机构地区: 中山大学物理科学与工程技术学院物理系
出 处: 《中国有色金属学报》 1996年第3期119-122,共4页
摘 要: 采用惰性气体保护蒸发凝聚技术制备出粒径为4~15nm的稀土金属Gd微粉(nmGd)。经振动样品磁强计测试,表明nmGd微粉在某一特征粒径dc时磁化率χ取得最小值。利用小角X射线散射方法分析了nmGd微粉的三维生长分形特征,表明nmGd微粒聚集体系呈质量分形,制备气压越小则分维系数Df越小。微粒生长模型是扩散限制聚集(DLA)与扩散限制团聚聚集(DLCA)模型共存,相应这两个模型阶段的分维系数Df存在一特征粒径df。根据纳米微粒理论对nmGd微粉体系的量子尺寸效应的特征尺寸dq进行了估算,并就三种特征粒径dc。 Nanometer gadolinium powders (nm Gd) sized 4~15nm have been prepared by means of condensation of evaporating Gd atoms in the atmosphere of inert gas argon. The magnetic susceptibility of nm Gd powders, measured by vibrating samples magnetometer, demonstrates a minimum when the size of nm Gd powder approaches a special value d c . The analysis, based on the measurement of small angle X rays scattering, shows that the as prepared nm Gd powders have a characteristic of mass fractal growth, and that a lower pressure of inert gas results in a small fractal dimension D f. There are two stages corresponding to DLA (Diffusion Limited Aggregation) and DLCA(Diffusion Limited Cluster Aggregation) models in the growing process of nm Gd powders. There exists a special size d f of nm Gd powder about fractal dimension between the two stages mentioned above also. According to the theory of nanometer materials, a calculation evaluating the critical size d q of quantum size effect of metal Gd has been carried out in order to clarify the influence of three special sizes d f, d q and d c on the magnetic susceptibility of nm Gd powders.