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.
Louisiana Tech University, colloquially referred to as Louisiana Tech or La Tech, is a coeducational public research university in Ruston, Louisiana, United States.
Louisiana Tech is designated as a Tier 1 national university by the 2014 U.S. News & World Report college rankings and is the only Tier 1 national university in the nine-member University of Louisiana System. As a designated space grant college, member of the Southeastern Universities Research Association, member of the Association of Public and Land-Grant Universities, and Carnegie Research University with high research activity (RU/H), Louisiana Tech conducts research with ongoing projects funded by agencies such as NASA, the National Institutes of Health, the National Science Foundation, and the Department of Defense.
Louisiana Tech is one of only 35 comprehensive research universities in the nation and the only university in Louisiana to be designated as a National Center of Academic Excellence in Information Assurance Education and Research by the National Security Agency (NSA) and the United States Department of Homeland Security (DHS). The university is known for its engineering and science programs.