Viswanath B, Raghavan R, Gurao N P, Ramamurty U, Ravishankar N
Materials Research Centre, Indian Institute of Science, Bangalore 560012, India.
Acta Biomater. 2008 Sep;4(5):1448-54. doi: 10.1016/j.actbio.2008.02.031. Epub 2008 Apr 1.
Mechanical properties of flux-grown tricalcium phosphate (TCP) single crystals ranging in size from 50 to 75microm have been characterized by performing micro- and nanoindentation on their facets. Notwithstanding the inherent brittleness and anisotropy, these single crystals exhibit nanoscale plasticity in the form of pile-up around the edges of indents. A similar plastic response was observed in hydroxyapatite (HA) single crystals during nanoindentation in an earlier study. The hardness and elastic modulus obtained during nanoindentation are discussed in comparison with the polycrystalline forms of both TCP and HA found in the literature. The indentation fracture toughness values of TCP single crystals were found to be higher than those of HA single crystals. The higher values are attributed not only to the difference in crystal structure and corresponding differences in surface energy, but also to extensive crack bridging by ligament formation across crack faces during crack propagation.
通过对尺寸在50至75微米之间的助熔剂生长磷酸三钙（TCP）单晶的晶面进行微观和纳米压痕试验，对其力学性能进行了表征。尽管这些单晶具有固有的脆性和各向异性，但它们在压痕边缘周围以堆积的形式表现出纳米级的可塑性。在早期的一项研究中，在纳米压痕试验中，羟基磷灰石（HA）单晶也观察到了类似的塑性响应。将纳米压痕试验中获得的硬度和弹性模量与文献中报道的TCP和HA多晶形式进行了比较讨论。发现TCP单晶的压痕断裂韧性值高于HA单晶。较高的值不仅归因于晶体结构的差异以及相应的表面能差异，还归因于裂纹扩展过程中穿过裂纹面形成的韧带导致的广泛裂纹桥接。
