【摘要】 利用原位XAFS技术研究了在273 K下化学还原法制备Ni70B30纳米非晶态合金的升温晶化过程.结果表明,NiB初始样品中存在Ni和B原子的局部富集,Ni原子的局域结构类似于非晶态Ni,并且Ni原子第一近邻B原子的平均配位数只有0.7左右,远低于其化学计量比7∶3应有的配位数3.6.在升温至498 K时,部分NiB开始晶化生成fcc-Ni;在523~598 K温度范围内,NiB晶化比例随着温度的升高呈线性增加;在温度高于598 K时,NiB纳米非晶态合金的晶化基本完成.更多还原

【Abstract】 In-situ XAFS was used to study the crystallization mechanism of Ni70B30 nano-amorphous alloys prepared by chemical reduction at 273 K.The result indicates that the as-prepared sample is in the state of an amorphous Ni-like structure with nickel-rich and boron-rich regions.The coordination number N in the first shell Ni-B is only 0.7,much less than the value(3.6) predicted by the atomic composition of 7∶3.From the XANES and radial distribution function analyses,crystallization of the as-prepared sample to fcc-Ni starts at the treatment temperature of 498 K and increases with temperature.Above 598 K,the crystallization of Ni70B30 sample has almost finished.Only the phase of crystalline fcc-Ni is formed in the whole thermal treatment process.更多还原