A Photo and Thermally Stimulated Luminescence Study of BaCl2:Eu2+ with Application to Neutron Imaging

<p>This thesis presents the results of a photo and thermally stimulated luminescence study of europium-doped barium chloride in relation to its potential application as a storage phosphor in glass ceramics for radiation imaging, particularly for neutron imaging. Previous work done on lithium borate (LiBO) glasses containing BaCl2:Eu2+ nanocrystals at Victoria University of Wellington had demonstrated comparable imaging capability with commercially available BaFBr:Eu2+ based imaging plates, though the sensitivity and spatial resolution were inferior to that material, and there was a substantial afterglow during the read-out process which degraded any image. These problems are addressed here. The effect of various different co-dopants on the storage properties was examined using the thermally stimulated luminescence (TSL) technique, with dopants primarily chosen from the alkali and alkaline earth elements. The resulting glow curves have been analysed to determine the activation energies associated with the various traps, and tentative assignments of structural defects to the various glow curve peaks are proposed. It was found that Li+ and Na+ gave small increases (20% and 50% respectively) in efficiency, though other dopants tended to reduce the overall output. In particular, K+ and Rb+ were found to substantially reduce the output efficiency. It was found that Li+ co-doped BaCl2:Eu2+ contained thermally unstable traps which at room temperature could result in the observed afterglow in LiBO/BaCl2 glass ceramics through a read-out induced phototransfer process. The experimental measurements required substantial hardware and software development of the existing VUW facilities for TSL, and these improvements are also described here. The most significant improvements are an extension of the operating range at the lower end of the existing TSL spectrometer to -50 degrees C through a cooled gas flow system, and the engineering of a completely new system to record TSL from 25 K to 400 K.</p>

A Photo and Thermally Stimulated Luminescence Study of BaCl2:Eu2+ with Application to Neutron Imaging

<p>This thesis presents the results of a photo and thermally stimulated luminescence study of europium-doped barium chloride in relation to its potential application as a storage phosphor in glass ceramics for radiation imaging, particularly for neutron imaging. Previous work done on lithium borate (LiBO) glasses containing BaCl2:Eu2+ nanocrystals at Victoria University of Wellington had demonstrated comparable imaging capability with commercially available BaFBr:Eu2+ based imaging plates, though the sensitivity and spatial resolution were inferior to that material, and there was a substantial afterglow during the read-out process which degraded any image. These problems are addressed here. The effect of various different co-dopants on the storage properties was examined using the thermally stimulated luminescence (TSL) technique, with dopants primarily chosen from the alkali and alkaline earth elements. The resulting glow curves have been analysed to determine the activation energies associated with the various traps, and tentative assignments of structural defects to the various glow curve peaks are proposed. It was found that Li+ and Na+ gave small increases (20% and 50% respectively) in efficiency, though other dopants tended to reduce the overall output. In particular, K+ and Rb+ were found to substantially reduce the output efficiency. It was found that Li+ co-doped BaCl2:Eu2+ contained thermally unstable traps which at room temperature could result in the observed afterglow in LiBO/BaCl2 glass ceramics through a read-out induced phototransfer process. The experimental measurements required substantial hardware and software development of the existing VUW facilities for TSL, and these improvements are also described here. The most significant improvements are an extension of the operating range at the lower end of the existing TSL spectrometer to -50 degrees C through a cooled gas flow system, and the engineering of a completely new system to record TSL from 25 K to 400 K.</p>

Geochemical Maturity and Paleo-Weathering Indices of Sedimentary Succession in JV Field Greater Ughelli Depo-Belt Niger Delta Basin

This study evaluates the geochemical maturity and paleo weathering indices of X well JV-Field, Greater UghelliDepo belt Niger Delta Basin, using reflected light microscope and geochemical proxies. The data obtained identified three lithofacies units as Sand, Shale, and Shaly sand facies .The application of source area weathering using Chemical index of alteration (CIA) and Chemical index of weathering (CIW) values for the sampled intervals ranges from (48.6-94.9%) and (60.6-96.7%), and have median values of (83.2 and 90.3) % respectively which is an indication of high weathering at the source. The values are variable and it may be as a result of multiple provenances of the sediments which have variable proportions of source area weathering and related processes or may be due to low concentrations of the alkalis and alkaline earth elements. However, all the samples excluding one with depth (12430ft) show CIA and CIW values greater than 70% indicating high (intensive) weathering either at the source or during transportation before deposition .From the high alteration indices value recorded from the sampled intervals, it can be inferred that the sediments are geochemically and texturally mature.

The series of measures for improvement of safety in oil and gas facilities producing, processing and transporting materials containing hydrogen sulfide Part 1. Corrosion-mechanical attack of hydrogen sulfide-containing media on steel equipment. The choice of construction steels and noncorrosive alloys for the oil and gas equipment

The necessity of the complex approach is defined for increase of reliability of the oil and gas equipment operated under pressure of hydrogen sulfide-containing medium, including: - control at the stages of design, manufacturing, commissioning, operation, repair and reconstruction; - organization of corrosion service; - rational choice of materials for equipment manufacturing and its repair; - use of different methods to protect equipment against corrosion: - diagnostics of equipment and evaluation of corrosion protection efficiency; - conducting corrosion tests of materials and corrosion control. The trend of increasing corrosive activity of the products of a number of hydrogen sulfide-bearing oil and gas fields is described. This is associated with their watering and contamination by sulfate-reducing bacteria. All types of corrosion-mechanical damage of steels in accordance with GOST R 53679-2009 (ISO 15156-1:2001) are considered. Comments are given on each of these types of damage and the types of steels that are prone to these defects are shown. The recommendations of GOST R 53679-2009 (ISO 15156-1:2001) are given for the selection of steel equipment operated under pressure of hydrogen sulfide-containing media depending on the type of their corrosionmechanical failure, with comments. Requirements for the use of steels modified with rare-earth metals (REM) and alkaline-earth elements (ALE) intended for operation in hydrogen sulfide-containing media are given.

The Effect of Alkaline Earth (Ba, Sr and Ca) Doped Iron Bismuth Glasses on The Structural, Thermoelectric and Electrical Properties

Glasses with nominal composition 70Bi2O3-30Fe2O3 and 10A-60Bi2O3-30Fe2O3 (mol%); (A = Ba, Sr and Ca) were prepared by the conventional melt quenching technique. X-ray diffraction (XRD) and Differential scanning calorimeter (DSC) confirm the amorphous nature of the glass samples. The iron-bismuth glasses show good solubility of alkaline earth elements ions. In temperatures range of 310–450 K, the dc conductivity of the glass samples containing alkaline earth elements enhanced. Glass sample containing Sr shows interesting electrical properties. All glass samples showed a transition from negative to positive Seebeck coefficient, this means that the conduction is mixed of electrons and holes charge carriers. The conduction mechanism of all samples obeys non-adiabatic small polaron hopping model of electron between iron ions. The calculated small polaron coupling constant, (γp) was found to be in the range of 10.25–17.28. Also, the calculated hopping mobility (µ) and carrier density (Nc) of glasses were in the range of 4.65\(\times {10}^{- 7}\)- 4.11\(\times {10}^{-3}\left({\text{c}\text{m}}^{2}{\text{V}}^{-1}{\text{s}}^{-1}\right)\) and 0.029-10 \(\left({\times {10}^{1 7}\text{c}\text{m}}^{-3}\right)\) at 333 K, respectively.

APPLICABILITY ASSESSMENT OF NATURAL WATERS IN IRRIGATION OF AGRICULTURAL LAND ON THE EXAMPLE OF THE VAKHSH RIVER AND ITS TRIBUTARIES

The results of chemical analyses of the Vakhsh river and its tributaries and the calculations of the main criteria for the water applicability for irrigation purposes are presented: the proportion of sodium cations capable of absorption, dissolution, ion exchange, and the proportion of magnesium. It was found that the waters of the Vakhsh river and its tributaries (Kyzylsu, Muksu, Obikhingou and Surkhob) are favorable for irrigation of agricultural land. On the values of the magnesium cations ratio to calcium cations the Vakhsh river and tributaries water correspond to the first class of «soft waters». It is shown that due to the surface and underground water exchange, underground water reservoirs are enriched by cations of alkaline and alkaline earth elements. The underground water reservoirs of the Vakhsh tributaries basin on the water quality terms are also suitable for irrigation purposes.