In pressurised water reactors (PWRs), hydrogen overpressure is used to keep the corrosion potential below the threshold for onset of intergranular stress corrosion cracking (IGSCC) in type 304 SS. However, some regions may contain higher oxygen levels resulting in an increase in the potential. These 'dead space' regions are difficult to access and during refuelling; oxygen may become trapped in these locations. The objective of this study was to investigate the influence of PGM additions on IGSCC susceptibility of type 304 stainless steels (SS) in the sensitised state within PWRs. The work presented herein investigates several aspects of the IGSCC problem. Virgin and platinum group metal (PGM)-modified (Ru and Pd) 304 SS have been studied. Material characterisation, including microstructural, tensile properties, hardness and grain size measurements, has been conducted. Crack initiation studies using U-bend samples in autoclaves simulating PWR environments have also been performed. In addition, crack propagation studies using circumferential cracked bar (CCB) specimens under constant extension in potassium tetrathionate solutions, a well-known medium to promote IGSCC on sensitised stainless steels, have been conducted in order to evaluate cracking resistance. Electrochemical studies using model solutions for PWR chemistry (containing boric acid and lithium hydroxide) and also potassium tetrathionate were carried out to look at the influence of the PGM on the kinetics of the main electrochemical reactions. The results revealed that PGM additions appeared to reduce crack initiation on sensitised type 304 SS under oxygenated conditions in high temperature water containing sulphate and chloride. PGM-doped and standard sensitised type 304 stainless steels revealed susceptibility to IGSCC propagation in 0.01 M K2S4O6, at pH=1.5 and 25°C. Electrochemical studies in potassium tetrathionate media showed smaller anodic dissolution peaks with PGM additions and metallography indicated less intergranular attack with PGM additions. In PWR model electrolytes, PGM additions, particularly 1 wt% Ru, were shown to catalyse the oxygen reduction reaction or hydrogen oxidation reaction, depending on the oxygen /hydrogen level. Overall findings showed that Ru additions can improve the IGSCC resistance of sensitised type 304 SS in PWR, while Pd additions are less effective.

Student Number : 0006342N - PhD thesis - School of Chemistry - Faculty of Science / An improved slurry method for determination of PGMs, gold and base metals (Ni, Cu, Fe and Co) using ICP-OES analytical instrument has been developed. This method has been successfully applied to quantitate metals in mineral concentrates and biological samples (grass, lichens, leaves and tree trunks) and validated using analytical figure of merit that include limits of detection, limits of quantition, accuracy and precision. Sample grinding using Fritsch GmbH Pulverissette Planetary Mono Mill was optimized to get > 60% and >80% of the particles to < 5.0 μm and < 10 μm respectively. The optimum grinding conditions for a sample mass of 0.4 g was determined as 130 rpm grinding speed and 30 minutes grinding time. An additional 15 minutes mixing with reagent was employed to ensure better slurry homogeneity for improved precisions. Five slurry dispersants; tetrasodium pyrophosphate, Triton X-100, dodecylbenzene sulfonic acid sodium salt, potassium cyanide and potassium thiocyanate, were evaluated at varied concentrations and 0.1% v/v Triton X-100 established as the best dispersant for slurry preparation. The ICP-OES sample delivery system was modified by introducing an extension elbow between the torch and the spray chamber that not only effectively reduced the sample residence time in the plasma for efficient atomization of the particles but also acted as a gravitational sieve eliminating larger particles and droplets. Prepared slurries were continuously agitated using an ultrasonic bath prior to and during aspiration into ICP-OES to prevent sedimentation and ensure constant stability of the slurry. Optimum operating conditions for ICP-OES established as 1600 W and 1450 W plasma power for PGMs and base metals respectively, using a nebulizer flow rate of 0.8 mL min-1, coolant gas flow rate of 13.0 mL min-1, auxiliary gas flow rate of 1.0 L min-1 with a sample uptake rate of 0.2 mL min-1. Limits of detection for the developed technique were determined in μg g-1 as 0.075, 0.039, 0.115, 0.071, 0.035 and 0.118 for Au, Ir, Pd, Pt, Rh and Ru respectively and 0.15, 0.391, 0.345 and 0.217 for Ni, Cu, Fe and Co respectively. Limits of quantitation in μg g-1 were obtained as 0.250, 0.130, 0.383, 0.237, 0.117 and 0.393 for Ir, Pd, Pt, Rh and Ru respectively and 0.5, 1.31, 1.15 and 0.723 for Ni, Cu, Fe and Co respectively. Good accuracy was recorded for all the base metals as well as for the platinum group metals and gold except iridium that was susceptible to copper interference. Two measurements of precision, reproducibility and repeatability were assessed. Reproducibility was obtained in percentages as 12, 7.93, 5.54, 10 and 12 for Au, Pd, Pt, Rh and Ru respectively and 9.9, 10, 9.8 and 10 for Ni, Cu, Fe and Co respectively. Repeatability was obtained in percentages as 11, 7.03, 4.94, 8.08 and 9.85 for Au, Pd, Pt, Rh and Ru respectively and 9.4, 9.6, 9.7 and 10 for Ni, Cu, Fe and Co respectively. Good percentage recoveries were obtained of 104.3%, 98.3%, 98%, 90.5% and 92.8% for Au, Pd, Pt, Rh and Ru respectively. Percentage recoveries of 109%, 111%, 89.9% and 100% for Ni, Cu, Fe and Co respectively were obtained. The simplicity and low cost of sample preparation used in this method enables it to be easily adopted in any ICP-OES laboratory. A single analyst may achieve more sample through-puts than before per day (including re-grinding and analysis), resulting in a highly economical and rapid technique for determination of metals.

Philosophiae Doctor - PhD / Nowadays, the pollution of surface waters with chemical contaminants is one of the most crucial environmental problems. These chemical contaminants enter rivers and streams resulting in tremendous amount of destruction, so the detection and monitoring of these chemical contaminants results in an ever-increasing demand. This thesis describes the search for a suitable method for the determination of platinum group metals (PGMs) in environmental samples due to the toxicity of mercury films and the limitations with methods other than electroanalytical methods. This study focuses on the development of a novel bismuth-silver bimetallic nanosensor for the determination of PGMs in roadside dust and soil samples. Firstly, individual silver, bismuth and novel bismuth-silver bimetallic nanoparticles were chemically synthesised. The synthesised nanoparticles was compared and characterised by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), ultraviolet-visible spectroscopy (UV-Vis), Fourier-transformed infrared spectroscopy (FT-IR), Raman spectroscopy, and transmission electron microscopy (TEM) analysis to interrogate the electrochemical, optical, structural, and morphological properties of the nanomaterials. The individual silver, bismuth, and bismuth-silver bimetallic nanoparticles in the high resolution transmission electron microscopy results exhibited an average particle size of 10-30 nm. The electrochemical results obtained have shown that the bismuth-silver bimetallic nanoparticles exhibit good electro-catalytic activity that can be harnessed for sensor construction and related applications. The ultraviolet-visible spectroscopy, Fourier-transformed infrared spectroscopy, and Raman spectroscopy results confirmed the structural properties of the novel bismuth-silver bimetallic nanoparticles. In addition the transmission electron microscopy and selected area electron diffraction morphological characterisation confirmed the nanoscale nature of the bismuth-silver bimetallic nanoparticles. Secondly, a sensitive adsorptive stripping voltammetric procedure for palladium, platinum and rhodium determination was developed in the presence of dimethylglyoxime (DMG) as the chelating agent at a glassy carbon electrode coated with a bismuth-silver bimetallic nanofilm. The nanosensor further allowed the adsorptive stripping voltammetric detection of PGMs without oxygen removal in solution. In this study the factors that influence the stripping performance such as composition of supporting electrolyte, DMG concentration, deposition potential and time studies, and pH have been investigated and optimised. The bismuth-silver bimetallic nanosensor was used as the working electrode with 0.2 M acetate buffer (pH = 4.7) solution as the supporting electrolyte. The differential pulse adsorptive stripping peak current signal was linear from 0.2 to 1.0 ng/L range (60 s deposition), with limit of detections for Pd (0.19 ng/L), Pt (0.20 ng/L), Rh (0.22 ng/L), respectively. Good precision for the sensor application was also obtained with a reproducibility of 4.61% for Pd(II), 5.16% for Pt(II) and 5.27% for Rh(III), for three measurements. Investigations of the possible interferences from co-existing ions with PGMs were also done in this study. The results obtained for the study of interferences have shown that Ni(II) and Co(II) interfere with Pd(II), Pt(II) and Rh(III) at high concentrations. The interference studies of Cd(II), Pb(II), Cu(II) and Fe(III) showed that these metal ions only interfere with Pd(II) and Pt(II) at high concentrations, with no interferences observed for Rh(III). Phosphate and sulphate only interfere at high concentrations with Pt(II) and Rh(III) in the presence of DMG with 0.2 M acetate buffer (pH = 4.7) solution as the supporting electrolyte. Based on the experimental results, this bismuth-silver bimetallic nanosensor can be considered as an alternative to common mercury electrodes, carbon paste and bismuth film electrodes for electrochemical detection of PGMs in environmental samples. Thirdly, this study dealt with the development of a bismuth-silver bimetallic nanosensor for differential pulse adsorptive stripping voltammetry (DPAdSV) of PGMs in environmental samples. The nanosensor was fabricated by drop coating a thin bismuth-silver bimetallic film onto the active area of the SPCEs. Optimisation parameters such as pH, DMG concentration, deposition potential and deposition time, stability test and interferences were also studied. In 0.2 M acetate buffer (pH = 4.7) solution and DMG as the chelating agent, the reduction signal for PGMs ranged from 0.2 to 1.0 ng/L. The detection limit for Pd(II), Pt(II) and Rh(III) was found to be 0.07 ng/L, 0.06 ng/L and 0.2 ng/L, respectively. Good precision for the sensor application was also obtained with a reproducibility of 7.58% for Pd(II), 6.31% for Pt(II) and 5.37% for Rh(III), for three measurements. In the study of possible interferences, the results have shown that Ni(II), Co(II), Fe(III), Na+, SO42- and PO43- does not interfere with Pd(II) in the presence of DMG with sodium acetate buffer as the supporting electrolyte solution. These possible interference ions only interfere with Pt(II) and Rh(III) in the presence of DMG with 0.2 M acetate buffer (pH = 4.7) as the supporting electrolyte solution.

As the role of technology within warfare continues to increase, it is important to investigate whether or not the consequences of these weapons are being adequately considered. The use of new weapons technologies, such as Unmanned Combat Aerial Vehicles and Precision Guided Munitions, have been both praised and condemned within the war in Afghanistan. Although praised as saving civilian lives due to the precision capabilities of the weaponry there are consistent civilian deaths attributed to these weapons systems. This study examines debates regarding new weapons technologies that have been utilised during the war in Afghanistan. Current literature regarding emerging weapons technology is examined in order to identify key debates. The literature was recognised as falling predominantly within three perspectives - strategy, law and ethics. By identifying the key debates within each perspective it is possible to identify where these debates overlap or diverge. This research concludes that the introduction of counterinsurgency strategy to modern warfare has led to an increasing concern with the ethical and legal dimensions of the debate surrounding new weapons technology.

In this study, a reversed-phase high performance liquid chromatography (RP-HPLC) method has been developed to separate and determine Pt and Pd after formation of their chelates with N,N-diethyl-N&#039 / -benzoylthiourea (DEBT). With the aim of reducing the number of steps in treating the samples, the method developed does not require the elimination of excess chelating reagent before the analysis of metal chelates. The different physical and chemical parameters affecting separation were examined in details. The whole analysis was completed on a C18 column in 16 min at 280 nm, with the mobile phase of acetonitrile-methanol-water (80:10:10, v:v:v) containing 0.20 mol l-1 pH 5.0 acetate buffer at a flow rate of 0.8 ml min-1. Detection limits of the method, based on 3s, were found as 14.2 ug l-1 for Pd and 0.77 mg l-1 for Pt using a 20-ul sample loop. Reproducibility of the method for ten repeated measurements was found as 2.36 % for 0.60 mg l-1 Pd and 2.58 % for 10.0 mg l-1 Pt as % RSD. The proposed method is a rapid, simple and highly selective method for the simultaneous determination of Pt and Pd by HPLC without the need for any interference elimination process.

Thesis (M. Sc.(Geography)) -- University of Limpopo, 2019 / Global production of Platinum Group Metals (PGMs) is dominated by South Africa due to its large economic resources base in the Bushveld Igneous Complex (BIC). PGMs are used in a wide range of high technology applications worldwide including medicinal, industrial and commercial purposes, and its contribution to the Gross Domestic Product (GDP) and creating jobs for many. In an area where mining activities dominate, there are likely to be problems that need effective environmental management approaches, which can be facilitated through legislations. Marula Platinum Mine (MPM) is located in Limpopo province BIC which has the second largest number of mining productivity in South Africa. Environmental legislations have been put in place by the South African government in order to avoid or minimise the footprints caused by PGM mining. This study looked at environmental compliance with solid waste management practices by Marula Platinum Mine (MPM) as guided by Mineral and Petroleum and Resource Development Act (MPRDA) and National Environmental Management Act (NEMA) as well as the environmental impacts of MPM in the surrounding communities. Both primary (questionnaires, field observations and key informant interviews) and secondary (NEMA, MPRDA, journals, reports, pamphlets, internet and books) data was used to address the objectives of the study. Descriptive method and Statistical Package for Social Sciences (SPSS) version 25 were used for the analysis of data. The key research results revealed that MPM was compliant with 65% and 21% partially compliant with solid waste management practices. Only 14% of information on solid waste management practices could not be accessed because MPM is still operational. MPM had also had negative footprints on the surrounding villages such as dust generation and cracks on walls and floors on houses of community members, strikes and increase in the usage of substance abuse. Recommendations of the study are that MPM should address challenges that hinder environmental compliance so as to be 100% compliant with MPRDA and NEMA regulations. MPM should also provide other mitigation measures for blasting of explosives to reduce dust generation and problems of cracks on houses of surrounding village members.