S. Zhou; A. Li; V. Vilchez; O. Gavalda‐Diaz; F. Bouville
Journal of the American Ceramic Society 108 (2025) 70074.
Overcoming the conventional trade-off between strength and toughness is the
long-term goal in structural materials. One way to break this trade-off is to get
inspiration frombiological materials in which delicately tailored microstructures
elicit unusual properties. For example, by manipulating the packing of miner-
alized building blocks over centimeter scale and their interfaces, nacre triggers
process zone toughening, a toughening mechanism that increases its tough-
ness well beyond its constituents and even leads to pseudo plastic macroscopic
behavior. Anisotropic colloidal crystal composites, in which monodispersed sil-
ica rods are assembled into densely packed and ordered microstructure, are an
excellent way to study the emergence and potency of this process zone tough-
ening. In this study, we investigate whether the mechanical properties of the
silica rods can be improved by heat treating the mineral building blocks and its
effect on the toughening mechanisms. After heat treatment at different temper-
atures from 600 to 1300◦C, silica rods treated at 600◦Cwerefoundtomaintain
the original shape and to enable the assembly of anisotropic colloidal crystal
composites with an 80% volume fraction of minerals. The flexural strength and
modulus of individual rods were determined as 1.4 ± 0.5 and 20.9 ± 10.7 GPa,
respectively, using a scanning electron microscopy in situ micro-bending test.We
compare Young’smodulus, strength, and toughness values ofthe colloidal crystal
composites obtained before and after heat treatment through nanoindentation
and three-point bending tests. Our findings show that heat treatment effectively
increases the maximum strength by 40%, doubles Young’s modulus and tough-
ness while maintaining the damage delocalization toughening mechanism over
millimeters.