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中子散射技术在纳米材料结构表征中的应用
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摘要
中子散射具有许多显著的优点。首先中子直接作用于原子核,所以中子的穿透能力远强于激光和X射线适合于研究浓溶液、甚至物质本体的结构;其次,原子核对中子散射能力的强弱不是由原子序数的高低决定,而是一种非常无规的分布,这就使得中子散射在软物质材料结构研究中具有广阔的应用前景:由于氢(H)和氘(D)对中子的散射长度具有非常大得不同(b_H=-3.74×10~(-13)cm,b_D=6.67×10~(-13)cm),我们可以用衬度匹配的方法来选择性观察我们想要观测的物体结构;再次中子的波长为0.1-3纳米,与X射线相当,但是,由于中子本身具有质量,所以用X射线测量物质结构将产生的热效应和分解效应,在中子技术中都不复存在;最后,联用中子衍射、小角中子散射、超小角中子散射,我们可以测量非常宽的尺寸范围:0.01?到30μm。本文将先简略介绍中国散裂中子源,然后以小角中子散射技术为例,具体介绍小角中子散射技术在纳米粒子结构表征、生物样品结构测量、凝胶内部纳米结构分析、聚合物太阳电池结构观测方面的应用。
Neutron scattering is a powerful tool to explore multi-scale structures from 0.01 ? to 30μm. First, neutron interacts with nucleus rather than electron clouds, so it is sensitive to light elements and isotopes(complementary to X-ray which is sensitive to elements with high molar mass). Second, the small scattering cross-section of most elements makes it easy for neutrons to penetration centimeters into materials, thus complicated sample environment and time resolved observations are possible in neutron scattering experiment. Third, thermal and cold neutrons bear much less energy than X-ray with the same wavelength, so there are no heat and decomposition effects to the sample in neutron scattering, which is very important in biology. The manuscript will focus on the applications of neutron scattering in material, Bio-physics and nano-science.
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