Hydroxyapatite was synthesized using calcium originated from waste eggshell that was reacted with phosphate obtained from diammonium hydrogen orthophosphate by ball milling technique. The samples were mixed at different time from 5 to 150 min. The structure, function group and morphology of hydroxyapatite were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FE-SEM). The result showed that the hydroxyapatite phase was appeared after ball milling about 5 min and confirmed with FTIR results. The FE-SEM of hydroxyapatite powder was spherical shape and agglomerate. The crystallinity of hydroxyapatite was increased with increasing ball milling time. This experiment showed that the nano hydroxyapatite could synthesized from waste eggshell by ball milling technique.

Abstract. The purpose of this study was to evaluate the radionuclide concentrations of London blue topaz after fast neutron irradiation. The London blue topaz was obtained from Sri Lanka which classified into dark and light colors in the shape of an oval and rectangle with small, medium and large size. The optical property and radionuclide concentrations of London blue topaz have been examine by UV-Visible spectroscopy and HPGe gamma ray spectrometry, respectively. The UV-absorption spectra of topaz was taken in the range of 300 to 800 nm at room temperature. The results showed that the absorption peak of topaz was observed with only broad peaks in the range of 550 to 700 nm and 630 nm that correlated to the O -center in hydroxyl sites which substitutes for fluorine in topaz structure. The radioactivity of dark and light colors in the shape of an oval and rectangle London blue topaz was in the range of 1.437  0.014 to 21.551  0.037 nCi/g (oval dark), 2.958  0.031 to 6.748  0.054 nCi/g (oval light) and 2.350  0.014 to 43.952  0.088 nCi/g (rectangle dark), 1.442  0.023 to 6.748  0.054 nCi/g (rectangle light), respectively. The decay rates of 46 Sc, 182 Ta and 54 Mn isotopes created by irradiation showed that the decay time of the radioactive element depended on the size of the topaz so increased with decreasing the size of topaz. Moreover, the size of topaz also affect the absorption coefficient. This study is applied to predict time of residue dose of topaz for enhancement colorless topaz by neutron radiation treatment.

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The nanocrystalline ZnO powders were synthesized by a direct thermal decomposition using zinc acetate dihydrate as starting materials. The precursor was characterized by TG-DTA to determine the thermal decomposition and crystallization temperature which was found to be at 300 °C. 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.

In the present work, colorless topaz was designed and developed a dosimeter for routine application. The samples were irradiated with gamma from 60Co at dose range 50 - 400 Gy and investigated by thermoluminescence (TL) and electron spin resonance (ESR). The TL grow curve of topaz were revealed two trapping levels at temperature 150 °C and 225 °C. The ESR signals of topaz shown that the g value at 1.966 and 2.012 due to Ti3+ and (AlO4)0 center, respectively. The intensities of TL and ESR were increased with increasing dose. The percentage error of dose from TL and ESR signal were 8 and 3, respectively. These experiment indicated that the colorless topaz could be used as a dosimeter.