Contribution to the valorisation of carbonates manganese Ores in ferromanganese industry

Abstract: The energy consumption in the ferroalloys industry has become an enormous challenge as the cost is increasing while the quality of the raw materials is not changing to compensate the lowering of the quality. It has become important to look at the use of valorising low quality raw materials and its implication on the energy consumption as well as the quality of the metal. The current study investigate and contributes to the valorisation of the low quality manganese raw materials namely carbonates manganese ores

What are the critical issues arising from the SADC trade integration process?

This policy brief is a shortened version of the following paper: Overview of Trade Relations in SADC: Some Empirical Observations by Paul Kalenga

Regional Trade Integration in Southern Africa: Critical Policy Issues

The aim of this paper is to highlight key issues arising from regional trade integration in the Southern African Development Community (SADC) as well as the concomitant policies required to facilitate the trade process. The paper highlights issues pertaining to distribution effects arising from integrating unequal partners and the need for open trade policies in order to realise potential positive spillovers

What are the major trends and determinants of foreign direct investment in SADC countries?

This policy brief is a shortened version of the following paper: Foreign Direct Investment in Sub-Saharan Africa by Paul Kalenga

Synthesis and characterization of copper chalcogenide nanoparticles and their use in solution processed photovoltaics

A Thesis submitted to the Faculty of Science, School of Chemistry at University of the Witwatersrand, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg 2015Photovoltaic cells offer a good alternative to the fossil fuels. Several approaches are being analysed in order to have solar cells that are capable to conquer the energy market all around the world. Quantum dots (QDs) have already proven features that can be taken into account to improve the properties of solar cells. Metal selenide nanoparticles (NPs) possess semiconducting behaviours that can vary with their structural and optical properties evolving from their synthesis. The reaction parameters such as the method, time, solvent and precursors can affect the growth and nucleation of particles and thus impose on the properties of the synthesized materials. The performance of solar cells made of the synthesized metal selenides will then be dependent upon the properties of the NPs used as active layer. Furthermore, the electrical current generation also depends on the structure of the deposited active layer and its interface with other films to be assembled for the device. The binary copper selenide, ternary copper indium selenide (CISe), quaternary copper indium gallium selenide (CIGSe) and quinary copper zinc tin sulphur selenide (CZTSSe) NPs were synthesized via conventional colloidal method (CCM) and microwave assisted method (MAM). The MAM has a particular interest as it is less time consuming and can easily be a large scale synthesis. Photovoltaic devices were fabricated from the synthesized materials as proof of concept for photovoltaic activities. The CCM was used to optimize various parameters for the synthesis of each type of the chalcogenide materials as this is easily controllable than the ones from the sealed vessel from MAM. The dependency of properties of all copper chalcogenide NPs on the time, precursor concentration, temperature and solvent of synthesis have been demonstrated via various characterization techniques including ultraviolet-visible-near infrared spectroscopy, photoluminescence spectroscopy, X-ray diffractometry and transmission electron microscopy. The binary copper selenide was first synthesized and considered as a template for evaluation of the use of copper chalcogenide materials in solar cells. Relatively smaller copper selenide NPs with average sizes of 4.5 and 6.0 nm were obtained from conventional colloidal and microwave assisted methods respectively. The sample yielded from the microwave assisted method possessed less polydispersed NPs. The later had better crystallinity in which prevailed a single cubic Cu2Se phase. To the best of our knowledge this is the first evidence of defined shapes and nearly single phase of small sized copper selenide NPs synthesized by mean of the MAM. The copper selenide particles synthesized via this method were used to fabricate a Schottky device. The conditions of copper selenide synthesis were optimized to 250 oC, 30 iii min of CCM synthesis using oleylamine (OLA) and a Cu/Se ratio of 1:1. Nearly hexagonal facets with blue-shifted absorption band edge of monodispersed NPs sizing 4-8 nm in diameter were obtained. The synthesized copper selenide showed better crystallinity with a single cubic Cu2Se phase. A Schottky device using MAM synthesized copper selenide NPs as the semiconducting layer was fabricated at room temperature. The diode effect was demonstrated with the electrical parameters such as the ideality factor, barrier height and the series resistances extracted from the experimental current-voltage data using the thermionic theory and Cheung’s modification. The thermionic theory resulted in the ideality factor of 4.35 and the barrier height of 0.895 eV whilst the Cheung’s method resulted in the ideality factor, barrier height and series resistance of 1.04, 2.59 10-3 eV and 0.870 Ω respectively. The ternary copper indium selenide NPs showed that the MAM allowed the formation of copper rich NPs alongside secondary products. The synthesis of the ternary sample via CCM was optimized using uncapped precursors (no TOP was added) in OLA at 220 oC for 30 min. The synthesized CuInSe2 NPs possessed a large blue-shift in their absorption band edges and emission peaks. The nearly stoichiometric CuInSe2 particles with diameter sizes of 5-9 nm were found in tetragonal crystalline orientation. The cyclic voltametry (CV) and the absorption spectra showed a large blue-shifted energy gap, about 0.95 eV, an increase from the bulk, proving the quantum confinement effects of synthesized copper indium selenide quantum dots. The CuInSe2 NPs were thus used as absorbing materials in the quantum dot sensitized solar cell devices (QDSSCs). The QDSSC devices were assembled via treatment of the titanium oxide, quantum dot layers and their interface. This was done by the treatment of copper indium selenide surface with mercapto-propionic acid (MPA) and ethanedithiol (EDT) during the deposition of the quantum dots onto TiO2 films. The MPA treatment did not reveal positive effects on copper indium selenide thin film and the assembled device under our optimized working conditions. However the use of EDT allowed the improvement of electron transport. The short circuit current (Jsc), open circuit voltage (Voc) and fill factor (FF) obtained from the current-voltage (J-V) curves reached the values of 324 μA cm-2, 487 mV and 43% respectively, indicating that the investigated quantum dots possess electrical properties. For the quaternary copper indium gallium selenide, relatively small sized NPs were synthesized via CCM and MAM. The CCM synthesized CIGSe NPs were less agglomerated iv with a shorter tailing in absorption than those from MAM. The stoichiometric CuIn0.75Ga0.25Se2 showed less agglomerated and highly crystalline particles with a large blueshifted absorption band edge and a smaller full width at halth maximum (FWHM) of the emission peak compared to CuIn0.5Ga0.5Se2 and CuIn0.25Ga0.75Se2. The use of OLA as solvent of synthesis improved the growth and dispersivity of copper indium gallium selenide NPs. The particles with a large blue-shifted absorption band edge, a lattice of tetragonal phase, more monodispersed CIGSe and possessing an average size of 6.5 nm were obtained from CCM synthesis using OLA. The OLA as-synthesized CIGSe NPs were used in thin film for the assembly of QDSSC. The device exhibited electrical properties with the Jsc, Voc and FF of 168 μA cm-2, 162 mV and 33% respectively. The overall device performance was poor but may further be improved for further photovoltaic application. The quinary CZTSSe NPs possessed large blue-shifted absorption band edges of 450-460 nm than the bulk material (827 nm). The emission peak at 532 nm and similar FWHM of less than 50 nm were observed in samples from both CCM and MAM. More monodispersed crystals were obtained with both methods whilst the average particle sizes of 10 and 9 nm were yielded from MAM and CCM respectively. The nanoparticles crystallized in tetragonal lattices between copper zinc tin sulphide and copper zinc tin selenide crystals. However, the MAM gave more crystalline phases. The CV and the absorption spectra showed a blue shifted energy gap, about 0.21 eV increase from the buk which is located at 1.51 eV. This is indicative of the quantum confinement effects of synthesized NPs. The evidence of electrical properties was also shown in the QDSSCs fabricated using the MAM synthesized quinary QDs. This was done following the same treatments as for copper indium selenide devices. The Jsc, Voc and FF were found at the maxima of 258 μA cm-2, 395 mV and 38% respectively. The MPA and EDT treatments did not improve the device performance under our working conditions. Nevertheless, the electrical properties observed in the assembled device were indicative of promising efficient solar cells from synthesized CZTSSe NPs

The Good, the Bad, the Marginal: respiratory management of <29 weeks infants according to subjective assessment of perinatal adaptation.

Background Even if a primary CPAP strategy gives benefits in extremely preterm infants, many still require intubation at birth. Half of those initially managed with primary CPAP will require further support: surfactant administration or mechanical ventilation. Those infants have increased risks of death and neonatal morbidities, and will require longer duration of respiratory support. Identifying them early, during the birth stabilization process, might lead to improvements in respiratory care. A subjective classification of perinatal adaptation as Good, Bad or Marginal has been suggested but requires further evaluation. We aimed to evaluate respiratory management according to perinatal adaptation. Methods Premature infants of less than 29 weeks and admitted between 01/2013 and 07/2014 were retrospectively studied. Neonatal database and discharge summaries provided neonatal care and outcome data. Good perinatal adaptation (GPA) was considered for infants with good respiratory drive, tone and low oxygen requirement in the delivery room. Infants with marginal (M) PA had intermittent respiratory drive, normocardia with ventilation, and decreasing FiO2. Bad (B) PA is considered with hypotonia, bradycardia, apnea and high FiO2. Data are presented as mean +/- SD, median (interquartile range) or incidence and analyzed with ANOVA, Kuskal-Wallis test or Chi2. Results Sixteen infants had GPA, 19 MPA and 23 BPA. GA was 26 4/7 wk (24-28) and BW was 885 187g. Risk factors for bad adaptation are (NS) male gender, lower GA, and no complete antenatal steroid exposure. Apgar at 1 min. increases with better PA [B3 (2-5); M6 (3-7) and G8 (7-8)*] (*p<.05 vs B & M), and improves at 5 min.: [B7 (6-7); M7 (6-8); G 9 (8-9)*]. Risk of intubation at birth is associated with poorer adaptation (B 87%; M 47%; G 12%, p<.01) Primary CPAP success was not different according to group (B 3/3; M66%; G56%). Surfactant while on CPAP (LISA method) was given to 11/16 patients, including 7 delivery room administrations. If intubated by day 3, duration of first invasive ventilation was shorter (NS) for GPA (9h) [MPA (15h), BPA (29h)]. Early neonatal death tended to decrease with better PA: 26%, 16% and 0% (p=.08). There is no difference in BPD -36 wk (B 19%, M13%, G 12%). Conclusions Infants with better perinatal adaptation have increased chances of being initially managed with CPAP. Primary CPAP success may be improved with less invasive surfactant therapy. Outside of the delivery room, perinatal adaptation assessment tends to identify risk of early neonatal death, but is not predictive of respiratory outcomes

National policies and regional integration in the South African Development Community

This paper focuses on the relationship between regional integration in the Southern African Development Community and national policies. Review of trade, industrial, agricultural, labour, and related policy areas, indicates that national policies can and do run counter to the regional integration initiatives that are formalized in the legal instruments of this southern African regional economic community

Investigation into the influence of magnesia content, alumina content, basicity and ignition temperature on the mineralogy and properties of iron sinter

The sinter quality is dependent on sinter mineralogy, which in turn depends on the chemical compositions of the sinter mix. Although many research works have been conducted, further investigation on the effect of chemical compositions (MgO, A2O3, Basicity) on the sinter quality is still required for further improvement of the sinter and more alternative additives are still being tested. In this project, a sinter pot has been used to manufacture sinters, which were characterized using point-counting to quantify the different phases and X-Ray diffraction to identify the polymorphic forms of Ca2SiO4 of the silicate phases. The produced sinters were evaluated with respect to reducibility index (RI), reduction degradation index (RDI), physical breakdown (TI and AI), and production properties (yield, coke breeze rate and production rate). The influence of ignition temperature, magnesium oxide, alumina addition and basicity on the mineralogy as well as physical and chemical properties of iron ore sinters were investigated. Results were obtained as follows: For the Base case with a basicity of 2, 2.8 mass% MgO content, 1.7 mass % Al2O3 and 10 mass% CaO, the effect of ignition temperature, which ranged between 864oC and 1100oC, on the sinter quality was investigated. Results showed that the ignition temperature had an effect on the sinter properties: reducibility (RI), physical strength (TI and AI), production properties (yield, coke breeze rate and production rate). The temperature 1053oC was the best ignition temperature for an economically acceptable sinter. A further increase in ignition temperature was found to form melt on the surface of the sinter produced, leading to a sinter of low quality. Also, X-rays diffraction pattern showed that the allotropic transformation of the Ca2SiO4did not take place. The Low SiO2– Low Al2O3 sinter had the highest reducibility index and had the highest Abrasion index and the lowest coke breeze rate at 2.8 mass% MgO content compared to all the sinters produced in this project. For the High SiO2 – Low Al2O3 sinter MgO was added through dolomite and fused magnesia. A comparative study on the effect of dolomite and fused magnesia was conducted. The sinter to which fused magnesia was added had lower reducibility, higher reduction degradation, higher tumble index, lower abrasion index and lower coke breeze rate than the sinter to which dolomite was added. High SiO2 – High Al2O3 sinter had the lowest reducibility index, the lowest reduction degradation, the lowest tumbler index and the highest coke breeze rate. The increase in MgO content in all the sinters produced increased the coke breeze rate.Dissertation (MSc)--University of Pretoria, 2008.Materials Science and Metallurgical Engineeringunrestricte

Producing Fabulous : Commodification and Ethnicity in Hair Braiding Salons

Black women wearing fabulous braids are a striking feature of the Afro-diasporic cultural landscape. However, the braiders and salon owners who enable this aesthetic engineering are seldom acknowledged. This dissertation investigates the experience and role of Caribbean and West and Central African women in the hair braiding industry, a rapidly growing business in the U.S. I address the complexity of these women’s multiple social roles and the multiple consciousness (King, 1988) associated with their demographic characteristics (color, ethnicity, gender, nationality, and immigrant status). The commonalities between the braiders and their mostly African American customers contrast vividly with their perception of one another as a cultural group and as business counterparts. This dissertation examines the aforementioned contrasts, and thereby enters the debate of the definition and significance of gendered blackness/racialized gender, when ethnicity transcends race. Late-20th and 21st century trans-diasporic migrations (especially the movement of Africans to and from Europe and the U.S.) have changed the make-up of the black diaspora and, consequently, what it means to be black in the modern world. As I discuss ethnicity as a for-profit construct in the U.S. and Jamaican political economy, I also propose a re-visited definition of Africanness, adjusted to the contemporary make-up of the African diaspora. In addition, I evaluate the label “African Hair Braiding” that features in numerous salons’ names by inspecting the “African” element in the service they render. The resulting dissertation reports and analyzes participant observation narratives, field notes, and interviews with owners, braiders, and customers in Queens (NY) and Baton Rouge (LA). I also examine the hair braiding market as both product and agent of globalization, shedding light on the contribution of these workers – a contribution that is often taken for granted, underestimated, underappreciated, ignored, or simply unheard of