Magnetic Properties of Ferrofluid Change Over Time: Implications for Magnetic Pore Fabric Studies

The anisotropy of magnetic susceptibility ferrofluid-impregnated samples is an efficient and powerful proxy for pore space preferred flow directions. One the main assumptions in fabric studies that all pores >10–20 nm are homogeneously filled with ferrofluid, ferrofluid has constant properties throughout over time. If only part filled, this can lead to artifacts. Additionally, because a given depends on fluid susceptibility, quantitative interpretations may be affected by interval between impregnation measurement time, or age during impregnation, unless remain constant. A careful investigation time variation fabrics synthetic natural shows time-dependence hysteresis properties, related dissolution particle surfactants, deterioration colloidal stability. latter leads aggregation sedimentation, which changes also affects behavior. Natural impregnated oil-based experience 2.5–3-fold increase mean important consequences susceptibility-based determination efficiency. Based our results, we recommend determined at measured shortly after impregnation.