Preparation Of Tarium Bitanate @ Bi-component Core-shell Filler And Dielectric Properties Of Polymer Matrix Composites

Ceramic/polymer matrix composites with high breakdown strength and low dielectric loss have great potential in the miniaturization,integration and functional development of electronic products.However,there are some problems,such as high dielectric loss.In order to solve the above problems,meanwhile to improve breakdown strength,the composites filling with the core-shell particles,especially the particles using barium titanate(BT)as the core,have been pay attention to.The preparation of core-shell filler often need surface modification for ceramics,so it is also considered on the potential environmental pollution.In this paper,"green"malic acid were used as surface modifier of barium titanate and doping agent of polyaniline(PANI)to prepare BT@PANI core shell particles.The polyvinylidene fluoride(PVDF)based composite material presented good dielectric properties.On this basis,to further regulate the dielectric loss of the composite,the composition of the shell layer was adjusted by silver(Ag)and iron(Fe₃O₄),respectively.The dielectric mechanism of the composite was explored.The main research contents and research results are as follows:(1)The BT@PANI core-shell particles were prepared by in-situ polymerization.The PVDF-based dielectric composites were prepared by using the particles as the filler.The results showed that the core-shell structure characteristics of BT@PANI particles were obvious.With the increase of the mass ratio of aniline to BT,the thickness of the shell increased and the part of the shell thickened.When the mass ratio of aniline and barium titanate was 0.5:1,the percolation threshold of BT@PANI/PVDF composite appeared at 40wt%.The dielectric constant and dielectric loss of the composite were176 and 19.57(100 Hz),122 and 3.13(10³Hz),respectively.When the content was 30wt%,these values were 43 and 0.57(100 Hz),31 and 0.31(10³Hz),respectively.The composite showed high dielectric constant and low dielectric loss.The dielectric properties also presented good frequency dependence in the range of 10³?10⁶ Hz.The excellent dielectric properties of the composite can be attributed to the low conductivity because the dopant of PANI was malic acid not the protonic acid.The BT@PANI/PVDF composite achieved multiple dielectric mechanisms such as interface polarization,barium titanate self-polarization and micro-capacitance,and effectively weakened the leakage loss.(2)In order to suppress the dielectric loss of the composites material,the BT@PANI-Ag core-shell particles were prepared on PANI shell by additional reducing agent method in situ.The results showed that the shell of the particles possessed bi-component structure characteristics.With the mass ratio of Ag NO₃ to BT@PANI increased,the dielectric constant of the composites increased.When the mass ratio of Ag NO₃ to BT@PANI is 2:1,the dielectric properties of the composite(30 wt%)presented unstable dependency on frequency.When the content was 30 wt%and the mass ratio of Ag NO₃ to BT@PANI was 1:1,the values were 28 and 0.15(10³Hz)?In comparison with the BT@PANI/PVDF composites,the values of dielectric loss reduced by more than two times while the values of dielectric constant was slightly low.(3)In order to suppress the dielectric loss of the composites,BT@PANI-Fe₃O₄core-shell particles were prepared by oxidation precipitation process,and the BT@PANI-Fe₃O₄/PVDF composite was prepared by using this particles as filler.The results showed that the shell of the particles possessed bi-component structure characteristics.With the increase of Fe₃O₄ content in the filler,dielectric constant of the BT@PANI-Fe₃O₄/PVDF(10 wt%)composites increased.When the content of Fe₃O₄,these values were lower those of the BT@PANI/PVDF composites.Dielectric loss also showed an increasing trend.Their values which were in range of 0.04?0.12were lower than those of the BT@PANI/PVDF composites.Furthermore,the dependence of dielectric properties on frequency was improved.When the mass ratio of ammonium ferrous sulfate to BT@PANI core-shell particles is 0.6:1,the dielectric values of the BT@PANI/BT@PANI-Fe₃O₄/PVDF composites,which the contents of two type fillers were 30 wt%and 10 wt%,can reach 37.5 and 0.42(10³ Hz).This work realized the control of dielectric loss of the polymer-based composite materials.