th  - 1988 - 51st ENC Conference

WED 9" 45 IFLUID AND SOLID STATE NMR IMAGING TECHNIQUES FOR STUDY-
ING THE PROCESSING OF ADVANCED CERAMIC COMPONENTS: Jerome L. Ackerman, *~
Leoncio Garrido, ~ William A. Ellingson, b and John D. Weyand; ~ ~Department of Radiology, NMR
Facility, Massachusetts General Hospital, Boston, MA 02114; bMaterials and Components Technol-
ogy Division, Argonne National Laboratory, Argonne, IL 60439; CResearch Laboratory, ALCOA
Technical Center, Alcoa Center, PA 15069
Nuclear magnetic resonance imaging has had major impact on medical diagnosis, but has only
recently been investigated for its potential as an analytical tool in the study of nonbiological ma-
terials. Applying imaging techniques to, for example, a polymeric material offers the possibility of
studying many of the physical and chemical properties normally analyzed with NMR, but now also
in a manner which allows the determination of how these properties vary with position within the
specimen.
We have used both fluid-state and solid-state NMR imaging to study the processing of advanced
ceramic materials. Elevated porosity or nonuniform binder distribution in green-state (unfired)
specimens can lead to flaws in the final densified part, and subsequent failure in service. To image
the porosity of a part, we introduce a carefully chosen tracer fluid into the specimen by vacuum
impregnation. We define the NMR-derived porosity in a region as the fraction of maximum signal
intensity normalized to that of pure tracer fluid. We image the polymeric binders (burned out during
final sintering) of green-state specimens with adaptations of standard 2DFT spin-echo techniques,
with the echo times TE reduced from the typical clinical range of 15 to 100 msec to the range of
600 itsec to 4 msec, in correspondence to the T2's of these materials. We employ image processing
'and display techniques to enhance the understandability of the image data, and to derive measures
of t, niformity such as porosity distribution functions.
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