ORNL Materials Programs Highlighted
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Alexander Zucker, ORNL associate director of Physical Sciences.
Bill R. Appleton, director of the Solid State Division.
James O. Stiegler, director of the Metals and Ceramics Division.
PAGE 36, MRS BULLETIN, JULY/AUGUST 1986
three days of talks a re given below. Readers of the BULLETIN who are interested in more detailson particular research projects or who are interested in the user facilities described should contact ORNL directly.
in construction and equipment money allocated to the new High Temperature Materials Laboratory. Many of the fruits of this research investment were described in the technical sessions which followed Zucker's remarks. Sessions were chaired by Bill R. Appleton, director of the Solid State Division, James O. Stiegler, director of the Metals and Ceramics Division, and Vic J. Tennery, directorof the High Temperature Materials Laboratory. A broad spectrum of research topics were covered in areas of both materials processing or synthesis and materials characterization. Unique capabilities at ORNL can be traced to a combination of facilities such as the Surface Modification Center, the High Flux Isotope Reactor, and the National Center for Low Temperature Neutron Irradiation. Summaries of the
Surfaces and Interfaces The session on surfaces and interfaces began with several papers on the use of ion beam and laser techniques for materials processing and analysis. The utility of ion beam and pulsed-laser processing in basic materials research is that these are nonequilibrium processing methods that impose extreme constraints on materials interactions. Consequently, they often lead to new and sometimes unique materials properties or offer new insights into the nature of the nonequilibrium interactions themselves. One such experiment involved the use of subnanosecond pulses from a synchrotron to study undercooling and overheating in silicon that occurs during melting and recrystallization induced by 20 nanosecond laser processing. By synchronizing the firing of a 20 nanosecond pulsed laser with 0.15 nanosecond x-ray pulses from the synchrotron, the temperature of the rapidly moving liquid-solid interface could be monitored through measurements of thermal-expansion-induced-strain. Measurements performed o n < l l l > S i d u r i n g 11 meters/second melting and during 6 meters/second regrowth showed that the interface temperature was 110 K lower during regrowth than during melting and that most of the temperature change was associated with the regrowth phase. Similar m e a s u r e m e n t s utilized timeresolved reflectivity and transmission measurements with nanosecond resolution to study the melting of amorphous Si continued
Vic J. Tennery, director of the High Temperature Materials Laboratory.
induced by rapid pulsed-laser processing. C o m b i n i n g these optical measurements w i t h T E M and ion scattering and comparing to theoretical model calculations permitted the researchers to study explosive crystallization, phase changes, interfacial g r o w t h kinetics, and nucleation and s
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