Search results for "ALLOYS"
showing 10 items of 1689 documents
Advances in selective conversions by heterogeneous photocatalysis
2010
Selective photocatalytic conversions are offering an alternative green route for replacing environmentally hazardous processes with safe and energy efficient routes. This paper reports the most recent advances in the application of heterogeneous photocatalysis to synthesize valuable compounds by selective oxidation and reduction.
Combining Membrane and Zero Brine Technologies in Waste Acid Treatment for a Circular Economy in the Hot-Dip Galvanizing Industry: A Life Cycle Persp…
2023
AbstractAn innovative approach of combining membrane and zero brine technologies for a joint treatment of industrial liquid waste is investigated regarding its environmental impacts compared to the existing liquid waste treatment. The object of investigation is the generation of waste acid solution by a hot dip galvanizing plant in Sicily, Italy. The waste acid solution contains hydrochloric acid, iron and zinc, which makes it a hazardous waste according to EU classifications. Environmental impacts are studied for two scenarios in the Tecnozinco hot-dip galvanizing plant in Sicily, Italy: (i) the current process of pickling with linear disposal of waste acid and (ii) the pickling combined w…
Random access with repeated contentions for emerging wireless technologies
2017
In this paper we propose ReCo, a robust contention scheme for emerging wireless technologies, whose efficiency is not sensitive to the number of contending stations and to the settings of the contention parameters (such as the contention windows and retry limits). The idea is iterating a basic contention mechanism, devised to select a sub-set of stations among the contending ones, in consecutive elimination rounds, before performing a transmission attempt. Elimination rounds can be performed in the time or frequency domain, with different overheads, according to the physical capabilities of the nodes. Closed analytical formulas are given to dimension the number of contention rounds in order…
Alkoxysilyl substituted oligo(phenylenevinylene)s: chromophores with reactive side chains
2003
The synthesis and properties of highly luminescent oligo(phenylenevinylene)s (OPV) with curable alkoxysilyl groups are described. Two diethoxymethylsilane moieties are connected directly or through flexible spacers to monodisperse alkoxy-substituted OPVs via hydrosilylation of alkinyl and allyloxy groups, Heck reaction with silylstyrene or condensation of aldehydes with aminopropyl silanes. Hydrolysis of the alkoxysilanes yields silanols condensing to curable three-dimensional networks, thus allowing the transformation of small molecules to transparent and fluorescent films with well-defined chromophores.
Alkoxysilylation of π-systems with extended conjugation—reactive chromophores for organic–inorganic hybrid materials
2004
Luminescent stilbenoid chromophores with diethoxysilane end groups are prepared via Heck reactions. Diethoxysilane-substituted styrenes are used as vinylic components, thus allowing the combined connection of the chromophore to the silane moiety with an extension of the π-system. 1,4-Distyrylbenzenes with a terminal bromine are used as coupling partners. The electrical and optical properties the four-ring OPVs are tuned via substitution with donating alkoxy side chains and electron withdrawing cyanide and a naphthyl-1,2,3-oxadiazole moiety. Hydrolysis yields film forming and luminescent cyclosiloxanes.
Tris- and tetrakis-[oligo(phenylenevinylene)]silanes: synthesis and luminescence behaviour
2002
Abstract The connection of three or four monodisperse oligo(phenylenevinylene)s to a central silicon atom is performed via Wittig–Horner reactions. The terminal rings are substituted with alkoxy side chains. Depending on the ratio of the lengths of the rigid conjugated units and the flexible side chains, transparent films can be obtained from several of these trigonal-pyramidal or tetrahedral molecules. An intense fluorescence in the blue-green region is emitted by molecules of either shape. These compounds are interesting as active materials for electro-optical applications due to their intense fluorescence and improved film forming capability.
Advanced fragmentation stage of oxide coating on polymer substrate under biaxial tension
2005
Crack patterns of 100-nm-thick silicon oxide coating on polypropylene film subjected to equibiaxial stress loading are studied experimentally. The loading is achieved by means of a bulging cell mounted under an optical microscope with stepwise pressurization of film specimens. The evolution of the coating fragment area distribution at relatively high strains is modeled using Weibull statistics to describe the coating strength. The fragment area distribution at an advanced fragmentation stage is shown to scale with the average fragment area, the latter being a power function of the applied biaxial strain.
Structure and diffusion of oxygen and silicon interstitials in silicon
1999
Abstract Ab initio quantum chemical simulation of silicon interstitials and oxygen-related defects Oi, V–O2, and V–O4 in oxygen-containing silicon was performed using the embedded molecular cluster model. The defect geometry and electronic structure were studied. The migration activation energy for Oi defect was estimated as 2.73 eV at the atmospheric pressure, and 2.70, 2.68, and 1.92 eV for the lattice compressed by 0.25, 0.37, or 5.0 per cent, respectively. The activation energy of silicon interstitial is not changing with pressure. The molecular cluster used to simulate V–O4 defect with C2v symmetry was shown to have only slight deviation from D2d at atmospheric pressure, a strong devia…
Structural and in situ vibrational study of luminescent cluster assembled silicon thin films
2006
A Low Energy Cluster Beam Deposition apparatus is employed to produce cluster assembled silicon thin films (1-500 nm thick) by using a laser vaporization source. The generated clusters are studied since their formation through time of flight mass spectra and the calculated size in the gas phase are compared with those of the deposited aggregates obtained through Dynamic Scanning Force Microscopy. The deposited material is also studied "in situ" by Raman and infrared spectroscopy. The spectra reveal that the as deposited clusters are hydrogenated with negligible amount of oxide. A comparison of the film properties before and after their air exposure shows that the exposition induces a consis…
Reactivity of commercial silicon and silicides towards copper(I) chloride. Effect of aluminium, calcium and iron on the formation of copper silicide
1998
Abstract The reaction of CuCl with silicon, containing Al, Fe and Ca as impurities, or with silicides (Si2Ca, Si2Fe, Si2Al2Ca, Si8Al6Fe4Ca) has been investigated in the temperature range 200–300°C. For the reaction between CuCl and commercial Si, it was found that, at 282°C, aluminium promotes the reaction between Cu3Si and CuCl while the rate of consumption of Cu3Si is greatly reduced by the presence of iron. The combined action of these two impurities leads to the formation of more copper–silicon alloy. In the presence of mixed silicides, the reaction with CuCl also leads to the formation of Cu3Si. For the quaternary Al–Ca silicide containing iron the rate of formation of Cu3Si is not inc…