High strength and damage-tolerance in echinoderm stereom as a natural bicontinuous ceramic cellular solid

Abstract

Due to their low damage tolerance, engineering ceramic foams are often limited to non-structural usages. In this work, we report that stereom, a bioceramic cellular solid (relative density, 0.2–0.4) commonly found in the mineralized skeletal elements of echinoderms (e.g., sea urchin spines), achieves simultaneous high relative strength which approaches the Suquet bound and remarkable energy absorption capability (ca. 17.7 kJ kg−1) through its unique bicontinuous open-cell foam-like microstructure. The high strength is due to the ultra-low stress concentrations within the stereom during loading, resulted from their defect-free cellular morphologies with near-constant surface mean curvatures and negative Gaussian curvatures. Furthermore, the combination of bending-induced microfracture of branches and subsequent local jamming of fractured fragments facilitated by small throat openings in stereom leads to the progressive formation and growth of damage bands with significant microscopic densification of fragments, and consequently, contributes to stereom’s exceptionally high damage tolerance.

A 3D hierarchical porous adsorbent constructed by cryo-polymerization for ultrafast uranium harvesting from seawater

“…2A). 45,46 Fig. 2B shows the 3D structure of the adsorbent skeleton, which has a well-ordered vertical pore structure (ESI Movie 2 †).…”

A 3D-printed CuNi alloy catalyst with a triply periodic minimal surface for the reverse water-gas shift reaction

“…Triply periodic minimal surface (TPMS)-based lattice structures have received considerable attention in various industrial sectors owing to their unique geometric structure of smooth surfaces with zero mean curvature and periodic distribution in three perpendicular directions. 14,[21][22][23] Compared with the honeycomb structure, these surfaces can split the space into two interlocked channels through a smooth transition rather than an angular transition. 24,25 The smooth and ordered microchannels with a TPMS can decrease the pressure drop and enhance the heat transfer effects and ow efficiency, thereby providing signicant potential for the design of monolithic xed-bed catalysts.…”

“…In addition, the exceptional mechanical strength derived from the unique geometry of a TPMS can effectively improve the structural stability of a catalyst during actual operation. 23,26 Herein, we have fabricated a monolithic CuNi alloy catalyst with ordered microchannels, composed of a typical TPMS, using a three-dimensional (3D) printing technology known as selective laser melting (SLM) to investigate the inuence of geometrical structure on the catalytic performance of reverse water-gas shi (RWGS) reactions. The intrinsic catalytic performance of CuNi alloys has been extensively demonstrated to surpass that of their respective pure metals in various reactions.…”

“…In addition, the exceptional mechanical strength derived from the unique geometry of a TPMS can effectively improve the structural stability of a catalyst during actual operation. 23,26…”

Composite material in the sea urchin Cidaris rugosa : ordered and disordered micrometre-scale bicontinuous geometries

“…Since then, authors have designated the 'rectilinear' stereom type, found in several species of Cidaroids [8], to the Primitive surface [7,12,26]; however a three-dimensional quantitative descriptive of this stereom type is lacking. Recently, a related ordered bicontinuous form, the so-called Diamond surface, was discovered in the ossicles of the starfish Protoreaster nodosus [3] and in the fossilized skeleton of a 385 Myr crinoid Haplocrinites boitardi [12], sparking a renewed interest into the calcite microstructures of echinoderms, including their potential in biomimetics [4,5,27,28].…”