Under certain circumstances, decreasing the dimensions of a material may lead to elastic or anelastic properties that diverge from bulk behavior. A distinction is made between elastic deformation, for which bond rearrangements are not required, and anelastic behavior, which involves reversible deformation due to defect motion. Elastic deformation (due to bond stretching) remains structure-insensitive down to near-atomic length scales, and only small deviations are expected (of the order of 10%). More significant deviations can be observed in special cases, which are described in the article. However, elastic moduli that are much lower than expected are sometimes seen, even in careful experiments. It now appears that this behavior may be explainable by time-dependent anelastic relaxation mechanisms. In contrast to purely elastic behavior, anelastic behavior is very sensitive to microstructure and is found to be common and often significant when things become small.
Shefford P. Baker, Guest Editor for this issue of MRS Bulletin, is an assistant professor in the Department of Materials Science and Engineering at Cornell University in Ithaca, N.Y. Baker's work in recent years has focused on the mechanical properties of materials with microscopic dimensions, and techniques to measure those properties. He has also researched modeling relationships between microstructure and mechanical properties. His current research includes measurements and modeling of thermo-mechanical behavior of thin metal films on substrates, adhesion of thin films to substrates, and mechanical-property distributions in materials with complex micro-structures. He received his PhD degree in materials science and engineering at Stanford University while researching the mechanical behavior of metal-metal multilayers. From 1993 to 1998, he was a staff scientist at the Max-Planck-Institute für Metallforschung in Germany. Baker has received an NSF CAREER Award, the Robert Cowie Excellence in Teaching Award, and the Merrill Presidential Scholar Outstanding Educator Award, the latter both from Cornell University. Baker has organized five MRS symposia and has taught MRS tutorials on nano-indentation and mechanical behavior of thin films.
Richard P. Vinci, Guest Editor for this issue of MRS Bulletin, is the Rossin Assistant Professor and Director of the Mechanical Behavior Laboratory in the Department of Materials Science and Engineering at Lehigh University in Bethlehem, Pa. His research involves the processing and properties of thin films and small-scale structures, with an emphasis on the mechanical behavior of metallic materials.
Vinci earned his BS degree in materials science and engineering from the Massachusetts Institute of Technology (1988) and his MS and PhD degrees from Stanford University (1991 and 1994, respectively). He was a postdoctoral scholar and an acting assistant professor at Stanford prior to accepting his current position with Lehigh in 1998. He has received the NSF CAREER Award, the ASM International Bradley Stoughton Award for Young Teachers, the Lehigh University Junior Award for Distinguished Teaching, and Lehigh's Gilbert E. Doan Award. He served as a symposium organizer at the 1999 MRS Fall Meeting and will co-chair an upcoming MRS workshop on materials in microelectro-mechanical systems.
Vinci can be reached by e-mail at firstname.lastname@example.org.
Tomás Arias is an associate professor in the Department of Physics at Cornell University in Ithaca, N.Y. His research interests include mathematics and theoretical condensed-matter physics. He received his BS and PhD degrees in physics from the Massachusetts Institute of Technology in 1986 and 1992, respectively. While studying at MIT, Arias worked as a postdoctoral associate from 1992 to 1993, and prior to that as a research assistant from 1988 to 1992.
Arias can be reached by e-mail at email@example.com.