Effect of annealing temperature on thermoluminescence glow curve for UV and gamma ray induced ZrO2:Ti phosphor

THERMOLUMINESCENCE AND KINETIC PARAMETERS OF MICRO-NANO MATRIX OF LITHIUM TRIBORATE AND ZINC OXIDE NANOPARTICLE

This study presents the first report on the kinetic parameters of micro-nano interaction of lithium triborate microparticles doped with zinc oxide nanoparticles (LBZ) in 0.1 to 0.4% dopant concentrations. The parent-dopant mix was synthesized using high-temperature solid-state method. The materials were subjected to X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and differential thermal analysis (DTA) to ascertain their structural, physical properties as well as gamma irradiation and thermoluminescence (TL) analysis for their dosimetric properties. XRD and DTA confirmed the formation of polycrystalline lithium triborate compounds, while SEM and EDS showed the presence of the dopant. TL analysis presented a simple glow curve structure with the main temperature peak for different dopant concentrations varying from 243 to 327°C. The activation energy (E) and frequency factor (s) were calculated for each peak shape parameter τ (low temperature half width), δ (high temperature half-width) and ω (total half width) using Chen's peak shape (PS) method and the order of kinetics was deduced from the symmetry factor (μg) and gamma dose-response curves. The activation energy and frequency factor with respect to the peak shape parameters Eτ, Eδ, Eω and sτ, sδ, sω across the dopant concentrations were in the range of 1.14 to 2.2 eV and 3.92 × 1010 to 7.71 × 1022 s-1, respectively. Comparing the methods for the determination of the order of kinetics, LBZ 0.2% agrees with the conditions of first-order kinetics, while second-order kinetics is assigned to LBZ 0.1, 0.3 and 0.4%. The results present simple glow curve structure which relates to stability, high-temperature peaks and E values which correspond to deep trap states.

Enhanced thermoluminescence of magnesia-doped zirconia nanoparticles exposed to ultraviolet/beta irradiation

In this study, magnesia-doped zirconia nanoparticles were synthesized via the sol-gel method, and this was followed by pellet manufacturing for ultraviolet (UV) and beta ray dosimetry. The raw materials included zirconium(IV) propoxide, isopropyl alcohol, acetic acid, nitric acid, and magnesium nitrate hexahydrate. Taguchi experimental design with an L9 orthogonal array and variance analysis was used to optimize the essential parameters and achieve the smallest sol average particle size. Isopropyl alcohol to zirconium(IV) propoxide (ISP/ZPP) volume ratio, MgO mole ratio, and reaction temperature were the three critical factors considered in this study. The sol average particle size, type of molecule bonds in the gel, calcination temperature, phase study, morphology, and thermoluminescence properties were determined by a wide range of analyses such as dynamic light scattering, Fourier-transform infrared spectroscopy, static timing analysis, x-ray diffraction, field-emission scanning electron microscopy, and thermoluminescent dosimetry (TLD). The optimized conditions for obtaining the smallest sol average particle size were an ISP/ZPP volume ratio of 30, 3% magnesium mole, and 70 °C reaction temperature. The ISP/ZPP volume ratio, with 51.38% participation, was identified as the most influential parameter. The crystallization temperature occurred at 560 °C, showing the tetragonal phase. The average crystalline size was found to be 15 nm. TLD analysis showed that the prepared pellets were 250 times more sensitive than pure zirconia synthesized via the same method, and displayed two thermoluminescent (TL) maxima located at 130 °C and 185 °C for UV irradiation, and one TL maximum for beta irradiation located at 180 °C. The presence of relatively low-temperature peaks and high sensitivity in both UV and beta irradiation suggested that magnesia-doped zirconia pellets can be suitable candidates for dosimetry applications.

Determination of (226)Ra, (232)Th, (40)K, (235)U and (238)U activity concentration and public dose assessment in soil samples from bauxite core deposits in Western Cameroon

Determination of activity concentrations in twenty five (25) soil samples collected from various points in bauxite ore deposit in Menoua Division in Western of Cameroon was done using gamma spectrometry based Broad Energy Germanium (BEGe6530) detector. The average terrestrial radionuclides of (40)K, (226)Ra, (232)Th, (235)U and (238)U were measured as 671 ± 272, 125 ± 58, 157 ± 67, 6 ± 3 and 99 ± 69 Bq kg(-1), respectively. The observed activity concentrations of radionuclides were compared with other published values in the world. The outdoor absorbed dose rate in air varied from 96.1 to 321.2 nGy h(-1) with an average of 188.2 ± 59.4 nGy h(-1). The external annual effective dose rate and external hazard index were estimated as 0.23 ± 0.07 mSv year(-1) for outdoor, 0.92 ± 0.29 mSv year(-1) for indoor and 1.13 for the external hazard index, respectively. These radiological safe parameters were relatively higher than the recommended safe limits of UNSCEAR. Consequently, using of soil as building material might lead to an increase the external exposure to natural radioactivity and future applications research need to be conducted to have a global view of radioactivity level in the area before any undergoing bauxite ore exploitation.