Synchrotron XRD Study on the Nacre of Freshwater Bivalve H. cumingii Lea

doi:10.3724/SP.J.1077.2012.00524

Abstract

Abstract:

Synchrotron XRD was used to study internal stress of nacre and microstructure of individual nacre tablet in the shell of freshwater bivalve H. cumingii Lea. The diffraction patterns show some biopolymers (intra-crystalline organic matrix) are occluded inside nacre tablets during biomineralization, causing that nacre powder exhibits tensile- like internal stress which is strongly anisotropic along different vectors of the reciprocal lattice. The characteristic of internal stress suggests that the intra-crystalline organic matrix is most probably arranged in the specific form. And line profile analysis which is conducted with the synchrotron XRD patterns of heated and unheated nacre powder samples, further confirms that the intra-crystalline organic matrix is adsorbed on (002) atomic planes of nacre tablets. The findings will facilitate the study on the formation mechanism and the strengthening and toughening mechanism of the nacre and provide theoretical basis for designing new organic-inorganic composite with high performances and cultivating pearl.

Key words: nacre, synchrotron XRD, microstructure, internal stress

CLC Number:

TB332

YAN Xiao-Hui, WANG Sheng-Nan, DU Bo, WANG Xiao-Xiang. Synchrotron XRD Study on the Nacre of Freshwater Bivalve H. cumingii Lea[J]. Journal of Inorganic Materials, 2012, 27(5): 524-528.

Figures/Tables 5

Fig. 1 Selected synchrotron diffraction peaks taken from H. cumingii powder samples annealed at 200℃ for 0, 0.5, 12 and 60 h (a) (002) reflection; (b) (012) reflection; (c) (111) reflection: (d) (021) reflection

Fig. 2 Comparison between nacre block and nacre powder sample in angular positions of their synchrotron (002) diffraction profile

Fig. 3 Comparison between nacre powder unbleached and bleached for two weeks in angular positions of their synchrotron (002) diffraction profile

Fig. 4 (a) Crystalline sizes and (b) averaged microstrain fluctuations along different crystallographic directions for H. cumingii plotted as functions of annealing time

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