Key Engineering Materials Vols. 594-595

Abstract: This paper focuses on the applicability of InN based quantum dot in the active layer of the solar cell to reduce the short circuit current variation above the room temperature. We have investigated numerically the effect of temperature on the short circuit current of the solar cell using InN based quantum dot in the active layer of the solar cell. The numerical results are compared with those obtained by using Ge based quantum dot. The comparison results revealed that the short circuit current has been increased slightly but the variation of short circuit current has been reduced significantly in the case of using InN quantum dot in the active layer of the device structure. As the results, InN can be considered as the best alternative material to fabricate solar cell with higher short circuit current in upcoming decades.

Abstract: The waste material from palm oil industry has been increasing since Malaysia was the world largest exported of palm oil mill. The waste such as palm fibers, nut shells, palm kernel and empty fruit bunches are the solid waste the obtained from palm oil processing for oil extraction. When these wastes were incinerated, the waste from the burning process known as boiler ash was obtained at the lower compartment of the boiler. The production of boiler ash was estimated to be over 4 million tones/ year. This paper investigates the influence of dolomite on the mechanical properties of boiler ash based geopolymer pastes. The boiler ash was calcined at 800oC for 1 hour. After that, the dolomite was replaced in boiler ash at 1, 2, 3, 4 and 5% wt where the geopolymer samples were cured 80 oC. Sodium silicate and sodium hydroxide (NaOH) with concentration 12 Molar has been used as alkaline activator to synthesis the boiler ash to produce geopolymer paste. The ratio of solid/liquid and sodium silicate/NaOH was 1 and 2.5 for all geopolymer paste. The result showed the addition of dolomite has decrease the strength of boiler ash based geopolymer. The geopolymer sample without addition of dolomite showed the maximum compressive strength (19.4 MPa) at 28 days testing. Meanwhile the addition of 4% of dolomite into geopolymer paste has the maximum compressive strength (7.3 MPa) compared to others. Additions of dolomite into boiler ash based geopolymer have reduced the compressive strength at 28 days of testing.

Abstract: LNG plant requires a lot of energy for its production especially in liquefaction process. One of the reasons is due to inefficiency on some of its major equipments, particularly on Main Cryogenic Heat Exchanger (MCHE). The efficiency of this unit can be improved by the usage of Mixed Refrigerant (MR) which matches closely the heating curve between hot and cold stream. However, the study on this refrigerant is complex and tedious due to multi component refrigerant and phase changing process inside MCHE. In this study, effect of varying MR composition towards MCHE performance is analyzed, with focus on heat transfer coefficient in shell side of MCHE. The analysis was based on single and two phase flow conditions which are gas flow and liquid falling film flow. The adjustment of binary components in MR composition was studied for each flow regime. By doing this, the best composition adjustment that gives the highest value of heat transfer coefficient was determined. It was found that the adjustment of methane-propane (C₁-C₃) is the best arrangement for both cases. However, it needs to be tested by applying this to actual process condition, in this case by implementing it in simulated LNG process.

Abstract: Selected ionic liquids are known to enhance the absorption of CO₂ for CO₂ removal purpose. In the idea to improve the membrane separation performance for natural gas sweetening, ionic liquid modified polymeric membranes were fabricated by using polyethersulfone (PES) and blended with different composition of ionic liquid which are 5 wt% and 15 wt%. Each fabricated membranes were prepared and dried under solvent evaporation at 90°C. Dense structure observed from FESEM analysis indicated the miscible blends of ionic liquid and PES. TGA analysis showed all fabricated membranes are still containing solvent and this resembles that membrane drying period is still insufficient. All fabricated membranes were tested with ideal gas permeation test. From the result, the addition of ionic liquid has enhanced the ideal CO₂ pemeance about 150% as compared to pure PES membrane. The ideal CO₂/CH₄ selectivity was also increase about 85% from the base but however, the separation index is still considered low and this may due to the presence of the solvent. This preliminary result has confirmed that the blending of ionic liquid with pure PES membrane has technically improved the membrane separation performance.

Abstract: Foamed Concrete (FC) needs high strength to prevent dynamic loading, thus it is important to enhance the ductility. Usage the Polypropylene Fibre (PF) examined its contribution in strength of FC on impact resistance. Microstructures were observed that air voids in matrix of FC produce micro-porous that reduce interfacial bonding into matrix and generate micro-crack that may propagation crack growth. Presence of PF in admixture results fibrillation and reduces micro-cracks. Tensile test was investigated that PF delays crack growth in matrix. In this investigation impact test were conducted using an instrumented drop-weight impact tower. When impactor hits the target surface in free surface condition causes compressive plastic wave transform to be tensile wave. It was affected by tensile strength therefore local effect has not found spalling in crater field. In addition influence of porous in matrix FC has ability to absorb the energy and it was not found distal crack around surface area. Penetration depth results showed FC with PF subjected to impact loading was lower than without FC. Presence of PF increases FC strength and local effect results there was not impression of fragments around distal surface due to brittle crushing.

Abstract: A Co-Cr-Mo (ASTM CoF-75) alloy is normally used because of their good in physical, mechanical, wear and as well as biocompatibility. In order to obtain similarity chemical structure of bone, addition of HAP or TCP into CoF-75 alloy is required. The samples were fabricated using powder metallurgy (P/M) technique under pressure of 350 MPa and sintered at 1200 °C under argon atmosphere. The results on the effect of different additives were studied in terms of shrinkage, bulk density, apparent porosity and microstructural analysis.

Abstract: Concrete is a structure that very weak in tension and need additional material to enhance their structural capacity. In 18^th century, concrete have been recognized as structure that very weak in tension [. Thus, concrete need additional supporting material that can improve the tension capacity. Because of the steel is very good in tension, the steel bar was embedded in concrete at the tensile stress area to obtain the full capacity of the steel bar as reinforcement.

Abstract: The chemical composition and preparation methods for ferrite were studied in order to control the quality of ferrite such as higher initial permeability and low energy losses. Nine samples of soft ferrite M_xZn_1-xFe₂O₄ with M=Ni, Mg, Cu ; x=0.2, 0.3, and 0.4 was prepared using solid state ceramic method and characterized for initial permeability, coercivity and relative loss factor (RLF). Studies show that samples with low Zn concentration, x=0.4, exhibit higher initial permeability, μ_i, with magnitude highest in sample with Ni concentration, that also has the highest atomic susceptibility among Ni, Mg and Cu. Initial permeability, μ_i ,also influences the resistivity of the samples with increasing susceptibility of magnetic spins, so samples with higher μ_i, e.g. Ni_0.4Zn_0.6Fe₂O₄ exhibit increased resistivity with increased initial permeability while Cu_0.4Zn_0.6Fe₂O₄ exhibit decreasing resistivity with increasing Cu content and lower initial permeability.

Abstract: This paper explains preparation of activated carbon from empty fruit bunch (EFB) using steam activation under optimum conditions; activation temperature of 765°C and activation time of 77min and analyzes their physical and chemical properties using proximate and ultimate analysis, fourier transform infrared (FT-IR) analysis, x-ray diffraction (XRD) analysis, nitrogen adsorption-desorption analysis and scanning electron microscopy (SEM) analysis. Results show activated carbon EFB consists of 68.32 wt% carbon, 3.12 wt% hydrogen, 2.12 wt% nitrogen and 26.44 wt% oxygen content. FT-IR spectroscopy result indicate that raw EFB was successfully converted to carbon after activation process and was proven by spectra of commercial activated carbon. The XRD study confirms the presence of some crystalline (graphite) phase around peaks 26^o and 43^o. Characterization by using BET and SEM analysis showed that activated carbon produced from EFB has good properties with high surface area (720.0 m²/g) and well developed pores.