Ice’s dream
Gene Ice’s award-winning X-ray mirrors enhance how we see modern materials
It began as a dream, received early support as a seed money project, and very well could revolutionize X-ray analysis of materials. An R&D 100 award may just be the beginning for ORNL’s new X-ray diffraction microscopy technique. |
| Kelsey Ice poses with two X-ray diffraction mirrors made of ultra-low-expansion glass that her dad, M&C Division's Gene Ice, developed. |
“This project gives us a totally new approach to our understanding of the properties of materials,” says the Metals and Ceramics Division’s Gene Ice. “It gives us a way to use powerful new X-ray sources such as the Advanced Photon Source to see inside materials in a way we’ve never been able to until now.”
Gene says the X-ray crystallography technique will offer researchers an unprecedented, three-dimensional view into the structure of polycrystalline materials, which he says includes just about every material except silicon. A media release from earlier this year gives the example of the integrated circuits in your personal computer’s microprocessor. When it goes on the blink, the cause is likely a breakdown in one or some of the countless tiny metal wires that establish connectivity within the chip’s silicon base.
When those connections are disrupted—through metal fatigue or some other types of stresses—you get that awful sinking feeling as your PC fails to boot up. That’s just one instance where enhancing the ability to analyze the grain structures of polycrystalline materials, such as the little metal wires, can give us more insight into making better materials.
“Those fine wires that connect the integrated circuits’ elements together represent a quality-control challenge to manufacturers and users,” Gene notes. “As IC chips become more dense, with finer wires layered closer together, the potential for failures increases as well.”
In fact, as materials become more advanced, industries will need more advanced ways of looking into them, at a submicron scale between the atomic level and the microscopic level—at a scale of tens of microns, or the “mesoscale.”
Gene’s pursuit of 3-D mesoscale X-ray diffraction images of polycrystalline grains began in the early 1980s. He received an IR 100 award (the R&D 100’s forerunner) in 1983 for an optical device he helped develop with fellow researcher Cullie Sparks for focusing X-rays at Brookhaven National Laboratory.
“The Dynamically Bent Sagittal Focusing Monochromator is a powerful technology that’s now used all over the world,” he says. “During a five-year off-site assignment to run Oak Ridge’s first X-ray synchrotron beamline, I became convinced that microdiffraction was the next step in materials characterization. I pushed for it. I received seed money funding in 1993 and went around the country talking to industries and other labs about their needs for such an instrument.”
In the meantime, Solid State Division’s Jim Roberto and Ben Larson became interested in partnering.
“Jim was looking at new directions in materials science, and there weren’t any tools for analyzing materials at the mesoscale,” says Gene. “Ben recognized how important the
X-ray microprobe would be and added the considerable expertise of his solid-state X-ray group to the project.”
With a larger LDRD grant to prove the principle, Gene and Ben revived the oldest technique for X-ray microscopy, called the Laue method. Laue diffraction uses a beam with many wavelengths. As Gene explains, using one wavelength on highly disordered materials drastically reduces the chances of obtaining information from each grain as the X-ray beam “scatters” off of structures. A polychromatic technique increases the information 10,000 times. It also, however, increases manyfold the complexity of the data.
In addition to the development of the R&D 100 Award-winning microfocusing mirrors, which are fabricated using thin-film deposition techniques championed by ORNL, Gene and Ben needed a new kind of X-ray monochromator that could either select a single wavelength or pass a polychromate beam. They also needed sophisticated computer codes to crunch the volumes of data.
M&C and Solid State, with Ben Larson leveraging his considerable reputation as an expert, entered into a collaboration with professor Walter Lowe at Howard University in Washington, D.C., to design and build a monochromator to select wavelengths from the polychromatic diffraction imaging. “It’s the first major scientific instrument that was built at Howard,” Gene says, “and it’s a fantastic instrument.”
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| Gene Ice |
Gene and Ben have also partnered with Solid State’s John Budai to analyze the RABiTS superconducting film developed by ORNL’s Superconductivity program, assessing how the structure in the underlying layers affect the grain structure, and thus the performance, of the deposited layers. The process can be applied to many materials—metal and ceramic—used for chips, gears, car bodies or even bridges.
Gene is also working on a proposal to apply the technique to groundwater-flow research. By studying the crystalline structures of radioactive and heavy-metal contaminated metals, much can be learned about how they are transported in groundwater.
“We can now look deep into a sample,” Gene says. “There have been many theories on how grains affect the performance of thin films, or how the wires in ICs evolve toward failure. Internal stresses are the forces, and up until now they have been totally invisible.”
Gene lists three innovations from the long-running project: the microfocusing mirrors that focus the X-ray beams, which won the R&D 100 Award; the monochromator that Howard University built, installed at Argonne’s Advanced Photon Source; and the automatic indexing software that separates the complicated Laue patterns, allowing them to characterize the grains.
“We would like to involve ORNL’s computational groups in adapting that software to massively parallel processing,” Gene says. “The data from the microscope are so complex that it takes days to interpret an experiment. Applying the codes to a supercomputer would allow us to make the analysis in real time!”
Researchers can finally determine what’s happening to specific grains in a material instead of averaging the results. “It’s a far more direct—and accurate—approach,” he says.
“People have been studying materials with X-rays for a long time,” Gene states. “We’ve brought back one of the oldest techniques—Laue diffraction—and applied innovative approaches and new technologies.
“In fact, this project has involved some of the best aspects of a national lab—interdivisional collaborations between M&C, Solid State and eventually the parallel computing groups; partnering with a university, particularly a historically black university; and the use of seed money and LDRD funding to nurture a visionary concept.”
Says Gene, “This project has put together the very strengths of this Laboratory. By being the first to develop this new technology, ORNL has the potential to make significant progress in a number of fields that touch on many divisions within ORNL.”—B.C.
