Brent Fultz received his Ph.D. from U. C. Berkeley in 1982. He was a Presidential Young Investigator; he also received an IBM Faculty Development Award and a Jacob Wallenberg Scholarship. He has consulted for the electronics testing company, Everett Charles Technologies, and the Defense Science Board. Fultz authored or co-authored well over 150 refereed publications, edited four books, and with J. Howe is completing a graduate-level textbook on diffraction and microscopy of materials. Fultz's description of his research interests is:
1. The main thrust of my work from 1987-92 was to use modern ideas in kinetics to understand atom movements in crystalline alloys. There were three accomplishments:
2. By calorimetry experiments we showed that vibrational entropy
is important for the thermodynamics of alloy phase stability.
Vibrational entropy is new to the materials science community,
and its importance was unexpected. We have begun to measure
phonon spectra of materials by inelastic neutron scattering.
From phonon spectra we learning why there are
differences in vibrational entropy between different alloy phases.
This work is performed at national laboratory facilities for
neutron beam experiments such as the reactor at Oak Ridge (HFIR)
and the spallation sources at Argonne (IPNS) and Los Alamos (LANSCE).
For many other types of materials, we are trying to determine how
differences in crystal structure or microstructure affect the
vibrational entropy.
L. J. Nagel, B. Fultz, and J. L. Robertson, "Vibrational Entropies of
Phases of Co3V Measured by Inelastic Neutron Scattering and Cryogenic
Calorimetry", Philos. Mag. B 75 (1997) 681-699.
L. J. Nagel, B. Fultz, J. L. Robertson, and S. Spooner, "Vibrational
entropy and microstructural effects on the thermodynamics of
partially-disordered and ordered Ni3V", Phys. Rev. B, 55 (1997) 2903-2911.
3. We are pursuing two new Mossbauer-type experiments.
They are:
i) diffraction from 57Fe atoms in specific chemical environments, and
ii) inelastic scattering to measure the vibrational spectra of 57Fe atoms.
Mossbauer diffraction is an unexplored technique that has a capability
of combining spectroscopy with diffraction in ways not avialable to
the three diffraction methods of x-ray, electron, and neutron
diffraction. It can provide information to permit new studies on
topic 1 above. The inelastic scattering methods are performed at
the Advanced Photon Source at Argonne National Laboratory, and provide
information useful for topics 2 and 4.
i.) T. A. Stephens and B. Fultz, "Chemical environment selectivity
in Mossbauer diffraction from 57Fe3Al", Phys. Rev. Lett. 78 (1997) p. 366-369.
ii.) B. Fultz, C. C. Ahn, E. E. Alp, W. Sturhahn, T. S. Toellner,
"Phonons in nanocrystalline 57Fe", Phys. Rev. Lett., in press.
4. We began our work on nanocrystalline materials by determining
the widths of their grain boundaries. We later tested two metallurgical
design strategies for stabilizing nanocrystalline materials against
growth of their crystallites. In a related problem, we have shown
both by experiment and by Monte Carlo simulations that two-phase
steady-states in driven alloys are caused by heterogeneities in the
enthalpy density. Recently we have been measuring the vibrational
spectrum of nanocrystalline materials, which are significantly different
from materials having conventional crystallites. We are also studying
the interaction of microwave radiation with nanocrystals.
H. N. Frase, L. J. Nagel, J. L. Robertson, and B. Fultz,
"Vibrational Density of States in Nanocrystalline Ni3Fe", Philos.
Mag. B 75 (1997) 335.
5. We have been studying electrochemical properties of metal hydrides
for several years. This is a response to a technological need to
improve the lifetime of nickel - metal hydride batteries.
The work includes an alloy design philosophy based on the kinetic
control of atom movements, for which some concepts of topic 1 above
are useful. We have begun to develop lithium alloys for electrodes
in rechargeable batteries.
C. Witham, B. V. Ratnakumar, R. C. Bowman, Jr., A. Hightower,
and B. Fultz, "Electrochemical Evaluation of LaNi5-xGex Metal Hydride Alloys",
J. Electrochem. Soc., 143 (1996) L205-L208.
6. We have just begun to study Tb-Dy alloys with giant magnetostriction (these materials change their length by about 1% in a modest magnetic field). Our intent is to design polycrystalline materials that exhibit much of the performance of single crystals.