Green foams for microwave absorbing applications: Synthesis and characterization

International audience; This study deals with the dielectric properties of recycled glass foams and their use as microwave absorbers. Glass wastes from Cathode Ray Tube have been used to produce foams by heating a mixture consisting of glass cullet and foaming agents (carbon or a combination of carbon, TiO2, MnO2 and AlN). As only part of the carbon introduced into the initial load oxidizes and contributes to the foaming process, the residual fraction acts as an electromagnetic absorber. The effect of the carbon load rate on the foams density and microwave properties was studied. These materials present a low permittivity and high dielectric losses in X-band. Foams density mainly controls the dielectric properties. Carbon-based glass foams show a great potential as microwave absorbers with a shielding effectiveness of 20 dB/cm at 12 GHz. Moreover, a tradeoff between the density and shielding efficiency can be achieved by controlling the load rate of carbon.