Lightweight Magnetic Nanoparticle-Graphite Composites with Tunable and Enhanced Electromagnetic Wave Absorption...

In this study, Fe, Ni-Fe, and Co-Fe magnetic nanoparticle-graphite hybrid composites are synthesized via the coprecipitation method. The effects of metal type, metal/C mass ratio, metal salts (anhydrous or hydrated Fe salts), and pH adjustment agents (NH₄OH or NaOH) on product properties and electromagnetic interference (EMI) shielding efficiency are examined. X-ray diffraction (XRD) confirms the formation of a cubic spinel structure. Fourier transform infrared spectroscopy (FT-IR) identifies the functional groups in the composites. Scanning electron microscopy (SEM) images show that increasing the Fe ratio from 1 to 8 leads to the increase in particle size from 19 to 27 nm in average, while the choice of pH adjustment agent has a minimal effect on morphology. The use of anhydrous metal salts results in larger and more porous particles. Vibrating Sample Magnetometry (VSM) analysis reveals that the FeG6.14Na sample exhibits the highest saturation magnetization (59.8 emu/g), while the NiFeG6.14Na sample, having smaller particle size, shows the lowest (29.6 emu/g). X-ray photoelectron spectroscopy (XPS) confirms the coexistence of Fe²⁺, Fe³⁺, Ni²⁺, and Co²⁺ oxidation states. The band gap of the samples ranged from 1.18 (CoFeG6.14Na) to 1.65 eV (FeG4NaS). EMI shielding tests indicate that Fe-containing composites achieve better wave absorption performance than NiFeG6.14Na (1.57%) and CoFeG6.14Na (1.81%). Overall, Fe-based composites demonstrate superior magnetic and EMI shielding properties, making them more effective for absorption-based applications.