international scientific society whose mission is to promote the global science and engineering professions concerned with minerals, metals and materials. Given annually, the William Hume-Rothery Award was established in 1972 by TMS to honor the memory of the great pioneer in alloy phases William Hume-Rothery, who was an Oxford professor and the leading figure of his time on the physics of alloys.

"It makes me very happy to receive this award, this affirmation from my peers," Moss said. "I am already planning what I would like to talk about and who I would like to invite to present papers around selected topics, both experimental and theoretical. I will definitely talk about Hume-Rothery and how his work has played out in contemporary science and in my own work."

Alloys are metals, such as steel and brass, composed of more than one element, where the resulting material has metallic properties and certain specific desirable characteristics, including strength, formability and corrosion resistance. Their use is ubiquitous, and a fundamental understanding is essential. In the 1960s, three scientific papers published by Moss and his collaborator, Philip C. Clapp, tied together their groundbreaking work on the local structure of (nominally) disordered alloys with regard to the energies of interaction among the atomic species that control the diffuse scattering of X-rays and neutrons that may be retrieved from such measurements.

"There is always a competition in matter between the states in which atoms are either arranged as largely ordered or essentially random," Moss said. "We knew that in alloys, high temperature and disorder go together. The missing link was the ability to assess the energies that determine the structure. This is important because the scattering of X-rays or neutrons from the high-temperature disordered state may be the sole direct method to access these energies that are crucial for alloy formation and stability. Of course, always at high temperature, entropy, or disorder, will eventually prevail over the energy and will disorder the atoms in alloys."

A prominent example that uses only the sharp Bragg peaks and not the distributed diffuse scattering is the local structure of carbon in iron (i.e. steel). From his measurements, Moss was able to determine the very distorted local region around a carbon atom that accounts for the basic strength of carbon steels. Without carbon, iron is nearly as soft as butter. Another very recent example demonstrated that the structure of the UH high-temperature superconductor, YBa2 Cu3 O6.93 (YBCO), is really constituted of very short-range atomic modulations.

Redefining the field of alloy studies, the Clapp-Moss theory became known as Krivoglaz-Clapp-Moss (KCM) Theory named for Clapp, Moss and M.A. Krivoglaz, the great Russian theorist whose earlier work in this area was combined with theirs. The correlation functions in disordered systems via KCM Theory is a topic still continually updated by prominent theorists.

Today, using the scattering techniques noted above, Moss continues to study the atomic structure of alloys in order to understand their phase stability and properties. Currently, he is working with Wolfgang Donner, an assistant professor of physics at UH, on several projects, including one that details the local structure of the very thin oxide film on silicon that turns out to be quite different from the bulk glass and is critical in the designing of computer chips. Donner has followed this thread in his own work, examining the growth of metallic multi-layer thin films in an apparatus he built in his lab that are used in magnetic recording. Moss and his colleagues, including Miguel Castro-Colin, a UH post-doctoral fellow whose dissertation was on this topic, recently published two definitive papers on the, presumably disordered, glass of silicon dioxide. Castro-Colin will take up an associate professorship at the University of Texas at El Paso this fall, where he will continue to pursue this challenging line of research.

Joining UH in 1972, Moss received his bachelor's and master's degrees in metallurgy from the Massachusetts Institute of Technology in 1956 and 1959. He earned his doctorate in metallurgy and materials science from MIT in 1962, in the lab of the pre-eminent MIT physicist, B.E. Warren, working on the scattering from disordered materials. Receiving many honors and awards since, Moss has served on a number of editorial and advisory positions both on professional journals and on panels for the Department of Energy, the National Academy of Sciences and several national neutron scattering centers.

Source: Eurekalert & others

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