Structural and mechanical evolution of Tridacna gigas during permineralization

Investigation on the Microstructures and Mechanical Properties of the Shells of Tridacna crocea

“…The self-locking feature has not been reported in aragonite cross-lamellar structures, nor in T. gigas, , a sister species of T. crocea.…”

“…The mechanical performance and its relationship with the microstructures of the cross-lamellar structures, and the formation mechanism of cross-lamellar structures in biological shells have been investigated by many research groups. ,, The strong mechanical properties of the cross-lamellar structures are mainly attributed to their multilevel structural arrangements and abundant interfaces on several scales. The value of nanohardness is variable in different species, between 2.71 and 5.8 GPa. , In general, the compression strength along the parallel direction (termed as the longitudinal cross section in this work) is higher than that along the perpendicular direction (termed as the transverse cross section in this work) of shells of Saxidomus . , The overall distribution of flexural strength is between 50 and 200 MPa. , The toughening mechanisms of the cross-lamellar structures indicate that the structural features such as uncracked-ligament bridging, fiber bridging, crack deflection, microcracking, and channel cracking, along with the plastic deformation of the aragonite units, can enhance the mechanical properties. ,,, Hou and co-workers pointed out there is a difference between the microstructure and mechanical properties of jade (permineralized) and normal shells of Tridacna gigas . It was found that the increased aragonite crystal size and decreased organic matter content during permineralization play important roles in the mechanical properties.…”

“…The relationship of the microstructures and the mechanical properties of different biogenic aragonite with cross-lamellar structures has been reported. ,,,− However, differences in the microstructures and mechanical properties between different locations of the shells with cross-lamellar structures have rarely been reported . In this work, the multilevel ordered micro- and nanostructures in the main part and the rib part of the shells of Tridacna crocea were investigated in detail.…”

“…Biogenic calcium carbonate minerals very often exhibit improved mechanical properties and hierarchically ordered micro- and nanostructures incorporated with about 1–5 wt % organic components. − The mollusk shells are a kind of typical biogenic calcium carbonate minerals with high mechanical properties that can protect soft tissues against deep-sea water pressure, seawater erosion, and predation. − The three most commonly formed phases of calcium carbonate that can be found in biological organisms are calcite, − aragonite, ,,− and vaterite, , while biogenic vaterite is a rare phase in organisms in comparison to the other two phases of calcium carbonates. Biogenic calcites contain prismatic and foliated microstructures .…”

“…Biogenic calcites contain prismatic and foliated microstructures . Biogenic aragonite may form hierarchically highly ordered microstructures such as a layered brick and mortar structure of nacre, ,− ,− fiber strips, − and cross-lamellar structures. ,,− , As one kind of typical biogenic aragonite minerals, aragonite cross-lamellar structures also exhibit a tougher feature than geological aragonite. Especially, cross-lamellar structures exhibit the highest fracture toughness (230 MPa) among all mollusk microstructures .…”