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This paper describes attenuation measurement using the modified micrsotrip line technique from new microwave substrate material. The magnitudes of the transmission coefficient (S21) from the microstrip measurement were used to determine the attenuation of the ZnO/PCL nanocomposites substrate with respect to different percentages of ZnO nanoparticles filler. Result from the measurement showed amongst others that as the filler content increases, the attenuation increases. The highest magnitude for attenuation was calculated for the 70% ZnO nano filler with a value of 14.92 dB and the least attenuation was calculated for the 25% ZnO nano filler, which value gave 6.72 dB which is very good for shielding applications. Transmission electron microscope (TEM) was used to analyse the average particle size of the ZnO powder used as filler in the study. The analysis showed that the average partcile size was 52.7 nm.

Short fibres are often used as reinforcing materials with thermoplastic polymers to improve the dielectric properties of the composites. In this work, the effects of oil palm empty fruit bunch (OPEFB)-fibre loading on polycaprolactone (PCL) polymer were extensively studied. The synthesis of OPEFBPCL composites were prepared via melt blend method. Theoretical and experimental analysis of electromagnetic (EMI) propagation, absorption and shielding effectiveness (SE) properties of the composite were also studied. The magnitudes of Sparameters for OPEFB fiber-reinforced PCL composites with different percentages of filler were measured by a rectangular waveguide connected with a microwave vector network analyzer (VNA) at (8-12) GHz frequency. Whilst the dielectric properties were studied using an open ended coaxial probe. The morphological characterization of the OPEFBPCL composite was carried out using X-ray diffraction and scanning electron microscopy (SEM). This work showed that XRD profile patterns slightly changed duo to the filler loading increment which result a reduction in both dielectric constant and loss factor. However, the relative permittivity of pure oil palm fibre and PCL was measured as (1.8-j*0.08) and (2.929j*0.3242) respectively. In addition, the composition of 12.5 wt% filler gave the highest dielectric constant and loss factor values. However, the reflection loss increases to filler content increments at the maximum frequency of 12 GHz-The excellent behavior of these polymer composites makes them superior nominees for microwave low absorption materials.

In designing filters and antenna feeds at microwave frequency, the energy density and stop bands are of vital importance. To this development, this work is set out to determine the transmission coefficients behavior of substrates along with their energy density for a microstrip structure using finite element method (FEM) and Vector network analyzer (VNA). In this work, a 15, 30 and 50 mm PTFE samples were used as an overlay substrate material on a patch microstrip antenna. Simulations and measurement were then carried using FEM and VNA, respectively. Transmission coefficient obtained via FEM and VNA were compared and the behavior of the substrates at 10 GHz were noted which is the area of broad stop band. Results from simulation and measurement showed that the energy density of the 50 mm thick substrates was 1.67 x 10-5 J/m3 while the attenuated power for the 15, 30 and 50 mm thick substrates at 10 GHz were 6.8, 8.0 and 14.6 dB, respectively. Based on these findings, it is concluded that the 50 mm thick PTFE substrates has the deepest stopband at 10 GHz and more suitable for filter designs and antenna feeds.

PTFE samples were prepared with different thicknesses. Their electric field intensity and distribution of the PTFE samples placed inside a rectangular waveguide were simulated using finite element method. The calculation of transmission/reflection coefficients for all samples thickness was achieved via FEM. Amongst other observable features, result from calculation using FEM showed that the attenuation for the 15 mm PTFE sample is −3.32 dB; the 30 mm thick PTFE sample has an attenuation of 0.64 dB, while the 50 mm thick PTFE sample has an attenuation of 1.97 dB. It then suffices to say that, as the thickness of the PTFE sample increases, the attenuation of the samples at the corresponding thicknesses increases.

This study involves an investigation to ascertain the effect of sintering temperature on the particle size distribution of Co0.5Zn0.5Fe2O4 nano-particle. The effect of the sintering temperature towards diffusion of CoO and ZnO into the tetrahedral and octahedral sites was also reported. In this study, CoO, ZnO and Fe2O3 powders were mechanically alloyed to synthesize fine powders of Co0.5Zn0.5 Fe2O4 nano-particles. The synthesized powder was then sintered at various temperatures which were employed to study the effect of sintering temperature on the materials. Further analysis was done using XRD to investigate the phases of the powder and the crystallite size using Scherrer equation, SEM and EDX for the morphology and elemental composition of samples. The XRD spectra indicated that Both ZnO and CoO powder reacted well during sintering, however, ZnO was first to diffuse into its crystallographic sites before CoO. While the particle size distribution increases as the sintering temperature increases. Amongst other findings, it was confirmed that sintering temperature affects the particle size distribution of samples and samples begin to agglomerate at temperature above 700˚C.

In industrial equipment and home appliance applications, the electromagnetic compatibility compliance directive (ECCD) demands that electromagnetic interference side effects be eliminated or marginally minimized. The equipment must not disturb radio and telecommunication as well as other appliances. Additionally the ECCD also governs the immunity of such equipment to interference and seeks to ensure that this equipment is not disturbed by radio emissions when used as intended. Many types of absorbing materials are commercially available. However, many are expensive and not environmentally friendly. It is in the light of the above that we studied the electromagnetic absorption properties of ZnO-PCL nanocomposites prepared from cheap and abundant resources which are environmentally friendly (zinc and polycaprolactone). The test was carried out using a microstrip, open ended coaxial probe, and vector network analyzer. Amongst other findings, result showed that the ZnO-PCL nanocomposite has the capability of attenuating microwave frequency up to −18.2 dB due to their very high specific surface areas attributed to the nanofillers at 12 GHz.

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