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Biomimetic Synthesis of Nacre Composite

Author: HuYanLi
Tutor: PeiZhongHua
School: Southwest University of Science and Technology
Course: Applied Chemistry
Keywords: Hen eggwhite Biomimetic synthesis Nacre Calcium carbonate Aspartic acid
CLC: TB332
Type: Master's thesis
Year: 2010
Downloads: 20
Quote: 0
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Abstract


Based on the similar with major proteins between hen egg-white and nacre, stack-like crystallization composites of calcium carbonate were biomimetic synthesized by the induction of hen egg white. The main conclusions are as follows:1. The stack-like crystallization of calcium carbonate was prepared by chemical precipitation, induced by the hen egg white whose proteins can be changed into gel in alkaline condition. The research conditions （such as minerliazation temperature, the concentration of egg white, and drying methods） was investigated. The optimum process conditions to get stack-like crystallization of calcium carbonate are mineralized temperature 15±2℃, time 2h, egg whitie concentration 7g/L, direct drying under 55℃. Results of SEM and TEM indicate that gelling eggwhite mediated the formation of the“stack-like”layered calcium carbonate aggregates composed of considerable nanosheets, and the results of FT-IR and XRD explain the reason of“stack-like”crystallization formation. The average elastic modulus and the hardness of stack-like calcium carbonate hybrid material were assessed 0.9952 GPa and 0.0415 GPa with Nano-indenter test, respectively.2. The stack-like crystallization of calcium carbonate in the presence of hen egg white under direct drying by gaseous diffusion process was attainded affter analysing the formation process of nacre. Many systematic studies of the influence of various experimental parameters, such as concentration of CaCl2, egg white, and mineralized time. Results showing that the marked morphological changes on the stack-like layered calciumcarbonate depend on the concentration of CaCl2 and egg white. The mineralized time has great influence on the morphology and polymorph. With the further reaction process, we obtain the crystal aggregates displying“stack-like”structure. The spacing of layers and interlamellar layers became more and more small. The optimum process conditions to get stack-like crystallization of calcium carbonate are mineralized temperature 28±2°C, time 15 to36h, egg whitie concentration 0.015g/L, CaCl2 concentration 0.30M, direct drying under 55℃.3. The stack-like crystallization of calcium carbonate in the presence of aspartic acid under direct drying by gaseous diffusion process. It proves that aspartic acid in the hen egg white has great influence on the formation of stacke-like cystal aggregates. With increasing of the concentration of aspartic acid, the spacing distance and interlamellar layers became larger. The gowth rate of calcium carbonate became slow, and the vaterite transfer into calcite. Mineralized time also influence on the morphology and polymorph. The samples most is like nacreous layers of calcium carbonate when the concentration is 0.30 g/L-1.00g/L, time is 6 to15h.This study have been performed on the fomation of laminate struture of calcium carbonate crystallization with egg white, which provide a new idea to mimic the organic matrix in the mollusk shells. The synthesis technology are simple, environmental friendly, process control, larger sample preparation, which have great effect on biomimetic research.

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CLC: > Industrial Technology > General industrial technology > Materials science and engineering > Composite materials > Non-metallic composite materials
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