【摘要】 采用原子配位分布函数为Gaussian函数PG 和指数函数PE 直积的非对称模型进行拟合计算 ,XAFS定量地研究化学还原法制备的Ni P和Ni Ce P超细非晶合金大无序度体系中Ni原子的局域环境结构随退火温度升高而产生的变化 .结果表明Ni P和Ni Ce P原样的Ni Ni配位的平均键长Rj、配位数N、热无序度σT、结构无序度σS 分别为 0 2 71nm ,10 0 ,0 0 0 6 0nm ,0 0 2 8nm和 0 2 71nm ,10 6 ,0 0 0 70nm ,0 0 30nm ,其结构无序度很大 ,为热无序度的 40 0 %左右 .在 5 73K退火后 ,Ni P样品已产生晶化 ,但Ni Ce P样品的晶化温度升高 10 0K左右 ,表明加入 2 %原子比的Ce能明显增加Ni P超细非晶合金的热稳定性 .在 773K退火后 ,Ni P和Ni Ce P样品晶化都近于完全且Ni Ni配位有相同的结构参数 ,其径向结构函数形状与Ni箔的类似 ,但Ni Ni配位的结构无序度为 0 0 11nm ,说明晶化后生成的金属Ni的晶格参数受P的影响产生很大的畸变 .更多还原

【Abstract】 XAFS technique has been used to quantitatively determine the local structure evolutions of ultrafine Ni\|P and Ni\|Ce\|P amorphous alloys prepared by chemical reduction during the annealing process.Using an asymmetric atom distribution function model of convolution of a Gaussian function P \-G and an exponential function P \-E for XAFS data analysis,we obtained that the average bond length R j,coordination N ,thermal disorder factor σ T,and static disorder factor σ S for the Ni\|Ni first neighbor shell are 0.271?nm,10.0,0.0060?nm and 0.028?nm in the Ni\|P and 0.271nm,10.6,0.0070?nm and 0.030?nm in the Ni\|Ce\|P initial samples,respectively.It indicates that the σ S is rather large and about three times larger than that of σ T.The Ni\|P sample crystallized under the annealing temperature of 573?K,while the crystallizing temperature of Ni\|Ce\|P sample is about 100?K higher.The result suggests that the thermal stability of Ni\|Ce\|P sample is significantly increased by the addition of 2% Ce element.After being annealed at 773?K,both Ni\|P and Ni\|Ce\|P samples are fully crystallized as metallic Ni and an amount of crystalline Ni\-3P.Furthermore,we have found that the static disorder σ s of Ni\|Ni coordination shell is 0.011?nm for the Ni\|P and still larger for the Ni\|Ce\|P samples annealed at 773?K,despite their radial distribution functions around Ni atoms are similar to that of Ni foil.It implies that the Ni lattice obtained from the crystallized Ni\|P and Ni\|Ce\|P amorphous alloys is significantly distorted by the interaction of P element.更多还原