Dielectric and mechanical properties of nickel silica core-shell reinforced PMMA nanocomposites

This paper study the dielectric and mechanical properties of poly (methyl methacrylate)-nickel silica core-shell nanocomposite. Ni@SiO₂/PMMA nanocomposite films were prepared by incorporating Ni@SiO₂ nanoparticles in PMMA matrix using the solution casting method. The morphology of the prepared nanoparticles was examined through a High-resolution transition electron microscope (HRTEM), which revealed the formation of SiO₂ shell at Ni magnetic nanoparticles. The dielectric properties of the nanocomposite films were studied as a function of temperature and frequency in the ranges of 30–180°C and 100 Hz – 5 MHz respectively. The incorporation of the nano Ni@SiO₂ to PMMA has a positive effect on the dielectric constant ε′ of the nanocomposites, as well as, ε′ improved with increasing temperature. The real electric modulus (M′) of composites confirms the occurrence of dispersion in all composites at all temperatures. While dielectric loss tangent ε ″ and the loss part of electric modulus spectra (M) exhibit relaxation peaks which characterize possible relaxation of interfacial polarization in the interface between Ni@SiO₂ core-shell and PMMA matrix, these peaks have shifted towards higher frequency with temperature. The relaxation and activation energies, E_c and E_a values decreased from 0.49 to 0.40 eV and from 0.87 to 0.70 eV respectively as Ni@SiO₂ content increased. The ac conductivity of the nanocomposite films has deeply increased with increasing temperature and Ni@SiO₂ content. The longitudinal modulus (L), shear modulus (G), Young's modulus (E), and bulk modulus (B) of films were studied and they increased as the filler increased from 0 to 15 wt.%.