Nanoscale structural and mechanical characterization of heat treated nacre

Nanoscale structural and mechanical characterization of heat treated nacre has been carried out. Two phase transformations were identified. i.e., from aragonite to calcite in the 500 degrees C heat treated nacre and from aragonite to calcium oxide (CaO) in the 1000 degrees C heat treated nacre. The brick-mortar architecture remains in the 500 degrees C heat treated nacre, but loses in the 1000 degrees C heat treated nacre. The heat treatment burned out the biopolymer in nacre. Nanoscale holes were discovered at the aragonite platelet boundaries and on the platelet surfaces. The heat treated nacre exhibits a sharp loss in elastic modulus and hardness compared with the fresh nacre. (C) 2009 Elsevier B.V. All rights reserved.