Search results for " interfaces"
showing 10 items of 1158 documents
SURFACE EFFECTS ON THE GROWTH OF SOLUTION PROCESSED PENTACENE THIN FILMS
2008
13,6-N-Sulfinylacetamidopentacene (SAP) has been transferred on solid substrates both by water-rich environment and organic solvents without altering his chemical structure. Thermal conversion of SAP to pentacene leads to crystals showing similar features of vacuum-sublimated pentacene both in the bulk and thin-film phases. The thin-film phase is strongly affected by the substrate surface properties. Low energy Si-CH3 rich surfaces allow for the formation of compact micrometric crystals following a Volmer-Weber like growth with orientation suitable for field-effect carrier mobility. Screw dislocations along with straight edges are found on these systems as an indication of a loose interlaye…
First-principles calculations for SrTiO3() surface structure
2002
As a continuation of our recent abinitio calculations of SrTiO 3(1 0 0) surface relaxation for the two different terminations (SrO and TiO2) [Phys. Rev. B 64 (2001) 23417], we analyze here their electronic structures (band structure, density of states, and the electronic density redistribution with emphasis on the covalency effects). We compare results of abinitio Hartree–Fock method with electron correlation corrections and density functional theory with different exchange-correlation functionals, including hybrid (B3PW, B3LYP) exchange techniques. Our results are also compared with previous abinitio plane-wave local density approximation calculations and experiments when availab le. Consi…
Electrophoretic flow behaviour and mobility of colloidal fluids and crystals.
2007
We report on measurements of the electrophoretic mobility mu of charged colloidal spheres in the deionized state, where the suspensions show fluid or crystalline order. In the fluid state, parabolic flow profiles are observed due to electro-osmotic solvent flow. In the crystalline state, complex flow profiles occur due to additional crystal cohesion. The mobility mu then may inferred from the flow velocity averaged over the complete cell cross section as performed in our home built super-heterodyne Doppler velocimeter. For two particle species of 68 and 122 nm diameter we measured mu as a function of particle concentration. Starting from a plateau value at low concentration, mu decreases ap…
Prediction of friction and heat flow in machining incorporating thermophysical properties of the coating–chip interface
2004
Abstract This paper deals with an experimental and analytical investigation into the thermodynamically activated effects influencing the behaviour of the multi-layered coated tool rake face during orthogonal cutting of ferromagnetic and paramagnetic steels. Temperature measurements on the tool rake face using a thermocouple-based technique and identification of the contact zone by means of computer image processing were carried out. New methodology for assessing friction and the amount of thermal energy generated when machining with a coated tool insert with natural and restricted contact coupled with a metallic chip, using thermophysical properties of the sliding materials is developed in …
A New Quasi-Static Cylindrical Roller Bearing Model to Accurately Consider Non-Hertzian Contact Pressure in Time Domain Simulations
2012
The accuracy of the fatigue life calculations in rolling bearing simulations is highly dependent on the precision of the roller-raceway contact simulations. Several different methods exist to simulate these pressure distributions and in time domain bearing simulations, where many contacts need evaluation, the simple and time efficient methods are more popular, yielding erroneous life estimates. This paper presents a new six degree of freedom frictionless quasi-static time domain cylindrical roller bearing model that uses high precision elastic half-space theory to simulate the contact pressures. The potentially higher computational demand using the advanced contact calculations is addressed…
A New Solution for Low-Voltage Distributed Generation Interface Protection System
2015
In this paper, a new solution is proposed for the remote monitoring and control of distributed generators (DGs) and energy storage systems (ESSs) connected to low-voltage distribution networks. The proposed system fulfills the in-force standard requirements for the connection of DGs to the utility grid. Moreover, it allows implementing some enhanced functions for the remote control of inverters of DGs and ESSs, not only in terms of disconnection but also in terms of voltage regulation and power shuttering. The proposed solution is based on a new interface protection system and a dedicated secondary substation concentrator, which allows the communication between the distributed system operat…
Quantitative description of temperature induced self-aggregation thermograms determined by differential scanning calorimetry
2012
A novel thermodynamic approach for the description of differential scanning calorimetry (DSC) experiments on self-aggregating systems is derived and presented. The method is based on a mass action model where temperature dependence of aggregation numbers is considered. The validity of the model was confirmed by describing the aggregation behavior of poly(ethylene oxide)-poly(propylene oxide) block copolymers, which are well-known to exhibit a strong temperature dependence. The quantitative description of the thermograms could be performed without any discrepancy between calorimetric and van 't Hoff enthalpies, and moreover, the aggregation numbers obtained from the best fit of the DSC exper…
Potential determining salts in microemulsions: interfacial distribution and effect on the phase behavior.
2013
In this work we consider potential determining salts, also referred to as phase transfer agents for a future objective of electrochemistry at the oil-water interface in microemulsions. We have studied these salts, composed of a hydrophilic and a hydrophobic ion, in microemulsion stabilized by nonionic surfactants with an oligo ethylene oxide headgroup. NMR measurements show that the salts preferentially dissociate across the surfactant interface between the oil and water domains, and hence create a potential drop across the surfactant film, and back to back diffuse double layers in the oil and water phases. These observations are also supported by Poisson-Boltzmann calculations. This adsorp…
Ethylene and phenylene bridged polysilsesquioxanes functionalized by amine and thiol groups as adsorbents of volatile organic compounds
2007
Abstract Ethylene and phenylene bridged polysilsesquioxane xerogels having amine and thiol groups attached to the surface have been obtained by the sol–gel method from 1,2-bis(triethoxysilyl)ethane or 1,4-bis(triethoxysilyl)benzene and functionalized silanes in the presence of an ammonium fluoride catalyst in an ethanol solution. The synthesized samples have a porous structure (700–850 m2/g) and a high content of functional groups (1.4–1.9 mmol/g). The obtained porous bridged polysilsesquioxanes exhibit a considerable affinity for adsorbing several organic compounds (n-hexane, n-heptane, benzene, cyclohexane, acetonitrile and triethylamine) from the gas phase. The sample with an ethylene br…
DFT study on complete ethylene decomposition on flat and stepped Pd
2010
Abstract We applied density functional theory (DFT) calculations to study ethylidyne (CCH 3 ) adsorption and decomposition to C and H over flat and stepped Pd surfaces. Our calculations show that ethylidyne is the most stable molecule among all the possible dehydrogenation or decomposition residues of ethylene. We discuss various possible reaction pathways for ethylidyne decomposition and point out that the most probable one is via ethynyl (CCH) species suggested also by experimental observations. Our calculations indicate that the presence of steps modify the potential energy surface by increasing the binding of most of the species, and also lowering the activation barrier for several reac…