Supphadate Sujinnapram

Characterization of Apatite from Human Teeth via XRD, FT-IR and TGA Techniques

Human teeth (HT) are natural composites which consist of nanohydroxyapatite (HAp) arranged in lamellae and bound to collagen. In present study, prepared HT powders with different ages were characterized by X-Ray Diffraction (XRD), Fourier transform infrared (FT-IR) and thermogravimetric anlysis (TGA) techniques. HT at age ranges of 1-10, 11-20, 21-30, 31-40, 41-50 and 51-60 years old were selected for tests. To prepare samples, human teeth were washed in boiling water for 1 h and left in 1 M KOH solution for 6 h to remove any organic material. After HT samples were cleaned with ultrasonic in ethanol, they were then finely grounded using agate mortar. The results from XRD indicate that the major diffraction peaks of all samples with different ages were very closely identified to that of stoichiometric HAp. All HT powders were found to be nanocrystalline structure. Furthermore, it was found that the decrease in HAp crystallinity seem to increase with higher age of 31-40 years old. To investigate chemical structure confirmed by FT-IR, All HT powders showed the band positions and function groups, which are similar to that of HAp. group found in chemical structure indicates the structure of carbonated apatite. TGA results were found that the increase of weight loss seem to increase with higher age.

The Preparation and Characterization of Y145 Superconductor

In this research, we synthesized and characterized the physical properties of YBa2Cu3Ox (Y123) and YBa4Cu5Ox (Y145) superconductors by solid state reaction and melt process. The raw materials Y2O3, BaCO3 and CuO were mixed, ground and react in the air atmosphere at 950 °C, at 980 °C for solid state reaction and melt process, respectively. The samples obtained were characterized by the resistivity measurement, SEM, EDX, XRD and DTA. It was found that the critical temperature onset of Y145 is 94 K and 96 K for solid state reaction and melt process, respectively. The samples were inhomogeneous with no impurity. The crystal structures was orthorhombic which a = 3.80446 Å, b = 3.86474 Å and c = 19.37104 Å for Y145 solid state reaction and a = 3.80180 Å, b = 3.86483 Å and c = 19.38194 Å for melt process. The peritectic temperature of Y145 is 1018 °C.

An improvement of dye-sensitized solar cell by acid treatment on modified ZnO photoanode

ABSTRACT An acid treatment of ZnO films was presented using HCl and HNO3 to improve the ZnO surface properties for applying a photoanode in dye-sensitized solar cell. Scanning electron microscope (SEM) image showed that the ZnO films changed after the treatment. Pore area and pore density were increased and a significant decrease in reflectance was observed. The treated films were used as photoanode of dye-sensitized solar cell and efficiency was enhanced. The maximum efficiencies were 0.73% and 0.89% for optimal HCl and HNO3 treatment compared with the non-treated photoanode of 0.64%. The efficiency was enhanced directly correlated to fill factor achievement. The achievement of fill factor was caused by an increase of pore area and pore density which lead an improvement of photoanode/dye/electrolyte interface. These results implied that HCl and HNO3 have potential to improve porous property of ZnO film for dye-sensitized solar cell application.

Some properties of YBamCu1+mOy(m = 2, 3, 4, 5) superconductors

We synthesized the YBamCu1+mOy superconductors; m = 2,3,4,5 that were Y123 (YBa2Cu3O7-x), Y134 (YBa3Cu4O9-x), Y145 (YBa4Cu5O11-x), Y156 (YBa5Cu6O13-x), by solid state reaction with the Y2O3, BaCO3 and CuO as the beginning materials. The calcination temperature was 950 C and varied the sintering temperature to be 950 C and 980 C. The resistivity measurement by four-point-probe technique showed that the Tconset of Y123, Y134, Y145, Y156 were at 97 K, 93 K, 91K, 85 K, respectively. The XRD and Rietveld full-profile analysis method were used and found that the crystal structure was in the orthorhombic with Pmmm space group with the ratio c/a were 3.0, 4.0, 5.0 and 6.0 for Y123, Y134, Y145 and Y156, respectively. The oxygen content was characterized by Iodometric titration. The (Cu3+/Cu2+and Oxygen content) were (0.28, 6.83), (0.19, 8.81), (0.13, 10.79), (0.16, 12.92) of Y123, Y134, Y145, Y156 respectively. We also found that the increasing of sintering temperature has reduced the oxygen content and the critical temperature of all samples.

Investigate the Properties of Y211 Doping Effect in the New Superconducting Y7Ba11Cu18Oy Compound

The new superconductors of Y-based compound, Y7Ba11Cu18Oy(Y7-11-18), has been discovered by solid state reaction with the different ratios of raw materials. All obtained samples were analyzed and characterized by XRD and the FULLPROF program. The lattice parameters of Y7-11-18 were a=3.8268 Å, b=3.8810 Å and c= 69.8794 Å. The Y7-11-18 showed the sharp transition curve of resistivity (ρ) at the critical temperature (Tc) =94 K. The doping of Y2BaCuO5 (Y211) showed that the higher Y211, the lower Tc and c lattice parameter. The SEM and EDX micrographs showed the grain size about 1-5 μm and without impurities. The DTA analysis resulted the decreasing of peritectic temperature from 962.74 °C by the higher Y211 contents.

Synthesis and Characterization of Nanocrystalline ZnO Powders by a Direct Thermal Decomposition Route Using Zinc Nitrate Hexahydrate

The nanocrystalline ZnO powders were synthesized by a direct thermal decomposition using zinc nitrate hexahydrate as starting materials. The precursor was characterized by TG-DTA to determine the thermal decomposition and crystallization temperature which was found to be at 325 oC. The precursors were calcined at different temperatures of 400, 500, and 600°C for 4 h. The structure of the prepared samples was studied by XRD, confirming the formation of wurtzite structure. The synthesized powders exhibited the UV absorption below 400 nm (3.10 eV) with a well defined absorption peak at around 285 nm (4.35 eV). The estimated direct bandgaps were obtained to be 3.19, 3.16, and 3.14 eV for the ZnO samples thermally decomposed at 400, 500, and 600°C, respectively.

Chemical vapor treatment of zinc oxide photoelectrodes for efficiency enhancement of dye-sensitized solar cells

ZnO photoelectrodes were successfully treated using hydrochloric vapor. The vapor was generated from hydrochloric acid solution with sonication assistance. The morphology showed a formation of plate-like structures after the vapor treatment, resulting in light scattering which was observed in terms of increased reflectance compared with the non-treated photoelectrodes. A dye-sensitized solar cell fabricated with the treated photoelectrodes exhibited an enhanced power conversion efficiency of 3.00% in comparison to the non-treated photoelectrodes base of 2.35%. The enhanced power conversion efficiency was observed in direct relation to the increased short-circuit current density. The increased short-circuit current density is due to the achieved light scattering in the photoelectrodes. Moreover, an extended open-circuit voltage was observed due to reduced electron recombination in the device. Therefore, a chemical vapor treatment of ZnO photoelectrodes via hydrochloric acid resulted in a successful scattering layer formation and a reduced recombination process for power conversion efficiency enhancement of ZnO dye-sensitized solar cells.Graphical abstract

Synthesized and characterization of YBa2Cu3Oy, Y3Ba5Cu8Oy, and Y7Ba11Cu18Oy superconductors by planetary high-energy ball-milling

The bulk samples of milled and unmilled synthesized by conventional solid-state reaction. The powder X-ray diffraction and Rietveld refinement software program characterized crystal structure. The elementary mapping technique was used EDXS. For the onset critical temperature (Tconset) and offset critical temperature (Tcoffset) the four-probes measurement method was utilized. The superconducting compound and non-superconducting compound were incorporated in the samples. The Y123 was highest superconducting compound and lowest the non-superconducting compound. The c lattice parameter of milled samples was longer than unmilled samples. The anisotropy parameter of the milled samples had a lower value than the unmilled samples. The mapping technique showed that the without any impurity and composite of Y, Ba, Cu, and O. The critical temperature of milled, Y358, and Y7-11-18 were higher than unmilled. Conversely, the critical temperatures of milled and unmilled Y123 were closed to Y358 and Y7-11-18.

KOH Treatment of Photoanode on Photovoltaic Properties of ZnO Based Dye-Sensitized Solar Cell

ZnO films were deposited on fluorine doped tin oxide glass substrate and chemically treated by KOH solutions. The films were immersed into 2 M KOH solution with various immersing time of 0-6 min at room temperature, rinsed and thermally treated. Small pore size was observed for treated films by scanning electron microscopy indicated that dense ZnO particles were removed. Eosin-Y sensitizer was loaded into treated photoanode using re-adsorption technique. The photovoltaic characteristics were investigated under standard light illumination (AM1.5). Short circuit current densities are not much changed for 0-4 min treatment. After then, it is rapidly decreased for 6 min treatment. Open-circuit voltage, fill factor and shunt resistance are increased after treatment. In addition, increased charge transfer resistance indicated that recombination is reduced by KOH solution treatment. The reduced recombination contributes efficient electrons transport through external circuit. These improvements resulting efficiency reached maximum value of 0.72% at 4 min treatment, compared with pristine cell efficiency of 0.64%.

Characterizations of YBa5Cu6Ox Superconductor Synthesized by Melt Process

The YBa5Cu6Ox (Y156) superconductors were synthesized by melt process method with sintering at 980 °C. The samples were characterized by the SEM, EDX, XRD and resistance measurement. The critical temperature onset () and the critical temperature offset () were found at 90 K and 80 K respectively. The crystal structures was orthorhombic performed by Rietveld full-profile analysis method with lattice parameter a = 3.80078 Å, b = 3.89068 Å and c = 22.94436 Å. The c/a ratio was 6.04 and the anisotropy was 2.33. The lower c/a ratio and higher anisotropic were found as increasing the sintering temperature with little change in a and b-axis value. We found that as increasing of sintering temperature, the critical temperature was decreased but the anisotropy was increased.