GO@CNT@Fe₃O₄@CuO Quaternary Nanohybrids: Enhanced Dielectric-Magnetic Synergy for High-Performance Epoxy-Based Electromagnetic Absorbers
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As awareness of electromagnetic interference (EM) grows, so does the demand for materials capable of absorbing EM waves. In this study, the GO@CNT@Fe 3 O 4 @CuO core-shell nanohybrid was fabricated using coprecipitation for Fe₃O₄ and in-situ thermal synthesis for CuO nanoparticles and then used as a novel electromagnetic (EM) absorber to create an epoxy-based nanocomposite for absorbing EM waves. The quaternary architecture uniquely integrates dielectric (GO, CNT), magnetic (Fe₃O₄), and semiconducting (CuO) components in a core-shell structure, enabling synergistic loss mechanisms and superior impedance matching compared to binary or ternary systems. Various characterization techniques, including FTIR, TGA, XRD, TEM, and SEM, confirmed the successful synthesis of the GO@CNT@Fe 3 O 4 @CuO nanohybrid. Next, multiple nanofillers, including GO@CNT, GO@CNT@Fe 3 O 4 , and GO@CNT@Fe 3 O 4 @CuO, were incorporated to modify the electromagnetic absorption properties of the epoxy matrix. All EM absorber features—reflection loss (RL), complex permittivity (εr = ɛ́ - jɛ̋), and permeability (μr = μ́ - jμ̋)—were evaluated using a vector network analyzer (VNA). During testing, key factors like nanofiller concentration, type, and the epoxy nanocomposite’s thickness were examined to identify optimal conditions for the EM absorber nanocomposite. Based on VNA results, the GO@CNT@Fe 3 O 4 @CuO-filled epoxy nanocomposite was deemed the best performer. The enhanced EM absorption is attributed to the combined dielectric and magnetic loss properties of the GO@CNT@Fe 3 O 4 @CuO nanohybrid. For the GO@CNT@Fe 3 O 4 @CuO nanocomposite, labeled as the E-GO@CNT@Fe 3 O 4 @CuO sample, the optimal concentration was 5 wt.%, with an RL of -37.5 dB, a nanocomposite thickness of 5.0 mm and an EAB of 3.2 GHz (9.0–12.2 GHz). For the optimal nanocomposite, the Real complex permittivity (ɛ́) and imaginary complex permittivity (ɛ̋) were measured as 6.1 and 2.6 with uncertainty ±0.2 and ±0.1, respectively. These values markedly enhanced absorption properties compared to the control sample, which was epoxy resin without any nanofillers. Consequently, we conclude that the synthesized GO@CNT@Fe 3 O 4 @CuO nanohybrid is an effective EM absorber. This performance surpasses many binary and ternary carbon-based composites at similar thicknesses and loadings, such as GO@CNT@Fe₃O₄ (-25 dB) and MWCNT/CuO/Fe₃O₄/PANI (-87.4 dB but at 15 wt.% and 2.5 mm), highlighting the efficiency of the quaternary design at low loading.
