多元醇法制备CoNi纳米粒子的形成机制,尺寸控制及磁性能

Formation mechanism,size control and magnetic properties of CoNi nanoparticles prepared by polyol method

采用多元醇法在150～190℃合成了CoNi合金纳米粒子,利用SEM-EDX,XRD和VSM对所制备的CoNi纳米粒子形貌、成分、结构以及磁性能进行了研究,并进一步探讨了形核剂K2PtCl4对CoNi纳米粒子形貌及磁性能的影响。结果表明,在180℃用多元醇法制备的Co40Ni60(inat%)纳米粒子为FCC结构,Co2+要易于Ni2+被还原,导致最初10min内合成的CoNi纳米粒子中含有约78%(原子分数)Co,表现为高饱和磁化强度和高矫顽力,随着反应时间的延长,CoNi纳米粒子的Co含量、饱和磁化强度及矫顽力逐步下降。在150～190℃范围内,随着反应温度的提高,Ni2+的被还原能力增强,高温下合成的CoNi纳米粒子具有较低的饱和磁化强度和较小的矫顽力。形核剂K2PtCl4的加入,并不影响CoNi合金纳米粒子的成分和晶体结构。但是,随着形核剂浓度的增加,CoNi纳米粒子平均直径明显减小,其矫顽力有所增大。通过设计形核剂的浓度,CoNi纳米粒子的直径可以在96～580nm范围内任意控制。

The morphology,composition,structure and magnetic properties of CoNi nanopartiles prepared at 150-190℃ for various times have been examined by using scanning electron microscopy assisted with energy dispersive spectropy of X-ray （SEM-EDX）,X-ray diffraction （XRD） and vibrating sample magnetometer （VSM）.The results show that all of the CoNi nanoparticles prepared above are of face centered cubic （FCC） structure.The Co2＋ ions are easier to be reduced than Ni2＋ ions,which results in about 78at%Co in the initial CoNi nanoparticles within 10 min at 180℃ with high saturation magnetization （Ms） and coercivity （Hc）.With prolonging reaction time,the Co content in the CoNi nanoparticles decreases,together with the lower Ms and Hc.The reduction of Ni2＋ ions can be enhanced by increasing temperature in the range of 150-190℃,and the CoNi nanoparticles prepared at higher temperature have low Ms and Hc.With the addition of nucleating agent K2PtCl4,the mean diameter of CoNi nanoparticles decreases rapidly but the Hc increases mildly.The addition of K2PtCl4 does not affect the composition and structure of CoNi nanoparticles,but the particle size can be tunable in the range of 96-580nm with the proper addition of K2PtCl4.The formation mechanism of CoNi nanoparticles has been finally discussed in detail based on the present results.