Frank Laboratory for Neutron Physics, Joint Institute for Nuclear Research, 6, Joliot Curie str, 141980, Dubna, Russian Federation.
Department of Structure of Matter, Earth and Atmospheric Physics and Astrophysics, Faculty of Physics, University of Bucharest, 405, Atomistilor str., 077125, Magurele, Ilfov, Romania.
Sci Rep. 2020 Jul 30;10(1):12869. doi: 10.1038/s41598-020-69859-2.
Two analytical methods based on the neutrons high penetrability, i.e. neutron diffraction (ND) and neutron computed tomography (NCT) were used to investigate the structure of the aragonitic skeleton of an exemplar/sample of Dipastraea pallida (Dana 1846), a modern hermatypic coral. ND was used to reconstruct the orientation distribution function (ODF) of the crystalline fibrils which compose the coral skeleton. Accordingly, 684 ND spectra were analyzed using the Rietveld method. The result confirmed the aragonite as the sole mineral component of coral skeleton, allowing to recalculate the ODF of aragonite fibrils and to represent it by means of (100), (010) and (001) crystallographic planes pole figures (PF). Experimental PF showed a remarkable similarity with PF recalculated by considering that all aragonite fibrils are oriented either along the growth axis of polyp cups or perpendicular to this direction. This result confirmed the previous observations based on optical microscopy, proving at the same time the availability of ND for such types of investigations. In turn, NCT evidenced the individual polyp cups, their interlocked 3D rigid porous structure as well as a periodic variation of density which could be attributed to a seasonal influence of the marine environment. Different from the classical X-ray computed tomography, the NCT, in view of neutron high cross-section for hydrogen, demonstrated the presence of a small amount of organic matter, otherwise transparent for X- and gamma rays.
两种基于中子高穿透性的分析方法，即中子衍射（ND）和中子计算机断层扫描（NCT），被用于研究现代四射珊瑚 Dipastraea pallida（Dana 1846）的方解石骨骼结构。ND 用于重建组成珊瑚骨骼的晶体原纤的取向分布函数（ODF）。相应地，使用 Rietveld 方法分析了 684 个 ND 光谱。结果证实了方解石是珊瑚骨骼的唯一矿物成分，从而可以重新计算方解石原纤的 ODF，并通过（100）、（010）和（001）晶面极图（PF）来表示。实验 PF 与考虑所有方解石原纤沿珊瑚杯生长轴或垂直于该方向取向时重新计算的 PF 具有显著相似性。这一结果证实了先前基于光学显微镜的观察结果，同时证明了 ND 适用于此类研究。反过来，NCT 证明了单个珊瑚杯、它们相互锁定的 3D 刚性多孔结构以及密度的周期性变化，这可能归因于海洋环境的季节性影响。与经典的 X 射线计算机断层扫描不同，鉴于中子对氢的高截面，NCT 显示出存在少量的有机物，否则对 X 射线和伽马射线是透明的。
