Water-Dependent Micromechanical and Rheological Properties of Silica Colloidal Crystals Studied by Nanoindentation

• Published in: Nano letters Vol. 12; no. 9; pp. 4920 - 4924
• Main Authors: Gallego-Gómez, Francisco, Morales-Flórez, Víctor, Blanco, Álvaro, de la Rosa-Fox, Nicolás, López, Cefe
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 12.09.2012
• Subjects: Bridges (structures); Capillarity; Colloids; Colloids - chemistry; Condensed matter: structure, mechanical and thermal properties; Crystals; Elastic Modulus; Exact sciences and technology; Granular materials; Hardness Tests - methods; Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties; Macromolecular Substances - chemistry; Materials Testing; Mechanical analysis; Mechanical and acoustical properties of condensed matter; Mechanical properties of nanoscale materials; Molecular Conformation; Nanoindentation; Nanostructure; Nanostructures - chemistry; Nanostructures - ultrastructure; Particle Size; Physics; Silicon dioxide; Silicon Dioxide - chemistry; Surface Properties; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Viscosity; viscoplasticity; energy dissipation; capillary cohesion; wet granular materials; colloidal crystals; Nanoindentation; Nanohardness; Temperature dependence; Deformation; Colloids; Mechanical properties; Nanostructures; Silica; Nanometer scale; Hardness testing; Colloidal crystals; Hardness indentation; Quantitative chemical analysis
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl3024998

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.