Liu Shunhua

Investigation of electrical conductivity and electromagnetic shielding effectiveness of polyaniline composite

Abstract With the increasing of electromagnetic pollution and the widely use of commercial and military products, there is an increasing interest in electromagnetic interference (EMI) shielding. This paper mainly aims at electrical conductivity and EMI shielding effectiveness (SE) of the conducting composites made from silicone rubber (SR) with different loading levels of HCl-doped polyaniline (PAN-HCl) in the low frequency range from 3 to 1500 MHz. The result indicates that SE of the composites increase and the volume resistivity decrease with increasing mass ratio loading of PAN-HCl in the SR. The measured SE of the composites are from 16 to 19.3 dB at 100 mass ratio loading of the PAN-HCl and the volume resistivity decrease nine orders of magnitude compared with that of the emeraldine base form of PAN (PAN-EB) composites.

Absorbing properties of α-manganese dioxide/carbon black double-layer composites

In order to improve the absorbing properties of the electromagnetic wave absorbing plate, double-layer wave absorbing materials, which are composed of a matching layer and an absorbing layer, were devised. The matching layer is a surface layer of the wave absorbing sample, from which most of the incident waves easily enter the sample, and the absorbing layer is a second layer under the matching layer, which plays an important role in incident wave attenuation. The total thickness of the double-layer composites is the sum of the thicknesses of the matching layer and the absorbing layer. In this paper, α-manganese dioxide and carbon black (CB) were used as absorbents in the matching layer and the absorbing layer respectively. Meanwhile, the structure of the α-manganese dioxide and the CB particles were analysed by x-ray diffraction and transmission electron microscopy, and the dielectric property and absorbing mechanics were also studied. The results showed that, in the case of the mass fraction of CB in the absorbing layer being 30% and the thickness of the absorbing layer being 3 mm, the effectual absorption band (below −10 dB) of the double-layer wave absorbing materials reaches 8.6 GHz and 7.6 GHz in the testing frequency range between 8 GHz and 18 GHz, respectively, when the mass fraction of α-MnO2 in the matching layer was 10% and the thicknesses of the matching layer were 2 mm and 1 mm, respectively, and the effectual absorption band (below −10 dB) reaches 8.7 GHz in 8–18 GHz when the mass fraction of α-MnO2 in the matching layer was 20% and the thickness of the matching layer was 2 mm.

Investigation of Electromagnetic Characteristics of Polyaniline Composites

With the increase of electromagnetic pollution and the wide use of commercial and military products, there is an increasing interest in electromagnetic interference (EMI) shielding. This article mainly aims at the effect of high magnetic field (HMF) on the grain shape and electrical conductivity of HCl-doped polyaniline (Pani-HCl), and the electrical conductivity and EMI shielding effectiveness (SE) of the conducting composites made from silicone rubber (SR) with different loading levels of Pani-HCl (without HMF) in the low frequency range from 3 to 1500 MHz. The result indicates that SE of the composites containing Pani-HCl (without HMF) increases and the volume resistivity decreases with increasing mass ratio loading of Pani-HCl in the SR. The measured SE of the composites are from 16 to 19.3 dB at 100 mass ratio loading of Pani-HCl and the volume resistivity decreases nine orders of magnitude compared with that of the emeraldine base form of Pani (Pani-EB) composites. The influence of HMF on electrical conductivity and grain shape of Pani-HCl is great. The grain shape of the in situ polymerization of PAN in 10T is an open-ramified rod-like pattern with a diameter of 50 nm and that of secondary doped PAN in 10T change to spherical structures of diameter of about 20-30 nm, which are obviously different from the irregular reef-like particle shape of doped PAN in 0T. It is thought that the reason for the different grain shape is anisotropic diamagnetic susceptibility of doped PAN and orientations of the HMF.