Search results for "Surfaces"

A Route to Grow Oxide Nanostructures Based on Metal Displacement Deposition: Lanthanides Oxy/Hydroxides Characterization

2012

Slow magnetic relaxation in carbonato-bridged dinuclear lanthanide(iii) complexes with 2,3-quinoxalinediolate ligands

2012

The coordination chemistry of the 2,3-quinoxalinediolate ligand with different lanthanide(iii) ions in basic media in air affords a new family of carbonato-bridged M 2 III compounds (M = Pr, Gd and Dy), the Dy 2 III analogue exhibiting slow magnetic relaxation behaviour typical of single-molecule magnets. This journal is © 2012 The Royal Society of Chemistry.

The Inchworm as a precision translator in a high magnetic field and UHV environment

1989

Abstract A new set-up has been designed and tested for on-line, high-precision mass measurements of short-lived radioactive isotopes via a determination of the ion cyclotron resonance. Ions delivered by the on-line isotope separator ISOLDE at CERN/Geneva are stored in a Penning trap installed in a superconducting solenoid. Due to severe space limitations in the bore of the solenoid, it is impossible to use conventional mechanical feedthroughs for the necessary manipulations inside the uhv chamber. Instead, a number of Inchworms, a high-precision positioning device based on the piezo-electric effect are employed. This publication reports on the first application of this device in a uhv envir…

Stratification Dynamics in Drying Colloidal Mixtures

2017

Stratification in binary colloidal mixtures was investigated using implicit-solvent molecular dynamics simulations. For large particle size ratios and film Péclet numbers greater than unity, smaller colloids migrated to the top of the film, while big colloids were pushed to the bottom, creating an "inverted" stratification. This peculiar behavior was observed in recent simulations and experiments conducted by Fortini et al. [ Phys. Rev. Lett. 2016 , 116 , 118301 ]. To rationalize this behavior, particle size ratios and drying rates spanning qualitatively different Péclet number regimes were systematically studied, and the dynamics of the inverted stratification were quantified in detail. Th…

On the topographic and energetic surface modifications induced by laser treatment of metallic substrates before plasma spraying

2003

Abstract Laser surface cleaning has been proven as a very suitable technique for the substitution of some surface preparation steps, such as wet cleaning and grit blasting. The mechanisms involved in short pulsed laser ablation include the absorption of the laser light and conversion into heat via collisional processes. Ejection of matter is achieved either by direct vaporization or hydrodynamical sputtering. This article aims at clarifying the laser–matter interaction mechanisms and effects on metallic materials for different surfaces initial roughness and laser beam energy densities. Both topographic and energetic modifications are investigated by SEM observations, roughness characterizat…

Surface modifications induced by nanosecond pulsed Nd:YAG laser irradiation of metallic substrates

2006

International audience; Substrate surface preparation is a key step in coating deposition process. In recent years, pulsed laser cleaning has emerged as a possible technique to challenge the traditional preparation methods (based on degreasing and eventually grit-blasting). The laser operated at short-pulse mode offers high cleaning efficiency and therefore has been largely used. In a specific process named PROTAL®, a nanosecond pulsed laser is introduced to prepare the surface simultaneously to thermal spraying, with the purpose of eliminating the contaminants and generating favorite surface conditions for coating deposition. This study aims at clarifying some fundamental aspects of nanose…

CO Oxidation on Cationic Gold Clusters: A Theoretical Study

2008

Aiming at understanding the elementary steps governing the oxidation of CO catalyzed by dispersed or supported gold nanoclusters, the reactivity of molecular species, such as O2 and CO, on neutral and positively charged Au13 clusters have been studied using a DFT approach. Two CO oxidation mechanisms have been simulated, involving respectively the adsorption of CO and O2 on adjacent catalytic sites (two-sites mechanism) and the competitive interaction of the reactants on the same site (single-site mechanism). It is demonstrated that in the former scheme a definite interaction of CO and O2 with both the charged and neutral cluster is effective, but that a chemical reaction between the adsorb…

Proof of multilayer structural organization in self-assembled polycation-polyanion molecular films

1994

Abstract Multilayer organization of ultrathin polycation-polyanion self-assembled films is demonstrated using two approaches. (1) Fabrication of polyion superlattices with alternation of three different polyelectrolytes in (ABCB) n fashion, which gives rise to a Bragg peak in X-ray reflectivity. The spacing d=93.4 A corresponds to the repeat unit (ABCB) n . (2) Drying-induced manipulation of the film surface at regular intervals. Normally the layer-by-layer adsorption is carried out by keeping the film wet throughout all deposition cycles. Alternatively the film surface can be manipulated by gently drying the film in a stream of nitrogen or air after the adsorption of every layer. When the …

Photoelectropoling of azobenzene chromophores in molecular films

1994

The photoinduced reorientation and photoelectropoling processes were investigated in molecular films of aliphatically substituted azobenzenes. While polarized illumination leads to a conversion of isotropic samples into anisotropic ones, upon application of external electric fields even macroscopically polar materials are created. The macroscopic polarity can be reversed under suitable experimental conditions. Order parameters as a function of the poling field were determined by Stark spectroscopy. Using atomic force microscopy it is shown that the structure of the sample is well defined on a microscopic length scale, whereas on a macroscopic length scale it is not.

Aggregation and Gel Formation in Basic Silico−Calco−Alkaline Solutions Studied:  A SAXS, SANS, and ELS Study

1999

Gelation of strongly basic silico−alkaline solutions was promoted by appropriate additions of calcium ions. The structure of the aggregates formed in the precursor sols and the resulting gels were studied, within a wide length scale, using small-angle X-ray, small-angle neutron, and elastic light scattering. The study of the kinetics of aggregation was performed in situ. The experimental results demonstrate that gels are composed of aggregates exhibiting a fractal structure, large particles formed in the solutions just after calcium addition and, in some cases, small primary particles remaining in the solution phase. The structural features of the gels are strongly dependent on the concentr…