Spatial arrangement of fibrils in concentrated aqueous sols of fibrillar pseudoboehmite

Spatial arrangement of fibrils in concentrated aqueous sols of fibrillar pseudoboehmite

Autor Faria, F. P. Google Scholar
Santos, P. S. Google Scholar
Santos, H. S. Google Scholar
Instituição Universidade Federal de São Paulo (UNIFESP)
Universidade de São Paulo (USP)
Resumo The particle size, aggregation state and spatial arrangements of the particles in concentrated sols of boehmite and of fibrillar pseudoboehmite are important parameters for determining the final properties of powders of gamma-Al2O3 for use as catalysts, adsorbents, coatings and alumina derived materials of desired porosity and mechanical strength. However, these parameters are very difficult to evaluate, even qualitatively, in concentrated sols especially by conventional transmission electron microscopy. in this paper, we report the use of freeze-etching and critical point drying methods applied to transmission and scanning electron microscopy to describe the spatial organization of fibrils in concentrated aqueous sols of pseudoboehmite. for this purpose, a series of mono-, two- and three-layer sols of fibrillar pseudoboehmite containing 70 g/l of AlOOH were produced by reaction of aluminum powder with aqueous solution of acetic acid. A three-dimensional interwoven organization of short, single fibrils was observed in the mono-layer sol. Similar arrangement was seen in the upper layer of two- or three-layer sols, although in these sols, the fibrils are long and aggregate-forming thin bundles. in the bottom layer, the fibrils are aggregated in thick bundles aligned parallel to their lengths and forming plates ordered inside the whole layer. in the third layer of three-layer sols, macroscopically constituted by white precipitates, a three-dimensional structure constituted by the stacking of the fibril plates was observed. A model is proposed for the three-dimensional arrangement of the fibrils in the sols of pseudoboehmite according to their aging time at 90degreesC. (C) 2002 Elsevier Science B.V. All rights reserved.
Assunto colloidal aluminum hydroxides
pseudoboehmite sols
critical point drying
pseudoboehmite electron microscopy
Idioma Inglês
Data 2002-09-01
Publicado em Materials Chemistry and Physics. Lausanne: Elsevier Science Sa, v. 76, n. 3, p. 267-273, 2002.
ISSN 0254-0584 (Sherpa/Romeo, fator de impacto)
Editor Elsevier B.V.
Extensão 267-273
Direito de acesso Acesso restrito
Tipo Artigo
Web of Science WOS:000176920200009

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