Key Engineering Materials Vol. 908

Abstract: In this work, the effect of different annealing treatments on the phase transition, structural behaviour and thermal analysis of MnCoGe alloys has been analysed. The changes in the transition temperatures have been studied by Simultaneous Thermal Analysis (STA). The results show that the structural transition temperature (T_str) depends on the annealing treatment of the samples preparation. However, under the same heat treatment no significant change is observed on the curie temperature (T_c). The thermal analysis reveals endothermic peak which corresponds to the structural phase transition of the compounds. The microstructural evolution has been monitored using in-situ X-ray diffraction which made known this compound produce three type of structures which are hexagonal, orthorhombic and mix structure (hexagonal and orthorhombic).

Abstract: This paper study the effect of structural behaviour and electrical properties in cubic NaZn13-type La (FeSi)₁₃ compounds annealed at different high temperatures from 1000oC to 1200oC. The Raman spectroscopy measurement revealed a different level of coexistence of La (FeSi)₁₃-type phase and α-Fe in 1000oC, 1100oC and 1200oC annealed samples. The different level coexistence of the phases suggested that the samples show a significant phase change with different annealing temperature methods. This finding has also supported by impedance analyzer measurement, where the pattern shows that the 1000oC and 1100oC samples have similar behaviour waveform pattern compared to the 1200oC, which has different behaviour. Besides, the impedance pattern clearly shows that the propagation of the signal for the 1000oC and 1100oC before it arrives in the conductor state (R=0.00) has high resistive values compared to 1200oC annealed samples. Further investigation on the electrical properties was done with the conductivity and tan delta measurements. The results show that 1200oC annealed sample have a high value of conductivity (S=18μ S/m) compares with 1100oC (S= 0.1μ S/m) and 1000oC (S=4.89n S/m). The tan delta measurements found that samples annealed at 1200oC temperature has low value of resistivity (tan ɗ = 0.117) compares with 1100oC (tan ɗ = 0.335) and 1000oC (tan ɗ = 0.482) respectively.

Abstract: This paper studies the electrical efficiency of carbon nanotubes (CNT) with nanosized diameter inserted into palm-based oil at various concentrations (0, 0.0125, 0.025, 0.0375, 0.05, 0.125, 0.25 and 0.5 g/L). Dispersion methods, including sonication and drying process were systematically applied for producing stable CNT nanofluids. Several parameters such as electrical properties (AC breakdown voltage) and dielectric properties (dissipation factor, relative permittivity and resistivity) were measured accordingly based on IEC 60156 and IEC 60247 international standards. The test results reveal that the higher concentration of CNTs dispersed in palm oil, the lower AC breakdown voltages produced. At 0.5 g/L concentration, the average of 50 breakdown was 22.30 kV, which is 72.33% decrement compared to palm oil without any nanofiller. Besides, the permittivity and resistivity of CNT nanofluids decrease as concentrations increased, while dissipation factor increases along with CNT concentrations. In order to further support this indication, Raman analysis is measured to relate the behavior of AC breakdown voltages and chemical structure of CNT nanofluids. Based on the Raman spectra at 2800-3200 cm^-1 region, it is shown that the value of total unsaturated fatty acid and total fatty acid decreased as concentrations of CNT increased. This occurrence directly influences the degradation performance of AC breakdown voltages.

Abstract: Nickel Oxide nanofibers were successfully prepared by electrospinning with a precursor mixture of Ni acetate/polyvinylpyrrolidone (PVP), followed by calcination treatment of the electrospun composite nanofibers. The parameter of solution and effect of applied voltage to the morphology of nanofibers were studied. Both Ni acetate/PVP and NiO NFs, nanofibers were characterized by FESEM and XRD. The results found that the nanofibers form with smooth surface without beads and the calcination temperature was at 500°C to produce NiO nanofibers.

Abstract: Hydrodesulfurization (HDS) technique is no longer applicable in achieving ultra-low sulfur diesel because of high operational cost, high operating temperature and low efficiency. Due to these disadvantage, catalytic oxidative desulfurization (Cat-ODS) has been introduced as a new technique in achieving ultra-low sulfur diesel. The performance of the Fe catalyst was investigated in Cat-ODS of model diesel using terbutyl hydroperoxide (TBHP) as oxidant and dimethylformamide (DMF) as an extracting solvent. The physicochemical analysis of this catalyst was accomplished using several characterization techniques such as BET, EDX and HRTEM. It posseses high surface area of 226 m²g^-1 with small particle sizes in the range of 6-7 nm and less metal leaching. Under optimize condition, about 90% of sulfur was removed from model diesel. In the absence of catalyst, only about less than 80% of organosulfur compounds were removed. The Cat-ODS system showed the promising technology to be compliment with hydrodesulfurization (HDS) to produce low sulfur diesel.

Abstract: This study was conducted to investigate the potential of water snowflake, Nymphoides indica and water hyacinth, Eichhornia crassipes to remediate batik wastewater. The endurance studies of both plant species showed that water hyacinth had a higher endurance limit toward batik wastewater than water snowflakes. Therefore, the phytoremediation study of batik wastewater was further conducted with water hyacinth as the agent. The results from phytoremediation had shown that water hyacinth was capable of reducing the concentration of sodium (Na), copper (Cu), lead (Pb), and chromium (Cr) by 30.8 mg/L, 0.014 mg/L, 0.089 mg/L, and 0.007 mg/L, respectively. In addition, Na was found to be highly accumulated in the stems of water hyacinth, while Cu, Pb, and Cr were all found to be highly accumulated in the roots of water hyacinth.

Abstract: Batch adsorption studies for the removal of Malachite green (MG) dye using eggshell was performed. Response Surface Methodology (RSM) was applied to investigate the effect of significant operating parameters on the uptake of the dye molecule. The aim of this study is to determine the potential of eggshell as adsorbent for MG removal and determine the optimum conditions for the adsorption process by using RSM with Central Composite Design (CCD). A 2³ full factorial CCD was generated using Design Expert. The effects and interactions of different parameters were evaluated which are contact time (20-60 min), pH (4-8) and adsorbent dosage (0.5-2.0 g). A quadratic model was developed correlating the adsorption variables to the response (percentage of MG removal). Analysis of variance (ANOVA) was used to determine the significant factors on experimental design response. The predicted results obtained were found to be in good agreement (R² = 0.9388) with the experimental results. The optimum percentage of MG removal was found to be 90.66% with the operating conditions of 40 minutes contact time, pH 6 and 1.25 g of adsorbent dosage. It was suggested that eggshell could be a potential adsorbent in removing MG from aqueous solution.

Abstract: This paper aims to synthesize high purity nano-sized silica from rice husk ash (RHA) by chemical method and investigate its physical and chemical properties. Through a controlled burning of rice husk, the white-colored RHA is obtained. Next, the RHA is subjected to the pre-treatment of acid leaching and thermal treatment. The synthesizing process has been done through the precipitation method. The EDX and FTIR analysis confirmed that the prepared powder consists of high purity silica particles through the detection of characteristic peaks of O and Si elements and the presence of primary bonds in silica, which are silanol groups and siloxane bonds. Meanwhile, the FESEM micrograph shows that silica particles in nano-scale had been obtained with an average diameter of 74.0 nm – 84.0 nm. The XRF and XRD analysis confirmed that the prepared powder yields 99.68% nano-silica in an amorphous structure.

Abstract: The barium oxide impregnated iron(III) oxide (BaO/Fe₂O₃) adsorbent was synthesized by an ultrasonic-assisted method. The adsorbent was calcined at 200-500 °C and its adsorption capacity was measured. The ultrasonic-assisted synthesis generated well-dispersed of BaO on Fe₂O₃ by giving none of the BaO peaks were observed through the XRD pattern. The most efficient adsorbent of BaO/Fe2O₃200 was calcined at 200 °C with adsorption capacity for physisorption and chemisorption of 5.01 and 88.81 mg/g respectively. Besides other carbonate species, it was believed the presence of the hydroxyl group could enhance the sorption by forming bicarbonate upon CO₂ chemisorption. It is also possessed a lower desorption range compared to BaO and Fe₂O₃ alone. The experimental CO₂ adsorption isotherm at 25 °C fit better with the Freundlich isotherm model. It implies a favorable adsorption process with multilayer adsorption occurs onto the heterogeneous surface.

Abstract: High Chemical Oxygen Demand (COD) levels in water indicate a vast amount of oxidizable matter that consumes a lot of dissolved oxygen in water. This results in adverse impacts on both aquatic ecosystems and human health. Wastewater from the fish cracker industry typically has high organic content and high COD value. In this study, rice husk was chosen as the raw material because of its abundance and economy. The optimum adsorption parameters such as flow rate, contact time, and initial COD concentration that affect adsorption by rice husk activated carbon were studied using Response Surface Methodology. The treatment was done in a continuous fixed-bed column. From the Box-Behnken design, it was determined that 68.09% removal percentage resulted from the best combination of 4.5 hours of contact time, 1 mL/min of flowrate, and 5% initial COD concentration. The SEM micrograph shows the adsorbent consists of a large number of pores before adsorption. Based on the study, rice husk activated carbon can be an alternative treatment for COD removal in wastewater. The use of activated carbon derived from agricultural waste materials can help reduce the waste produced, which will otherwise end up in the landfill.