A NMR technique for the analysis of pore structure: Numerical inversion of relaxation measurements

摘要: Abstract NMR spin—lattice relaxation measurements of fluids contained in porous solids could be a powerful tool for pore size/structure analysis. It does not suffer from many the inherent disadvantages mercury porosimetry/nitrogen condensation such as necessity shape assumption, measuring only smallest constriction pore, sample compression (porosimetry), and limited size range (condensation). However, successful extraction desired volume distribution experimental requires solution an “ill-posed” problem. A recently developed nonnegatively constrained least-squares (NNLS) algorithm was used to approach this Two methods were including matching data real time using NNLS transforming both governing equations into frequency domain subsequent with NNLS. Numerical experiments conducted artificial generated variety types. The two analyze exact containing 5% random error. Direct analysis more accurate reproducing structures than Fourier transform except limit high noise. Deconvolution structure gave nearly results. Analysis after introducing error yielded less accurate, yet stable Small oscillations calculated distributions noted but these are on same order or smaller those normally encountered porosimetry/condensation experiments.