For release: Dec. 13, 1999
Contacts:
Matt Kramer, Metallurgy and Ceramics, (515) 294-0276
Susan Dieterle, Public Affairs, (515) 294-1405
Shedding new light on advanced materials
Portable furnace designed at Ames Laboratory gives scientists a better
look at microstructures
AMES, Iowa -- A unique, compact furnace combined with high-energy X-rays is giving
researchers at the U.S. Department of Energy's Ames Laboratory the unprecedented ability
to directly record the chemical and structural changes of complex materials at high
temperatures under real processing conditions.
This information is crucial to understanding and controlling the
composition and microstructure of new materials. It previously took months or years to
collect such data through the laborious process of heating, quenching and then analyzing
numerous samples. But the Ames Lab researchers can now gather the data in just a few days
while getting a more detailed picture of what happens to a material's crystal structure as
it heats and cools. The new system is ideal for complex materials such as structural
ceramics, superconducting wires and nanostructured materials. The insights gained
through the Ames Lab system may speed the development of new materials for use in fields
such as aerospace engineering, electrical distribution systems and microelectronics.
"We're seeing details of the phase transitions in the materials that I don't think
anybody has ever described before," said scientist Matt Kramer, who helped design the
new furnace.
The furnace uses an analytical technique known as X-ray diffraction in which an X-ray beam
is focused on a small sample of material. The beam is diffracted by the crystal structure
of each material, producing a unique pattern of concentric circles, called "Debye
rings." By capturing images of the changes in the ring pattern as the material is
heated and cooled, scientists gain a better fundamental understanding of what happens to
the material's crystal structure at various temperatures.
In 1997, Kramer began working with senior metallurgist Bill McCallum, senior physicist and
Iowa State University physics professor Alan Goldman, assistant metallurgist Kevin Dennis
and then-Ames Lab graduate student Larry Margulies on a design for a compact, portable
furnace that would enable them to rotate samples during an experiment. They also wanted to
be able to subject the samples to a variety of environments, such as inert or oxidizing
atmospheres, encountered in processing conditions.
What emerged was a scaled-down version of the standard laboratory tube furnace, measuring
about 18 inches tall and 6 inches in diameter and capable of heating samples to 1500
degrees C (2700 F). The top has an indirect, magnetic coupling system that connects to a
motor shaft, which can rotate the sample holder up to 1,000 times per minute. One end of
the sample holder -- a long pipette that can be capped -- is placed in the coupling system
while the end containing the sample is aligned with a
3-millimeter opening in the side of the furnace. The X-ray beam enters through the opening
and the diffracted rays emerge through a slot in the furnace.
Kramer said the new system is an improvement over current high-temperature X-ray
diffraction systems, in which samples rest on a flat plate. This doesn't allow the sample
to be rotated and sometimes causes the liquid and solid phases of the material to draw
apart. Also, the flat-plate systems don't always heat the sample uniformly, producing
large temperature variations in the material that make it difficult to correlate the
temperatures with changes in the crystal structure.
"The excellent control we have with our furnace means that we can select an exact
temperature setting for our measurement and know that the whole sample is that
temperature," Kramer said. "And with the confined geometry, we can melt things
and know that the liquid and solid aren't separating."
The experiments are conducted at off-site facilities where high-energy X-rays of between
35 and 100 kilovolts are available. Most of the experiments take place at the Advanced
Photon Source at the Energy Department's Argonne National Laboratory near Chicago and the
Cornell High Energy Synchrotron Source in New York. At Argonne's APS facility, the new
home for the furnace will be a sector of the beam reserved for the Midwest Universities
Collaborative Access Team, which is operated by Ames Lab and Iowa State.
Before an experiment begins, the furnace must be aligned with the X-ray beam -- a
painstaking process because the beam itself is about 1 millimeter wide and 0.5 millimeter
high. "That's the hard part," Kramer said. "The first time we did this, it
took us three days to align the furnace to the beam and then another hour or two to align
the sample to the beam itself. But we've gotten the process down well enough now
that it only takes us about a half a day to line it up and minutes to put the sample
in."
The researchers have also found that "shuttering" the beam, rather than using a
continuous ray, enables them to take better sequential images from the diffracted rays.
Kramer said the reactions are monitored with a time resolution of less than two seconds,
fast enough to make a virtual movie of images that capture the material's structural
transformation during temperature-driven processing.
Kramer added that colleagues at Argonne and the European Synchrotron Research Facilities
have asked about having Ames Lab build similar furnaces for them. The furnace used by
Kramer and his colleagues was built by Ames Laboratory's Engineering Services Group.
Ames Laboratory is operated for the Department of Energy by Iowa State University. The Lab
conducts research into various areas of national concern, including energy resources,
high-speed computer design, environmental cleanup and restoration, and the synthesis and
study of new materials.
To view a graphic representation of the furnace, click here.
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Last revision: 12/10/99
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