纳米Ni颗粒的化学合成与表征

Synthesis and Characterization of Ni Nanoparticles

利用溶胶凝胶法制备前驱体,在惰性气氛中进行热处理,合成了立方结构的纳米Ni粉末,晶粒尺寸范围从15到110nm,分别用差热分析仪(TG-DTA),X射线衍射仪(XRD)、振动样品磁强计(VSM)、透射电镜(TEM)等测试手段对样品的反应过程、形貌结构和磁学性质进行表征测试。结果表明,随着热处理温度的升高,纳米镍粉的晶粒尺寸会逐渐增大,并发现了晶格收缩现象,比饱和磁化强度(Ms)随着粒径的减小而减小;而矫顽力(Hc)在粒径尺寸大于单畴临界尺寸时随着粒径的减小而增大,当粒径尺寸减小到单畴临界尺寸以下时矫顽力(Hc)又逐渐减小。

The face--centered cubic Ni nanoparticles with grain sizes ranging from 15 to 110 nm have been synthesized using heat--treating technique with the precursors prepared by sol--gel method at different temperatures in argon atmosphere. The synthesis condition, structure, morphology and magnetic properties of the samples are studied by using thermogravimetric analysis （TG） , differential thermal analysis （DTA）, x- ray diffraction （XRD）, vibrating sample magnetometer （VSM） and transmission electron microscopy（TEM） respectively. The results indicate that the grain size becomes larger with growth of temperature, and we find the lattice contraction of the nanometer powders. The saturation magnetization （Ms） decreases with decrease of the grain size. However, the coercivity （Hc） increases with the reduction of grain size when the grain size is bigger than the single domain critical dimension. The value of the coercivity decreases when the grain size becomes less than single domain critical dimension.