Nacre (mother-of-pearl) from mollusc shells is a biologically formed lamellar ceramic. The structure and growth of nacre has been the subject of study due to its remarkable mechanical properties produced by its deceptively simple microstructure makes its fracture toughness about 3000 times that of aragonite, its main component. More than 95 weight percent of nacre consist of tablets of aragonite, an orthorhombic form of calcium carbonate (CaCO3). These tablets lie in a matrix of biological macromolecules, which make up the remaining composition. The aragonite tablets are about 0.5 μm thick and roughly 10 μm across. Layers of the single-crystalline tablets are separated by thin (20 nm to 30 nm) organic layers containing nanometer-scale pores. In this talk we will discuss this brick-and-mortar microstructure, as a perfect model for soft and hard (bio-inorganic) nanocomposites, which gives nacre its exceedingly high fracture toughness and elastic modulus.
Back to Solid State and Materials Chemistry II
Back to The 37th Middle Atlantic Regional Meeting (May 22-25, 2005)