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Microstructure And Thermal Expansion Properties Of Ostrich Eggshell

Author(s):
A. Heredia, L. Lozano, C.A. Martinez-Matias, M.A. Peña-Rico, A.Rodriguez-Hernández, E. Villarreal, A. Martínez, M.V. García-Garduño, V.A. Basiuk, L. Bucio and E. Orozco

Description/Abstract:
N7.5

Abstract Body: The science of biomimetics has the potential to enrich many areas of technology and to design new materials but this design should be based on the understanding ob biomolecular mechanisms that make possible the preferencial arrangement, preferential growth, porosity, particle size, association with biopolymers, etc. All these properties make the biological materials renoweds models to mimic them due to their strength and thoughness. This is the case of ostrich eggshells. Formation of biominerals should be mimicked to synthesize composites based on crystal orientation and combinations of biomacromolecules related with common biological crystals, as in eggshells, bones and teeth, that is to say obtain ideas from the structures of living organisms to generate new hybrid materials. The aim of all kind of composite studies is the fabrication of organic-inorganic materials with controlled structures based on biologic ions that may lead to the fabrication of new materials with high performance and high function as well as environment beningnity. The structural arrangement of calcite crystals reached in ostrich eggshell is discussed in terms of the analysis of the eggshell microstructure and thermal expansion. The crystal orientation of crystallites is not homogeneous along the eggshell thickness: the microstructural characterization by scanning and transmission electron microscopy (STEM), powder X-ray diffraction (XRD) and thermal expansion experiments (TE) show that two main characteristic arrangement of calcite exist as well as high stability to thermal expansion in a wide range of values (from room temperature to near 450 Celsius degrees). In the outer surface the c-axis of calcite microcrystals appears closely aligned perpendicular to the outer eggshell surface; while in the inner surface, the hexagonal axis of the crystallites are directed along the eggshell surface. The authors acknowledge the financial support of UNAM DGAPA-PAPIIT IN113199; and A Heredia to National Council of Science and Technology (CONACyT) funding.

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