Material Connections:
This is the first in a series of joint symposia offered by the Department
of Materials Science and Engineering of Northwestern University and the
Materials Science Division of Argonne National Laboratory
Date: March 6, 2001
Time: 1:00pm till 4:30pm
Place: Northwestern University
Building: Technological Institute
2145 Sheridan Road
Rm: Lecture Room 3 (1st floor West Side)
The featured topic of this year's symposium will be:
NANOSCIENCE PROGRAM:
1:10 1:20 Opening Remarks ( Lec Rm 3 Tech)
1:20-1:40 NANO-SCALE COMPOSITION MODULATION IN ULTRATHIN EPITAXIAL ALLOY
FILMS
Mark Asta, Northwestern University.
1:45 2:05 Magnetic Reversal in Thin Film Exchange-Spring Magnets
Sam Jiang, Argonne National Laboratory
2:10 2:30 SINGLE MOLECULE SENSING, CHARACTERIZATION, AND ACTUATION
Mark Hersam, Northwestern University.
2:35 2:50 Coffee Break
2:50 3:10 COMPLEX FLUIDS AS SCAFFOLDING FOR THE FORMATION OF
NANOPARTICLE ARRAYS
M. A. Firestone, Argonne National Laboratory
3:15-3:35 NANOPATTERNED AND NANOSTRUCTURED MATERIALS PREPARED FROM
ARTIFICIAL PROTEINS AND DNA Ilya Koltover, Northwestern University
3:40-4:00 FERROELECTRIC DOMAIN STRUCTURE IN KNbO3 / KTaO3
HETEROSTRUCTURES BY MOLECULAR DYNAMICS SIMULATION Simon R.
Phillpot,
Argonne National Laboratory
Supported by the Office of the Vice President for Research, Northwestern
University.
Abstracts: Material Connections Symposium Tuesday March 6, 2001
NANO-SCALE COMPOSITION MODULATION IN ULTRATHIN EPITAXIAL ALLOY FILMS
Mark Asta, Materials Science and Engineering, Northwestern University.
It is generally recognized that the competition between surface and elastic
strain energy can drive self assembly of nano-scale features in strained
epitaxial thin films. This talk will focus on one particular example of
this type of phenomenon, namely the spontaneous formation of
compositionally modulated structures in very thin (a single to a few
monolayer) films of size-mismatched, bulk-immiscible metals. We will
discuss how first-principles calculations on the atomic scale are being
combined with continuum elasticity theory to model the formation and
thermal stability of these structures.
Magnetic Reversal in Thin Film Exchange-Spring Magnets
J. S. Jiang, S. Bader, Materials Science Division, Argonne National Laboratory
A promising new pathway to achieve permanent magnets with high
energy-products lies in the nano-assembly of existing hard and soft
magnetic materials. The exchange-spring magnets, which are based on
interfacial exchange coupled soft and hard magnetic nano-phases, have the
potential to surpass the current commercially available Nd-Fe-B in
achieving higher energy product. I will describe the synthesis of model
exchange-spring systems using bilayers and superlattices of epitaxial hard
(SmCo) and soft (Fe, Co) magnetic layers, and the characterization of the
magnetic reversal behaviors of both the soft and hard components using a
variety of experimental tools, including magnetometry, magneto-optic and
x-ray magnetic circular dichroism imaging. The results illustrate close
correlations between the magnetic behavior and the microstructure of
exchange spring magnets.
SINGLE MOLECULE SENSING, CHARACTERIZATION, AND ACTUATION"
Mark Hersam, Materials Science and Engineering, Northwestern University.
Chemical, mechanical, and electrical properties of individual molecules
differ significantly from the behavior of bulk materials. In my research
group, we develop nanofabrication techniques that enable spontaneous
self-assembly of single molecules into pre-defined atomic resolution
patterns (see Figure 1). The properties of these surface-mounted molecules
are directly measured and then interfaced to the macroscopic world via
conventional microfabrication. I will discuss our accomplishments in
single molecule electronic and mechanical devices and assess our future
prospects for chemical and biological sensors.
COMPLEX FLUIDS AS SCAFFOLDING FOR THE FORMATION OF NANOPARTICLE ARRAYS.
M. A. Firestone, Materials Science Division, Argonne National Laboratory
Complex fluids are non-covalent aggregates characterized by both a high
degree of anisotropy and segregated hydrophilic and hydrophobic domains
organized on the nanometer length scale. Recently, we have demonstrated
facile introduction and spatial compartmentalization of inorganic
nanoparticles in the lamellar gel phase of a polymer-grafted, lipid-based
complex fluid. Specifically, by controlling the size and surface chemistry
of silver nanoparticles, site-directed localization of the particles into
one of the three physicochemically distinct regions of the lamellar gel
phase of the complex fluid has been achieved. Most significantly, we have
also found that by adjustment of the complex fluid composition (i.e.,
increasing the length of the appended polymer), the interactions of the
encapsulated nanoparticles and therefore, their optical and electronic
properties, can be "fine-tuned". Complex fluids have thus been shown to
serve not only as passive scaffolding for the organization of inorganic
nanoparticles, but also as potential "active" host media for modulating the
optical and electronic properties of encapsulated guest species.
NANOPATTERNED AND NANOSTRUCTURED MATERIALS PREPARED FROM ARTIFICIAL
PROTEINS AND DNA
Ilya Koltover, Materials Science and Engineering, Northwestern University.
Artificial proteins and DNA represent a new class of macromolecular
materials that bridge the gap that has traditionally separated natural
polymers from their synthetic counterparts. While synthetic polymers are
interesting and enormously important, their utility derives in large part
from their physical properties; chemists have yet to capture in synthetic
polymers the more subtle catalytic, informational, and transduction
properties of proteins and nucleic acids. The reason for this distinction
may lie in the levels of architectural control to be found in each class of
polymers; proteins and nucleic acids are characterized by defined lengths,
sequences, and stereochemistries, while synthetic polymers are highly
heterogeneous molecular mixtures. This raises interesting questions
regarding the kinds of materials science that could be done if new
macromolecular architectures could be created with precise control of the
most important structural variables. Microbial expressions of artificial
genes provides a means of doing just that. In our laboratory, the process
begins with molecular design - the specification of a chain structure that
we believe will exhibit interesting (and perhaps useful) behavior. The
target structure is then encoded into an artificial gene, and the gene is
expressed in an appropriate microbial host. I will describe two targets
under present and future investigation in our laboratory: novel liquid
crystal phases and macromolecular surface arrays with nanometer-scale
features prepared from rigid-rod protein polymers; and nanometer-scale
wires and networks templated on DNA and membrane assemblies.
FERROELECTRIC DOMAIN STRUCTURE IN KNbO3/KTaO3 HETEROSTRUCTURES BY MOLECULAR
DYNAMICS SIMULATION*
M. Sepliarsky1,2, Simon R. Phillpot1, D. Wolf1, M. G. Stachiotti2 and R. L.
Migoni2
1 Materials Science Division Argonne National Laboratory
2Instituto de Fisica Rosario, CONICET UNR, Rosario, ARGENTINA
We have developed an atomic-level approach to the simulation of the
ferroelectric perovskite KNbO3 (KNO) based on the traditional Buckingham
potential with shell model which correctly reproduces the ferroelectric
phase behavior and dielectric and piezoelectric properties. Using this and
a compatible interatomic potential for the incipient ferroelectric KTaO3
(KTO), we have determined the structure and ferroelectric properties of
coherent KNO/KTO heterostructures of varying layer thicknesses; such
heterostructures have important opto-electronic applications. We find that
there is a strong coupling of the polarizations parallel to the modulation
direction of the KNO and KTO layers, but that the in-plane polarizations
are only rather weakly coupled between layers. Moreover, we find that the
differing strain states produced respectively by growth on a KNO substrate
and on a KTO substrate result in qualitatively different calculated
ferroelectric behavior in the heterostructures.
--------------------
check out <www.tech.nwu.edu/~indrel/home.html> !
Allison H. Berger
Office of Industry Relations
Northwestern University
2145 Sheridan Road
Tel: (847) 491-3365
Fax: (847) 467-3033
Email: [EMAIL PROTECTED]
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