Thermal Conductivity And Electrical Insulation Of AIN/epoxy Composites

In this dissertation, we used bisphenol A type epoxy resin as matrix and aluminumnitride (AlN) powder as filler to prepare AlN/epoxy resin composites with different fillerscontent. To study the crystal structure, thermal stability, morphology, rheological properties,thermal conductivity and electrical performance of the composites, X-ray diffraction (XRD),thermogravimetric analyzer (TGA), differential scanning calorimeter (DSC), scanningelectron microscope (SEM), rotational rheometer, thermal conductivity meter, highresistance meter, and breakdown voltage tester were used. Based on experimental results,the following conclusions can be obtained:AlN fillers can be evenly dispersed in the epoxy resin matrix, without obviousagglomeration. In the process of preparing composite materials, the crystal structure of AlNhas not been destroyed. The addition of aluminum nitride fillers decreased the thermaldecomposition temperature and the glass transition temperature of AlN/epoxy composites.Adding AlN particles did not influence the volume resistivity and dielectric strength, andthe composites still had good electrical insulation properties and can be used as insulatingmaterials.With the increasing of AlN, the apparent viscosity and shear stress of the compoundsystem increased significantly, and the non-Newtonian shear-thinning behavior was alsomore obvious. The higher of temperature or faster of shear rate, the apparent viscosity ofthe composites was lower. In the same condition, materials filled with the bigger micronsize of fillers had lower viscosity. Compared with using single particle size fillers, hybridfillers improved the flowability of composite.The thermal conductivities of AlN/epoxy composites improved remarkably with theincreasing of AlN fillers. Meanwhile, the composites with larger sized AlN showed betterthermally conductive properties at high loading content. When the volume fraction of6.3 μm AlN fillers was30%, the thermal conductivity of the composites achieved0.44W/(m·K), being more than2.2times of that of neat epoxy. Compared to single particle sizefillers, using hybrid fillers failed to significantly improve the thermal conductivity ofAlN/epoxy composites. Choosing some different thermal conductivity models to fit theexperimental data, we found that the Nielsen-Lewis model was more suitable. Through theanalysis, we introduced a correction factor into the Maxwell-Eucken model, and establisheda new model which is in good agreement with our experiments.