Study on the non-destructive evaluation of overall particle dispersion within nanocomposites by nonlinear ultrasonic and its applicability

The dispersion of nanoparticles in nanocomposites seriously affects the material properties. However, the current nanoparticle dispersibility assessment mainly relies on the microscopic imaging method, which has the limitations of being lossy and having a narrow detection area, and is unable to realize the assessment of the overall dispersibility of the particles in bulk materials. This article uses nonlinear ultrasonic technology (NLUS) to achieve the overall dispersion evaluation of nanoparticles. Theoretical and experimental results show that: the nanoparticles nonlinear coefficient (Δβ) and the particle agglomeration degree (K) approximately satisfy the linear variation relationship (R² > 0.9), while the smaller the elastic modulus of the particles is, the larger the slope of the Δβ-K fitting function is; the results of the NLUS test are not affected by the factors of surface modification. The error between the NLUS nondestructive evaluation results of particle dispersion and the SEM lossy test results ranged from 3 % to 15 %. The single detection region of NLUS is a three-dimensional region of ultrasonic wave propagation and the single detection time is short, these features enable NLUS to be applied in the rapid non-destructive evaluation of the overall dispersion of large volume polymer-based nano-dielectric material particles.