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Cinética de degradação microbiológica de torta de filtro no solo na presença de cádmio e níquel.; Filter cake microbiologycal degradation kinetics in soil on the presence of cadmium and nickel.

Firme, Lucia Pittol
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 20/04/2005 PT
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Avaliou-se o efeito das doses dos metais, cádmio e níquel, na velocidade de degradação da matéria orgânica adicionada ao solo através de torta de filtro em ensaios de respirometria. O solo utilizado, Latossolo Vermelho Amarelo de textura média, foi amostrado a uma profundidade de 0-20 cm. Foram aplicadas doses de 0; 28; 56; 112 e 200 mg kg-1 de cádmio e 0; 62,5; 125; 250 e 500 mg kg-1 de níquel como CdCl2.2,5H2O e NiCl2.6H2O, respectivamente. As doses de torta de filtro foram de 0, 40, 80 e 120 Mg ha-1, definidas com base nas doses normalmente aplicadas no cultivo de cana. Na instalação dos experimentos, as massas requeridas dos metais foram adicionadas a 800 g de solo, após a incorporação da torta de filtro. Foram empregados potes de vidro com tampa vedante e capacidade de 2 L, contendo solo umedecido para atingir 80% da capacidade máxima de retenção de água. A incubação foi conduzida à temperatura de 28oC durante 72 dias. Os dois ensaios de incubação, um para cádmio e outro para níquel, foram conduzidos em esquema fatorial 5 x 4, em delineamento inteiramente casualizado, com 3 repetições. O CO2 liberado do solo foi absorvido em solução de NaOH e quantificado por método condutimétrico. No solo, após o período de incubação...

Preparação de hidróxidos mistos nanoestruturados de níquel/cobalto e desenvolvimento de sensores FIA amperométricos; Preparation of nanostructured nickel/cobalt mixed hydroxides and development of FIA amperometric sensors

Martins, Paulo Roberto
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 21/03/2012 PT
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Nesta tese foram desenvolvidos sensores amperométricos baseados em porfirinas supramoleculares e hidróxido de níquel nanoestruturado e estabilizado na fase alfa, bem como novos materiais baseados em hidróxidos mistos de níquel e cobalto nanoetruturados e estabilizados na fase alfa. Também, um analisador FIA amperométrico, foi desenvolvido em colaboração com o Laboratório de Instrumentação Analítica do IQ-USP, para a determinação e quantificação de SO2 livre em amostras reais, como vinhos, águas de coco e sucos de frutas. Os sensores amperométricos baseados em porfirinas supramoleculares foram empregados na determinação de SO2 livre, presente em sucos de frutas e águas de coco, utilizando um sistema FIA amperométrico. O sistema FIA amperométrico foi constituído de um injetor manual, uma cela amperométrica em fluxo integrada a uma unidade de difusão de gases e um fluxo de uma solução de ácido sulfúrico e de uma solução de eletrólito. Possíveis interferentes como ácido ascórbico, catecol, glicose e benzoato de sódio foram avaliados antes de iniciar as análises das amostras reais. Os resultados das análises foram comparados com o método oficial Monier-Williams. Os níveis de SO2 livre encontrados nas amostras estavam de acordo com o que é preconizado pela Legislação Brasileira. Os eletrodos de FTO...

Catalisadores nanoparticulados de níquel e níquel-paládio obtidos a partir de precursores organometálicos; Nickel and nickel-palladium supported nanocatalysts obtained from organometallic precursors

Costa, Natália de Jesus da Silva
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 31/08/2012 PT
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A catálise é a chave para o desenvolvimento de processos químicos sustentáveis e, portanto, o preparo de catalisadores que sejam mais ativos e seletivos é sempre uma questão atual. Utilizando as propriedades diferenciadas de nanopartículas metálicas e as vantagens de separação e estabilidade de um catalisador heterogêneo, este trabalho descreve novos catalisadores de níquel e de níquel-paládio em escala nanométrica, suportados em sólidos magnéticos, para hidrogenação de olefinas. Os catalisadores de níquel apresentados neste trabalho foram preparados pela metodologia de decomposição do precursor organometálico Ni(COD)2 (COD = ciclo-octadieno), que apresenta o metal em estado de oxidação zero e permite a formação de nanopartículas metálicas após a hidrogenação das ligações C=C do ligante. O catalisador de níquel aprimorado, composto por nanoagregados de níquel, apresentou atividade superior a qualquer outro reportado na literatura para o mesmo tipo de reação. Além disso, mesmo com a facilidade de oxidação do Ni(0), este novo catalisador teve apenas sua superfície oxidada a NiO ao ser armazenado em ar. O NiO formado foi facilmente reduzido por hidrogênio a Ni(0) em condições brandas (75°C) se comparado ao NiO bulk (270-520°C). Os catalisadores bimetálicos de níquel-paládio foram sintetizados por uma reação de substituição galvânica com Pd(OAc)2 em um catalisador de Ni(0) suportado e por decomposição simultânea dos precursores organometálicos Ni(COD)2 e Pd2(dba)3 (dba = dibenzilideno acetona) em diferentes frações molares. Os catalisadores bimetálicos preparados por substituição galvânica não resultaram em estruturas core(Ni)-shell(Pd) como o esperado...

Investigação de tratamentos alternativos de fosfatização para eliminação do níquel e cromo hexavalente; Investigation of alternative phosphating treatments for nickel and hexavalent chromium elimination

Jazbinsek, Luiz Antônio Rossi
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 30/10/2014 PT
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362.1886%
O processo de fosfatização é amplamente utilizado na indústria de tratamento de superfície de metais, especialmente de placas de baixa espessura, melhorando a aderência entre a superfície do metal e o revestimento de tinta, e aumentando a durabilidade dos sistemas de pintura contra ataques corrosivos. Os fosfatos tricatiônicos contendo zinco, níquel e manganês são comumente aplicados em aço, e muito se discute sobre a substituição do níquel por outro elemento com o objetivo de obter um fosfato mais amigável ao meio ambiente, tanto em seus processos como para as pessoas envolvidas. O nióbio tem sido avaliado nesse sentido. Os impactos ambientais mais significativos dos fosfatos estão relacionados com a presença do níquel e do cromo hexavalente utilizado no processo, devido a exposição ao contato humano e a contaminação residual da água e do solo. Seguindo a linha de pesquisa que estudou a substituição do níquel por nióbio em camadas formadas sobre o aço carbono, o presente estudo avaliou e caracterizou camadas de fosfato contendo zinco, manganês e nióbio, formadas em aço galvanizado, comparando os resultados com o fosfato de zinco, manganês e níquel, bem como com o fosfato de zinco e manganês, sem a adição de nióbio. Embora o uso de cromo não seja recomendado mundialmente...

Protective effect of nickel chloride on superoxide damage: enhancement of CuZn superoxide dismutase affinity to the oxygen free radical.

Novelli, E. L.; Rodrigues, N. L.; Ribas, B. O.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 28-32
ENG
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The effect of nickel from soluble NiCl2 on Cu-Zn superoxide dismutase (SOD) activity, as well as on rate of nitro blue tetrazolium reduction, was studied in vitro since lipid peroxidation has been implicated in cell damage by nickel insoluble compounds, whose toxicity and carcinogenicity are well established. The physical and chemical nature of nickel compounds is one of the key determinations of its toxicity. Soluble nickel freely enter cells, but is just as readily excreted reducing the opportunity for production of lipid damage. Nickel from NiCl2 strongly activated SOD activity. In vitro addition of nickel chloride to a crude lung preparation altered the KM for SOD without changing the Vmax. Nickel chloride produced increased enzyme affinity to the substrate, because decreased (O2-) concentration that yields half-maximal velocity. The combination of nickel and SOD may contribute to stabilization of the particular conformation of SOD responsible for maximal catalytically activity.

Toxic mechanism of nickel exposure on cardiac tissue

Novelli, E. L B; Diniz, Y. S.; Machado, T.; Proença, V.; Tibiriçá, T.; Faine, L.; Ribas, B. O.; Almeida, J. A.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 177-187
ENG
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The incidence of cardiovascular disease has increased in the general population, and cardiac damage is indicated as one important cause of mortality. In addition, pollution and metal exposure have increased in recent years. For this reason, toxic effects of metals, such as nickel, and their relation to cardiac damage should be urgently established. Although free radical-mediated cellular damage and reactive oxygen species have been theorized as contributing to the nickel mechanism of toxicity, recent investigations have established that free radicals may be important contributors to cardiac dysfunction. However, there is little information on the effect of nickel exposure on markers of oxidative stress in cardiac tissue. Nickel exposure (Ni2+ 100 mg L-1 from NiSO4) significantly increased lipoperoxide and total lipid concentrations in cardiac tissue. We also observed increased serum levels of cholesterol (59%), lactate dehydrogenase (LDH-64%), and alanine transaminase (ALT-30%) in study animals. The biochemical parameters recovered to the control values with tocopherol intake (0.2 mg 200 g-1). Vitamin E alone significantly decreased the lipoperoxide concentration and increased superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities in the heart. Since no alterations were observed in catalase and GSH-Px activities by nickel exposure while SOD activities were decreased...

Hypersensitivity to conventional and to nickel-free orthodontic brackets

Pantuzo,Mariele Cristina Garcia; Zenóbio,Elton Gonçalves; Marigo,Helenice de Andrade; Zenóbio,Madelon Aparecida Fernandes
Fonte: Sociedade Brasileira de Pesquisa Odontológica - SBPqO Publicador: Sociedade Brasileira de Pesquisa Odontológica - SBPqO
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2007 EN
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The aim of this study was to evaluate the allergenic potential of orthodontic brackets, comparing the cutaneous sensitivity provoked by metals present in conventional metallic brackets to that provoked by brackets with a low concentration of nickel, known as "nickel-free". A sample was selected from 400 patients undergoing treatment in the orthodontic clinic of the Pontifical Catholic University of Minas Gerais (Belo Horizonte, MG, Brazil), in the period from the beginning of 2002 to the end of 2003. A cutaneous sensitivity patch test containing 5% nickel sulphate was used in 58 patients (30 males and 28 females), aged between 11 and 30, which were using fixed appliances with Morelli® brackets in both arches. In a second phase, 30 days later, a comparative test of cutaneous sensitivity was applied to the whole sample with two types of test specimens, in the form of a disc. Two alloys were tested: discs composed of the alloy used in the construction of conventional brackets and discs composed of a nickel-free alloy. The internal part of the forearm was chosen for testing, and 20 test specimens of each experiment (corresponding to the twenty brackets of a complete fixed appliance) were applied. Of the 58 patients evaluated, 16 patients were sensitive to the patch test with 5% nickel sulphate. Out of these 16 patients...

Complexes pinceurs de cobalt et de nickel : synthèse, caratérisation, réactivité

Lefèvre, Xavier
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
FR
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Plusieurs nouveaux complexes pinceurs de cobalt et de nickel ont été préparés avec le ligand pinceur de type POCOP : 2,6-(i-Pr2PO)2C6H4. Dans le cas du cobalt, une nouvelle voie de synthèse a été développée. Contrairement au cas du nickel, il s’agit ici de cobalt au degré d’oxydation +III. Les composés obtenus sont paramagnétiques. En outre, le dérivé bromé est instable à la lumière et se décompose en perdant un brome pour former le complexe pinceur de Co(II). La réactivité de ces complexes a été étudiée. Pour ce qui est du nickel, la catalyse de l’hydroamination a été élargie aux dérivés de l’acrylonitrile et aux amines aromatiques. En outre, la réaction d’hydroaryloxylation a été étudiée dans les mêmes conditions. Enfin, avec le 4-cyanostyrène et le cinnamonitrile, la formation d’amidines a été observée. Un complexe pinceur portant cette amidine a été isolé. Enfin, le cation réagit avec des anions fortement coordonnants tels le cyanure ou l’isocyanate. En outre, l’anion triflate peut être déplacé par l’eau, l’acrylonitrile et ses dérivés. Enfin, une réactivité particulière a été observée avec la morpholine, l’acétone et un mélange 1:1 aniline/triéthylamine.; A large variety of new POCOP pincer type complexes of cobalt and nickel have been prepared. All those complexes are based on the following POCOP pincer type ligand: 2...

The effects of temperature on nickel tocicity in goldfish (carassius auratus L.)

Norris, Stacey L.
Fonte: Brock University Publicador: Brock University
Tipo: Electronic Thesis or Dissertation
ENG
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Although it is widely assumed that temperature affects pollutant toxicity, few studies have actually investigated this relationship. Moreover, such research as has been done has involved constant temperatures; circumstances which are rarely, if ever, actually experienced by north temperate, littoral zone cyprinid species. To investigate the effects of temperature regime on nickel toxicity in goldfish (Carassius auratus L.), 96- and 240-h LCSO values for the heavy metal pollutant, nickel (NiCI2.6H20), were initially determined at 2DoC (22.8 mg/L and 14.7 mg/L in artificially softened water). Constant temperature bioassays at 10°C, 20°C and 30°C were conducted at each of 0, 240-h and 96-h LCSO nickel concentrations for 240 hours. In order to determine the effects of temperature variation during nickel exposure it was imperative that the effects of a single temperature change be investigated before addressing more complex regimes. Single temperature changes of + 10°C or -10°C were imposed at rates of 2°C/h following exposures of between 24 hand 216 h. The effects of a single temperature change on mortality, and duration of toxicant exposure at high and low temperatures were evaluated. The effects of fluctuating temperatures during exposure were investigated through two regimes. The first set of bioassays imposed a sinewave diurnal cycle temperature (20.±.1DOC) throughout the 10 day exposure to 240-h LeSO Ni. The second set of investigations approximated cyprinid movement through the littoral zone by imposing directionally random temperature changes (±2°C at 2-h intervals)...

The concentration of intracellular nickel in Haemophilus influenzae is linked to its surface properties and cell-cell aggregation and biofilm formation

Ng, J.; Kidd, S.
Fonte: Urban & Fischer Verlag Publicador: Urban & Fischer Verlag
Tipo: Artigo de Revista Científica
Publicado em //2013 EN
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Of the known proteins which use nickel as a co-factor, Haemophilus influenzae contains only urease and glyoxalase I (gloA). We have recently reported that this pathogen harbours a unique nickel uptake system (nikKLMQO-nimR). Unusually, the disruption of the nickel uptake system (nikQ or nimR mutants) resulted in cells that aggregated and formed an increased biofilm compared to the wild type cells. Using a gloA mutant strain and urease-specific inhibitor we showed that this phenotype is not due to the loss-of-function of these enzymes. By generating H. influenzae "resting cells" which are enzymatically inactive but maintain their structural integrity we have shown that the cell aggregation in the nikQ/nimR mutants is not due to the loss of enzymatic function. The nikQ mutant was unable to accumulate nickel but the addition of excess nickel did restore intracellular nickel levels and this resulted in the nikQ mutant returning to the wild type "free-living" phenotype; cells with no aggregation and no biofilm formation. We used a range of techniques which showed that the nikQ mutant possesses changes to its cell surface properties. The mutant was more negatively charged than wild type cells as well as being more hydrophobic. Analysis of the outer membrane constituents showed that there were molecular differences. Although the nikQ mutant appears to grow the same as its wild type cell we have shown that there is a change in the "lifestyle" of these nickel limited cells and this induces changes to the surface of the cell to promote cell-cell aggregation and biofilm formation.; JiaQi Ng and Stephen P. Kidd

Evaluating the respiratory bioaccessibility of nickel in soil through the use of a simulated lung fluid

Drysdale, M.; Bjorklund, K.L.; Jamieson, H.E.; Weinstein, P.; Cook, A.; Watkins, R.T.
Fonte: Springer Verlag Publicador: Springer Verlag
Tipo: Artigo de Revista Científica
Publicado em //2012 EN
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Simulated lung fluids are solutions designed to mimic the composition of human interstitial lung fluid as closely as possible. Analysis of mineral dusts using such solutions has been used to evaluate the respiratory bioaccessibility of various elements for which solubility in the lungs is a primary determinant of reactivity. The objective of this study was to employ simulated lung fluid analysis to investigate the respiratory bioaccessibility of nickel in soils. Current occupational guidelines in Australia regulate nickel compounds in terms of water solubility, though this may not be an accurate estimation of the total nickel that will dissociate in the lungs. Surface soils were collected from the city of Kalgoorlie in Western Australia, the site of an operational nickel smelter and metal mining activities. The fraction of the samples less than 10 μm was extracted from the soil, and it was this sub-10-μm fraction that was found to hold most of the total nickel present in the soil. The fine fraction was analyzed using a simulated lung fluid (modified Gamble's solution) to isolate the nickel phases soluble in the lungs. In addition, a sequential extraction was employed to compare the bioaccessible fraction to those dissolved from different binding forms in the soil. In all samples...

THE SELECTIVE SULPHIDATION AND PHYSICAL UPGRADING OF NICKEL FROM A NICKELIFEROUS LATERITIC ORE

HARRIS, CHRIS
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
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The processing of nickeliferous laterites to produce nickel metal is both complex and energy intensive. Since most laterites are found in remote regions, the capital costs for the infrastructure can exceed those for the process itself. The low temperature sulphidation of lateritic ores to produce an intermediate nickel concentrate for further processing offers a number of potential advantages, such as lower energy consumption and a relatively simple flowsheet. In this research, the sulphidation of a nickeliferous lateritic ore was investigated between the temperatures of 450-1100oC and sulphur additions of between 25-1000 kg of sulphur per tonne of ore. The experiments demonstrated that the nickel oxide within the ore can be selectively sulphidized to a nickel-iron sulphide. It was found that both the grade and the sulphidation degree largely depended upon the temperature and the sulphur additions, with temperatures above 550oC exhibiting the highest nickel sulphidation extents and grades. A DTA/TGA with mass spectrometer was used to further elucidate the nature of the phase transformations that occur upon heating of the ore, in the presence of sulphur. It was found that the Fe-Ni-S phase formed at low temperatures was submicron in nature and heating to temperatures of 1050oC-1100oC allowed for the growth of the sulphides to a d80 of up to 14 µm due to increased sulphide mobility...

Application of simulated lung fluid analysis to characterize the influence of smelter activity on the respiratory bioaccessibility of nickel-bearing soils in Kalgoorlie, Western Australia

Drysdale, Mallory Elizabeth Brennan
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado Formato: 5085581 bytes; application/pdf
EN; EN
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The city of Kalgoorlie in Western Australia has been labeled an “asthma hot spot” attributed to mining activity, prompting further investigation into toxic elements (Lee et al., 2006). Inhalation of nickel-bearing particles is a particular concern due to the presence of a nickel smelter 10km upwind of the city. The toxicological properties of nickel are well-documented, thus the primary objective is the characterization of phases identified as problematic in the lungs. To determine the smelter’s influence on nickel bioaccessibility in the soils throughout the city of Kalgoorlie, surface soil samples were taken from areas within the city and compared to soils near the smelter and outside the city, distant from the smelter. Soils were sieved to isolate the respirable fraction (<10um) potentially associated with lung disease and analyzed using a simulated lung fluid to determine the concentration of nickel soluble in the lungs. The soluble nickel represents the fraction that may be involved in allergic or asthmatic reactions, while the insoluble compounds may be of concern as some are carcinogenic. Further soil characterization was done using a six step sequential extraction and mineralogical analysis to identify nickel-bearing minerals. The influence of the smelter activity on nickel bioaccessibility in the soils within Kalgoorlie is low...

Monohalogénocyclopropanations stéréosélectives à l'aide de carbénoïdes de zinc, couplages croisés de cyclopropylsilanols, cyclisations d'iodures d'alkyle catalysées par le nickel

Bonhomme-Beaulieu, Louis-Philippe
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
FR
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Les cyclopropanes sont des unités qui sont très importantes en raison de leur présence dans de nombreux produits naturels, dans certaines molécules synthétiques ayant une activité biologique, ainsi que dans plusieurs intermédiaires synthétiques. Les travaux décrits dans cet ouvrage portent sur l’halogénocyclopropanation stéréosélective d’alcools allyliques en présence d’un ligand chiral stœchiométrique de type dioxaborolane et de carbénoïdes de zinc substitués dérivés de composés organozinciques et d’haloformes. Nous avons ainsi développé des conditions pour l’iodo-, la chloro- et la fluorocyclopropanation stéréosélective. Une étude mécanistique portant sur la nature des carbénoïdes alpha-chlorés et alpha-bromés a révélé qu’il y a un échange des halogènes portés par ces carbénoïdes. Lors de la chlorocyclopropanation, le carbénoïde le plus réactif (alpha-chloré) réagit de façon prédominante en vertu du principe de Curtin-Hammet. Les iodocyclopropanes énantioenrichis ont pu être fonctionnalisés via une réaction d’échange lithium-iode suivie du traitement avec des électrophiles, ou via une réaction de transmétallation au zinc suivie d’un couplage de Negishi. Ainsi...

Lung cancer risk associated with occupational exposure to nickel, chromium VI, and cadmium in two population-based case-control studies in Montreal.

Beveridge, Rachelle
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
EN
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Cancer du poumon associé à l’exposition au nickel, au chrome VI et au cadmium dans le milieu de travail utilisant deux études populationnelles cas-témoins à Montréal. Au début des années 1990, le nickel, le chrome VI et le cadmium ont été classés en tant qu’agents cancérigènes de classe 1 par le CIRC (Centre International de Recherche sur le Cancer). Cependant, les résultats des études ayant permis la classification de ces métaux n’ont pas toujours été reproduits, et d’importantes questions demeurent quant aux effets de ces métaux à de faibles niveaux d’exposition. Un plus grand nombre de recherches empiriques est donc nécessaire afin de réaffirmer la cancérogénicité de ces agents, et d’identifier les circonstances dans lesquelles ils peuvent être néfastes. L'objectif de cette étude était d'explorer la relation entre l’exposition à un des métaux (soit le nickel, le chrome VI, ou le cadmium) et les risques subséquents de développer un cancer du poumon chez des travailleurs provenant de différents milieux de travail qui sont exposés à ces métaux à de différents degrés. Deux études cas-témoins de base populationnelle menées à Montréal ont fourni les données nécessaires pour examiner la cancérogénicité de ces métaux. La première étude était menée entre 1979 et 1986 chez des hommes âgés de 35 à 70 ans ayant un cancer dans l’un de 19 sites anatomiques de cancer sélectionnés. La seconde étude était menée entre 1996 et 2001 chez des hommes et des femmes âgés de 35 à 75 ans...

Synthesis of nickel disilicide quantum dots in silicon dioxide films

Yoon, Jong-Hwan; Elliman, Robert
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
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Nickel disilicide (NiS2) quantum dots (QDs) have been grown in silicon-rich oxide (SiOx) films by either ion implanting with nickel or coating with an evaporated Ni film and annealing at 1100 °C. It is shown that both techniques produce well-defined sing

Investigation of bolometric and resistive properties of nickel oxide

Kumar, Shaurya
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
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This work investigates the properties of nickel oxide for use in microbolometric and resistive memory applications. For the uncooled infrared radiation detector industry, the current standard sensor materials are either very expensive, but very sensitive (vanadium oxide), or the other extreme of low cost, and low quality (amorphous silicon). Thus, a need arises for a medium-grade, medium-cost microbolometer sensitive material. The physical scaling limits of conventional charge-based non-volatile memory has progressed the semiconductor industry into searching for a new type of non-volatile memory device. Resistive random access memory (ReRAM) shows promise to fill this void, and nickel oxide presents itself as a potential forerunner in this market by demonstrating its ability to switch from a high resistance state to a low resistance state. A die with microbolometer devices and metal-insulator-metal (MIM) structures was designed and fabricated, with nickel oxide as the infrared-sensitive and resistance-switching material respectively. Two methods of obtaining nickel oxide were investigated - plasma oxidation and thermal oxidation. Ellipsometry, X-ray diffraction, transmission electron microscopy, and energy dispersive X-ray spectroscopy were used to study the films created using the two techniques. Thermally grown nickel oxide was used for the fabrication of the bolometer and MIM devices...

Macrocycle ligand modifications in the pursuit of nickel-oxygen complexes

Trujillo, Joliene Renee
Fonte: University of Delaware Publicador: University of Delaware
Tipo: Tese de Doutorado
Relevância na Pesquisa
364.07312%
Riordan, Charles; The utility of small molecules lies in the ability to alter the structure of the molecule and examine the spectroscopic characteristics as well as the reactivity of the complex. Small molecules are often used to probe mechanistic questions on much more complicated systems, such as enzymes. In 1996 a new form of superoxide dismutase was discovered which had nickel in the active site of the enzyme. This discovery sparked renewed interest in nickel-oxygen chemistry. Small molecules were used to probe different nickel-oxygen structure types and their spectroscopic characteristics, though complete understanding of the implications when altering the small molecules has yet to develop. This thesis addresses macrocycle ligand modifications, the varying ways of synthesizing nickel-oxygen complexes, and the reactivity of the nickel-oxygen adducts with exogenous substrates. The work presented herein, describes the synthesis and characterization of [Ni(tmcyclen)(CO)](OTf). Subsequent oxygen activation by [Ni(tmcyclen)(CO)](OTf) lead to the formation of ”side-on” nickel(III) peroxo complex as determined by electronic absorption spectroscopy, electron paramagnetic resonance spectroscopy, and mass spectroscopy. Alternatively...

Pincer ligand complexes for the study of nickel oxygen species

Klebon, Bryan D.
Fonte: University of Delaware Publicador: University of Delaware
Tipo: Tese de Doutorado
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Riordan, Charles G.; The catalytic oxidation of organic molecules in an environmentally friendly and cost effective manner represents a substantial challenge. One approach employed to address this challenge has been to draw inspiration from biological systems, which utilize base metal ions in a wide variety of catalytic reactions. The recent discovery of a nickel containing dioxygenase enzyme has triggered an interest in nickel based oxidation catalysis. This thesis addresses the synthesis of a variety of pincer ligand supported nickel complexes and their reactivity with dioxygen. Two pincer ligand systems were investigated, namely PCP and NCN pincer ligands. The synthesis and characterization of [PCPCy2Ni(OH2)]BF4, PCPCy2Ni(BF4), [PCPCy2Ni(CN-t-Bu)]BF4, and [PCPCy2Ni(CO)]BF4, are detailed, as well as attempts to reduce these complexes to give a NiI species. The strongly pi-accepting ligands were introduced in the hope that they would stabilize a NiI species and prevent disproportionation. The only discernible products of reduction attempts were colloidal nickel and starting material, suggesting that disproportionation occurs even in the presence of strongly pi-accepting ligands. Nickel complexes supported by the NCN pincer ligand system were also examined. The synthesis and characterization of [NCN(iPr)2Ph]NiBr is discussed. Reduction of [NCN(iPr)2Ph]NiBr with KC8 gives a bimetallic complex featuring a NiI-NiI bond. This bimetallic core is supported by two NCN ligands. While each ligand is bound in a mu-eta(2):eta(1) fashion...

Influence of Operation Parameters on Metal Deposition in Bright Nickel-plating Process

Sadiku-Agboola,O.; Sadiku,E.R.; Ojo,O.I.; Akanji,O.L.; Biotidara,O.F.
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2011 EN
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Bright nickel deposits were electrolytically applied on steel in the nickel Watts bath. The effect of some operational parameters on metal deposition in bright nickel plating was investigated. The investigation indicated that the weight of bright nickel deposited on metal during the process of electroplating was affected by plating temperature, voltage, current density, plating bath pH and plating time. The study established that the deposition of best bright nickel was obtained at a plating temperature of 56 ºC, current density of 6 A/dm² and plating time of 18 minutes. Brightener is used in applications requiring outstanding appearance with minimum thickness of applied nickel plating. It can also be used for heavy deposit applications because it exhibits unparalleled ductility and low stress. Brightener was used in this study to determine the best nickel plating in the process. Boric acid was added for fixing the bath pH. The compositions of the brightener and nickel solution used are included in the text.