M.D. Sánchez

Electron microscopy study of CeOx–Pd/α-Al2O3 catalysts for methane dry reforming

We have investigated the interaction between Pd and Ce in a (0.47 wt %) CeOx–Pd(1 wt %)/α-Al2O3 catalyst that is used in the reforming reaction of CH4 with CO2. The freshly reduced catalyst was characterized by various electron microscopy techniques, such as elemental mapping, Z-contrast imaging, and electron energy-loss spectroscopy to understand the role of Ce on a microscopic scale. The high spatial resolution elemental mapping indicates that CeOx is located in close proximity of the palladium nanoparticles. High-resolution lattice images and energy-loss spectra obtained in the vicinity of the Pd particles show an anisotropic distribution of CeOx crystallites limited to the interface region between Pd and the substrate but not covering the surface of the Pd nanoparticles. Energy-loss near edge fine structure of Pd M edges reveals that the Pd nanoparticles are not oxidized.We have investigated the interaction between Pd and Ce in a (0.47 wt %) CeOx–Pd(1 wt %)/α-Al2O3 catalyst that is used in the reforming reaction of CH4 with CO2. The freshly reduced catalyst was characterized by various electron microscopy techniques, such as elemental mapping, Z-contrast imaging, and electron energy-loss spectroscopy to understand the role of Ce on a microscopic scale. The high spatial resolution elemental mapping indicates that CeOx is located in close proximity of the palladium nanoparticles. High-resolution lattice images and energy-loss spectra obtained in the vicinity of the Pd particles show an anisotropic distribution of CeOx crystallites limited to the interface region between Pd and the substrate but not covering the surface of the Pd nanoparticles. Energy-loss near edge fine structure of Pd M edges reveals that the Pd nanoparticles are not oxidized.

Numerical experiments on dynamic stiffening of beams and plates

Abstract By introducing continuous or discontinuous variations in the thickness of beams, arches and plates, it is possible in many practical situations to raise the value of the fundamental frequency and, at the same time, to lower the weight of the structural element. This is a beneficial situation, especially in those cases where weight reduction and large dynamic stiffness are of interest. The present paper surveys some recent practical accomplishments in this area. The rigorous procedure consists, from a general structural optimization viewpoint, of minimizing an objective function (for instance, total volume) subject to constraints on the geometry and behavior (natural frequencies, buckling loads, etc.). In many instances it is convenient to reverse the problem: one fixes or limits the weight or volume and constructs some quantity which describes the desired behavior of the system e.g. the fundamental frequency. The problems under study in the present paper are considerably more modest in scope, since the procedure is performed by numerical experiments.

Multiple Scattering Processes in Ion Atom Single Ionization

The recent advances in the spectroscopy of ion atom collision processes have enabled the accomplishment of kinematically complete experiments where determination of all components of the momentum of each particle in the colliding system is achieved. In this paper we give an account of different multiple scattering processes which can be identified in ion-atom ionization calculations for the triply differential cross section and how the structures that appear could be experimentally searched using recoil-ion momentum spectroscopy techniques.

TRIPLY DIFFERENTIAL CROSS SECTION FOR IONIZATION OF MULTIELECTRONIC TARGETS

Abstract The Continuum Distorted Wave-Eikonal Initial State (CDW-EIS) approach is used to calculate the Triply Differential Cross Section (TDCS) for ionization of multielectronic atomic targets in coincidence with the outgoing projectile direction and recoil momentum of the target. A generatrix state method is used to evaluate the transition amplitudes for a general initial atomic state. The structures presented in both TDCSs are compared standing out the double collision mechanisms. The results obtained in CDW-EIS approximation are compared with previous classical trajectories Monte Carlo (CTMC) calculations.