Ferrochrome (FeCr) is a crude alloy containing chromium (Cr) and iron (Fe). FeCr is mainly used for the production of stainless steel, which is an important modern-day alloy. FeCr is produced from chromite ore through various smelting methods. In this study, the focus was on the pelletised chromite pre-reduction process, which is also referred to as the solid state reduction of chromite. In this process, fine chromite ore, a clay binder and a carbon reductant are dry milled, agglomerated (pelletised) and pre-reduced (solid state reduction) in a rotary kiln. The pre-reduced pellets are then charged hot, immediately after exiting the rotary kiln, into a closed submerged arc furnace (SAF). This production process option has the lowest specific energy consumption (SEC), i.e. MWh/ton FeCr produced, of all the FeCr production processes that are commercially applied. Other advantages associated with the application of the pelletised chromite pre-reduction process are that it eliminates the use of chromite fines, has a high Cr recovery, and produces low sulphur- (S) and silicon (Si)-containing FeCr. The main disadvantage of the pelletised chromite pre-reduction process is that it requires extensive metallurgical control due to the variances in the levels of pre-reduction achieved and carbon content of the pre-reduced pelletised furnace feed material. This implies that the metallurgical carbon balance has to be changed regularly to prevent the process from becoming carbon deficient (also referred to as ‘under coke’) or over carbon (also referred to as ‘over coke’). The analytical technique currently applied to determine the level of chromite pre-reduction is time consuming, making it difficult and expensive to deal with large numbers of samples. In an attempt to develop a technique that would be faster to determine the level of chromite pre-reduction, a new analytical method using a combination of scanning electron microscopy (SEM), image processing and computational techniques was investigated in this study. Metallurgical grade chromite (<1 mm), anthracite breeze (<1 mm), and fine FeCr (<1 mm) that were used to prepare pellets in the laboratory, as well as industrially produced pre-reduced pellets that had already been milled in preparation for the determination of the pre-reduction level with wet chemical analysis were received from a large South African FeCr producer. These laboratory prepared pellets and the industrially produced pellet mixtures were considered in this investigation. Samples were moulded in resin and polished in order to obtain SEM micrographs of the polished cross sections. Elements with higher molecular weights are indicated by lighter greyscale, while elements with lower molecular weights are indicated by darker greyscale in SEM micrographs. This basic principle was applied in the development of the new analytical technique to determine the level of chromite pre-reduction, with the hypothesis that the pixel count of white pixels (representing metallised particles), divided by the combined pixel count of white (representing metallised particles) and grey (representing chromite particles) pixels would be directly related to the level of chromite pre-reduction determined with the current wet chemical method. This hypothesis can be mathematically expressed as: The newly-developed analytical method was validated by correlating the white pixel% calculated with the chromite pre-reduction levels (%) determined with wet chemical analysis of laboratory prepared and industrially produced pellet mixtures, which had R2 values of 0.998 and 0.919, respectively. This suggests that the method can be used to determine chromite pre-reduction accurately. / MSc (Engineering Sciences in Chemical Engineering), North-West University, Potchefstroom Campus, 2015

Ferrochrome (FeCr) is a crude alloy containing chromium (Cr) and iron (Fe). FeCr is mainly used for the production of stainless steel, which is an important modern-day alloy. FeCr is produced from chromite ore through various smelting methods. In this study, the focus was on the pelletised chromite pre-reduction process, which is also referred to as the solid state reduction of chromite. In this process, fine chromite ore, a clay binder and a carbon reductant are dry milled, agglomerated (pelletised) and pre-reduced (solid state reduction) in a rotary kiln. The pre-reduced pellets are then charged hot, immediately after exiting the rotary kiln, into a closed submerged arc furnace (SAF). This production process option has the lowest specific energy consumption (SEC), i.e. MWh/ton FeCr produced, of all the FeCr production processes that are commercially applied. Other advantages associated with the application of the pelletised chromite pre-reduction process are that it eliminates the use of chromite fines, has a high Cr recovery, and produces low sulphur- (S) and silicon (Si)-containing FeCr. The main disadvantage of the pelletised chromite pre-reduction process is that it requires extensive metallurgical control due to the variances in the levels of pre-reduction achieved and carbon content of the pre-reduced pelletised furnace feed material. This implies that the metallurgical carbon balance has to be changed regularly to prevent the process from becoming carbon deficient (also referred to as ‘under coke’) or over carbon (also referred to as ‘over coke’). The analytical technique currently applied to determine the level of chromite pre-reduction is time consuming, making it difficult and expensive to deal with large numbers of samples. In an attempt to develop a technique that would be faster to determine the level of chromite pre-reduction, a new analytical method using a combination of scanning electron microscopy (SEM), image processing and computational techniques was investigated in this study. Metallurgical grade chromite (<1 mm), anthracite breeze (<1 mm), and fine FeCr (<1 mm) that were used to prepare pellets in the laboratory, as well as industrially produced pre-reduced pellets that had already been milled in preparation for the determination of the pre-reduction level with wet chemical analysis were received from a large South African FeCr producer. These laboratory prepared pellets and the industrially produced pellet mixtures were considered in this investigation. Samples were moulded in resin and polished in order to obtain SEM micrographs of the polished cross sections. Elements with higher molecular weights are indicated by lighter greyscale, while elements with lower molecular weights are indicated by darker greyscale in SEM micrographs. This basic principle was applied in the development of the new analytical technique to determine the level of chromite pre-reduction, with the hypothesis that the pixel count of white pixels (representing metallised particles), divided by the combined pixel count of white (representing metallised particles) and grey (representing chromite particles) pixels would be directly related to the level of chromite pre-reduction determined with the current wet chemical method. This hypothesis can be mathematically expressed as: The newly-developed analytical method was validated by correlating the white pixel% calculated with the chromite pre-reduction levels (%) determined with wet chemical analysis of laboratory prepared and industrially produced pellet mixtures, which had R2 values of 0.998 and 0.919, respectively. This suggests that the method can be used to determine chromite pre-reduction accurately. / MSc (Engineering Sciences in Chemical Engineering), North-West University, Potchefstroom Campus, 2015

Copper-alumina composites were developed for testing in abrasive wear applications. The composites featured a porous continuous ceramic-preform network infiltrated by a liquid metal to form the final consolidated composite. The liquid metal phase was pure copper. Six different ceramic preform variants were tested. Ceramic volume fractions of 40, 50 and 60% were used, of two preform types; one pure-alumina, and one with additional 2wt% copper(I) oxide (CU20), functioning as an infiltration aid, the effects of which were determined in a previous study; the copper-oxide reduced infiltration pressure and allowed the use of higher ceramic phase volume fraction in the final composite. Abrasive wear tests against two automotive braking system materials were conducted. Grey cast iron of alloy type GG15 was used to establish a baseline for behaviour of the six different composite samples and compare them. Following this, the three volume fraction variants of samples using the copper-oxide infiltration aid were trialled against a commercially-available European passenger vehicle brake pad friction material; ABEX 6091. Wear tests were conducted on a pin-on-disc tribometer. Hemispherical-headed pins were made from the composite and tested against rotating discs of the grey cast iron and the ABEX friction material. Contact velocity was kept constant at Ims-?? at room temperature in air, and contact loads up to 15N were used. Test loads of 1-4N were used against grey cast iron, and 15N against the ABEX friction material. Optical micrography was used to monitor the wear rate of samples tested against grey cast iron. Scanning electron microscopy (SEM) was used to characterise bulk microstructures and evaluate surface wear features. Transmission electron microscopy (TEM) was used for further microstructural investigation of the sintering and interfacial features of the undamaged pin samples, as well as damage zones and tribofilm compositions. Focussed ion beam (FIB) milling was used to create subsurface cross-sections of wear regions and prepare TEM samples. The wear performance of the different sample types was compared by ceramic content and preform additives. It was found that the wear resistance of pure-alumina preform composites was dependent on ceramic volume fraction. Increasing ceramic content lead to increased wear resistance. The lower sinter temperature of the samples with the copper oxide additive led to reduced wear resistance compared with the monolithic alumina preforms and changes in ceramic volume fractions were not discernable in wear resistance against grey cast iron. This could be further supported by qualitative micrographic observations. All tests against grey cast iron were dominated by tribochemical film formation, which was determined to be oxidation of the iron which formed at the composite pin contact surface. Further testing of the copper-oxide containing samples against the ABEX friction material revealed a mixed result; the 50 and 60% ceramic volume samples produced near-identical wear performance, while the 40% sample suffered poor wear resistance. The dominant wear mechanism of composite pins tested against the ABEX friction material was abrasive wear. Sub-surface analysis of wear pins revealed a prominent damage layer forming at the contact surface of all pin samples which progressively grew into the bulk material. This layer was believed to have an important effect on the wear behaviour of the materials.

Copper-alumina composites were developed for testing in abrasive wear applications. The composites featured a porous continuous ceramic-preform network infiltrated by a liquid metal to form the final consolidated composite. The liquid metal phase was pure copper. Six different ceramic preform variants were tested. Ceramic volume fractions of 40, 50 and 60% were used, of two preform types; one pure-alumina, and one with additional 2wt% copper(I) oxide (CU20), functioning as an infiltration aid, the effects of which were determined in a previous study; the copper-oxide reduced infiltration pressure and allowed the use of higher ceramic phase volume fraction in the final composite. Abrasive wear tests against two automotive braking system materials were conducted. Grey cast iron of alloy type GG15 was used to establish a baseline for behaviour of the six different composite samples and compare them. Following this, the three volume fraction variants of samples using the copper-oxide infiltration aid were trialled against a commercially-available European passenger vehicle brake pad friction material; ABEX 6091. Wear tests were conducted on a pin-on-disc tribometer. Hemispherical-headed pins were made from the composite and tested against rotating discs of the grey cast iron and the ABEX friction material. Contact velocity was kept constant at Ims-?? at room temperature in air, and contact loads up to 15N were used. Test loads of 1-4N were used against grey cast iron, and 15N against the ABEX friction material. Optical micrography was used to monitor the wear rate of samples tested against grey cast iron. Scanning electron microscopy (SEM) was used to characterise bulk microstructures and evaluate surface wear features. Transmission electron microscopy (TEM) was used for further microstructural investigation of the sintering and interfacial features of the undamaged pin samples, as well as damage zones and tribofilm compositions. Focussed ion beam (FIB) milling was used to create subsurface cross-sections of wear regions and prepare TEM samples. The wear performance of the different sample types was compared by ceramic content and preform additives. It was found that the wear resistance of pure-alumina preform composites was dependent on ceramic volume fraction. Increasing ceramic content lead to increased wear resistance. The lower sinter temperature of the samples with the copper oxide additive led to reduced wear resistance compared with the monolithic alumina preforms and changes in ceramic volume fractions were not discernable in wear resistance against grey cast iron. This could be further supported by qualitative micrographic observations. All tests against grey cast iron were dominated by tribochemical film formation, which was determined to be oxidation of the iron which formed at the composite pin contact surface. Further testing of the copper-oxide containing samples against the ABEX friction material revealed a mixed result; the 50 and 60% ceramic volume samples produced near-identical wear performance, while the 40% sample suffered poor wear resistance. The dominant wear mechanism of composite pins tested against the ABEX friction material was abrasive wear. Sub-surface analysis of wear pins revealed a prominent damage layer forming at the contact surface of all pin samples which progressively grew into the bulk material. This layer was believed to have an important effect on the wear behaviour of the materials.

Magister Pharmaceuticae - MPharm / The aim of this study was to investigate the mechanism of fenfluramine-induced pulmonary phospholipidosis, by comparing the profile and levels of induced phospholipids in the rat and the mode of phospholipase inactivation, both relative to that produced by chlorphentermine. Wistar and BD9 rats were injected with fenfluramine (FF) and chlorphentermine (CP) intra-peritoneally daily over a six week period to induce phospholipidosis. The lungs isolated from such treated and untreated animals, were grouped into unlavaged lungs and lungs to be lavaged and from the latter group the alveolar macrophages were isolated. Small sections of the unlavaged lungs were microscopically examined to verify the induction of phospholipidosis. Further the levels of phosphatidyl choline (PC), spingomyelin (SPM), phosphatidyl ethanolamine (PE), phosphatidyl glycerol (PG), phosphatidyl inositol (PI), phosphatidyl serine (PS) and phosphatidic acid (PA) were determined in both groups of lungs using a TLC method. To assess whether the drug-mediated inactivation of the phospholipases (PL) occurred via direct inhibition of the enzymes or via the drug-phospholipid complex, the hydrolysis of the above phospholipids by PL-A or PL-C were monitored using colorimetric methods. The feasibility of the phospholipid-drug complex-mediated mechanism was further explored, by assessing the effect the two drugs had on the phase transition temperature of the phospholipids. Electron microscopy revealed the presence of hypertrophied and elevated counts of alveolar macrophages in the treated-Wistar and -BD9 rats. In the FF- and CP treated Wistar and BD9 rats there were, compared to the saline-treated rats, a 200 % and 235 % increase in macrophage counts, respectively, for the FF-treated rats and a 700 % and 965 % increase in macrophage counts, respectively, for the CP treated rats. The levels of all the phospholipids in the unlavaged lungs of both rat strains were elevated, except that for PG, PS and PA. In both rat strains following the treatment with both drugs the PG levels were not elevated and the PS levels were not elevated following CP treatment. Following the treatment for both drugs, the PA levels were also not elevated in the BD9 rats. Relative to the levels found in the unlavaged lungs of the control rats, the increases ranged from a minimum of 9 to a maximum of 216 %. In general, Wistar rats appeared to be more susceptible to both FF and CP treatment. In both rat strains, lavaging of the lungs considerably reduced the levels of phospholipids remaining in the lung and the differences between the treated and untreated animals became less striking. The addition of FF or CP, whether directly to the enzyme, or in the form of the drug phospholipid complex, resulted in significant decreases in the PL-A-mediated or PL-C-mediated hydrolysis of virtualy all the test phospholipids. The average decrease ranged from 0.811 to 4.04 ,.,.FFAbbb ,.,.1-1sample min-I, for the PL-A activity and 0.023 to 0.827 ,.,.gIp'CC100 ,.,.1-1 sample min-I, for the PL-C activity. In the case of FF, the inhibition of PL-A activity could not be ascribed exclusively to either direct inhibition of the enzyme or reduced susceptibility of the phospholipid substrate-drug complex. The PL-C activity appeared to be inhibited to a greater extent via the phospholipid substrate-drug complex rather than by direct inhibition. On the other hand, CP induced a small, but significantly greater degree of inhibition of PL-A activity, more via direct inhibition, rather than by the phospholipid substrate-drug complex. The PL-C activity appeared to be inhibited to a greater extent via phospholipid substrate-drug complexation than by direct inhibition. From the above data, considered collectively, it was not possible to declare either of the two possible mechanisms as the more likely one for FF or CP-induced inhibition of the phospholipases. The feasibility of the indirect mode was further explored, by determining the phase transition temperatures for the phospholipid-drug complexes of each drug. The addition of each drug caused a depression of the phase transition temperature of all the phospholipids with a .1T'dd ranging from 0.52 to 15.73 °C. This appears to support the notion that both drugs bind to the phospholipids and the differences in the extent of the phase transition temperature depression of the individual phospholipids may indicate differences in the binding capacities of these drugs. The following major conclusions may be drawn from the results of this investigation. Fenfluramine induces a phospholipidosis syndrome in the lungs of Wistar and BD9 rats that are histologically similar to that induced by CP. It induces the elevation of essentially the same phospholipids as CP, primarily in the alveolar spaces and macrophages, and by implication, most likely via similar mechanisms. For both FF and CP, both direct inhibition and phospholipid-drug complex-mediated inhibition of phospholipases were found to be a viable mechanism for this syndrome. The mechanism for FF-induced pulmonary phospholipidosis thus appears to be similar to that of CP; small quantitative differences in essentially similar mechanisms, may explain the differences in the levels of induced phospholipidosis found in this study.

It has long been known that chronic exposures to high concentrations of respirable coal mine dust can lead to the development of lung diseases such as Coal Worker's Pneumoconiosis, commonly referred to as "black lung", and silicosis. Since the mid-1990s, an alarming resurgence of diseases has been documented in central Appalachia, where underground mining often necessitates significant extraction of rock strata along with the thin seams of coal. These circumstances have prompted concern over if or how changing dust composition might be a factor in contemporary disease prevalence. Until now, the total mass concentration and quartz mass fraction of respirable dust have been regulated and monitored in US coal mines. Unfortunately, however, these two metrics alone do not paint a full picture of dust composition. Earlier work in the author's research group established a preliminary thermogravimetric analysis (TGA) method for coal mine dust. The method is intended to allow estimation of three key mass fractions of the dust from separate sources: coal from the coal strata being mined; non-carbonate minerals from the rock strata being mined or drilled; and carbonates that are primarly sourced from application of rock dust products to the mine floor or ribs. However, accuracy of the preliminary method was substantially limited by poor dust recovery from the fibrous filter media used for sample collection. This thesis includes two studies: The first study aims to establish an improved TGA method. It uses smooth polycarbonate (PC) filters for dust sampling and a modified thermal ramping routine. The method is verified using laboratory-generated respirable dust samples. In the second study, the improved TGA method is used to analyze 75 respirable mine dust samples, collected in 15 US mines. Replicate samples are also analyzed by scanning electron microscopy using energy dispersive X-ray (SEM-EDX). TGA and SEM-EDX results are compared to gain insights regarding the analytical methods and general trends in dust composition within and between mines. / Master of Science / It has long been known that chronic exposures to excessive respirable coal mine dust can lead to the development of lung diseases such as Coal Worker’s Pneumoconiosis (“Black Lung”) and silicosis. Disease rates in central Appalachia have shown an alarming and unexpected increase since the mid-1990s, despite declining dust concentrations evident from regulatory compliance monitoring data. Clearly, there is a need to better understand coal mine dust composition, which will require additional analytical methods. Thermogravimetric analysis (TGA) has been proposed as one possible method, because it should allow estimation of three key dust components from separate sources: coal from the coal strata being mined; non-carbonate minerals from the rock strata being mined or drilled; and carbonates from application of rock dust products to the mine floor and ribs. However, preliminary work with TGA showed limited accuracy, mostly due to sampling materials. In this thesis, two studies were performed. The first study aims to establish an improved TGA method using smooth, polycarbonate (PC) filters. The second study demonstrates the method on a large number of mine dust samples, and compares the results to those gained by an alternative method that uses electron microscopy.

<p> <p>&nbsp / </p> <p align="left">&nbsp / </p> <p>&nbsp / </p> </p> <p align="left">The aim of this study was to produce useful composite materials from fly ash, a major waste product of coal combustion from power plants. Polyaniline-fly ash (PANI-FA) composites were prepared by in situ polymerisation of aniline in the presence of Fly Ash (FA) by two slightly different methods. In one case polystyrene sulphonic acid (PSSA) was used as a stabilizer and in another case the starting materials (aniline and FA) were aged before oxidation. The aging procedure formed nanotubes that have cross-sectional diameters of 50-110 nm. The other procedure produced nanotubes with a diameter of 100-500 nm and the length of up to 10&mu / m. The presence of metal oxides and silica in FA were responsible for the formation of nanorods in PANI-PSSA-FA.. The formation of the composites was confirmed by UV-Vis and FTIR. The UV-Vis showed maximum absorbance at 330-360 nm ( due to &pi / -&pi / * transition of benzoid rings) and 600-650 nm(due to charge transfer excitons of quinoid rings), which are characteristics of emaraldine base. The electrochemical analysis of the composites showed that the composites were conductive and electroactive. The Cyclic Voltammetry of PANI-PSSA-FA showed three redox couples which are characteristics of sulphonated PANI. The morphology of the composites was studied by Scanning Electron Microscopy (SEM) and showed that our methods gave composites with improved homogeneity as compared to other reported methods. Thermo Gravimetric analysis (TGA) showed that the presence of FA in the composites improves the thermal stability of the composites by up to 100 0C.<br /> &nbsp / </p>

The main objective of this study was to determine the effects of batters containing various flour types and frying methods on physical and chemical properties of chicken fingers. To determine the effects of different flour types, 30 % of the corn and wheat flour mix in control batter was replaced with chickpea, rice or soy flours. Frying was performed in microwave oven at 365 W (70 %) power level and at 180&amp / #61617 / 1&deg / C for different times. Samples were also fried in a conventional fryer at 180&amp / #61617 / 1&deg / C for comparison. The properties that were measured were coating pick-up and moisture content, oil content, color, hardness, porosity and acrylamide content of fried samples. In addition, microstructural analysis of batters and temperature distribution of fried samples during cooling were performed. Moisture content of chicken fingers decreased whereas the darkness, porosity and hardness of samples increased with increasing microwave frying time. Using microwaves decreased frying time by 70 %. Samples fried for 1.5 min using microwave provided similar moisture and oil contents in the coating part as compared to conventionally fried ones for 5min. However, the chicken part of microwave fried sample had lower moisture content. Lighter colored samples with higher porosity and lower hardness values were obtained with microwave frying. In microwave frying, soy flour addition to batter formulation decreased the moisture loss and oil absorption as compared to control by 19.3% and 20.7%, respectively. The lowest hardness, the highest porosity and oil content were obtained with the addition of chickpea flour. Flour type was not found to be effective on acrylamide content. Microwave frying provided lower acrylamide content as compared to those fried conventionally for all types of flours. The reduction in acrylamide level was the highest (34.5%) for rice flour containing batter. Color parameters of chicken fingers were not found to be a reliable indicator of acrylamide levels. Different types of frying method and flours used in batter formulation resulted in differences in the microstructure of fried batter. Variations in internal temperature distribution during cooling increased with frying time in both microwave and conventional frying. The sample fried in microwave oven for 1.5 min had a more nonuniform temperature distribution.

<p> <p>&nbsp / </p> <p align="left">&nbsp / </p> <p>&nbsp / </p> </p> <p align="left">The aim of this study was to produce useful composite materials from fly ash, a major waste product of coal combustion from power plants. Polyaniline-fly ash (PANI-FA) composites were prepared by in situ polymerisation of aniline in the presence of Fly Ash (FA) by two slightly different methods. In one case polystyrene sulphonic acid (PSSA) was used as a stabilizer and in another case the starting materials (aniline and FA) were aged before oxidation. The aging procedure formed nanotubes that have cross-sectional diameters of 50-110 nm. The other procedure produced nanotubes with a diameter of 100-500 nm and the length of up to 10&mu / m. The presence of metal oxides and silica in FA were responsible for the formation of nanorods in PANI-PSSA-FA.. The formation of the composites was confirmed by UV-Vis and FTIR. The UV-Vis showed maximum absorbance at 330-360 nm ( due to &pi / -&pi / * transition of benzoid rings) and 600-650 nm(due to charge transfer excitons of quinoid rings), which are characteristics of emaraldine base. The electrochemical analysis of the composites showed that the composites were conductive and electroactive. The Cyclic Voltammetry of PANI-PSSA-FA showed three redox couples which are characteristics of sulphonated PANI. The morphology of the composites was studied by Scanning Electron Microscopy (SEM) and showed that our methods gave composites with improved homogeneity as compared to other reported methods. Thermo Gravimetric analysis (TGA) showed that the presence of FA in the composites improves the thermal stability of the composites by up to 100 0C.<br /> &nbsp / </p>

Magister Scientiae - MSc / The main hypothesis in this study is the development of a nanocomposite mediated amperometric biosensor for detection of hydrogen peroxide. The aim is to combine the electrochemical properties of both polyaniline and ferrocenium hexafluorophosphate into highly conductive nano composites capable of exhibiting electrochemistry in non acidic media; shuttling electrons between HRP and GCE for biosensor applications. / South Africa