Applied Mechanics and Materials Vol. 815

Abstract: In this work, the effect of PMMA in low density polyethylene/water hyacinth fibers composites were prepared and characterized in terms of tensile properties and FTIR characteristics. Water hyacinth fibers (WHF) were incorporated into the LDPE matrix with different fiber loading. LDPE/WHF and LDPE/WHF_PMMA composites were prepared with Z-blade mixer at 180 °C with rotor speed of 50 rpm. The PMMA modified WHF increased the tensile strength and Young’s modulus while reduced the elongation at break of LDPE/WHF_PMMA composites in comparison with LDPE/WHF composites. The absorption peak at 1736.28 cm^-1 indicated the presence of ester carbonyl group (C=O) in LDPE/WHF_PMMA composites.

Abstract: Milling sugarcanes to produce sugar generates by-product called bagasse. Due to the large availability and low cost, the potential of obtaining renewable and biodegradable fibers from bagasse had been explored. To produce fibers from these bagasse, the bagasse was treated in alkali solution using 14 % v/v calcium hydroxide, Ca (OH)₂ at high temperature (60-70°C) for 4 hours. After treatment and washed to remove dissolved substances, the fibers were cut into 3 and 5 cm length. Some fibers were prepared in their original length. These fibers were mixed with polypropylene (PP) matrix in weight % ratios of bagasse fibers/PP 20/80, 25/75, and 30/70 and hotpressed to make composite samples. Composites produced were characterised with tensile test to evaluate their tensile properties. Scanning electron microscopy (SEM) was performed on the fiber surface as well as on the fracture area of the tensile tested samples. Tensile strength of the composite shows an increase with the increase of the fiber length and weight % ratios of bagasse fibers/PP up to 25/75 and decreases when bagasse fibers were added to 30 wt.%. The highest strength of 11,30 MPa was obtained when 5 cm fibers were used in a weight % ratio of bagasse fibers/PP at 25/75. SEM study found a greater number of fibers oriented perpendicular to the tension direction.

Abstract: Kenaf is renowned for its renewable and environmental friendly properties. Recently, there is an interest on the application of kenaf-based material for high-end uses such as in the automotive industry. In this study, the effects of oil palm shell powder (OPSP) addition on the mechanical properties of kenaf reinforced polypropylene (PP) composites are investigated. Two types of kenaf are used in this study, i.e., non-woven and short fiber. For the former, the composites are fabricated by hot pressing a non-woven kenaf sheet sandwiched by thin PP sheets which have been mixed beforehand with OPSP by using internal mixer. For the latter, kenaf short fibers are mixed with OPSP using internal mixer, then compression molded by using hot press. In general, addition of OPSP was effective to improve the mechanical properties of non-woven kenaf reinforced PP composites, while the kenaf short fiber reinforced PP showed varied results. Composites reinforced with non-woven kenaf showed a larger increase in tensile strength, elongation at break and impact strength with the OPSP addition than those reinforced by kenaf short fibers.

Abstract: Technology for surface protection in contact with seawater has been studied. It mainly focuses on the capability of superhydrophobicity characteristic. Currently, the application of superhydrophobicity in controlling corrosion problem in the marine environment is still new. The development of superhydrophobicity on the materials surface can be achieved by designing a specific texture pattern in micro-or nanometer scale for producing high roughness surface. This review paper is mainly on the laser technology for producing superhydrophobicity characteristic of materials surface. This technique offers the most control and precision over the produced geometry.

Abstract: In this work, the characterization of porous silicon (PS) for potential visible light emission was investigated by simulation. SILVACO TCAD simulator was used to simulate PS by using process simulator, ATHENA and device simulator, ATLAS. Different pore diameter sizes of the PS structures were constructed. The structural, optical and electrical characteristics of the structures PS were investigated by current-voltage (I-V), current gain, spectral response and the energy band gap. It was observed that PS enhances the current gain compare to bulk Si and exhibited photo emission in the visible spectrum which constitutes to the quantum confinement effect of the Si in the PS structures.

Abstract: Undoped barium titanate and lanthanum (La) doped barium titanate (BaTiO₃) were studied for ferroelectric properties with the formula of Ba_1-xLa_xTi_1-x/4O₃ for x=0.1 and being prepared by using conventional solid state method reaction. The pure phase of this composition which x=0 were found at final heating temperatures starting from 1300°C and x=0.1 at 1350°C for overnight in air with intermittent grinding. The changes in the crystal structure of the composition were detected by using X-ray diffraction. Impedance Spectroscopy analysis is carried out to determine the dielectric properties for undoped BaTiO₃ and La doped BaTiO₃ for x=0.1.

Abstract: — Barium titanate (BaTiO₃) thin films are suitable for many application especially photonics. BaTiO₃ thin films are deposited using spin coating with an optimum spin speed of 4500rpm. The samples are then characterized using XRD, AFM and SEM. The results of the XRD analysis showed that both the 5-and 10-coated layers are polycrystalline BaTiO₃ with differences in terms of diffraction intensity, due to the number of layers. As for optical application, the surface roughness is the most crucial part. The number of layers of 5 and 10 have thickness of 2.927nm and 4.456nm RMS.

Abstract: Graphene sheets offer extraordinary thermal, electronic and mechanical properties which could enhance the performance of the device for various applications. However, a large quantity production and the direct dispersion of graphene or graphite sheets in water without the assistance of dispersing agent has been considered to be a challenging issue. In this study, we reported that by introducing the functional group on the graphene basal plane started from natural graphite can readily form stable graphene oxide (GO) solution in a large quantity through modified hummers method. Structural and physiochemical properties of the GO were investigated with help of Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR). The effects of the annealing treatment on a GO surface were analyzed using a Semiconductor Parameter Analyzer (SPA) in order to obtain the electrical resistance measurement. Based on the thermal reduction results, the resistance of drop casting is greater than spray coating which indicates that, the drop casting method is more reliable to be used in any application.

Abstract: The objective of this study is to investigate the fire retardancy effect of coconut coir, rice husk and sawdust panels which are incorporated with magnesium hydroxide (Mg (OH)₂) and zinc borate (2ZnO∙3B₂O₃∙3.5H₂O) as additives. The natural fiber and additives are mixed and cured for one week, with polyester resin and hardening catalyst as binders. Fire retardancy of these panels are tested according to American Society for Testing and Materials (ASTM) Horizontal (D 365) and Vertical Burning (D 3801) tests. Principle of fire retardants and mechanism of polymer combustion are shown in this study too. The study revealed that the sawdust panels with both additives have the highest fire retardancy compared to rice husk and coconut coir panel with both additives.

Abstract: The use of fly ash as an alternative material for cement substitute in concrete mix already a common practice nowadays. However, as a waste material, fly ash varies in quality and condition, as shown by variation of its fineness, specific gravity, Loss on Ignition (LOI) and also on its chemical composition. By measuring the acidity (pH) of the fly ash in water solution, percentage of mass retained on 45 μm sieve, and superplasticizer demand of the fly ash, we can develop a quick estimation of the quality of fly ash. This study aims to investigate a quick method to estimate the quality of fly ash by measuring the physical and chemical pointers, as indicator for its properties and the effect on the setting time and compressive strength of mortar. Fly ash content was varied from 0-70% of the total mass of cementitious materials to make HVFA mortar. Fly ashes were obtained from four power plants in Indonesia. Tests conducted were material characterization, setting time, temperature rise, and compressive strength of mortar at different ages. Different fly ash quality can be shown by the fast pointers; namely pH, superplasticizer demand and % retained on 45 μm sieve. Setting time and strength development were affected by the different properties of fly ash.