Evaluation of a magnetic dispersion by interparticle interactions

The magnetic, theological and electrical effects of interparticle interactions in a metal particle dispersion have been investigated experimentally with the aim of understanding the state of the dispersion through such interactions. Samples of different degrees of dispersion were obtained by varying the duration of a sand milling operation. The magnetic interactions were assessed from the hysteresis and remanence curves of frozen dispersion samples. The coercivity and remanence coercivity of the dispersion samples were found to increase with increasing milling time, while the switching field distribution calculated from both the hysteresis and remanence curves decreased. The first normal stress difference, N-1, of the dispersion was measured as a theological indicator of magnetic interactions. N-1 decreased with increasing milling time. The dielectric constant and the ac conductivity were investigated for possible electrical particle interactions. Both parameters decreased with increasing milling time, but the results were found to be due to polymer-particle rather than particle-particle interactions.