摘要:
准弹性中子散射(quasi-elastic neutron scattering, QENS)实验是研究水泥老化过程中水动态的一种新颖的实验方法。本文利用老化时间分别为7,14和30 d水泥样品的QENS谱实验数据,通过应用四个高斯项的和的能量分辨函数R(Q, E)代替一个高斯项的能量分辨函数来改进经验扩散模型(empirical diffusion model, EDM),再进行非线性最小二乘拟合。由此导出水泥样品中水动态的相关物理参数：不动水数密度A,自由水指数FWI=B1/(A+B1+B2),洛伦兹函数的半高宽Γ,移动水跳跃之间的平均停留时间τ0及自扩散系数Dt,而且可得出更为精准的QENS谱拟合曲线。拟合得到的物理参数可定量描述水泥老化过程中水动态过程,从而为QENS实验在水泥老化过程中水动态研究的应用提供一种合理实用的谱分析方法。
Abstract:
Quasi-elastic neutron scattering (QENS) is a novel experimental technique for studying the translational dynamics of water in cement paste. In our work, the improved empirical diffusion model has been used to the nonlinear least square fit of the QENS experimental data of cement samples cured for 7, 14 and 30 days, where an energy resolution function R(Q, E) of four Gaussian terms instead of one Gaussian term is utilized during the fitting process. Parameters of the translational dynamics of water in cement paste have been deduced: the number density of immobile water A, the free water index FWI=B1/(A+B1+B2), the full width half maximum of Lorentzian functionΓ, the average residence timeτ0 between jumps and the self-diffusion coe?cient Dt of mobile water. Fitted QENS spectra are more accurate and the dynamics of water in cement paste can be quantitatively explained with these deduced parameters.All this provides a practical and useful method for spectral analysis of QENS on translational dynamics of water in cement.
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