title: Water-dependent micromechanical and rheological properties of silica colloidal crystals studied by nanoindentation.
abstract: Here we show the suitability of nanoindentation to study in detail the micromechanical response of silica colloidal crystals (CCs). The sensitivity to displacements smaller than the submicrometer spheres size, even resolving discrete events and superficial features, revealed particulate features with analogies to atomic crystals. Significant robustness, long-range structural deformation, and large energy dissipation were found. Easily implemented temperature/rate-dependent nanoindentation quantified the paramount role of adsorbed water endowing silica CCs with properties of wet granular materials like viscoplasticity. A novel "nongranular" CC was fabricated by substituting capillary bridges with silica necks to directly test water-independent mechanical response. Silica CCs, as specific (nanometric, ordered) wet granular assemblies with well-defined configuration, may be useful model systems for granular science and capillary cohesion at the nanoscale.
authors.affiliation: Instituto de Ciencia de Materiales de Madrid, ICMM (CSIC), C/Sor Juana Inés de la Cruz 3, 28049 Madrid, Spain. francisco.gallego@icmm.csic.es
authors.forename: Francisco
authors.initials: F
authors.lastname: Gallego-Gómez
authors.forename: Víctor
authors.initials: V
authors.lastname: Morales-Flórez
authors.forename: Alvaro
authors.initials: A
authors.lastname: Blanco
authors.forename: Nicolás
authors.initials: N
authors.lastname: de la Rosa-Fox
authors.forename: Cefe
authors.initials: C
authors.lastname: López
mesh_terms: D003102:Colloids / Q000737:chemistry*; D055119:Elastic Modulus; D006245:Hardness Tests / Q000379:methods*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties; D014783:Viscosity
chemical_list: D003102:Colloids; D046911:Macromolecular Substances; D012822:Silicon Dioxide