A commercial process development for plant food formulation using polyprotic acids from natural extracts as chelating agents
- Authors: Ndibewu, Peter Papoh
- Date: 2005
- Subjects: Chelates , Lemon juice , Liquid fertilizers
- Language: English
- Type: Thesis , Doctoral , DTech (Chemistry)
- Identifier: vital:10368 , http://hdl.handle.net/10948/153 , Chelates , Lemon juice , Liquid fertilizers
- Description: The citrus industry is one of South Africa's largest agricultural sectors in terms of export earnings with lemon fruits and juice as a trendsetter due to their high grade quality. According to growers, the Eastern Cape Province of South Africa alone produces an excess of about 10-14,000 tons of lemon juice which is presently of no economic value due to the sour taste and “bitterness”. As a result of this excess and in order to make use of the polyprotic acids naturally occurring in the lemon juice, four fertilizer nutrient mixtures are formulated, using lemon juice as base. From a conceptual scientific approach, characterization (physico-chemical and functional properties determinations) of Eureka Lemon fruit juices were undertaken, followed by smaller scale batch formulation experiments. On the basis that these lemon juice-based fertilizer mixtures are prepared following standard liquid fertilizer formulation guidelines, a field test was conducted to evaluate their potential effectiveness to influence plant growth. A growth chamber testing on tomato plants revealed high growth response (> 99.9 % certainty) potential in two of the semi-organic mixtures formulated while the organic mixture showed a relatively good growth rate as compared to the control (pure tap water). According to statistical analysis (ANOVA) comparison, two of the semi-organic mixtures performed considerably better than the two commercial samples evaluated. Potential benefits profoundly associated with these nutrient mixtures as compared to similar liquid fertilizer products on the market is that most nutrients are chelated and dissolved in solution. Also, the mixtures contain all necessary nutrients including plant growth substances required for healthier plant growth. The most important socioeconomic impact is the value addition to the technology chain in the citrus industry. The use of fluid fertilizers in significant quantities is less than twenty years old. Nevertheless, growth has been so rapid that in South Africa demand for mixed liquid fertilizer has greatly increased from 90 000 tons NPK & blended micronutrients in 1955 to more than 600 000 per annum tons today (Report 41/2003, Department of Minerals and Energy). The liquid fertilizers market is sparsely specialized with major competitors like Omnia, Kynoch and Foskor supplying more than 50 % of the market demand. Amongst the nutrient mixtures formulated, mixture one is an NPK (1-1-2) based nutrient mixture containing both secondary nutrients (0.5 % Mg & 1.0 % Ca) and seven micronutrients (0.1 % Fe, 0.05 % Cu, 0.05 % Zn, 0.05 % Mn, 0.02 % B, 0.0005 % Mo and 0.0005 % Co). The composition of this mixture offers the formula a potential to be used as a general purpose (all stages of plant growth) fertilization mixture in view of its balanced composition (containing all essential plant nutrients). Mixture two contains essentially the micronutrients and in higher concentrations (0.3 % Fe, 0.3 % Cu, 0.1 % Zn, 0.2 % Mn, 0.02 % B, 0.0005 % Mo and 0.0005 % Co) as compared to mixture one except for boron, molybdenum and cobalt. The concentration of the micronutrients contained in this mixture is adequately high which offers a potential for it to be used in supplementing nutrition in plants with critical micronutrient-deficient symptoms. Mixture three is very similar to mixture two (1.0 % Fe, 0.05 % Cu, 0.05 % Zn, 0.05 Mn, 0.05 % B, 0.0005 % Mo and 0.0005 % Co) except that the concentrations of all seven micronutrients are considerably less than those of contained in mixture two. However, the concentration of iron in this mixture is as high as 1.0 %. The mixture has a potential to be used in high iron-deficient situations. Mixture four is an organic formula with relatively low nutrient concentrations (NPK-0.02-0.02-1, 0.27 % Mg, 0.02 % Ca, 0.008 % Fe, 0.26 % Cu, 0.012 % Zn, 0.009 % Mn). Nevertheless, this mixture is appealing for organically grown crops where the use of chemicals is prohibited by standards. These lemon juice-based nutrient mixtures were further characterized and tested for stability and storability over a period of eight weeks. This study revealed no major change in the physical quality (colour, pH and “salt out” effect). The basic formulation methodology is a two-step procedure that involves filtration of the lemon juice to remove membranous materials, mixing at ambient temperature and stabilization of the nutrient mixtures. However, for the organic nutrient formula mix, filtration follows after extraction of nutrients from plant materials using the lemon juice.
- Full Text:
- Date Issued: 2005
- Authors: Ndibewu, Peter Papoh
- Date: 2005
- Subjects: Chelates , Lemon juice , Liquid fertilizers
- Language: English
- Type: Thesis , Doctoral , DTech (Chemistry)
- Identifier: vital:10368 , http://hdl.handle.net/10948/153 , Chelates , Lemon juice , Liquid fertilizers
- Description: The citrus industry is one of South Africa's largest agricultural sectors in terms of export earnings with lemon fruits and juice as a trendsetter due to their high grade quality. According to growers, the Eastern Cape Province of South Africa alone produces an excess of about 10-14,000 tons of lemon juice which is presently of no economic value due to the sour taste and “bitterness”. As a result of this excess and in order to make use of the polyprotic acids naturally occurring in the lemon juice, four fertilizer nutrient mixtures are formulated, using lemon juice as base. From a conceptual scientific approach, characterization (physico-chemical and functional properties determinations) of Eureka Lemon fruit juices were undertaken, followed by smaller scale batch formulation experiments. On the basis that these lemon juice-based fertilizer mixtures are prepared following standard liquid fertilizer formulation guidelines, a field test was conducted to evaluate their potential effectiveness to influence plant growth. A growth chamber testing on tomato plants revealed high growth response (> 99.9 % certainty) potential in two of the semi-organic mixtures formulated while the organic mixture showed a relatively good growth rate as compared to the control (pure tap water). According to statistical analysis (ANOVA) comparison, two of the semi-organic mixtures performed considerably better than the two commercial samples evaluated. Potential benefits profoundly associated with these nutrient mixtures as compared to similar liquid fertilizer products on the market is that most nutrients are chelated and dissolved in solution. Also, the mixtures contain all necessary nutrients including plant growth substances required for healthier plant growth. The most important socioeconomic impact is the value addition to the technology chain in the citrus industry. The use of fluid fertilizers in significant quantities is less than twenty years old. Nevertheless, growth has been so rapid that in South Africa demand for mixed liquid fertilizer has greatly increased from 90 000 tons NPK & blended micronutrients in 1955 to more than 600 000 per annum tons today (Report 41/2003, Department of Minerals and Energy). The liquid fertilizers market is sparsely specialized with major competitors like Omnia, Kynoch and Foskor supplying more than 50 % of the market demand. Amongst the nutrient mixtures formulated, mixture one is an NPK (1-1-2) based nutrient mixture containing both secondary nutrients (0.5 % Mg & 1.0 % Ca) and seven micronutrients (0.1 % Fe, 0.05 % Cu, 0.05 % Zn, 0.05 % Mn, 0.02 % B, 0.0005 % Mo and 0.0005 % Co). The composition of this mixture offers the formula a potential to be used as a general purpose (all stages of plant growth) fertilization mixture in view of its balanced composition (containing all essential plant nutrients). Mixture two contains essentially the micronutrients and in higher concentrations (0.3 % Fe, 0.3 % Cu, 0.1 % Zn, 0.2 % Mn, 0.02 % B, 0.0005 % Mo and 0.0005 % Co) as compared to mixture one except for boron, molybdenum and cobalt. The concentration of the micronutrients contained in this mixture is adequately high which offers a potential for it to be used in supplementing nutrition in plants with critical micronutrient-deficient symptoms. Mixture three is very similar to mixture two (1.0 % Fe, 0.05 % Cu, 0.05 % Zn, 0.05 Mn, 0.05 % B, 0.0005 % Mo and 0.0005 % Co) except that the concentrations of all seven micronutrients are considerably less than those of contained in mixture two. However, the concentration of iron in this mixture is as high as 1.0 %. The mixture has a potential to be used in high iron-deficient situations. Mixture four is an organic formula with relatively low nutrient concentrations (NPK-0.02-0.02-1, 0.27 % Mg, 0.02 % Ca, 0.008 % Fe, 0.26 % Cu, 0.012 % Zn, 0.009 % Mn). Nevertheless, this mixture is appealing for organically grown crops where the use of chemicals is prohibited by standards. These lemon juice-based nutrient mixtures were further characterized and tested for stability and storability over a period of eight weeks. This study revealed no major change in the physical quality (colour, pH and “salt out” effect). The basic formulation methodology is a two-step procedure that involves filtration of the lemon juice to remove membranous materials, mixing at ambient temperature and stabilization of the nutrient mixtures. However, for the organic nutrient formula mix, filtration follows after extraction of nutrients from plant materials using the lemon juice.
- Full Text:
- Date Issued: 2005
Material characterisation of laser formed dual phase steel components
- Authors: Els-Botes, Annelize
- Date: 2005
- Subjects: Steel -- Fatigue , Bending , Lasers , Sheet-steel -- Effect of lasers on
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9609 , http://hdl.handle.net/10948/176 , Steel -- Fatigue , Bending , Lasers , Sheet-steel -- Effect of lasers on
- Description: The nature and scope of this thesis can be divided into four categories: • FORMING PARAMETERS • Identification of various laser forming parameters in order to produce specimens of similar dimension (radius of curvature). • TEMPERATURE AND MICROSTRUCTURE • To study the effect of maximum temperature reached during the forming operation on the microstructure of the various specimens. • FATIGUE LIFE • Compare the fatigue life of the specimens produced by various laser parameters to that of the original material, and also the fatigue life of mechanical formed specimens. • RESIDUAL STRESS PROFILE Determine if the laser forming process induces detrimental residual stress magnitudes in the specimens. The main objective of this thesis was to gain an understanding of the way in which laser forming affects the fatigue performance and residual stress magnitude / distribution of dual phase steel. Although lasers have been used successfully in various manufacturing processes (welding, cutting, marking, etc.), little information is available on the influence of laser forming on many automotive alloys such as dual phase steel. The first part of the work involved a literature review of the process and factors affecting the laser forming process. It became clear from the literature overview that laser forming of sheet material thicker than 1mm is complex in nature. The variables that can influence the process are complicated and their interaction with each other is not easily controlled. The main parameters that were thus controlled in this study are as follows: • Laser power (P) • Laser head travel speed (v) • Laser beam size (mm) The chapters that follow the literature review, deals with the laser forming process of dual phase steel and the production of fatigue specimens using various laser parameters. It was found that the following laser parameters resulted in specimens with approximately the same radius of curvature: Laser power KW Beam diameter mm Interval spacing % Overlap Scanning velocity m/min Line Energy J/m 5 20 10 50 2,5 2000 3,1 14 10,5 25 2 1550 1,5 7,5 7,5 0 1,2 1250 From the results obtained from fatigue testing specimens produced with the above settings, it is clear that the laser forming process has the potential to be employed as a production stage in the manufacture of wheel centre discs while maintaining adequate fatigue strength. Large beam diameters which cause heat penetration through the thickness of the specimen and hence microstructure breakdown should be avoided, since it was shown that these specimens exhibited impaired mechanical properties than those produced with a smaller laser beam diameter. The microstructural changes observed during the forming process needs to be considered since the mechanical properties of the material changes with a change in microstructure. A dramatic change in microstructure was observed; therefore it is of crucial importance that microstructural evaluation plays an important part in deciding optimum laser parameters for the forming process of ferrous alloys. During residual stress analysis, trends were observed between measurements taken at the same location of the samples; regardless whether measurements were taken on the laser irradiated side or the reverse side of the specimen. The only difference was the magnitude of the relieved residual stress. In most cases the obtained relieved residual stress was much smaller in magnitude than that of the original plate (in the bulk of the material). The surface indicated a slight tensile residual stress for most samples evaluated. A good correlation in distribution profile was obtained between microhardness and relieved residual stress distribution at the ‘middle of sample’ location. This indicates that an increase in hardness indicates an increase in residual stress magnitude for the laser formed specimens. In conclusion, this research has proved that it is possible to deform metal plate of a 3,5mm thickness with a CO2 laser system. The research also established the effect of process parameters on the final product’s shape/bend angle and characterised the effect of the laser forming process on the material’s mechanical properties and structural integrity.
- Full Text:
- Date Issued: 2005
- Authors: Els-Botes, Annelize
- Date: 2005
- Subjects: Steel -- Fatigue , Bending , Lasers , Sheet-steel -- Effect of lasers on
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9609 , http://hdl.handle.net/10948/176 , Steel -- Fatigue , Bending , Lasers , Sheet-steel -- Effect of lasers on
- Description: The nature and scope of this thesis can be divided into four categories: • FORMING PARAMETERS • Identification of various laser forming parameters in order to produce specimens of similar dimension (radius of curvature). • TEMPERATURE AND MICROSTRUCTURE • To study the effect of maximum temperature reached during the forming operation on the microstructure of the various specimens. • FATIGUE LIFE • Compare the fatigue life of the specimens produced by various laser parameters to that of the original material, and also the fatigue life of mechanical formed specimens. • RESIDUAL STRESS PROFILE Determine if the laser forming process induces detrimental residual stress magnitudes in the specimens. The main objective of this thesis was to gain an understanding of the way in which laser forming affects the fatigue performance and residual stress magnitude / distribution of dual phase steel. Although lasers have been used successfully in various manufacturing processes (welding, cutting, marking, etc.), little information is available on the influence of laser forming on many automotive alloys such as dual phase steel. The first part of the work involved a literature review of the process and factors affecting the laser forming process. It became clear from the literature overview that laser forming of sheet material thicker than 1mm is complex in nature. The variables that can influence the process are complicated and their interaction with each other is not easily controlled. The main parameters that were thus controlled in this study are as follows: • Laser power (P) • Laser head travel speed (v) • Laser beam size (mm) The chapters that follow the literature review, deals with the laser forming process of dual phase steel and the production of fatigue specimens using various laser parameters. It was found that the following laser parameters resulted in specimens with approximately the same radius of curvature: Laser power KW Beam diameter mm Interval spacing % Overlap Scanning velocity m/min Line Energy J/m 5 20 10 50 2,5 2000 3,1 14 10,5 25 2 1550 1,5 7,5 7,5 0 1,2 1250 From the results obtained from fatigue testing specimens produced with the above settings, it is clear that the laser forming process has the potential to be employed as a production stage in the manufacture of wheel centre discs while maintaining adequate fatigue strength. Large beam diameters which cause heat penetration through the thickness of the specimen and hence microstructure breakdown should be avoided, since it was shown that these specimens exhibited impaired mechanical properties than those produced with a smaller laser beam diameter. The microstructural changes observed during the forming process needs to be considered since the mechanical properties of the material changes with a change in microstructure. A dramatic change in microstructure was observed; therefore it is of crucial importance that microstructural evaluation plays an important part in deciding optimum laser parameters for the forming process of ferrous alloys. During residual stress analysis, trends were observed between measurements taken at the same location of the samples; regardless whether measurements were taken on the laser irradiated side or the reverse side of the specimen. The only difference was the magnitude of the relieved residual stress. In most cases the obtained relieved residual stress was much smaller in magnitude than that of the original plate (in the bulk of the material). The surface indicated a slight tensile residual stress for most samples evaluated. A good correlation in distribution profile was obtained between microhardness and relieved residual stress distribution at the ‘middle of sample’ location. This indicates that an increase in hardness indicates an increase in residual stress magnitude for the laser formed specimens. In conclusion, this research has proved that it is possible to deform metal plate of a 3,5mm thickness with a CO2 laser system. The research also established the effect of process parameters on the final product’s shape/bend angle and characterised the effect of the laser forming process on the material’s mechanical properties and structural integrity.
- Full Text:
- Date Issued: 2005
Metalorganic vapour phase epitaxial growth and characterisation of Sb-based semiconductors
- Authors: Vankova, Viera
- Date: 2005
- Subjects: Compound semiconductors , Epitaxy , Organometallic compounds , Metal organic chemical vapor deposition
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10548 , http://hdl.handle.net/10948/d1019678
- Description: This study focuses on the growth and characterization of epitaxial InAs and InAs1-xSbx. Layers are grown on InAs, GaAs and GaSb substrates by metalorganic vapour phase epitaxy, using trimethylindium, trimethylantimony and arsine as precursors. The growth parameters (V/III ratio, Sb vapour phase compositions) are varied in the temperature range from 500 ºC to 700 ºC, in order to study the influence of these parameters on the structural, optical and electrical properties of the materials. The layers were assessed by X-ray diffraction, electron and optical microscopy, photoluminescence and Hall measurements. Furthermore, the influence of hydrogenation and annealing on the electrical and optical properties of GaSb was investigated. It is shown that the growth temperature and the V/III ratio play a vital role in the resulting surface morphology of homoepitaxial and heteroepitaxial InAs layers. Growth at low temperatures is found to promote three-dimensional growth in both cases, with improvements in the surface morphologies observed for higher growth temperatures. All the investigated epilayers are n-type. It is shown that the electrical properties of heteroepitaxial InAs epilayers are complicated by a competition between bulk conduction and conduction due to a surface accumulation and an interface layer. The low temperature photoluminescence spectra of homoepitaxial InAs are dominated by two transitions. These are identified as band-to-band/excitonic and donor-acceptor recombination. The incorporation efficiency of antimony (Sb) into InAs1-xSbx is dependent on the growth temperature and the V/III ratio. Under the growth conditions used in this study, the incorporation efficiency of Sb is controlled by the thermal stability of the two constituent binaries (i.e. InAs and InSb). Changes in the low temperature photoluminescence spectra are detected with increasing x. From temperature and laser power dependent measurements, the highest energy line is attributed to band-to-band/excitonic recombination, while the peak appearing approximately 15 meV below this line is assigned to donor-acceptor recombination. The origin of an additional “moving” peak observed for higher Sb mole fraction x is tentatively attributed to quasi-donor-acceptor-recombination, arising from increased impurity/defect concentrations and a higher compensation ratio in the material. However, the unusual behaviour of this peak may also be ascribed to the presence of some degree of ordering in InAsSb. The exposure of a semiconductor to a hydrogen plasma usually leads to the passivation of shallow and deep centres, thereby removing their electrical and optical activity. In this study, the passivation and thermal stability of the native acceptor in p-type GaSb is also investigated. It is shown that this acceptor can be passivated, where after improvements in the electrical and optical properties of GaSb are observed. Upon annealing the passivated samples above 300 °C, the acceptor is reactivated.
- Full Text:
- Date Issued: 2005
- Authors: Vankova, Viera
- Date: 2005
- Subjects: Compound semiconductors , Epitaxy , Organometallic compounds , Metal organic chemical vapor deposition
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10548 , http://hdl.handle.net/10948/d1019678
- Description: This study focuses on the growth and characterization of epitaxial InAs and InAs1-xSbx. Layers are grown on InAs, GaAs and GaSb substrates by metalorganic vapour phase epitaxy, using trimethylindium, trimethylantimony and arsine as precursors. The growth parameters (V/III ratio, Sb vapour phase compositions) are varied in the temperature range from 500 ºC to 700 ºC, in order to study the influence of these parameters on the structural, optical and electrical properties of the materials. The layers were assessed by X-ray diffraction, electron and optical microscopy, photoluminescence and Hall measurements. Furthermore, the influence of hydrogenation and annealing on the electrical and optical properties of GaSb was investigated. It is shown that the growth temperature and the V/III ratio play a vital role in the resulting surface morphology of homoepitaxial and heteroepitaxial InAs layers. Growth at low temperatures is found to promote three-dimensional growth in both cases, with improvements in the surface morphologies observed for higher growth temperatures. All the investigated epilayers are n-type. It is shown that the electrical properties of heteroepitaxial InAs epilayers are complicated by a competition between bulk conduction and conduction due to a surface accumulation and an interface layer. The low temperature photoluminescence spectra of homoepitaxial InAs are dominated by two transitions. These are identified as band-to-band/excitonic and donor-acceptor recombination. The incorporation efficiency of antimony (Sb) into InAs1-xSbx is dependent on the growth temperature and the V/III ratio. Under the growth conditions used in this study, the incorporation efficiency of Sb is controlled by the thermal stability of the two constituent binaries (i.e. InAs and InSb). Changes in the low temperature photoluminescence spectra are detected with increasing x. From temperature and laser power dependent measurements, the highest energy line is attributed to band-to-band/excitonic recombination, while the peak appearing approximately 15 meV below this line is assigned to donor-acceptor recombination. The origin of an additional “moving” peak observed for higher Sb mole fraction x is tentatively attributed to quasi-donor-acceptor-recombination, arising from increased impurity/defect concentrations and a higher compensation ratio in the material. However, the unusual behaviour of this peak may also be ascribed to the presence of some degree of ordering in InAsSb. The exposure of a semiconductor to a hydrogen plasma usually leads to the passivation of shallow and deep centres, thereby removing their electrical and optical activity. In this study, the passivation and thermal stability of the native acceptor in p-type GaSb is also investigated. It is shown that this acceptor can be passivated, where after improvements in the electrical and optical properties of GaSb are observed. Upon annealing the passivated samples above 300 °C, the acceptor is reactivated.
- Full Text:
- Date Issued: 2005
On the growth and characterisation of AIGaN alloys for optoelectronic applications
- Authors: James, Grant Robert
- Date: 2005
- Subjects: Gallium nitride -- Electric properties , Photoluminescence
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/8824 , vital:26433
- Description: In this study the growth and characterisation of undoped and Si-doped AlxGa1-xN has been performed. The layers were grown using low-pressure metalorganic vapour phase deposition (MOCVD) on sapphire substrates. The optical and electrical properties of the AlxGa1-xN layers were studied using variable temperature Hall effect and photoluminescence measurements. AlxGa1-xN layers were grown over the entire composition range. Room temperature ultraviolet (UV) transmission measurements showed that the material quality was very good for layers with an Al content, x, of 0 _ x _ 0.5. However, the quality of layers of higher composition was seen to rapidly decrease with increasing x. The electrical and optical properties of AlxGa1-xN with x < 0.5 were also good, comparable to those reported on in literature. The study of the Si-doping of AlxGa1-xN was performed in two parts; firstly a series of Al0.23Ga0.77N samples was grown in which the doping level was increased from zero to n _ 3 × 1018 cm-3. A similar, albeit a less rigorous, study was performed for Al0.41Ga0.59N and Al0.5Ga0.5N. A second series of samples was then grown in which the doping level was kept constant, while the Al content was incrementally increased. Room temperature Hall effect measurements performed on Si-doped Al0.23Ga0.77N showed that the electron concentration did not scale linearly with the silane flow, as was the case in GaN. It was also seen that the electron mobility of the layers increased with slight Si-doping, possibly due to an improvement in the crystalline quality and/or a change in the conduction mechanism. It was also found that at higher compositions (x = 0.41 and 0.50) an increase in the doping level resulted in an increase in the mobility. Variable temperature Hall effect and photoluminescence measurements, performed on the Al0.23Ga0.77N samples, revealed a good correlation between the first PL activation energy E1 and the donor activation energy ED, prompting the conclusion that the first PL recombination channel in AlxGa1-xN is due to the delocalisation of excitons bound at neutral Si donors. Furthermore, E1 and ED were seen to decrease with n1/3, as is the case for GaN and other semiconductor materials. It was also observed that strong exciton localisation occurs in slightly Si-doped material, with the amount of localization becoming less at higher doping levels. Possible mechanisms responsible for the second PL recombination channel of activation energy E2 were also proposed. The electrical and optical properties of the second set of AlxGa1-xN samples was then studied. The PL properties of undoped AlxGa1-xN were typical of a homogeneous alloy system, with the increase in the PL FWHM and exciton localisation energies with x following the trend predicted by alloy disorder theory. The variation of the band gap energy with the Al content could not, however, be fitted over the entire composition range using a single bowing parameter. It was proposed that this was due either to an effect of the 9 7 valence band crossover, or due to exciton localisation at alloy disorder and/or impurities. As was the case for GaN and Al0.23Ga0.77N, all undoped material was highly resistive. As was mentioned earlier, the exciton localisation energies increased according to alloy disorder theory in undoped AlxGa1-xN. In the doped samples, however, a large increase in the donor localisation energy was measured for x > 0.3. The possibility that Si could become a DX-centre in AlxGa1-xN was then investigated. However, Hall effect measurements showed that the Si activation energy increased in good agreement with the model of a shallow effective mass state donor, with no sudden increase in ED being observed up to x = 0.4. It was then suggested that the increase in the E1 and E2 activation energies, as well as the exciton localisation energies, could be due to the 9 7 valence band crossover, which occurs at roughly the same composition. However, due to the scarcity of reports on the valence band structure in AlxGa1-xN no conclusions could be made at this stage as to the effect of the 9 7 valence band crossover on the PL properties of AlxGa1-xN.
- Full Text:
- Date Issued: 2005
- Authors: James, Grant Robert
- Date: 2005
- Subjects: Gallium nitride -- Electric properties , Photoluminescence
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/8824 , vital:26433
- Description: In this study the growth and characterisation of undoped and Si-doped AlxGa1-xN has been performed. The layers were grown using low-pressure metalorganic vapour phase deposition (MOCVD) on sapphire substrates. The optical and electrical properties of the AlxGa1-xN layers were studied using variable temperature Hall effect and photoluminescence measurements. AlxGa1-xN layers were grown over the entire composition range. Room temperature ultraviolet (UV) transmission measurements showed that the material quality was very good for layers with an Al content, x, of 0 _ x _ 0.5. However, the quality of layers of higher composition was seen to rapidly decrease with increasing x. The electrical and optical properties of AlxGa1-xN with x < 0.5 were also good, comparable to those reported on in literature. The study of the Si-doping of AlxGa1-xN was performed in two parts; firstly a series of Al0.23Ga0.77N samples was grown in which the doping level was increased from zero to n _ 3 × 1018 cm-3. A similar, albeit a less rigorous, study was performed for Al0.41Ga0.59N and Al0.5Ga0.5N. A second series of samples was then grown in which the doping level was kept constant, while the Al content was incrementally increased. Room temperature Hall effect measurements performed on Si-doped Al0.23Ga0.77N showed that the electron concentration did not scale linearly with the silane flow, as was the case in GaN. It was also seen that the electron mobility of the layers increased with slight Si-doping, possibly due to an improvement in the crystalline quality and/or a change in the conduction mechanism. It was also found that at higher compositions (x = 0.41 and 0.50) an increase in the doping level resulted in an increase in the mobility. Variable temperature Hall effect and photoluminescence measurements, performed on the Al0.23Ga0.77N samples, revealed a good correlation between the first PL activation energy E1 and the donor activation energy ED, prompting the conclusion that the first PL recombination channel in AlxGa1-xN is due to the delocalisation of excitons bound at neutral Si donors. Furthermore, E1 and ED were seen to decrease with n1/3, as is the case for GaN and other semiconductor materials. It was also observed that strong exciton localisation occurs in slightly Si-doped material, with the amount of localization becoming less at higher doping levels. Possible mechanisms responsible for the second PL recombination channel of activation energy E2 were also proposed. The electrical and optical properties of the second set of AlxGa1-xN samples was then studied. The PL properties of undoped AlxGa1-xN were typical of a homogeneous alloy system, with the increase in the PL FWHM and exciton localisation energies with x following the trend predicted by alloy disorder theory. The variation of the band gap energy with the Al content could not, however, be fitted over the entire composition range using a single bowing parameter. It was proposed that this was due either to an effect of the 9 7 valence band crossover, or due to exciton localisation at alloy disorder and/or impurities. As was the case for GaN and Al0.23Ga0.77N, all undoped material was highly resistive. As was mentioned earlier, the exciton localisation energies increased according to alloy disorder theory in undoped AlxGa1-xN. In the doped samples, however, a large increase in the donor localisation energy was measured for x > 0.3. The possibility that Si could become a DX-centre in AlxGa1-xN was then investigated. However, Hall effect measurements showed that the Si activation energy increased in good agreement with the model of a shallow effective mass state donor, with no sudden increase in ED being observed up to x = 0.4. It was then suggested that the increase in the E1 and E2 activation energies, as well as the exciton localisation energies, could be due to the 9 7 valence band crossover, which occurs at roughly the same composition. However, due to the scarcity of reports on the valence band structure in AlxGa1-xN no conclusions could be made at this stage as to the effect of the 9 7 valence band crossover on the PL properties of AlxGa1-xN.
- Full Text:
- Date Issued: 2005
The development of an electrochemical process for the production of para-substituted di-hydroxy benzenes
- Authors: Rautenbach, Daniel
- Date: 2005
- Subjects: Phenol , Benzene
- Language: English
- Type: Thesis , Doctoral , DTech (Science)
- Identifier: vital:10367 , http://hdl.handle.net/10948/159 , Phenol , Benzene
- Description: The project was concerned with the investigation of the electrochemical oxidation of various phenols, and to develop a viable reaction system for the production of the respective hydroquinones. Current production routes utilizing phenol as starting material have the limitations of using large amounts of acids, having to be stopped at low conversions and producing a mixture of the hydroquinones and catechols. Of the possible routes to the respective hydroquinones from the various phenols, the electrochemical oxidation of these phenols offers commercial and environmental advantages and hence formed the theme of the investigation. The synthetic possibilities proved to be more prevalent in a system when the electrochemical oxidation of these phenols was performed in an aqueous medium utilizing an organic co-solvent. Results obtained during this investigation made it possible to make certain predications about the mechanism taking place. This was found to depend on the anode material used for the oxidation. The results showed that the process developed for the electrochemical oxidation of these phenols, yields mainly the para-isomers of the respective hydroquinones and benzoquinones in good yields and selectivities, with fair current efficiencies and good mass balances at high conversions. For example: * Phenol (batch) 8 F: 345% current efficiency, 70% hydroquinone, 6% catechol, 9% benzoquinone, 9% phenol and 94 mass balance. * 2-Tert-butylphenol (flow) 10 F: 37% current efficiency, 65% hydroquinone, 33% benzoquinone, 2% phenol and 100% mass balance. * 2,6-Di-tert-butylphenol (flow) 11 F: 23% current efficiency, 92 % hydroquinone, 6% benzoquinone, 1% phenol and 99% mass balance. The developed electrochemical oxidation system offers the following advantages over previous and current methods: simplified isolation and extraction procedures, smaller amounts of acid usage, reasonably selective synthesis of the para-isomer and a less corrosive system all at high conversions.
- Full Text:
- Date Issued: 2005
- Authors: Rautenbach, Daniel
- Date: 2005
- Subjects: Phenol , Benzene
- Language: English
- Type: Thesis , Doctoral , DTech (Science)
- Identifier: vital:10367 , http://hdl.handle.net/10948/159 , Phenol , Benzene
- Description: The project was concerned with the investigation of the electrochemical oxidation of various phenols, and to develop a viable reaction system for the production of the respective hydroquinones. Current production routes utilizing phenol as starting material have the limitations of using large amounts of acids, having to be stopped at low conversions and producing a mixture of the hydroquinones and catechols. Of the possible routes to the respective hydroquinones from the various phenols, the electrochemical oxidation of these phenols offers commercial and environmental advantages and hence formed the theme of the investigation. The synthetic possibilities proved to be more prevalent in a system when the electrochemical oxidation of these phenols was performed in an aqueous medium utilizing an organic co-solvent. Results obtained during this investigation made it possible to make certain predications about the mechanism taking place. This was found to depend on the anode material used for the oxidation. The results showed that the process developed for the electrochemical oxidation of these phenols, yields mainly the para-isomers of the respective hydroquinones and benzoquinones in good yields and selectivities, with fair current efficiencies and good mass balances at high conversions. For example: * Phenol (batch) 8 F: 345% current efficiency, 70% hydroquinone, 6% catechol, 9% benzoquinone, 9% phenol and 94 mass balance. * 2-Tert-butylphenol (flow) 10 F: 37% current efficiency, 65% hydroquinone, 33% benzoquinone, 2% phenol and 100% mass balance. * 2,6-Di-tert-butylphenol (flow) 11 F: 23% current efficiency, 92 % hydroquinone, 6% benzoquinone, 1% phenol and 99% mass balance. The developed electrochemical oxidation system offers the following advantages over previous and current methods: simplified isolation and extraction procedures, smaller amounts of acid usage, reasonably selective synthesis of the para-isomer and a less corrosive system all at high conversions.
- Full Text:
- Date Issued: 2005
The development of best practice guidelines for the contingency management of health-related absenteeism in the motor manufacturing industry
- Authors: Werner, Amanda
- Date: 2005
- Subjects: Sick leave , Absenteeism (Labor) , Contingency theory (Management) , Automobile industry and trade -- South Africa
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9379 , http://hdl.handle.net/10948/160 , Sick leave , Absenteeism (Labor) , Contingency theory (Management) , Automobile industry and trade -- South Africa
- Description: The research problem in this study was to identify best practices for the contingency management of health-related absenteeism. To achieve this goal, the following actions were taken: A literature study was conducted to identify the scope and impact of health-related absenteeism on organisations and the legal parameters within which health-related absenteeism should be managed. A literature study was also conducted to identify strategies to prevent and reduce health-related absenteeism and strategies to ensure the continuous provision of products and services in periods of high absenteeism. The theoretical study focused on the management of absenteeism, wellness, ill-health/mental problems and HIV/AIDS, as well as contingency strategies aimed at maintaining production and service provision. iii The findings from the literature study were integrated into a model of best practices for the contingency management of health-related absenteeism. This model was used as a basis for the development of a survey questionnaire to determine whether senior human resources practitioners, occupational health practitioners or line managers, who were responsible for the management of health-related absenteeism in organisations, agreed with the best practice guidelines developed in the study. The survey was conducted in the motor and motor component industry in the Nelson Mandela Metropolitan Municipality and Buffalo City Metropole. The empirical results from the study showed a strong concurrence with the best practices guidelines developed in the study, with the exception of the strategies aimed at maintaining undisrupted production and service provision during periods of high absenteeism. In particular, disagreement was shown with regard to alternative work arrangements such as flexible work-hours, a compressed workweek, telecommuting and job-sharing. Absenteeism, in general, is an issue that organisations are challenged with on a daily basis. The proliferation of various diseases, specifically HIV/AIDS, is contributing to this problem. An integrated and strategic approach is required to deal effectively and constructively with the immediate and expected future impact of health-related issues on absenteeism. Organisations could use the best practices guidelines, identified in this study, as a mechanism to benchmark how well they manage health-related absenteeism
- Full Text:
- Date Issued: 2005
- Authors: Werner, Amanda
- Date: 2005
- Subjects: Sick leave , Absenteeism (Labor) , Contingency theory (Management) , Automobile industry and trade -- South Africa
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9379 , http://hdl.handle.net/10948/160 , Sick leave , Absenteeism (Labor) , Contingency theory (Management) , Automobile industry and trade -- South Africa
- Description: The research problem in this study was to identify best practices for the contingency management of health-related absenteeism. To achieve this goal, the following actions were taken: A literature study was conducted to identify the scope and impact of health-related absenteeism on organisations and the legal parameters within which health-related absenteeism should be managed. A literature study was also conducted to identify strategies to prevent and reduce health-related absenteeism and strategies to ensure the continuous provision of products and services in periods of high absenteeism. The theoretical study focused on the management of absenteeism, wellness, ill-health/mental problems and HIV/AIDS, as well as contingency strategies aimed at maintaining production and service provision. iii The findings from the literature study were integrated into a model of best practices for the contingency management of health-related absenteeism. This model was used as a basis for the development of a survey questionnaire to determine whether senior human resources practitioners, occupational health practitioners or line managers, who were responsible for the management of health-related absenteeism in organisations, agreed with the best practice guidelines developed in the study. The survey was conducted in the motor and motor component industry in the Nelson Mandela Metropolitan Municipality and Buffalo City Metropole. The empirical results from the study showed a strong concurrence with the best practices guidelines developed in the study, with the exception of the strategies aimed at maintaining undisrupted production and service provision during periods of high absenteeism. In particular, disagreement was shown with regard to alternative work arrangements such as flexible work-hours, a compressed workweek, telecommuting and job-sharing. Absenteeism, in general, is an issue that organisations are challenged with on a daily basis. The proliferation of various diseases, specifically HIV/AIDS, is contributing to this problem. An integrated and strategic approach is required to deal effectively and constructively with the immediate and expected future impact of health-related issues on absenteeism. Organisations could use the best practices guidelines, identified in this study, as a mechanism to benchmark how well they manage health-related absenteeism
- Full Text:
- Date Issued: 2005
The development of motivational strategies for public sector workers in Kenya
- Authors: Chepkilot, Ronald Kiprop
- Date: 2005
- Subjects: Public administration -- Kenya , Employee motivation , Civil service -- Kenya -- Personnel management
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9380 , http://hdl.handle.net/10948/161 , Public administration -- Kenya , Employee motivation , Civil service -- Kenya -- Personnel management
- Description: The purpose of this study was to develop motivational strategies for motivating public sector workers in Kenya. To achieve this objective the following procedure was followed: • An examination of the public service was undertaken and the following factors were considered: The history of the public service; Past government reform programmes; The problem of corruption; Future government reform programmes; and The motivational climate in the service. iv • A literature survey was conducted on the approaches used by organisations in motivating employees. The findings were used to develop a motivational strategy model. On the basis of the strategies in the model, a questionnaire was developed for the empirical research study. • The empirical study was undertaken to examine the level of motivation in the public service and to identify the motivational strategies currently used in the public service in Kenya. The study also sought to determine the extent to which public sector managers agreed or disagreed that the motivational strategies developed by the study would be effective in motivating employees in their organisations. The results of the empirical study were incorporated into the integrated motivational strategy model presented in chapter six. The study established that the level of motivation among the public sector workers was extremely low. According to the research findings, 87 per cent of the respondents indicated that the level of motivation of employees in their organisation was low while 13 per cent indicated that it was high. It was also established that the climate in the public service was not conducive for motivating employees: the indicators were lack of job security; very low salaries; limited training and development opportunities; lack of career development programmes and lack of adequate working tools and equipment. It was further established that the government could no longer afford to make any substantial increases in salaries to the workers because the wage bill was extremely high at the level of 9.6 per cent of the GDP. It was observed that any further increases in salaries would v have a negative impact on the economy of the country. In view of the above, this study becomes extremely relevant as it suggests ways of enhancing the levels of motivation in the public service to improve service delivery in the public sector without allocation of vast financial resources. The study strongly recommends the application of the integrated motivational strategy model in its entirety; to enhance the level of employee’s motivation and work performance and achieve efficiency and effectiveness in service delivery. The study also recommends that further research be carried out to determine the effects of corruption on employee motivation and ways of eliminating the vice in the public service.
- Full Text:
- Date Issued: 2005
- Authors: Chepkilot, Ronald Kiprop
- Date: 2005
- Subjects: Public administration -- Kenya , Employee motivation , Civil service -- Kenya -- Personnel management
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9380 , http://hdl.handle.net/10948/161 , Public administration -- Kenya , Employee motivation , Civil service -- Kenya -- Personnel management
- Description: The purpose of this study was to develop motivational strategies for motivating public sector workers in Kenya. To achieve this objective the following procedure was followed: • An examination of the public service was undertaken and the following factors were considered: The history of the public service; Past government reform programmes; The problem of corruption; Future government reform programmes; and The motivational climate in the service. iv • A literature survey was conducted on the approaches used by organisations in motivating employees. The findings were used to develop a motivational strategy model. On the basis of the strategies in the model, a questionnaire was developed for the empirical research study. • The empirical study was undertaken to examine the level of motivation in the public service and to identify the motivational strategies currently used in the public service in Kenya. The study also sought to determine the extent to which public sector managers agreed or disagreed that the motivational strategies developed by the study would be effective in motivating employees in their organisations. The results of the empirical study were incorporated into the integrated motivational strategy model presented in chapter six. The study established that the level of motivation among the public sector workers was extremely low. According to the research findings, 87 per cent of the respondents indicated that the level of motivation of employees in their organisation was low while 13 per cent indicated that it was high. It was also established that the climate in the public service was not conducive for motivating employees: the indicators were lack of job security; very low salaries; limited training and development opportunities; lack of career development programmes and lack of adequate working tools and equipment. It was further established that the government could no longer afford to make any substantial increases in salaries to the workers because the wage bill was extremely high at the level of 9.6 per cent of the GDP. It was observed that any further increases in salaries would v have a negative impact on the economy of the country. In view of the above, this study becomes extremely relevant as it suggests ways of enhancing the levels of motivation in the public service to improve service delivery in the public sector without allocation of vast financial resources. The study strongly recommends the application of the integrated motivational strategy model in its entirety; to enhance the level of employee’s motivation and work performance and achieve efficiency and effectiveness in service delivery. The study also recommends that further research be carried out to determine the effects of corruption on employee motivation and ways of eliminating the vice in the public service.
- Full Text:
- Date Issued: 2005
The oxidative coupling of phenols using stoichiometric metal oxidants
- Authors: Hoffmann, Eric
- Date: 2005
- Subjects: Phenols , Oxidation , Stoichiometry
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10977 , http://hdl.handle.net/10948/180 , Phenols , Oxidation , Stoichiometry
- Description: The oxidative coupling of 2,6-di-t-butylphenol under mild reaction conditions is well documented and the subject of many patents. However, the coupling of other monoand di- substituted phenols is not as well documented and thus there is scope for further investigation for providing a convenient, environmentally friendly and economically viable method for the oxidative coupling of these phenols. In this study, the oxidative coupling of a variety of alkylated phenolic substrates, 2-tbutylphenol, 2,6-di-t-butylphenol, 2,4 -di-t-butylphenol and ,4-dimethylphenol, using a range of different oxidizing agents, were investigated by means of experimental and/or theoretical means. The dibutylated aromatics provided the highest selectivities to their respective coupled products, with results obtained with the dimethyl analogue being only satisfactory, and that for 2 -t-butylphenol being totally inefficient. PM3 Molecular orbital (MO) calculations were used to predict the possible modes of coupling for the substrates 2,6 -di-t-butylphenol and 2,4-di-t-butylphenol, and these results were then compared with those obtained experimentally in the laboratory. Preliminarily, the coupling of unsubstituted phenolics was also assessed by means of MO calculations. Much emphasis was placed on Ce(IV) as the oxidant, and the reaction conditions under which it was used and the results that were obtained have not been reported before and are therefore novel. The oxidation of 2,4-di-t-butylphenol using Ce(IV) in the presence of methanesulphonic acid was optimized to afford high yields and selectivities to the desired ortho C-ortho C coupled product under mild reaction conditions. Various reaction parameters were also investigated in this case, such as varying the MeSO3H concentration, the solvent, the reaction temperature, the reaction time, the substrate loading, the rate of oxidant addition and the substrate to oxidant ratio. Ce(IV) also gave a high selectivity to the para C-para C coupled product when IX using 2,6-di-t-butylphenol as the substrate. However, it was not as effective with 2,4- dimethylphenol, and even less so with 2-t-butylphenol. The oxidation reactions of 2-t-butylphenol and 2,4-dimethylphenol with various coupling agents were also investigated with the intention of obtaining high selectivities to the respective desired coupled products. In these studies, 2-t-butylphenol afforded a large number of products, irrespective of the oxidant used. The dimethyl analogue was more selective, but results were not optimal. It was clear that the number of substituents on the phenol ring, their nature and their position with regards to the hydroxyl moiety was of great importance and made a significant impact on the preferred coupling mode of the substrate. It was observed that steric effects also played a major role in the outcome of these reactions: 2,6-di-t-butylphenol never afforded any C-O coupled products whereas 2-t-butylphenol, 2,4-di-t-butylphenol and 2,4-dimethylphenol all appeared to undergo some C-O coupling. Finally, reaction mechanisms were provided for both the K3Fe(CN)6 and Ce(IV) work, these reacting in basic and acidic media, respectively. It was proposed that both of these mechanisms operate through the initial formation of the phenoxyl radical.
- Full Text:
- Date Issued: 2005
- Authors: Hoffmann, Eric
- Date: 2005
- Subjects: Phenols , Oxidation , Stoichiometry
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10977 , http://hdl.handle.net/10948/180 , Phenols , Oxidation , Stoichiometry
- Description: The oxidative coupling of 2,6-di-t-butylphenol under mild reaction conditions is well documented and the subject of many patents. However, the coupling of other monoand di- substituted phenols is not as well documented and thus there is scope for further investigation for providing a convenient, environmentally friendly and economically viable method for the oxidative coupling of these phenols. In this study, the oxidative coupling of a variety of alkylated phenolic substrates, 2-tbutylphenol, 2,6-di-t-butylphenol, 2,4 -di-t-butylphenol and ,4-dimethylphenol, using a range of different oxidizing agents, were investigated by means of experimental and/or theoretical means. The dibutylated aromatics provided the highest selectivities to their respective coupled products, with results obtained with the dimethyl analogue being only satisfactory, and that for 2 -t-butylphenol being totally inefficient. PM3 Molecular orbital (MO) calculations were used to predict the possible modes of coupling for the substrates 2,6 -di-t-butylphenol and 2,4-di-t-butylphenol, and these results were then compared with those obtained experimentally in the laboratory. Preliminarily, the coupling of unsubstituted phenolics was also assessed by means of MO calculations. Much emphasis was placed on Ce(IV) as the oxidant, and the reaction conditions under which it was used and the results that were obtained have not been reported before and are therefore novel. The oxidation of 2,4-di-t-butylphenol using Ce(IV) in the presence of methanesulphonic acid was optimized to afford high yields and selectivities to the desired ortho C-ortho C coupled product under mild reaction conditions. Various reaction parameters were also investigated in this case, such as varying the MeSO3H concentration, the solvent, the reaction temperature, the reaction time, the substrate loading, the rate of oxidant addition and the substrate to oxidant ratio. Ce(IV) also gave a high selectivity to the para C-para C coupled product when IX using 2,6-di-t-butylphenol as the substrate. However, it was not as effective with 2,4- dimethylphenol, and even less so with 2-t-butylphenol. The oxidation reactions of 2-t-butylphenol and 2,4-dimethylphenol with various coupling agents were also investigated with the intention of obtaining high selectivities to the respective desired coupled products. In these studies, 2-t-butylphenol afforded a large number of products, irrespective of the oxidant used. The dimethyl analogue was more selective, but results were not optimal. It was clear that the number of substituents on the phenol ring, their nature and their position with regards to the hydroxyl moiety was of great importance and made a significant impact on the preferred coupling mode of the substrate. It was observed that steric effects also played a major role in the outcome of these reactions: 2,6-di-t-butylphenol never afforded any C-O coupled products whereas 2-t-butylphenol, 2,4-di-t-butylphenol and 2,4-dimethylphenol all appeared to undergo some C-O coupling. Finally, reaction mechanisms were provided for both the K3Fe(CN)6 and Ce(IV) work, these reacting in basic and acidic media, respectively. It was proposed that both of these mechanisms operate through the initial formation of the phenoxyl radical.
- Full Text:
- Date Issued: 2005
Virtuous living towards an African theology of wisdom in the context of the African renaissance
- Nkesiga, Reverend Solomon Basabose
- Authors: Nkesiga, Reverend Solomon Basabose
- Date: 2005
- Subjects: Wisdom -- Religious aspects , Ethics -- Africa -- Religious aspects , Black theology
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:8414 , http://hdl.handle.net/10948/454 , http://hdl.handle.net/10948/d1011900 , Wisdom -- Religious aspects , Ethics -- Africa -- Religious aspects , Black theology
- Description: The structure of this study is a complex inter-relationship of a variety of sources in a theological work, namely, personal experience, African social and politico-economic context, philosophical reflection, wisdom traditions and Christian theology. These sources form a coherent inter-relationship which is foundational for an African theology of wisdom. The introduction gives an overview of my moral and theological formation. This is intended to provide a perspective through which the issue of moral orientation in African context has been approached. It is therefore entitled: Moral formation and the shaping of a theological mind. The first chapter answers the question: Why is Africa in need of a wisdom theology that addresses the issue of moral regeneration? This question is posed in the broader context of the current African Renaissance debates. The links between the Italian (European) and African Renaissance indicate that moral regeneration is a crucial part of the socio-political, intellectual and economic re-birth of Africa. This “socio-historical” source gives the context and urgency of a wisdom theology. It is therefore entitled: A contextual analysis: The European and African Renaissance. The second chapter re-asserts the rise of virtue ethics as an alternative ethical theory to the predominant deontological and utilitarian traditions. This is achieved through analysing Alisdair MacIntyre’s earlier work, After Virtue: A Study in Moral Theory (1981), set in the context of Iris Murdoch and Elizabeth Anscombe, the modern initiators of a virtue ethic. This “philosophical” source gives the theoretical framework that addresses the question of moral formation. It is therefore entitled: A philosophical analysis: The rise of virtue ethics as alternative ethical theory. The third chapter is devoted to two related “wisdom” themes: Firstly, the seven traditional virtues are briefly described highlighting the virtue of wisdom as foundational. Secondly, the idea of wisdom is further developed via three wisdom traditions, namely: wisdom in the Hellenistic, Judeo-Christian and African traditions. This “sapiential” source gives this African theology of wisdom its most important building blocks. This chapter is therefore entitled: A sapiential analysis: Wisdom as foundation for virtue ethics in Africa. The last chapter brings the previous sources together under a specific theological perspective. It draws on aspects of recent African theologians’ work, notably: Kwame Gyekye and Benezet Bujo who engage with and bring together Western and African theological traditions. I answer a pertinent question, “What does such a ‘theological’ perspective entail?” I draw on Scripture and its Trinitarian tradition to demonstrate how African wisdom, reinforced by the framework of virtue theory, and developed in the context of present-day Africa by an African student of theology, has the potential to contribute to the moral transformation of Africa. This more overt “theological” source is the distinctive Christian enterprise of an African wisdom theology. The chapter title is aligned with the overall title of this study: A theological analysis: Toward an African virtue ethics? To this end, this study achieves its attempt to construct an inter-related framework from which an African theology of wisdom may emerge.
- Full Text:
- Date Issued: 2005
- Authors: Nkesiga, Reverend Solomon Basabose
- Date: 2005
- Subjects: Wisdom -- Religious aspects , Ethics -- Africa -- Religious aspects , Black theology
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:8414 , http://hdl.handle.net/10948/454 , http://hdl.handle.net/10948/d1011900 , Wisdom -- Religious aspects , Ethics -- Africa -- Religious aspects , Black theology
- Description: The structure of this study is a complex inter-relationship of a variety of sources in a theological work, namely, personal experience, African social and politico-economic context, philosophical reflection, wisdom traditions and Christian theology. These sources form a coherent inter-relationship which is foundational for an African theology of wisdom. The introduction gives an overview of my moral and theological formation. This is intended to provide a perspective through which the issue of moral orientation in African context has been approached. It is therefore entitled: Moral formation and the shaping of a theological mind. The first chapter answers the question: Why is Africa in need of a wisdom theology that addresses the issue of moral regeneration? This question is posed in the broader context of the current African Renaissance debates. The links between the Italian (European) and African Renaissance indicate that moral regeneration is a crucial part of the socio-political, intellectual and economic re-birth of Africa. This “socio-historical” source gives the context and urgency of a wisdom theology. It is therefore entitled: A contextual analysis: The European and African Renaissance. The second chapter re-asserts the rise of virtue ethics as an alternative ethical theory to the predominant deontological and utilitarian traditions. This is achieved through analysing Alisdair MacIntyre’s earlier work, After Virtue: A Study in Moral Theory (1981), set in the context of Iris Murdoch and Elizabeth Anscombe, the modern initiators of a virtue ethic. This “philosophical” source gives the theoretical framework that addresses the question of moral formation. It is therefore entitled: A philosophical analysis: The rise of virtue ethics as alternative ethical theory. The third chapter is devoted to two related “wisdom” themes: Firstly, the seven traditional virtues are briefly described highlighting the virtue of wisdom as foundational. Secondly, the idea of wisdom is further developed via three wisdom traditions, namely: wisdom in the Hellenistic, Judeo-Christian and African traditions. This “sapiential” source gives this African theology of wisdom its most important building blocks. This chapter is therefore entitled: A sapiential analysis: Wisdom as foundation for virtue ethics in Africa. The last chapter brings the previous sources together under a specific theological perspective. It draws on aspects of recent African theologians’ work, notably: Kwame Gyekye and Benezet Bujo who engage with and bring together Western and African theological traditions. I answer a pertinent question, “What does such a ‘theological’ perspective entail?” I draw on Scripture and its Trinitarian tradition to demonstrate how African wisdom, reinforced by the framework of virtue theory, and developed in the context of present-day Africa by an African student of theology, has the potential to contribute to the moral transformation of Africa. This more overt “theological” source is the distinctive Christian enterprise of an African wisdom theology. The chapter title is aligned with the overall title of this study: A theological analysis: Toward an African virtue ethics? To this end, this study achieves its attempt to construct an inter-related framework from which an African theology of wisdom may emerge.
- Full Text:
- Date Issued: 2005
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