John Cahn, an emeritus senior fellow and materials scientist at the U.S. Commerce Department's National Institute of Standards and Technology (NIST), has been named to receive the prestigious Kyoto Prize in Advanced Technology. Cahn's numerous major contributions to materials science include developing a fundamental theory that describes the behavior of mixtures of different materials and how they tend to separate at the microscale. The theory established an entire branch of materials research and is particularly important to the rational design of new alloys.
Awarded annually since 1985 by the nonprofit Inamori Foundation, the Kyoto Prize is Japan's highest private award for global achievement and honors significant contributions to the betterment of society. The focus of this year's award for advanced technology is materials science and engineering. The prize includes a diploma, the Kyoto Prize medal and a cash gift totaling 50 million yen (~$625,000), awarded during a week of ceremonies beginning Nov. 9, 2011, in Kyoto, Japan.
"John's developments in the theory and models of materials have given scientists tools to understand and make new materials ranging from metals to plastics to ceramics and glass," said NIST metallurgist Frank Gayle. "For instance, your smart phone or laptop computer might contain 100 different materials, and John's work has probably influenced the understanding and development of half of those."
Practically all metals in use today are alloys, mixtures of two or more pure metals that, combined, have superior properties to either alone. Alloys are not always uniform, homogeneous mixtures. At the microscopic scale in some alloys, the different elements tend spontaneously to separate slightly in twisty, random clumps, a phenomenon called "phase separation." Unlike crystallization, in which one component of a solution separates out to solidify at discrete starting points (think of making rock candy), this separation happens simultaneously throughout the mixture.
The phase separation and related changes in microstructure play a key role in determining the physical engineering properties of the bulk composite alloy—things like strength, toughness, ductility, magnetic strength and thermal conductance—but before the work of Cahn and his collaborator John Hilliard, then at General Electric, there was no good mathematical description of how this separation occurred. Developing a new alloy to meet specific material requirements was a painfully long and expensive process of trial and error.
The Cahn-Hilliard equation supplied that basic framework. The equation describes, quantitatively, how the components of a binary mixture that becomes unstable when cooled will separate. Cahn proceeded to elaborate the theory, showing how basic thermodynamic principles could be used to design alloys that would form desired microstructures. His work laid the foundation for the rational design and manufacture of new materials based on the Cahn-Hilliard equation.
Like many other fundamental theories, the work has proven relevant to a broad range of seemingly disparate fields. The Cahn-Hilliard equation, among other things, describes how galaxies began forming out of the primal material of the Big Bang in the early stages of the universe.
For more information, see the NIST June 24, 2011, news announcement at www.nist.gov/public_affairs/releases/kyoto-prize-062411.cfm.