Influence of heat treatment temperature on the crystal structure and electromagnetic properties of Co-plated hollow glass microspheres

Co-plated hollow glass microspheres acquired by electroless plating method were treated at different temperature, then its surface morphology, crystal structure, electromagnetic parameters, absorbing properties and the magnetic properties were studied. The results showed that with the rise of heat treatment temperature, the coatings have been through micro-melting until the more serious melting and coating spalling; HCP to FCC of Co transition occurred in the coating and the extent becomes larger. Heat treat temperature has significant influence on the permittivity of Co-plated microspheres but little influence on its permeability. The permittivity of Co-plated microspheres with 800 and 1000°C rose by a large scale while the permeability changed little in 2-18 GHz frequency band, thus, the reflectivity reduced dramatically. The coercive of Co-plated microspheres becomes smaller with the rise of temperature, and its hysteresis loss decreased slightly after heat treatment. It can be predicted that the absorbing properties of Co-plated microspheres with 800 and 1000°C heat treatment will be greatly improved.