Wandee Onreabroy

Temperature Effect on Chicken Egg Shell Investigated by XRD, TGA and FTIR

The main purpose of this work is to study the structure of Anadara granosa shell sample and its structural transformation upon heat treatments. The sample was ground and characterized as powder throughout this work. Structural identifications of all samples were characterized, and determined qualitatively by using X-ray diffraction, IR spectroscopy and thermogravimetry measurement (TGA). It was found that the specimen is made of aragonite, a common phase of CaCO3 mineral. The powder sample was annealed at specific temperatures over the range of 200°C - 900°C and the effects of heat treatment on the structure of Anadara granosa shell samples were studied. The results show that aragonite transforms to calcite at the temperatures between 200°C and 400°C and completely becomes calcite between 400-500°C. Then, the calcite transforms to calcium oxide at the temperatures between 500°C - 900°C. The exact structures and quantities of phase at different annealing temperatures were studied by Rietveld refinement. In our study, we also used IR spectroscopy and TGA to study the effect of water absorption of the samples on the phase transformation.

Novel Photocatalytic Ag/TiO2 Thin Film on Polyvinyl Chloride for Gaseous BTEX Treatment

This study aims to provide the photocatalytic approach for treatment of some hazard air pollutants such as benzene, toluene, ethylbenzene and xylene (BTEX) under visible light. Silver doped titanium dioxide (Ag/TiO2) thin films with various molar ratios (0.01, 0.05, 0.1 and 0.2 mol) were synthesized via sol-gel method and dipped on polyvinyl chloride (PVC) sheet before curing with UV lamp. The X-ray diffractograms showed the composite of TiO2 anatase and nanosilver. The effect of silver doping on decreasing of band gap energy of TiO2 was observed from the absorption edge shift to higher wave length, analyzed by UV-visible spectrometer. The results from hydrophilicity test indicated that hydrophilicity of TiO2 thin film was increased by doping silver. The morphology of the Ag/TiO2 thin film studied by Scanning Electron Microscope equipped with an Energy Dispersive Spectrometer revealed well dispersed nanosilver on the smooth thin film. The BTEX degradation was carried out in a batch reactor with the initial concentration of mixed BTEX gas [25 ppm]. The remaining BTEX was examined by Gas Chromatography equipped with flame ionization detector. Among Ag/TiO2 thin films, the 0.1 Ag/TiO2 thin films exhibited the best performance for gaseous BTEX degradation under visible light. The maximum degradation efficiency was belong to xylene (89%), followed by ethylbenzene (86%), toluene (83%) and benzene (79%).

XRD, Photoluminescence and Optical Absorption Investigations of Cobalt‐doped ZnO

Zn1−xCoxO (with x = 0, 0.01, 0.10 and 0.20) were synthesized by solid‐state reaction method sintered at 600° C for 12 hours. The samples were studied by X‐ray diffraction (XRD), optical absorption (UV‐Vis) and Photoluminescence (PL). Structural analysis by Rietveld method using XRD showed that the peaks of secondary phase Co3O4 with a cubic structure were visible in the high‐doped sample (x = 0.1, 0.2), besides the main peaks of wurtzite‐like structure the same as that of ZnO. Shift of the XRD peaks proved the incorporation of Co2+ into the ZnO lattice. The band gap energy decreased from 3.18 to 3.14 eV with the increasing of cobalt concentration. PL spectra at room temperature showed the blue emission with the peak around 412 nm. In addition, the intensity of the blue emission decreased upon increasing the Co concentration, which indicated their high structural, defects and optical quality in the ZnO.

Effects of dust accumulation and module cleaning on performance ratio of solar rooftop system and solar power plants

Thailand is an agricultural country, with rice, sugar, and cassava as the major export products. Production of rice, sugar cane, and cassava entails agricultural activities that give rise to significant airborne dusts. In this work, five photovoltaic (PV) units (one solar rooftop and four power plants) are selected for the study. From the study of dust accumulation on glass surface located near rice farms, it was found that opaque areas due to the deposition of dust are 11–14% after 1–2-week exposure. As a consequence, PV system performance is affected. Performance ratio was calculated to determine these effects. Overall results reveal that during the dry and hot seasons, dust deposition significantly affects the performance ratio. The performance ratio reduces by 1.6–3% for 1-month dust accumulation and reduces by 6–8% for 2-month dust accumulation. After cleaning the dust accumulated, the performance ratio greatly increases, resulting in the increase in the energy output by 10%. This increase provides economic and cost benefits of PV cleaning. The performance ratio is not significantly changed during the rainy season, which PV modules are relatively clean as the dust is washed away by rain. It was also found that most of the solar power plants in Thailand still rely on manual cleaning of PV modules with washing water followed by wiping. However, only one power plant, employs a machine for cleaning, resulting in lower cleaning costs.

Structural Evolution of Cu-In-Se Thin Films Prepared by Spin Coating Technique

A low cost and simple fabrication of Cu-In-Se polycrystalline thin film for copper indium diselenide solar cell was prepared in a two-step process. The first step, a Cu In precursor film was prepared from copper acetate monohydrate and indium acetate mixed solution. The solution was coated on molybdenum-coated soda lime glass using the spin coating technique at room temperature following annealing in air at 500°C for 20 minutes. The effect between spin parameters and film thickness of as-deposited Cu-In film were investigated. The second step, selenium was added in the precursor film by selenization process at 450°C in Se atmosphere for 30 minutes in a low vacuum tube furnace with background pressure of 10-2 mbar. The crystallographic properties of Cu-In-Se thin films were identified by X-ray diffractometer (XRD), the surface and cross-sectional morphology of films were observed by scanning electron microscopy (SEM). The chemical compositions of films were characterized by energy dispersive spectroscopy (EDS). It was found that the thickness of Cu-In films deposited on molybdenum-coated soda lime glass were approximately 1 μm. The EDS analysis showed the composition ratio in atomic % of Cu/In as approximately as 0.77. The XRD results reveal that the as-deposited Cu-In films consist of a mixture of copper oxide (CuO) and indium oxide (In2O3) phase at the annealing temperature of 500°C. Furthermore, CuO and In2O3 phase were converted to (112) oriented chalcopyrite copper indium diselenide after selenization process.

Water Absorption and Phase Transition of Calcium Carbonate in the Sea Water Mussel (Anadara Granosa)

The main purpose of this work is to study the structure of Anadara granosa shell sample and its structural transformation upon heat treatments. The sample was ground and characterized as powder throughout this work. Structural identifications of all samples were characterized, and determined qualitatively by using X-ray diffraction, IR spectroscopy and thermogravimetry measurement (TGA). It was found that the specimen is made of aragonite, a common phase of CaCO3 mineral. The powder sample was annealed at specific temperatures over the range of 200°C - 900°C and the effects of heat treatment on the structure of Anadara granosa shell samples were studied. The results show that aragonite transforms to calcite at the temperatures between 200°C and 400°C and completely becomes calcite between 400-500°C. Then, the calcite transforms to calcium oxide at the temperatures between 500°C - 900°C. The exact structures and quantities of phase at different annealing temperatures were studied by Rietveld refinement. In our study, we also used IR spectroscopy and TGA to study the effect of water absorption of the samples on the phase transformation.

Structural and Optical Properties of Zn0.8Co0.2O Ceramics

The Zn0.8Co0.2O ceramics were synthesized by the solid state reaction method with the mixture of ZnO and CoO powders. The mixed powders were sintered at 1200 °C and 1300 °C for 4 hours. It was found that the X-ray diffraction patterns of Zn0.8Co0.2O ceramics were similar to that of the pure ZnO one. The crystal structure of Zn0.8Co0.2O ceramics were then determined using the Rietveld full-profile analysis method to indicate a single phase with a wurtzite-like structure. Their microstructures were examined using the scanning electron microscopy. The results showed that their grain sizes were increased with increasing both the sintering temperatures and the doping effect. Moreover, the optical absorption spectra using UV-Vis spectrometer showed that there were several extra absorption bands appearing in the Zn0.8Co0.2O samples. This confirms that Co2+ is substituted Zn2+ in the wurtzite structure.