Morphology transcription process from CMC micelles to inorganogel and its effect on the properties of alumina particle

In this study, a carboxymethyl cellulose (CMC)-mediated sol-gel process was developed to synthesize the alumina hydoxide whiskers. During the process, inexpensive inorganic salts were used as precursors and supercritical drying method was used to extract the water in hydrogel. The influences of CMC on the gel formation and the particle morphology were investigated. The results show that the formation of CMC-aluminium hydroxide organic-inorganic hybridgels led to a morphology transcription process from CMC micelles to aluminium hydroxide gel, as a result, the precursor with whiskerious morphology was obtained.

Hydrothermal synthesis of alumina nanotubes templated by anionic surfactant

The alumina nanotubes were prepared by using the anionic surfactant, sodium dodecyl sulfonate (SDS), as structure-directing template for the first time with Al(NO3)(3)center dot 9H(2)O as precursor via a hydrothermal method. Structure and morphology of the nanotubes were characterized by XRD, TEM, FT-IR, TG and N-2 adsorption-desorption. The obtained nanotubes were found having outer diameters from 6 to 8 nm with length up to 200 nm. (C) 2005 Elsevier B.V. All rights reserved.

The surface sites of sulfated zirconia studied in situ by laser-induced fluorescence spectroscopy

The surface sites of sulfated zirconia were investigated in situ by laser-induced fluorescence spectroscopy using aniline as the probe molecule. Different from the cases for many other oxides, the aniline adsorbed on the unique active sites of sulfated zirconia at r.t. is changed into another species, which emits a characteristic fluorescence band at 422 nm. The results illustrate that the sulfate groups in sulfated zirconia are favorable for the generation of these unique active sites, which also rarely exist on pure zirconia composed of tetragonal and monoclinic phases but do not exist on pure zirconia composed of monoclinic phase. (C) 2004 Elsevier B.V. All rights reserved.

Uniformly carbon-covered alumina and its surface characteristics

Uniformly carbon-covered alumina (CCA) was prepared via the carbonization of sucrose highly dispersed on the alumina surface. The CCA samples were characterized by XRD, XPS, DTA-TG, UV Raman, nitrogen adsorption experiments at 77 K, and rhodamine B (RB) adsorption in aqueous media. UV Raman spectra indicated that the carbon species formed were probably conjugated olefinic or polycyclic aromatic hydrocarbons, which can be considered molecular subunits of a graphitic plane. The N(2) adsorption isotherms, pore size distributions, and XPS results indicated that carbon was uniformly dispersed on the alumina surface in the as-prepared CCA. The carbon coverage and number of carbon layers in CCA could be controlled by the tuning of the sucrose content in the precursor and impregnation times. RB adsorption isotherms suggested that the monolayer adsorption capacity of RB on alumina increased drastically for the sample with uniformly dispersed carbon. The as-prepared CCA possessed the texture of alumina and the surface properties of carbon or both carbon and alumina depending on the carbon coverage.

Reversible regeneration of molybdenum carbonyl species on an alumina thin film

The thin alumina film-supported metallic molybdenum model catalyst was prepared by thermal decomposition of MO(CO)6, and CO chemisorption on the catalyst was investigated in-situ by thermal desorption spectroscopy (TDS) and X-ray photoelectron spectroscopy (XPS). The results showed that a molybdenum-carbonyl-like species was formed on the alumina surface at low temperature by high coordination of CO with the surface metallic molybdenum nanoparticles, indicating a reversible regeneration of molybdenum carbonyl on the alumina surface. CO chemisorption on the model catalyst surface caused the Mo 3d XPS peak to shift toward higher binding energy. The formed molybdenum carbonyl species appeared at about 240 K in the TDS. The supported metallic molybdenum nanoparticles were quite different from the bulk molybdenum in chemical properties, which indicated a prominent particle-size effect of the clusters.