Development of high capacity lithium-manganese-rich cathode materials xLi2MnO3•(1-x)LiMn0.5Ni0.5O2 for lithium ion batteries
- Authors: Rapulenyane, Nomasonto
- Date: 2018
- Subjects: Lithium ion batteries , Electrochemistry Lithium cells
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/34766 , vital:33442
- Description: In this study, a facile synthesis method was developed to produce layered-layered cathode materials with the formula xLi2MnO3•(1-x)LiMO2 (M= Ni and Mn) referred to as lithium-manganese-rich materials for lithium ion batteries. The prepared materials displayed high capacity ≥200 mAh/g at a current density of 20 mA/g in the voltage range of 2.0 V to 4.8 V. In particular the cathode material prepared at pH 10.0 delivered a high initial discharge capacity of 266 mAh/g at 20 mA/g current density and maintained a discharge capacity ≥220 mAh/g at 50 mA/g after 50 cycles. The synthesis method was used to further investigate the effect of lithium ratio in the layered-layered material. Li1+xMn0.6Ni0.2O2, x= 0.2, 0.25, 0.3 and 0.4 cathode materials were produced respectively. The BET surface area analysis results showed that Li1.3Mn0.6Ni0.2O2 material had comparatively higher surface area to the other cathode materials and also delivered good electrochemical results. XPS showed that the cation distribution is affected by the increase in lithium ratio, the Mn4+ percentages decreased significantly with an increase in lithium ratio. All materials peaks deconvoluted into two peaks namely Mn4+ and Mn3+, Li1.3Mn0.6Ni0.2O2 had the highest percentages of the stable Mn4+ 70.8%. Further investigation focused on the effect of the sintering temperature on the structure and the electrochemical performance of Li1+xMn0.6Ni0.2O2, x= 0.25, 0.3 and 0.4 cathode materials. X-ray diffraction showed the same patterns for all cathode materials sintered at 700˚C, 800˚C and 900˚C. Rietveld refined results however, showed that the increase in the sintering temperature, results in a decrease in the Li2MnO3 component percentage in the layered structures. Scanning electron microscopy images further proved that the particle size increases with increasing temperature. The charge–discharge tests of coin cells demonstrated that the materials sintered at 800˚C delivered higher discharge capacities above 200 mAh/g at 20 mA/g current density when compared to the materials made at the lower temperatures. Lastly the cathode material prepared at pH 10.0 was further evaluated in a cell using lithium titanate oxide Li4Ti5O12 as anode material. The cells delivered an initial discharge capacity of 213 mAh/g at 20 mA/g within a voltage range 3.3V-0.5V. The coin cells developed in this work delivered good cycling performance.
- Full Text:
- Date Issued: 2018
- Authors: Rapulenyane, Nomasonto
- Date: 2018
- Subjects: Lithium ion batteries , Electrochemistry Lithium cells
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/34766 , vital:33442
- Description: In this study, a facile synthesis method was developed to produce layered-layered cathode materials with the formula xLi2MnO3•(1-x)LiMO2 (M= Ni and Mn) referred to as lithium-manganese-rich materials for lithium ion batteries. The prepared materials displayed high capacity ≥200 mAh/g at a current density of 20 mA/g in the voltage range of 2.0 V to 4.8 V. In particular the cathode material prepared at pH 10.0 delivered a high initial discharge capacity of 266 mAh/g at 20 mA/g current density and maintained a discharge capacity ≥220 mAh/g at 50 mA/g after 50 cycles. The synthesis method was used to further investigate the effect of lithium ratio in the layered-layered material. Li1+xMn0.6Ni0.2O2, x= 0.2, 0.25, 0.3 and 0.4 cathode materials were produced respectively. The BET surface area analysis results showed that Li1.3Mn0.6Ni0.2O2 material had comparatively higher surface area to the other cathode materials and also delivered good electrochemical results. XPS showed that the cation distribution is affected by the increase in lithium ratio, the Mn4+ percentages decreased significantly with an increase in lithium ratio. All materials peaks deconvoluted into two peaks namely Mn4+ and Mn3+, Li1.3Mn0.6Ni0.2O2 had the highest percentages of the stable Mn4+ 70.8%. Further investigation focused on the effect of the sintering temperature on the structure and the electrochemical performance of Li1+xMn0.6Ni0.2O2, x= 0.25, 0.3 and 0.4 cathode materials. X-ray diffraction showed the same patterns for all cathode materials sintered at 700˚C, 800˚C and 900˚C. Rietveld refined results however, showed that the increase in the sintering temperature, results in a decrease in the Li2MnO3 component percentage in the layered structures. Scanning electron microscopy images further proved that the particle size increases with increasing temperature. The charge–discharge tests of coin cells demonstrated that the materials sintered at 800˚C delivered higher discharge capacities above 200 mAh/g at 20 mA/g current density when compared to the materials made at the lower temperatures. Lastly the cathode material prepared at pH 10.0 was further evaluated in a cell using lithium titanate oxide Li4Ti5O12 as anode material. The cells delivered an initial discharge capacity of 213 mAh/g at 20 mA/g within a voltage range 3.3V-0.5V. The coin cells developed in this work delivered good cycling performance.
- Full Text:
- Date Issued: 2018
Success factors of social enterprises in the education sector
- Authors: Makgato, Noko Leonard
- Date: 2018
- Subjects: Social entrepreneurship -- South Africa , Entrepreneurship -- South Africa Economic development -- Social aspects -- South Africa , Success in business -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/22629 , vital:30034
- Description: Social entrepreneurship is a complex concept with many dimensions that is not well understood in South Africa. The purpose of this research is to contribute to the limited body of knowledge leading to a better understanding of various factors of success that are at play within social enterprises in the education sector in South Africa, including characteristics of the social entrepreneurs at the helm of these ventures. For the purpose of this research, social entrepreneurship is treated as a phenomenon that occurs at the intersection of for-profit, non-profit and non-governmental organisations, without being limited to any single organisational format. Data analysed was obtained through in-depth interviews with persons in the top leadership of FIVE social enterprises, including founders and executives. From this data a composite set of success factors was developed, with the findings presented according to emerging themes and topics. The study reveals a core set of attributes related to environmental, organisational, leadership, financial and stakeholder factors that manifest in successful social enterprises. Research conclusions and recommendations based on this study were made, opportunities for further research were identified and shortcomings of this study were acknowledged.
- Full Text:
- Date Issued: 2018
- Authors: Makgato, Noko Leonard
- Date: 2018
- Subjects: Social entrepreneurship -- South Africa , Entrepreneurship -- South Africa Economic development -- Social aspects -- South Africa , Success in business -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/22629 , vital:30034
- Description: Social entrepreneurship is a complex concept with many dimensions that is not well understood in South Africa. The purpose of this research is to contribute to the limited body of knowledge leading to a better understanding of various factors of success that are at play within social enterprises in the education sector in South Africa, including characteristics of the social entrepreneurs at the helm of these ventures. For the purpose of this research, social entrepreneurship is treated as a phenomenon that occurs at the intersection of for-profit, non-profit and non-governmental organisations, without being limited to any single organisational format. Data analysed was obtained through in-depth interviews with persons in the top leadership of FIVE social enterprises, including founders and executives. From this data a composite set of success factors was developed, with the findings presented according to emerging themes and topics. The study reveals a core set of attributes related to environmental, organisational, leadership, financial and stakeholder factors that manifest in successful social enterprises. Research conclusions and recommendations based on this study were made, opportunities for further research were identified and shortcomings of this study were acknowledged.
- Full Text:
- Date Issued: 2018
Female university students’ perceptions of the effects of maternal loss on their identity and intimacy development
- Authors: Makalima, Phaphama
- Date: 2017
- Subjects: Intimacy (Psychology) Identity (Psychology) , Students -- South Africa -- Psychological aspects Developmental psychology -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/18090 , vital:28575
- Description: Early maternal loss and its effects on daughters’ development has generated interest internationally. Yet very few studies have been conducted within South Africa, even though the prevalence of South African children growing up with the loss of their mothers is on the increase particularly due to HIV and Aids. This field of study is particularly important as mothers play a significant developmental role in children’s wellbeing. This study focused on exploring NMMU female students’ perceptions of the effects of maternal loss before adolescence on their identity and intimacy development. A qualitative research approach was followed in order to gain in-depth understanding regarding these perceived effects. A purposive, non-probability sampling method was employed to select participants and semi-structured interviews were conducted with them to explore and describe their perceptions. Attachment theory was utilised to provide a theoretical understanding of the potential impact of such loss on identity and intimacy development. Erikson’s psychosocial development theory was employed to describe the nature of personal identity and intimacy. The role of mothers in the South African context is perceived to be of importance with much focus on daughters’ identity development. Childhood maternal loss for daughters was perceived to effect the identity formation of participants in the study. The majority of participants perceived not having been able to spend enough time with their biological mothers to have limited their self-exploration. The participants perceived that this loss also had an effect on their intimacy as it isolated them from their peers and available support systems due to the fear of experiencing losing a person again in their lives.
- Full Text:
- Date Issued: 2017
- Authors: Makalima, Phaphama
- Date: 2017
- Subjects: Intimacy (Psychology) Identity (Psychology) , Students -- South Africa -- Psychological aspects Developmental psychology -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/18090 , vital:28575
- Description: Early maternal loss and its effects on daughters’ development has generated interest internationally. Yet very few studies have been conducted within South Africa, even though the prevalence of South African children growing up with the loss of their mothers is on the increase particularly due to HIV and Aids. This field of study is particularly important as mothers play a significant developmental role in children’s wellbeing. This study focused on exploring NMMU female students’ perceptions of the effects of maternal loss before adolescence on their identity and intimacy development. A qualitative research approach was followed in order to gain in-depth understanding regarding these perceived effects. A purposive, non-probability sampling method was employed to select participants and semi-structured interviews were conducted with them to explore and describe their perceptions. Attachment theory was utilised to provide a theoretical understanding of the potential impact of such loss on identity and intimacy development. Erikson’s psychosocial development theory was employed to describe the nature of personal identity and intimacy. The role of mothers in the South African context is perceived to be of importance with much focus on daughters’ identity development. Childhood maternal loss for daughters was perceived to effect the identity formation of participants in the study. The majority of participants perceived not having been able to spend enough time with their biological mothers to have limited their self-exploration. The participants perceived that this loss also had an effect on their intimacy as it isolated them from their peers and available support systems due to the fear of experiencing losing a person again in their lives.
- Full Text:
- Date Issued: 2017
The distribution and diversity of macroalgae in selected estuaries along the Eastern Cape coast of South Africa
- Authors: Prinsloo, Shireen
- Date: 2012
- Subjects: Estuarine ecology -- South Africa -- Eastern Cape , Algal communities -- South Africa -- Eastern Cape , Marine plants -- Economic aspects -- South Africa -- Eastern Cape , Estuarine area conservation -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10631 , http://hdl.handle.net/10948/d1012314 , Estuarine ecology -- South Africa -- Eastern Cape , Algal communities -- South Africa -- Eastern Cape , Marine plants -- Economic aspects -- South Africa -- Eastern Cape , Estuarine area conservation -- South Africa -- Eastern Cape
- Description: The growth and accumulation of macroalgae in estuaries are a common sight throughout the world (Boyer and Fong, 2005). Because macroalgae establish such complex but important links with other components within an estuary, it is essential to know which variables control and regulate their occurrences. The type of algae that will occur in an estuary depends however, on the physical and chemical features of the particular estuary (Lobban and Harrison, 1994). The focus of this study was to document and provide a listing of algae from estuaries around the Eastern Cape coast of South Africa and describe the communities which form within each estuarine habitat. The questions posed were: Do algae assemblages differ in estuaries with different environmental conditions? Are different plant communities inhabited by different algae communities? Also, are algae diverse in estuaries that are in a pristine condition? The estuaries were Mngazana, Ngqusi/Nxaxo, Mtati, Mpekweni, East Kleinemonde, West Kleinemonde, Kariega, Bushmans, Kowie and the Sundays estuary. Percentage cover surveys were conducted and environmental parameters recorded to determine community structure of algae and their environmental tolerances. A total of 49 different macroalgal species were identified from 11 estuaries, which were dominated by Chlorophytes (23 species) and Rhodophytes (17 species). The Ochrophytes consisted of 10 species. The highest number of species recorded was 29 at the Bushmans estuary (March 2009), while the lowest number (4 species) was recorded at Mtati (October 2008). Common Chlorophytes found included Ulva prolifera, Chaetomorpha linum and Codium tenue. In the Division Ochrophyta, species from the Genus Ectocarpus were the most common. Of the red algae filamentous reds, Polysiphonia incompta and Polysiphonia kowiensis were the common algae found at estuaries. Salinity (p= 0.029861; n= 49) and temperature (p= 0.037641; n= 49) were the driving environmental parameters of estuaries and significantly influenced richness of species. In ordination analyses, patterns of biogeographic distribution were noticeable and were described by salinity. Four gradients caused by salinity were therefore found – which is inversely correlated to water clarity. Moreover, a clear split between temporarily open/closed and the permanently open estuaries was observed. Samples grouped into four communities presumably based on the similarity in conditions of estuaries. Within each estuarine community and major type of estuary there was a range of environmental conditions. However, the macroalgae within each community may not have been colonists of or found in greatest abundances in the estuaries of these communities per se, but may have grouped together in this manner based on the optimum growing conditions for them. Also, specific algal groups were not directly determined by the type of estuary they were found in; they were driven by environmental ranges rather. The results therefore support hypothesis one which states species distribution and diversity differ and are influenced by environmental gradients of the estuary. Although close species and habitat relationships were apparent from the ordination analyses, providing support for hypothesis two which states “Different plant communities in estuaries will be inhabited by different macroalgae communities”, the evidence was not substantial enough to provide sufficient support for the hypothesis. Lastly, the hypothesis “Macroalgae are diverse in estuaries that are in a pristine condition” was not accepted as highest species numbers were found in estuaries of greatest anthropogenic disturbance (e.g. Bushmans estuary) and not in estuaries which where ecologically more natural (e.g. Mtati estuary). By doing monthly macroalgal sampling over a period of one year for example one would obtain greater information of biodiversity, and patterns of macroalgal seasonality may be uncovered as well. This is an area of reasearch which needs to be investigated in the future as it would greatly add to the understanding of the role macroalge have in an estuarine environment.
- Full Text:
- Date Issued: 2012
- Authors: Prinsloo, Shireen
- Date: 2012
- Subjects: Estuarine ecology -- South Africa -- Eastern Cape , Algal communities -- South Africa -- Eastern Cape , Marine plants -- Economic aspects -- South Africa -- Eastern Cape , Estuarine area conservation -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10631 , http://hdl.handle.net/10948/d1012314 , Estuarine ecology -- South Africa -- Eastern Cape , Algal communities -- South Africa -- Eastern Cape , Marine plants -- Economic aspects -- South Africa -- Eastern Cape , Estuarine area conservation -- South Africa -- Eastern Cape
- Description: The growth and accumulation of macroalgae in estuaries are a common sight throughout the world (Boyer and Fong, 2005). Because macroalgae establish such complex but important links with other components within an estuary, it is essential to know which variables control and regulate their occurrences. The type of algae that will occur in an estuary depends however, on the physical and chemical features of the particular estuary (Lobban and Harrison, 1994). The focus of this study was to document and provide a listing of algae from estuaries around the Eastern Cape coast of South Africa and describe the communities which form within each estuarine habitat. The questions posed were: Do algae assemblages differ in estuaries with different environmental conditions? Are different plant communities inhabited by different algae communities? Also, are algae diverse in estuaries that are in a pristine condition? The estuaries were Mngazana, Ngqusi/Nxaxo, Mtati, Mpekweni, East Kleinemonde, West Kleinemonde, Kariega, Bushmans, Kowie and the Sundays estuary. Percentage cover surveys were conducted and environmental parameters recorded to determine community structure of algae and their environmental tolerances. A total of 49 different macroalgal species were identified from 11 estuaries, which were dominated by Chlorophytes (23 species) and Rhodophytes (17 species). The Ochrophytes consisted of 10 species. The highest number of species recorded was 29 at the Bushmans estuary (March 2009), while the lowest number (4 species) was recorded at Mtati (October 2008). Common Chlorophytes found included Ulva prolifera, Chaetomorpha linum and Codium tenue. In the Division Ochrophyta, species from the Genus Ectocarpus were the most common. Of the red algae filamentous reds, Polysiphonia incompta and Polysiphonia kowiensis were the common algae found at estuaries. Salinity (p= 0.029861; n= 49) and temperature (p= 0.037641; n= 49) were the driving environmental parameters of estuaries and significantly influenced richness of species. In ordination analyses, patterns of biogeographic distribution were noticeable and were described by salinity. Four gradients caused by salinity were therefore found – which is inversely correlated to water clarity. Moreover, a clear split between temporarily open/closed and the permanently open estuaries was observed. Samples grouped into four communities presumably based on the similarity in conditions of estuaries. Within each estuarine community and major type of estuary there was a range of environmental conditions. However, the macroalgae within each community may not have been colonists of or found in greatest abundances in the estuaries of these communities per se, but may have grouped together in this manner based on the optimum growing conditions for them. Also, specific algal groups were not directly determined by the type of estuary they were found in; they were driven by environmental ranges rather. The results therefore support hypothesis one which states species distribution and diversity differ and are influenced by environmental gradients of the estuary. Although close species and habitat relationships were apparent from the ordination analyses, providing support for hypothesis two which states “Different plant communities in estuaries will be inhabited by different macroalgae communities”, the evidence was not substantial enough to provide sufficient support for the hypothesis. Lastly, the hypothesis “Macroalgae are diverse in estuaries that are in a pristine condition” was not accepted as highest species numbers were found in estuaries of greatest anthropogenic disturbance (e.g. Bushmans estuary) and not in estuaries which where ecologically more natural (e.g. Mtati estuary). By doing monthly macroalgal sampling over a period of one year for example one would obtain greater information of biodiversity, and patterns of macroalgal seasonality may be uncovered as well. This is an area of reasearch which needs to be investigated in the future as it would greatly add to the understanding of the role macroalge have in an estuarine environment.
- Full Text:
- Date Issued: 2012
Social sustainability of biogas production in Sogwala village, lower Gweru district, Zimbabwe
- Authors: Dhliwayo, Nyaradzo
- Date: 2010
- Subjects: Biogas -- Zimbabwe , Biogas -- Developing countries , Sustainability -- Zimbabwe
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:10648 , http://hdl.handle.net/10948/1459 , Biogas -- Zimbabwe , Biogas -- Developing countries , Sustainability -- Zimbabwe
- Description: The study has explored the social sustainability of biogas production in a local village of Sogwala which is located in the Lower Gweru District of Zimbabwe. The social sustainability assessment was based on the two concepts of social sustainability, namely human capital and social capital with particular emphasis on their respective elements and aspects. Qualitative and quantitative research methodology methods were used on a sample of 100 households using biogas and some key informants. Analysis of the variance was used to determine whether biogas production could account for any effects on the social and human capital elements of the Sogwala community. An overview and descriptive statistics analysis of the findings from the study have been provided where the biogas users’ experiences, perspectives are discussed and results were assessed. For instance, effects on the aspects of social capital elements which include increases in the social group membership of households after the introduction of biogas production the village; the performance of biogas energy as compared with other fuel sources in terms of accessibility, efficiency and the degree of labour needed for continual production of biogas. In view of the human capital element, assessment is done on the economic status per household before and after the production of biogas, where emphasis is placed on the aspects of employment, education and health indicators within the social sustainability context. The fundamental benefits from biogas production are considered and discussed with the technical issues surrounding biogas production also being presented. This is not just a technical unit for providing alternative energy supply, but it requires management, labour and knowledge, skills to operate on a daily basis for it to have an impact that can bring positive change to the daily social lives of both the young and old.
- Full Text:
- Date Issued: 2010
- Authors: Dhliwayo, Nyaradzo
- Date: 2010
- Subjects: Biogas -- Zimbabwe , Biogas -- Developing countries , Sustainability -- Zimbabwe
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:10648 , http://hdl.handle.net/10948/1459 , Biogas -- Zimbabwe , Biogas -- Developing countries , Sustainability -- Zimbabwe
- Description: The study has explored the social sustainability of biogas production in a local village of Sogwala which is located in the Lower Gweru District of Zimbabwe. The social sustainability assessment was based on the two concepts of social sustainability, namely human capital and social capital with particular emphasis on their respective elements and aspects. Qualitative and quantitative research methodology methods were used on a sample of 100 households using biogas and some key informants. Analysis of the variance was used to determine whether biogas production could account for any effects on the social and human capital elements of the Sogwala community. An overview and descriptive statistics analysis of the findings from the study have been provided where the biogas users’ experiences, perspectives are discussed and results were assessed. For instance, effects on the aspects of social capital elements which include increases in the social group membership of households after the introduction of biogas production the village; the performance of biogas energy as compared with other fuel sources in terms of accessibility, efficiency and the degree of labour needed for continual production of biogas. In view of the human capital element, assessment is done on the economic status per household before and after the production of biogas, where emphasis is placed on the aspects of employment, education and health indicators within the social sustainability context. The fundamental benefits from biogas production are considered and discussed with the technical issues surrounding biogas production also being presented. This is not just a technical unit for providing alternative energy supply, but it requires management, labour and knowledge, skills to operate on a daily basis for it to have an impact that can bring positive change to the daily social lives of both the young and old.
- Full Text:
- Date Issued: 2010
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