Advanced Materials Research Vol. 620

Abstract: The purpose of this work is to understand the phases formation and lattice parameter changes with addition 0.6 to 2.7 wt.% in Al-Si-Mg-Ce cast alloy. Al-Si-Mg-Ce eutectic and hypoeutectic cast alloy were prepared by conventional casting technique. The alloys were investigated by using optical microscope, Scanning electron microscope (SEM) and X-Ray diffractometry (XRD). The addition of Ce resulted in precipitation of Al₄Ce in eutectic cast alloy and CeMg₂Si₂ in hypoeutectic cast alloy. The lattice parameter of Al increases with increase in Ce content wheareas lattice parameter of Si phase decreases as the Ce content increases.

Abstract: Novel hexagonal rods of Bi_0.4Sb_1.6Se_3xTe_3(1-x) (0.0x1.0) were synthesized successfully through solid-state microwave synthesis. These hexagonal rods were explored using field emission scanning electron microscopy images. The X-ray diffraction results indicate that the powders (0.0x0.8) can be indexed as the rhombohedral phase, whereas the sample with x=1.0 has an orthorhombic phase structure. The electrical conductivity gradually decreases as Se increased, resulting in an increase in the Seebeck coefficient. Ascribing to the increased Seebeck coefficient for the sample with x=0.8, the maximum power factor is 7.47 mW/mK² at 373 K.

Abstract: Zinc oxide (ZnO) nanostructures were successfully grown on gold-seeded Si substrate prepared by a solution-immersion method using a novel mixture of an aqueous solution of Zinc nitrate hexahydrate (Zn (NO₃)₂.6H₂O) with a non-toxic, odourless urea (CH₄N₂O) as a stabilizer. Structural and optical properties of resultant ZnO thin films were investigated by X-Ray Diffraction, FESEM and Photoluminescence Spectroscopy (PL). Clusters of ZnO micro-flower with serrated broad petals with the thickness of petals approximately 60 nm were interestingly formed on the film with horizontal manner of alignment during immersion process. The smallest grain size (29 nm) along (100) orientation was achieve with the alignment of substrate tilt towards 60°. The petals structure has high surface area, is a potential metal oxide nanostructures to be develop for optoelectronic devices and chemical sensors.

Abstract: Potassium Calcium Silicate (K₂CaSiO₄) is a mineral that has been of high interest in the field of applied mineralogy. Crystallization of K₂CaSiO₄ from high chromium EAF slag was studied and the slag samples were characterized using XRF, XRD, SEM/EDX, FTIR and TG/DTA. The distinct mineral phases in the EAF slag were neutralized and formed with a grain boundary by air cooling and dispersed phases by water cooling. The EDX revealed that both the grain boundary and matrix phases are composed of potassium, calcium and silicon. The addition of K₂CO₃ to EAF slag not only imparts the needed potassium but also reduced the heavy metal present in the slag as revealed by the XRF analysis. Using thermodynamic modeling, it is deduced that the percentage of potassium silicate formed during simulation process (when) increases as the basicity of EAF slag decrease.

Abstract: Representative of clay deposits from central Cambodia were analyzed in terms of their mineral phases, mineralogical composition and phase changes after firing by qualitative and quantitative XRD analysis. To examine the phase changes, the samples were prepared and fired from 950 to 1200 °C. Results show that Cambodian clays contained quartz, illite, kaolinite, and chlorite-vermiculite mixed-layer as dominant mineral phases and the minor phases of albite and calcite also appeared in the samples. The rational analysis shows that chlorite-vermiculite was the main mineral in all Cambodian clays. After the samples were preceded upon firing, new phases of mullite, hematite and crystobalite were appeared above 1050 °C.

Abstract: In the current investigation, friction stir processing (FSP) of aluminium alloy 6061 alloy was carried out under different cooling conditions to determine its influence on the microstructure evolution and properties of the investigated alloy. It was found that the type and distribution of the strengthening precipitates in the friction stir processed Al 6061 alloy significantly depend on the FSP parameters and working temperatures during FSP. The properties of friction stir processed alloy were evaluated using micro-hardness and bulk hardness tests. It was observed that 6061 alloy friction stir processed under rapid cooling conditions exhibited enhanced hardness which was found to vary between nearly 12 to 33 % as compared to the alloy processed under ambient cooling conditions.

Abstract: The crystal structure of N-(3,4-Dichlorophenyl)-3-oxobutanamide (I) is optimized by semi-empirical methods using MOPAC2009 program. The optimized geometries from both Austin Model 1 (AM1) and Parametrization Model 6 (PM6) describe the conformational discrepancy and crystal packing. The energy minimized structures from both the models are in good agreement with X-ray crystal data. The intramolecular charge transfer interactions are studied from the molecular orbital calculations. The parametric molecular electrostatic potential (PMEP) calculated by AM1 semi-empirical method shows the involvement of oxygen and chlorine atoms in the crystal packing interactions. The aromaticity of phenyl ring in the structure is determined using HOMED calculations.

Abstract: The properties of mortar containing rice husk ash at varying temperatures were studied. Three rice husk ash samples were prepared at different temperatures and with various colors, i.e., 600°C (pink), 800°C (grey), and 1000°C (white), all were used for this study. Ordinary Portland cement (OPC), a well known universal binder, was partially replaced with rice husk ash at 10, 15, 20, and 30% by weight of binder. The water to binder ratio (W/B) of the mortar was kept constant at 0.45. The mortars were subjected to seawater or saturated Ca (OH)₂ solution. The controlled and exposed mortars were characterized using X-ray diffraction, FTIR spectroscopy and compressive strength test. The results show that the amount of silica present in RHA are varied with burning temperature and colors, approximately in the range of 95 to 97%. White RHA produced higher compressive strength both in seawater and Ca (OH)₂ solution. Finally, white RHA with 15% replacement was most suitable to be used as additive in OPC, and showed good potential for use in seawater applications and alkaline environment.

Abstract: Milling process through mechanical alloying method was performed on a powder mixture of Fe-80.11 wt%, Nb-17.62 wt% and C-2.26 wt% to produce Fe-NbC composite by in situ reaction. Ball to powder weight ratio parameter was selected since formation of phase and microstructure characteristics of this composite were expected to depend on ball collision event during milling. The as-milled and sintered Fe-NbC was characterized by X-ray diffraction (XRD) and Scanning Electron Microscopic (SEM). We found that formation of Fe-NbC by in situ required mechanical alloying of the mixture using 10:1 of ball to powder weight ratio to achieve small crystallite size and more homogeneous of NbC phase.

Abstract: Polyvinyl alcohol (PVOH) and corn starch (CS) blends were prepared with various amounts of attapulgite (AT) clay to form a series of PVOH/CS/AT blend films by using a solution casting method. The effect of AT on the XRD pattern and tensile properties of the composites were investigated. It was found that addition of AT in PVOH/CS blend has changed the crystallinity index of the blend films and thus influenced the tensile properties. PVOH/CS/AT1 blend films showed the highest crystallinity index and proved by the value of tensile strength and tensile modulus. The lowest crystallinity index is shown by the PVOH/CS/AT5 blend films.