采用自悬浮定向流法制备纳米Ni粉体, 利用放电等离子烧结技术制备出了直径10 mm、厚2 mm, 致密度为96.8 %, 显微硬度为4.17 GPa的纳米块体材料。用X射线衍射仪、扫描电子显微镜和显微硬度计分析了烧结块体样品的相组成、晶粒尺寸、微观形貌和显微硬度。研究表明：随烧结温度的升高, 块体样品的致密度和晶粒尺寸增大, 当烧结温度为650 ℃时, 致密度最高, 晶粒尺寸为44.8 nm;显微硬度随烧结温度的增高先增大后减小, 当烧结温度为550 ℃时, 显微硬度最大为4.33 GPa;较高烧结温度下, 断口微观形貌的纳米级韧窝出现, 显示了韧性断裂的特征。

Ni nano-particles were prepared by flow-levitation method. And then, bulk nanocrystalline Ni samples, 10 mm in diameter and 2 mm in height with a relative density of 96.8 % and a microhardness of 4.17 GPa, were fabricated by spark plasma sintering using the nano-particles. The phase composition, grain size, microstructure and microhardness of the bulk samples were characterized by X-ray diffractometer, scanning electron microscope, and Vickers microhardness tester, respectively. The results indicate that the relative density and grain size increase with increasing sintering temperature. The optimal relative density has been obtained at the sintering temperature of 650 ℃, at which the average grain size is 44.8 nm. The microhardness first increases and then decreases with increasing sintering temperature. Its optimal value is 4.33 GPa obtained at the sintering temperature of 550 ℃. When the sintering temperature is high, the appearance of nano-dimples in fractography reveals the existence of ductile fracture morphology.