Applications of NMR imaging in materials science

NMR Imaging or Magnetic Resonance Imaging (MRI) is applied as a nondestructive evaluation technique for visualization of internal structure of complex materials. The materials studied were porous glasses, reinforced elastomers, polymeric composites and v-belts. The structural details include dispersion of fillers, defects, inclusions, laminations and reinforcing fibers.; Experiments were performed on water-filled porous glass cylinders with different porosities. MR images obtained were used to study permeation of water in these materials. Defects in these glasses are studied in the MR images. The results of relaxation measurements of water in filled silicate glasses show a decrease in T{dollar}sb1{dollar} with decreasing pore size.; MRI was applied to study model elastomeric systems. A crosslinked polydimethylsiloxane rubber system with and without fillers was studied. The fillers used were carbon black and zinc oxide. The images present information of filler dispersion and homogeneity of mixing. Defects such as cracks, air bubbles and filler agglomerates were also observed.; Styrene-butadiene rubber (SBR) containing varying concentrations of carbon black filler was studied using MRI and solid-state NMR. It is seen that the image intensity decreases with the filler loading. Factors which contribute to changes in intensity can arise from changes in motion due to differences in free volume and/or elastomer/filler interactions in addition to variation in the rubber/filler ratio. Solid state NMR experiments were performed on the same materials. Cross-polarization magic angle spinning (CPMAS) experiments were performed. The laboratory and rotating frame spin-lattice (T{dollar}sb1{dollar}, T{dollar}sb{lcub}1rho{rcub}{dollar}) relaxations times are not affected due to increasing filler loading. However, the cross polarization time constant (T{dollar}sb{lcub}rm CH{rcub}{dollar}), measured by inversion recovery cross-polarization (IRCP), shows a dependence on the filler loading.; Fiber-reinforced elastomeric v-belts were studied utilizing MRI. Samples were investigated for differences in the belt construction and composition. Images provide detailed information on the construction of the belts. The orientation and the positions of the fibers and also the component layers of the belts are visible in the images. X-Ray CT (Computed Tomography) experiments were also performed on the belts.; The ability of MRI to non-destructively acquire 3-D spatial information was utilized to display three dimensional images from 2-D data sets. 3-D rendering of these data sets was investigated to display materials images. These image processing techniques were applied to visualize structural features or defects in phantoms which model material systems. Phantoms included silica glass cylinders and silicon rubber castings with different fillers and modeled inclusive defects.