Fabrication and characterization of metal-core carbon-shell nanoparticles reinforced epoxy nanocomposites

Metal nanoparticles (NPs) were prepared starting from acrylamide complex of iron (FeAAm) nitrates. Precursors thermolysis at constant temperature in a self-generated atmosphere lead to formation of metal NPs, whose dimensions depend by the temperature and the time of synthesis. These NPs were used in different percentages to prepare epoxy resin based nanocomposites. Transmission Electronic Microscopy (TEM) was employed to determine shape and dimensions of the synthetized NPs. Their internal structure was investigated using the X-Ray diffraction, and results have revealed a metal core/polymeric shell structure. These results were also confirmed by cross Thermogravimetric analysis (TGA) and vibrating sample magnetometer (VSM). Optical microscopy, performed on the NPs/epoxy resin system, was used to determine the obtained dispersion degree. Thermogravimetric analysis was employed to study the effect of NPs on the thermal stability of composites, showing that negligible variations are induced by their presence. Thermomechanical characterization, performed using a Dynamic Mechanical Analyzer (DMA), have revealed a slight increase in the room temperature elastic modulus, while more remarkable variations are induced at high temperature. Glass transition temperature (Tg) does not result significantly affected by the presence of the nanoparticles. A complete fracture characterization was carried out to assess the effect of nanoparticles addition compared to the neat resin system, and the presence of NPs induces a global increase in the fracture energy: this effect is a consequence of the fracture path lengthening. However, higher filler contents are characterized by a lower increase in fracture energy, due to the coalescence of the voids around the debonded nanoparticles. Magnetic tests, performed using a vibrating sample magnetometer, have revealed the ferromagnetic behavior of the iron particles based nanocomposites. In particular, saturation magnetization and coercivity were found dependent on the diameter of the iron core which depends, in turn, by the NPs pyrolysis temperature. Therefore nanocomposites filled with high temperature synthetized NPs show a stronger ferromagnetic behavior.