Microwave-magnetic field dual-response raspberry-like microspheres for targeted and repeated self-healing from electrical damage of insulating composites

During long-term service, micro-cracks and electric-tree damage inevitably appear in solid insulation materials due to the effects of ambient temperature, humidity, mechanical stress, electromagnetic fields, and so on, leading to premature failure or even explosion of electrical and electronic devices. A timely repair of mechanical and electric-tree damage is, thus, not only urgent but also enormously challenging. This article reports the development of microwave-magnetic field dual-response raspberry-like microspheres (MMDR-RLMSs) for use as targeted and repeatable self-healing agents for insulating composite materials. MMDR-RLMSs are cross-linked with an epoxy resin (EP) matrix to form a thermoplastic-thermoset composite insulating material that provides targeted self-healing of the insulating material to fix cracks and electric-tree damage. In particular, Fe3O4@SiO2 nanoparticles, which have a microwave-magnetic field dual-response function, are coated onto the surface of repair microspheres, which can be targeted to the damage-prone areas of the insulating material under an applied magnetic field. This strategy greatly reduces the doping concentration of repair microspheres and minimizes the negative impact on the intrinsic properties of the EP. The proposed method is an example of a no-shell-type microcapsule self-healing system and offers the advantages of multiple, noncontact, dual-response self-healing functionalities to heal mechanical and electric-tree damage. In contrast to the present microcapsule system, the self-healing function is long term and repeatable, which opens a new route toward self-healing of electrical composite materials.