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Biomimetic Synthesis, Hierarchical Assembly and Mechanical Properties of Calcite/Chitosan Composites in a Three‐Dimensional Chitosan Scaffold
Author(s) -
Xiao Junwu,
Yang Shihe
Publication year - 2011
Publication title -
advanced engineering materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.938
H-Index - 114
eISSN - 1527-2648
pISSN - 1438-1656
DOI - 10.1002/adem.201080068
Subject(s) - calcite , materials science , biomineralization , nanocomposite , crystallization , crystallinity , nanocrystal , chemical engineering , nucleation , phase (matter) , amorphous calcium phosphate , chitosan , nanoparticle , calcium carbonate , amorphous calcium carbonate , biomimetic synthesis , composite material , nanotechnology , mineralogy , calcium , chemistry , organic chemistry , metallurgy , engineering
Biominerals provide excellent mechanical properties for skeletal support and protection, rivaling and even outperforming those of many engineered ceramics fabricated at high temperatures and pressures. However, the mechanisms of biomineralization are still poorly understood. To make progress in this direction, here we study the crystallization of calcite (thermodynamically the most stable CaCO 3 phase) from an amorphous calcium carbonate (ACC) precursor inside a three‐dimensional insoluble chitosan scaffold. A hydrated ACC phase with complete disorder is found to first nucleate from citrate–calcium ion pairs and subsequently transform into stabilized ACC nanoparticles with a short‐range order of calcite, which then crystallize and grow into calcite nanocrystals via the transient ACC phase, instead of direct crystallization from the hydrated ACC precursor as reported previously. The calcite nanocrystals are aggregated and collectively oriented into rough rhombohedral calcite mesocrystals, and eventually evolve into smooth mesocrystals. Mechanical property characterizations of the novel bio‐inspired nanocomposites show a strong dependence on the content of the constituent inorganic nanocrystals. Furthermore, the reduced elastic modulus is closely related to the interfacial interaction strength between the inorganic nanocrystals and the organic matrix, whereas the hardness is dependent on the crystallinity of the constituent inorganic mesocrystals in the nanocomposites.