Materials Science Forum Vol. 889

Abstract: Pure and F doped TiO₂ nanotubes was synthesized using simple hydrothermal method. The hydrothermal was conducted using teflon-liner autoclave and maintained at 150oC for 24 hours. The characterization of synthesised product was carried out using x-ray diffraction (XRD), transmission electron microscope (TEM), energy dispersive of x-ray spectroscopy (EDX) and ultra violet – visible light diffuse reflectance spectroscopy (UV-Vis DRS) for band gap measurements. XRD patterns indicated that anatase TiO₂ phase was remained after F doping suggested that fluorine was highly dispersed into TiO₂ by substituted with O in the TiO₂ lattice to formed TiO_2-xF_x solid solution. Morphology investigation using TEM found out small diameter of nanotubes structure within 8 – 10 nm of pure and F doped TiO₂ nanotubes. The band gap energy (E_g) of both nanotubes samples were almost similar proposing that F doping does not modify the band gap energy.

Abstract: This paper reports the outcome of the laboratory investigation conducted on new clay liners modified with kaolinite combined with various content of lime-treated, various content of bentonite and admixture of kaolinite adding with 3% nano-kaolinite for composition. The 3% nano-kaolinite was chosen based on earlier finding by S.V.Netethu (2013). The various content of lime-treated and bentonite adopted are 2.0%, 5.0%, 7.5% and 10.0% by total weight of the kaolinite. Compaction tests was performed on the resulted modified clay liner samples to evaluate the best percentage that gives optimum moisture content (OMC) and maximum dry density (MDD) . The best percentage of each bentonite and lime-treated are chosen and be added into kaolinite and the physical properties of samples are tested and compared to the other two samples which are kaolinite only and kaolinite added with 3 % of nano-kaolinite. Nano-kaolinite was produced using a mill machine and the sized of nano-kaolinite (1nm-100nm) were examined under Scanning Electron Microscope (SEM) machine.The addition of 3% nano-kaolinite to the kaolinite gives the best compaction result compared to bentonite or lime-treated. The value of dry density is increased to give the reduction of air voids, thereby reducing the hydraulic conductivity by concept. Based on the compaction test value, it clearly observed that admixture of kaolinite adding with 3% nano-kaolinite gives the best results from the other samples due to required less water to achieve maximum dry density of 1.39 Mg/m³ and 27.34% of optimum moisture content resulted positive effect in soil properties.

Abstract: This research focuses on the diaphragm design of the graphene MEMS capacitive microphone. Simulation part will be first involved in order to get the optimum dimensions of each elements by COMSOL multiphysics simulation software. This study will discussed on mechanical behavior of graphene diaphragm for MEMS capacitive microphone. First stage will implicated a theoretical model of diaphragm MEMS capacitive microphone. Then, boundary element based simulation with some mathematical formula will be used to design and evaluate the model. The output value of selective parameters such as the thickness and diameter of diaphragm, air gap and others are crucial in order to further fabricate the MEMS capacitive microphone. The proposed design of graphene diaphragm are in circular shape and square shape. The mechanical sensitivity of diaphragm with the pressure changes will be the crucial parameters in early stage. The results revealed that the circular shape diaphragm shows the better deflection with the thicker diaphragm gives the lower deflection. Von mises stress for both diaphragm shape also recorded in order to avoid the failure of the proposed design.

Abstract: In this work, effect of chirality on gas adsorption property of semiconducting single-wall carbon nanotubes (SWCNTs) is reported for the first time. First principles simulation of the interaction of three different chirality SWCNTs with different gas molecules is performed maintaining equilibrium tube–molecule distance. Results are obtained employing density functional theory, using the Atomistic toolkit simulation package (ATK-DFT). Nanotube density of states is observed to vary significantly due to interaction with different types of gases as well as for same gas if chirality of SWCNTs varies. The most significant finding is, the change in DOS near Fermi level is highest in mod 2 type semiconducting SWCNT for different gas molecules irrespective of donor or acceptor. Thus, proper selection of chirality of SWCNT is important to make nanotube based gas sensor and mod 2 types semiconducting SWCNTs should get preference over mod 1 type as a sensing element so as to get better sensitivity.

Abstract: In this work, an improved technique for chirality assignment of single wall carbon nanotubes (SWCNT) is proposed which work for both isolated and bundles SWCNTs. The technique exploits the (2n+m) family pattern both in optical transitions vs diameter plot and Raman G-mode frequency vs diameter plot of SWCNTs. Using two different plots can give accurate value of the family of unknown SWCNTs that can be used to find chiral index (n, m) of unknown SWCNT unambiguously in most of the cases. Unlike existing methods, graphical comparison or pattern recognition with an existing Kataura plot is not required here. Chirality of 13 SWCNTs are assigned here using this technique. Validity of assigned chirality is cross checked from previous experimental reports. The technique is especially useful for determining chirality of isolated SWCNT.

Abstract: Concrete is one of the most important materials for construction industry. The material in the mixture of concrete includes cement, sand and coarse aggregate. Production of cement causes the air pollution from the emission of carbon dioxide to the air. This research studies the replacement of cement with palm oil fuel ash (POFA) in the concrete mixture. The objective of this research is to investigate the compressive strength of concrete and water absorption rate of concrete made from POFA and to compare the strength and absorption rate between conventional concrete and concrete made from POFA. This is to indicate whether the compressive strength and absorption rate are equivalent to the strength of conventional concrete. The methodology used in this research is experimental method and the palm oil fuel ash was taken from palm oil mill in Cha’ah, Johor, Malaysia. The results of this research are the specimens which contain 20% POFA has a compressive strength and water absorption rate comparable to conventional concrete.

Abstract: This study investigated the effects of multiple blended binders on the properties and performance of concrete pavement. Mineral admixtures, namely, silica fume, metakaolin, and rice husk ash, are used to replace ordinary Portland cement at replacement levels of 0% (control mix), 5%, 10%, and 15% by mass-to-mass basis. The performance of the multiple binders on the concrete pavement properties was evaluated based on compressive strength, strength reduction, and strength activity index. Results showed that the mineral admixtures can be satisfactorily used as cement replacement materials to increase the properties of pavement concrete. Moreover, concrete pavements with 5% and 10% replacement levels exhibited excellent performance with good strength.

Abstract: This paper presents the structural behaviour of reinforced concrete beam embedded with high density polyethylene balls (HDPE) subjected to flexural load. The HDPE balls with 180 mm diameter were embedded to create the spherical voids in the beam which lead to reduction in its self-weight. Two beam specimens with HDPE balls (RC-HDPE) and one solid beam (RC-S) with dimension 250 mm x 300 mm x 1100 mm were cast and tested until failure. The results were analysed in the context of its ultimate load, load-deflection profile, and crack pattern and failure mode. It was found that the ultimate load of RC-HDPE was reduced by 32% compared to RC-S beam while the maximum deflection at its mid span was increased by 4%. However, RC-HDPE is noticed to be more ductile compared to RC-S beam. Both types of beams experienced flexure cracks and diagonal tension cracks before failure.

Abstract: Flow insulator is the material which having fluid flow through itself resulting to the fluid temperature difference between the upstream and downstream regions. The flow insulation characteristics of combined two cordierite alumina (Cr-Al) porous plates with 2 mm free space was investigated experimentally. The results indicated the air temperature drop across the flow insulator and the thermal efficiency increase with the inlet air temperature and decrease with increasing air flow rate. The higher PPI porous plate placing upstream layer resulted in increasing the thermal efficiency of the flow insulator significantly.