Relaxometry

A carefully chosen set of experimental techniques applied to porous media characterization provides results that can be much greater than the sum of the individual parts. The inter-relation and complementarity of a number of techniques will be considered. NMR cryoporometry provides a valuable method of pore size measurement. An NMR method that is more widely used to assess pore dimensions relies on relaxation time analysis of a liquid that fills the pores and the enhanced relaxation that occurs in a liquid at the solid/liquid interface.
Thermoporometry, a method based on the application of Differential Scanning Calorimetry (DSC), is closely related to cryoporometry, but employs a different set of assumptions to evaluate pore size distributions. Comparison of the results obtained on the same samples using all these methods together with gas adsorption serves to validate the methods and provide significantly more information about surface-fluid interaction and the behavior of nano-scale material within pores than each method employed in isolation. Technique developments will be discussed and applications of these methods to ideal silicas will be used to illustrate their power, particularly in combination. © 2003
Elsevier Science Inc. All rights reserved.
Keywords: Porous media; Nuclear magnetic resonance; Cryoporometry; Relaxometry

The effect of pre-treatment of low grade waste clay on the disposition of the water in clay based geopolymer has been investigated. The condition of the clay was untreated, calcined, and mechanically activated. Two different curing conditions were applied: ambient curing over 24 h and 120 C over a 6 h. Time-domain NMR, FTIR, and EDS were used to study the water disposition in the clay-based geopolymer. Geopolymers cured under ambient conditions demonstrated no discernible change in the water interactions due to insufficient heat during curing to trigger the polycondensation. Time-domain NMR revealed that for the geopolymers heat-cured at 120 C, the water component becomes more strongly bound with increasing curing time. The mechanically-activated system showed the strongest water bond compared to the calcined and untreated systems. FTIR results indicate that the intensity of the vibrational band arising from the structural water at 3620 cm-1 increases with increasing curing.

Oxygen-sensitive F-19 magnetic resonance imaging of perfluorocarbon compounds requires that fluorocarbon T1 changes correlate with the local PO2 and not with the composition of the surrounding aqueous phase. The influence of various bioconstituents and paramagnetic ions within the aqueous phase on the F-19 fluorocarbon phase T1 for PFC emulsions was evaluated at 0.14 and 0.66 T. T1 was measured for FC-43, perflubron, and a fluorinated surfactant. Controlled variables introduced in the aqueous phase included annex solution constituents, blood, pH changes, and Gd-DTPA. For a constant PO2, the F-19 T1s were independent of the emulsion constituents, blood concentration, and pH. For FC-43 and perflubron, F-19 T1 was independent of the Gd-DTPA concentration, while the aqueous phase T1 decreased by more than an order of magnitude. XMO-10 (smallest emulsion particle size) showed a slight decrease in F-19 T1 with increasing Gd-DTPA concentration at 0.66 T.