Abstract:The dielectric and magnetic behaviour and thermal properties of composites based on nickel-zinc ferrite (NZF) filler can be improved by the addition of various types of materials. Amongst others, ferrite-polymer composites have been subjected to a wide range of research, due to their extensive applications: electromagnetic interference shielding, microwave absorption, electrodes and sensors. Currently, the interest in scientific and technical searches for the potential outcomes of ferrite-polymer materials due to their different uses in applications such as telecommunication applications, microwave devices and electromagnetic interference shielding has been growing stronger. The dielectric and magnetic behaviour and thermal properties for such composite materials depend on size, shape and the amount of filler addition. Nickel-zinc ferrite material was prepared using the conventional solid-state reaction technique. This study highlights the development of microwave-absorbing material from NZF by adding natural fibres, Oil Palm Empty Fruit Bunch (OPEFB) and polycaprolactone (PCL). OPEFB is considered in this study because it is a solid waste product of the oil palm milling process which is widely and cheaply available. The use of OPEFB in this product may save the environment from oil palm solid waste. A Thermal Hake blending machine was used in blending the powder structure of NZF + OPEFB + PCL, which made it homogeneous. These composites were characterized by the use of Fourier transform infrared (FTIR) spectrometry and scanning electron microscopy (SEM). The thermal degradation behaviour of the composites was analyzed using thermogravimetric analysis (TGA) and differential thermogravimetric (DTG) thermograms. The effective permittivity and effective permeability was obtained over a broad frequency range from 8 to 12 GHz at room temperature. It was observed that the values of effective permittivity and permeability increased as the content of NZF content increased. A rectangular waveguide connected to a microwave vector network analyser (PNA) (HP/Agilent model PNA E8364B) was employed in measuring the reflection coefficient S 11 and transmission coefficient S 21 parameters of composites for different percentages of NZF filler. This parameter was then used in calculating the microwave absorbing properties (dB).
Bio-composites of oil palm empty fruit bunch (OPEFB) fibres and polycaprolactones (PCL) with a thickness of 1 mm were prepared and characterized. The composites produced from these materials are low in density, inexpensive, environmentally friendly, and possess good dielectric characteristics. The magnitudes of the reflection and transmission coefficients of OPEFB fibre-reinforced PCL composites with different percentages of filler were measured using a rectangular waveguide in conjunction with a microwave vector network analyzer (VNA) in the X-band frequency range. In contrast to the effective medium theory, which states that polymer-based composites with a high dielectric constant can be obtained by doping a filler with a high dielectric constant into a host material with a low dielectric constant, this paper demonstrates that the use of a low filler percentage (12.2%OPEFB) and a high matrix percentage (87.8%PCL) provides excellent results for the dielectric constant and loss factor, whereas 63.8% filler material with 36.2% host material results in lower values for both the dielectric constant and loss factor. The open-ended probe technique (OEC), connected with the Agilent vector network analyzer (VNA), is used to determine the dielectric properties of the materials under investigation. The comparative approach indicates that the mean relative error of FEM is smaller than that of NRW in terms of the corresponding S21 magnitude. The present calculation of the matrix/filler percentages endorses the exact amounts of substrate utilized in various physics applications.
Basic research on recyclable, renewable and biodegradable polymer composite materials reinforced with natural fibers is increasingly growing. In this article, we characterize agricultural waste by determining its dielectric properties for microwave absorber application. Recently, polymer composites reinforced with natural fibers are increasingly used in dielectric and aircraft applications. We used a Thermal Hake blending machine to blend oil palm empty fruit bunch with polycaprolactone grain to make a homogeneous powder. The functional groups of the resulting composites were then analyzed through Fourier transform infrared spectrometry. Thermogravimetric and differential thermogravimetric analyses were performed to determine the thermal degradation behaviors of the composites. The tensile strength, tensile modulus and elongation at break of the composites were measured in an Instron universal testing machine. A rectangular waveguide and open‐ended coaxial probe connected to a microwave network analyzer (PNA) Agilent N5230A PNA‐L was used to measure the reflection coefficient S11 and transmission coefficient S21 values and the dielectric properties of the composite materials. Results showed that the thermal stability and dielectric properties of the polymer composites decreased as the fiber content increased. The composites exhibited potential as microwave absorbers at microwave frequencies. POLYM. COMPOS., 39:E1778–E1787, 2018. © 2018 Society of Plastics Engineers
Fabrication of hybrid composite of nickel oxide (NiO) combined with oil palm empty fruit bunch (OPEFB) reinforced with polycaprolactone (PCL) has been done by using thermal Haake blending machine, which ensured mixture homogeneity. All hybrid composites' characterizations were carried out using X‐ray diffraction (XRD), Fourier transform infrared spectrometry, differential thermogravimetry, thermogravimetric analysis, and scanning electron microscopy. The results showed that the XRD profile patterns of the composites clearly changed as the filler loading amount was increased. Fourier transform infrared spectra illustrated a slight change in the frequencies and positions of the peaks after adding NiO, indicating that some interactions occurred between C=O and O–H or among the fiber, NiO, and PCL. The microwave electromagnetic properties, such as reflection loss (dB), relative complex permittivity (εr =εr′–jεr″), and permeability (μr=μr′−jμr″) were calculated at various microwave frequencies in the X‐band (8–12 GHz) range. It was observed that the thermal stability, magnetic, and dielectric properties of NiO:OPEFB:PCL composites were modified significantly with NiO addition. This enables the new hybrid composites to be used as engineering materials in the microwave applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 46998.
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