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 degrees C and 100 Hz - 5 MHz respectively. The incorporation of the nano Ni@SiO2 to PMMA has a positive effect on the dielectric constant epsilon' of the nanocomposites, as well as, epsilon' 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 epsilon" 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.%.