Adsorption of the diazo dye Direct Red 23 onto a zinc oxide surface: A spectroscopic study

The adsorption of the diazo dye Direct Red 23 onto a zinc oxide surface at 30 degrees C in the dark was investigated. The color reduction was monitored by spectrophotometry at 503 run. The FTIR and Raman spectra of the Direct Red 23 adsorption as a function of ZnO concentration were registered. From the PM3 semi-empirical calculations of the atomic charge density and dipole moment of the Direct Red 23 molecule, it was demonstrated that the azo, dye molecule may be adsorbed onto the ZnO Surface through molecule geometry modifications, enhancing the interfacial area causing a variation in the bonding frequencies. (C) 2009 Elsevier B.V. All rights reserved.

Effects of alloying elements on the cytotoxic response of titanium alloys

Titanium alloys, alloys, especially beta-type alloys containing beta-stabilizing elements, constitute a highly versatile category of metallic materials that have been under constant development for application in orthopedics and dentistry. This type of alloy generally presents a high mechanical strength-to-weight ratio, excellent corrosion resistance and low elastic modulus. The purpose of this study is to evaluate the cytotoxicity and adhesion of fibroblast cells on titanium alloy substrates containing Nb, Ta, Zr, Cu, Sn and Mo alloying elements. Cells cultured on polystyrene were used as controls. In vitro results with Vero cells demonstrated that the tested materials, except Cu-based alloy, presented high viability in short-term testing. Adhesion of cells cultured on disks showed no differences between the materials and reference except for the Ti-Cu alloy, which showed reduced adhesion attributed to poor metabolic activity. Titanium alloys with the addition of Nb, Ta, Zr, Sn and Mo elements show a promising potential for biomedical applications. (C) 2011 Elsevier B.V. All rights reserved.

Production of hydrogen via steam reforming of biofuels on Ni/CeO(2)-Al(2)O(3) catalysts promoted by noble metals

The catalytic activity of Ni/CeO(2)-Al(2)O(3) catalysts modified with noble metals (Pt, Ir, Pd and Ru) was investigated for the steam reform of ethanol and glycerol. The catalysts were characterized by the following techniques: Energy-dispersive X-ray, BET, X-ray diffraction, temperature-programmed reduction, UV-vis diffuse reflectance spectroscopy and X-ray absorption near edge structure (XANES). The results showed that the formation of inactive nickel aluminate was prevented by the presence of CeO(2) dispersed on alumina. The promoting effect of noble metals included a decrease in the reduction temperatures of NiO species interacting with the support, due to the hydrogen spillover effect. It was seen that the addition of noble metal stabilized the Ni sites in the reduced state along the reforming reaction, increasing the ethanol and glycerol conversions and decreasing the coke formation. The higher catalytic performance for the ethanol steam reforming at 600 degrees C and glycerol steam reforming was obtained for the NiPd and NiPt catalysts, respectively, which presented an effluent gaseous mixture with the highest H(2) yield with reasonably low amounts of CO. (c) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.

Ethanol steam reforming for production of hydrogen on magnesium aluminate-supported cobalt catalysts promoted by noble metals

The performance of noble metal (Pt, Ru, Ir)-promoted Co/MgAl(2)O(4) catalysts for the steam reforming of ethanol was investigated. The catalysts were characterized by energy-dispersive X-ray spectroscopy, Xray diffraction, UV-vis diffuse reflectance spectroscopy, temperature-programmed reduction, temperature-programmed oxidation and X-ray absorption near edge structure (XANES). The results showed that the formation of inactive cobalt aluminate was suppressed by the presence of a MgAl(2)O(4) spinel phase. The effects of the noble metals included a marked lowering of the reduction temperatures of the cobalt surface species interacting with the support. It was seen that the addition of noble metal stabilized the Co sites in the reduced state throughout the reaction. Catalytic performance was enhanced in the promoted catalysts, particularly CoRu/MgAl(2)O(4), which showed the highest selectivity for H(2) production. (C) 2009 Elsevier B.V. All rights reserved.

Hydrogen production by steam reforming of ethanol over Ni-based catalysts promoted with noble metals

The catalytic activity of Ni/La(2)O(3)-Al(2)O(3) Catalysts modified with noble metals(Pt and Pd) was investigated in the steam reforming of ethanol. The catalysts were characterized by ICP, S(BFT), X-ray diffraction, temperature-programmed reduction, UV-vis diffuse reflectance spectroscopy and X-ray absorption fine structure (XANES). The results showed that the formation of inactive nickel aluminate was prevented by the presence of La(2)O(3) dispersed on the alumina. The promoting effect of noble metals included a marked decrease in the reduction temperatures of NiO species interacting with the support. due to the hydrogen spillover effect, facilitating greatly the reduction of the promoted catalysts. it was seen that the addition of noble metal stabilized the Ni sites in the reduced state throughout the reaction, increasing ethanol conversion and decreasing coke formation, irrespective of the nature or loading of the noble metal. (C) 2009 Elsevier B.V. All rights reserved.

Effect of adding CaO to ZrO(2) support on nickel catalyst activity in dry reforming of methane

Nickel catalysts with a load of 5 wt% Ni, supported on pure ZrO(2) and ZrO(2) stabilized with 4, 8 and 14 mol% CaO, were prepared by the polymerization method. The samples were characterized by X-ray diffraction (XRD), temperature-programmed reduction with hydrogen (TPR-H(2)), specific surface area (BET) and impedance spectroscopy (IS) and tested in the carbon dioxide reforming of methane. The XRD patterns showed the presence of the oxide precursor (NiO) and the tetragonal phase of CaO-ZrO(2) solid solutions. According to the TPR-H(2) analysis, the reduction of various NiO species was influenced by the support composition. The electrical properties of the support have a proportional effect on the catalytic activities. Catalytic tests were done at 800 degrees C for 6 h and the composition of the gaseous products and the catalytic conversion depended on the CaO-ZrO(2) solid solution composition and its influence on supported NiO species. A direct relation was found between the variation in the electrical conductivity of the support, the nickel species supported on it and the performance in the catalytic tests. (C) 2009 Elsevier B.V. All rights reserved.

Self-reinforced composites obtained by the partial oxypropylation of cellulose fibers. 2. Effect of catalyst on the mechanical and dynamic mechanical properties

This work describes the partial oxypropylation of filter paper cellulose fibers, employing two different basic catalyst, viz., potassium hydroxide and 1,4-diazabicyclo [2.2.2] octane, to activate the hydroxyl groups of the polysaccharide and thus provide the anionic initiation sites for the ""grafting-from"" polymerization of propylene oxide. The success of this chemical modification was assessed by FTIR spectroscopy, X-ray diffraction, scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis and contact angle measurements. The study of the role of the catalyst employed on the extent of the modification and on the mechanical properties of the ensuing composites, after hot pressing, showed that both the Bronsted and the Lewis base gave satisfactory results, without any marked difference.