Search results for "DISPERSION"

2021

The reaction of :AlAriPr8 (AriPr8 = C6H-2,6-(C6H2-2,4,6-iPr3)2-3,5-iPr2) with ArMe6N3 (ArMe6 = C6H3-2,6-(C6H2-2,4,6-Me3)2) in hexanes at ambient temperature gave the aluminum imide AriPr8AlNArMe6 (1). Its crystal structure displayed short Al-N distances of 1.625(4) and 1.628(3) A with linear (C-Al-N-C = 180°) or almost linear (C-Al-N = 172.4(2)°; Al-N-C = 172.5(3)°) geometries. DFT calculations confirm linear geometry with an Al-N distance of 1.635 A. According to energy decomposition analysis, the Al-N bond has three orbital components totaling -1350 kJ mol-1 and instantaneous interaction energy of -551 kJ mol-1 with respect to :AlAriPr8 and ArMe6N:. Dispersion accounts for -89 kJ mol-1, w…

Refractive index of the CuAlO2delafossite

2008

The refractive index of the CuAlO2 delafossite has been determined from interference measurements in single crystals performed in the visible, near and mid infrared regions of the spectrum. The analysis of the refractive index dispersion corresponding to light polarization perpendicular to the c-axis (P ⊥ c) yields a static dielectric constant of 0 = 7.7 ± 0.8 and a low frequency electronic constant ∞ = 5.1 ± 0.1. The relevant infrared active mode is found to be at 550 ± 25 cm−1. The electronic contribution can be well described by a Penn gap at 39 000 ± 1000 cm−1. Both the refractive index and its dispersion are found to be smaller for P||c than for P ⊥ c.

Weak interactions between trivalent pnictogen centers: computational analysis of bonding in dimers X3E...EX3 (E = pnictogen, X = halogen).

2009

The nature of weak interactions in dimers X(3)E...EX(3) (E = N-Bi, X = F-I) was investigated by wave function and density functional theory (DFT)-based methods. Out of the 20 systems studied, 10 are found to be bound at the CP-MP2 and LMP2 levels of theory. Detailed partition of the interaction energy into different components revealed that dispersion is the primary force holding the dimers together but there also exists an important ionic component whose contribution increases with increasing halogen size. As expected, standard density functionals fail to describe bonding in the studied systems. However, the performance of DFT methods can be easily improved via empirical dispersion correct…

Versatile wet-chemical synthesis of non-agglomerated CaCO3 vaterite nanoparticles.

2011

Calcium carbonate (vaterite) nanoparticles of 20-60 nm size were obtained without stabilizing tensides by heating a dispersion of calcium bicarbonate (CaHCO(3)) in ethylene glycol for 30 minutes at 40 to 100 °C.

Au deposited on CeO2 prepared by a nanocasting route: A high activity catalyst for CO oxidation

2014

Abstract A set of catalysts comprised of gold on different CeO 2 supports has been prepared by a nanocasting route and characterized by several physicochemical techniques. These catalysts have been tested for CO oxidation and show outstanding catalytic activity. Higher calcination temperatures of the hard template, producing a poorly ordered silica template, have led to a higher amount of oxygen vacancies on the surface of CeO 2 . The presence of surface oxygen defects in the support combined with the deposition of Au nanoparticles ( ca. 3 nm) homogeneously dispersed on the CeO 2 support may explain the excellent behaviour for low temperature CO oxidation. Surprisingly, it has been observed…

On the integrability of the extended nonlinear Schrödinger equation and the coupled extended nonlinear Schrödinger equations

2000

We consider the extended nonlinear Schr¨ (ENLS) equation which governs the propagation of nonlinear optical fields in a fibre with higher-order effects such as higher-order dispersion and self-steepening. We show that the ENLS equation does not pass the Painlev´ test. Similarly, we claim that the coupled ENLS equations and N -coupled ENLS equations which govern the simultaneous propagation of two and more nonlinear fields in optical fibres are also not integrable from the Painlev´ e analysis point of view.

Price Convergence in the European Union

2004

This study investigates the relationship between market integration and price convergence in international markets. Using a panel data set of consumer price indices (general and by groups and classes), it examines how European market integration has affected cross-country dispersion in the European Union.

Flow phenomenon of micron-sized particles during cold spray additive manufacturing: High-speed optic observation and characterization

2020

Abstract A high-speed laser shadowgraph observation of the particles flow during cold spraying enables a good phenomenological characterization. The particles in-flight behaviour develops a kinematics with two regimes regardless the powder nature. When leaving the nozzle, the particles form a regime of uniform jet over a certain distance along the flow direction, and then a regime of sparse jet while particles deviate in the radial direction. This dispersion increases away from the nozzle exit and exhibits thereby an event of oblique collision during an additive route process. Under such conditions, kinematic deficiency prevails since oblique collision has shown to alter the deposition effi…

Large eddy simulation of inertial particles dispersion in a turbulent gas-particle channel flow bounded by rough walls

2020

The purpose of this paper is to understand the capability and consistency of large eddy simulation (LES) in Eulerian–Lagrangian studies aimed at predicting inertial particle dispersion in turbulent wall-bounded flows, in the absence of ad hoc closure models in the Lagrangian equations of particle motion. The degree of improvement granted by LES models is object of debate, in terms of both accurate prediction of particle accumulation and local particle segregation; therefore, we assessed the accuracy in the prediction of the particle velocity statistics by comparison against direct numerical simulation (DNS) of a finer computational mesh, under both one-way and two-way coupling regimes. We p…

Etude theorique de la dynamique du réseau de batio en phase quadratique

1999

Abstract The lattice dynamics of barium titanate BaTiO 3 is discussed quantitatively in the framework of a shell model taking into account the electronic polarizabilities of the constituent ions and including Coulomb and short-range interactions. The results of calculations point out the important role of the anisotropic oxygen polarizability. There is a good agreement between calculated and experimental dispersion curves.