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An absorber with lightweight, low-cost, high absorption and broad frequency bandwidth is highly expected to design an electromagnetic wave absorber application. In this paper, the carbon materials based agricultural waste from oil palm empty fruit bunch (OPEFB) were studied to investigate the electromagnetic wave, especially the microwave absorption properties within the range from 8 to 12 GHz (X-band). The carbon-based OPEFB is prepared by hydrothermal carbonization (at 180 oC for 8 hours) followed by chemical (using KOH activating agent) and physical (at 800 oC for 2 hours) of carbonization processes. We studied the microwave absorption properties of the porous carbon-based OPEFB with 20 % of KOH concentration. A vector network analyzer (VNA) takes the microwave absorption properties within the X-band frequency range. The results indicate the ability to absorb electromagnetic waves in all X-band frequencies for porous activated carbon-based OPEFB samples. The reflection loss is reach -32.21 dB at 10.64 GHz. The enhancement of EM wave absorption in activated carbon-based OPEFB compared to that of raw OPEFB material is correlated to the formation of porous stracture inducing the multiple reflection to enhance the interfacial polarization of EM wave. This research show that the porous carbon-based OPEFB can be a promising candidate for a lightweight, green, and renewable of electromagnetic waves absorber in the future. [ABSTRACT FROM AUTHOR]

Natural fibers are abundant in Indonesia, coconut fiber (Cocos nucifera) is used as an insulation composite for wall fillers. In general non-natural materials such as glass wool, polyurethane, fiberglass, polyimide foam, and other synthetic materials are still used as substitutes for insulation, which has been using synthetic materials since the use of coconut fiber as agricultural waste. This research is to analyze the quality of the fiberboard's physical and mechanical properties. To know quality product physical and mechanical tests such as density, moisture content, water absorption, thickness expansion, compression, and bending (standardized using JIS A 5905 2003) and morphological analysis were carried out to determine visual characterization using a 3D keyence microscope on a fiberboard. Making a test sample with a size of 210 x 120 x 5 cm, coconut fiber is mixed with polyurethane adhesive with a density variation of 0.04, 0.06, 0,08, and 0.1, then cold-pressed at a pressure of 5 kg/cm2 for 2 hours because the polyurethane adhesive is thermosetting, and then cut to a size of 30 x 30 cm. The results showed that the higher the density of the fiberboard, the better the physical and mechanical properties. A density of 0.1 g/cm3 produces the best mechanical properties. [ABSTRACT FROM AUTHOR]

Hydrophilic cotton fabric (WCA = 68°) was successfully converted to superhydrophobic (WCA > 150°) by coating the surface with ZnO nanoparticles (NPs) using the hydrothermal method without additional reagent. We noted that the ZnO particle size, as well as the sample surface density, increased with the higher precursor concentrations, forming hierarchical morphology. Interestingly, the coexistence of the excitonic state (∼ 4 eV) and the defect state (2 - 3.2 eV) was observed, which has the potential for developing a water-repellent and anti-bacterial surface. The role of morphology on absorption and wettability properties is then studied comprehensively. Our results can be used as a strategy for designing water-repellent and anti-bacterial coatings for medical and textile applications. [ABSTRACT FROM AUTHOR]

Zinc oxide nanorods/Graphene (ZnO NRs/Gr) were synthesized using an easy and fast method; spray for ZnO seed and graphene deposition and hydrothermal for ZnO NRs. The sample was varied by using different ZnO seed precursor of 0.1 M, 0.2 M, and 0.3 M. We found that the greater the concentration of ZnO led to a decrease in porosity, accompanied by an increase in the water contact angle of 150°, 153°, and 155°. The XRD results confirmed that there was no shift in the ZnO peak, which indicated that there was no significant structural change due to the lattice strain. UV-Vis analysis obtained a band gap of ∼3.4 eV and an excited state of ∼4 eV. Based on the results obtained, ZnO NRs/Graphene can be a promising waterproof coating material on cotton fabrics. [ABSTRACT FROM AUTHOR]

The development of particleboard made from non-wood lignocellulose materials and natural adhesives has become intensive research due to the lack of wood supply and fossil resources. In this study, coconut husk and citric acid were used as the raw material and natural adhesive for new generation of particleboards. The effect of particles size and citric acid content in the physical properties of the particleboards were investigated. The particles sizes of coconut husk were divided into 3 sizes of mesh such as 4, 10, and 14 while citric acid content was varied in the range of 15 to 25 wt%. Thermo-pressing technique was conducted in 200 °C for 10 min. 300 mm x 300 mm x 9 mm board size was formed for 0.8 g/cm3 target density. The physical properties of particleboards are improved from smaller to bigger particle size (4 to 14 mesh) proportional to the increment of citric acid content until 20 wt%. Type 18 JIS A 5908 (2003) standard was satisfied in physical properties of particleboards for 14 mesh of particles and 25 wt% citric acid binder. Consequently, it was concluded that 14 mesh of the particles size and a citric acid content of 25 wt% were effective in manufacturing particleboards composed of coconut husk and citric acid. [ABSTRACT FROM AUTHOR]

We have investigated optical properties of Ta-doped TiO2 thin film on LaAlO3 (LAO) substrate using Spectroscopic Ellipsometry (SE) at room temperature. Amplitude ratio Ψ and phase difference Δ between p- and spolarized light waves are obtained by multiple incident angles measurement (60°, 70°, and 80°) at energy range of 0.5 - 6.5 eV. In order to obtain optical properties for every Ta concentrations (0.01, 0.4, and 5 at. %), multilayer modelling was performed simultaneously by using Drude-Lorentz model. Refractive index and optical dispersion parameters were determined by Wemple-DiDomenico relation. In general, refractive index at zero photon energy n(0) increases by increasing Ta concentration. Furthermore, optical band gap shows a significant increasing due to presence of Ta dopant. In addition, other optical constants are discussed as well. [ABSTRACT FROM AUTHOR]