Effects of heat treatment on magnetic properties of Co-Fe-plated hollow ceramic microspheres

Functional hollow ceramic microspheres plated with Co-Fe were obtained through electroless plating technique for the application of lightweight microwave absorbers. They were treated at different temperatures by vacuum annealing method. The surface-coated hollow microspheres were characterized by scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). The microwave electromagnetic loss and absorbing properties of hollow microspheres plated with Co-Fe were tested by network vector analysis. The magnetic properties were tested by vibrating sample magnetometer (VSM). The results show that the annealing treatment changed the crystal phase of Co from HCP to FCC, simultaneously increased the crystallinity and crystal size of Co and Fe in coating layers. Additionally, after annealing at 800 °C or 1 000 °C, the microwave absorbing properties and soft magnetic properties of hollow microspheres plated with Co-Fe were further improved.