Effect of liquid-solid ratio on the morphology, structure, conductivity, and electromagnetic characteristics of iron particles

Using a ball-milling technique, polymorphous iron particles were prepared by changing only the liquid-solid ratio λ. Effects of λ on their morphology, structure, conductivity, and electromagnetic properties were studied. The results show that an increase of λ from 0 to 0.25 causes a nonlinear decrease of the conductivity in the ranges of 88.50–2.25 S cm−1 and a regular variation of the electromagnetic parameters, corresponding to the as-obtained iron particles. This is ascribed to a combination of the increased shape anisotropy and the decreased fresh surface with active atoms deriving from the weakened welding-on action and the enhanced micro-malleation action in the ball-milling process. Hereinto, the iron flakes formed at wet-milling with λ=0.08−0.25 have lower conductivity, higher permittivity and permeability, and more excellent absorption property compared with the irregular iron particles obtained at dry-milling with λ=0. It is a consequence of the synergistic effect of dielectric relaxation loss, exchange energy and conductance loss originating from the flake-shape structures. This indicates that the morphology, structure, conductivity, and electromagnetic properties of the products can be effectively controlled by changing λ.