Shunhua Liu

A Discrete Slab Absorber: Absorption Efficiency and Theory Analysis

Slab absorber is an important topic not only for military purposes but also for commercial application. Single-layer compact slab absorber cannot meet the required wave absorption in broad wave band besides some absorption peaks, and it is very necessary to develop a new kind of absorber to meet the need of absorption in broad wave band. In this study, a discrete slab absorber (DSA) has been developed by isolating conductive medium in absorbing matrix, and the reflection loss test indicates that the DSA exhibited excellent absorption effectiveness at 8-18 GHz. With the increasing carbon black (CB) content of the isolated conductive particles in the slab absorber, the reflection loss increases in the range 8-18 GHz. When mass fraction of CB gets to 30%, the reflection loss is below 10 dB in the range 8.5-18 GHz, and the effective absorption band below 10 dB gets to 9 GHz. In comparison, the compact slab sample with 30 mass% CB only shows two absorption peaks and the effective absorption band below 10 dB is under 1 GHz. Finally, an absorption mechanism is suggested.

Electromagnetic characteristics of nanometer manganese dioxide composite materials

The electromagnetic properties of nanometer-sized manganese dioxide and silica dioxide/manganese dioxide composite in the frequency range 2–18 GHz are discussed in this paper. Findings show that MnO2 is a kind of dielectric loss media with broad frequency bandwidth. Moreover, with the increasing of the MnO2 filing proportion, the wave absorbing peak values drift to the lower frequency band. Analyses of transmission electron microscope (TEM) micrograph and electromagnetic parameters of MnO2 particulate show that its wave attenuation property can be attributed mainly to its flaky and stripshaped topography and high dielectric constant.

Electromagnetic wave absorption properties of carbon powder from catalysed carbon black in X and Ku bands

Carbon powder from catalysed carbon black (CPCCB) was prepared after a pyrogenation of carbon black (CB) with nanosized iron catalyst at atmospheric pressure and a temperature of 1100 °C. The complex relative permittivity and permeability of the CPCCB were measured by a reflection/transmission technique in the X and Ku bands. The reflection loss of CPCCB/paraffin wax composite was recorded. A wider absorption frequency range in the X band and Ku band could be obtained by adding 3 vol.% and 6 vol.% CPCCB in paraffin wax, respectively. Our results indicate that CPCCB could be a promising microwave absorption material.