Diversos anodos para célula a combustível de óxido sólido (SOFC) têm sido estudados devido aos problemas de deterioração dos anodos tradicionalmente usados, os compósitos à base de zircônia estabilizada/Ni (YSZ/Ni). Estudos prévios evidenciaram que a perovskita La0,75Sr0,25Cr0,50Mn0,50O3 (LSCM) possui desempenho similar em SOFCs usando hidrogênio e metano como combustível, tornando essa cerâmica um possível substituto dos compósitos à base de níquel. No presente estudo, foram sintetizados compostos La0,75Sr0,25Cr0,50-xMn0,50- yRux,yO3 (LSCM-Ru) pelo método dos precursores poliméricos. Análises termogravimétrica e térmica diferencial (TG/ATD) simultâneas e difração de raios X (DRX) foram utilizadas para monitorar a evolução térmica das resinas precursoras e a formação de fase dos compostos. As propriedades elétricas de amostras sinterizadas foram estudadas pela técnica de 4 pontas de prova dc na faixa de temperatura entre 25 °C e 800 °C. Os resultados experimentais indicaram a formação de fase única dos compostos LSCM-Ru calcinados a ~1200 °C. Os parâmetros de rede, calculados a partir dos dados de DRX, revelaram que a substituição parcial dos íons Cr ou Mn pelo Ru não altera significativamente a estrutura cristalina do LSCM até x,y ~ 0,10; uma característica consistente com os raios iônicos similares dos cátions Cr, Mn e Ru com número de coordenação seis. Medidas de resistividade elétrica ao ar mostraram que o mecanismo de transporte não é alterado e que o efeito da substituição de Ru nas propriedades elétricas do composto depende do íon substituído (Cr ou Mn) de maneira consistente com suas substituições parciais. Os testes de SOFCs unitárias revelaram que células com os anodos constituídos por uma camada coletora de corrente do anodo cerâmico LSCM-Ru e uma camada funcional de YSZ/Ni têm desempenho superior a células contendo apenas o anodo cerâmico. As células contendo os anodos cerâmicos LSCM-Ru foram testadas em hidrogênio e etanol, entre 800 °C e 950 °C, e mostraram desempenho em etanol superior ao em hidrogênio; uma característica que foi associada às propriedades de transporte eletrônico dos compostos LSCM-Ru em atmosfera redutora. Os resultados sugerem que os compostos LSCM com substituição parcial de Ru são anodos promissores para SOFC operando com etanol. / Several anodes for solid oxide fuel cell (SOFC) have been studied because of serious degradation exhibited by the traditionally used yttria-stabilized zirconia/Ni cermets (YSZ/Ni). Previous studies showed that the perovskite La0.75Sr0.25Cr0.50Mn0.50O3 (LSCM) has similar performance in SOFCs running on hydrogen and methane fuels, making such a ceramic a potential alternative to YSZ/Ni cermets. In the present study, compounds La0.75Sr0.25Cr0.50- xMn0.50-yRux,yO3 (LSCM-Ru) were synthesized by the polymeric precursor method. Simultaneous thermogravimetric and differential thermal analysis (TG/DTA) and X-ray diffraction (XRD) were used to monitor the thermal evolution of the precursor resins and the formation of crystalline phases. The electrical properties of sintered samples were studied by the 4-probe dc technique in the temperature range between 25 °C and 800 °C with controlled atmosphere. The experimental results showed the formation of single phase LSCM-Ru compounds after heat treatment at ~ 1200 °C. Lattice parameters, calculated from the XRD data, revealed that the partial substitution of Cr or Mn by Ru has no significant effect on the crystal structure of LSCM up to Ru x,y ~ 0.10; in agreement with the similar ionic radius of Cr, Mn and Ru with coordination number six. Electrical resistivity measurements showed that the transport mechanism is unchanged and that the effect of Ru addition on the electrical properties of the compound depends on the substituted ion (Cr or Mn). Electrochemical tests of SOFCs demonstrated that single cells comprised of a current collector layer of LSCM-Ru ceramic anode and a functional layer for YSZ/Ni have superior performance when compared to single cells with only one layer of the ceramic anode. Single cells with the LSCM-Ru ceramic anode layer were tested under both hydrogen and ethanol fuels, in the 800 °C - 950 °C temperature range. The main results showed that the single fuel cells exhibited higher performance under ethanol than under hydrogen; a feature that was related to the enhanced electronic transport properties of LSCM-Ru in reducing atmosphere. The experimental results suggest that the LSCM-Ru compounds are promising anodes for ethanol fueled SOFCs.

Heavy metals are released into the environment either by natural processes or by anthropogenic activities. Industries such as leather tanning, textiles, metallurgical, electroplating and mining activities discharge the chromium along with other heavy metals, which causes water pollution and environmental degradation. There are many conventional methods to overcome this problem such as chemical precipitation, ion exchange, reverse osmosis, etc but, these methods have certain drawbacks like generation of secondary sludge, inefficient removal of metal ions of low concentration, high cost etc. To overcome these limitations by conventional methods, an environmental friendly method, namely bioremediation has been adopted. Bioremediation uses microorganisms, biodegradable industrial wastes, or plants to mitigate this problem. In this investigation, bacterial strains have been isolated from the soil and water samples collected from a chromite mine in Karnataka. The capability of these bacterial strains have been assessed to remediate Cr (VI) in batch experiments in order to achieve the prescribed standards of regulatory agencies, and to elucidate the mechanisms of bioremediation of Cr (VI). Additionally, using these bacterial strains, biosensors have been developed to detect Cr (VI) ions in the solution by electroanalytical techniques. The major objectives of this research investigation are: a) Isolation, characterization and identification of bacterial strains from water and soil samples obtained from a chromite mine in Karnataka. b) To study the ability of three isolated bacterial strains namely Arthrobacter sp, Exiguobacterium sp. and Micrococcus sp. to remediate Cr (VI) during growth in media, amended with different concentrations of Cr (VI) c) Delineation of the probable mechanisms of bioremediation of Cr (VI) by three bacterial strains with the aid of proteomic and metabolomic studies d) Optimization of factors influencing the bioremoval of Cr (VI) using the isolated bacterial strains as biosorbents in batch experiments. c) Elucidation of mechanisms of bioremoval of Cr (VI) at the microbe – metal interface for all three bacterial strains, adopting characterization techniques like FTIR, XPS, SEM – EDS and zeta potential measurements. d) Micrococcus sp. was chosen for the fabrication of biomodified carbon paste electrode (CPE) to sense the Cr (VI) ions using voltammetric techniques, namely cyclic voltammetry (CV) and differential pulse cathodic stripping voltammetry (DPCSV). The salient findings of this research work are highlighted as follows: Firstly, bioremediation experiments were carried out using the bacterial strains isolated from soil and water samples collected from the chromite mines of Mysore Minerals Limited, Hassan district, Karnataka, India. Initially, the characterisation of the isolated bacterial strains were carried out with respect to their biochemical aspects, antibiotic susceptibility, morphology using scanning electron microscopy and cell wall nature by Gram’s staining. The identification of the three isolated bacterial strains were accomplished by 16S rRNA method and the three bacterial strains have been identified as Arthrobacter sp., Exiguobacterium sp. and Micrococcus sp.. The experiments were conducted to assess the potential of the isolated bacterial strains namely, Arthrobacter sp., Exiguobacterium sp. and Micrococcus sp., for the remediation at two different concentrations of 10 mg/L and 30 mg/L of Cr (VI) ions, during cell growth i.e. using metabolically active cells of bacteria. It was found that the three bacterial strains could bioreduce toxic Cr (VI) to the less toxic Cr (III) form, by 95% to 99%, within a time span of 12 h to 120 h. In the experiment with sulphate as the competitive ion in the growing mode of the bacterial strains Arthrobacter sp., Exiguobacterium sp. and Micrococcus sp., the percentage bioreduction of Cr (VI) to Cr (III) was not hampered. Scanning electron microscopic studies on the bacterial cells of Arthrobacter sp., Exiguobacterium sp. and Micrococcus sp., before and after interaction with Cr (VI) showed the morphological changes after interaction with Cr (VI), as an adaptive strategy to counter the toxic effect of Cr (VI). Further, to elucidate the mechanisms of bioreduction of Cr (VI) to Cr (III) by the three bacterial strains, the proteins and metabolites were isolated from the pristine bacterial cells and Cr (VI) interacted bacterial cells. The proteins were isolated from different parts of the cells and assessed for the differential expression of proteins under Cr (VI) stress. It was found that, seven differentially expressed protein bands were observed on SDS PAGE profile of Arthrobacter sp. interacted with Cr (VI), from the soluble protein isolated from the crude extract, devoid of cell membrane. A single band of differentially expressed protein was observed in the extracellular secretion in Exiguobacterium sp. and in the case of Micrococcus sp. four differentially expressed proteins were observed in the membrane fraction of proteins. The mass spectrometry data of the differentially expressed proteins were used to identify the probable protein candidates using MASCOT search in NCBIr database. It was found that some of these proteins were a class of transport proteins and a few belong to the reactive oxygen species scavengers. These findings suggested that the bioreduction of Cr (VI) to Cr (III) involved the efflux mechanism and ROS scavenger production, to resist the toxicity of Cr (VI). The metabolite concentration profile was studied for the all three bacterial cells in the absence and presence of Cr (VI) using NMR spectroscopy. The results of this study showed an increase and decrease in the concentration of various metabolite components after interaction with Cr (VI), and this was observed in all the three bacterial strains. Some of the metabolites identified using Chenomx 8.1 metabolite library, were found to be osmoprotectants like betaine, proline etc, which combat the stress of Cr (VI). Therefore, the overall bioremediation of Cr (VI) by metabolically active bacterial cells is through bioreduction of toxic Cr (VI) to the less toxic Cr (III) form and the resistance mechanisms to overcome the toxic effect of Cr (VI) is by the efflux mechanism, production of osmoprotectants and expression of ROS scavengers. In the third part of investigation, the bioremoval of Cr (VI) ions in batch experiments using metabolically inactive cells as biosorbents, for all the three bacterial strains, were studied. The bioremediation efficiency of each bacterial strain was evaluated, considering the various parameters like effect of contact time of bacterial cells with the Cr (VI) ions, pH of Cr ion solution, biomass loading and initial concentration of Cr (VI) ion. The Cr (VI) biosorption efficiency obtained for the bacterial strains Arthrobacter sp., Exiguobacterium sp. and Micrococcus sp. was found to be 93 %, 85 % and 100 % respectively. Apart from the biosorption of Cr (VI) by bacterial cells, the residual Cr was found to be in the form of Cr (III) ions. Therefore, complete bioremoval of Cr (VI) ions could be achieved as a combined process of biosorption and bioreduction, for all three bacterial strains, meeting the acceptable limits prescribed for Cr (VI) ion for drinking water, by regulatory agencies i.e. 0.05 mg/L of Cr (VI) ions. The biosorption of Cr ions by all the three bacterial strains were found to follow a typical Langmurian behaviour. The bioremediation process by the bacterial strains was also evaluated using suitable kinetic models and the results indicated that the bioremoval of Cr (VI) by Arthrobacter sp., Exiguobacterium sp. and Micrococcus sp. followed pseudo second order kinetics. The next aim was to ascertain the mechanism of bioremoval of Cr (VI) ions by the metabolically inactive cells. For this, different characterisation techniques were adopted that aided in the elucidation of reactions occurring at the interface of bacterial cell surface and Cr solution. The nature of interacting forces in bioremoval process was found out by desorption studies, and it was observed that only partial desorption of Cr ions was achieved from the biosorbed bacterial cells. This was further confirmed, by calculation of Gibbs free energy and the values were found to be in the range of – 25 to -32 kJ/mol, thus indicating that the process of bioremoval of Cr (VI) ions by the bacterial cells, is by chemisorption process. The variation in the charge of the bacterial cell surface, before and after interaction with chromium ions, was studied by performing zeta potential measurements as a function of pH. The surface charge of the bacterial cells alone was found to be negatively charged over a wide range of pH. Subsequent to interaction of the bacterial cells with the negatively charged oxyanions of Cr (VI) ions, the surface charge was observed to be less electronegative, which further confirmed the binding of the positively charged Cr (III) ions, formed via bioreduction on the bacterial cell surface. FTIR spectral studies revealed the functional groups involved, in bioremoval of Cr ions, present on bacterial cell surface. The functional group facilitating the bioremoval of Cr ions are –NH, -COOH and phosphate. EDS studies confirmed the Cr peak for the bacterial cells interacted with Cr ions. The oxidation state of Cr ion bound to the bacterial cell surface was determined with the help of XPS analysis. It was interesting to observe the Cr (III) peaks along with their Cr (VI) peaks. These studies provided evidence in support of the bioreduction of Cr (VI) to Cr (III) and biosorption of bioreduced Cr (III) ions onto the surface of bacterial cells, apart from the fraction present in bulk solution. The next objective was to assess the potential of Micrococcus sp. as sensor for the detection of Cr (VI) ions, using electroanalytical techniques such as, cyclic voltammetery (CV) and differential pulse cathodic stripping voltammetry (DPCSV). For this, Carbon Paste Electrode (CPE) was coated with the bacterial strain namely, Micrococcus sp and the modified electrode was used as the working electrode in a three electrode system. The developed biomodified electrode showed an approximately 3-fold increase in the sensing of Cr (VI) ion in comparison with the unmodified electrode CPE, which is attributed to the binding of Cr (VI) ions to functional groups present on the bacterial cell surface. The lower limit of detection obtained for Cr (VI) ions using CV was found to be 1 x10-4 M. The lower limit of detection was improved to 1 x 10-9 M of Cr (VI) using DPCSV.

M.Sc. / This study focuses on the Merensky Reef (MR) occurring within the Two Rivers Platinum mine property in the farm Dwarsriver 372 KT, on the Southern sector of the Eastern Limb of the Bushveld Complex. Five MR exploratory drill core intersections were obtained. Petrographic and mineral chemical characteristics of these drill core samples focused on the characterization of minerals like clinopyroxene, orthopyroxene, plagioclase, chromite and olivine. Data of the cryptic variation of orthopyroxene, plagioclase and chromite, from a 10 m interval (approximate thickness of the section studied); from footwall through the MR to the hangingwall lithologies at Dwarsriver are described in this study. Locally the vertical cryptic variation of these minerals is broadly consistent with regional trends of the RLS. The lateral variation (i.e. along strike) is less pronounced; however, locally these minerals appear to be chemically evolving moving to the south of the property. Footwall orthopyroxene compositions vary from a minimum of En66 and reach a maximum of En84. Those of the MR range from En71 to En85. Hangingwall orthopyroxene compositions range from En60 and reach a maximum of En80. Plagioclase compositions in the footwall units range from a minimum of An69 and reach a maximum of An85. Those of the MR range from a minimum of An35 to a maximum of An84. This wide range in plagioclase compositions is believed to be as a result of the increased presence of fluids within the MR interval. The hangingwall plagioclase compositions range from An64 to An84. By analogy of the Western Limb, where the lithologies of the Northwestern sector are believed to be proximal to the feeder of this limb; the local lateral variation in the present study suggests that the lithologies of either the Central or Western sectors are most probably proximal to the feeder for the Eastern Limb. PGM assemblages associated with and adjacent to the MR chromitite stringers were evaluated using an MLA. Data obtained from this technique is in broad agreement with regional studies of the MR. With the aid of wholerock PGE assays the MLA technique has proven to be a powerful tool in evaluating PGM assemblages relatively quickly, from a few carefully selected samples. The mineralogical associations of the PGM with the gangue and host minerals have shown three main associations. These are the associations of chromite, BMS and silicates with the PGM, of which the base metal sulfide (BMS) association is remarkable given that these have a relatively low modal abundance. The relatively high mineralogical association of the BMS with PGM has been explained by a model involving a base metal sulfide liquid which possibly scavenged chalcophile and siderophile elements. Chromite chemistry and modal analyses of MR secondary silicate phases, which peak adjacent to the chromitite stringers, suggests elevated fluid overprinting within and adjacent to the chromitite stringers. The upper chromitite stringers, however, have higher abundances of PGM phases that are believed to be secondary in origin relative to the basal chromitite stringers. Generally the PGM associated with the upper chromitite stringers are also bigger in size averaging 70 μm as opposed to 27 μm for those associated with the basal chromitite stringers. The increase in grain size of the PGM along with the higher modal abundance of secondary PGM phases associated with the upper stringers is believed to be as a result of fluids. These fluids although affecting both the upper and basal chromitite stringers, appear to have had a relatively higher influence on the upper chromitite stringers. The most common PGMs encountered in this study are isoferroplatinum, sperrylite, michenerite, maslovite, cooperite, laurite and braggite.

Europe’s largest chrome deposit is hosted by the 2.44 Ga Kemi ultramafic layered intrusion. The lower half of the intrusion consists of peridotites, pyroxenites and chromitite layers while the upper half consists of websterites, gabbronorites and leucogabbros. The mafic minerals of the lower and upper parts of the intrusion are altered to serpentine, chlorite, talc, amphiboles and carbonates. However, the original mineralogy is still preserved in the middle part of the intrusion. Earlier work on the Kemi intrusion concentrated mainly on the economically important chromitite layers and suggested that these layers were formed through contamination of a single pulse of primitive magma by underlying Archaean basement crustal material. The broad variations of the major element concentrations reflect variations in the mode of the Kemi rocks. The petrology, which shows olivine- and orthopyroxene-dominated rocks in the lower portion of the intrusion to plagioclase- and clinopyroxene-dominated rocks in the upper portion, shows a gross consistency with a fractional crystallization process.The incompatible elements are relatively enriched in the lower portion of the intrusion which is not consistent with a broad fractional crystallization process. These variations suggest that the ultramafic portion of the KemiIntrusion is relatively enriched in trapped liquid compared to the mafic portion.ε2.44 Nd values ranges from +4 (consistent with depleted mantle source) to -10 (indicating a contribution from Archaean crust). The lower peridotites, pyroxenites and websterites have ε2.44 Nd values ranging between depleted mantle signatures and -2, whereas the gabbroic cumulates have ε2.44 Nd values which cover a range from around -5 to -10. Nd isotopic variation in the lower part of the profile is punctuated by distinct spikes to lower ε2.44 Nd corresponding to the chromitite horizons. Both the lower and upper portions of the Kemi Intrusion show enrichment of LREEC1 relative to HREEC1. The LREEC1 enriched values start to increase markedly from about the 1000 meter mark and continue to increase in value towards the roof of the intrusion.The main enrichment of PGE (ΣPPGE = 55 to 148 ppb) occurs approximately 90 to 160 m above the basal contact, beginning within andcontinuing above the main chromitite ore horizon. The mantle-normalized PGE abundances of the main chromitite horizon and the peridotites and pyroxenites below it show enrichment of IPGEPM (Os + Ir + Ru) relative to PPGEPM (Rh + Pd + Pt). In contrast, the overlying rocks are characterised by enrichment of PPGEPM relative to IPGEPM. These PGE-patterns suggest the influence of two distinct controlling processes above and below the main chromitite reef.The isotopic data are consistent with the initial introduction of multiple pulses of depleted mantle-derived magma crystallising olivine and pyroxene. Before the parent magma was fed into the Kemi magma chamber, it underwent crustal contamination and assimilation in a staging chamber within the lower crust. Some of these pulses were “critically crustally contaminated”, inducing chromite saturation and precipitation. The modelling also predicts minor in-situ contamination of the parent magma in the Kemi chamber with its wall and roof rocks. Above the main chromitite layer (about 160 m above the basal contact), the chromite content decreases and the PPGEPM/IPGEPM values increase which is consistent with scavenging of the IPGE into the lowermost layers and/or evolving magma compositions. Above 1000 m, the isotopic and REE data indicate a new magma pulse which has also been extensively contaminated in the staging magma chamber before emplacement into the Kemi magma chamber. The contamination in the staging magma chamber increased which is reflected in a progressively larger crustal component towards the top of the Kemi Intrusion

The Uitkomst Complex is located within the Great Escarpment area close to the town of Badplaas, approximately 300 km due east of Pretoria, in the Mpumalanga Province, South Africa. This complex is believed to represent a layered conduit system related to the 2.06 Ga Bushveld Complex. The succession from the bottom up comprises the Basal Gabbro- (BGAB), Lower Harzburgite- (LHZBG) and Chromitiferous Harzburgite (PCR) Units, collectively referred to as the Basal Units, followed by the Main Harzburgite- (MHZBG), Upper Pyroxenite-(PXT) and Gabbronorite (GN) Units, collectively referred to as the Main Units. The Basal Unit is largely hosted by the Malmani Dolomite Formation, in the Pretoria Group of the Transvaal Supergroup sediments. The Lower Harzburgite Unit contains numerous calc-silicate xenoliths derived from the Malmani Dolomite. The Basal Units host the economically important nickel-bearing sulphide and chromite deposits exploited by the Nkomati Mine. An area of extensive localized talc-chlorite alteration is found in the area delineated for large scale open cast mining. This phenomenon has bearing on the nature and distribution of the sulphide minerals in the Chromitiferous Harzburgite and to a lesser extent the Lower Harzburgite Units. The Basal Unit is comprised of both near pristine areas of mafic minerals and areas of extensive secondary replacement minerals. Of the olivine minerals, only fosterite of magmatic origin is found, the fosterite suffered hydrothermal alteration resulting in replacement of it by serpentine and secondary magnetite. Three different types of diopside are found, the first is a primary magamatic phase, the second is a hybrid “transitional” phase and the third, a skarn phase. Hydrothermal alteration of the matrix diopside led to the formation of actinolite-tremolite pseudomorphs. This secondary tremolite is intergrown with the nickeliferous sulphide grains. Chromite grains are rimmed or replaced by secondary magnetite. Pyrrhotite grains is also rimmed or replaced by secondary magnetite. Talc and chlorite is concentrated in the highly altered rocks, dominating the PCR unit. Primary plagioclase and calcite do not appear to have suffered alteration to the same extent as the other precursor mafic magmatic and hydrothermal minerals. It is suggested that the PCR was the first unit to be emplaced near the contact of the dolomite and shale host rock. The more primitive mafic mineral composition and presence of chromitite attest to this interpretation. The LHZBG and MHZBG units may have been emplaced simultaneously, the LHZBG below and the MHZBG above. Interaction and partial assimilation of the dolomitic country rock led to a disruption of the primary mafic mineralogy, resulting in the preferential formation of diopside at the expense of orthopyroxene and plagioclase. Addition of country rock sulphur resulted in sulphur saturation of the magma and resulted in the observed mineralization. The downward stoping of the LHZBG magma, in a more “passive” pulse-like manner led to the formation of the calc-silicate xenolith lower third of this unit. It is proposed that the interaction with, and assimilation of the dolomitic host rock by the intruding ultramafic magmas of the Basal Units are responsible, firstly, for the segregation of the nickeliferous sulphides from the magma, and secondly for the formation of a carbonate-rich deuteric fluid that affected the primary magmatic mineralogy of the Basal Unit rocks. The fluids released during the assimilation and recrystallization of the dolomites also led to the serpentinization of the xenoliths themselves and probably the surrounding hybrid and mafic- ultramafic host rocks. The CO2-rich fluids migrated up and outward, while the H2O-rich fluids remained confined to the area around the xenoliths and LHZBG unit. The H2O-rich fluid is thought to be responsible for the retrograde metamorphism of the precursor magmatic and metamorphic minerals in the Lower Harzburgite Unit. The formation of an exoscarn within the dolomitic country rocks and a selvage of endoskarn on the contact form an effective solidification front that prevented further contamination of the magma. It is also suggested that these solidification fronts constrained the lateral extent of the conduit. The CO2-enriched deutric fluid was able to migrate up to the PCR unit. Here the fluid was not removed as effectively as in the underlying parts of the developing conduit. This resulted in higher CO2-partial pressures in the PCR unit, and the stabilization of talccarbonate assemblages that extensively replaced the precursor magmatic mineralogy. Intrusion of the magma into the shales, which may have been more susceptible to assimilation and greater stoping, led to a broadening in the lateral extent of the Complex, in the Main units above the trough-like feature occupied by the Basal Units. Late-stage, hydrous dominated fluid migration is inferred to have been constrained to the central part of the conduit. This is demonstrated by the dominance of chlorite in the central part of the Uitkomst Complex in the study area. The Uitkomst Complex was further deformed by later intrusions of dolerite dykes. Weathering of the escarpment led to exposure of the conduit as a valley and oxidation of the surficial exposed rocks. / Thesis (PhD)--University of Pretoria, 2012. / Geology / unrestricted

This paper examines how Speller’s theory of success in amphibious operations can be applied on a successful amphibious operation. The research has been encouraged by the fact that previous research concerning success in amphibious operations appears to be lacking. No previous studies of the theory have been found, which further strengthen the necessity for this study. The theory is examined by a single-case study of the recognised amphibious assault on Inchon during the Korean War. The theory is able to explain the success, otherwise the credence to the theory would be refuted. The result of the analysis discloses that Speller’s theory successfully explains the Inchon success in every analytical aspect but deception. The study shows that the coalition forces did not manage to or intend to deceive the North Korean opponent in relation to how an amphibious landing should take place. This study supports the theory as explanatory and can serve as vital knowledge when planning and executing an amphibious operation; however, to strengthen the study’s result, further studies are necessary.

Neste trabalho estuda-se o comportamento de redução para a obtenção da liga FeCrAC a partir da pelota auto-redutora feita de minério de cromita, coque de petróleo, ferro-silicio, cal hidratada, sílica e cimento portland ARI. As principais variáveis consideradas são: teor de redutor na composição da pelota, quantidade do redutor, temperatura e tempo. Inicialmente os materiais (cromita, ferro-silício, coque de petróleo, cal hidratada, sílica e cimento Portland ARI), foram caracterizados por: análise química e análise granulométrica. Após a caracterização os materiais (cromita, ferro-silício, coque de petróleo e cimento Portland ARI) foram aglomerados na forma de pelotas juntamente com cal hidratada e sílica para ajuste da basicidade quaternária da escória. A redução das pelotas foi feita num forno de indução que pode atingir temperaturas de até 1973K (1700oC). Todos os experimentos de redução foram realizados no aparato experimental utilizando-se cadinhos de grafite nas temperaturas de 1773K (1500oC), 1823K (1550oC) e 1873K (1600oC). Após os ensaios de redução os produtos obtidos (escória e metal) foram analisados por microscopia ótica, por microscopia eletrônica de varredura (MEV) e análise por EDS. O efeito do aumento da temperatura na redução da cromita é significativo. Houve aumento na velocidade de redução de 4 a 6 vezes com o aumento de 1773K (1500oC) para 1873K (1600oC). Os resultados indicam um efeito marcante de pequenas adições de Fe-Si na velocidade de redução da cromita. Na temperatura de 1773K (1500oC) as adições até ~2% de Fe-Si são benéficas e para adições maiores praticamente não há vantagens técnicas e econômicas. Os tempos necessários para atingir a fração unitária de redução foram 12, 7,5 e 5 minutos para adições de Fe-Si de 0, ~1%, e ~2%, respectivamente; a temperatura de 1823K (1550oC). À temperatura de 1873K (1600oC) as adições de Fe-Si na pelota apresentam também efeitos significativos na velocidade de redução, porém adições de ~1%, e ~2% mostraram os mesmos resultados, indicando que o teor ótimo de adição de Fe- Si na pelota deve estar em torno de 1%. Verificou-se que a utilização de pelotas auto-redutoras contendo 26% em excesso, sobre o estequiométrico, de coque de petróleo aumentou o rendimento de recuperação de Cr de 96% para 98%. O rendimento e a eficiência do processo de auto-redução supera aos processos convencionais de produção de FeCrAC, obtendo-se altas recuperações de cromo na faixa de 96% até 98% para Cr. / The reduction behaviors, at high temperature, of the self-reducing pellets of chromites for production of high carbon ferro-chromium are studied in this work. The influences of the temperature, of the excess of reductant and the small addition of the Fe-Si were analyzed. The materials used (chromites, petroleum coke, Portland cement, hydrated lime and silica) were characterized chemically and by size distribution. The composite pellets (self-reducing) were produced aiming a quaternary basicity of 0.91. The reductant was calculated considering a stoichiometry of reduction and dissolution of 4wt%C in the final metallic phase. The reduction experiments were made in a special system, in argon atmosphere, heated by induction and at temperatures of 1773, 1823 and 1873K. The dried pellets were placed into a pre-heated graphite crucible and left there along up to no gas evolution was observed. The results of the reacted fraction with time were plotted and the obtained product (metallic and slag phases) after experiments were analyzed by optical and by electron micrograph. The chemical estimations were made by micro-analysis (EDS) The effect of increasing the temperature of reduction was sensitive, such that, the reduction rate increased 4 to 6 times with increase of temperature from 1773 to 1873. The small additions, up to 2% of Fe-Si, for substituting the equivalent fixed carbon of the petroleum coke showed to improve substantially the reduction rate, almost doubling it in comparison with pellets without any addition. The use of excess of 26%, over the stoichiometry, of the petroleum coke decreased around 50% of the chromium content in the slag, with relation to pellet without excess. The chromium recovery yield reached 98%. This result coupled with very high reduction rate of self-reducing pellets show the potential for self-reducing processes for ferro-chromium production.

Parcels of diamond crystals from the A154 South kimberlite diatreme, Northwest Territories (n=281), and the Lynx kimberlite dyke, Quebec (n=6598) were examined in terms of colour, size, morphology, and UV fluorescence (A154 South samples only). A subset of stones from each parcel (A154 South: n=60, Lynx: n=20) were cut and polished to expose internal zonation and mineral inclusions. Exposed primary mineral inclusions were quantitatively analyzed for major elements by EMPA. Diamond crystals from the Kelsey Lake kimberlite diatreme, Colorado (n=20), were cut into plates and analyzed for nitrogen aggregation states by FTIR. Twelve of these stones were then analyzed with further subsets from A154 South (n=18) and Lynx (n=16) for carbon isotope ratios and nitrogen abundances by SIMS. Every diamond crystal cut and polished had its internal zonation imaged with CL. Mineral inclusion data from A154 South and Lynx show that the mantle keel of the Slave craton is slightly less depleted than that of the Superior craton, and both are less depleted than those of the Kaapvaal and Siberian cratons. Equilibration conditions plot on hotter geothermal gradients (surface heat flows ~42 mW/m2) than for those of typical Archean cratons (≤40 mW/m2). Equilibration temperatures (~1150-1250°C) are ~100-200°C hotter than previously reported from Kelsey Lake (~1020°C). Kelsey Lake and A154 South samples have carbon isotope ratios and nitrogen contents typical of most diamond populations worldwide. Diamond crystals from Lynx are entirely different, consisting of mostly Type II diamond with δ13C (vs. PDB) values from approximately -3.6 ‰ to +1.7 ‰. These 13C-enriched samples are suggested to be the result of extreme Rayleigh fractionation of diamond from a carbonate fluid and possibly input of carbon sourced from subducted abiotic oceanic crust. Also notable is that growth trends (δ13C-[NT]) for most of the samples studied show little or no consistency with published fractionation models.

Parcels of diamond crystals from the A154 South kimberlite diatreme, Northwest Territories (n=281), and the Lynx kimberlite dyke, Quebec (n=6598) were examined in terms of colour, size, morphology, and UV fluorescence (A154 South samples only). A subset of stones from each parcel (A154 South: n=60, Lynx: n=20) were cut and polished to expose internal zonation and mineral inclusions. Exposed primary mineral inclusions were quantitatively analyzed for major elements by EMPA. Diamond crystals from the Kelsey Lake kimberlite diatreme, Colorado (n=20), were cut into plates and analyzed for nitrogen aggregation states by FTIR. Twelve of these stones were then analyzed with further subsets from A154 South (n=18) and Lynx (n=16) for carbon isotope ratios and nitrogen abundances by SIMS. Every diamond crystal cut and polished had its internal zonation imaged with CL. Mineral inclusion data from A154 South and Lynx show that the mantle keel of the Slave craton is slightly less depleted than that of the Superior craton, and both are less depleted than those of the Kaapvaal and Siberian cratons. Equilibration conditions plot on hotter geothermal gradients (surface heat flows ~42 mW/m2) than for those of typical Archean cratons (≤40 mW/m2). Equilibration temperatures (~1150-1250°C) are ~100-200°C hotter than previously reported from Kelsey Lake (~1020°C). Kelsey Lake and A154 South samples have carbon isotope ratios and nitrogen contents typical of most diamond populations worldwide. Diamond crystals from Lynx are entirely different, consisting of mostly Type II diamond with δ13C (vs. PDB) values from approximately -3.6 ‰ to +1.7 ‰. These 13C-enriched samples are suggested to be the result of extreme Rayleigh fractionation of diamond from a carbonate fluid and possibly input of carbon sourced from subducted abiotic oceanic crust. Also notable is that growth trends (δ13C-[NT]) for most of the samples studied show little or no consistency with published fractionation models.

As a result of increasing cost, efficiency and environmental pressures ferrochrome producers strive towards lower overall energy consumption. Increases in local electricity prices have placed particular pressure on South African ferrochrome producers. Pelletised chromite pre–reduction is likely the currently applied ferrochrome production process option with the lowest specific electricity consumption. In this process fine chromite, together with a carbonaceous reductant and a clay binder is milled, pelletised and pre–reduced. In this dissertation it is demonstrated that the functioning of the clay binder in this process is not as straightforward as in conventional metallurgical pelletisation processes, since the cured pre–reduced pellets are characterised by an oxidised outer layer and a pre–reduced core. Conventional performance characteristics of clay binders (e.g. compressive strength and abrasion resistance) therefore have to be evaluated in both oxidative sintering and reducing environments. Two clay samples, i.e. attapulgite and bentonite, were obtained from a local ferrochrome producer and investigated within the context of this study. Results indicated that the compressive and abrasion resistance strengths of oxidative sintered pellets for both clays were substantially better than that of pre–reduced pellets. Thus, although the objective of the chromite pre–reduced process is to achieve maximum pre–reduction, the strength of pre–reduced chromite pellets is significantly enhanced by the thin oxidised outer layer. The strength of the bentonite–containing pellets was found to be superior in both pre–reducing and oxidative sintering environments. This is significant, since the attapulgite clay is currently the preferred option at both South African ferrochrome smelting plants applying the pelletised chromite pre–reduction process. Although not quantitatively investigated, thermo–mechanical analysis indicated that the hot strength of the attapulgite pellets could be weaker than the bentonite–containing pellets. The possible effects of clay binder selection on the level of pre–reduction were also investigated, since it could have substantial efficiency and economic implications. For both case study clays investigated, higher clay contents resulted in lower pre–reduction levels. This has relevance within the industrial process, since higher clay contents are on occasion utilised to achieve improved green strength. The average pre–reduction of the bentonite–containing pellets were also consistently higher than that of the attapulgite–containing pellets. Again, this is significant, since the attapulgite clay is currently the preferred option. In general the case study results presented in this dissertation indicated that it is unlikely that the performance of a specific clay binder in this relatively complex process can be predicted; based only on the chemical, surface chemical and mineralogical characterisation of the clay. / Thesis (M.Sc. (Chemistry))--North-West University, Potchefstroom Campus, 2012.