准弹性中子散射(QENS)在受限水动态研究中的应用

Application of quasi-elastic neutron scattering to dynamics study of confined water

准弹性中子散射(Quasi-elastic neutron scattering,QENS)实验是研究受限水动态的一种重要实验手段。水泥样品中存在有结合水和受限水,各自的含量随着水泥样品的老化时间、环境温度、水和水泥(w/c)质量比、添加剂等因素的不同而变化,处于强受限状态的水的动态特性影响着水泥石的耐久性和力学特性,因此,水泥样品中受限水动态的研究具有重要的意义。本文综述了近年来水泥样品中受限移动水含量比例和受限水动态的QENS实验研究,着重介绍采用弛豫盒子模型(Relaxing cage model,RCM),对QENS谱实验数据的拟合分析,得到描述水泥样品中受限水动态相关信息的关键物理参数:受限移动水比例系数1-p,微纳孔中受限水分子在某位置上的诱捕(俘获)时间?0、受限水平均迁移弛豫时间<?>及其自扩散系数D,表征水泥样品微纳孔均匀性的形状因子?等,为QENS实验在受限水动态研究中的应用提供一种合理实用的方法。

Background： Quasi-elastic neutron scattering （QENS） is an important experiment for dynamics study of confined water. It is significant to study the dynamics of confined water in cement paste. Purpose： In this paper, we have two aims. One is to present a reviewer of QENS study on dynamics of confined water in cement paste in recent years. The other is to illustrate the QENS application to the study on dynamics of confined water based on cement paste. Method： Relaxing cage model （RCM） is specially introduced for the analyses of QENS spectra. Results： Based on RCM, several parameters for describing the dynamics of confined water in cement paste, can be obtained from the analyses of QENS spectra： a fraction of mobile ＇glassy＇ water molecules embedded in amorphous gel region surrounding the hydration products, l-p, the capture time of confined water molecule in some place-ι0, the average translational relaxation time-〈r〉, the self-diffusion coefficient-D, and a phenomenologieal shape parameter describing the uniform of amorphous in cement paste-β. Conclusion： All these provide a practical method for QENS study on dynamics of confined water in cement paste.