http://hdl.handle.net/10386/8 2026-04-07T09:14:22Z 2026-04-07T09:14:22Z Mojapelo, Semola Kabelo http://hdl.handle.net/10386/5408 2026-03-24T01:00:13Z 2025-01-01T00:00:00Z

The design, synthesis, and antitubercular properties of the tri-substituted benzofuran derivatives Mojapelo, Semola Kabelo Tri-Substituted benzofuran derivatives exhibit greater biological activities influenced by natural compounds with highest potency, selectivity, and multifunctionality. Naturally occurring benzofuran with hydroxyl, methoxy, phenyl modification in different position showed antimicrobial, anticancer, antitubercular, and neuroprotective activities. These modification groups can influence lipophilicity, binding affinity and membrane permeability of mycobacterium tuberculosis which impact bioactivity. The aim of the study was to design, synthesise, and evaluate the anti-tubercular properties of the tri-substituted benzofuran derivatives. 5-iodovanillin 1B was made by iodinating commercially available vanillin 1A in a 92% yield. 2-(substituted)-7-methoxybenzofuran-5-carbaldehydes 2A-2E were produced by a Sonogashira cross-coupling reaction with palladium using a variety of acetylenes in a 60–80% yield. 2-(substituted)-7-methoxybenzofuran-5-carbaldehydes (2A-2E) were reduced with sodium borohydride in ethanol at room temperature, producing 2-substituted-7-methoxybenzofuran-5-ylmethanols (3A-3E) in a 60–82% yield. The esterification of the 2-substituted-7-methoxybenzofuran-5-carbaldehydes 3A-3E was catalysed by a Mukaiyama catalyst with several carboxylic acids in dichloromethane at room temperature, producing esters 3A1-3E5 in 40–80% yields. FTIR and NMR spectroscopy were used to characterise each of the synthesised substances. The online platform ADMET3.0 was used to perform the ADMET characteristics of esters 3A1-3E5. The antimycobacterial, cytotoxic, and solubility properties of every synthesised compound were assessed biologically. Several trisubstituted benzofuran derivatives that were synthesised demonstrated antimycobacterium tuberculosis (Mtb H37Rv) activity. For example, compound 3B3 showed good activity in all three media used with less toxicity. Additionally, six compounds (2A, 3A, 3A2, 2B, 3B, and 3B1) showed solubility results ranging between 5-195 μM. Compound 3B showed the best solubility of 195 μM but poor antitubercular activity in all three media used. On the contrary, compound 2A showed promising antimycobacterial activity of 2.02-18.08 μM in two media but had poor solubility of less than 5 μM. Additionally, compound 3A2 demonstrated activity in one medium (7H9/CAS/Glu/Tx), whereas compound 3B1 demonstrated activity in two media (7H9/ADC/Glu/Tw and 7H9/ADC/Glu/Tx). Both compounds displayed comparable outcomes, including good solubility at 50 μM and cytotoxicity at or above 50 μM, respectively. Thesis (M.Sc. (Chemistry)) -- University of Limpopo, 2025

2025-01-01T00:00:00Z Maseko, Sibusiso http://hdl.handle.net/10386/5407 2026-03-24T01:00:20Z 2025-01-01T00:00:00Z

Geology, mineralogy and the occurrence of rare earth elements in the coal deposit at the Uitkomst Colliery (Utrecht Coalfield), Kwazulu-Natal, South Africa Maseko, Sibusiso The Utrecht Coalfield is one of the coalfields of the Main Karoo Basin, which is currently underexplored and there is no information regarding the REEs concentration. Before extracting the REEs, it is significant to examine the distribution and concentration of REEs within the host rock, in this case, coal. The purpose of the study is to explore the mineralogical and geochemical characteristics and occurrence of REEs in the coal deposits at the Utrecht Coalfield (Uitkomst Colliery). Seventeen samples from three different seams (Gus, Alfred, and Fritz) were analysed using petrography, ultimate analysis, proximate analysis, and X-ray diffraction (XRD) analysis. The REEs concentration in the samples was determined by inductively coupled plasma (ICP-MS) techniques, whereas scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) as a direct method and Pearson’s correlation as an indirect method was used to determine the mode of occurrence of the REEs in the samples from the Utrecht Coalfield. The Vryheid Formation in the Utrecht Coalfield consists of sandstones, siltstones, shale, and mudstone, with minor coal seams. The average thickness of the Eland, Fritz, Alfred, and Gus seams is 0.30 m, 0.21 m, 1.21 m, 1.12 m, and 1.26 m, respectively. The samples were dominantly inertinite rich with lesser liptinite and vitrinite macerals and were categorised as medium-rank- C. The Gus, Alfred and Fritz seams had an average ash content of 14.9%, 29.9% and 18.4%, respectively. Few of the samples were low sulphur coals whereas others were medium sulphur coals. The dominant minerals detected by the XRD are quartz and kaolinite with lesser pyrite. The sum concentration of REEs ranged from 23.15 to 173.50 ppm, with an average of 101.43 ppm. The average REEs concentration for the Gus Seam was 79.47 ppm, 120.79 ppm for the Alfred seam, and 137.63 ppm for the Fritz seam. The samples had REEs concentrations higher than that of Worlds and USA Coals except for samples CMB-L1, CB2-L1, CB1-L2, CB2-L2, and CB2-S1. Furthermore, samples CB1-L1, CMB-D, JCBH08B, and JCBH20 had REEs concentrations higher than that of Chinese Coals. The Pearsons’ correlation indicated a mixed inorganic-organic affinity of REEs as shown by the positive correlation. The SEM-EDS analysis in the samples revealed that the REEs have inorganic and organic affinities. The coal-forming environment was weakly reducing to oxidizing, favouring REEs enrichment. The provenance is predominantly a felsic source region, likely a mixture of Archean and post-Archean rocks, including sedimentary sources with granitic, tholeiitic, and alkalic basalt. The Utrecht Coalfield is not promising for REEs extraction. Thesis (M.Sc. (Geology)) -- University of Limpopo, 2025

2025-01-01T00:00:00Z Matukane, Ncedo Matricia http://hdl.handle.net/10386/5398 2026-03-19T01:00:23Z 2025-01-01T00:00:00Z

Mineralogical characterisation of brittleness indices of platinum-bearing reefs (UG 2), located in the eastern limb of the Bushveld Igneous Complex Matukane, Ncedo Matricia The brittleness of rocks has traditionally been measured utilizing mechanical properties, however, it has been established that the mechanical properties of rock masses strongly depend on their petrographic properties, and mineralogical composition plays a critical role in determining the property of rocks to fail. Despite the existence of established brittleness indices based on the mineralogical composition of rocks, the selection of brittle components in rocks remains subjective and can be contradictory. The effects of porosity, stress state, cement type and strength, pre-consolidation factor, grain size, and external mechanical conditions are also not considered in the existing brittleness indices. This study aims to characterize the brittleness indices of platinum-bearing (UG2) reefs on the eastern limb of the Bushveld Igneous Complex using mineralogical analysis. To this aim, microscopic examinations identified different mineralogical characteristics, laboratory analysis of UG2 samples was performed to obtain the mechanical parameters, and additional parameters were obtained from numerical simulations. Innovative brittleness indexes (B1, B2, B3, B4, and B5) are developed utilizing parameters such as textural variables, contact type, contact nature, and packing density. The brittleness indexes are additionally compared with previous important brittleness indices utilizing fieldwork, laboratory analysis, numerical simulation, and predictions (multivariate linear models). Additionally, a similar approach was applied to the mechanical parameters, developing innovative brittleness indexes B1, B2, B4 and B6 using traditional mechanical parameters. The results revealed that contact type and contact nature were the most significant mineralogical predictors of brittleness, with models B2 and B6 demonstrating strong predictive accuracy (R² values of 0.778 and 0.727, respectively) and near-perfect precision (SE = 0.000). Texture and packing variables had a lesser impact on brittleness prediction. While tensile (σt) and compressive strength (σc) emerged as key predictors with high accuracy. Models B2 and B6 were the most reliable, showing near-perfect precision with SE values of 0.000. In contrast, models B1 and B4 were less precise, and B3 lacked statistical significance. The high statistical significance and low SE values of B2 and B6 confirmed their reliability for brittleness prediction. It is recommended that more sophisticated methods be applied as well. Thesis (M.Sc. (Geology)) -- University of Limpopo, 2025

2025-01-01T00:00:00Z Morukuladi, Mogahabo Tebogo http://hdl.handle.net/10386/5204 2025-12-09T01:00:12Z 2025-01-01T00:00:00Z

Computational and experimental studies of transition metal carbonate precursors as cathodes for lithium-ion batteries Morukuladi, Mogahabo Tebogo This study investigates the layered oxide cathode with NMC-type LiNixMnyCozO2 as the alternative cathode material for lithium ion batteries. This material has attracted the researcher’s interest as alternative cathode material due to its low cost and less toxicity as compared to the most widely commercialised lithium cobalt oxide (LCO). Lithium nickel manganese cobalt oxide (often abbreviated as NMC) is a type of cathode material used in lithium-ion batteries. It's a popular choice because it offers a balance of high energy density, good cycling stability and relatively low cost compared to other cathode materials. In this study we investigate the stability properties of Ni0.3Mn0.5Co0.2CO3 and Ni0.3Mn0.5Co0.2O2, respectively. In particular, we focus on the manganese rich compositions and minor amounts of nickel and cobalt. We further doped both system (Ni0.3Mn0.5Co0.2CO3 and Ni0.3Mn0.5Co0.2O2) with fluorine, titanium, niobium and chromium to check if their contributions could improve or disprove the behaviour of Ni0.3Mn0.5Co0.2CO3 and Ni0.3Mn0.5Co0.2O2 materials. Firstly, the structural, electronic, mechanical and vibrational properties of Ni0.3Mn0.5Co0.2CO3, Ni0.3Mn0.5Co0.2O2 and their doped systems have been calculated using the density functional theory employing the pseudo-potential plane-wave approach within the local gradient approximation with the Hubbard parameter U for strongly correlated transition metals. The structural property calculations included the equilibrium lattice parameters, density and energy of formations while electronic properties included the partial density of states (PDOS), total density of states (TDOS) and band structures for all the systems. Furthermore, mechanical properties investigated the elastic constants, Pugh ratio and anisotropy while vibrational properties investigates the phonon dispersion curves for Ni0.3Mn0.5Co0.2CO3, Ni0.3Mn0.5Co0.2O2 and their doped systems. The calculated lattice parameters and energy of formation could be used for benchmarking in the future since no similar work was found in literature for comparison. Moreover, the calculated energy of formations revealed the relatively low and negative values for all the systems, suggesting thermodynamic stability. With the band structures, we found that Ni0.3Mn0.5Co0.2CO3 and Ni0.3Mn0.5Co0.2O2 structures were semiconductors with a direct gap of 0.004 eV and 0.036 eV with their doped systems also indicating metallic characteristics. Moreover, the partial density of states for our materials and their doped systems were also found to be metallic as there was no energy band gap observed at the Fermi line. Furthermore, the elastic constants revealed that all our systems recorded 21 independent elastic constants which falls within the triclinic lattice systems. For a material to be considered mechanically stable within the triclinic system, there are conditions to be satisfied, hence Ni0.3Mn0.5Co0.2CO3 satisfied all the conditions suggesting mechanical stability while Ni0.3Mn0.5Co0.2O2 did not satisfy all the conditions implying mechanical instability. The phonon dispersion curves revealed that Ni0.3Mn0.5Co0.2CO3 was vibrationally stable while Ni0.3Mn0.5Co0.2O2 was vibrationally unstable due to the presence of negative vibrations along the Brillouin zone. Furthermore, the phonon dispersion curves for doped systems revealed that some are vibrationally stable while some are vibrationally unstable. Secondly, since the study focuses on manganese rich systems, cluster expansion technique was used to generate phases in the manganese rich side. From the results, various phases with varied concentrations and symmetries were produced by the ground-state phase diagram. The accuracy of new structures during cluster expansion fitting is indicated by the cross validation score (CVs) for all of the generated new structures being less than 5meV per active atom position. Since all of the developed structures have CVs below 5meV, this indicate that our calculations were valid and the newly generated structures will work realistically. From the phase diagram, we noticed that all the predicted phases are in the negative energy of formations side (miscible constituent) which indicate thermodynamic stability. Moreover, of all the phases generated within the diagram, only phases in the manganese rich side were explored by using first principles calculations to further confirm their stability properties by determining their structural, electronic, mechanical and vibrational properties. The energy of formation results revealed that all the phases are thermodynamically stable while electronic properties revealed metallic characteristic for all the phases in the Mn-rich side. For mechanical properties, we found that few phases did not satisfy the triclinic conditions which implies mechanical instability while other phases were found to satisfy the conditions, indicating mechanical stability. Lastly, the carbonate co-precipitation method was used in this study to synthesize the transition metal carbonate precursors using a 4L stirred tank reactor (CSTR) under steady state circumstances. We produced Ni0.28Mn0.53Co0.19CO3 and Ni0.17Mn0.67Co0.17CO3 which was later lithiated to form LiNi0.33Mn0.53Co0.14O2 and LiNi0.17Mn0.67Co0.17O2 as our layered cathodes. Both the lithiated samples were further characterized for thermogravimetric analysis, x-ray diffractions, morphologies, EDX and XRF. Thermogravimetric analysis revealed thermodynamic stability for both samples while XRD’s also managed to produce the most crystalline peak at 003 indexing. The scanning electron microscopy was also tested to determine the particle size and distribution for both samples and the results revealed a homogeneous particle distribution in each sample. We further collaborated with University of Kent for the usage of the synchrotron beam of the Diamond light source to determine the effect of fluorination on our NMC samples. In particular, we wanted to check if fluorination reduces or increases the oxidation states of metals within our samples and results revealed that fluorination does not change the oxidation state of our samples. Thesis (Ph.D. (Physics)) -- University of Limpopo, 2025

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