OAK RIDGE, Tenn., Oct. 2, 2002 - From soft drink cans to bones, virtually all materials are made up of heterogeneous - or dissimilar - microstructures, and researchers at Oak Ridge National Laboratory have developed a tool to better study those structures.
The work of ORNL's Gene Ice and Ben Larson has attracted interest from NASA; the auto, semiconductor and electronics industries; and the world of academia because it fills a gap that has hindered progress in studying new materials. Their technique enables them to study the heterogeneous structure of materials in great detail and in three dimensions, and it paves the path for the development of new materials.
"Although people have gotten pretty good at developing new materials with trial and error, information that this technology will provide will reduce reliance on that technique," said Larson, a senior researcher in the lab's Solid State Division and the developer of a novel technique that allows for the 3D capability. "This will allow scientists to look at materials between 1/10th of a micron to hundreds of microns - the so-called mesoscale."
A micron is equal to one-millionth of a meter. It is at this scale that the Department of Energy wanted ORNL to investigate, and just two years ago Ice received an R&D 100 Award for his differentially deposited X-ray micro-focusing mirrors. Ice's invention allows scientists to study internal interactions in materials made up of small disoriented crystal blocks called grains.
Larson's technique uses a knife-edge profiler as a moving pinhole camera to make measurements with a charge coupled device area detector. The approach builds on Ice's accomplishments by making it possible to probe the interior of bulk materials to obtain "depth-resolved" structural information.
The instrument allows researchers to examine and measure structure, orientation, morphology, stress and strain, all without destroying the sample. Researchers can perform these studies with micron resolution in single crystal, polycrystalline materials, composites, multi-layers and deformed materials in the mesoscale range.
The work was published earlier this year in a Letter to Nature (Nature 415, 887).
In the past, researchers could either study isolated single crystals or they could study the average properties of many polycrystalline grains. Neither approach provides an entirely accurate picture at the scale required to understand the behavior of polycrystalline materials. The ORNL instrument provides sub-micron resolution and three-dimensional information over hundreds of microns, which is exactly what is needed to study changes in microstructure and develop materials.
During the last two years, Larson and Ice have been working toward making their measurement technique available to industry and the scientific community. They believe their differential-aperture X-ray microscopy represents a breakthrough that will revolutionize micro-structural study of materials.
"With this new capability, previously missing information is available for comparison with computer modeling to guide the development of materials," said Ice, a researcher in ORNL's Metals & Ceramics Division. "I think we can expect this technique to contribute to the development of materials for computers, automobiles, medical equipment and superconductors."
Larson and Ice conduct their experiments at the Advanced Photon Source at Argonne National Laboratory. Collaborators include Wenge Yang, John Budai and Jon Tischler of ORNL and researchers at Howard University in Washington, D.C., and the University of Illiniois.
Funding for this research is provided by DOE, which also provided initial funding through ORNL's seed money and Laboratory Directed Research and Development programs. ORNL is a DOE multiprogram research facility managed by UT-Battelle.
Materials provided by Oak Ridge National Laboratory. Note: Content may be edited for style and length.
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