Dr. Kasra
Momeni, assistant professor of mechanical engineering and director of the
Advanced Hierarchical Materials by Design Lab at Louisiana Tech University, has
discovered a new mechanism for strengthening nanomaterials and tailoring their
properties to build superior structures.
Momeni, in
collaboration with researchers from Wright State University and the University
of Göttingen in Germany, have revealed a new path for engineering nanomaterials
and tailoring their characteristics. This additional dimension added to the
material design opens new doors to build superior materials by engineering
their atomic structure. The proposed approach can also be used to adjust the
chemistry of the material, which is of importance for designing new catalytic
materials enhancing the chemical processes.
"Stacking
faults in nanomaterials drastically change the stress distribution, as the
long-range stress fields interact with the boundaries in these materials,"
said Momeni. "The complex nature of the stresses formed in nanowires, as a
result of superposition of the stress fields from surface relaxation and
reconstruction as well as the stacking fault stress fields, changes the failure
mechanism of the nanowires."
Atomistic
simulations indicate that the presence of stacking faults results in an
inhomogeneous stress distribution within the nanowires due to the change in the
sign of stress fields on the two sides of stacking faults (i.e. compressive
stress on one side and tensile stress on the other side). This inhomogeneous
stress field results in a nonsymmetrical mechanical response of the nanowires
under tensile and compressive loadings. The defected nanowires with diameters
smaller than 1.8nm and a single stacking fault, surprisingly, have higher a
yield stress compared to their counterparts with perfect structures.
"This
surprising behavior is due to the interaction between the stress fields of
stacking faults with the stress field of relaxed and reconstructed surfaces in
thin nanowires," Momeni said. "We expect similar results in other 1D
nanomaterials with stacking faults, where inhomogeneous stresses form. The
developed atomistic model paves the way to study the effect of different
stacking fault distributions and engineering defects to tailor material
properties."
"Dr. Momeni
arrived at Louisiana Tech this past August and has hit the ground
running," said Dr. David Hall, director of civil engineering, construction
engineering technology and mechanical engineering at Louisiana Tech. "His
discovery of a method to strengthen materials through the interaction of
atomic-level material features is a significant and fundamental contribution in
computational mechanics.
"Dr. Momeni
is at the cutting edge of a new research area that uses supercomputing to
understand and design new materials, and we are thrilled to have him on our
faculty."
Source:
