Materials Science Forum Vol. 756

Abstract: Layered double hydroxide (LDH) hybrid materials of Zn-Al-layered double hydroxide-3,4-dichlorophenoxy acetate acidnanocomposites (ZADs) were prepared by direct self-assembly method. The pH of the solution was adjusted to 7.5 using 2M NaOH. Various Zn2+ to Al3+ molar ratios, R ranging from 1 to 6 were used with a fixed concentration of 3,4-D at 0.3 M. The Powder X-ray diffraction (PXRD) patterns showed the formation of well-ordered nanocomposite with the expansion of basal spacing from 8.9 Å in the Zinc-Aluminium-Layered Double Hydroxide (ZAL) to 18.7 - 22.1 Å in the resulting nanocomposites. The Fourier transform infrared (FTIR)spectra for the nanocomposites showed features for both ZAL and ZAD, showing the successful intercalation of the organic moiety into the LDH interlayer. The percentage loading of 3,4-dichlorophenoxy acetati acid(3,4-D) in LDH was found to be increased from 34.7-48.1 % (w/w), as the mole fraction of Al decreased from 0.44-0.15. This study shows that the mole fraction of zinc ion was replaced by aluminium ion in the LDH plays an important role in controlling the physic-chemical properties of the resulting material.

Abstract: The performance of an adiabatic extrusion in minimizing the risk of thermal degradation for PA6/C20A nanocomposites was investigated in this paper. The screw speed of twin-screw extruder was maintained at constant value of 100 RPM while the clay loadings C20A were varied between 1 wt %, 3wt % and 5 wt % respectively.Thermal gravimetric analysis was used to characterize the thermal property of polyamide6/C20A-nanocomposites and the crystallization pattern was thoroughly examined via the application of differential scanning calorimetry. The time taken for 10 wt.% mass losses of majority adiabatic extruded samples was observed to be longer as compared to the conventional extruded PA6/C20A samples. The combination effect of adiabatic extrusion and nanoclay presence in the PA6-matrix has managed to increase thermal resistant of PA6. The crystallinity grade for each of the samples with different loading of C20A. however has not diversed in value since the index of crystallinity (Xc) remains independent of C20-volume althoughconventional/adiabatic setting of extruder could possibly have greater effect on the crystalline feature of PA6/C20A nanocomposites.

Abstract: The etching processes of Si [1 0 0] wafer have been studied using two different methods; namely the wet chemical etching method, using HNO3-HF-CH3COOH solution, and the Ultra Low Frequency Plasma (ULFP) method at (1KHz). Ion etching using inert gas only (e.g., argon gas), and ion chemical etching using an active gas (beside the inert gas) such as oxygen techniques were used. Calculations of the different parameters produced by chemical etching and plasma etching for silicon wafer (sample) such as ( hole depth, hole width and etching rate) were investigated using the images of Optical Scanning microscope (OSM) and Joel Scanning microscope (JSM). The formed hole width (ω) increases by increasing the exposure time of the sample in the different types of etching. Values of the hole width were in the range of 2- 7 µm during exposure times of (30 to 100 min). The sample growth exponent constant was about ( 0.0707 and 0.0537 µm/min ) .Hole has depths in the range of( 0.5 to 3 µm) in time of (30 to 100 min).The average distances between the holes were decreased by increasing the exposure time from (14 to 4 µm) in the time range of (30 – 100 min). The rates of etching were ranged from (0.0226 to 0.0448 µm/ min) either for dry or wet etching. Normal 0 21 false false false MS X-NONE X-NONE The etching processes of Si [1 0 0] wafer have been studied using two different methods; namely wet chemical etching method, using HNO₃-HF-CH₃COOH solution, and Ultra Low Frequency Plasma (ULFP) method at (1KHz). Ion etching used inert gas only (e.g., argon gas) while ion chemical etching used an active gas (beside the inert gas) such as oxygen techniques were used. Calculations of the different parameters produced by chemical etching and plasma etching for silicon wafer (sample) such as ( hole depth, hole width and etching rate) were investigated using the images of Optical Scanning Microscope (OSM) and Joel Scanning Microscope (JSM). The formed hole width (ω) increased by increasing the exposure time of the sample in the different types of etching. Values of the hole width were in the range of 2- 7 µm during exposure times of (30 to 100 min). The sample growth exponent constant was about (0.0707 and 0.0537 µm/ min). Hole has depths in the range of( 0.5 to 3 µm) in time of (30 to 100 min).The average distances between the holes were decreased by increasing the exposure time from (14 to 4 µm) in the time range of (30 – 100 min). The rates of etching were ranged from (0.0226 to 0.0448 µm/ min) either for dry or wet etching. /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

Abstract: Nanoindentation tests with loading rates of 0.05 mN/s, 0.1 mN/s, 0.5 mN/s, and 1.0 mN/s were conducted on the Au ball bond. The effect of different loading on the Au ball bond were analysed based on qualitative and quantitative results. The displacement burst was more pronounced with the increment of loading rates. The increase of hardness value and the decrease of the reduced modulus value when the loading rate was increased are due to the effect of creep. It was found that the loading rate of 0.5 mN/s is the appropriate and stable value for the nanoindentation test on the Au ball bond.

Abstract: The synthesis of aligned multi-walled carbon nanotubes (MWCNTs) using thermal and floating catalytic chemical vapor deposition (CVD) method has been optimized in order to obtain MWCNTs with specific characteristics namely diameter and thickness of nanotubes array. Process parameters such as substrate preparation which involved buffer layer deposition, temperature and reaction duration were studied. Samples produced were analyzed using FESEM, HRTEM and Raman spectroscopy. Typical thickness of CNTs array obtained using thermal CVDis 38 µm whilst the ones from the floating technique have a wide range of thickness with the thickest being about 639 µm for the duration of 1 hour. Floating CVD method has the capability to produce good quality, aligned CNTs array with various thicknesses required to vary the electrode gap of the ionization-based gas sensor for the reduction of the breakdown voltage, leading to low power consumption and safe operation of the sensor.

Abstract: The oxide semiconductor with different band gap energy i.e. manganese dioxide (MnO₂) (E_g: 1.30eV) and zinc oxide (ZnO) (E_g: 3.37 eV) nanoparticles were used to degrade RhodamineB (RhB) under irradiation of UV light (254 nm).The MnO₂ nanoparticles were synthesized by hydrothermal method (160 °C, 4 h) using analytical grade manganese sulfate hydrate and potassium permanganate (VII) as precursors. The XRD analysis reveals that the nanoparticles were d-MnO₂.The photocatalytic study shows that degradation of RhB solution by ZnO nanoparticles (rate constant: 0.02749 min^-1) was approximately four times faster than the d-MnO₂ nanoparticles (rate constant:0.0067 min^-1). This observation could be attributed to the higher reducing and oxidizing power of ZnO in producing free radicals for photodegradation of RhB solution.

Abstract: Calcium hydroxides (Ca(OH)₂) nanostructures have been fabricated through simple facile solution based synthesis at different temperatures 35,45 and 55°C repectively.Ethanol was utilized as a medium for reaction. The synthesized powder was characterized by Field Emission Scanning Electron Microscope (FESEM SUPRA 35VP ZEISS), Fourier transform infrared (FTIR Perkin Elmer Spectrum One Spectrophotometer) and X-raydiffraction (XRD). Based on XRD analysis, the synthesis samples exhibited crystal hexagonal phase of Ca(OH)₂.The crystallite size for powders prepared was between 17 nm to 31 nm. Short nanorod like structures was successfully obtained in 80 ml ethanol solution for entire temperatures. However, the length and diameter decreased with increased the reaction temperatures. Short nanorod synthesized at 55°C has small diameters and length compared at 35°C. Carbon dioxide (CO₂) adsorption for synthesized powders was studied by simultaneous thermal analyzer (STA). Ca(OH₎₂ prepared at 35°C and45°C in 80 ml ethanol showed CO₂ adsorption capacity about 9.3 mmol/g and 9.7 mmol/g respectively.

Abstract: The utilization of greenhousegases, such as carbon dioxide (CO₂) and methane (CH₄), is among the most important challenges in the energy research field. The catalytic activity behavior of CO₂ reforming of CH₄ (CRM) over synthesized multi-walled carbon nanotubes (MWCNTs) with Co-Mo and MgO nanoparticles was investigated. Based on conversion of reactants and production of syngas, the synthesized Co-Mo-MgO/MWCNTs were found to be a suitable catalyst for the CRM reaction. The CH₄ and CO₂ conversions were greatly influenced by the reaction temperature in the range of 750-1000 °C. The catalyst exhibited high activity and stability during 10 h reaction time with 82.68% conversion of CH₄ at 950 °C respectively,without significant deactivation. The reaction rate of CH₄ and CO₂ over carbon nanotubes was affected significantly by the reaction temperature.The syngas ratio was close to unity and no carbon deposition over the catalyst was observed after the termination of the reaction.

Abstract: Numerous research have been conducted to improve the efficiency of dye solar cell (DSC) through the study on its components namely the dye, electrolyte, counter electrode and the photoelectrode material. This paper presents the study on the usage of a multilayered structure with different composition of TiO₂ nanoparticles/aggregates composites starting with the top layer consisting of purely aggregates and ending with the bottom layer consisting of wholly nanoparticles as the photoelectrode material. The graded composition profile of increasing amount of aggregates at the top of the photoelectrode and increasing amount of nanoparticles at the bottom of the photoelectrode will allow for the enhancement in the optical properties and kinetics of DSC. The layers were screen-printed onto FTO coated glass substrate to form the photoelectrodewith an active area of 1 cm2 and thickness of 12 µm. The N719 dye-coated TiO2 electrode was then assembled into sandwich configuration with platinized conducting glass electrode and injected with iodide/tri-iodide redox couples electrolyte.Kinetics and the underlying transport properties of the assembled DSCs were measured by Electrochemical Impedance Spectroscopy (EIS). The response of the cells towards a spectrum of light frequencies was measured using Incident Photon to Electron Conversion Efficiency (IPCE). Conversion efficiency was measured using a 100 mW/cm2 solar simulator. Highest efficiency was found for the multilayered photoelectrode configuration at 4.58% with 14% improvement over the DSC with pure aggregate.DSCs with the multilayered composite configuration have higher current density, Jscwith an increase of 2.249 mA cm-1 compared to the one with only nanoparticles and only aggregates layer. Multilayer configuration has shown significant improvement in the quantum efficiency by exhibiting higher light absorption especially in the range of 500-550 nm light wavelength by about 12.9%.The increase in the conversion efficiency of DSCs with multilayer configuration is also attributed to the improvement in the electron diffusion as evident by the EIS measurement.

Abstract: Solvent controlled synthesis of tin oxide nanocatalysts were prepared via the hydrothermal method. To study the effect of solvent on the particle size of tin oxide and their catalytic efficiency on photodegradation of environmental hazardous materials, the synthesis was carried out at different concentrations of solvent (isoamyl alcohol) keeping all other reaction conditions constant. The nanoparticles were characterized by FourierTransmission Infrared Spectroscopy, Scanning Electron Microscopy, Transmission Electron Microscopy, X-ray Diffraction and Thermogravimetric analysis. Prepared nanoparticles were applied as nanocatalyst under UV-visible light for the photodegradation of methyl green,which is an abundant organic pollutant of industrial waste water. Photodegradation activities of the nanocatalysts were measured in three different ways, i. pseudo first order rate constant, “k”. ii. percentage degradationand iii. degradation rate. Effect of solvent was quantitatively explained in term of double sphere model of ion-ion interaction. Degradation of pollutants was also monitored by High Performance Liquid Chromatography.