Surface functionalization of diazonium-treated hybrid fillers for enhanced electromagnetic interference properties in epoxy composites

The increased integration and miniaturization of electronic devices have brought significant challenges in managing internally generated heat and suppressing electromagnetic interference (EMI), both of which can critically affect device reliability, performance, and lifespan. Although thermal interface materials (TIMs) and EMI shielding films have been used to address these challenges independently, such multilayered approaches are often hindered by interfacial thermal boundary resistance, secondary EMI caused by reflection, increased weight, and the risk of corrosion. Hence, the present study reports a novel multifunctional epoxy-based composite that incorporates diazonium-functionalized carbonyl iron (CI) particles that were surface-modified using a diazonium salt of 5-amino salicylic acid (D-CI) and a three-dimensional (3D) porous reduced graphene oxide aerogel (rGOA) for simultaneously addressing the heat dissipation and EMI shielding challenges. The surface modification of CI via aryl diazonium chemistry enables the formation of covalently bonded aromatic layers that effectively suppress particle agglomeration and improve the interfacial compatibility with the polymer matrix. The introduction of π-electron-rich structures further extends π–π electron transfer pathways, thereby facilitating interfacial charge transport between metallic components and contributing to the enhancement of electrical conductivity. In addition, improved dispersion and filler–filler connectivity promote the formation of continuous thermal conduction pathways, thereby resulting in higher thermal conductivity. Demonstrating excellent integrated performance, the D-CI/rGOA/epoxy composite delivered thermal and electrical conductivities of 4.48 W/m·K and 59.1 S/cm, respectively, while its EMI shielding effectiveness reached as high as 74.4 dB. Thus, the proposed strategy offers strong potential for use in next-generation electronic packaging.