微乳液体系中Ni-La-B非晶态合金纳米团簇的制备及退火晶化

Preparation and Annealing Crystallization of Ni-La-B Amorphous Alloy Nanoclusters by W/O Microemulsion

在W/O型反相微乳液体系中,以KBH4为还原剂制得近乎单分散的Ni-La-B非晶态合金纳米团簇。采用扫描电子显微镜、透射电子显微镜、X射线衍射、差示扫描量热仪和X射线光电子能谱(XPS)等测试技术对样品进行了表征。结果表明,团簇呈球形,尺寸为10～15nm,分布较均匀,基本呈单分散。升温速率为20K/min时,DSC曲线在657.6和724.3K处出现2个强放热峰,其晶化温度明显高于水溶液体系以KBH4为还原剂制备的Ni-B非晶态合金纳米颗粒,表明样品具有良好的热稳定性。X射线衍射测试鉴识出DSC曲线揭示的2个相转变过程,Ni-La-B非晶态合金晶化成Ni-La-B晶态合金和Ni-La-B晶态合金转化成纳米晶Ni-La和单质B。相转变活化能的测定表明,后1个晶态合金的相转变过程的速率比前1个非晶态合金的快。

The nearly monodispersed Ni-La-B amorphous alloy nanocluster was prepared from the reduced reaction of Ni（Ac）2 and La（NO3）3 by KBH4 in W/O microemulsion. Samples were characterized by SEM, TEM, XRD, DSC and XPS. The results show that the sample exhibits a spherical morphology with a size of around 10 - 15 nm and an even size distribution. The DSC curves show that there are exothermic peaks corresponding to phase transition at 657.6 K and 724. 3 K at a heating rate of 20 K/min. The crystallization temperature of the sample is significantly higher than that of the nano Ni-B amorphous alloy powder obtained by chemical reduction with KBH4 in aqueous solution. Thus, the Ni-La-B amorphous alloy nanocluster prepared by microemulsion method has excellent thermal stability. The XRD results identify the two phase transition steps as determined by DSC analysis： one is the transformation of Ni-La-B amorphous alloy into Ni-La-B crystalline alloy, the other is the decomposition of Ni-La-B crystalline alloy into Ni-La crystalline alloy and release of B. The rate of the latter is higher than that of the former, which has been found via determining phase transition activation energy.