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The microstructures and mechanical properties of Clinocardium californiense shell were investigated in relation to the different parts of shell. It is found that the shell can be divided into three parts, that is, the dorsal side, body part, and marginal side based on the variation of microstructures along the longitudinal cross section. Specifically, all areas exhibit a cross-lamellar structure on the dorsal side, and a hierarchical structure comprising three layers including inner (with a cross-lamellar structure), middle (with a complex cross-lamellar structure), and outer (with a prismatic structure) layers was observed on the body part, whereas on the marginal side, the orientation of aragonite sheets shows an obvious deflection. The structural architecture, the dimensions of different-order lamellae in the same kind of structure and the orientation between the indenting direction and aragonite sheet all contribute to the unique mechanical properties of this shell. It is also found that a low value of the ratio of hardness-to-Young's modulus ( H/ E) corresponds to an improved indentation toughness. The middle layer with the densest and most complicated structure on the body part shows the lowest H/ E ratio and the highest hardness and Young's modulus. [ABSTRACT FROM AUTHOR]

Abstract: The effect of short-term pre-annealing treatment on the compressive deformation and damage behavior of ultrafine-grained (UFG) copper produced by equal channel angular pressing (ECAP) has been studied by mechanical tests and microstructural observations. It is found that a controlled 10-min pre-annealing treatment on the UFG copper below the recrystallization temperature can result obviously in a higher strength (higher flow stress level) and a higher flow stability (lower stress softening rate) under uniaxial compression, as compared to the case of as-ECAPed sample. Observations of surface and interior deformation damage features indicate that, compared to the as-ECAPed copper sample, the pre-annealed ECAPed copper at less than recrystallization temperature may exhibit a better compressive plastic deformation capacity, namely, the destructive deformation morphology of large-scale shear bands normally observed in compressed as-produced UFG copper sample would not appear in compressed pre-annealed sample, except for a relatively smooth surface morphology featuring some ‘step’ reliefs with a few discontinuous shear bands and non-propagation voids. Finally, the deformation mechanism of different kinds of severe plastic deformation (SPD) processed UFG materials as well as their pre-annealing effects are further discussed, and a general rule is summarized as follows: an appropriate selection of pre-annealing temperature and annealing time is needed for improving both strength and ductility of SPDed materials with a microstructure comprising equiaxed grains and well-defined grain boundaries. [Copyright &y& Elsevier]

To explore some new approaches to designing novel mimetic architecture for bone implant materials, the conversion of a natural ceramic of Saxidomus purpuratus shell to hydroxyapatite (HAp) was investigated in the present study by using a pre-treatment in phosphate buffer solution (PBS) and an in vitro assessment in stimulated body fluid (SBF) solution. The main concern was focused on a comparison of in vitro bioactivity on the outer layer (porous fibrous/blocky structure) and inner layer (complex crossed-lamellar) of the shell. It is found that the apatites are deposited more compactly on the surface of porous blocky layer than crossed-lamellar layer in the preliminary stage of immersion in PBS for the same time. However, after a subsequent in vitro mineralization in SBF for a relatively long time of 4 weeks, the bioactive bone-like apatite layers are formed on the both inner and outer layers with different structures. Importantly, the results have demonstrated that the crossed lamellar structure with a good combination of mechanical and biological performances can be well referenced as a bio-inspired composite structure for hard tissue replacements. [ABSTRACT FROM AUTHOR]