This is a comprehensive interdisciplinary program of basic research on displacive transformations in ceramics. The ultimate aim is to raise the level of understanding of these transformations to that comparable with martensitic transformations in metallic systems. The program involves studies concerning precursor phenomena and phonon effects, elasticity properties, transformation crystallography, static displacements, chemical and structure ordering, and kinetics. Systems currently being studied are KNbO;i3, PbTiO;i3, and BaT:O;i3, as well as relaxor ferroelectrics PMN, PST, and PLZT.

The Materials Research Laboratory is engaged in a collaborative effort with personnel from the Oak Ridge National Laboratory, National Institute of Standards and Technology, and UOP Research Inc. for the development of two beam lines of the Advanced Photon Source (APS) being constructed at the Argonne National Laboratory. The foci of this effort are to do research and to educate new generations of scientists and engineers at the cutting edge of the science and engineering in various disciplines. Particular efforts presently underway and planned are in surface/interface diffraction, magnetic scattering, inelastic scattering, MÖssbauer effect, diffuse scattering, and macromolecular crystallography. H. Chen is the director of this APS beam-line development project.

The principal means by which Ni-based superalloys strengthen themselves is precipitation hardening. Recent years have seen a renewed interest in the phenomena of Ostwald ripening. The classical theory has recently been modified to incorporate the effect of finite volume fraction and the coherency stresses due to lattice mismatch. These factors can have profound effect on the precipitates growth kinetics and their final size distribution. There is an acute need for experimental verification, which is the principal goal of this research. We have found for the first time enhanced coarsening rate due to lattice misfit strain via small-angle neutron scattering measurements. Further study is being conducted using TEM to confirm the scattering results.

Anomalous x-ray scattering studies of a lead-magnesium-biobate (PMN) single crystal were carried out to study its superstructure. Ordering was observed by the presence of 1/2(111) type superlattice peaks. By tuning the energy of the synchrotron radiation to values close to the Pb L _III absorption edge, the superstructure was shown to include Pb, either by atomic exchange or large displacements. Recent synchrotron x-ray data show the Bragg peak intensities changed not only with temperature but also with aging time. Further work is needed to separate these two effects and to understand the ordering-temperature relationship.

Zeolites find wide applications in petrochemical industries owing to their unique properties, such as absorbents, catalysts, and ion exchangers. Many studies have concentrated on the synthesis of new zeolite types and possible applications for zeolites. The underlying molecular events which govern crystallization are still poorly understood. With the brilliant synchrotron radiation source at APS available as well as state-of-the-art position-sensitive detectors, it becomes possible to carry out the in situ studies using SAXS and WAXS techniques to monitor the whole process of zeolite crystallization, with the precursor gel transformation monitored by SAXS and crystallization by WAXS simultaneously.