Preparation,Characterization And Terahertz Detection Spectra Of Doped Composite Coatings

Terahertz waves are ultra-high frequency electromagnetic waves,located between the microwave and infrared bands,they have both macroscopic classical theory and microscopic quantum theory.Terahertz technology has the characteristics of high signal-to-noise ratio,low photon energy that do not damage to the detected objects.It can easily and conveniently obtain the photoelectric response amplitude and phase information of material,it can be applied to the fields of material spectroscopy and non-destructive testing.The thesis prepared the doped composite coatings contained two different nano-fillers:Graphene/epoxy resin coating and CNTs@Ti/epoxy resin coating,and tested their physical and chemical properties.SEM results showed that the nano-filler dispersed in the epoxy resin matrix very well by using ultrasonic dispersion.XRD,FTIR and Raman spectroscopy results showed the interaction between the nano-filler and the matrix.Nano-fillers with conductive properties improved the electrical properties of the composite coatings.With the increasing of the concentration of nano-fillers,the conductive properties of the composite coatings gradually increased.The transmission terahertz spectroscopy system was used to study the terahertz spectrum characteristics of the two kinds of composite material coatings,and the terahertz spectrum analysis was performed on the coatings with different concentrations of nano-fillers at the same time.The experimental results showed that the time domain electric field loss of the composite coating increased,and the frequency domain power loss increased,with the concentration of nanofillers increasing,The absorption coefficient continued to increase with the increasing frequency,which is related to the dipole relaxation loss of polar molecules in the polymer matrix and the absorption of terahertz by carriers in nanometer materials.In addition,it was found that the CNTs@Ti/epoxy resin composite coating exhibited abnormal refractive index character under the action of terahertz waves,which may be due to the difference in the dielectric properties of the nano-metal contained therein,as well as the volume particle fraction and shape.In summary,by testing the physicochemical properties of the two doped composite coatings and analyzing their response under terahertz waves radiation,the physical properties of composite coatings contained nano-fillers are obtained,which has a certain reference for the study of new modified composite materials.It also explored the application of terahertz spectroscopy technology for photoelectric non-destructive testing of materials at the same time.