Figure 3b and c show that most of the nanoparticles were embedded in the PVDF matrix, with no clear evidence of Al particle-matrix debonding, indicating a relatively strong interfacial bonding and good compatibility between the Al nanoparticles and the matrix; and only a very small amount of nanoparticles were exposed outside, that is, most of the Al nanoparticles were uniformly wrapped by the matrix [29], So, after surface modifications, no large obvious Al nanoparticle conglobations and agglomerations were found, indicating a uniform dispersion of the nanoparticles in the matrix.
3 we can observe that no large obvious Al nanoparticle conglobations and agglomerations exist, indicating improved interfacial bonding strength between the filler and matrix, and a uniform dispersion of the nanoparticles in the matrix; therefore, this increase in the permittivity can be ascribed to the fact that the silane coupler or PDA shell acts as a molecular bridge between the matrix and the filler, which effectively eliminates the voids and defects at the phase interfaces, and improves the interfacial adherence strength, thereby resulting in an enhanced dielectric permittivity [32], Furthermore, Al nanoparticles homogeneously dispersed in the matrix, are conducive to enhancing the interfacial polarizations resulting from enormous interfacial areas.
