Microwave assisted magnetite carbon dots for enhanced the thermal aging resistance, magnetic and dielectric properties of acrylonitrile butadiene rubber composites

Magnetic carbon dots (Fe 3 O 4 /N–CQDs) were synthesized via a one-step microwave-assisted method using sugarcane bagasse as the carbon precursor. The synthesized materials were thoroughly characterized via thermogravimetric analysis (TGA/DTG), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and transmission electron microscopy (TEM) to examine their thermal behavior, nanoscale morphology, and phase composition. These Fe 3 O 4 /N–CQDs were incorporated into acrylonitrile butadiene rubber (NBR) at varying concentrations (0–11 phr), and the resulting composites were evaluated for their structural characteristics (FTIR, SEM), thermal stability, curing behavior, mechanical performance, swelling resistance, thermal aging resistance, as well as magnetic, and dielectric properties. Among the formulations studied, the composite containing 8 phr Fe 3 O 4 /N–CQDs showed the most balanced performance, with tensile strength increasing from 2.3 to 4.2 MPa and hardness from 54 to 65 Shore A. Post-aging analysis revealed improved tensile strength and reduced swelling, attributed to enhance crosslinking. The composites demonstrated superior thermal aging resistance under accelerated aging at 110°C for 10 days. Magnetic measurements indicated soft magnetic behavior, with saturated magnetization increasing from 29.05x 10 −3 emu/g (0 phr) to 91.32 × 10 −3 emu/g (11 phr) and coercivity below 120 G, while dielectric and conductivity studies showed frequency-dependent permittivity and conductivity consistent with interfacial polarization and hopping mechanisms. These results demonstrate that Fe 3 O 4 /N–CQDs can simultaneously enhance the thermal, mechanical, antiaging, magnetic, and dielectric properties of NBR compounds.