Three-dimensional electron paramagnetic resonance imaging technique for mapping porosity in ceramics

This paper reports on a three-dimensional (3D) electron paramagnetic resonance imaging (EPRI) method which was developed to probe the structure and size of pores in ceramic materials. The imaging device that was added to the EPR instrument consisted of a computer-controlled current source and magnetic field gradient. This add-on facility was tested using a well-defined diphenlpicrylhydrazzyl phantom sample. Pumice was then used to demonstrate the potential of the technique. This stone was immersed in a 0.5 mm 15N-substituted per-deutereted tempone water solution to fill the pores with spin labels. Images were reconstructed using a filtered back-projection technique. A two-dimensional (2D) imaging plane was constructed by collecting 33 projection planes over 180 degrees. A 3D image was derived from 22 planes each constructed by 22 projections. At present, the facility allows a resolution of 69 and 46 μm for 2D and 3D imaging, respectively. Advancements of the imaging apparatus, software, and line width of the spin labels will be needed to enhance the resolution of this technique