Browsing by Author "Mohammed, L."
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Item A comparative review of the mineralogical and chemical composition of African major bauxite deposits(Heliyon, 2023) Zainudeen, N.M.; Mohammed, L.; Nyamful, A.; Adotey, D.; Osae, S.K.Bauxite, which is the main raw material that aluminium is extracted from was discovered in Africa in the early 1900s. Currently, the production and export capacities of the African Bauxite ore are about a third of the World’s total capacity. However, the processes leading to the final finished product of; surface mining of the ore, refining ore into alumina and finally extracting the pure aluminium metal in high energy consuming smelters that employ the Hall-H´eroult electrolysis process; seldom take place inside Africa. The main goal of this work is to analyse the mineralogical and geochemical characteristics of bauxite deposits from some prominent bauxite producing and exporting countries of Africa in order to fashion out if a trend exist for the type of source rocks. Judging from the data obtained, gibbsite is found to be the main aluminium oxide in all the bauxite deposits with slight occurrence of boehmite in 3 out of the 13 deposits, while goethite is the main oxyhydroxide iron mineral. The compiled results of the various investigations highlighted the fact that the deposits are of diverse qualities with respect to world standard of major element content of bauxite; with average percentage concentration in the ranges as: Al2O3 (43.73–61.25), Fe2O3 (1.55–34.25), SiO2 (0.42–10.84); except two of the deposits with alumina content less than 40%. With evaluated silica moduli less than 8 for only two (2) of the deposits (4.76 and 6.94), the rest have higher moduli that ranges between (14.49 and 75.45). The higher percentage of iron oxide content (>20) in six (6) out of the 13 ore deposits, allowed the deposits to be grouped into three (3) categories of grades; high alumina ore, ferruginous ore, siliceous ore and combination of each. Source rock of the deposits were determined through geochemical and petrographic considerations of laterisation products of the rocks through evaluation of the weathering indices of; Chemical Index of Alteration which was in the range (97.16–99.98) while the Ruxton ratio ranged between (0.0133–0.2100); signifying the parent rock underwent intensive weathering process. This is indicative of the source rocks of the Bauxite deposits being either (i) anorthositic, (ii) argillite and dolerite, (iii) granulite and feldspathic gneiss, and/or, (iv) mafic-basaltic andesite igneous. Awareness of new and yet-to-commence emerging bauxite producing African countries was created, by highlighting the economic impact those respective countries will experience when that mining sector is developed for the aluminum in dustry at home and world at large.Item Effect of Morphologically Different Conductive Agents on the Performance of Silicon Anode in Lithium‐Ion Batteries(ChemistrySelect, 2018-10) Madzvamuse, A.; Hamenu, L.; Mohammed, L.; Ko, J.M.The performance of electrochemical electrodes, is largely dependent on the extent of efficient electrical contacts between particles, and secondly, between the current collector and the particles, amongst other factors. We report on the electrical conductivity of silicon anode electrodes that have been prepared by using conductive agents with different morphological properties. Super P® Li (SP), VGCF®‐H vapor grown carbon fibers (VGCF), and their mixture were incorporated separately into the anode electrode to observe their distinctive resultant performance. The morphological characterization was done using scanning electron microscopy whilst the electrochemical properties of the prepared electrodes were characterized by electrical resistivity test, cyclic voltammetry, charge/discharge tests and electrochemical impedance spectroscopy. The combination of VGCF®‐H and Super P® Li, results in improved performance of the anode, due to their synergistic interactions which reduce the effects encountered during the failure of the silicon anode electrode caused by large volume changes. These findings unlock new opportunities for the exploration and development of other morphologically useful conductive agents to improve silicon anode in lithium ion batteries.Item LiNi1/3Mn1/3Co1/3O2/graphite cells adopting polyolefin and non-polyolefin separators for potential application in industrial manufacturing of energy storage devices(Electrochemistry Communications, 2024) Hamenu, L.; Mohammed, L.; Abdul-Samii, R.; et al.This study features comprehensive physical and electrochemical properties of different polyolefin and non polyolefin separators. These separators include polypropylene-polyethylene-polypropylene (PEP), polyethylene (PE), Al2O3-coated polypropylene (C-PP), polyethylene terephthalate (PET), and Silicon carbide mat (SiCmat). The interaction of the different separators and the electrolyte was investigated in terms of ionic conductivity, contact angle test, electrolyte uptake, and electrolyte oxidation. The full cells fabricated using the different separators were also studied for charge–discharge performance, cycle performance, and internal resistance. Results showed that the different separators demonstrated different physical and electrochemical behavior. The non-polyolefin separators registered a small electrolyte contact angle due to their high porosity and structural compatibility with the electrolyte. At 10 C-Rate, the specific capacity is in the order of PET > SiCmat > C-PP > PE > PEP corresponding to 90 mAh/g, 85 mAh/g, 70 mAh/g, 60 mAh/g and 40 mAh/g respectively. After 100 cycles at 1.0 C-rate, the cycle performance is in the order of PE > PET > C-PP > SiCmat > PEP corresponding to 70 %, 65 %, 61 %, 51 % and 49 % respectively. Thermally, PET, C-PP and SiCmat showed better thermal stability compared to the other separators. Therefore, Industrial production that requires high thermal stability may rely on C-PP, PET, or SiCmat, while PET and SiCmat offer better cycle performance and may replace commercially available PE and PEP.