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Boehmite

About: Boehmite is a research topic. Over the lifetime, 3085 publications have been published within this topic receiving 54863 citations. The topic is also known as: boehmite.


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Journal ArticleDOI
11 Jul 2003-Langmuir
TL;DR: In this article, a general method to coat colloids with silica is described, which is especially useful for colloidal particles that cannot be covered directly with SiO2 by a Stober-like growth process.
Abstract: A general method to coat colloids with silica is described. The amphiphilic, nonionic polymer poly(vinylpyrrolidone) (PVP) was adsorbed to various colloidal particles such as small gold colloids, gold-shell silica-core particles, small and large silver colloids, boehmite rods, gibbsite platelets, and positively or negatively charged polystyrene. After this functionalization the stabilized particles could be transferred to a solution of ammonia in ethanol and directly coated with smooth and homogeneous silica shells of variable thickness by addition of tetraethoxysilane in a seeded growth process. The length of the polymer used strongly influences the stability of the colloids and the homogeneity and smoothness of the initial silica coating. This method is especially useful for colloidal particles that cannot be covered directly with SiO2 by a Stober-like growth process. Compared to methods known from the literature for the coating of such particles, this new method is faster and requires neither the use o...

1,009 citations

Journal ArticleDOI
TL;DR: In this paper, the formation of the well ordered super spinel structure is suppressed by obstructing the diffusion of the A1 ions either by the surface of numerous pores or by incorporating large ions such as Na ions (y-alumina from crystalline boehmite) and in these cases the disordered spinel type aluminas are transformed at a high temperature to 0and a-Al~O 3 by complete recrystallization to small particles which still have some preferred orientation.
Abstract: Bayerite, fl-AI(OH)3, and boehmite, 7-A1OOH, both with crystallite sizes of some tenths of a micron, were used for this investigation. The transformation of bayerite to T-alumina and of boehmite to 7and a for 7-alumina the oxygen sublattice is fairly well ordered, whereas the tetrahedral A1 lattice is strongly disordered. The crystallographic texture of 7and 7-alumina could be related to their microporous texture and this in its turn to the length of the OH bonds in the hydroxides. The formation of the well ordered super spinel structure ~-A120 3 is suppressed by obstructing the diffusion of the A1 ions either by the surface of numerous pores (T-alumina from bayerite or 7-alumina from gelatinous boehmite) or by incorporating large ions such as Na ions (y-alumina from crystalline boehmite). In these cases the disordered spinel type aluminas are transformed at a high temperature to 0and a-Al~O 3 by complete recrystallization to small particles which still have some preferred orientation.

457 citations

Journal ArticleDOI
TL;DR: In this article, the gamma, delta, theta and alpha-Al{sub 2}O{sub 3} phases, prepared by dehydration of aluminium oxihydroxide AlOOH (boehmite), were measured by XRD and IR spectroscopy on all samples.

428 citations

Journal ArticleDOI
TL;DR: In this article, a step-by-step mechanism for the structural transformation of boehmite (AlOOH) taking place under calcination and leading to γ-alumina (γ-Al2O3) has been investigated theoretically.
Abstract: The topotactic transformation of boehmite (AlOOH) taking place under calcination and leading to γ-alumina (γ-Al2O3) has been investigated theoretically and a step-by-step mechanism for the structural transformation is proposed This mechanism reveals two major steps First, the structural collapse of boehmite occurs, after hydrogen transfers and water extraction Then, through an aluminum migration process, the γ-alumina characteristics appear The proposed mechanism demonstrates the existence of an equilibrium structure for γ-alumina containing 25−31% of tetrahedral aluminum sites in agreement with nuclear magnetic resonance (NMR) results Temperature effects on the thermodynamic stability of the different structures involved in the mechanism has been investigated Theoretically simulated X-ray diffraction (XRD) patterns confirm the validity of our model structures According to this mechanism, a coherent skeleton of γ-alumina inherited from the original AlOOH network is constructed This skeleton can be

428 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202379
2022167
202181
2020120
2019115
2018139