Mesoscopic Crystallographic Textures on Shells of a Hyaline Radial Foraminifer Ammonia beccarii
Mesoscopic Crystallographic Textures on Shells of a Hyaline Radial Foraminifer Ammonia beccarii
复制标题
透明径向有孔虫 Ammonia beccarii 壳上的细观晶体结构
作者：
K. Nakajima;Y. Nagai;M. Suzuki;Y. Oaki;K. Naito;Y. Tanaka;T. Toyofuku;H. Imai
大多数有孔虫是简单的单细胞原生动物，它们创造出具有精确控制结构的钙质贝壳。我们研究了一种透明的放射状有孔虫氨贝卡利的多孔壳的晶体组构。钙质壳的复杂结构包括直径为2μm的直孔周围的微米单晶域，这些结构域被应变的中间区域分割。晶界中方解石的c轴几乎垂直于壳层表面。在壳壁的整个单晶区都观察到了介观织构，如间隔为∼200-450 nm的周期性侧线和间隔为∼150 nm的垂直裂纹。特殊的力学性能，如比冰洲石更低的杨氏模数和更高的硬度，归因于特殊的介观织构的存在。
Most foraminifera, simple unicellular protists, create calcareous shells with precisely controlled architectures. We investigated the crystal fabric of porous shells of a hyaline radial foraminifer, Ammonia beccarii. The complex structures of the calcitic shell include micrometric single-crystalline domains around a straight pore ∼2 μm in diameter which are divided by strained intermediate regions. The c axes of calcite in the domains were almost perpendicular to the shell surface. The mesoscopic textures, such as periodic lateral lines with a ∼200–450 nm interval and vertical cracks with a ∼150 nm interval, were observed throughout the single-crystalline domains in the shell wall. Specific mechanical properties, such as a lower Young's modulus and a higher hardness of the shells than those of Iceland spar, are ascribed to the presence of the specific mesoscopic textures.