Applications of Earth's Field NMR to porous systems and polymer gels

Abstract

NMR relaxometry in the Earth's magnetic field is used to characterize porous systems and polymer gels. The used instrument is a home built Earth's field NMR (EFNMR) device equipped with some unique features such as first order gradiometer polarization and detection coils, shimming coils and a shielding box that make it possible to directly derive the relaxation times from the free induction decay signal inside a laboratory building with a signal to noise ratio of about 100. Different kinds of experiments show the dexterity of the EFNMR device in a broad range of applications. By analyzing the signal amplitude, information such as water content, water distribution or drying behavior of different kind of samples is obtained. From the analysis of the relaxation times, information about the environment of the protons is derived. In this way, the pore size distribution of porous materials and the polymerization characteristics of polymer gels containing water is obtained.