Design And Microwave Absorbing Property Of Foam Glass Matrix Composite

Main object of this study was to study the microwave absorption of foam glass in which Zn and MnO₂ was added to raw materials, which provided experimental data and theoretical basis for obtaining foam glass with strong microwave absorption.Series of foam glass specimens were fabricated by sintering mixture of SiO₂, H₃BO₃, ROH, Al₂O₃, graphite and additive (Zn and MnO₂). Investigation on the change rate of diameter of cylindrical glass body (r) fired at different temperatures was carried out to determine the optimum value of r corresponding to foaming temperature. XRD was utilized to analyze compositions. Foam microstructure and ZnO morphology were recorded by SEM. Microwave reflectivity in X-band was calculated based on permittivity which was tested through wave guide method.With the increase of graphite content, foam distribution became inhomogeneous, which could be improved by prolonging milling time properly. Foam glass sintered at 750℃with more than 3.85wt% graphite added into mixture did not foamed because additive of graphite increased the melting temperature of batch. The microwave absorption of foam glass without Zn was weak with minimum reflection of ?0.3dB.The pore size and porosity decreased with the increased content of zinc. The oxidation of Zn led to the production of ZnO whisker and nanocrystal on bubble walls of foam glass. The morphology of ZnO was determined by the supersaturation of ZnO(g) related to content of graphite and Zn, and the relationship was illustrated in a diagram. Quantity of ZnO nanocrystal increased with the increase of Zn content from 5.26wt% to 21.74wt%, while length of ZnO whisker got shorter and diameter got bigger. while the Zn content was fixed at 5.66wt%, increase of graphite content resulted in decreased supersaturation and shorter ZnO whisker. The property of microwave absorption was related to the content of graphite and Zn. When content of graphite and Zn were 1.96wt% and 14.3wt%, respectively, the minimum microwave reflection of foam glass/ZnO was ?16dB, and the effective bandwidth was 1.1GHz.With the increase of MnO2 content, the pore size, porosity and diameter of ZnO rod in foam glass increased, and microwave absorption also increased. When 5.66wt% MnO₂ and 10wt% Zn were added, the minimum and maximum reflection of specimen were ?12dB and ?7dB, respectively, and available bandwidth was 1.7GHz(8.9-10.6GHz), which would be prospective microwave absorber.