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Multi-scale modelling of oxide-based solid state battery
Get PDFThesis (M.Sc. (Physics)) -- University of Limpopo, 2023The oxide garnet Li7La3Zr2O12 (LLZO) exhibits high Li-ion conductivity and chemical stability
when in contact with lithium metal anodes, making it a promising solid electrolyte for Li-based
batteries. The tetragonal phase, however, is poorly Li-ion conductive at room temperature. It
is essential for Tetragonal Li7La3Zr2O12 (t-LLZO) to be capable of enduring high temperatures
with good phase stability in order to be used in practical devices. In this way, adding
supervalent cations, such as Ta, to the Zr-site of t-LLZO stabilizes the low-temperature
structure of the tetragonal crystals, and more importantly, creates vacancies in the tetragonal
phase, thereby enhancing its ionic conductivity. However, the crystal structure behaviour at
high temperatures remains unclear. Moreover, the fundamental aspect of supervalent
substitution as well as which level of lattice expansion/contraction promotes ionic diffusion of
this supervalent substitution remains poorly understood.
The density functional theory calculations implemented in the Vienna ab initio simulation
package were utilized to offer a better understanding of the stabilization of the tetragonal
Li7La3Zr2O12 phase by determining the structural, mechanical, and electronic properties of the
high-conductive LLZO structure. It was found that the structural properties calculated are in
good agreement which is within a 2% error of the experimentally measured results from other
studies. The t-LLZO structure has a negative energy of formation, which is consistent with
experimental data. The calculated Young’s modulus is in good agreement with the experimental
observations, and it satisfies the necessary stability constraints for the configuration. Owing to its
large band gap for electrochemical stability, the calculated band structure of t-LLZO shows
that the material is a magnetic separator with a wide and indirect band gap along the gsymmetry point, which is in good agreement with the experimental observations from other
studies.
In this study, first-principle calculations combined with cluster expansion simulation were
performed on the t-LLZO to attain a fundamental understanding on the phase stability of Tadoped LLZO and generate new possible phases of Ta-doped LLZO. Furthermore, Monte Carlo
simulation was utilised to gain an insight into the behaviour of the Ta-doped phase as a function
of temperature under canonical ensemble. The cluster expansion generated 28 new multicomponent Ta-doped Li5La3Zr2-xTaxO12 structures, were all of the new structures are
thermodynamically stable with a negative enthalpy of formation. The Monte-Carlo temperature
profiles have a miscible gap with very small energy difference, indicating that there is no phase
separation and the system mixes well at ~900K. Further density functional theory calculations
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were performed on the most stable generated Ta-doped LLZO structures to determine the structural, mechanical, and electronic properties of the structures for their application as active
solid-state electrolytes. It is found that the generated structures exhibit good structural stability
since the calculated lattice parameters of the Ta-doped LLZO structures are found to be smaller
than that of pure t-LLZO. The results show that the distance between Li-Li in doped Ta-LLZO
is smaller than in pure t-LLZO, which indicates that the smaller the difference between the
dopant ionic radius and the critical dopant radius, the higher the conductivity. Therefore, the
structural properties of Tantalum-doped structures are shown to improve due to the smooth
decrease in calculated lattice parameters. Moreover, the Ta-doped structures show good elastic
stability against deformation and exhibit magnetic separator behavior, which encourages their
use as the next-generation solid electrolytes. Therefore, the findings provide a better
understanding of the phase stability of the generated Ta-doped LLZO structures, which set a
strong foundation for further analysis of the temperature effect on the rate of lithium-ion
diffusion and the mobility of the lanthanum, zirconium, tantalum, and oxygen ions in the
system at high temperatures, which is crucial for the development of these promising solidstate electrolytes for all-solid-state Li-ion batteries
South African border security management : a case of international migration
Get PDFThesis (Ph.D. (Public Administration)) -- University of Limpopo, 2023The purpose of this study was to investigate the efficacy of South African border security management in terms of the effects of international migration in the country. Triangulation descriptive research was used in this study to determine the efficacy of South African border management. Structured questionnaires and an unstructured interview guide were used to collect data. In both provinces, Limpopo and Mpumalanga, four (4) focus group discussions were held. There were two blinded focus group discussions with community members and two with illegal immigrants. Officials from border security agencies were among those who have participated in this study. A total of (n110) immigrants were surveyed in both provinces, with 110 responding to qualitative interviews, for a total of 215 participants in this study.
SPSS, ATLAS.ti, and themes were used to analyse raw data. The study looked into a variety of factors, including push and pull factors, corruption, and border management. The study's findings reveal a variety of factors that contribute to illegal human mobility. Thousands of immigrants cross the borders illegally into South Africa from various African countries. Some of them, however, are refugees, while others are economic migrants. According to the Refugee Act, all asylum seekers must apply for asylum within five days of their arrival in order to avoid being repatriated and found to be in the country illegally. As a result, the immigrants fail to visit the refugee reception office to register and apply for asylum, and they remain in the country illegally. Some of them simply come to South Africa to look for opportunities.
Corruption and bribery are contributing factors to South Africa's lack of effective border management; officials take bribes from immigrants, compromising South African security because some of those who cross the border to this country are criminals; some are the most wanted criminals in their home country
Design and synthesis of quinoline-triazole schiff base metal complexes as potential anti-cancer agents
Get PDFThesis (M. Sc. (Chemistry)) -- University of Limpopo, 2023The aim of the project was to synthesize quinoline-1,2,3-triazole Schiff base hybrids as promising anti-cancer agents. A laboratory prepared 2-Amino-3,5dibromoactophenone was subjected to Claisen-Schmidt aldol-condensation with benzaldehyde derivatives to form 2-aminochalones. The step was followed by an acid mediated-cyclization reaction to form 2-substituted 2,3-dihydro-quinolin-4(1H)ones, which in turn underwent dehydrogenation and oxidative aromatization to afford 2-substituted quinolin-4(1H)-ones derivatives. The nucleophilic substitution of the latter with sodium azide yielded the 2-substituted 4-azidoquinolines, which underwent Huisgen cycloaddition reaction to form the 4-triazolo-quinoline derivatives in high yields and further confirmed using X-ray diffraction analysis. The 4-triazolo quinoline derivatives formed from propargyl alcohol, served as precursors for oxidation reaction to afford carbaldehyde triazolyl-quinoline derivatives, which in turn were reacted with 2-picolylamine to produce a quinoline-triazolyl Schiff base ligand derivatives in low yields through condensation reaction. The 3-fluoro-phenyl triazole derivatives were subjected to metal coordination with Ruthenium (II) p-cymene bischloride to form ruthenium arene coordinated complexes, showing a CIS in the range of ẟ (-0.003-0.047) ppm for 1H NMR and ẟ (-0.058-0.010 ppm) for 13C NMR. All the synthesised compounds were confirmed using a combination of 1H-NMR, 13C-NMR, FT-IR, and mass spectrometry. The triazolyl quinoline derivative compounds were tested against MDA-MB-231 cell line (breast cancer) here (6,8-dibromo-4-(4-(3fluorophenyl)1H-1,2,3-triazol-1-yl)-2-(4-methoxyphenyl) quinoline 153 h showed a good cytotoxicity effect compared to other compounds with an IC50 of 40.7 µM. The quinoline triazolyl compound molecular docking revealed that(6,8-dibromo-4-(4-(3fluorophenyl)1H-1,2,3-triazol-1-yl)-2-(4-methylphenyl) quinoline 153 g displays good binding energy of -10.9 k calmol and an inhibitory concentration of 0.80 µM against VEGFR-2 tyrosine kinase referenced to Sorafenib (standard)
The influence of learners' textbooks on Sepedi writing skills in a grade 7 classroom : a case of primary schools in Lebowakgomo Circuit
Get PDFThesis (M.Ed. (Language Education)) -- University of Limpopo, 2023The aim of the study was to investigate the influence of learners’ textbooks on
Sepedi essay writing skills. Grade 7 learners at primary schools in Lebowakgomo
Circuit are faced with challenges of language proficiency due to unnecessary usage
of loaned words, orthographic and morphological errors in their written essays. This
study adopted qualitative approach and followed a case study design and an
interpritivist paradigm. Qualitative data was collected through semi-structured
interviews and document analysis of the learners’ textbooks and written essays.
Data collected was analysed following the inductive method of thematic data
analysis. The research highlighted that learners use Sepedi textbooks that contain
spelling errors, infusion of languages like English, Afrikaans and isiZulu that
negatively affect learners’ writing skills. It was evident that the errors in learners’
essays emanated from the textbooks given from the schools. It is recommended that
Sepedi Home Language textbooks be thoroughly proofread before being supplied to
schools. The Department of Basic Education should ensure that authors of textbooks
show a good conduct of the language because home language carries the pride,
culture, heritage and identity of the learners they are prescribed fo
Exploring the reading and writing proficiency challenges of English language intermediate phase learners in selected public school in the Gauteng Province
Get PDFThesis (M.A. (English Studies)) -- University of Limpopo, 2023The South African Language in Education Policy (LiEP) states that, in the Intermediate Phase (IP), English First Additional Language (EFAL) should be the preferred Language of Learning and Teaching (LoLT). The purpose of this qualitative study was to better understand the challenges that IP EFAL learners face, as well as teachers' perceptions of EFAL reading and writing in IP. To fit the purpose of the study, purposive sampling was adopted on the basis of EFAL learning in the selected schools, which included nine IP EFAL teachers and ten written activities from learners' workbooks. Interviews and document analysis were used to collect data.
The study found that introducing English LoLT in the IP hinders profound EFAL acquisition and learning, as well as learners' reading and writing proficiencies. Poor EFAL reading and writing skills among school learners have emerged as a major concern, overshadowing the good intentions of the learning outcomes initiated by the LiEP and the Constitution of the Republic of South Africa.
The key findings presented, and suggestions put forward can inform policy decision making and best practices that underlie writing proficiency challenges of English language among IP learners in public schools and mostly second language classrooms. It will further contribute to the growing body of knowledge concerning the various impacts of EFAL learning in South African schools
Assessment of bush encroachment and its potential drivers in selected locations of the Limpopo Province, between 2001 and 2018 time periods
Get PDFThesis (M. Sc. (Geography)) -- University of Limpopo, 2023The only ecosystem that is best suited to accommodate livestock in Africa is the
Savanna ecosystem. The livestock can be raised well in the savanna ecosystem due
to the availability of enough grass and trees. However, there has been an expansion
in indigenous woody plant species cover, density, and biomass in the savanna
ecosystem. Therefore, with an increase in woody cover, also known as bush
encroachment; which is globally, threatening grazing resource availability in the
Savanna. The study aim was to assess bush encroachment and its potential drivers
in selected locations of the Limpopo province, between 2001 and 2018 time periods.
The objectives of this study are to highlight areas of bush encroachment using
existing remote sensing derived tree cover product over a period between 2001 and
2018 in the Limpopo province; and to determine environmental and socio-economic
factors that influence bush encroachment in the Limpopo province. The tree cover
change dataset was acquired from the Council of Scientific and Industrial Research
(CSIR), and was used to asses bush encroachment. The logistic regression was
used to determine which environmental and socio-economic variables influence bush
encroachment. When implementing logistic regression to understand drivers of bush
encroachment, three scenarios were decided, i) environmental variables only, ii)
socioeconomic variables only and iii) environmental and socio-economic data
combined. The results of the study show that there has been an increase of bush
encroachment over the past years in the Limpopo province. Environmental variables
such as temperature minimum, temperature mean and bulk density were found to
significantly influence bush encroachment. Similarly, socio-economic variables such
as population density and annual income distributions such as household income
with no income; income above poverty line; income below average income; average
income; and middle average income were found to be significant. Therefore, the
study used the applications of remote sensing to assess bush encroachment in the
Limpopo province.Council for Scientific and Industrial Research (CSIR) and
National Research Foundation (NRF
Highly adsorptive removal of palladium and platinum ions from wastewater using novel ethylenediamine-glutaraldehyde-grafted metal organic framework
Get PDFJournal article published in the journal Environmental Nanotechnology, Monitoring & Management 20 (2023) 100805Herein, a metal–organic framework (MIL-101(Cr)) was synthesized and functionalized with ethylenediamineglutaraldehyde
(ED-GA for removal of palladium (Pd2+) and platinum (Pt4+) from wastewater. The chemical
structure, surface properties, morphology, and adsorption energy of the prepared materials, MIL-101(Cr) and
MIL-101(Cr)/ED-GA were analyzed using several analytical techniques and density functional theory (DFT). The
prepared MIL-101(Cr)/ED-GA was efficient in removing Pd2+ and Pt4+ from aqueous solution with the percentage
removal reaching 95% for Pd2+ and 85% for Pt4+. Furthermore, the adsorption data demonstrated a
good fit to the Langmuir isotherm model and gave the maximum adsorption capacity values of 416.17 mg g 1 for
Pt4+ and and 322.6 mg g 1 for Pd2+ ions. Kinetics data obeyed a pseudo-second-order model and revealed the
rapid adsorption of Pd2+ and Pt4+ ions by MIL-101(Cr)/ED-GA which reached equilibrium within 10 and 40 min,
respectively. Lastly, DFT studies revealed that the adsorption of Pd2+ ions by the composite forms a more
thermodynamically stable compound than adsorption of Pt4+, suggesting that the material easily interacts with
Pd and high selectivity is thus expected. This was indeed confirmed by experimental selectivity test results.
Owing to their high affinity for PGMs, N atoms depicted large adsorption energy values compared to other
adsorption sites. The MIL-101(Cr)/ED-GA could act as an efficient and cost effective adsorbent for removal of
platinum group metals from wastewater
The variability of soil carbon and other selected soil properties as indicators of sustainable land management under tomato production at Mooketsi ZZ2 farm in Limpopo, South Africa
Get PDFThesis (M.Sc. (Soil Science)) -- University of Limpopo, 2023The soil is the most important component in sustainable land management that varies
spatially due to the combined effect of biological, physical, and chemical processes
that occur over time. Although there has been extensive research on some of the soil
characteristics and their effects on different crop yields, the interactive effect of various
management practices and soil properties on carbon as well as the main factor or
factors controlling soil C under short-term continuous tomato production are not yet
fully understood. The objectives of the study were (i) to determine the spatial variation
of soil carbon (C) and other selected soil properties within the tomato production field
and (ii) to investigate the inter-relationship between soil C and the selected soil
properties within the tomato production field at Mooketsi ZZ2 Farm. To achieve these
objectives, a detailed soil survey was conducted, whereby a systematic soil sampling
strategy was carried out where one sample was collected every 40 m using an auger
at depth of 0-15 cm on a 23-hectare farm. The total number of samples collected were
132. A handheld Global Positioning System (GPS) was used to record the
geographical coordinates, the latitude, and the longitude of where each sample was
taken, this was used to create spatial variability maps. A handheld cone penetrometer
was used to determine the penetrative resistance of the soil before soil samples were
collected. The collected soil samples were analysed for physical and chemical soil
properties such as particle size distribution, aggregate stability, soil organic carbon
(SOC), soil pH, electrical conductivity (EC), and soil extractable phosphorus. The soil
colour was also determined for the collected soil samples. The coefficient of variation
(CV) showed that high variation exists in SOC with a CV of 38.72%, clay content with
CV of 43.48%, silt content with CV of 50.70% and EC with CV of 59.60%.
Semivariograms which are important for spatial analysis showed variation of soil
properties within Mooketsi ZZ2 farm. Spatial dependency, which is the nugget/sill ratio,
showed that extractable P had a weak spatial dependence with 1.00 nugget/sill ratio.
Soil pH (KCl), EC, MWD, clay, silt and sand had moderate spatial dependence with
the following nugget/sill ratios: 0.60; 0.44; 0.38; 0.48; 0.41 and 0.41 respectively. The
SOC and PR both had 0 nugget/sill ratio which is a strong spatial dependence. The
correlation results showed that SOC had weak correlation with the silt, sand and clay
content having correlation coefficients of 0.30, -0.27 and 0.2, respectively. This means
that texture does not influence the spatial variation of SOC across the tomato field. Mean weight diameter (MWD) was positively correlated with sand (r= 0.50) and
negatively correlated with silt content (r = -0.46) and clay content (r= -0.51) showing
that there was weak aggregation in the Glenrosa soil. The electrical conductivity had
relatively weaker positive correlation with both clay content (r= 0.33) and silt content
(r= 0.29) and it was negatively correlated with sand content (r= -0.32). The positive
relationship between clay content and silt content with EC might be because; finer
particles have more negatively charged sites that can hold onto the cations. The
negative relationship between EC and sand content might be because; sandy soils
tend to have low organic matter levels, which is important in binding soil particles. The
low correlations between soil properties might be because, the Glenrosa soil has low
clay content which means less surface area to hold cations and soil particles is
available. This leads to poor soil structure and poor nutrient holding capacity of the
soil. Overall, the results revealed that there was wide spatial variation within the soil
properties of the study area. The RMSE values showed that kriging is reliable to
characterize pH, MWD, SOC, P, PR, clay, silt, and sand with moderate to good
accuracy, but it is less reliable when it comes to EC. From the inter-relationship results,
it can be concluded that there is no soil property that has strong influence on SOC for
the case considered. This indicates that none of these properties could serve as a
proxy for predicting soil C or as parameters that can assist in soil C management
options. The observed spatial variation could have an implication in the optimization
of tomato yield in the study area. This bids for the adoption of site-specific soil nutrient
management in the area in order to optimize tomato production because over and
under fertilisation would be costly for the farm
Experiences of mothers of children with severe intellectual disability regarding partner support in the Capricorn District, Limpopo Province
Get PDFThesis (M.A. (Nursing) -- University of Limpopo, 2023Background: Raising a child with a severe intellectual disability is a challenge for most mothers, as most mothers experience a lack of support from their partners. This lack of partner support causes high stress and marital problems for mothers.
Purpose: The purpose of the study was to determine the experiences of mothers of children with a severe intellectual disability regarding partner support in the Capricorn District, Limpopo Province.
Study method: A qualitative, explorative, and descriptive design was applied to explore and describe the experiences of mothers of children with a severe intellectual disability regarding partner support. Participants were selected using a purposive sampling method. Data were collected from twelve mothers of children with severe intellectual disability using a semi-structured interview guide. Data were analysed using Tesch’s approach to data analysis. Trustworthiness was ensured by using four criteria of trustworthiness, credibility, dependability, confirmability, and transferability. Ethical clearance was obtained from the Turfloop Research Ethics Committee (TREC) and permission to collect data was granted by the Department of Education Limpopo Province and the principals of the selected special schools. The details of the study were explained to the participants who then agreed to participate in the study by signing a consent form.
Results: The findings of the study showed that mothers experienced negative and positive partner support. The positive supports include caring about and loving the child, having a positive relationship with the child, and having instrumental support through sharing supervision and caring. The most negative support was partners not accepting the child, partners lacking emotional support and marital relationship challenges.
Limitation: Data was collected during the COVID-19 lockdown, which delayed getting permission to collect data as the schools were closed for a long time.
Conclusion: The healthcare practitioners as the first people to identify the disability, should immediately inform the mothers and their partners about the child’s disability and start with counselling immediately and continue with counselling throughout the
development. The recommendation of the study focused on the promotion of partner support through research, education and trainin
Investigation of language use in academic writing of grade 10 learners in English First Additional Language (EFAL) classroom
Get PDFThesis (M. A. (Language Education)) -- University of Limpopo, 2023This study investigated the challenges experienced by Grade 10 learners in the usage of English as the first additional language in classroom academic writing. Qualitative methodology was used to conduct this study where responses from a sample of 10 learners and 2 EFAL teachers were obtained. The participants were purposefully sampled from a secondary school in Tweefontein. The researcher collected data using the semi-structured interviews and document analysis. Selected teachers were interviewed and learners were given an essay writing task. The data was analysed using the inductive thematic data analysis method. The study‟s findings point to social media as the major factor that contributes to the learners‟ usage of social language in academic essay writing. Contraction was found to be the most common language issue in the learners‟ academic writing. The study recommends that stakeholders such as the Department of Education, teachers, parents and learners should work together in order to improve the learners‟ usage of language in academic writing