Passive and active mechanical properties of biotemplated ceramics revisited

Abstract

Living nature and human technology apply different principles to create hard, strong and tough materials. In this review, we compare and discuss prominent aspects of these alternative strategies, and demonstrate for selected examples that nanoscale-precision biotemplating is able to produce uncommon mechanical properties as well as actuating behavior, resembling to some extent the properties of the original natural templates. We present and discuss mechanical testing data showing for the first time that nanometer-precision biotemplating can lead to porous ceramic materials with deformation characteristics commonly associated with either biological or highly advanced technical materials. We also review recent findings on the relation between hierarchical structuring and humidity-induced directional motion. Finally, we discuss to which extent the observed behavior is in agreement with previous results and theories on the mechanical properties of multiscale hierarchical materials, as well as studies of highly disperse technical materials, together with an outlook for further lines of investigation.

A Perspective on Bio‐Mediated Material Structuring

“…Biotemplating approaches differ by the number of hierarchical levels transferred to the final material. While for many purposes, the retention of less than three levels of hierarchy is sufficient, a field of research concerns itself with the truest‐possible retention of all superatomic structural features, in order to create novel material properties based on the evolved interplay between the hierarchical levels in the original template . Crucially, all existing biotemplating approaches can also be applied to the structures presented throughout this article.…”

“…Since, in nacre, it is influenced by the ratio of aragonite to protein, the minimal structure sizes of the latter determine the minimal sizes of the former. This design principle also aids to create technical ceramic materials with mechanical properties that are atypical for ceramics, such as the provision for noncatastrophic fracture behavior or large plastic deformation …”

Hierarchical Architectures to Enhance Structural and Functional Properties of Brittle Materials

“…[116] Mechanical properties of the former cell walls, of this material, are entirely different from the one of wood charcoal. [117] Yet, no systematic mechanical (in particular fracture mechanical) experiments have been performed, although this would be highly desirable in order to estimate the potential of these materials for applications as lightweight structural materials. [112] It has recently been suggested that this behavior is most probably primarily governed by the nanoscale porosity, with nanopore deformation, and -collapse being the preferred energy consuming mechanisms.…”

“…[112] It has recently been suggested that this behavior is most probably primarily governed by the nanoscale porosity, with nanopore deformation, and -collapse being the preferred energy consuming mechanisms. [117] Yet, no systematic mechanical (in particular fracture mechanical) experiments have been performed, although this would be highly desirable in order to estimate the potential of these materials for applications as lightweight structural materials. Fig.…”

Modeling the Compressive Behavior of Anisotropic, Nanometer‐Scale Structured Silica

“…We previously stated that “hierarchical silica from wood is a material with a plastic deformation behavior [...]“ . In this work, we present and discuss a dynamic model for such a material.…”