Intrinsic size-effect in scaffolded porous calcium silicate particles and mechanical behavior of their self-assembled ensembles.

Title Intrinsic size-effect in scaffolded porous calcium silicate particles and mechanical behavior of their self-assembled ensembles.
Authors S.Hoon Hwang; R. Shahsavari
Journal ACS Appl Mater Interfaces
DOI 10.1021/acsami.7b15803
Abstract

Scaffolded porous submicron particles with well-defined diameter, shape and pore size have profound impacts in drug delivery, bone-tissue replacement, catalysis, sensors, photonic crystals and self-healing materials. However, understanding the interplay between pore size, particle size, and mechanical properties of such ultrafine particles, specially at the level of individual particles and their ensemble states, is a challenge. Herein, we focus on porous calcium-silicate submicron particles with various diameters - as a model system - and perform an extensive 900+ nanoindentations to completely map out their mechanical properties at three distinct structural forms from individual submicron particles to self-assembled ensembles to pressure-induced assembled arrays. Our results demonstrate a notable "intrinsic size-effect" for individual porous submicron particles around ~200-500 nm, induced by the ratio of particle characteristic diameter to pore characteristic size distribution. Increasing this ratio results in a brittle-to-ductile transition where the toughness of the submicron particles increase by 120%. This size-effect becomes negligible as the porous particles form superstructures. Nevertheless, the self-assembled arrays collectively exhibit increasing elastic modulus as a function applied forces while pressure-induced compacted arrays exhibits no size-effect. This study will not only have an impact on tuning properties of individual scaffolded porous particles, but can have implications on self-assembled superstructures exploiting porosity and particle size to impart new functionalities.

Citation S.Hoon Hwang; R. Shahsavari.Intrinsic size-effect in scaffolded porous calcium silicate particles and mechanical behavior of their self-assembled ensembles.. ACS Appl Mater Interfaces. 2017. doi:10.1021/acsami.7b15803

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