Search results for "medium"
showing 10 items of 3746 documents
Tritium release from breeding blanket materials in high magnetic field
2007
Abstract Under the operating conditions of a fusion reactor, the blanket materials: ceramic and Be pebbles will be at a high temperature (up to 1123 K), under action of intense radiation (up to 10 19 n m −2 s −1 ) and magnetic field (MF) up to 7–10 T. In order to introduce action of radiation and MF in post-irradiation investigations of the tritium release from the blanket materials, a special rig for thermo-annealing of pre-irradiated samples at a high temperature up to 1120 K under irradiation with fast electrons of 5 MeV and dose rate 14 MGy/h in MF up to 1.7 T was used for this study. A delay of the tritium release in MF of 2.4 T at thermo-annealing of the lithium orthosilicate Li 4 S…
Au nanowire junction breakup through surface atom diffusion.
2018
Metallic nanowires are known to break into shorter fragments due to the Rayleigh instability mechanism. This process is strongly accelerated at elevated temperatures and can completely hinder the functioning of nanowire-based devices like e.g. transparent conductive and flexible coatings. At the same time, arranged gold nanodots have important applications in electrochemical sensors. In this paper we perform a series of annealing experiments of gold and silver nanowires and nanowire junctions at fixed temperatures 473, 673, 873 and 973 K (200 degrees C, 400 degrees C, 600 degrees C and 700 degrees C) during a time period of 10 min. We show that nanowires are especially prone to fragmentatio…
Experimental and theoretical evidence for substitutional molybdenum atoms in theTiO2(110)subsurface
2006
Molybdenum was deposited at room temperature on the ${\mathrm{TiO}}_{2}(110)$ surface in the 0--1.3 equivalent monolayer (eqML) range and was then annealed at $400\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ in order to reach a kind of equilibrium state. A threshold was found in the behavior of the deposit: below 0.2 eqML, substitutional molybdenum occurs in titanium sites located under the bridging oxygen atoms of the ${\mathrm{TiO}}_{2}(110)$ surface. In this position, molybdenum atoms are in a structural and chemical ${\mathrm{MoO}}_{2}$-like environment. Density-functional theory calculations show that this molybdenum site is actually the most stable one in …
Understanding the Conversion Process of Magnetron-Deposited Thin Films of Amorphous ReO$_x$ to Crystalline ReO$_3$ upon Thermal Annealing
2020
Crystal growth & design 20(9), 6147 - 6156 (2020). doi:10.1021/acs.cgd.0c00848
Influence of nanoporous structure on mechanical strength of aluminium and aluminium alloy adhesive structural joints
2006
The influence of surface treatments on the mechanical strength of adhesive joints was investigated. The attention was focused on AA2024 alloy because it is extensively used in both the automotive and aerospace industries. Adhesive joints fabricated with pure aluminium were also investigated in order to evidence possible differences in the surface features after identical treatments. Before joining with a commercial epoxy adhesive, metal substrates were subjected to different kinds of treatment and the surfaces were characterized by SEM analysis. The formation of a microporous surface in the AA2024 alloy, upon etching and anodizing, is discussed on the basis of the role of the intermetallic …
The influence of composition on band gap and dielectric constant of anodic Al-Ta mixed oxides
2015
Al-Ta mixed oxides were grown by anodizing sputter-deposited Al-Ta alloys of different composition. Photocurrent spectra revealed a band gap, Eg, slightly independent on Ta content and very close to that of anodic Ta2O5 (∼4.3 eV) with the exception of the anodic film on Al-10at% Ta, which resulted to be not photoactive under strong anodic polarization. The photoelectrochemical characterization allowed to estimate also the oxides flat band potential and to get the necessary information to sketch the energetic of the metal/oxide/electrolyte interfaces. Impedance measurements allowed to confirm the formation of insulating material and to estimate the dielectric constant of the oxides, which re…
Tailoring of the Solid State Properties of Al–Nb Mixed Oxides: A Photoelectrochemical Study
2013
Al–Nb containing mixed oxides were grown by anodizing sputter-deposited Al–Nb alloys of different compositions. A photoelectrochemical investigation was carried out in order to estimate the band gap, flat band potential, and conductivity type of these oxides as a function of their composition. The dependence of the band gap on the composition of mixed sp–d metal oxides has been rationalized by using a semiempirical correlation between the difference of electronegativity and band gap of oxides proposed in the literature some years ago and recently tested for regular d–d metal mixed oxides. The band gap increase observed as a function of Al content into the oxides seems mainly depending on th…
Anodic alumina membranes as template for the synthesis of 1-D metal oxide and hydroxide nanostructures
2008
Anodic alumina membranes with highly ordered cylindrical pores and tuneable geometry have been prepared (pore diameters=20−200 nm; pore density 1012-1014 pores/m2; thickness: 20-100 mm) by controlling the anodizing process of aluminum in phosphoric, oxalic and sulphuric acid. The influence of different parameters (initial treatment of aluminium surface, composition of electrolyte, temperature and applied potential) on the final characteristics of the membranes have been investigated. The use anodic alumina membranes as template for the electrosynthesis of some metal hydroxides and oxides 1-D nanostructures (nanowires and nanotubes) will be also proved.
Physicochemical characterization and photoelectrochemical analysis of iron oxide films
2013
Iron oxide films with a nanoporous structure were grown by anodizing sputter-deposited Fe in a fluoride containing ethylene glycol solution and annealed under air exposure at different temperatures. X-ray diffraction and Raman spectroscopy allowed to identify the presence of hematite and/or magnetite after thermal treatment for films annealed at T ≥ 400 °C under air exposure. According to GDOES compositional depth profiles, the thermal treatment sensitively reduced the amount of fluoride species incorporated into the film during the anodizing process. A band gap value of ~2.0 eV was estimated for all the investigated layers, while a flat band potential dependent on both the growth condition…
Numerical and experimental investigation of short Au nanorods
2014
The plasmonic properties of Au nanorods (NRs) have been investigated theoretically and experimentally, a system that is of high current interest in relation to various nanophotonics applications. The non-aligned NRs arrays were formed by a seed-mediated growth method that relies on the reduction of metal salt by a weak reduction agent in the presence of preformed metallic seed nanoparticles. We applied the finite-element method to calculations of absorption spectra from gold NRs supported in an aqueous solution. Comparison to experimentally measured spectra is found in a good agreement.