Twin density of aragonite in molluscan shells characterized using X-ray diffraction and transmission electron microscopy
Twin density of aragonite in molluscan shells characterized using X-ray diffraction and transmission electron microscopy
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DOI：
10.1016/j.jcrysgro.2014.03.029
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发表时间：
2014-07-01
影响因子：
1.8
通讯作者：
Nagasawa, Hiromichi
中科院分区：
文献类型：
--
作者：
Kogure, Toshihiro;Suzuki, Michio;Nagasawa, Hiromichi
用X射线衍射仪和透射电子显微镜对构成各种贝壳结构的文石中的{110}孪晶密度进行了表征，找出了决定贝壳中孪晶密度的因素。几种地质成因的文石晶体也进行了对比研究。孪晶密度强烈地依赖于壳层的组织结构和种类。珍珠质结构的孪晶密度很低，与贝壳类别无关。另一方面，交叉片层(CL)结构中的孪晶密度在类或亚类之间有很大的差异，这主要与构成文石纤维的晶体方向有关。在具有致密的{110}孪晶的文石晶体中，透射电子显微镜观察到两种类型的孪晶结构：一种是具有平行孪晶面的规则多合成孪晶，另一种是具有两个或三个方向的不规则多环孪晶。前者可能是腹足纲特定亚纲的CL结构的特征。后者可能与c轴择优取向的显微组织中以(Hk0)界面为主的晶界有关，孪晶密度主要与显微组织中的晶体尺寸有关。(C)2014爱思唯尔B.V.保留所有权利。
{110} twin density in aragonites constituting various microstructures of molluscan shells has been characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM), to find the factors that determine the density in the shells. Several aragonite crystals of geological origin were also investigated for comparison. The twin density is strongly dependent on the microstructures and species of the shells. The nacreous structure has a very low twin density regardless of the shell classes. On the other hand, the twin density in the crossed-lamellar (CL) structure has large variation among classes or subclasses, which is mainly related to the crystallographic direction of the constituting aragonite fibers. TEM observation suggests two types of twin structures in aragonite crystals with dense {110} twins: rather regulated polysynthetic twins with parallel twin planes, and unregulated polycyclic ones with two or three directions for the twin planes. The former is probably characteristic in the CL structures of specific subclasses of Gastropoda. The latter type is probably related to the crystal boundaries dominated by (hk0) interfaces in the microstructures with preferred orientation of the c-axis, and the twin density is mainly correlated to the crystal size in the microstructures. (C) 2014 Elsevier B.V. All rights reserved.