In situ compression of ceramic-organic supraparticles: Deformation and fracture behavior

Supercrystalline nanocomposites (SCNCs) feature intriguing functionalities and exceptional mechanical properties, but they are usually confronted with challenges when it comes to processing them in larger bulk form. One way to tackle this problem is a hierarchical approach, for which spherical SCNCs, i.e. supraparticles (SPs), are promising candidates as building blocks. Understanding the mechanical behavior of SPs is thus a key step towards the development of robust, multifunctional and macroscopic SCNCs. Hereby, in situ compression tests are performed on SPs with varying sizes and levels of crosslinking of their organic ligands. A size-dependent deformation and fracture behavior emerges. Plasticity occurs in larger SPs, while small ones exhibit brittle fracture. Surface stress and compaction affect the elastic modulus. Fracture initiation sites shift from the center of SPs to their equatorial belts with the decrease of SPs’ size. The inverse scaling relationship between fracture strength and SPs’ sizes is rationalized via Griffith theory.