海水鲈鱼鳞片及鳍骨中羟基磷灰石的X射线极图法和ODF法择优取向分析

采用X射线衍射采集海水鲈鱼鳞片中羟基磷灰石(002)、(130)、(211)面网和鳍骨中羟基磷灰石(031)、(120)、(132)面网极图数据并计算了取向分布函数(ODF)以分析其择优取向特征,其中鳞片极图数据显示出羟基磷灰石结晶学c轴主要有3个择优取向,分别是与鳞片法线方向平行、相交39°和相交63°,而鳍骨极图推测出其羟基磷灰石c轴择优取向大致有五个方向,分别与鳍骨截面法线相交3°、9°、17°、24°和36°. ODF的计算结果表明,鳞片中羟基磷灰石有比较明显的择优取向是结晶学c轴近似平行于鳞片表面,同样,鳍骨ODF中羟基磷灰石择优取向为结晶学c轴近垂直于截面.极图和ODF结果上的差别是由于极图本身是晶体取向的二维投影图,单张极图显示的择优信息不够完整,因此ODF用来解析生物矿物的择优取向特征更为准确.鳞片和鳍骨中羟基磷灰石结构中的择优取向现象是因为生物矿化过程中有机质的调控作用而使结晶学c轴趋向平行胶原纤维长轴方向,并且这种择优特征也是硬体组织具有优良力学性能的要求.

Preferred orientation of hydroxylapatite in the scales and fins of seawater Lateolabrax japonicus determined using XRD pole figures and ODF

Pole figures measured using X-ray diffractometry were used to analyze the orientation of crystalline hydroxylapatite (HAP) in the scales and fins of seawater Lateolabrax japonicus. An orientation distribution function (ODF) was calculated based on the pole figures of the lattice planes(002),(130),and(211) of HAP in the scales and those of(031),(120),and(132) in the fins. The pole figures indicate that the c-axis of HAP prefers three primary orientations in the scales and five primary orientations in the fins. In the scales,the preferred orientations of the HAP c-axis are parallel to the normal line of the scale face and intersect the normal line at about 39° and 63°. In the fins,the HAP c-axis intersects the normal line of the cross-section at 3°,9°,17°,24°,and 36°. However,the calculated ODFs show that the preferred orientations of the HAP c-axes are nearly parallel to the face of the scales and perpendicular to the cross-section of the fins. As the pole figure only reflects a two-dimensional projection of the crystalline orienta-tions,the preferred orientations determined by the pole figures are not very accurate. Conversely,three-dimensional ODF is more suit-able for analyzing the preferred orientation of biominerals than the two-dimensional projection. The tendency of the c-axis to be parallel to the collagen fibers is controlled by organic matter and provides a good mechanical performance in hard tissue.