Search results for " metal"
showing 10 items of 2159 documents
Catalytic effect of transition metals (copper, iron, and nickel) on the foaming and properties of sugar-based carbon foams
2019
Abstract Recently, bio-based carbon foams have gained much interest in many chemical industry fields because of their unique structure and properties. This study provides new information on the effects of catalytic metals (iron, nickel, and copper) on the foaming process. Specifically, the effects of these catalysts on the density, foam growth, and cell size and then further on the pore size distribution and specific surface areas after the physical activation are considered. Furthermore, some of the activated sugar foams were used in adsorption tests using methylene blue as adsorbent. Results showed that the highest effect on foam density was obtained using the iron catalyst in the foaming…
Transition metal ion induced hydrogelation by amino-terpyridine ligands
2014
Hydrogelation behavior of two amino-terpyridine ligands in the presence of divalent metal ions in water was studied in detail. The effect of ligand structure and different counter anions on the gel morphologies was also explored. peerReviewed
Role of elastic and electronic interactions in trapping of hydrogen by impurities in transition metals
1985
The interplay between the lattice distortion and the electronic contributions to the trapping of migrating hydrogen isotopes by substitutional impurities is investigated. We use a comprehensive calculational scheme incorporating (i) the effective-medium theory for the electronic interaction, (ii) the lattice Green’s function for elastic coupling, and (iii) the hydrogen quantum motion. The calculations for Ti and Cr impurities in V host show that lattice strain effects dominate. Cr, which otherwise provides an electronic trap site, does not induce trapping when elastic effects are incorporated. The situation in the case of Ti is just the reverse. We find no isotope dependence of the binding …
Geochemical fingerprints of brannerite (UTi 2 O 6 ): an integrated study
2020
AbstractBrannerite (UTi2O6) is among the major uranium-bearing minerals found in ore deposits, however as it has been long considered as a refractory mineral for leaching it is currently disregarded in ore deposits. Brannerite is found in a variety of geological environments with the most common occurrences being hydrothermal and pegmatitic. On the basis of scanning electron microscopy observations coupled with electron probe micro-analyses and laser ablation inductively-coupled plasma mass spectrometer analyses, this study describes the morphological features and the major- and trace-element abundances of brannerite samples from five hydrothermal and five pegmatitic localities across the w…
CoS2/TiO2 Nanocomposites for Hydrogen Production under UV Irradiation
2019
Transition metal chalcogenides have intensively focused on photocatalytic hydrogen production for a decade due to their stronger edge and the quantum confinement effect. This work mainly focuses on synthesis and hydrogen production efficiencies of cobalt disulfide (CoS2)-embedded TiO2 nanocomposites. Materials are synthesized by using a hydrothermal approach and the hydrogen production efficiencies of pristine CoS2, TiO2 nanoparticles and CoS2/TiO2 nanocomposites are compared under UV irradiation. A higher amount of hydrogen production (2.55 mmol g&minus
Active lighting applied to three dimensional reconstruction of specular metallic surfaces by polarization imaging
2005
This thesis deals with a new automated tridimensional inspection system for specular metallic surfaces, based on polarization analysis. We first present an extension of the ‘Shape from Polarization' method for dielectric to metallic surfaces. After being reflected, an unpolarized light wave becomes partially linearly polarized, depending on the surface normal and on the refractive index of the media it impinges on. Hence, by measuring the polarization parameters of the reflected light, the surface normals are computed. The ambiguity concerning the normals orientation is solved here with a new active lighting system. Then, we describe and compare numerical methods for reconstructing the trid…
Acidic Co-Catalysts in Cationic Gold Catalysis.
2016
A systematic study on the effects of Lewis or Bronsted acid co-catalysts in gold-catalyzed reactions was undertaken using representative reactions (O-, N-, and C-nucleophilic additions to alkynes). Through these reactions, it was demonstrated that an acidic co-catalyst can increase the catalyst turnover significantly, enabling practical reaction rates at competitive catalyst loadings (<1 mol %). Further investigation is currently underway to improve the understanding of the subtle principles underlying these experimental observations.
Multi-channel receptors based on thiopyrylium functionalised with macrocyclic receptors for the recognition of transition metal cations and anions.
2010
We report herein the synthesis and characterization of a family of ligands containing different cation binding sites covalently connected to a thiopyrylium signalling reporter. The receptors L1–L6 are able to signal the presence of certain metal cations via three different channels; i.e. electrochemically, fluorogenically and chromogenically. An acetonitrile solution of L1–L6 shows a bright blue colour due to a charge-transfer band in the 575–585 nm region. The colour variation in acetonitrile of L1–L6 in the presence of the metal cations Ag+, Cd2+, Cu2+, Fe3+, Hg2+, Ni2+, Pb2+ and Zn2+ has been studied. A selective hypsochromic shift of the blue band was found for the systems L4-Pb2+ and L…
Anion exchange membrane based on alkali doped poly(2,5-benzimidazole) for fuel cell
2012
Abstract The properties of alkali doped poly(2,5-benzimidazole) membrane with different alkali doping levels for fuel cell application are reported in this work. The alkali doping level played an important role for the ion conductivity of the membrane. The ion conductivity significantly increased with alkali doping level. The ion conductivity also increased with the temperature. The ion conductivity of the alkali doped ABPBI membrane (alkali doping level = 0.37), reached to 2.3 × 10 − 2 S cm − 1 at room temperature and 7.3 × 10 − 2 S cm − 1 at 100 °C. The water uptake of the alkali doped ABPBI membrane was increased from 9.1% to 19.2% with increasing alkali doping level at room temperatur…
4,4′-bis(dimethylamino)biphenyl containing binding sites. A newfluorescent subunit for cation sensing
2002
The emission behaviour of the 4,4′-bis(dimethylamino)biphenyl subunit covalently attached to aza-crown ethers is studied. Some new ligands have been synthesised in order to test the properties of this new fluorophore. The fluorescence of these new ligands and some other compounds previously described has been studied in acetonitrile in the presence of Ni2+, Cu2+, Zn2+, Hg2+, Pb2+, Cd2+ and also in the presence of some alkali and alkaline-earth cations.