Search Results (3)

Electromagnetic interference (EMI) has been recognized as a new sort of pollution and can be considered as the direct interference of electromagnetic waves among electronic equipment that frequently affects their typical efficiency. As a result, shielding the electronics from this interfering radiation has been addressed as critical issue of great interest. In this study, different hybrid nanocomposites consisting of magnetite nanoparticles (Fe₃O₄) and reduced graphene oxide (rGO) as (conductive/magnetic) fillers, taking into account different rGO mass ratios, were synthesized and characterized by XRD, Raman spectroscopy, TEM and their magnetic properties were assessed via VSM. The acquired fillers were encapsulated in the polyurethane foam matrix with different loading percentages (wt%) to evaluate their role in EMI shielding. Moreover, their structure, morphology, and thermal stability were investigated by SEM, FTIR, and TGA, respectively. In addition, the impact of filler loading on their final mechanical properties was determined. The obtained results revealed that the Fe₃O₄@rGO composites displayed superparamagnetic behavior and acceptable electrical conductivity value. The performance assessment of the conducting Fe₃O₄@rGO/PU composite foams in EMI shielding efficiency (SE) was investigated at the X-band (8–12) GHz, and interestingly, an optimized value of SE −33 dBw was achieved with Fe₃O₄@rGO at a 80:20 wt% ratio and 35 wt% filler loading in the final effective PU matrix. Thus, this study sheds light on a novel optimization strategy for electromagnetic shielding, taking into account conducting new materials with variable filler loading, composition ratio, and mechanical properties in such a way as to open the door for achieving a remarkable SE. Full article

A study addressed to develop new recyclable and/or biodegradable magnetic polymeric materials is reported. The selected matrices were polypropylene (PP) and poly (lactic acid) (PLA). As known, PP corresponds to a non-polar homo-chain polymer and a commodity, while PLA is a biodegradable polar hetero-chain polymer. To obtain the magnetic nanocomposites, magnetite supported on thermally reduced graphene oxide (TrGO:Fe₃O₄ nanomaterial) to these polymer matrices was added. The TrGO:Fe₃O₄ nanomaterials were obtained by a co-precipitation method using two types of TrGO obtained by the reduction at 600 °C and 1000 °C of graphite oxide. Two ratios of 2.5:1 and 9.6:1 of the magnetite precursor (FeCl₃) and TrGO were used to produce these nanomaterials. Consequently, four types of nanomaterials were obtained and characterized. Nanocomposites were obtained using these nanomaterials as filler by melt mixer method in polypropylene (PP) or polylactic acid (PLA) matrix, the filler contents were 3, 5, and 7 wt.%. Results showed that TrGO₆₀₀-based nanomaterials presented higher coercivity (Hc = 8.5 Oe) at 9.6:1 ratio than TrGO₁₀₀₀-based nanomaterials (Hc = 4.2 Oe). PLA and PP nanocomposites containing 7 wt.% of filler presented coercivity of 3.7 and 5.3 Oe, respectively. Theoretical models were used to analyze some relevant experimental results of the nanocomposites such as mechanical and magnetic properties. Full article

The high thermal conductivity and stability, outstanding mechanical properties, and low weight make graphene suitable for many applications in the realm of thermal management, especially in high integration systems. Herein, we report a high-performance, low-temperature reduced graphene oxide/magnetic carbon fiber composite film. Magnetic carbon fibers were prepared using a co-precipitation method, and the graphene oxide solution was prepared using an improved Hummers’ method. The magnetic carbon fibers were orientated by magnetite and immersed in the graphene oxide solution during filtration, followed by annealing at 800 °C. The composite film exhibited improved thermal conductivity (over 600 W/m·K) and mechanical properties (tensile strength of 37.1 MPa and bending cycle of up to 8000). The experimental results illustrate that the graphene in the composite membrane provides heat transfer channels to promote in-plane thermal conductivity, while the magnetic carbon fiber acts as a scaffold to reinforce the mechanical properties and improve the quality of the graphene. Due to the synergistic effect of the graphene and magnetic carbon, this composite has wide potential applications in heat dissipation. Full article