Search results for "Epos"
showing 10 items of 1649 documents
Pt–CeO thin film catalysts for PEMFC
2015
Abstract Platinum is the mostly used element in catalysts for fuel cell technology, but its high price limits large-scale applications. Platinum doped cerium oxide represents an alternative solution due to very low loading, typically few micrograms per 1 cm2, at the proton exchange membrane fuel cell (PEMFC) anode. High efficiency is achieved by using magnetron sputtering deposition of cerium oxide and Pt of 30 nm thick nanoporous films on large surface carbon nanoparticle substrates. Thin film techniques permits to grow the catalyst film characterized by highly dispersed platinum, mostly in ionic Pt2+ state. Such dispersed Pt species show high activity and stability. These new materials ma…
Proton exchange membrane fuel cell made of magnetron sputtered Pt–CeO and Pt–Co thin film catalysts
2015
Abstract Preparation of catalysts for proton exchange membrane fuel cells (PEMFCs) is of growing interest during last years. The magnetron sputtering technique is a promising method of catalyst preparation because it permits to synthesize catalysts in a fast and relatively less expensive way, however control of specific surface and durability of such catalysts still remains the main concern. We tested a single cell PEMFC catalyzed by using exclusively thin film approach by combining state-of-the art Pt-doped cerium oxide anode and a new Pt–Co alloy cathode. We have shown that beside very high mass activity of the catalysts relative to the membrane electrode assembly the catalyst nanoporous …
Preparation of magnetron sputtered thin cerium oxide films with a large surface on silicon substrates using carbonaceous interlayers.
2013
The study focuses on preparation of thin cerium oxide films with a porous structure prepared by rf magnetron sputtering on a silicon wafer substrate using amorphous carbon (a-C) and nitrogenated amorphous carbon films (CNx) as an interlayer. We show that the structure and morphology of the deposited layers depend on the oxygen concentration in working gas used for cerium oxide deposition. Considerable erosion of the carbonaceous interlayer accompanied by the formation of highly porous carbon/cerium oxide bilayer systems is reported. Etching of the carbon interlayer with oxygen species occurring simultaneously with cerium oxide film growth is considered to be the driving force for this effec…
MOCVD growth of porous cerium oxide thin films on silicon substrate
2015
Abstract Porous cerium oxide thin films were grown by pulsed direct liquid injection metal organic chemical vapor deposition (DLI-MOCVD) on silicon substrate, using cerium tetrakis (1-methoxy-2-methyl-2-propanolate) dissolved in cyclohexane as precursor as well as oxygen as oxidant agent. The chemical and morphological characteristics of the films were investigated by XPS, SEM and TEM. The influence of the growth conditions on the morphological features of the thin films and the cerium chemical states are reported and discussed. The decrease of the oxygen and/or alkoxide flow rate induces the decrease of both the film thickness and the porosity of the layer. Moreover, the growth of silicate…
The synthesis of zeolites from dry powders
1995
Summary ZSM-5 was synthesized by different methods with a gradually decreasing water content ending in a reaction mixture with absolutely dry reagents in form of a powder in the complete absence of a solution phase. Amorphous precursors obtained by drying SiO 2 * Al 2 O 3 gels at 650°C were transformed into zeolites in the presence of dried NH 4 F and TPABr. The reaction products were characterized by XRD, REM, TG/DTA, MAS NMR and Electron Micropobe. Pure ZSM-5 or Silicalite-1 was obtained in all cases. Some water is probably formed as a reaction product, but the maximum water pressure is appreciably below the saturation pressure at the given reaction conditions. To explain the formation of…
Chemical Vapour Deposition of Pure Titanium Using a Heated Wire Reactor and TiI4
2017
Master's thesis Renewable Energy ENE500 - University of Agder 2017 An experimental reactor system has been optimized throughout a series of experiments for making titanium tubes from an electrically heated titanium coil filament by a chemical vapour deposition method, based on the original van Arkel-de Boer -process. The titanium is thermally decomposed on the filament from vapourized titanium tetraiodide in a method not seen in similar experiments. The small-scale reactor is built for this purpose, and the associated systems and methods are developed to maintain the optimal conditions for a continuous metal deposition. A filament current control system is made of an Arduino micro-controlle…
A monolayer of a Cu2+-tetraazamacrocyclic complex on glass as the adhesive layer for silver nanoparticles grafting, in the preparation of surface-act…
2011
International audience; A silane-derivatized tetraaza Cu2+ macrocyclic complex is prepared, which forms monolayers on glass surfaces, capable of allowing the further deposition of a stable monolayer of silver nanoparticles, obtaining by this, surfaces that display an enhanced antibacterial activity against Staphylococcus aureus and Escherichia coli.
MoO (x≤2) ultrathin film growth from reactions between metallic molybdenum and TiO2 surfaces
2001
Abstract Exposures to oxygen at room temperature and annealings under vacuum were carried out on deposits obtained from molybdenum interacting with (1 1 0) TiO 2 surfaces in order to obtain molybdenum oxide ultra thin films. Exposures to oxygen at room temperature show that the interfacial molybdenum oxide layers resulting from the TiO 2 /Mo interactions are inactive towards oxygen whereas the metallic molybdenum clusters, which grew on top of the interfacial layers, oxidise into MoO 3 . Besides, during annealings under vacuum, substrate oxygen anions can diffuse into the deposit. Thus, between 400 and 500°C, molybdenum oxide layers are progressively oxidised into MoO 2 . Moreover, from the…
Reactivity between molybdenum and TiO2(110) surfaces: evidence of a sub-monolayer mode and a multilayer mode
2005
Small amounts of molybdenum (from 0.03 to 1.3 eqML) were deposited on non-stoichiometric TiO 2 (1 1 0) surface. The deposits were investigated by means of LEED and X-ray/UV photoemission using synchrotron radiation. For the smallest coverage (<0.2 eqML), deposition leads to oxidation of molybdenum into species close to Mo 4+ .In such a case, states appearing in TiO 2 band gap are mainly due to reduced titanium. For higher coverages, metallic behaviour of molybdenum is observed. This phenomenon was explained, thanks to first principle calculations, as a decrease of the Mo-O interactions for the benefit of the Mo-Mo interactions as the surface molybdenum atom density increases.
ChemInform Abstract: Catenanes and Threaded Systems: From Solution to Surfaces
2009
Functional catenanes and threaded systems able to perform controllable mechanical motions are ideally suited for the design of molecular devices displaying mechanical, electronic, information or sensing functions. These systems have been extensively studied in solution phase and numerous examples of stimuli-driven molecular shuttles have been reported. However, for fully developing their potential applications, they must be interfaced with the macroscopic world. To achieve this objective, in the last few years catenanes and rotaxanes have been organized over surfaces in the form of chemisorbed monolayers or physisorbed monolayers, multilayers and thin films. This tutorial review summarizes …