Search results for "engineering.material"

Effects of pressure, temperature and atomic exchanges on phase separation dynamics in Au/Ni(111) surface alloy: Kinetic Monte Carlo study

2015

Abstract Instability of the Au/Ni(111) surface alloy is studied in different CO gas pressure, p , and temperature limits using kinetic Monte Carlo simulations. We analyze the reaction front dynamics and formation of Au clusters using the model which takes into account surface adatom pair and three-body interactions, CO adsorption and desorption, catalytic carbonyl formation reaction, Au and Ni adatom diffusion and their concerted exchange. Variation of interaction parameters allows us to identify three possible reaction front propagation limits with different pressure dependencies: (i) slow channel-like flow in agreement with experimental data [1] (step flow rate, R , increases with p ), (i…

Electrochemical Detection of High Oxidation States of Chromium( IV and V ) in Chromium‐Doped Cassiterite and Tin‐Sphene Ceramic Pigmenting Systems

2006

Solid-state electrochemistry is applied to detect the presence of chromium centres with high oxidation states in chromium-doped cassiterite and tin-sphene ceramic pigmenting systems. Voltammetric data indicate that CrV and CrIV centres with different coordinative arrangements exist in the studied materials, and yield proton-assisted reduction processes at +0.95, +0.42 AgCl/Ag in contact with 0.50 M H2SO4. Electrochemical measurements are correlated with spectroscopic data. The CrIV and CrV metal ions display a significant light-driven electrocatalytic effect on the oxidation of 1,4-dihydrobenzoquinone and Fe(CN)64– ions that involves the formation of surface-confined adducts. (© Wiley-VCH V…

Deciphering the Role of Dipolar Interactions in Magnetic Layered Double Hydroxides

2018

Layered double hydroxides (LDHs) exhibit unparalleled anion exchange properties and the ability to be exfoliated into 2D nanosheets, which can be used as a building block to fabricate a wide variety of hybrid functional nanostructured materials. Still, if one wants to use LDHs as a magnetic building blocks in the design of complex architectures, the role played by the dipolar magnetic interactions in these layered materials needs to be understood. In this work, we synthesized and characterized a five-membered CoAl-LDH series with basal spacing ranging from 7.5 to 34 Å. A detailed experimental characterization allows us to conclude that the main factor governing the dipolar interactions betw…

Cover Feature: Fundamental Insights into the Covalent Silane Functionalization of NiFe Layered Double Hydroxides (Chem. Eur. J. 29/2020)

2020

Dynamic response in pH and the transient behavior of some chemical elements in pulp-water suspensions

1999

Properties of methyl radical trapped in amorphous SiO2 and in natural SiO2-clathrate Melanophlogite

2013

Abstract We report an experimental investigation by electron paramagnetic resonance (EPR) on methyl radical (CH3 ) observed in γ-ray irradiated high-purity amorphous silicon dioxide (a-SiO2) and in a polycrystalline sample of Melanophlogite, a rare natural form of SiO2-clathrate. From the analysis of the EPR spectra we estimate the correlation time of the hindered rotational motion of CH3 molecules at T = 77 K in the two different materials. This physical quantity gives a quantitative measure of the freedom of motion of CH3 molecules trapped in the two solid systems, putting forward relevant information on the properties of the cavities/interstices in which the radicals are confined. In par…

MOCVD growth of CdTe on glass: analysis of in situ post-growth annealing

2004

Abstract In this paper, we analyse the growth by MOCVD of CdTe on glass substrates using in situ post-growth annealing. First, in order to perform a systematic study, polycrystalline layers of CdTe were deposited by MOCVD on glass substrates. The structure and morphology of the layers was investigated as a function of different growth parameters, temperature, VI/II precursor molar ratio and substrate position on the susceptor. An activation energy of Ek=20.7 kcal/mol was obtained from the experimental data. In order to better understand the process and the effects of different growth parameters, a numerical model that simulated the gas flow in the reactor, was developed. Secondly we analyse…

Mechanisms of Organic Coating on the Surface of a Poplar Biochar

2017

Background: Recent studies highlighted that biochar efficiency to improve soil fertility is enhanced after it is blended with fresh organic materials. It was suggested that organic coating of inner-porous biochar surfaces acts as a kind of “glue” for plant-nutrients, thereby allowing their slow release towards plant-roots and/or microorganisms. Objective: The aim of the present study is to improve the understanding of the nature of the interactions between fresh organic matter and a poplar biochar. Method: Two fluorinated organic models were used as target molecules in order to apply heteronuclear (i.e. 19F) fast field cycling (FFC) NMR relaxometry. Results: The results suggest that organic…

Nanoreactors for the multi-functionalization of poly-histidine fragments

2019

Water-soluble MBHA derivatives were found to self-assemble in a water environment to generate aggregates showing core–shell architectures. The aggregates appeared to be capable of working as nanoreactors performing a multi-functionalization of poly-histidine fragments, which after an initial interaction with the solvated oligo(ethylene glycol) shell reach the reactive core.

Physicochemical Investigation of Lightfast AgCl and AgBr Nanoparticles Synthesized by a Novel Solid−Solid Reaction

2003

Small size AgX (X = Br, Cl) nanoparticles have been synthesized by a novel solid−solid reaction performed by mixing two dry dispersions of AgNO3 and KX nanoparticles in AOT/n-heptane solutions. UV−vis investigation ascertained that formation of nanosized particles taking place after the mixing process is fast and complete. Microcalorimetric measurements of the thermal effect coupled with the mixing process suggest the occurrence of confinement effects and adsorption of the surfactant molecules at the nanoparticle surface, hinting at formation of charged nonstoichiometric surfactant-coated nanoparticles. The analysis of SAXS spectra shows that salt-containing AOT reversed micelles are slight…