Rhelogical properties of molten crystallized glass
Formulation of nuclear waste conditioning glass results from a compromise between waste loading, glass technological feasibility and its long-term behavior. Up to now borosilicate glasses formulated at CEA and elaborated at La Hague plant by Orano to condition nuclear waste are homogeneous when molten. That means that today glass formulation is determined such as solubility limits of each constituting elements of waste aren’t exceeded in order to avoid phase separation (implying typically Mo, S, P) and/or crystallization (implying typically Fe, Ni, Cr, Zn, Al, Ce, Cs, Ti…) leading to a two-phase molten glass (liquid-liquid or liquid-solid).Today CEA would like to explore the impact of solid particles in suspension in the molten glass and in the final glass canister on respectively the glass technological feasibility and its long-term behaviour.
The proposed study focuses on the molten glass technological feasibility. The presence of solid heterogeneities in the melt is known to lead to a modification of some of its physical properties – notably its rheology, as well as thermal and electrical conductivities, and can generate settling phenomena. Yet these properties are in the heart of vitrification process control and modelling. This study will then investigate the impact of crystals in the molten glass on vitrification process control and modelling.
Simulation of thermal exchange between fluid and structure in turbulent channels
There is presently a huge effort in Europe for the Development of high power (PW range), high repetition rate (1-10 Hz) lasers: the ELI project in three countries of Eastern Europe , the Apollon program in France have the objective to install multipetawatt high repetition rate lasers for scientific research and applications in various fields of physics. These large projects result in – and demand – an increased mastering of most challenging issues in laser technology; at high repetition rate one of the greatest issues consists in the cooling of the laser amplifiers for the highest repetition rates. In order to master this technology, CEA (Grenoble and Saclay, with a collaboration with Grenoble/LEGI) has decided to start an R&D program, with the following tasks to perform: (i) simulation of the cooling of amplifiers; (ii) validation of the calculations; (iii) design of an appropriate cooling system dedicated to future high power high repetition rate lasers: for this, cryogenic helium gas is a very interesting fluid, as working at low temperature for laser amplification allows a better thermal conductivity of the amplifiers (consequently a better uniformity of their temperature), and an increased efficiency of the laser amplification.
This postdoc position is associated with the first (simulation) task.
Synthesis of inorganic monoliths functionalized with nanoparticles
Since 2008, the "Institut de Chimie Separative de Marcoule" (ICSM) and specifically the "Laboratoire des Nanomateriaux pour l’Energie et le Recyclage" (LNER) has developped specific skills in synthesis routes and studies of porous materials (BET, TEM, SEM, SAXS).
This post-doctoral position is devoted to the synthesis of inorganic monoliths using high internal phase emulsion (HIPE) as soft template, and particularly to the functionalization of these materials with nanoparticles (NP).
The use of an emulsion in the procedure allows to consider innovative ways of functionalizing the material. For example, the oil-water interface in the emulsion may be the site of adsorption of nanoparticles of interest for a given application. In our case the goal is to prepare an emulsion with high internal phase (> 50% vol) stabilized by both surfactants (required for mesoporosity) and NP of interest to functionalize the macroporosity. NPs are chosen to cover liquid effluent decontamination (zeolite, nonatitanate, clathrate)
New nanostructurated fluorescent materials for the detection of volatile organic compounds.
The presence in indoor environments of many substances and (geno-)toxic, allergenic and infectious agents with pathogenic effects is well known. The on-site detection of these
substances has become a strong need, related to public health concerns. To respond to this need and enable the development of sensitive and selective ’field-deployable chemical sensors’, different technological solutions are being considered (conductimetric, electrochemical, piezoelectric, electro-mechanical, optical based systems…). Among all these methods, those based on the use of fluorescence phenomena are particularly interesting because of the inherently high sensitivity (lower limit of detection) of the technique and the possibility it offers to develop low cost, small size and low
energy consuming devices.
The proposal falls into this context and aims at evaluating the potentialities of new nanostructurated organic materials for the detection of indoor air trace pollutants by fluorescence change monitoring. This work will be done in straight collaboration with the Laboratoire Chimie des Polymères (UMR7610-CNRS/UPMC Paris VI) specialized in the synthesis
of functionalized organogels. More precisely, we propose to develop new highly porous supramolecular materials serving either as substrate for the sensitive fluorescent polymer or functionalised so as to directly detect and recognize the vapor pollutant.
The physico-chemical properties of these new materials will be examined by different techniques. Their performances in the presence of target pollutants (formaldehyde, acetaldehyde) and potentially interferants will be evaluated. Finally, the most interesting materials will be integrated into a functional prototype.