am7b15803_si_001.pdf (2.13 MB)
Intrinsic Size Effect in Scaffolded Porous Calcium Silicate Particles and Mechanical Behavior of Their Self-Assembled Ensembles
journal contribution
posted on 2017-12-14, 00:00 authored by Sung Hoon Hwang, Rouzbeh ShahsavariScaffolded
porous submicron particles with well-defined diameter, shape, and
pore size have profound impacts on 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, especially
at the level of individual particles and their ensemble states, is
a challenge. Herein, we focus on porous calcium-silicate submicron
particles with various diametersas a model systemand
perform 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 increases 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 of applied forces, while pressure-induced compacted
arrays exhibit no size effect. This study will impact tuning properties
of individual scaffolded porous particles and can have implications
on self-assembled superstructures exploiting porosity and particle
size to impart new functionalities.