Preparation And EMI Properties Of Ni/PANI Composite Materials

Electromagnetic shielding is one of the main means in suppressing electromagneticradiation and electromagnetic interference (EMI). A new functional material with low reflectionand high absorption can prevent contamination of electromagnetic wave more effectively. Inthis paper, Polyaniline (PANI) with dielectric property, and nickel (Ni) with electromagneticproperty were used as electromagnetic shielding material. Preparations of PANI/Ni and theeffect of material type and content on the EMI performance of shielding coating were studied.In this paper, Ni/PANI composite powders with different mass ratio were synthesized insitu polymerization using hydrochloric acid (HCl), citric acid and camphorsulfonic acid (CSA)as the doping acid. Composite materials were characterized, measured and analysised by X-raydiffraction analyzer (XRD), scanning electron microscopy (SEM), Fourier transform infraredspectroscopy (FTIR), and four point probe instrument. The results showed that the compositeshad the core-shell structure, and there was no chemical bond between Ni and PANI. Theconductivity of composites was lower than that of the pure PANI, and the conductivityincreased with PANI increasing. The Ni of the composite had some loss when the doping acidwas the HCl.The coatings were prepared by mixing Ni with pure PANI doped by citric acidmechanically. The morphologies and properties of coatings were observed and measuredthrough SEM, the four point probe instrument and network analyzer. The results indicated thatthe conductivity of the coatings decreased, the shielding effectiveness (SE) and absorption lossincreased, and the SE of coatings was above60dB while using citric acid as the doped acid ofPANI.The coatings were prepared by adding Ni/PANI composites and Ni as the filler, and theirmicrostructure and properties were studied by SEM, the four point probe instrument andnetwork analyzer. The experimental results showed that the conductivity of the coatings withNi/PANI composite increased, and it was higher than that of the coating of Ni and PANI mixedmechanically. The conductivity of the coatings with composite obtained the maximum (92.58S/cm) when the mass ratio of Ni and AN was1:4and citric acid was used as dopant, the SE was 70~80dB and had small fluctuation in the frequency of30MHz~1500MHz, the absorptionloss was account for60%, which was agreement with the results of electromagnetic parameters.Besides, the contents of different mass ratio of composite (wt(Ni:An)=1:4) on properties ofcoatings were also studied. The results showed that the SE of the coatings with2.5wt%,4wt%,6wt%composite (Ni:An=1:4) were similar, the SE were about70~80dB,65~80dB and65~90dB in the frequency of30MHz~1500MHz, respectively, but the SE of the coating with9wt%composite (Ni:An=1:4) fell sharply and only was30~50dB.