A Low-Cost Low-Field Nuclear Magnetic Resonance Cryoporometry System for Nanopore Size Measurement

Nanopore size measurement is of great significance to understand the physical and chemical properties of porous media. In this article, a low-cost low-field nuclear magnetic resonance (NMR) cryoporometry system was developed. A low-field cryogenic NMR probe was first designed, where the sample in the chamber could be cooled to the object temperature accurately by automatically controlling the spraying rate of liquid nitrogen during the signals measured by the home-built low-field NMR system. Experiments were then undertaken to obtain the freezing point temperatures of CaCl2 solutions with different concentrations. The comparison with the theoretical values shows the proposed low-field NMR cryoporometry system has the ability to precisely control the temperature of samples. Furthermore, the system developed in this article was applied to measure three molecular sieves and the experimental results are consistent with the known pore size distribution, which proves the accuracy of the developed system for the measurement of the nanopore porous medium. In conclusion, the low-field NMR cryoporometry system developed in this article provides a low-cost solution to the nondestructive and accurate characterization of nanopore size of porous materials.

Automated summary

In this article, a low-cost low-field nuclear magnetic resonance (NMR) cryoporometry system was developed to accurately measure the nanopore size of porous materials. The experimental results show that the proposed system has the ability to precisely control the temperature of samples and provide consistent measurements with known pore size distribution.