贝壳珍珠层断裂过程的原位观察及其增韧机制分析

天然生物材料的组织结构特征及其与性能间的关系研究对于材料的仿生设计有重要意义.本文利用扫描电镜原位观察了受拉伸载荷作用下珍珠层中裂纹的萌生及扩展方式,并结合SEM和TEM技术研究了贝壳珍珠层微观组织结构,探讨了裂纹扩展过程中的增韧机制.结果表明,珍珠层相邻片层凹凸镶嵌互补,多边形文石晶体是由纳米级颗粒构成的多晶体.裂纹偏转,有机物桥联,纤维拔出,小孔聚结等多种增韧机制在裂纹扩展过程中协同作用,都源自珍珠层独特的微观结构,并提出片层的球冠型结构是导致珍珠层具有超常韧性的机制之一.

In Situ SEM Observation of Crack Propagation and Analysis of the Toughening Mechanism in Nacre

Microstructure of nacre is significant to understand the behavior of nacre and the biomimetic designing of materials. In the present paper the microstructure of nacre of bivalve shell is investigated by SEM and TEM. It is shown that in the nacre the neighbor aragonite laminae interpose perfectly. A aragonite tablet is polycrystal composed of nanoscale mineral islands. The in situ SEM observations of crack propagation in the nacre have been studied. The results indicate several toughening mechanisms, such as crack deflection, fibre pullout, organic matrix bridging and voids kinking, act in the nacre simultaneously, which attributes to its unique microstructure.