• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Journal of magnetic resonance >Diffusion in porous building materials with high internal magnetic field gradients
【24h】

Diffusion in porous building materials with high internal magnetic field gradients

机译：内部磁场梯度高的多孔建筑材料中的扩散

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Measuring the water diffusivity in porous building materials with NMR is hindered by the presence of large internal magnetic field gradients originating from magnetic impurities (Fe). To investigate the diffusion of water in these materials, a stimulated echo NMR technique is applied. A new analytical equation for the long-time signal decay in the presence of spatially varying internal field gradients is derived. This equation is experimentally confirmed by measurements on representative materials with large internal gradients (fired-clay brick and sintered crushed glass) and a material with very small internal gradients (glass filter). The diffusivity is determined in the long time limit, where it is constant and limited by the tortuosity of the pore structure. Tortuosities of different samples derived from the NMR data show an excellent agreement with the macroscopic tortuosities measured by electrochemical impedance spectroscopy. The developed technique can also be applied in unsaturated media, during e.g., drying, water absorption, and concentration changes. The characteristic length scales of the internal field fluctuations estimated from the model are compared with the structural length scales, whereas the magnitude of these fluctuations is compared with results of macroscopic magnetization measurements.
机译：由于磁性杂质（Fe）产生的内部磁场梯度大，因此无法使用NMR测量多孔建筑材料中的水扩散率。为了研究水在这些材料中的扩散，应用了激发回波NMR技术。推导了在空间变化的内部场梯度存在下长时间信号衰减的新解析方程。通过对具有较大内部梯度的代表性材料（烧结粘土砖和烧结的碎玻璃）和具有非常小的内部梯度的材料（玻璃过滤器）进行测量，可以通过实验确定该方程式。扩散率是在很长的时间范围内确定的，它是恒定的，并受孔结构的曲折性限制。从NMR数据得出的不同样品的曲折度与通过电化学阻抗谱测量的宏观曲折度显示出极好的一致性。所开发的技术还可以应用于例如干燥，吸水和浓度变化期间的不饱和介质中。将模型估算的内部磁场波动的特征长度尺度与结构长度尺度进行比较，而将这些波动的幅度与宏观磁化强度测量结果进行比较。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号