Microstructure-driven mechanical and electromechanical phenomena in additively manufactured nanocrystalline zinc oxide.

Advances in nanoscale additive manufacturing (AM) offer great opportunities to expand nanotechnologies; however, the size effects in these printed remain largely unexplored. Using both in-situ nanomechanical and electrical experiments and MD simulations, this study investigates additively manufactured nano-architected nanocrystalline ZnO (nc-ZnO) with ~7 nm grains and dimensions spanning 0.25-4 µm. These nano-scale ceramics are fabricated through printing and subsequent burning of metal ion-containing hydrogels to produce oxide structures. Electromechanical behavior is shown to result from random ordering in the microstructure and can be modeled through a statistical treatment. A size effect in the failure behavior of AM nc-ZnO is also observed and characterized by the changes in deformation behavior and suppression of brittle failure. MD simulations provide insights to the role of grain boundaries and grain boundary plasticity on both electromechanical behavior and failure mechanisms in nc-ZnO. The frameworks developed in this paper extend to other AM nanocrystalline materials and provide quantification of microstructurally-drive limitations to precision in materials property design.