Abstract: In this research, optoelectronic devices consisted of an infrared light emitting diode and a phototransistor with no special handling or third party-packaging were irradiated to ionizing radiation utilizing x-rays. It was found that the devices under test (DUTs) undergo performance degradation in their functional parameters during exposure to x-rays. These damaging effects are depending on their current drives and also the Total Ionizing Dose (TID) absorbed. The TID effects by x-rays are cumulative and gradually take place throughout the lifecycle of the devices exposed to radiation.
Abstract: The purpose of this paper is to investigate the mineralogical components of palm oil fuel ash (POFA) with or without unburned carbon by using semi-quantitative X-ray diffraction (XRD). Original POFA taken from palm oil mill was ground in ball mill, producing ground POFA (GPOFA). Unburned carbon was removed by heating the GPOFA at 500 °C for 1 h, producing treated POFA (TPOFA). Neither glassy phase crystallization nor agglomeration of GPOFA particles occurred during the heat treatment. The content of crystalline phase and glassy phase in GPOFA or TPOFA was determined using semi-quantitative XRD analysis internal standard method. The results showed that GPOFA and TPOFA contained 67.22% and 73.89% of glassy phase, respectively, which could be used as pozzolanic materials. The presence of P2O5, K2O and Na2O in POFA was the reason of reducing the melting point of POFA in boiler.
Abstract: Polycrystalline perovskite manganites of Pr0.67Ba0.33MnO3 bulk ceramic samples were prepared via conventional solid-state reaction. The influence of structure and microstructure towards sintering temperature of the samples were studied. At lower sintering temperature (900°C, 1100°C and 1100°C) other phases such as PrO2 and BaMnO3 were detected using XRD and further confirmed with EDX analysis. Furthermore, phase purification and crystal structure transformation was observed in sample sintered at 1200°C and 1300°C respectively. SEM analysis indicated that higher sintering temperature promotes grain growth and densification. Overall, in this paper, phase purification and crystal structure transformation had been observed. Orthorhombic structure is more favorable to form at higher sintering temperature for Pr0.67Ba0.33MnO3.
Abstract: The investigation of ceramic filler on the properties of denture base materials made from PMMA filled with Al2O3/ZrO2 was carried out. The amount of Al2O3/ZrO2 filler was fixed at 5 wt%. However, the ratios of Al2O3 to ZrO2 added were varied from 0 to 100. Samples were prepared for fracture toughness and flexural test. The findings were analyzed using scanning electron microscopy (SEM). The findings were recorded that the Al2O3/ZrO2 ratios show higher fracture toughness and flexural properties than PMMA matrix. SEM micrographs indicate that distribution of Al2O3 and ZrO2 in the PMMA matrix is fairly homogeneous. The mixing method was good between reinforcement particles and PMMA matrix. Therefore, addition of six ratios of Al2O3/ZrO2 with PMMA and this mixture is able to improve the mechanical properties of this denture base material.
Abstract: Black aluminium dross produced from a local aluminium smelting plant was used in this study. Solvothermal method was used to produce nanostructured alumina from this waste. Initial product obtained is of low quality with 86.9% Al2O3 content and mixed crystalline phases of 71% α-alumina and 29% calcium dodeca aluminate (CaO(Al2O3)6). The introduction of the fractional precipitation stage into the process helps in improving the purity of the alumina product to 96.5% and also produces 100% α-alumina crystalline phase. The study also shows that the crystallite size of the α-alumina products produced from this process is less than 100nm.
Abstract: Vickers hardness of zirconia toughened alumina added MgO with different composition and particle size has been studied. Five different size of magnesium oxide particle at different composition (0.5 wt % to 0.9 wt %) were used in this experiment. Each batch of composition was mixed, uniaxially pressed into 13 mm pellets and sintered at 1600oC for 4 hours in pressureless conditions. Analysis of Vickers hardness, microstructural observation and EDX analysis has been carried out. Microstructural observation showed that the addition of magnesium oxide greatly affected zirconia toughened alumina microstructure. Smaller Al2O3 grain size is observed with the presence of MgO thus improving its mechanical properties such as hardness and density. Results of Vickers hardness increased linearly with addition of more MgO until a certain composition. Each particle size of MgO addition show different composition is needed to reach the optimum Vickers hardness, depending on the particle size. The increase of hardness of the cutting insert is mainly contributed by small sized Al2O3 grains due to the microstructure pinning effect introduced by MgO. Maximum Vickers hardness achieved in this experiment is 1710 Hv, obtained at 0.7 wt% MgO with 0.15 µm particle size.
Abstract: the paper relates a study in developing a quantitative elemental analysis for clay minerals by the EDXRF technique. Elements of interest are Al, Si, K, Ca, Ti and Fe. The regression method involved development of calibration graphs of each of these elements using six different clay minerals reference standards. straight lines were obtained from these calibration graphs with r2 values ranging from 0.923 to 0.997. The accuracy of this regression method was then tested by comparing the quantitative analysis result obtained from fundamental parameter method using argillaceous limestone reference standard as the sample. Fundamental parameter method gives a more accurate result than that of the regression method.
Abstract: Epitaxial growth of GaN has become an interest topic in term of light emitting device fabrication. Most of the commercial GaN based device is normally grown on sapphire substrate. For power device application, SiC has been found to be a desirable candidate for GaN epilayer due to their high thermal conductivity, small lattice mismatch, and hexagonal lattice mismatch with cleaved facet for the laser cavity. In this paper, X-ray diffraction (XRD) technique is employed to study the structural properties of GaN thin film grown on 6H-SiC substrate. For conventional XRD -2 scan, only diffraction peaks from GaN (002) and its multiple diffractions were observed, along with diffractions from SiC (006) peak. These results suggested that the GaN film is in wurtzite phase. For XRD rocking curve of omega scan of (002) diffraction plane of the GaN, a full width at half maximum of about 259 arcsec is obtained.