A review of metal oxide-related microwave absorbing materials from the dimension and morphology perspective

Various wireless devices have been widely used in every aspect of life and further lead to the severe electromagnetic waves pollution. Fortunately, researchers have developed microwave absorbing materials which are able to transfer the harmful electromagnetic waves into other energy, such as thermal energy. In recent years, numerous studies on preparing microwave absorbing materials with various components, morphologies and structures have been reported. Metal oxide-related composites are widely used as microwave absorbers due to their excellent electromagnetic properties. The morphology and nanostructure would play a key role on the microwave absorbing performances, which can cause "structural effect". The ideal microwave absorbing materials should meet following demands: widely effective absorption frequency (f_E), thinner thickness (d), light-weight, and strong absorption. In this review, we summarized various common morphologies and structures of metal oxide/metal oxide-based composites, and categorized them from a dimensional perspective. The different microwave absorbing properties and mechanisms are given much attention in detail.