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The Role of Boundaries and Other Microstructural Features on Emergent Mechanical and Mechanically-Coupled Phenomena at the Nanoscale


Gallivan, Rebecca Anne (2023) The Role of Boundaries and Other Microstructural Features on Emergent Mechanical and Mechanically-Coupled Phenomena at the Nanoscale. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/gv3v-9k07.


As nanotechnology continues to advance, the need for smaller, structurally complex materials has grown. However, these microscopic (10⁶) and nanoscopic (10⁹) structures often display unexpected changes in mechanical properties as compared to their macroscopic counterparts. Nanomechanical studies investigating size-effects in stiffness, strength, recoverability, ductility, and fracture, reveal an intimate interplay between the breakdown in continuum behavior and the energetic landscape of microstructural mechanisms. Additive manufacturing opens new opportunities to explore this microstructure-mechanics relationship as it enables the micro- and nano-scale production of novel materials and microstructures. While existing studies on structural and functional materials highlight the unique size-scale behavior, a large gap remains in our understanding of the complex relationship between microstructure and material performance. This work investigates the interactions and mechanisms that give rise to emergent nanoscale phenomena. With microstructural characterizations, we demonstrate the role of boundaries and interfaces on mechanical and mechanically-coupled behavior in (1) dense nanowire arrays, (2) nano-architected nanocrystalline zinc oxide, and (3) highly-twinned additively manufactured metallic systems. This work provides critical insights into the mechanisms underlying the observed emergent phenomena and further opens our fundamental intuition for microstructure-mechanics relationships in materials at the nanoscale.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Microstructure, Nanomechanics, Additive Manufacturing, Nanofabrication, Material Characterization
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Materials Science
Awards:Demetriades-Tsafka-Kokkalis Prize in Nanotechnology or Related Fields, 2023.
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Greer, Julia R.
Thesis Committee:
  • Falson, Joseph (chair)
  • Faber, Katherine T.
  • Fultz, Brent T.
  • Greer, Julia R.
Defense Date:30 June 2022
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0016945
Department of Energy (DOE)DE-SC0019166
Amazon AI4Science FellowshipUNSPECIFIED
Record Number:CaltechTHESIS:07112022-193425820
Persistent URL:
Related URLs:
URLURL TypeDescription adapted for Chapter 2 discussed in Chapters 5 and 6 published doctoral work not adapted for the thesis
Gallivan, Rebecca Anne0000-0001-6516-2180
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:14970
Deposited By: Rebecca Gallivan
Deposited On:20 Jul 2022 18:54
Last Modified:08 Nov 2023 00:27

Thesis Files

[img] PDF (Full Thesis) - Final Version
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[img] Video (AVI) (Nanowire Bundle Compression Video) - Supplemental Material
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