Distributions of transverse relaxation times for soft-solids measured in strongly inhomogeneous magnetic fields.
The single-sided NMR-MOUSE sensor that operates in highly inhomogeneous magnetic fields is used to record a CPMG (1)H transverse relaxation decay by CPMG echo trains for a series of cross-linked natural rubber samples. Effective transverse relaxation rates 1/T(2,short) and 1/T(2,long) were determined by a bi-exponential fit. A linear dependence of transverse relaxation rates on cross-link density is observed for medium to large values of cross-link density. As an alternative to multi-exponential fits the possibility to analyze the dynamics of soft polymer network in terms of multi-exponential decays via the inverse Laplace transformation was studied. The transient regime and the effect of the T(1)/T(2) ratio in inhomogeneous static and radiofrequency magnetic fields on the CPMG decays were studied numerically using a dedicated C++ program to simulate the temporal and spatial dependence of the CPMG response. A correction factor T(2)/T(2,eff) is derived as a function of the T(1)/T(2) ratio from numerical simulations and compared with earlier results from two different well logging devices. High-resolution T(1)-T(2) correlations maps are obtained by two-dimensional Laplace inversion of CPMG detected saturation recovery curves. The T(1)-T(2) experimental correlations maps were corrected for the T(1)/T(2) effect using the derived T(2)/T(2,eff) correction factor.
Chelcea
R I
RI
Technical University of Cluj-Napoca, Daicoviciu 1, R-400020 Cluj-Napoca, Romania.
Fechete
R
R
Culea
E
E
Demco
D E
DE
Blümich
B
B
D003201:Computers; D007089:Image Enhancement; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008280:Magnetics; D008422:Materials Testing / Q000379:methods*; D008853:Microscopy / Q000379:methods; D008962:Models, Theoretical; D012680:Sensitivity and Specificity