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An attempt for formulating techniques of measuring sub-nanometer vacancies using positronium

尝试制定使用正电子测量亚纳米空位的技术

基本信息

批准号：
10450316
负责人：
ITO Yasuo
金额：
$ 3.39万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-10450316/
关键词：
Positron annihilation Positronium Polymers Free Volume Xe-129 NMR polyimide gas sorption sorption polyimide positronium lifetime free volume neutron diffraction polytetrafIuoroethyIene positronium Iifetime ^<129>Xe NMR revers

项目摘要

It is becoming possible to estimate the size and number of free volume holes in insulating materials from positron lifetime measurements. Since the related physical quantities, the lifetime τ_3 and the intensity l_3 of the o-Ps component, are not the direct measure of the free volume quantities, it is imperative to work out a connection between τ_3 and the free volume size, and between l_3 and the number of them. For this purpose we have performed the following investigations ;1) The relationships between o-Ps parameters and free volume characteristics are summarized.It has been made clear that Ps seeks larger holes and/or dig holes (makes the hole size lager).The extent of making the hole size larger has been found to be approximately 20% in plasticized conditions. In glassy polymers, however, the extent will not be as large as this.O-Ps intensity l_3 is not always the measure of the number of the free volumes.2) The o-Ps method has been compared with other techniques of free volume determination. Chemical shift Xe-129 showed particularly excellent correlation with τ_3, which served as the standard for calibration of the chemical shift technique.3) The Ps method of measuring the free volumes has been applied to some practical cases.The chanse of free volume states after sorbing external molecules (propylene) was measured for several polyimides using the Ps method.The free volume structure of reverse osmosis membranes was measured.

通过正电子寿命测量来估计绝缘材料中自由体积孔的尺寸和数量已经成为可能。由于相关物理量τ_3和o-Ps分量的强度l_3并不是自由体积量的直接量度，因此必须建立τ_3与自由体积大小、l_3与它们的数量之间的联系。为此，我们进行了以下研究；1）总结了o-Ps参数与自由体积特性之间的关系。已经明确Ps寻求更大的孔和/或挖孔（使孔尺寸更大）。已发现在塑性条件下使孔尺寸变大的程度约为20%。然而，在玻璃态聚合物中，程度不会这么大。O-Ps 强度 l_3 并不总是自由体积数量的度量。2) o-Ps 方法与其他自由体积测定技术进行了比较。化学位移Xe-129与τ_3表现出特别好的相关性，作为化学位移技术的校准标准。3）Ps法测量自由体积已应用于一些实际案例。利用Ps法测量了几种聚酰亚胺吸附外部分子（丙烯）后自由体积状态的变化。测量了反渗透膜的自由体积结构。