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Microwave absorption properties of Epoxy/Nickel Ferrite (NiFe2O4) and Epoxy/Barium Titanate (BaTiO3) composites were investigated and compared in the 1–14 GHz. Epoxy/filler particles (NiFe2O4 and BaTiO3) composites were prepared with 85/15 mixture ratios via Ultrasonic Probe Sonicator method in solution. The complex permittivity ( ɛ′‐ ɛ″) and permeability ( μ′‐ μ″) of the composites have been measured at different microwave frequencies in 1–14 GHz via vector network analyzer (Keysight N9926A). The reflection loss (RL) of composites was calculated and evaluated from camplex permitivity and permeability. The obtained results show that both composites exhibit the large RL and broadband within the frequency range from 1 to 14 GHz for different thickness. Epoxy/BaTiO3 showed a better microwave absorption at the range of 6–7.2 GHz for 7 and 6 mm, at the range of 7.4–9.1 GHz for 5 mm. However, the Epoxy/NiFe2O4 exhibits the largest RL and the widest bandwidth than those obtained from Epoxy/BaTiO3 composite. POLYM. COMPOS., 39:E2143–E2148, 2018. © 2017 Society of Plastics Engineers

The present study aims to produce graphene nanoplatelet-coated B4C ceramic particle using semi-powder method and to investigate the effect of graphene nanoplatelets on wear and corrosion performance of Al–Si-based metal matrix hybrid composites. For this purpose, first graphene nanoplatelets at different ratios (0.25, 0.5, and 1 vol.%) were coated to the surfaces of B4C particles and then the Al–Si alloy was infiltrated into the reinforcements by gas pressure infiltration method. The characterization of graphene nanoplatelet-coated B4C powders and its composites was carried out by X-ray diffraction, differential scanning calorimetry, scanning electron microscope, and transmission electron microscope analysis. Tribological properties were investigated by reciprocating ball-on-flat method under three different loads (10–20–40 N) in a dry environment. The corrosion resistance was carried out with Tafel polarization method in 3.5% NaCl solution. Characterization results show that graphene coated on the B4C surface was successfully achieved by semi-powder method. After infiltration process, a new phase formation was not observed, but porosity increased with the increase of graphene content. When the boron carbide surface was coated with 0.5vol.% graphene, it was determined that the specific wear resistance increased by 55% and the corrosion resistance decreased by 12%.

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