Al_2O_3/Ni包裹粉体的制备、烧结行为及其显微结构研究

Preparation, Sintering Behavior and Microstructure of Al_2O_3-Coated Ni Powders

利用非均相沉淀包裹技术，在铝无机盐溶液中制备出氧化铝前驱体包裹纳米镍颗 粒的复合粉体，并通过能量发散能谱（ＥＤＳ）以及俄歇电子能谱（ＡＥＳ）研究包裹粉体的成分构 成，发现镍纳米颗粒表面均匀地包裹一层氧化铝的前驱体．煅烧后的包裹粉体在氩气氛中进行 热压烧结．结果表明，与溶胶－凝胶法制备的粉体相比，包裹粉体可以在较低的温度下达到致 密化．烧结后的材料其显微结构明显不同于球磨粉体烧成的材料，不论在氧化铝晶界或晶内， 镍颗粒与氧化铝之间都有孔隙，这是由于镍的热膨胀系数比氧化铝的热膨胀系数大引起的． Ａｌ２Ｏ３／Ｎｉ复合材料的断裂方式以沿晶断裂为主.

Alumina precursor-coated nanosized Ni powders were prepared by the heterogeneous precipitation method in the aluminium salt solution. The chemical composition of the as-prepared coated powder was characterized by energy dispersive spectra and Auger electron spectra. It revealed that nanosized Ni particles were homogeneously coated with layers of alumina hydrate. The calcined powders that were performed in argon were hot pressed in a protective atmosphere of argon. The experimental results indicate that the calcined powders can be sintered to nearly fully dense at a lower temperature as compared with that from sol-gel prepared powder mixtures. The microstructures of these sintered specimens are different from that of ball-milled and hot-pressed counterparts. Irrespective of the location of Ni particles in alumina matrix, there exist holes at the interfaces between alumina grains and Ni particles, which is attributed to thermal expansion mismatch between alumina and nickel. The fracture mode of these composites is mainly an intergranular-type.