Effects of Recycled FeO Nanofiller on the Structural, Thermal, Mechanical, Dielectric, and Magnetic Properties of PTFE Matrix.

The purpose of this study was to improve the dielectric, magnetic, and thermal properties of polytetrafluoroethylene (PTFE) composites using recycled FeO (rFeO) nanofiller. Hematite (FeO) was recycled from mill scale waste and the particle size was reduced to 11.3 nm after 6 h of high-energy ball milling. Different compositions (5-25 wt %) of rFeO nanoparticles were incorporated as a filler in the PTFE matrix through a hydraulic pressing and sintering method in order to fabricate rFeO-PTFE nanocomposites. The microstructure properties of rFeO nanoparticles and the nanocomposites were characterized through X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM). The thermal expansion coefficients (CTEs) of the PTFE matrix and nanocomposites were determined using a dilatometer apparatus. The complex permittivity and permeability were measured using rectangular waveguide connected to vector network analyzer (VNA) in the frequency range 8.2-12.4 GHz. The CTE of PTFE matrix decreased from 65.28×10-6/°C to 39.84×10-6/°C when the filler loading increased to 25 wt %. The real (') and imaginary (″) parts of permittivity increased with the rFeO loading and reached maximum values of 3.1 and 0.23 at 8 GHz when the filler loading was increased from 5 to 25 wt %. A maximum complex permeability of 1.1-j0.07 was also achieved by 25 wt % nanocomposite at 10 GHz.