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Portable furnace provides a better look at microstructures A unique, compact furnace designed and built at the DOE's Ames Laboratory is giving researchers the unprecedented ability to directly record the chemical and structural changes of complex materials at high temperatures under real processing conditions. 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. The device, built by Ames Laboratory's Engineering Services Group, is a scaled-down version of a standard laboratory tube furnace. It measures about 18 inches tall and 6 inches in diameter and is capable of heating samples to 1500 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. Ames Laboratory scientist Matt Kramer, who helped design the furnace, said the new system is an improvement over 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 samples don't always heat 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 furnace is housed at the Advanced Photon Source at DOE's Argonne National Laboratory in a sector of the beam reserved for the Midwest Universities Collaborative Access Team, which is operated by DOE's Ames Lab and Iowa State University. The device has also been used by researchers at DOE's Brookhaven National Laboratory, and the Ames Lab group is currently working on a new furnace design in conjunction with the Synchrotron Radiation Instrumentation Collaborative Access Team at Argonne. Submitted by DOE's Ames Laboratory |
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