Orientation-dependent electromagnetic properties of basalt fibre/nickel core--shell heterostructures

The influence of orientation on electromagnetic properties of basalt fibre/nickel core--shell heterostructures prepared by a simple electroless plating method is investigated. For comparison, the same investigation is also performed on naked basalt fibres. For electromagnetic measurement, the directions of basalt fibre/nickel and naked basalt fibres are parallel, random and perpendicular to the direction of external electric field, termed E_|| sample, random sample and E_⊥ sample, respectively. Electromagnetic anisotropy can be clearly observed in the basalt fibre/nickel core--shell heterostructures, while electromagnetic properties of naked basalt fibres are unrelated to the orientation. The E_⊥ basalt fibre/nickel shows the highest dielectric loss but the lowest magnetic loss, and E_|| basalt fibre/nickel exhibits the highest magnetic loss but the lowest dielectric loss. The dielectric loss of E_⊥ basalt fibre/nickel is several times as large as that of E_|| basalt fibre/nickel, which could be attributed to the increase of polarization relaxation time as a consequence of the nanosize-confinement effect. The magnetic loss of E_|| basalt fibre/nickel is even one order of magnitude higher than that of E_⊥ basalt fibre/nickel, which originates mainly from the natural magnetic resonance of basalt fibre/nickel core--shell heterostructures.