Structural Transformation of Bilayer Ferro-Foams Caused by Magnetic Field
Previous researchers have proved that units constituting monodisperse bilayer foams can transform reversibly by changing foam liquid fraction. Structural transformation of bilayer ferro-foams caused by magnetic field is investigated in this paper. It is observed that bilayer ferro-foams transform from Tóth structure to honeycomb structure caused by liquid fraction change which attributes to foam imbibition under a uniform magnetic gradient field. In order to acquire critical structural transformation liquid fraction range, foam liquid fractions are calculated by image analysis. However, we also observed that, when applying a homogeneous magnetic field, bilayer ferro-foams can also perform this transformation at a constant liquid fraction. This phenomenon is related to energy absorption of foam system, which is induced by magnetic interaction of magnetic moments after applying a magnetic field. This self-organizational behavior of foam structure is believed to be based on energy minimization principle. This study opens possible applications in the field of metal foam preparation.