title: Vertically oriented structure and its fracture behavior of the Indonesia white-pearl oyster.
abstract: Structural calcites, aragonites, and the bonding organic network decide the growth, structure and mechanical properties of the mollusk bivalvia shell. Here, it was found out that the calcite prisms together with the coated organics construct another kind of 'brick and mortar' structure similar to the aragonite tablets. The calcite layer can be divided into three sublayers and direct evidences show that the calcite prisms are produced by two methods: nucleation and growing in the first sublayer; or fusing from the aragonites, which is quite different from some previous reports. The crystallographic orientation, micro hardness and crack propagations were tested and observed by XRD, micro harness tester, SEM and TEM. Submicron twin crystals were observed in the immature aragonite tablets. The fracture processes and the micro deformation of the aragonite tablets are detected by acoustic emission (AE) in the tensile tests, which gave the interpretation of the dynamical fracture processes: plastic deformation and fracture of the organics, and friction of the minerals at the first two stages; wear and fracture of the minerals at the third stage. Calcites and aragonites are combined and working together, like two layers of vertical 'brick and mortar's, ensuring the stable mechanical properties of the whole shell.
authors.affiliation: Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing, People's Republic of China; The Collaborative Innovation Center for Advanced Aero-Engine (CICAAE), Beijing University of Aeronautics and Astronautics, Beijing, People's Republic of China; Beijing Key Laboratory of Advanced Nuclear Materials and Physics, Beijing University of Aeronautics and Astronautics, Beijing 100191, People's Republic of China.
authors.forename: Guowei
authors.initials: G
authors.lastname: Chen
authors.affiliation: Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing, People's Republic of China; The Collaborative Innovation Center for Advanced Aero-Engine (CICAAE), Beijing University of Aeronautics and Astronautics, Beijing, People's Republic of China; Beijing Key Laboratory of Advanced Nuclear Materials and Physics, Beijing University of Aeronautics and Astronautics, Beijing 100191, People's Republic of China. Electronic address: Luo7128@163.com.
authors.forename: Hongyun
authors.initials: H
authors.lastname: Luo
authors.affiliation: Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing, People's Republic of China.
authors.forename: Shunfei
authors.initials: S
authors.lastname: Luo
authors.affiliation: Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing, People's Republic of China; The Collaborative Innovation Center for Advanced Aero-Engine (CICAAE), Beijing University of Aeronautics and Astronautics, Beijing, People's Republic of China; Beijing Key Laboratory of Advanced Nuclear Materials and Physics, Beijing University of Aeronautics and Astronautics, Beijing 100191, People's Republic of China.
authors.forename: Zhenying
authors.initials: Z
authors.lastname: Lin
authors.affiliation: Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing, People's Republic of China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Ma
mesh_terms: D060105:Animal Shells / Q000502:physiology*; D000818:Animals; D002119:Calcium Carbonate / Q000032:analysis*; D003461:Crystallography; D007214:Indonesia; D049911:Pinctada
chemical_list: D002119:Calcium Carbonate
keywords: Acoustic emission; Aragonite tablet; Bivalvia shell; Calcite prism; Fracture process; Oriental growth