The aim of the present investigation is to develop mechanochemically synthesized nano-crystalline hydroxyapatite (nHAp) bioceramics using clam seashells and phosphoric acid by varying the CaO:H3PO4 acid at different wt% ratios, i.e. 1:0.75, 1:1.0, 1:1.25, 1:1.5 and 1:1.75. The synthesized powders were characterized using X- ray diffraction ( XRD), scanning electron microscope and high resolution transmission electron microscopy. XRD results showed that the average crystallite size of the powder varies from 54 to 69 nm with enhancement in its crystallinity from 85 to 96%. An attempt was laid to access the mechanical behavior of nHAp through indentation at the micron scale. Microindentation derived properties, viz. microhardness, fracture toughness, brittleness index and fracture energy showed significant variation with CaO:H3PO4 mixing ratio due to the evolution of HAp and other calcium phosphate based phase(s). The fracture behavior illustrated a considerable improvement with the variation in CaO:H3PO4 mixing ratio. GRAPHICAL ABSTRACT

中文翻译：

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雇佣蛤壳机械化学合成纳米晶羟基磷灰石的结构和力学行为

本研究的目的是通过改变不同重量百分比的 CaO:H3PO4 酸，即 1:0.75、1:1.0、1:1.25，使用蛤壳和磷酸开发机械化学合成的纳米晶羟基磷灰石 (nHAp) 生物陶瓷, 1:1.5 和 1:1.75。使用 X 射线衍射 (XRD)、扫描电子显微镜和高分辨率透射电子显微镜对合成的粉末进行表征。XRD 结果表明粉末的平均晶粒尺寸从 54 到 69 nm 不等，结晶度从 85% 到 96% 不等。试图通过微米级的压痕来获得 nHAp 的机械性能。微压痕衍生属性，即。显微硬度、断裂韧性、脆性指数和断裂能随 CaO 显示出显着变化：由于 HAp 和其他磷酸钙基相的演变，H3PO4 混合比。断裂行为表明随着 CaO:H3PO4 混合比的变化有相当大的改善。图形概要