VO2 thin films based active and passive thermochromic devices for energy management applications

VO₂ thin films were fabricated by argon ion beam assisted non-reactive ac dual magnetron sputtering followed by carefully controlled thermal oxidation. This method is known to give high quality compact thin films with uniform high deposition rates. Thin films deposited on both bare glass and indium tin-oxide (ITO) coated glass substrates were studied, respectively, as passive and active thermochromic devices for their electrical and optical switching behaviors. Thin films varying in thicknesses from 65 to 250 nm were investigated. ITO film was used as an integrated heating device to activate the phase transition via an applied bias voltage. Such structures were found to bear several advantages from an application point of view.     

An adaptive remeshing strategy for viscoelastic fluid flow simulations

In the last few years, we have developed a fairly general adaptive finite element solution procedure which can be applied to a large variety of problems. In this paper, this strategy is briefly recalled and applied to the solution of two-dimensional viscoelastic fluid flow problems. A log-conformation formulation recently introduced by Fattal and Kupferman [R. Fattal, R. Kupferman, Time-dependent simulation of viscoelastic flows at high Weissenberg number using the log-conformation representation, J. Non-Newtonian Fluid Mech. 126 (2005) 23-37] was implemented in order to improve the convergence properties of the numerical scheme. We confirm some results obtained in Hulsen, Fattal and Kupferman [M. Hulsen, R. Fattal, R. Kupferman, Flow of viscoelastic fluids past a cylinder at high Weissenberg number: stabilized simulations using matrix logarithm, J. Non-Newtonian Fluid Mech. 127 (2005) 27-39] and in some instances, we show that mesh adaptation allows to almost automatically reproduce accurate results obtained on very fine structured meshes.     

How does γ-irradiation affect the properties of a microfiltration membrane constituted of two polymers with different radiolytic behavior?

The objective of this work is to present the behavior of a fluorinated microporous membrane composed of poly(vinylidene fluoride) (PVDF) mechanically reinforced by a polyamide-66 (PA-66) fabric under γ-irradiation with dose ranging between 0 and 100 kGy, in inert atmosphere and at room temperature. Particular attention was paid to the evolution of mechanical properties, the surface morphology and pores size distribution of this membrane, in order to study the filtration capacity and selectivity with increasing radiation dose. Moreover, the repartition of the generated radicals onto the two components of the membrane was achieved by electron spin resonance (ESR) spectroscopy. Two different regimes are observed depending on the dose range, and a correlation between the mechanical behavior of the membrane and the evolution of the concentration of the radicals in the PA fabric is observed. Globally, the porosity of the surface membrane does not vary whatever the dose may be, but the mechanical properties of the membrane as well as the permeability are strongly affected, even for low radiation dose such as 10 kGy. These results are related to chain scissions on the PA fabric, which occurred preferentially, compared to cross-linking, in the investigated dose range.     

Raman spectra of CuGaS2-x Se x (x=0, 0.5, 1.0)

Summary Raman spectra on the CuGaS_2-x Se _x system (x=0, 0.5, 1.0) are described for the first time. The observed structures are assigned on the basis of the analogies with binary solid solutions. The broadening of theA ₁ sulphur mode seems to indicate the effect of substitutional disorder. Paper presented at the ?V. International Conference on Ternary and Multinary Compounds?, held in Cagliari, September 14–16, 1982.     

Complexing capacity of low-level radioactive waste leachates for Co and Cd using an ion-exchange technique

Low-level radioactive wastes (LLRW) intended for disposal at Chalk River laboratories (CRL) are composed primarily (>90% by volume) of organic material (paper, used clothing, packaging material, mop heads, etc.). Upon contact with water, microbial degradation of this material will produce dissolved organic matter (DOM) which has the potential to change the speciation and mobility of radionuclides in soils. The determination of the aqueous speciation of nuclides will provide a tool that will enable a better prediction of the behaviour of nuclides and their potential to migrate in soils.

This work is one aspect of the characterisation of the DOM produced by the microbial degradation of LLRW. An ion-exchange technique was set up to demonstrate the applicability of the method to determine the complexing capacity of the DOM in a difficult matrix. Leachates from a LLRW degradation experiment were used with two radioisotopes (¹⁰⁹Cd and ⁶⁰Co). The method allows the determination of the free-ion content of a metal in a solution, which also leads to the determination of the complexed fraction.

The leachate matrix consisted of 0.1 M ionic strength of inorganic salts, with 4177 mg C/l of DOM. The complexing capacity of the DOM in the leachates was 50 μg/l for Co, and 0.54 μg/l for Cd. This represents 0.0028% and 0.000015% of the available DOM sites to Co and Cd, respectively. The conditional stability constant of the DOM with Cd was slightly higher (log β = 1.98) than that of acetic acid, whereas it was ambiguous for Co (log β = 2.02 or 2.54). DOM fouling did not constitute a problem, and the method could be used for other radionuclides and metals.     

A reaction-based chromogenic and fluorescent chemodosimeter for fluoride anions

An innovative trihexylsilylacetylene-containing BODIPY dye was designed and proved to be a highly selective, sensitive, and fast chromogenic and fluorescent chemodosimeter for fluorides.     

Fraternal twin iridium hemicage chelates

The synthesis and complete photophysical characterization of rigidified neutral hemicage iridium complexes are presented. The hemicage ligands were obtained via a modular synthesis, which will facilitate the expansion of future hemicage syntheses. Slight variations in structure between the two iridium hemicage podates reveal subtle differences in photophysical behavior, which will aid in the design of functional materials. A parallel computational investigation corroborates the experimental findings. The insight gleaned from this study will have an impact for the design of iridium-based luminophores for OLED-type applications.     

Fluoride glass Raman fiber laser at 2185 nm

We report on the first Raman laser based on a fluoride glass optical fiber. The Raman fiber laser was pumped by a 9.6?WTm3+:silica CW fiber laser operating at a wavelength of 1940?nm. A maximum output power of 580?mW was measured at 2185.1?nm, corresponding to a frequency shift of 579?cm(-1) (17.37?THz). We observed a threshold power of 3.8?W and a low power slope efficiency of 29% with respect to the launched pump power. Using those results and the known fiber parameters, we estimated a Raman gain peak value of 3.52*10(-14)?m/W, which is lower than the previously reported values.