5 results on '"Wiebeck, Hélio"'
Search Results
2. Panorama da Pesquisa Acadêmica Brasileira em Nanocompósitos Polímero/Argila e Tendências para o Futuro
- Author
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Anadão, Priscila, Wiebeck, Hélio, and Valenzuela-Díaz, Francisco R.
- Subjects
Nanocomposite ,Nanocompósito ,argila ,polymer ,clay ,polímero - Abstract
A pesquisa em nanocompósitos polímero/argila foi iniciada pela Toyota no final dos anos 80. A partir deste marco, a comunidade científica mundial voltou sua atenção para este tipo de material graças às propriedades mecânicas, químicas e térmicas avançadas em comparação com os compósitos tradicionais. Não foi diferente no Brasil, tal atenção pode ser comprovada pelos inúmeros trabalhos científicos sobre nanocompósitos que começaram a despontar no início do século XXI. Assim, o presente artigo objetiva, após discorrer sobre as definições que concernem nanocompósitos polímero/argila, apresentar as pesquisas científicas brasileiras em nanocompósitos de polímeros de uso geral, de polímeros de engenharia e de outros tipos de polímeros, relacionando-os com o método de produção empregado, morfologia final e propriedades decorrentes da formação de nanocompósitos. Por fim, o mapa da pesquisa brasileira em nanocompósitos polímero/argila e sua perspectiva para o futuro são apresentados. The research on polymer/clay nanocomposites was initiated by Toyota in the late 80s. From then on, the world scientific community has turned its attention to this type of material due to the enhanced mechanical, chemical and thermal properties in comparison to traditional composites. In Brazil, it was not different, as can be seen from the countless scientific works on nanocomposites which have emerged in the early 21th century. The aim thus is, after discussing the definitions related to the polymer/ clay nanocomposites, to show Brazilian scientific works on the general use of plastics, engineering plastics and other types of polymers, correlating them with their production method, final morphology and resulting properties. Finally, a map of the Brazilian research into polymer/clay nanocomposites and their future perspective are presented.
- Published
- 2011
3. Montmorillonite as a component of polysulfone nanocomposite membranes
- Author
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Anadão, Priscila, Sato, Laís Fumie, Wiebeck, Hélio, and Valenzuela-Díaz, Francisco Rolando
- Subjects
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MONTMORILLONITE , *COMPOSITE materials , *SULFONES , *ARTIFICIAL membranes , *SOLUTION (Chemistry) , *DISPERSION (Chemistry) - Abstract
Abstract: Nanocomposite membranes containing polysulfone (PSf) and sodium montmorillonite from Wyoming (MMT) were prepared by a combination of solution dispersion and the immersion step of the wet-phase inversion method. The purpose was to study the MMT addition with contents of 0.5 and 3.0 mass% MMT in the preparation of nanocomposite membranes by means of morphology, thermal, mechanical and hydrophilic properties of nanocomposite membranes and to compare these properties to the pure PSf membrane ones. Small-angle X-ray diffraction patterns revealed the formation of intercalated clay mineral layers in the PSf matrix and TEM images also presented an exfoliated structure. A good dispersion of the clay mineral particles was detected by SEM images. Tensile tests showed that both elongation at break and tensile strength of the nanocomposites were improved in comparison to the pristine PSf. The thermal stability of the nanocomposite membranes, evaluated by onset and final temperatures of degradation, was also enhanced. The hydrophilicity of the nanocomposite membranes, determined by water contact angle measurements, was higher; therefore, the MMT addition was useful to produce more hydrophilic membranes. [Copyright &y& Elsevier]
- Published
- 2010
- Full Text
- View/download PDF
4. Montmorillonite/carbon nanocomposites prepared from sucrose for catalytic applications
- Author
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Anadão, Priscila, Hildebrando, Edemarino Araújo, Pajolli, Ivan Luiz Rocchetti, de Oliveira Pereira, Kleberson Ricardo, Wiebeck, Hélio, and Valenzuela Díaz, Francisco Rolando
- Subjects
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MONTMORILLONITE catalysts , *CARBON , *NANOCOMPOSITE materials , *SUCROSE , *ADSORPTION (Chemistry) , *THERMOGRAVIMETRY , *X-ray diffraction , *SCANNING electron microscopy , *SURFACE chemistry , *FOURIER transform infrared spectroscopy - Abstract
Abstract: Sucrose was used to prepare montmorillonite/carbon nanocomposites by calcination in a reduced atmosphere. The aim was to investigate the changes derived from varying the clay and sucrose content in the resulting material and to change the adsorption properties to evaluate its potential to be used in catalytic applications. X-ray diffraction patterns revealed the formation of an intercalated nanostructure composed of carbon-filled clay mineral layers, which was confirmed by the Fourier transform infrared spectra and thermogravimetry curves. Differences in composition and texture surface were detected by scanning electron microscopy images and were supported by viscosity measurements. These measurements were helpful in understanding why the sample prepared with the highest sucrose content presented the lowest gasoline and methylene blue adsorption results and why the highest adsorption properties were attributed to the sample with the highest clay content. Moreover, BET and BJH studies allowed understanding oleic acid catalytic conversion. Finally, a water flux simulation test was performed to determine the mechanical resistance in comparison to an activated carbon. It was found that the nanocomposites were more resistant, supporting their use in catalytic applications for a longer period of time. [Copyright &y& Elsevier]
- Published
- 2011
- Full Text
- View/download PDF
5. Obtenção em escala de bancada de um nanocompósito de pseudoboemita com nylon 6,12
- Author
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Nakashima, Marcela, Miranda, Leila Figueiredo de, Wiebeck, Hélio, and Munhoz Junior, Antonio Hortêncio
- Subjects
nanocomposite ,nanocompósito ,nylon 6,12 ,pseudoboemita ,seudobohemite ,ENGENHARIAS::ENGENHARIA DE MATERIAIS E METALURGICA [CNPQ] - Abstract
This work is about a nanocomposite compound made with a ceramic material and a polymer used as matrix. The purpose of this work is evaluating the influence of the addition of the nanoparticles of the ceramic material in the nanocomposite. The ceramic material used was pseudoboehmite obtained by sol-gel process The pseudoboehmite was obtained from aluminum nitrate and ammonium hydroxide using poly-vinyl alcohol during the precipitation. The polymer nylon 6,12 has used in this process. Mechanical properties also will be analyzed: tensile strength, compression strength, impact thoughness, melt flow, SHORE hardness and density. The results has showed that increased values of the mechanical properties, was compared with the material without adding nanoparticles. O presente trabalho trata-se do estudo de um nanocompósito à base de cerâmica (fase dispersa) + polímero (matriz), que tem como objetivo de analisar as propriedades mecânicas nanocompósito em relação às propriedades mecânicas do mesmo polímero sem a adição das nanopartículas de material cerâmico. As nanopartículas utilizadas foram de pseudoboemita, obtida pelo processo sol-gel. Na obtenção da pseudoboemita utilizou-se nitrato de alumínio como precursor e hidróxido de amônio com a adição de álcool polivinílico durante a precipitação. A matriz polimérica utilizada foi o nylon 6,12. As propriedades mecânicas avaliadas foram: resistência à tração, resistência a compressão e resistência ao impacto, índice de fluidez, dureza SHORE e densidade. Os resultados mostram que houve um aumento nos valores de propriedades mecânicas do material obtido em relação ao polímero sem adição de nanopartículas.
- Published
- 2009
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