The Sutdy On The Preparation And Shielding Properties Of Polyaniline/Nano Nickel Composite Materials

With the rapid development of society,various kinds of radio communication equipment,electronic instruments and computers have been widely used in various aspects of the national economy.These electrical devices provide humans with convenience while providing more and more artificial electromagnetic radiation and interference for humans.PANI/Ni composite shielding material not only retains the controllability of PANI dielectric properties and bandwidth of absorption frequency and other advantages,but also can make up for the lack of nano-nicke(Ni)shielding materials,it has a bright future.In this thesis,using Ni and aniline as raw materials,citric acid as doping acid and ammonium persulfate(APS)as oxidant,PANI/Ni composites and their modified composites were prepared.The effect of the reaction conditions,the ratio of Ni to aniline and modifiers on the properties of the composites were studied.The specific studies were list as following:(1)A series of PANI/Ni composites were prepared by in-situ polymerization of aniline using Ni as core,citric acid as dopant and APS as oxidant.The effect of the reaction time,reaction temperature,oxidant dosage and citric acid concentrati on the conductivity and other related properties of PANI/Ni composites were systematic studied.The composites were characterized by Infrared spectroscopy(FTIR),UV-Vis,and X-ray diffraction(XRD).The analysis results showed that the reaction time,reaction temperature,the amount of APS and the concentration of citric acid have a great influence on the molecular structure and crystallinity of the composites.The four-probe tester results showed that the reaction time,reaction temperature,the amount of oxidant(APS)and citric acid concentration have a great impact on the conductivity of the composites.It was found that the best reaction time for obtaining high conductivity polyaniline was 10 h,the best reaction temperature was about 5?,the molar ratio of oxidant amine persulfate to aniline was 1.5:1,and the citric acid concentration was 1.5 mol/L.(2)The PANI/Ni composites with different ratios of Ni and aniline weresynthesized by in-situ polymerization of aniline using Ni as core,citric acid as dopant and APS as oxidant and the effect of different ratios of Ni and aniline on properties of composites were studied.Research showed that the PANI/Ni composites with different ratios of Ni and aniline were prepared by in-situ polymerization.The FTIR and XRD results showed that there is no chemical bond between Ni and PANI.The results of UV-visible absorption spectrum showed that Ni has little effect on its molecular structure when PANI is polymerized.The conductivity of PANI/Ni composites is significantly better than that of pure PANI.When the mass ratio of Ni to aniline is 1:3,the conductivity of the synthesized composite reaches a maximum of 1.82 S/cm.After the shielding film was prepared using the synthesized PANI/Ni composites,the electromagnetic shielding performance was measured in the low frequency band 0~1500 MHz and high frequency band 2~18 GHz and the results shown that the obtained film have good electromagnetic shielding effectiveness,especially in the high frequency band 2~18 GHz.The different mass ratio of Ni and PANI has the best ratio of the shielding effectiveness of the composite film,and the composite film prepared with the mass ratio of Ni to aniline of 1:3 has the best shielding effectiveness in the shielding range of 3.6~5.36 GHz,the maximum shielding effectiveness is66.5 dB(3)Pretreatment modification of Ni with p-aminobenzoic acid,amino phenylacetic acid and amino phenylbutyric acid.The results of FTIR spectra showed that p-aminobenzoic acid,amino phenylacetic acid and amino phenylbutyric acid can interact with Ni powder through chemical bonds,and amino functional groups can be introduced onto the surface of Ni particles.The results of XRD analysis showed that Ni was modified by three different modifiers of p-aminobenzoic acid,amino phenylacetic acid and amino phenylbutyric acid did not affect the lattice structure of Ni and the purity was high after modification.(4)The composites were synthesized by in-situ polymerization of aniline using p-aminobenzoic acid-Ni,amino phenylacetic-Ni,amino phenylbutyric acid-Ni as core.The TEM images showed that all three modified composites have a core-shell structure;The FTIR,UV-Vis and XRD analysis show that there are chemical bonds between Ni and PANI in the three modified composites;The results of thermogravimetric analysis showed that the presence of modified Nicould improve the thermal stability of PANI,and the thermal stability of PANI in the composites modified with amino phenylacetic acid was the best;The Raman spectroscopy and the four-probe tester showed that the conductivity of the modified composites was higher than that of PANI.The conductivity of amino phenylacetic acid-PANI/Ni was the best when using 0.1 mol/L amino phenylacetic acid modified composite.The electrical conductivities of p-aminobenzoic acid-PANI/Ni,amino phenylacetic acid-PANI/Ni,amino phenylbutyric acid-PANI/Ni and unmodified PANI were 1.848 S/cm,1.941 S/cm,1.781 S/cm and 0.847 S/cm,respectively.The vector network analyzer measured the shielding effectiveness of composite films prepared from the composites modified with three modifiers in the low frequency range of 0 to 1500 MHz and the high frequency range of 2 to 18 GHz.The shielding effectiveness of the composite film prepared from the composites modified by the three modifiers is significantly increased,especially the shielding effectiveness of the composite membrane prepared from amino phenylacetic acid-PANI/Ni reaches a maximum state.Electromagnetic parameter analysis indicates that this is due to the natural magnetic resonance of the Ni core giving it a strong magnetic loss and PANI imparting a strong dielectric loss.