DSpace 8

DSpace is the world leading open source repository platform that enables organisations to:

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Now showing 1 - 5 of 9

Recent Submissions

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Recent developments strategies in high entropy modified lithium-rich layered oxides cathode for lithium-ion batteries
(ECS Meeting Abstracts, Volume MA2025-01,, 2025) Ajayi, Samuel O.; Ehi-Eromosele, Cyril; Liu, Xinying; Mathe, Mahlanyane Kenneth
LiNi0.5Mn0.2Co0.2O2 (NMC532) is a widely used cathode material in commercial lithium-ion batteries; however, it suffers from capacity degradation and poor rate performance. In this study, sol-gel combustion synthesis (SCS) with a controlled fuel-to-oxidizer ratio (fuel stoichiometric (FS) and fuel-rich (FR) compositions, the fuel-lean (FL)) respectively, was employed to improve the structural and electrochemical performance of the NMC532 cathode. The fuel-to-oxidizer ratio was found to significantly impact the exothermicity of the combustion reaction, which subsequently influenced the morphology, crystal structure, and electrochemical performance of the synthesized NMC532 material. The FL composition produced a well-defined layered structure, the largest crystallite size, and the lowest degree of cation mixing compared to the FS and FR compositions. The FL cell exhibited an initial discharge capacity of 180 mAh/g and the highest capacity retention of 92.2% when cycled at 0.1 C within a voltage range of 2.5–4.4 V. Additionally, it demonstrated superior rate capability, delivering capacities of 180, 178, 175, and 173 mAh/g at current densities of 1 C, 3 C, 5 C, and 10 C, respectively, within a voltage range of 3.0–4.6 V. The electrochemical impedance spectroscopy (EIS) measurements confirmed that the FL cell had the lowest polarization and impedance. The superior electrochemical performance of the FL cathode was ascribed to its improved structural properties.
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Recent developments strategies in high entropy modified lithium-rich layered oxides cathode for lithium-ion batteries
(Inorganic Chemistry Communications, 2025-02) Ajayi, Samuel O.; Dolla, Tarekegn H.; Bello, Ismaila T; Liu, Xinying; Makgwane, Peter R.; Mathe, Mkhulu K.; Ehi-Eromosele, Cyril O.
Lithium-rich layered oxides (LRLOs) are of intense interest and are regarded as one of the best cathodes for next-generation Lithium-Ion batteries (LIBs). LRLOs are favored due to the low cost of production, high energy densities, voltage, and specific capacity. LRLOs suffer from irreversible capacity loss, poor rate capability, voltage, and capacity fade, which in turn limit their full practical applications and commercialization. Therefore, strategies such as surface coating, surface treatment, composition optimization, and elemental doping have been explored to enhance the structural and electrochemical performance of LRLO. Nevertheless, high entropy (multiple elements) doping has proven to be a very effective strategy due to its simplicity and expansion of LRLO lattice interplanar spacing without damaging their original structure. It is worth noting that there has been little research work on high entropy strategies for modifying LRLO cathode. Thus, the aim of this review is current update on high entropy strategies for modifying LRLO cathode materials.
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Environmental assessment of radionuclide exposure in packaged borehole water exploited from crystalline rocks in Ogbomoso
(ICSAEES-2024, Lagos, Nigeria, 2024) Oladipo, A. E.; Aremu, A. A.; Adeniji, A. A.; Ayinla, T. O.; Babarimisa, I. O.; Morakinyo, R. O.; Araka, I. O.; James, U. E.
The amounts of naturally occurring radionuclides (40K, 238U and 232Th) in packaged borehole water manufacture have been investigated in this work. Furthermore, the buildup of radioactive materials in drinking water presents a direct path for human population exposure to internal radiation. The amount of radioactivity in the processed and unprocessed water samples was measured using gamma spectrometry and a computer-resident quantum multichannel analyser (MCA 2100R) connected to a well-calibrated and shielded NaI (Tl) detector. From the results, it was revealed that the values of activity concentration of processed water ranges between 50.46 ± 3.14 Bq/L to 102.18 ± 14.07 Bq/L, 7.92 ± 4.46 to 16.71 Bq/L, and 10.00 ± 0.84 Bq/L to 14.87 ± 4.03 Bq/L for 40K, 238U and 232Th, respectively. Also, the results obtained for the activity concentration of unprocessed water ranges between 74.51 ± 3.51 Bq/L to 102.21 ± 7.23 Bq/L, 14.86 ± 1.91 Bq/L to 19.87 ± 3.10 Bq/L and 10.00 ± 3.36 Bq/L to 17.79 ± 4.43 Bq/L for 40K, 238U and 232Th, respectively. The results confirmed the presence of40K as a principal occurring radionuclide in the water samples. The annual effective dose for processed water ranges from 0.012 to 0.017 mSyr-1, while it ranges between 0.015 and 0.020 mSyr-1 for unprocessed water. Results in the present study fall below 0.1 mSyr-1, which is the acceptable limit recommended by International Commission on Radiological Protection standard value.
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Effects of Aerosol Scattering Attenuation on Free-Space Optical Link Performance in Owerri, Southeast, Nigeria
(Science and Technology: Developments and Applications Vol. 8,, 2025) Akinwumi, A.; Ayo-Akanbi, O.; Omotosho, T. V; Arijaje, T; Ometan, T.; Adewusi, O.
High-speed, point-to-point data transmission through laser beams across terrestrial networks is sometimes referred to as "Free-Space Optics" (FSO). Multimedia applications including social networks, OTT platforms, video conferencing, and multimedia streaming are driving up the demand for data rates and channel bandwidth, which has led to a telecommunications bottleneck. In spite of the several benefits of using free-space optical (FSO) communication systems as complementary platforms for next-generation networks, the existence of atmospheric disturbances such as fog and scintillations are key sources of signal impairment that affect system performance. Thus, it is crucial to learn about the specific weather patterns of the areas where FSO lines will be installed. The purpose of this work is to estimate the availability performance of FSO lines broadcasting at both 850 nm and 1550 nm by performing a statistical analysis of meteorological visibility data gathered for Owerri in Nigeria over a 21-year period (2000-2021). The results show that the visibility during the most common fog events in Owerri is 100 meters. The probabilities of encountering and exceeding the scattering attenuations associated with Owerri's most common fog event are 0.0002 and 0.0229, respectively. This research could be expanded in the future by exploring the effects of varying localized climatic conditions on the many forms of optical signals, such as plane, spherical, and Gaussian beam waves. This would aid in the modelling of different forms of attenuation for deployment sites of FSO or hybrid FSO systems.
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Analysis of Attenuation Due to Atmospheric Gases Prediction Models at Ota, Nigeria
(Science and Technology: Developments and Applications Vol. 7, 2025) Akinwumi, A.; Omotosho, T.; Usikalu, M.; Adewusi, M.; Ometan, O.; Emetere, M.
The theory explaining the interaction between molecules and radiation of gases in telecommunication ascertained the fact that microwave signals experience significant attenuation that can appreciably degrade the quality of signal transmissions. Millimeter and sub-millimeter wave signals experience scattering and absorption while propagating through the atmosphere. The demand for satellite services is rapidly increasing on a daily basis. One of the major concerns for satellite telecommunication designers is the impacts of gas attenuation on earthspace path links, most importantly in tropical areas. This research has been directed at the analysis and comparison of gas attenuation prediction models at Covenant University, Ota, southwest Nigeria (Lat: 6.7 o N, Long: 3.23o E). Gas attenuation data were collected from the spectrum analyzer and Davis automatic weather station for a period of five years (April 2012- December 2016) from Astra 2E/2F/2G Satellite link set at an elevation angle of 59.9o on 12.245 GHz. The monthly gas attenuation was analyzed and compared with existing gas attenuation prediction models that could provide a guide to microwave propagation engineers in the tropical region. The results suggest that even during clear-sky, gas attenuation still poses a threat to the design of satellite communication on the earth-space path. The results also suggest that even during clear-sky, gas attenuation still poses a threat to the design of satellite communication on the earth-space path. Likewise, the same pattern was observed from 2013 to 2016 where Salonen’s model was reported as the lowest model and Liebe’s model gave the highest value. Therefore, the ITU-R model may be more accurate for modelling gas attenuation for the region. Hence, the statistics provided in this work will help engineers in planning and designing good telecommunication systems in the tropical region.