A Study On The Methods Of Observation On The Microstructure Of LDPE Matrix Nanocomposite By Using Scanning Electron Microscope

Polyethylene nano dielectric is composite material with inorganic nanometer-filler evenly mixed in polyethylene matrix, based on polyethylene.Because the nano materials have quantum effects, size effects and interface effects, the composite materials have many excellent properties, which has received wide attention in the field of HVDC cables. However, we do not have a profound understanding of the microstructure if polyethylene based nano dielectrics. The resolution of field emission scanning electron microscope?FEG-SEM? breaks through the wavelength limit of optical microscope, and sample preparation is simple, so FEG-SEM could be regarded as an important tool for measuring the sample surface morphology. But due to the low conductivity of polyethylene, a conductive channel in a scanning electron microscope is unable to be formed, thus images with high resolution cannot be obtained. Therefore, the SEM image of polyethylene nano dielectric composite material with high definition is very important in the field of engineering dielectric.In this dissertation, the characteristics of SEM were studied. The principle of SEM and the characteristics of SEM images with different accelerating voltages,working distance and different signal were also studied. Secondly, the section and surface of polyethylene and SiO₂/LDPE materials, and the characteristics of obtained SEM image at the 0%, 30% and 100% BSE signal, respectively, were studied, using nano SiO₂ as an example. The accelerating voltage and working distance of polyethylene and SiO₂/LDPE compound materials were conformed.For polyethylene and SiO₂/LDPE materials, this paper studied the methods of preparing flatness surface of samples, and preparing the working parameters of the tested surface. In addition, the charged phenomenon in polyethylene and SiO₂/polyethylene materials was investigated, and the eliminating of charging phenomena of samples was summarized.Finally, the crystallization characteristics LDPE and SiO₂/LDPE were researched in the current study. By using polarizing microscope and atomic force microscope the crystallizing fields of LDPE and SiO₂/LDPE captured by scanning electron microscope were compared. The results showed that the crystallizing fields captured by the scanning electron microscope and atomic force microscope were exactly the same. Moreover. Nano particles and the polyethylene matrix distribution under the scanning electron microscope were studied. The results indicated that one part of SiO₂ is randomly distributed,another part of SiO₂ is distributed around spherocrystal in the matrix, when the contents of SiO₂ is 1wt%. SiO₂ is complete randomly distributed in the matrix when the contents are 3wt%.