Search

The development of microwave shielding nanocomposites based on recycled hematite nanoparticles, oil palm empty fruit bunch (OPEFB), and polytetrafluoroethylene (PTFE) was the main focus of this study. The complex permeability (μ′–jμ″), complex permittivity (ε′–jε″), reflection coefficient (S11), and transmission coefficient (S21) were determined using rectangular waveguide (RWG) connected to a vector network analyzer (VNA) in the frequency range of 8.2–12.4 GHz. The power loss, reflection loss, and total shielding effectiveness (SE) were calculated using the scattering parameters obtained through RWG. The results showed that the nanocomposites' microwave shielding properties can be controlled by tuning the percentage of Fe2O3 nanofiller in the nanocomposites. The values of ε′, ε″, μ′, and μ″ were enhanced by increasing the content of the recycled Fe2O3 nanofiller in the nanocomposites. At 10 GHz, the power loss values obtained for the nanocomposites ranged between 8.52 and 15.64 dB, while at 12.4 GHz, a maximum value of 16.32 dB was achieved by 25 wt%. nanocomposite. The total SE also increased with increasing Fe2O3 loading and a maximum value of 21.2 dB was achieved by 25 wt% nanocomposite at 12.4 GHz. The Fe2O3‐OPEFB‐PTFE nanocomposites have the potential to be used in microwave shielding applications in the frequency range 8.2–12.4 GHz. [ABSTRACT FROM AUTHOR]

Low dielectric loss and low-cost recycled borosilicate (BRS) glass-reinforced polytetrafluoroethylene (PTFE) composites were fabricated for microwave substrate applications. The composites were prepared through a dry powder processing technique by dispersing different micron sizes (25 µm, 45 µm, 63 µm, 90 µm, and 106 µm) of the recycled BRS filler in the PTFE matrix. The effect of the filler sizes on the composites' thermal, mechanical, and dielectric properties was studied. The dielectric properties of the composites were characterised in the frequency range of 1–12 GHz using an open-ended coaxial probe (OCP) connected to a vector network analyser (VNA). XRD patterns confirmed the phase formation of PTFE and recycled BRS glass. The scanning electron microscope also showed good filler dispersion at larger filler particle sizes. In addition, the composites' coefficient of thermal expansion and tensile strength decreased from 12.93 MPa and 64.86 ppm/°C to 7.12 MPa and 55.77 ppm/°C when the filler size is reduced from 106 μm to 25 μm. However, moisture absorption and density of the composites increased from 0.01% and 2.17 g/cm3 to 0.04% and 2.21 g/cm3. The decrement in filler size from 106 μ m to 25 μ m also increased the mean dielectric constant and loss tangent of the composites from 2.07 and 0.0010 to 2.18 and 0.0011, respectively, while it reduced the mean signal transmission speed from 2.088 × 108 m/s to 2.031 × 108 m/s. The presented results showed that PTFE/recycled BRS composite exhibited comparable characteristics with commercial high-frequency laminates. [ABSTRACT FROM AUTHOR]

The purpose of this study was to improve the dielectric, magnetic, and thermal properties of polytetrafluoroethylene (PTFE) composites using recycled Fe2O3 (rFe2O3) nanofiller. Hematite (Fe2O3) 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 rFe2O3 nanoparticles were incorporated as a filler in the PTFE matrix through a hydraulic pressing and sintering method in order to fabricate rFe2O3–PTFE nanocomposites. The microstructure properties of rFe2O3 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 (ε′) and imaginary (ε″) parts of permittivity increased with the rFe2O3 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 − j 0.07 was also achieved by 25 wt % nanocomposite at 10 GHz. [ABSTRACT FROM AUTHOR]