Navegação Periódicos - Artigos por autor "9697"

Classificar por: Ordenar: Resultados:

  • IPEN-DOC 26862

    GARCIA, PAULO R.A.F.; PRYMAK, OLEG; GRASMIK, VIKTORIA; PAPPERT, KEVIN; WLYSSES, WAGNER; OTUBO, LARISSA ; EPPLE, MATTHIAS; OLIVEIRA, CRISTIANO L.P.. An in situ SAXS investigation of the formation of silver nanoparticles and bimetallic silver–gold nanoparticles in controlled wet-chemical reduction synthesis. Nanoscale Advances, v. 2, n. 1, p. 225-238, 2020. DOI: 10.1039/c9na00569b

    Abstract: We present a study on the formation of silver (Ag) and bimetallic silver–gold (AgAu) nanoparticlesmonitored by in situ SAXS as well as by ex situ TEM, XRD and UV-vis analysis in a flow reactor at controlled reaction temperature. The formation mechanism of the nanoparticles is derived from the structural parameters obtained from the experimental data. The evolution of the average particle size of pure and alloyed nanoparticles shows that the particle growth occurs initially by a coalescence mechanism. The later growth of pure silver nanoparticles is well described by Ostwald ripening and for the alloyed nanoparticles by a process with a significantly slower growth rate. Additionally, the SAXS data of pure silver nanoparticles revealed two major populations of nanoparticles, the first one with a continuous crystal growth to a saturation plateau, and the second one probably with a continuous emergence of small new crystals. The particle sizes obtained by SAXS agree well with the results from transmission electron microscopy and X-ray diffraction. The present study demonstrates the capability of an in situ investigation of synthesis processes using a laboratory based SAXS instrument. Online monitoring of the synthesis permitted a detailed investigation of the structural evolution of the system.

    Palavras-Chave: nanoparticles; small angle scattering; x-ray diffraction; silver; bimetals; gold; monte carlo method; nanostructures; alloys

    Icon

  • IPEN-DOC 25853

    PINHEIRO, ANDRE L.G.; CARMO, JOSE V.C. do; CARVALHO, DAVI C.; OLIVEIRA, ALCINEIA C.; RODRIGUEZ-CASTELLON, ENRIQUE; TEHUACANERO-CUAPA, SAMUEL; OTUBO, LARISSA ; LANG, ROSSANO. Bio-additive fuels from glycerol acetalization over metals-containing vanadium oxide nanotubes (MeVOx-NT in which, Me=Ni, Co, or Pt). Fuel Processing Technology, v. 184, p. 45-56, 2019. DOI: 10.1016/j.fuproc.2018.11.008

    Abstract: The biodiesel production has led to a drastic surplus of glycerol and catalytic conversion of glycerol into valueadded products is of great industrial importance. Thus, the acetalization of glycerol with ketone or aldehydes allows the glycerol transformation into bio–additive fuels. In this work, metals-containing vanadium oxides nanotubes (MeVOx NT in which, Me=Co, Pt or Ni) have been synthesized with additional internal porosity and tested in the acetalization of glycerol with acetone (AG) for valuable biofuels production. The catalysts showed remarkable performances in the AG reaction. Furthermore, by variation of the composition, catalyst loading and temperature and using distinct substrates (butyraldehyde, furfuraldehyde and benzaldehyde), NiVOxNT is active, being very selective to solketal and reciclable for 4 times in the AG reaction. On the contrary, pure VOx NT easily deactivated due to the structure agent removal during the reaction, which promote the collapse of the tubular structure. The CoVOxNT and PtVOxNT catalysts did not exhibit such a stable structure and easily deactivated in the reaction due to leaching of the metals oxides during the AG.

    Palavras-Chave: biodiesel fuels; glycerol; nanotubes; vanadium oxides; biofuels; acetates; catalysts; acetone

    Icon

  • IPEN-DOC 26873

    SANTOS, DOUGLAS C.; GOES, JOÃO M.R.; SOUZA, VIVIANE C. de; BISPO, DIEGO F.; OTUBO, LARISSA ; ANDRADE, GEORGE R.S.; CAMARGO, ZAINE T.; SANTOS, EULER A. dos. Green synthesis of silver nanostructures with amino acid-modified Pluronic F127 for antibacterial applications. Applied Surface Science, v. 505, p. 1-12, 2020. DOI: 10.1016/j.apsusc.2019.144449

    Abstract: The aim of this work was to evaluate the use of amino acid-functionalized Pluronic F127 derivatives in the synthesis of silver nanostructures (SNS), such as nanoparticles (SNP) and nanoclusters (SNC). Herein, glycine, Lalanine, and DL-alanine were used to functionalize poly(ethylene oxide) (PEO) end groups from the polymer chain via an esterification pathway. The esterified polymers were used for reducing and stabilizing SNS by a hydrothermal or a photo-assisted route (using a UVA light). The functionalized polymers were characterized by FTIR and the obtained SNS were characterized by UV–vis spectroscopy and TEM, which showed that the SNS obtained by the hydrothermal route are predominantly spherical, whereas those obtained by photo-assisted method give rise to rods and prisms. Kinetic studies showed that alanine and glycine form particles with different rates and that the different enantiomers (L and DL) influence the size and shape of SNS. The nanoparticles obtained by the two routes had their antibacterial efficiency tested against S. aureus by the Agar well diffusion method.

    Palavras-Chave: nanoparticles; silver; nanostructures; pluronics; synthesis; antibiotics; amino acids; alanines; reduction; photochemistry

    Icon

  • IPEN-DOC 26664

    CAMPOS, ALEX C.; PAES, SUANE C.; CORREA, BRUNO S.; CABRERA-PASCA, GABRIEL A.; COSTA, MESSIAS S.; COSTA, CLEIDILANE S.; OTUBO, LARISSA ; CARBONARI, A.W. . Growth of long ZnO nanowires with high density on the ZnO surface for gas sensors. ACS Applied Nano Materials, v. 3, n. 1, p. 175-185, 2020. DOI: 10.1021/acsanm.9b01888

    Abstract: Among the various approaches to grow semiconducting oxide nanowires, the thermal oxidation procedure is considered a simple, efficient, and fast method that allows the synthesis of micro and nanostructured arrangements with controlled size and morphology. In the work reported in this paper, long ZnO nanowires were synthesized on the surface of oxidized high-purity Zn foils by heating in air at different rates and temperatures. The size and morphology investigated by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) for a sample heated at 620 °C with heating rate of 20 °C/min reveal the growth of long ZnO nanowires with length of ∼50 μm and average diameter of 74 nm grown along the ⟨112̅0⟩ direction with high population density. Results with different heating rates indicates that this parameter is determinant in tuning the size, morphology, and population density of nanowires. X-ray diffraction (XRD) shows patterns for both ZnO and metallic Zn with preferential orientation, whereas perturbed angular correlation (PAC) measurements using 111In(111Cd) probe nuclei indicate that probe nuclei occupy only Zn sites in the preferential oriented metallic zinc. However, for samples submitted to high-temperature heating (820 and 1000 °C), XRD yields only the ZnO pattern and, amazingly, PAC continues showing probe nuclei only at metallic Zn sites indicating the presence of thin regions of highly oriented Zn trapped between grains of ZnO. Moreover, this strong preference of indium atoms (of parent radioactive 111In) here revealed helps to understand the oxidation mechanism and the growth of the nanowires.

    Palavras-Chave: zinc oxides; nanowires; electric fields; oxidation; temperature gradients; x-ray diffraction; thermal analysis; transmission electron microscopy

    Icon

  • IPEN-DOC 26481

    ARAUJO, JESUINA C.S.; OTON, LAIS F.; OLIVEIRA, ALCINEIA C.; LANG, ROSSANO; OTUBO, LARISSA ; BUENO, JOSE M.C.. On the role of size controlled Pt particles in nanostructured Pt-containing Al2O3 catalysts for partial oxidation of methane. International Journal of Hydrogen Energy, v. 44, n. 50, p. 27329-27342, 2019. DOI: 10.1016/j.ijhydene.2019.08.176

    Abstract: The effect of the Pt loadings and particles sizes on the stability of Pt(x wt%)/Al2O3 catalysts were investigated in the partial oxidation of methane (POM) reaction. The Al2O3 support was prepared by sol-gel method and different Pt loadings, varying from 0.5 to 2.0 wt% were incorporated to alumina through the incipient wetness impregnation method. The physicochemical features of the catalysts were determined by XRD, ICP-OES, Nitrogen-sorption, UVeVisible, H2-TPR, CO-DRIFTS, SEM-EDS, XPS and HRTEM techniques. The metal dispersion was evaluated in the cyclohexane dehydrogenation reaction. Lower Pt loadings resulted in well dispersed Pto nanoparticles with an enhanced activity in cyclohexane dehydrogenation and POM reactions. With increasing Pt loading to 2.0 wt%, the Pt nanoparticles of the Pt(2.0 wt%)/Al2O3 showed a methane conversion of 63% in 24 h of time on stream, and the catalyst was very selective to H2 and CO. Based on the HRTEM, XPS and Raman spectroscopy techniques, an increment in the Pt loadings evidenced an enrichment of Pto clusters on the surface, however, no heavy carbon deposits formation was observed.

    Palavras-Chave: methane; oxidation; aluminium oxides; platinum; nanostructures; catalysts; carbon

    Icon

  • IPEN-DOC 27128

    VIEIRA, LAÍS H.S.; SABINO, CARLA M.S.; SOARES JÚNIOR, FRANCISCO H.; ROCHA, JANAINA S.; CASTRO, MANUELA O.; ALENCAR, RAFAEL S.; COSTA, LUELC S. da; VIANA, BARTOLOMEU C.; PAULA, AMAURI J. de; SOARES, JOAO M.; SOUZA FILHO, ANTONIO G.; OTUBO, LARISSA ; FECHINE, PIERRE B.A.; GHOSH, ANUPAMA; FERREIRA, ODAIR P.. Strategic design of magnetic carbonaceous nanocomposites and its application as multifunctional adsorbent. Carbon, v. 161, p. 758-771, 2020. DOI: 10.1016/j.carbon.2020.01.089

    Abstract: Magnetic carbonaceous nanocomposites (MCN) were prepared by hydrothermal carbonization (HTC) of a carbohydrate in the presence of Fe3þ, followed by thermal treatment with KOH for simultaneous activation and magnetization. The precursor formed (IOCN) in the HTC process contained iron oxide nanoparticles encapsulated in the hydrochar matrix. The thermochemical parameters of the activation (temperature and IOCN/KOH mass-ratio) were varied to achieve an increase of the specific surface area along with formation of magnetic phases in MCN compared to IOCN. Activation temperature was found to be responsible for the structural and morphological properties of the MCNs whereas the IOCN/KOH mass-ratio controlled the porosity. The magnetic properties of the MCNs originated from the formation of Fe3O4 and Fe0 phases, which are encapsulated in the carbonaceous material. The MCNs were tested for adsorption of methylene blue (MB) dye, followed by magnetic separation. The MCN, produced in the optimized conditions, showed a specific surface area of 766 m2 g 1, magnetization of 8 emu g 1 and a MB adsorption capacity of 570 mg g 1. Detailed kinetic and isotherm studies of MB adsorption were also performed. The methodology of simultaneous activation and magnetization to generate MCNs, presented here, could be extended to obtain new multifunctional carbon-based nanocomposite adsorbent starting from different biomasses.

    Palavras-Chave: nanocomposites; carbonaceous materials; magnetic materials; magnetic fields; iron oxides; hydrothermal systems; adsorbents; carbon

    Icon

  • IPEN-DOC 26448

    ARAUJO, JESUINA C.S.; OTON, LAIS F.; BESSA, BRUNO; NETO, ANTONIO B.S.; OLIVEIRA, ALCINEIA C.; LANG, ROSSANO; OTUBO, LARISSA ; BUENO, JOSE M.C.. The role of Pt loading on La2O3-Al2O3 support for methane conversion reactions via partial oxidation and steam reforming. Fuel, v. 254, p. 1-15, 2019. DOI: 10.1016/j.fuel.2019.115681

    Abstract: The effects of Pt loadings on the catalytic performance of the La2O3-Al2O3-supported Pt nanoparticles are investigated during the partial oxidation (POM) and steam reforming of methane (SRM). From analyses of XRD, UV–Vis, TPR, CO-DRIFTS, XPS, Raman spectroscopy, cyclohexane dehydrogenation reaction, Pt surface species and their dispersions were dully observed. The good degrees of interaction between Pt nanoparticles and lanthana species in the support gave robust catalysts in POM, evidenced by XPS and TEM for low Pt loadings. Arrhenius plots for SRM showed an apparent activation energy of 70 kJ mol−1 for all Pt(x wt%)/Al2O3-La2O3 catalysts. An enrichment of the Pt species at loadings superior to 0.5 wt% resulted in Pt nanoparticles weakly interacting with the La2O3-Al2O3 support and the consequent sintering of the particles in SRM and POM reactions. On the contrary, best catalytic results and a more stable performance during POM in 24 h on stream was observed, when dispersing a 0.5 wt% of Pt on the support. A strong interaction between the PtOx species and the support was crucial for La2O3 preserve the high dispersion of the Pt entities. This favored the reactivity of surface oxygen species coming from LaPtOx[Pto]n. Indeed, this chemical entity was located on the surface of the solid, at the periphery of Pto particles, being further converted into La2PtOx[Pto]n−1. The decomposition of CH4 to CO and H2 as well as the coke gasification on the accessible Pt sites gave better conversions for Pt(0.5 wt%)/Al2O3- La2O3 compared with the other solids with higher Pt loadings.

    Palavras-Chave: nanoparticles; surfaces; particles; lanthanum oxides; catalysts; aluminium oxides; oxidation; steam reformer processes

    Icon

A pesquisa no RD utiliza os recursos de busca da maioria das bases de dados. No entanto algumas dicas podem auxiliar para obter um resultado mais pertinente.

É possível efetuar a busca de um autor ou um termo em todo o RD, por meio do Buscar no Repositório , isto é, o termo solicitado será localizado em qualquer campo do RD. No entanto esse tipo de pesquisa não é recomendada a não ser que se deseje um resultado amplo e generalizado.

A pesquisa apresentará melhor resultado selecionando um dos filtros disponíveis em Navegar

Os filtros disponíveis em Navegar tais como: Coleções, Ano de publicação, Títulos, Assuntos, Autores, Revista, Tipo de publicação são autoexplicativos. O filtro, Autores IPEN apresenta uma relação com os autores vinculados ao IPEN; o ID Autor IPEN diz respeito ao número único de identificação de cada autor constante no RD e sob o qual estão agrupados todos os seus trabalhos independente das variáveis do seu nome; Tipo de acesso diz respeito à acessibilidade do documento, isto é , sujeito as leis de direitos autorais, ID RT apresenta a relação dos relatórios técnicos, restritos para consulta das comunidades indicadas.

A opção Busca avançada utiliza os conectores da lógica boleana, é o melhor recurso para combinar chaves de busca e obter documentos relevantes à sua pesquisa, utilize os filtros apresentados na caixa de seleção para refinar o resultado de busca. Pode-se adicionar vários filtros a uma mesma busca.

Exemplo:

Buscar os artigos apresentados em um evento internacional de 2015, sobre loss of coolant, do autor Maprelian.

Autor: Maprelian

Título: loss of coolant

Tipo de publicação: Texto completo de evento

Ano de publicação: 2015

Para indexação dos documentos é utilizado o Thesaurus do INIS, especializado na área nuclear e utilizado em todos os países membros da International Atomic Energy Agency – IAEA , por esse motivo, utilize os termos de busca de assunto em inglês; isto não exclui a busca livre por palavras, apenas o resultado pode não ser tão relevante ou pertinente.

95% do RD apresenta o texto completo do documento com livre acesso, para aqueles que apresentam o significa que e o documento está sujeito as leis de direitos autorais, solicita-se nesses casos contatar a Biblioteca do IPEN, bibl@ipen.br .

Ao efetuar a busca por um autor o RD apresentará uma relação de todos os trabalhos depositados no RD. No lado direito da tela são apresentados os coautores com o número de trabalhos produzidos em conjunto bem como os assuntos abordados e os respectivos anos de publicação agrupados.

O RD disponibiliza um quadro estatístico de produtividade, onde é possível visualizar o número dos trabalhos agrupados por tipo de coleção, a medida que estão sendo depositados no RD.

Na página inicial nas referências são sinalizados todos os autores IPEN, ao clicar nesse símbolo será aberta uma nova página correspondente à aquele autor – trata-se da página do pesquisador.

Na página do pesquisador, é possível verificar, as variações do nome, a relação de todos os trabalhos com texto completo bem como um quadro resumo numérico; há links para o Currículo Lattes e o Google Acadêmico ( quando esse for informado).

ATENÇÃO!

ESTE TEXTO "AJUDA" ESTÁ SUJEITO A ATUALIZAÇÕES CONSTANTES, A MEDIDA QUE NOVAS FUNCIONALIDADES E RECURSOS DE BUSCA FOREM SENDO DESENVOLVIDOS PELAS EQUIPES DA BIBLIOTECA E DA INFORMÁTICA.

O gerenciamento do Repositório está a cargo da Biblioteca do IPEN. Constam neste RI, até o presente momento 20.950 itens que tanto podem ser artigos de periódicos ou de eventos nacionais e internacionais, dissertações e teses, livros, capítulo de livros e relatórios técnicos. Para participar do RI-IPEN é necessário que pelo menos um dos autores tenha vínculo acadêmico ou funcional com o Instituto. Nesta primeira etapa de funcionamento do RI, a coleta das publicações é realizada periodicamente pela equipe da Biblioteca do IPEN, extraindo os dados das bases internacionais tais como a Web of Science, Scopus, INIS, SciElo além de verificar o Currículo Lattes. O RI-IPEN apresenta também um aspecto inovador no seu funcionamento. Por meio de metadados específicos ele está vinculado ao sistema de gerenciamento das atividades do Plano Diretor anual do IPEN (SIGEPI). Com o objetivo de fornecer dados numéricos para a elaboração dos indicadores da Produção Cientifica Institucional, disponibiliza uma tabela estatística registrando em tempo real a inserção de novos itens. Foi criado um metadado que contém um número único para cada integrante da comunidade científica do IPEN. Esse metadado se transformou em um filtro que ao ser acionado apresenta todos os trabalhos de um determinado autor independente das variáveis na forma de citação do seu nome.

A elaboração do projeto do RI do IPEN foi iniciado em novembro de 2013, colocado em operação interna em julho de 2014 e disponibilizado na Internet em junho de 2015. Utiliza o software livre Dspace, desenvolvido pelo Massachusetts Institute of Technology (MIT). Para descrição dos metadados adota o padrão Dublin Core. É compatível com o Protocolo de Arquivos Abertos (OAI) permitindo interoperabilidade com repositórios de âmbito nacional e internacional.

1. Portaria IPEN-CNEN/SP nº 387, que estabeleceu os princípios que nortearam a criação do RDI, clique aqui.


2. A experiência do Instituto de Pesquisas Energéticas e Nucleares (IPEN-CNEN/SP) na criação de um Repositório Digital Institucional – RDI, clique aqui.