High Power Ultrasonic Testing Method for Agglomeration of Nanoparticles in Nanocomposite Dielectrics

The high surface per unit volume of nanoparticles leads to strong attractive interaction between particles producing high agglomeration tendency [1]-[2]. The agglomeration of nano particles in the polymer will reduce the overall modification effect of the material. When the degree of agglomeration is severe, it may even cause serious deterioration of the mechanical and electrical properties of materials [3]. Electron microscope imaging is the main method to detect the dispersion of nano fillers in solid dielectrics, but this method is easily limited by the detection range, so the evaluation of the overall dispersion of materials still needs to be further explored. In this paper, according to the mechanical constitutive relationship in nanocomposite dielectrics, we first theoretically analyzed the feasibility of nonlinear acoustic detection method. Then the samples with different dispersion degree were prepared by adjusting the dispersion factors, and the feasibility of the detection method was verified by scanning electron microscope (SEM), broadband dielectric spectroscopy (BDS) and nonlinear ultrasonic test results. Finally, we use this method to detect functionally graded materials (FGM), and realize the nonlinear acoustic imaging of FGM, which provides a new way for the dispersion detection of nano materials like nanocomposite dielectric and FGM.