Mechanical
and Materials Engineering
David Bahr
Nanomaterials: Bridge Between Atomic
and Macroscopic
There
is significant evidence that the mechanical properties
of nanostructured materials differ significantly from
their bulk counterparts. Dr. David Bahr and his colleagues
in the School of Mechanical and Materials Engineering
and the Center for Materials Research have developed
the capabilities to measure the properties of these very
fine structures and then carry out the basic research
required to link the processing which created that structure
to the subsequent properties. By tying together characterization
tools such as electron microscopy and diffraction, atomic
force microscopy, and nanoindentation, they have been
able to explain the mechanical response of materials
in which classic methods of deformation break down. By
studying the deformation and fracture on these small
scales, they have been able to demonstrate that halide
ions in acidic solutions can weaken the fracture strength
of a 2-5 nm thick oxide film protecting titanium or stainless
steel.
Coupling
these nanoscale measurements with bulk stress corrosion
cracking tests shows how the strength of protective
layers only 20 atoms thick can control the fracture
of large engineering structures. Another example
of this type of bridging length scales includes
research in the area of thin film adhesion, where
layers of titanium only 15 nm thick are used to
promote the adhesion of vapor deposited platinum
films required for use in a MEMS heat engine.
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 |
This
engine, developed by Drs. Robert Richards, Cill Richards,
and Bahr, produced the first demonstration of electrical
power using a MEMS heat engine, and has been funded by
National Science Foundation, Defense Advanced Research
Projects Agency, and the Army Space and Missle Defense
Command for use as an alternative to batteries.
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Students
working on this project have demonstrated that the
use of a 15 nm adhesion layer between two mm thick
films can quadruple the adhesion of these materials.
In all these areas, faculty, graduate students, and
undergraduate research assistants are striving to
relate the nanoscale structures to the bulk performance
of the materials, and bring nanoengineering from
the bench top to practical applications in society. |
Contact
Information
David Bahr, Ph.D.
Associate Professor
School
of Mechanical and Materials Engineering
Washington State University
PO Box 642920
Pullman, WA 99164-2920
Telephone:
509-335-8523
E-mail: dbahr@wsu.edu
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David Bahr
