Nanoindentation-based study of the mechanical behavior of bulk supercrystalline ceramic-organic nanocomposites

Bulk poly-supercrystalline ceramic-organic nanocomposites were produced and characterized with a nanoindentation-based study. These nanocomposites were processed using two different routines, to compare their properties with and without crosslinking the organic ligands interfacing the ceramic nanoparticles. Together with the expected material strengthening induced by crosslinking, a distinct response emerges when using Berkovich and cube-corner indenters. The supercrystalline materials are prone to compaction, cracking and chipping phenomena that become more severe when a sharper tip is employed, implying that a Berkovich indenter is more suitable for the evaluation of elastic modulus and hardness. The cube-corner tip, on the other hand, is employed for the investigation of fracture toughness, comparing two methods and multiple models available from the literature. The fracture toughness outcomes suggest that cracks evolve with a quarter-penny shaped profile at the indent's corners, and that extrinsic toughening mechanisms, such as plastic-like deformation and crack deflection, play a significant role.