Microwave Assisted Magnetite Carbon Dots for Enhanced the Thermal Aging Resistance, Magnetic and Dielectric Properties of Nitrile Rubber (NBR) Composites

Magnetic carbon dots (Fe₃O₄/N–CQDs) were synthesized through a single-step, microwave-assisted approach using sugarcane bagasse as a renewable carbon source. The synthesized nanomaterial was thoroughly characterized via thermogravimetric analysis (TGA/DTG), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and transmission electron microscopy (TEM) to confirm its structural, chemical, and morphological attributes. These Fe₃O₄/N–CQDs were incorporated into nitrile butadiene rubber (NBR) at varying concentrations (0–11 phr), and the resulting nanocomposites were evaluated for their structural integrity (FTIR, SEM), curing behavior, mechanical performance, swelling resistance, thermal aging stability, and electromagnetic properties. The formulation containing 8 phr Fe₃O₄/N–CQDs exhibited optimal enhancement, with tensile strength increasing from 2.3 to 4.2 MPa and hardness rising from 54 to 65 Shore A. Post-aging analysis revealed improved tensile strength and reduced swelling, attributed to enhance crosslinking and interfacial interactions. The nanocomposites demonstrated superior thermal stability under accelerated aging at 110°C for 10 days, and the embedded magnetic domains contributed to improved magnetic and dielectric behavior as well. This study underscores the multifunctional potential of biomass-derived Fe₃O₄/N–CQDs as sustainable, high-performance additives for advanced rubber technologies.