| |
Home | Research
| Teaching | People
| Contact | Materials
Science | Chemical Engineering
Research
Program [ Group seminar schedule ]
[ Publications ] [ Facilities ] [SURF 2009]
Projects
Sustainable energy has emerged as the most pressing challenge facing humanity in the 21st century. Fuel cells, because of their high efficiencies and benign emissions, will likely play an important role in a sustainable energy future. In this work we hope to leverage new materials discovery against tailored architectures in order to obtain unprecented fuel cell power outputs.
Solid acids are a fascinating class of materials built upon hydrogen
bonded oxyanion groups. In contrast to polymeric proton conductors,
these compounds conduct protons without the assistance of mobile water
molecules, opening new technological possibilities and scientific
avenues. Our success in fabricating and demonstrating fuel cells based
on these electrolytes has lead to the spin-off company, Superprotonic
Inc.
-
Proton
Conducting Perovskites
Several oxides of the perovskite structure, notably BaCeO3,
BaZrO3, SrCeO3
etc., can, after appropriate doping so as to contain oxygen vacancies,
adsorb significant quantities of water into their bulk structures.
The protons associated with the incorporated water are present in
the form of hydroxyl groups and can easily migrate from one oxygen
ion to the next. This easy migration results in a high conductivity
and materials that are useful for a range of devices, from fuel cells
to hydrolysis cells to hydrogen separation membranes.
- Solid
Oxide Fuel Cells
Solid
oxide fuel cells (SOFCs) operate at high temperatures, and, as a consequence,
they can utilize hydrocarbon fuels, they provide for efficient catalysis,
and they exhaust 'high quality' waste heat that can be used for additional
power generation. High temperature operation, however, has generally
been responsible for the high cost of SOFCs and for their undesirability
for portable applications. Our efforts in solid oxide fuel cells span
a number of activities. These include the use of ceria as an electrolyte
for reduced temperature operation, the incorporation of ceria in fuel
cell anodes for enhanced electrooxidation activity for complex hydrocarbon
fuels, the development of alternative perovskite cathodes for high
activity oxygen electroreduction, and the operation of fuel cells
in so-called single chamber mode for portable power.
- Thermoelectric
Materials and Devices
Thermoelectric materials are useful for converting heat into electricity
(power generation), or, conversely, for extracting heat using electricity
(cooling). Such materials must combine low thermal conductivity,
high electronic conductivity and high Seebeck coefficient, where Seebeck
coefficient is the ratio of the voltage generated across a material
in response to an applied temperature gradient. The strategy
we employ to achieve this somewhat contradictory set of properties
incorporates both semiconductor materials with complex crystal structures
and microstructural manipulation by rapid quenching. For a general
overview of thermoelectrics and some fun demos, visit the JPL
TE page.
- Ferroelectric
Materials and Actuators
(leaving this site)
Over the past several years, ceramic actuators have been developed based
on Pb(Ti,Zr)O3, or PZT, because of
its high piezoelectric coefficients. In this work we use structural
much simpler compounds, BaTiO3 and
PbTiO3 and intermediates, to develop
microactuators. The strategy is to take advantage of the domain
reorientation that occurs in these tetragonal, ferroelectric materials
upon application of an electric or mechanical field. Strains of
1 to 6 % can, in principle, be obtained. The success of this approach
relies on the preparation of highly oriented thin films. Our synthetic
strategy is based on the sol-gel technique of oxide synthesis.
Many silicates are relatively good conductors of alkali ions.
Such materials serve as excellent model systems for study because a
wide variety of crystal structures can be obtained. Moreover,
the structures are typically anisotropic, and thus the impact of subtle
differences in structural features can be probed via measurements along
different directions.
People and Agencies
No post-doctoral
positions are currently open.
- Undergraduate
Opportunities
SURF projects for 2009 - All positions are now filled.
Junior or sophomore Caltech students with prior research experience preferred, and in some cases only Caltech students will be considered. See individual project descriptions for course requirements and recommended prior experience.
In addition to applying through the SURF program, Interested candidates should
send a CV, transcript and at least one letter of recommedation to Prof.
Sossina Haile and the direct laboratory mentor specified in the project description, before requesting further information. Please do not rely on the SURF office to forward this information.
You may
also be able to pursue research in the Haile laboratory via the National Science Foundation
summer research program in solid state and materials chemisitry, run
by the University of Oregon. This program is primarily for non-Caltech students with US citizenship or permanent residency. Please visit
http://ssmchem.uoregon.edu/
to apply. While the Haile group laboratory may not be specifically listed as one of the host laboratories, if you are interested in that program and in one of the projects listed here, it is possible that arrangements can be made.
|