Dielectric Properties And Interface Compatibility Of CCTO/PVDF Composites

With the rapid development of electronic and electrical industry, electroniccomponents are developing rapidly in towards miniaturization and high-speed. Energystorage index has been paid much attention as a key indicator of electronic components.The experts and scholars are studying many kinds of dielectric materials, which have higherdielectric constant, lower dielectric loss and processing performance more excellent. Withthe deepening of the exploration, more and more kinds of composite materials have beenstudied. Moreover, the study found that due to the interfacial compatibility between twophases in the composites has a significant influence on various properties of compositematerials, scholars from domestic and foreign did a lot for trying to improve the two-phaseinterface compatibility. The characterization of composite interface compatibility alsocaught much research. At present, most of the researchers only carried out on the compositematerial with the qualitative analysis of composites, and only a few scholars can use themethod of quantitative characterization analysis of the composite scattered interfacecompatibility through digital image processing techniques.In this paper, different kinds and the different mass fraction of coupling agents wereused to modify copper calcium titanate (CCTO) with giant dielectric constant. Poly(vinylidene fluoride)(PVDF) was dissolved in N,N dimethyl formamide (DMF), then usingthe method of solution mixing, modified CCTO and PVDF were mixed to become modifiedCCTO/PVDF composite films, which have different kinds and mass fraction of couplingagent. And, morphology analysis (SEM), structure analysis (XRD), infrared analysis (FTIR)and the analysis of the dielectric properties and dielecric strength were analyzed. Finally, byusing digital image processing methods for analyzing composite transmission electronmicroscopy (TEM), and combined with the fractal theory formula, the interfacialcompatibility of the composites was quantitatively characterized. The results show that different types of coupling agents have different influence on thedielectric properties of the composite films. Silane coupling agent is the best, and thentitanate coupling agent, the worst is aluminum zirconium coupling agent. Through test andanalysis, it could be learned that the amount of coupling agent was not the more the betterwithin a certain range, and with the increase of the amount of coupling agents, the dielectricconstant increased first and then decreased. The addition of coupling agent only changedthe connection of CCTO and PVDF, and had no effect on the crystallization of thecomposite material. However, PVDF crystal structure had been destroyed a little. Addingcoupling agent will make energy storage density increase with the order:0.4wt%A171＞0.6wt%KH560＞0.6wt%ZJ311＞0.2wt%ZJ101＞0.4wt%LD139. The optimal issilane coupling agent A171when its content was0.4wt%, i.e., when the frequency f is104Hz, the value of dielectric constant is50.0, and the value of dielectric loss is0.0462, andthe value of energy storage density is1.58times of the value of that not modified.For the quantitative characterization of composite materials uniformity, in the paper,the TEM images of composite materials were processed, in order to make the image qualityand image contrast improved, let image grayscale widened and make the CCTO particlesclearer. Combined with the box-counting dimension of fractal theory, the materialuniformity was analyzed. The smaller the fractal dimension is, the better the uniformity ofdispersion interface is. Through digital image processing technology for the analysis ofunmodified and modified with A171composite film TEM patterns, the box-countingdimension of modified film is1.46, which is less than that of unmodified one (1.50), so theinterface compatibility of modified film is better.At present, the ceramic/polymer composites is one of the hot research topics in thefield of electronics. In this paper, five kinds of coupling agent had been choosen to modifycomposite material, and the test method is simple, with the raw material easy to obtain.Coupling agent can improve the two phase interface compatibility of composite materials,and make two phase dispersed evenly, and improve the performance of the materials.Combing box-counting dimension theory with digital image processing technology, quantitative characterization of uniformity of the composite material dispersion andinterface compatibility could be obtained. It gives a new way for the research of multiphasecomposite materials.