In this study nanocomposites consisting of an epoxy resin and ceramic zinc ferrite nanoparticles have been successfully developed and investigated morphologically and structurally by means of scanning electron microscopy (SEM) images and X-ray diffraction (XRD) spectra. The thermal properties of the nanocomposites were studied via differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The thermomechanical characterization of the fabricated nanocomposites was studied via dynamic mechanical analysis (DMA) and the magneto-dielectric response was assessed by means of a broadband dielectric spectroscopy (BDS) and by employing a superconducting quantum interference device (SQUID) magnetometer. Data analysis demonstrates that the incorporation of nanoinclusions into the matrix improves both the thermomechanical and the dielectric properties of the systems, as indicated by the increase of the storage modulus, the real part of dielectric permittivity and conductivity values with filler content, while at the same time induces magnetic properties into the matrix. Zinc ferrite nanoparticles and their respective nanocomposites exhibit superparamagnetic behavior at room temperature. Three relaxations were recorded in the dielectric spectra of all systems; originating from the filler and the polymer matrix, namely interfacial polarization, glass to rubber transition of the polymer matrix and the reorientation of small polar side groups of the polymer chain.

In the present study two sets of nanocomposites consisting of an epoxy resin and BaFe₁₂O₁₉ or SrFe₁₂O₁₉ nanoparticles were successfully developed and characterized morphologically and structurally via scanning electron microscopy and X-ray diffraction spectra. The dielectric response of the nanocomposites was investigated by means of broadband dielectric spectroscopy and their magnetic properties were derived from magnetization tests. Experimental data imply that the incorporation of the ceramic nanoparticles enhances significantly the dielectric properties of the examined systems and their ability to store electrical energy. Dielectric spectra of all systems revealed the presence of three distinct relaxation mechanisms, which are attributed both to the polymer matrix and the nanoinclusions: Interfacial polarization, glass to rubber transition of the polymer matrix and the re-orientation of small polar side groups of the polymer chain. The magnetic measurements confirmed the ferromagnetic nature of the nanocomposites. The induced magnetic properties increase with the inclusion of hexaferrite nanoparticles. The nanocomposites with SrFe₁₂O₁₉ nanoparticles exhibit higher values of coercive field, magnetization, magnetic saturation and remanence magnetization. A magnetic transition was detected in the ZFC/FC curves in the case of the BaFe₁₂O₁₉/epoxy nanocomposites.

In this study, hybrid nanocomposites consisting of Fe₃O₄/BaTiO₃/epoxy resin were prepared with varying amounts of filer content. Structural and morphological characterization, conducted via X-Ray Diffraction patterns and Scanning Electron Microscopy images, revealed the successful fabrication of composites and fine dispersion of inclusions. Thermomechanical properties are studied via Differential Scanning Calorimetry, Thermogravimetric Analysis, Dynamic Mechanical Analysis and static mechanical tests. Hybrid composites exhibit enhanced thermal stability and improved mechanical response. Indicatively, Young’s modulus, tensile strength and fracture toughness increase from 1.26 GPa, 22.25 MPa, and 3.03 kJ/m³ for the neat epoxy to 1.39 GPa, 45.73 MPa, and 41.08 kJ/m³ for the composites with 20 or 15 parts per hundred resin per mass (phr) of Fe₃O₄, respectively. Electrical behavior is investigated via Broadband Dielectric Spectroscopy and ac conductivity measurements. The real part of dielectric permittivity reaches the value of 11.11 at 30 °C for the composite with 40 phr of Fe₃O₄. The ability to store and retrieve electric energy on the nanocomposites is examined with the following parameters: the filler content and the applied voltage under dc conditions. Retrieved energy reaches 79.23% of the stored one, for the system with 15 phr of Fe₃O₄. Magnetic response is studied via a Vibrating Sample Magnetometer. Magnetic saturation, for the system with the highest magnetic filler content, obtains the value of 25.38 Am²/kg, while pure magnetic powder attains the value of 86.75 Am²/kg. Finally, the multifunctional performance of the nanocomposites is assessed regarding all the exerted stimuli and the optimum behavior is discussed.