Magnetic filtration of ferrofluids

Abstract

We have used a modified HGMS apparatus to selectively filter aggregated particles from samples of ferrofluid. We have identified the reduced initial susceptibility <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\bar{X_{i}} (=[dI/dH]/I_{S})</tex> as a quality control parameter for fluid stability to field gradients. We show that <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\bar{X_{i}}</tex> is a far more sensitive measure than particle sizing techniques which are insensitive to the presence of aggregates.