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MEAM Seminar: “Effect of Nanoparticle Size on the Mechanical Properties of Nanoparticle (NP) Assemblies”
June 26, 2019 at 3:30 PM - 5:00 PM
Nanoparticle assemblies (NPAs) have attracted tremendous interests of various research communities. The particle-size-effect on mechanical properties of NPAs is systematically studied. With decreasing the particle size d from 300 nm to 10 nm, the SiO2 NPAs become drastically harder (∼39×), stiffer (∼15×), and tougher (>3.5×). The results are consistent with the data scattered in the literature for various nanoparticle (NP) systems, indicating a fundamentally universal d-effect for all NPAs. A model is developed to correlate the hardness and the NP junction (NPJ) strength f. Here, f is mainly due to van der Waals and capillary interactions, roughly a constant (140 nN) for d = 100–300 nm, and then f decreases with decreasing d from ∼100 nm. The deformation mechanism of NPAs (for indentation depth ≫d) is shear plasticity involving shear breaking of NPJs. The fundamental mechanism for the d-effect is that, with decreasing d, the NPJ’s planar density increases much faster than the decrease of f. Moreover, three deformation mechanisms of NPAs, (1) nanoparticle dislodging, (2) shear-band formation, and (3) cracking are naturally d-dependent. These new findings can provide important insights into the fundamental understanding of the inter-NP interaction, the mechanical behavior of the NPAs, and the design of robust NP-based devices. If time allows, as an independent topic, the experimental characterization of freestanding membrane will also be briefly discussed.
Ph.D. Candidate, Department of Mechanical Engineering, Villanova University
Lu An is a PhD candidate in Department of Mechanical Engineering at Villanova University and has defended his PhD dissertation. His research focuses on synthesis, modeling and mechanical characterization of individual nano-sized materials and their assemblies. His research interests are focused on the mechanical behavior of nanomaterials, including nanoscale ceramic and metal materials, self-assembly of nanoparticles, and freestanding membrane including 2D materials. He has published 3 journal papers. He received his M.S. in Institute of Metal Research, Chinese Academy of Science in 2015, and his B.S. in Material Science and Engineering from Shandong University in 2012.