Made available in DSpace on 2014-10-09T12:34:08Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:40Z (GMT). No. of bitstreams: 0 / Esse trabalho teve como objetivo verificar o efeito da adição do ácido oléico na moagem de alta velocidade/energia na obtenção de pós magnéticos em escala nanométricas da liga Pr12Fe65,9Co16B6Nb0,1. A primeira etapa deste trabalho, envolveu a obtenção de pós magnéticos por meio do processo de hidrogenação, desproporção, dessorção e recombinação (HDDR), utilizando a pressão de H2 de 930 mbar (hidrogenação e desproporção) e temperatura de dessorção e recombinação de 840 ºC. Inicialmente, os pós HDDR foram submetidos à moagem de alta velocidade/energia a 900 rpm, com variação do volume do meio de moagem (ciclohexano) sem adição de ácido oleico. Em seguida, os pós HDDR foram submetidos à moagem com adição de ácido oleico, variando o tempo de moagem. Após a moagem, foi realizado tratamento térmico dos pós a 700 ºC ou 800 ºC durante 30 min., com a finalidade de cristalização do pó. Foi verificado que, a utilização de 6,6 ml de ciclohexano como meio de moagem e com adição de ácido oleico há uma melhora na eficiência da moagem dos pós. Para adições de surfactante, de 0,02 a 0,05 ml e tempos de moagem até 360 minutos, não ocorre a aglomeração dos pós magnéticos no pote de moagem, obtendo acima de 90% de eficiência na moagem. A segunda etapa deste trabalho envolveu a caracterização dos pós magnéticos: utilizando magnetômetro de amostra vibrante, microscopia eletrônica de Varredura, microscopia eletrônica de transmissão e difração de raios-X. Os resultados obtidos mostraram que a adição de ácido oléico na moagem de alta velocidade/energia proporciona uma melhora nas propriedades magnéticas. Com a variação do tempo de moagem a fase Fe-α presente no pó HDDR apresenta diminuição no tamanho do cristalito (de 35 para ~ 10 nm) enquanto que, na fase Pr2Fe14B verifica-se menor grau de cristalinidade. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2015-01-21T10:06:51Z No. of bitstreams: 0 / Made available in DSpace on 2015-01-21T10:06:51Z (GMT). No. of bitstreams: 0 / O interesse em utilizar terras raras para investigar propriedades e funções de sistemas bioquímicos tanto quanto de determinar substâncias biológicas tem crescido em diferentes áreas, incluindo biomarcadores em imunologia (fluoroimunoensaios). Atualmente, o uso de terras raras no diagnóstico de diversas doenças tem se tornado muito importante com o desenvolvimento de kits de diagnóstico. Como característica principal, as terras raras podem apresentar longo tempo de vida, fotoestabilidade e bandas de emissão finas e bem definidas na região do visível, demonstrando vantagens únicas quando comparadas a outras espécies luminescentes. O presente trabalho teve como objetivo sintetizar molibdatos de terras raras pelo método de coprecipitação, assim como caracterizá-los através de técnicas como: difração de raios X, espectroscopia do infravermelho, análise termogravimétrica, microscopia eletrônica de varredura, microscopia eletrônica de transmissão e estudos de luminescência. Nesse trabalho foram desenvolvidos três diferentes estudos de síntese: a influência da variação da velocidade do dispersor no momento da precipitação; a influência do tratamento térmico na estrutura, morfologia e propriedades luminescentes; e a influência da concentração do íon dopante nas propriedades estruturais e espectroscópicas. Outro passo importante desse trabalho foi o de aminofuncionalizar as nanopartículas utilizando um organosilano (APTES) para recobrir e estabelecer pontos para que essas partículas pudessem se ligar a espécies biológicas. Foi comprovado pelos resultados das caracterizações que esse processo foi eficiente e a incorporação da sílica foi bem sucedida. O Antígeno Específico da Próstata (PSA) foi então ligado às nanopartículas funcionalizadas para possibilitar o diagnóstico de câncer de próstata através de fluoroimunoensaios e dessa forma, níveis de detecção foram estabelecidos. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

A junção miotendínea (JMT) é a principal área de transmissão de força e de lesões do sistema muscular esquelético, atuando no posicionamento e estabilização articular. O estudo morfológico das estruturas e ultraestruturas da JMT do músculo esternomastóideo (EM) demonstrará as características desde o nascimento, ao revelar os esboços iniciais do desenvolvimento, sua completa formação na fase adulta e possíveis alterações e comprometimentos morfofuncionais em decorrência do processo fisiológico do envelhecimento. O objetivo do presente estudo consiste em descrever as características estruturais e ultraestruturais da JMT do músculo EM de ratos Wistar recém-nascidos, adultos e idosos empregando os métodos de microscopia de luz, microscopia eletrônica de varredura e microscopia eletrônica de transmissão. Foram utilizados 45 ratos Wistar, em três grupos (n=15): Grupo Recém-nascido: animais com 5 dias de vida; Grupo Adulto: animais com 4 meses de idade; Grupo Idoso: animais com 24 meses de idade. Os animais, após anestesia, foram dissecados os músculos EM e as JMT destes foram processadas de acordo com os métodos empregados. As características morfológicas da JMT do Grupo Recém-nascido revelaram o seu esboço durante o desenvolvimento, através da interação das células musculares e elementos da matriz extracelular, destacando delgadas dobras no sarcolema e elevada atividade celular através de inúmeras tenoblastos e mitocôndrias ovais aglomeradas. No Grupo Adulto revelaram características clássicas da JMT em destaque às dobras do sarcolema formando longas projeções denominadas de evaginações e invaginações sarcoplasmáticas. No Grupo Idoso foram observadas alterações na JMT, com espessamento em ambos os níveis das invaginações sarcoplasmáticas e nas comunicações centrais com as junções laterais, além de espessamento de feixes de fibras colágenas e redução celular nesta área. Conclui-se que a JMT desde os estágios iniciais de desenvolvimento ao envelhecimento apresentam intenso processo de formação, remodelamento e alterações em decorrência do processo fisiológico do envelhecimento. / The myotendinous junction (MTJ) is the main area of power transmission and injuries of the musculoskeletal system, working on positioning and joint stabilization. The morphological study of the structures and ultrastructures of JMT muscle esternomastóideo (EM) demonstrated characteristics from birth, to reveal initial development, its complete training in adulthood and possible changes and compromises morphofunctional due to the physiological process of aging. The aim of this study is to describe the structural and ultrastructural features of JMT muscle EM Wistar rat newborns, adults and the elderly employing the methods of light microscopy, scanning electron microscopy and transmission electron microscopy. We used 45 Wistar rats into three groups (n = 15): Newborn Group: animals with 5 days of life; Adult Group: animals with 4 months of age; Group Aged: animals 24 months of age. The animals, after anesthesia, the muscles were dissected and the MTJ these were processed in accordance with the methods employed. The morphological characteristics of the JMT Group Newborn revealed his sketch during development, through the interaction of muscle cells and extracellular matrix elements, highlighting the slender folds sarcolemma and high cellular activity through numerous mitochondria oval crowded and tenoblastos. In Adult Group revealed classic features of JMT with highlight the folds of the sarcolemma forming long projections denominated evaginations and invaginations of the sarcoplasmic membrane. In Aged Group changes were observed in the MTJ with thickening at both levels of sarcoplasmic invaginations and in communications with the central lateral junctions, and thickening of collagen fibers and reduced cell in this area. We conclude that the JMT since the early stages of development to aging have intense training process, remodeling and changes due to the physiological process of aging.

The research carried out here employed analytical and imaging transmission electron microscopy and scanning transmission electron microscopy to gain a good understanding of local structure and composition of semiconductor nanocrystals and quantum dots for electronics and optoelectronics applications. One of the world's most advanced analytical scanning transmission electron microscopes in the field, the Daresbury SuperSTEM, was used to scrutinise the structure and composition of the samples. Three nanostructure systems are investigated in this thesis: 1. Structures consisting of Ge-nanocrystals (NCs) in alumina. Here HRTEM suggests relaxed and twinned smaller NCs grown annealed at lower temperature compared to elongated non-faulty bigger NCs annealed at higher temperature. HRTEM also suggests a polycrystalline structure of the matrix. 2. With regards to the InAs/GaAs quantum dots (QD) the study aims in particular at elucidating QD formation by investigating samples grown with and without growth interrupt (GI). Diffraction contrast TEM shows formation of buried dots in the sample prepared with GI whereas for the sample without GI the immediate growth of GaAs after InAs inhibits diffusion and segregation of In adotoms, and no footprint of buried dots has been observed. HRTEM and HAADF show coherent QDs in the sample with GI and abrupt InAs/GaAs interfaces in the sample without GI. In executing energy electron loss spectroscopy (EELS) and geometric phase analysis (GPA) the distribution of In in InGaAs/GaAs QDs has been obtained in samples grown in the critical thickness regime for quantum dot formation. The highest In percentage achieved in the dots grown with a nominal fraction of 100% was ~70%. EELS shows variations in the In concentration within the QD structure and wetting layer 3. In the case of Er-doped Si-NCs in silica this research tries to provide an understanding of structure, composition and position of excess Si and Er in the silica matrix of materials prepared under different growth conditions and to correlate this information with the PL emission, all with the aim to find preparation routes for optimum optical efficiency for applications of this materials system in silicon photonics. High spatial correlation between Si-NCs, Er and O in the Er and Si co-implanted sample with strong indication of an Er-oxide/Si core-shell structure had been found. The lack of an Er-oxide plasmon indicates, however, that the shell structure and its interface with the SiNCs is highly defective and a likely cause for non-radiative recombination. The sample with similar excess Er and Si concentrations but prepared in a two-stage implantation and annealing process shows a 10 times improvement in the optical emission. Here no spatial correlation between Er and Si-NCs was found in core loss EELS. EELS and HAADF evidenced more highly, near-atomically dispersed Er in the matrix with no formation of a core-shell structure as compared to the co-implanted sample. No footprint of Er-silicide plasmon was observed by low loss valence band EELS investigation in the co-implanted sample.

Orientador: Adilma Regina Pippa Scamparini / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-08T02:50:35Z (GMT). No. of bitstreams: 1 Luvielmo_MarciadeMello_D.pdf: 3297730 bytes, checksum: dc80c8868bb6f8fa43b93b87d5e0bae3 (MD5) Previous issue date: 2007 / Resumo: O presente estudo teve como objetivo fazer uma seleção de linhagens de X. campestris para a produção de goma xantana e verificar o efeito do processo de ¿stress¿ alcalino em diferentes condições de produção deste biopolímero, através da avaliação da produção de goma e da viscosidade aparente, que é um fator de elevada relevância para designar em quais processos e setores da indústria a goma xantana será aplicada. A pesquisa também teve como objetivo investigar as mudanças na estrutura da goma xantana causadas pelo ¿stress¿ alcalino, e as mudanças na ultraestrutura das células, assim como a disposição da goma em diferentes etapas da sua produção e em diferentes tempos de ¿stress¿ alcalino, a fim de contribuir com uma maior compreensão desse complexo processo. Foi selecionada a linhagem X. campestris pv. manihotis 280-95, como a de melhor desempenho em produção e qualidade, com uma produção de goma xantana de 10,8 g/L. A partir destes estudos, X. campestris pv. manihotis 280-95 passou a ser a bactéria utilizada para os estudos posteriores. O maior valor de produção de goma xantana foi atingido em ¿stress¿ alcalino com pH 12 (EA12), seguido do ¿stress¿ alcalino em pH 11 (EA11) e ¿stress¿ alcalino em pH 8 (EA08). Porém a qualidade da goma obtida após o processo de EA12 é menor se comparada à obtida sem o processo de ¿stress¿ alcalino. O hidróxido de sódio (NaOH) foi o álcali que apresentou melhor desempenho para o processo de ¿stress¿ alcalino. A produção de goma xantana (g.L-1) e as viscosidades aparentes das gomas não foram afetadas nos diferentes tempos de ¿stress¿ alcalino (EA12) testados nesse estudo (1h, 2h, 3h e 4h), na faixa de taxa de deformação testada (0 ¿ 60 s-1). A produção de goma xantana obtida da fermentação realizada em bioreator de 2 L utilizando X. campestris pv. manihotis 280-95 foi maior após o processo de ¿stress¿ alcalino por 24 horas (EA24h). Ao final de 72 horas de fermentação 9,43 g.L-1 de goma xantana foram obtidos e após 24 horas de ¿stress¿ alcalino, a produção foi 74,8% maior (16,48 g.L-1). No estudo das ultraestruturas (capítulo IV) foi possível visualizar cada passo dos processos e verificar que, mesmo no inóculo puro, observa-se também uma pequena produção de goma xantana próximo a algumas células. No final da fermentação (FF), observou-se o início de mudanças estruturais nas bactérias, como a vacuolização citoplasmática e a descontinuidade da membrana, podendo sugerir um início no processo de lise bacteriana. Após o ¿stress¿ alcalino (EA12-1h), foram observadas acentuadas diferenças estruturais nas células bacterianas. O conteúdo citoplasmático das bactérias tornou-se mais vacuolizado e verificou-se descontinuidade nas membranas das células bacterianas, indicando processo de lise bacteriana. A goma xantana que se apresentou agrupada em grumos, adquiriu uma conformação organizada em círculos concêntricos. Finalmente, pode ser mencionado que novos estudos com diferentes linhagens e condições de processo devem ser realizados procurando-se sempre melhores resultados de produção e qualidade desse biopolímero / Abstract: The present study had as objective to make a selection of strains of X. campestris for the production of xanthan gum and to verify the effect of the process of alkaline "stress" at different conditions of production of this biopolymer, through the evaluation of the gum production and of the apparent viscosity, which is a factor of high relevance, in order to allocate which processes and sections of the industry the xanthan gum will be applied in. The research also aimed to investigate changes in the structure of the xanthan gum caused by the alkaline "stress", changes in the ultrastructure of the cells, as well as the disposition of the gum at different stages of its production and at different times of alkaline "stress", so as to contribute with a better understanding of such compound process. The strain was selected X. campestris pv. manihotis 280-95, as better acting in production and quality, with a production of xanthan gum of 10,8 g.L-1 starting from these studies, X. campestris pv. manihotis 280-95 started to be the bacterium used for the subsequent studies. The largest value of production of gum xantana was reached in alkaline "stress" with pH 12 (EA12), followiedby the alkaline "stress" in pH 11 (EA11) and alkaline "stress" in pH 8 (EA08). However, the quality of the gum obtained after the process of EA12 is worse compared to what was obtained without the process of alkaline "stress." The hydroxide of sodium (NaOH) was the alkali that presented better results in obtaining the process of alkaline "stress." The production of xanthan gum (g.L-1) and the apparent viscosities of the gums were not affected in the different times of alkaline "stress" (EA12) tested in that study (1:00, 2:00, 3:00 and 4:00), at the shear rate range tested (0 - 60 s-1). The production of xanthan gum obtained from the fermentation accomplished in bioreactor of 2 L using X. campestris pv. manihotis 280-95 was larger after the process of alkaline "stress" within 24 hours (EA24h). At the end of 72 hours of fermentation 9,43 g.L-1 of xanthan gum were obtained and after 24 hours of alkaline "stress", the production was 74,8% larger (16,48 g.L-1). In the study of the ultrastructures (chapter IV) it was possible to observe each step of the processes and to verify that, even in the pure inoculum, it is also observed a small production of gum close to some cells. Atthe end of the fermentation (FF), the beginning of structural changes was observed in the bacteria, as the vacuum cytoplasm and the discontinuity of the membrane, could suggest a beginning in the process of bacterial lise. After the alkaline "stress" (EA12-1h), accentuated structural differences were observed in the bacterial cells. The content cytoplasm of the bacteria became more vacuuming and discontinuity was verified in the membranes of the bacterial cells, indicating process of bacterial lysis. The resulting xanthan gum presented in clots, acquired an organized conformationin concentric circles. Finally, it can be mentioned that new studies with different strains and process conditions should be accomplished being always sought better production results and quality of that biopolymer / Doutorado / Doutor em Ciência de Alimentos

Orientador: Marcelo Giannini / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-27T18:34:59Z (GMT). No. of bitstreams: 1 Vermelho_PauloMoreira_D.pdf: 2479320 bytes, checksum: 0d9cc50e5276a8b6e9a933c7dcd3239c (MD5) Previous issue date: 2015 / Resumo: Os objetivos deste estudo foram analisar as características ultramorfológicas da interface de união dente-resina, a resistência de união ao esmalte e dentina pelo método da microtração e os padrões de fratura dos espécimes testados. Dois adesivos "universais ou multi-molde" (Scotchbond Universal, 3M ESPE e All-Bond Universal, Bisco) foram testados nos modos autocondicionantes e com condicionamento prévio e comparados aos métodos tradicionais de união ao esmalte e dentina (grupos controles) utilizando os adesivos Optibond FL (Kerr) e Clearfil SE Bond (Kuraray Noritake). Esmalte e dentina de terceiros molares humanos foram utilizados nos procedimentos adesivos, os quais foram realizados com as instruções dos fabricantes. Após a aplicação dos adesivos, um bloco de compósito foi construído em incrementos. Os dentes foram seccionados longitudinalmente para obtenção de espécimes em formato de "palitos" para o ensaio de resistência de união por microtração (n=8) e as análises em microscopia eletrônica de transmissão (MET) (n=2). Os espécimes foram testados após 24 horas ou um ano de armazenamento em saliva artificial. Para a MET, solução traçadora de nitrato de prata foi utilizada para mostrar espaços nanométricos e evidências de degradação na área de união. As superfícies fraturadas dos espécimes foram observadas em microscopia eletrônica de varredura e os dados de resistência de união analisadas pela ANOVA três-fatores, teste de Tukey e Dunnett (5%). O condicionamento prévio do esmalte aumentou a resistência de união dos adesivos universais, mas essa reduziu após o armazenamento por um ano. Os adesivos universais mostraram menor resistência de união em esmalte que o grupo controle quando utilizados no modo autocondicionante no tempo de 24 horas. Nenhuma diferença significativa foi encontrada na resistência de união em dentina nos dois tempos de avaliação quando comparados aos adesivos universais e os controle. O armazenamento por um ano reduziu a resistência de união em dentina apenas para um adesivo universal usando no modo autocondicionante. A análise fractográfica em esmalte mostrou predomínio de fraturas mistas e coesivas na camada de adesivo. Em dentina, o predomínio foram fraturas mistas, adesivas e coesivas em compósito. A observação da ultramorfologia em MET mostrou a formação de hibridização e zonas de interação entre todos os adesivos em esmalte e dentina nos dois modos de aplicação. Sinais de nanoinfiltração foram identificados na área de união dentina-resina para os adesivos Scotchbond Universal e Clearfil SE Bond após armazenamento por um ano. Os resultados sugerem que armazenamento por um ano pode reduzir a resistência de união quando os adesivos universais foram aplicados em esmalte condicionado, mas em dentina condicionada não houve redução da resistência de união, exceto para o adesivo Scotchbond Universal. No esmalte a resistência de união do grupo controle foi maior que a dos adesivos universais no modo autocondicionante. Após o armazenamento por um ano, a resistência de união dos adesivos universais em esmalte tratado com ácido fosfórico não diferiu do grupo controle. Em dentina, não foi encontrada diferença significativa entre adesivos universais e os grupos controles, independente do modo de condicionamento / Abstract: The aims of this study were to analyze the ultramorphological characteristics of tooth¿resin interfaces, the microtensile bond strength of multimode adhesive systems bonded to enamel and dentin, and the failure pattern of tested specimens. Two multimode adhesives (Scotchbond Universal, 3M ESPE; All-Bond Universal, Bisco) were tested in both self-etch and etch-and-rinse modes and compared to control groups using traditional bonding techniques (Optibond FL, Kerr; Clearfil SE Bond, Kuraray Noritake) in enamel and dentin. Enamel and dentin from third human molars were used for bonding and adhesives used according to the manufacturer¿ instructions. A composite resin block was incrementally applied to bonded surfaces, and teeth were sectioned transversely to the tooth-composite interface to obtain specimens for microtensile bond strength (n=8) and transmission electron microscopy (TEM) analysis (n=2). Specimens were tested after storage for either 24 hours or 1 year in artificial saliva. For TEM, a silver tracer solution was used to reveal nanometer-sized spaces and evidence of degradation within resin¿dentin interfaces. Fractured surfaces of tested specimens were analyzed under scanning electron microscopy. Bond strength data were analyzed by three-way ANOVA and by Tukey¿s and Dunnett¿s tests (?=5%). The acid-etching mode increased the enamel bond strength of multimode adhesives; however, bond strength decreased after storage for 1 year. Multimode adhesives showed lower enamel bond strength than the control group adhesive when used in self-etch mode for 24 hours. No significant differences in dentin bond strength were noted between multimode and control adhesives in either evaluation period. Storage for 1 year only reduced the dentin bond strength for a multimode adhesive used in self-etch mode. Mixed and cohesive-within-adhesive-layer failures were predominant in enamel. In dentin most fractures were mixed, adhesive along the dentin or enamel, and cohesive within the composite layer. TEM analysis identified hybridization and interaction zones in dentin and enamel for all adhesives and application modes. Silver impregnation was detected on dentin¿resin interfaces after storage of specimens for 1 year only with the Scotchbond Universal and Clearfil SE Bond samples. Results suggested that storage for 1 year can reduce bond strength when multimode adhesives are applied on an etched surface, but the dentin bond strength was not affected when using the etch-and-rinse mode (except for the Scotchbond Universal sample). The enamel bond strengths of the control group adhesives were higher than those obtained for multimode adhesives in the self-etch mode. After storage for 1 year, the bond strengths of multimode adhesives in etched enamel did not differ from those of the control group adhesive. In dentin, no significant difference was noted between the multimode and control group adhesives, regardless of etching mode / Doutorado / Dentística / Doutor em Clínica Odontológica

The theoretical part of the diploma thesis deals with the basic principles of the scanning electron microscope and the environmental scanning electron microscope. A description of the signals generated by an electrons incidence onto a specimen and detection options of these signals in the mentioned microscopes is included in the work. The experimental part of the work concerns an examination of a quality of several joints soldered by different methods on the printed circuit boards after different stresses by use of a visual check and the instruments of the light microscope and the environmental scanning electron microscope. The acquired data are evaluated and summarized.

Metallic thin films consisting of separated nanostructures are fabricated by evaporative glancing angle deposition at room temperature. The columnar microstructure of the Ti and Cr columns is investigated by high resolution transmission electron microscopy and selective area electron diffraction. The morphology of the sculptured metallic films is studied by scanning electron microscopy. It is found that tilted Ti and Cr columns grow with a single crystalline morphology, while upright Cr columns are polycrystalline. Further, the influence of continuous substrate rotation on the shaping of Al, Ti, Cr and Mo nanostructures is studied with view to surface diffusion and the shadowing effect. It is observed that sculptured metallic thin films deposited without substrate rotation grow faster compared to those grown with continuous substrate rotation. A theoretical model is provided to describe this effect

M. Tech. (Department of Metallurgical Engineering, Faculty of Engineering Technology), Vaal University of Technology. / Lonmin mining company located in the Bushveld Complex of South Africa is one of the main platinum group elements (PGEs) producers in the world. Its core operations are made up of 11 shafts and inclines. There are resources of 181 million troy ounces of 3PGE + Au, and there are reserves of 32 million ounces of 3PGE + Au. One of the ore type produced at Lonmin is UG2 ore which is dominated by the high presence of chromite. The UG2 ore is also associated with PGE assemblages divided into sulphides and non-sulphides, and it is beneficiated through the froth flotation technique. Froth flotation is a physico-chemical process that is used for separation of desired valuable minerals from the gangue minerals by utilising the difference in surface properties. The process has been achieving lower recoveries with P4 (shaft name) UG2 ore compared to Eastern Platinum Limited (EPL) UG2 ore when using similar reagents suite, this leads to loss of valuable minerals to the tailings, both ores were from Lonmin. The first step was to conduct the mineralogical analysis conducted using Scanning electron microscopy- energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), and optical microscopy to study the mineral composition of the two ores, and to identify any differences between them (two ores) considering that EPL UG2 ore is a blend of P1, P2, P3 (shaft names) and P4 UG2 ores while P4 UG2 ore is not blended with any other ores. The mineralogical results showed the presence of chromite, plagioclase, enstatite and sulphide minerals. The PGEs could not be detectable by any of the techniques used due to their small size and rarity. However, X-ray diffraction detected differences in concentrations of minor gangue constituents such as talc, muscovite, chlorite and actinolite and these results suggest that reagent consuming gangue mineralogy may have contributed to the differences in PGE recoveries by flotation. Batch flotation tests were also conducted. The existing reagent suite consisted of CuSO4 as an activator, Sodium n-propyl xanthate (SPNX) as a collector, carboxymethyl cellulose CMC as a depressant, and Senfroth 200 as a frother, and this was a single collector system. Therefore it was imperative to conduct flotation n investigation on alternative collector blends in order to improve the recovery of P4 UG2 ore. SNPX was used as the primary collector and it was blended with the following co-collectors: alkyl dithiocarbamates (DTC), two formulations of S-alkyl-N-butyl thionocarbamates (ABTC C1 & ABTC C2), and two formulations O-isopropyl-N-ethyl thionocarbamate (IPETC 30 & IPETC 31), one co-collector at a time. The first test incorporated the SNPX at dosage of 150 g/t without a blend and this dosage was selected based on the current optimum practice used at Lonmin and to use as a benchmark for the project. Trying to maintain the same dosage of 150 g/t of collectors, SNPX + co-collector were blended at two different dosages of 100 g/t + 50 g/t, and was also due to the fact that the co-collectors were highly concentrated and small dosages were expected to perform very well with SNPX. Lastly, the SNPX + co-collector at dosages 100 g/t + 125 g/t, here the dosage of co-collector was very high compared to 50 g/t and this was to check the effect of high dosages of highly concentrated collectors on the performance of the ore. The flotation results showed that the use of 50 g/t of co-collectors yielded optimum PGEs + Au recoveries and grades, while the dosage of 125 g/t decreased recoveries and grades. The high dosage quantities of collectors do not necessarily mean they will yield improved recoveries and grades. Different chain structures can be used to alter the behaviour of a collector, and these may increase or decrease their capabilities to cause higher recoveries. By using a collector with a longer hydrocarbon chain the flotation limit may be extended without loss of selectivity, consequently bringing about greater water repulsion, instead of increasing the concentration of a shorter chain collector. At 100 g/t of SNPX and 50 g/t of co-collector i.e. SNPX + IPETC 30 yielded improved 3PGE + Au recovery of 85.7 % at 3PGE + Au grades of 60.14 g/t, compared to the unblended SNPX (150 g/t) which yielded 3PGE + Au recovery of 81.1 % but insignificantly higher grade of 60.53 g/t. On the other hand, SNPX + IPETC C1 blend yielded low 3PGE + Au recoveries compared to SNPX + IPETC 30 and SNPX + IPETC 31 blends, but it achieved the highest grade of 76.1 g/t. Evidently, this proves that the relationship between recovery and grade is a trade-off. The results have also shown the synergic effects, especially for SNPX blended with IPETC 30, and SNPX blended with IPETC 31 at dosage of 100 g/t (SNPX) and 50 g/t (IPETCs). It can be concluded that the different interaction obtainable from the thionocarbamate (ROCSNHR), effectively complement that from the xanthate ion (ROCS2–) to achieve more collector interaction at surface sites otherwise interactable for xanthate only. Therefore the collector blends rendered the mineral of interest hydrophobic and as a result the minerals were recovered to the concentrate. On the other hand, too much of collectors may not be beneficial. At the dosage of 100 g/t of SNPX and 125 g/t of collectors, SNPX + DTC attained lower recoveries compared to SNPX, SNPX + IPETC 30, SNPX + IPETC 31, however the grade was higher than achieved SNPX + IPETC 30, SNPX + IPETC 31 and SNPX + ABTC C1. Nevertheless, comparing these results to the dosage of 50 g/t of the co-collectors, the 125 g/t did not perform well at all. The dosage of 125 g/t of co-collectors lead to loss of collecting power and selectivity, especially for SNPX + IPETC 30, SNPX + IPETC 31, and SNPX + ABTC C1 blends. It is therefore wise to conduct an optimisation test to determine the correct dosing rate. In addition, the chromite entrainment was below the smelter limit and is very beneficial since chromite is detrimental to the furnace. Therefore, it is concluded that the blends of SNPX with IPETC 30 and IPETC 31 at a dosage 50 g/t have shown satisfying recoveries and the FeCr2O4 recovery is less than 1 % meaning there will not be any smelter penalties for FeCr2O4 content. Therefore, these are the recommended collector blends. It is recommended that further mineralogical study of the ores be conducted so that it may provide deeper insight into the causes of low recoveries under SNPX only. The system of blended collectors and its optimisation would be beneficial and can be practiced. The Chemisorption studies between the minerals and co-collectors used will provide more specific insight and details into the actual interaction synergy that gave the improved recoveries.

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