Noble Metals
Mostrando 1-12 de 17 artigos, teses e dissertações.
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1. Determination of gold by high-resolution continuum source atomic absorption spectrometry with chemical vapor generation
Avaliou-se o potencial analítico da geração de vapor químico e da espectrometria de absorção atômica com fonte contínua de alta resolução com atomização em tubo de quartzo na determinação de ouro. As espécies voláteis de ouro foram formadas pela reação com tetraidroborato(III) de sódio na presença de ácido clorídrico. Investigou-se a in
J. Braz. Chem. Soc.. Publicado em: 2013-05
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2. Processamento de placas de circuito impresso de equipamentos eletroeletrônicos de pequeno porte
A hydrometallurgical process applicable to printed circuit boards of small electrical and electronic devices was developed. This involved three leaching steps (60 ºC, 2 h): 6 mol L-1 NaOH, 6 mol L-1 HCl and aqua regia. NaOH removed the resin and flame retardant that covered the circuit boards. HCl dissolved the most electropositive metals and a small amount
Quím. Nova. Publicado em: 2013
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3. Heavy metals in vegetables and potential risk for human health
Ingestion of vegetables containing heavy metals is one of the main ways in which these elements enter the human body. Once entered, heavy metals are deposited in bone and fat tissues, overlapping noble minerals. Slowly released into the body, heavy metals can cause an array of diseases. This study aimed to investigate the concentrations of cadmium, nickel, l
Scientia Agricola. Publicado em: 2012-02
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4. O efeito da desativação térmica nas propriedades oxirredutoras e na atividade catalítica de catalisadores CZ e Pd-CZ
Automotive catalyst, using in Brazil since 1992, is a essential technology for vehicular emissions control. Noble metals are the active phase of these catalysts, and cerium zirconium mixed oxides (CZ), responsibles for the oxygen storage capacity (OSC), one of the most important aspect for the operational performance of the catalyst. In this context, the oxi
Química Nova. Publicado em: 2012
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5. Avaliação eletroquímica do desempenho de células termogalvânicas empregando líquidos iônicos como meio eletrolítico e alumínio como eletrodos
Thermogalvanic cells are thermoconverter electrochemical devices where two electrodes, not necessarily chemically identical or reversible, are held at different temperatures. The temperature difference between the electrodes creates a potential difference that can be used to drive current to an external circuit. Thus, direct conversion from thermal energy to
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 2011
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6. Estudo de nanofios metálicos por primeiros principios
In the present work, we investigate electronic and structural properties of nanowires based on noble metals (Au,Ag,Pt,Pd) and mid-series 4d and 5d transition metals (W,Mo,Ta,Nb). We employ an ab initio methodology implemented in the SIESTA package, based in the Kohn-Sham formulation of density functional theory (DFT). The generalized gradient approximation (
Publicado em: 2010
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7. Diagnose de microbiólitos metálicos em espécies vegetais endêmicas em solos de rochas ultramáficas por microscopia eletrônica de varredura
The aim of this paper is to investigate by SEM the presence of crystalline forms of noble metals in dehydrated tissues of Scutia buxifolia (Rhamnaceae), Scoparia montevidensis (Scrophulariaceae) and Adiantopsis cf. chlorophylla (Pteridaceae), a endemic vegetation on ultramafic soils from Pedras Pretas, São Sepé, southermost Brazil. Chemical composition of
Publicado em: 2010
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8. Estudo das características morfológicas texturais e estruturais dos catalisadores automotivos, síntese e caracterização de filmes alternativos
The structural, morphological and textural changes of new and used automotive catalysts heated at temperatures between 500 and 1000°C were investigated. The catalysts were thermally characterized on simultaneous thermogravimetric and differential thermal analysis (TG-DTA) equipment performed in air and N2. Morphological changes were observed by scanning ele
Publicado em: 2010
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9. Nanoparticulas metalicas anisotropicas : mecanismos de formação e aplicações opticas / Anisotropic metal nanoparticles : formation mechanisms and optical applications
Noble metal nanoparticles have attracted a recent renewed interest due to the new scientific and technological applications exploiting their unique optical properties. At nanometric scale, it is well known that the optical response of metals, related to the excitation of surface plasmons, strongly depends not only on the size of the particles but also on the
Publicado em: 2008
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10. Catalisadores à base de Cu, Co ou Fe trocados ou suportados em zeólita USY avaliação na redução de NO com CO
The emissions of the nitrogen oxides (NOx) must be hardly reduced in the next years. The catalytic reduction of NO with CO is one of the possible processes with potential to be able to transform those oxides in N2. In that process, supported noble metals have been the most used, however, their low stability in the presence of water steam or SO2, have led to
Publicado em: 2008
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11. Perovskitas contendo lantânio, ferro e cobalto - melhoramento de propriedades texturais via síntese por nanomoldagem e avaliação como catalisadores na redução de NO com CO
Mixed oxides with perovskite structure have high potential as catalysts in gas depollution processes and particularly in the abatement of nitrogen oxides (NOx). Such solids could be considered as a promising alternative for the replacement of noble metals based catalysts, whose use is predominant. Great flexibility of composition, easy synthesis, low cost an
Publicado em: 2008
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12. Preparation and characterization of mixed modified electrodes used in electrocatalytic hydrogenation of organic substrates / Preparação e caracterização de eletrodos modificados mistos e seu uso em hidrogenação eletrocatalítica de substratos orgânicos
This thesis describes the preparation of new modified electrodes (MEs) using the method of noble metal particles deposition like nickel, palladium and platinum in the surface of commum metals particles as cooper and iron. This new electrodes were denominated mixed MEs, and can show different caractheristics and present higher efficiency than others already s
Publicado em: 2006