NMR IMAGING OF PASTES IN A RAM EXTRUDER

Nuclear magnetic resonance (NMR) imaging was used to investigate the e xtrusion behaviour of pastes with a ram extruder. Extrusions of limest one pastes with moisture contents of 23-29% nd pastes of an oxide cera mic (Pural) with moisture contents of 72-76% have shown that NMR is a suitable method for the detection and quantification of structural cha nges and flow processes in pastes, e.g. the relative motion between th e liquid and the solid phases, the beginning and time-dependent develo pment of fissures within the cylinder filling and the extrudate, pepti zation and agglomeration. With NMR one can distinguish between free an d bound water and determine the spatial distribution of the respective fractions of a phase within a specific volume element. Furthermore th e time- and location-dependent displacement profiles of the solid and the liquid can be observed.