A review of models for single particle compression and their application to silica microspheres

We report on the deformation behavior of single silica microspheres. For the first time a detailed discussion on the quantitative evaluation of force–deformation data in the elastic and plastic regime is given. The microspheres are compressed between two flat plates of a custom built manipulation device supported by a scanning electron microscope. The device allows a high sample throughput enabling full statistical evaluation of force–deformation data of single microspheres. Existing theories describing the deformation behavior of single spheres are discussed and applied to the elastic and plastic deformation regime of silica microspheres. The results obtained from the theories are compared between each other and values reported in literature. The silica microspheres exhibit a significantly different deformation behavior than expected from bulk fused silica, i.e. a distinct plastic deformation behavior. Furthermore, a significant decrease in Young’s modulus and hardness was observed caused by high porosity and reduced crosslinking of silicon atoms, respectively, that is inherent to silica produced by Stöber synthesis. However, the calculated contact pressures exceed the compressive strength of bulk fused silica by at least a factor of two as an effect of a reduced amount of material flaws in microstructures.

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• Review on deformation models of particles.
• In situ deformation study of silica microspheres.
• Observation of plastic deformation and crack formation.
• Statistical data evaluation.
• Calculation of Young’s modulus, yield strength and hardness.