Study On Microwave Absorption Properties Of Metal Reinforced Foam Glass Matrix Composite

In this paper, microwave absorbing composites were prepared by adding cobalt, nickel and copper metal filler into foam glass as a matrix. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were used to characterize pore structure and constituents of samples. Complex permittivity and permeability of composites were measured by wave guide method in X-band (8.2—12.4GHz) and reflection loss was calculated based on permittivity and permeability.Results indicate that: Real part of complex permittivity for foam glass with 2wt % graphite declined from 3.25 to 3 with frequency, as well as imaginary part decreased from 1.3 to 1; Real part of complex permeability lied between 0.96 and 1.07, while imaginary part varied from 0.02 to 0.13. Reflection loss of foam glass less than -2dB was obtained in all X-band and the minimum reflectivity was -6dB at 12.4GHz with a thickness of 3mm.The cobalt-containing foam glass with low metal powder additive had low density and high porosity. When the mass ratio of metal filler to foam glass is larger than 3:20, porosity of composite decreased rapidly with metal powder additive, while density increased. As mass ratio increased, real part of permittivity of composites varied from 4.5 to 50; Imaginary part increased from 2.7 to 50 with mass ratio; Both real part and imaginary part increased rapidly when mass ratio was larger than 5:20. Real part of permeability for composites lied between 0.95 and 1.1; Imaginary part increased with mass ratio and the values ranged from 0.02 to 0.32. Reflection loss values of Co3 sample (mass ratio of cobalt powder to foam glass was 3:20) less than -11dB were obtained in all X-band and a minimum reflectivity of -15.1dB was observed at 9.6GHz with a thickness of 3.5mm.Nickel-containing foam glass (nickel filler to foam glass ratio was 1:20) had a reflection loss below-10 dB in the range of 9.5—11GHz with a thickness of 4mm. Copper-containing foam glass (mass ratio of copper powder to foam glass was 4:20) achieved a reflectivity less than -10dB in the range of 8.3—10.8GHz with a thickness of 4mm.Microwave absorption of foam glass matrix composite was mainly from dielectric loss. Adding metal filler into foam glass could enhance dielectric loss of glass matrix and benefit impendence match between glass matrix and air, therefore microwave absorbing properties of composite was improved.