Enaineerina Interface/Interphase For Formulating The Microwave Dielectric Frequency Dispersion In Carbon Nanocomposites

Interface constitutes a significant volume fraction in nanocomposites.With decreasing filler size,the filler-matrix interfaces become more spatially extensive and complex,playing a pivotal role in determining the ultimate performance of composites properties.However,the development and optimization of nanocomposites is restricted by the limited exploration and understanding of interfaces.It requires the ability to tune and tailor interfaces to tap the full potential of nanocomposites.In this study,we take multi-walled carbon nanotubes/silicone elastomer nanocomposites as a representative material system,and have explored the correlation between interfacial properties and high frequency dielectric response systematically from the perspective of engineering interface in functionality context.Interface modification and interface design across different length scales are carried out.Together with dielectric spectra and relaxation process analyses,this study affords to improve the understanding of interface and its role in determining dielectric properties.Overall,this study opens up new possibilities for designing and engineering dielectric functional nanocomposites.Interfaces together with other meso-structural parameters(volume fraction,dispersion and agglomeration)play decisive roles in formulating the dielectric patterns(permittivity,relaxation process).Both covalent and non-covalent modification methods have been applied in this study to modify filler-matrix interfacial properties.The local distribution and destruction of ?-? electron network on CNTs have resulted in the change of conductivity and permittivity.With improved dispersion of CNTs in polymer matrix,the characteristic relaxation peak shifts to higher frequencies.Meanwhile,the relaxation peak is also enhanced with stronger interfacial bonding.Altogether,these structural features determine the dielectric response in carbon nanocomposites.Based on the sensitivity of dielectric spectra to intermolecular interaction and structural properties,dielectric measurements are coupled with cyclic loading to characterize the dynamic evolution of interfaces in carbon nanocomposites.With different interfacial modification methods,the samples exhibit distinct patterns of evolution under cyclic loading.The interface reconstruction process in the surfactant-modified sample is observed from the dielectric spectra as the disappearance and reappearance of relaxation peak.On the other hand,the accumulated breakage of the interfacial bonding in CA-MWCNTs/SE is reflected in dielectric spectra as the gradual disappearance of relaxation peak.The novel method developed here is instrumental to understand the filler-matrix interaction in general nanocomposites.Furthermore,we have designed and introduced a relatively large-scale vertical interphase into carbon nanocomposites,in which dielectric response and relaxation process have been successfully tailored.A remarkable relaxation process has been observed in vertical-interphase nanocomposites,which shows sensitivity to both filler volume fraction and the polarization ability of the compositions.From this perspective,it is convenient and efficient to tune the high-frequency properties of carbon nanocomposites.The insights provided here will pave the way for optimized design and precision engineering of microwave functional polymer nanocomposites and enabled devices.