Nanoindentation, Modeling, and Toughening Effects of Zirconia/Organic Nanolaminates

The present research is motivated by the remarkable toughness of natural nanostructured composites, specifically nacre, whose highly regular “brick‐and‐mortar” structure is composed of alternating layers of aragonite sheets separated by thin layers of organic material. Robust multilayer zirconium oxide (ZrO2)‐organic nanolaminates are deposited on Si wafers. Organic layers are synthesized employing layer‐by‐layer (LbL) deposition of alternating polyanion (PSS) and polycation (PAH) sublayers. Zirconia layers are deposited on LbL organic films employing magnetron sputtering from ZrO2 target and characterized employing TEM and XRD. Hardness and elastic modulus of the obtained nanostructures are measured employing nanoindentation technique. Yield stress of both constituents is obtained by fitting finite element (FE) nanoindentation simulations to nanoindentation measurements. Using the obtained mechanical data, the toughening of multilayered nanostructure relative to bulk zirconia is shown numerically by crack shielding mechanism that is demonstrated employing FE simulations. The higher toughness of the nanolaminates is also demonstrated by controlled scratch test. Bioinspired zirconia/organic nanolaminates are synthesized by PVD sputtering of ZrO2 on organic films deposited by a polyelectrolyte based layer‐by‐layer technique (LbL). Nanoindentation and FE modeling is used to obtain the mechanical properties of the structure. Sharp decrease of calculated driving force for crack propagation confirms the toughening effect of the organic phase and nanolaminar architecture.