Preparation and characterization of carbonyl iron/glass composite absorber as matched load for isolator

Abstract

Composite absorbers made from 66wt% carbonyl iron and 34wt% low melting point glass powder were prepared by a pressureless sintering technique in a nitrogen atmosphere. Apparent porosity and bending strength of the as-prepared composites were investigated. The microstructure, heat resisting properties and electromagnetic properties were characterized by scanning electron microscopy, thermal gravimetric analysis–differential scanning calorimetry and vector network analyzer. The results show that the carbonyl iron/glass composite absorbers were difficult to densify. As the sintering temperature and soaking time increased, the apparent porosity first decreased and then increased, whereas the bending strength showed the opposite change. The composite absorber sintered at 520°C for 40min achieved the minimum apparent porosity of 13.08% and the highest bending strength of 52MPa. Compared to the carbonyl iron/silicone rubber absorber, the carbonyl iron/glass composite absorber exhibited better heat resisting properties, and the initial oxidation temperature was increased about 200°C. The composite absorber with a thickness of 1.25mm showed a good microwave absorbing property in 8–12GHz.