<jats:title>Abstract</jats:title> <jats:p>Thorium Phosphate-Diphosphate (TPD) c... more <jats:title>Abstract</jats:title> <jats:p>Thorium Phosphate-Diphosphate (TPD) can be considered as a potential matrix for the immobilization of actinides and especially for the plutonium coming from dismantled nuclear weapons. The capability of this solid to form solid solutions by substitution of thorium by tetravalent uranium, neptunium or plutonium is rather high. The synthesis of sintered pellets of thorium-uranium(IV) phosphate-diphosphate was successfully performed. Their density reached 95–99% of the value calculated from XRD data. The open and closed porosities were equal to 2–3% each. The resistance of the TPD and derivative solid solutions to aqueous corrosion are also very good. Leaching tests of powdered samples containing tetravalent plutonium or uranium showed that the normalized dissolution rate remained low (between 10−5 and 10−6 g/(m2.d)) even in acidic media. For tetravalent actinides, the saturation of the leachate seems to be controlled by the precipitation of the thorium phosphate-hydrogenphosphate hydrate which solubility product was found to be KS,0°* = 10−66.6 ± 1. This very low value allows a supplementary delay of the actinides migration in the hypothesis of their release in the leachate from the matrix.</jats:p>
Several compositions of new precursor of thorium–uranium (IV) phosphate–diphosphate solid solutio... more Several compositions of new precursor of thorium–uranium (IV) phosphate–diphosphate solid solutions (Th4−xUx(PO4)4P2O7, called β-TUPD) were synthesized in closed PTFE containers either in autoclave (160°C) or on sand bath (90–160°C). All the samples appeared to be single phase. From XRD data and TEM observations, the diffraction lines matched well with that of pure thorium phosphate–hydrogenphosphate hydrate (TPHPH), Th2(PO4)2(HPO4)·H2O, which confirmed the
HAL (Le Centre pour la Communication Scientifique Directe), 1999
This work presents a feasibility study for the revalorization of ultimate glassy wastes. A new pr... more This work presents a feasibility study for the revalorization of ultimate glassy wastes. A new process was used to convert these wastes into high value structural composite materials that can be used as brake friction materials. As significant amounts of vitrified domestic waste residues (20 to 60 wt%) were used to manufacture these composite materials, this revalorization process is particularly promising in the context of clean technologies and sustainable development as an alternative to the storage of wastes. Thus the aim of this study was to determine the feasibility of using glassy wastes as friction material in automotive brakes and, moreover, to assess whether this revalorization technique of ultimate wastes is both economical viable and environmentally friendly. Specific mechanical properties (friction, wear rate etc) were measured and appeared to be better than those of conventional commercial brake pads. To assess the environmental impact of these composite materials, risk assessment studies were conducted to evaluate the remobilization of hazardous species such as heavy metals that are concentrated in the wastes. Leaching tests were conducted to simulate the effects of weathering. The alteration solutions were analyzed by ICP-MS to evaluate the dissolution rate of the wastes matrix and the amount of heavy metals released. Thermal shock experiments were conducted with laser ablation and ICP-MS to monitor the secondary products rejected at high temperature. Reutilization of wastes for friction applications appeared to be an economically viable opportunity to converse and valorize ultimate glassy wastes respecting environmental regulations.
Due to their ability to undergo a refractive index change (Δn) induced by appropriate UV irradiat... more Due to their ability to undergo a refractive index change (Δn) induced by appropriate UV irradiation and thermal development, Photo-Thermo-Refractive (PTR) glasses are candidate materials for use in optical applications such as hologram recording, optical data storage, or spectral filters. Although this induced index modulation (Δn) has been characterized in terms of its optical ramifications, glass scientists are working to understand more clearly, the underlying mechanisms associated with the photo-induced crystallization process. For example, the phase, concentration and size of crystals responsible for the induced index change, the diffusion and growth process leading to the resultant optical behavior, and the precise role of the active components of PTR glasses, has yet to be completely elucidated. Numerous techniques have been employed to address these questions and this paper reports results of sample preparation and analysis of PTR glasses using Transmission Electron Microscopy (TEM).
Colloids and Surfaces A: Physicochemical and Engineering Aspects, Nov 1, 2017
The use of cerium dioxide manufactured nanoparticles (CeO2 MNPs) at a large scale in the industry... more The use of cerium dioxide manufactured nanoparticles (CeO2 MNPs) at a large scale in the industry, automotive and everyday products is resulting in a continuous emission and release of CeO2 MNPs to the aquatic environments. In such complex systems, MNPs interact with water components, including biopolymers, resulting in MNP coating which give a new environmental identity to the MNPs and greatly influence their fate, transport and biological impact. MNP surface properties, aggregation, media composition such as ionic composition and pH, strongly influence the importance of natural organic matter coating and coating stability with time. In our study, we are using alginate, a relevant surrogate of natural organic polysaccharides, to coat CeO2 MNPs under different conditions from ultrapure water to synthetic and natural waters. First, the most favourable conditions of alginate coating are defined and then the stability of this coating in changing pH condition is investigated. Then alginate coating impact, at variable alginate concentration, is studied in synthetic and natural waters and comparison is made with ultrapure water. The possible interaction mechanisms between alginate, CeO2, dissolved ions (in particular divalent cations) and natural inorganic compounds are discussed. Our finding demonstrates that alginate concentration, solution pH and presence of divalent cations are key parameters defining the stability and effect of alginate coating and that once formed the biopolymer coating is found irreversible with time and when changing the solution chemistry.
The green micro-alga Chlamydomonas reinhardtii sequesters Cd as vacuolar Cd polyphosphate granule... more The green micro-alga Chlamydomonas reinhardtii sequesters Cd as vacuolar Cd polyphosphate granules and Cd–thiol, diffused in the whole cell.
<jats:title>Abstract</jats:title> <jats:p>Thorium Phosphate-Diphosphate (TPD) c... more <jats:title>Abstract</jats:title> <jats:p>Thorium Phosphate-Diphosphate (TPD) can be considered as a potential matrix for the immobilization of actinides and especially for the plutonium coming from dismantled nuclear weapons. The capability of this solid to form solid solutions by substitution of thorium by tetravalent uranium, neptunium or plutonium is rather high. The synthesis of sintered pellets of thorium-uranium(IV) phosphate-diphosphate was successfully performed. Their density reached 95–99% of the value calculated from XRD data. The open and closed porosities were equal to 2–3% each. The resistance of the TPD and derivative solid solutions to aqueous corrosion are also very good. Leaching tests of powdered samples containing tetravalent plutonium or uranium showed that the normalized dissolution rate remained low (between 10−5 and 10−6 g/(m2.d)) even in acidic media. For tetravalent actinides, the saturation of the leachate seems to be controlled by the precipitation of the thorium phosphate-hydrogenphosphate hydrate which solubility product was found to be KS,0°* = 10−66.6 ± 1. This very low value allows a supplementary delay of the actinides migration in the hypothesis of their release in the leachate from the matrix.</jats:p>
Several compositions of new precursor of thorium–uranium (IV) phosphate–diphosphate solid solutio... more Several compositions of new precursor of thorium–uranium (IV) phosphate–diphosphate solid solutions (Th4−xUx(PO4)4P2O7, called β-TUPD) were synthesized in closed PTFE containers either in autoclave (160°C) or on sand bath (90–160°C). All the samples appeared to be single phase. From XRD data and TEM observations, the diffraction lines matched well with that of pure thorium phosphate–hydrogenphosphate hydrate (TPHPH), Th2(PO4)2(HPO4)·H2O, which confirmed the
HAL (Le Centre pour la Communication Scientifique Directe), 1999
This work presents a feasibility study for the revalorization of ultimate glassy wastes. A new pr... more This work presents a feasibility study for the revalorization of ultimate glassy wastes. A new process was used to convert these wastes into high value structural composite materials that can be used as brake friction materials. As significant amounts of vitrified domestic waste residues (20 to 60 wt%) were used to manufacture these composite materials, this revalorization process is particularly promising in the context of clean technologies and sustainable development as an alternative to the storage of wastes. Thus the aim of this study was to determine the feasibility of using glassy wastes as friction material in automotive brakes and, moreover, to assess whether this revalorization technique of ultimate wastes is both economical viable and environmentally friendly. Specific mechanical properties (friction, wear rate etc) were measured and appeared to be better than those of conventional commercial brake pads. To assess the environmental impact of these composite materials, risk assessment studies were conducted to evaluate the remobilization of hazardous species such as heavy metals that are concentrated in the wastes. Leaching tests were conducted to simulate the effects of weathering. The alteration solutions were analyzed by ICP-MS to evaluate the dissolution rate of the wastes matrix and the amount of heavy metals released. Thermal shock experiments were conducted with laser ablation and ICP-MS to monitor the secondary products rejected at high temperature. Reutilization of wastes for friction applications appeared to be an economically viable opportunity to converse and valorize ultimate glassy wastes respecting environmental regulations.
Due to their ability to undergo a refractive index change (Δn) induced by appropriate UV irradiat... more Due to their ability to undergo a refractive index change (Δn) induced by appropriate UV irradiation and thermal development, Photo-Thermo-Refractive (PTR) glasses are candidate materials for use in optical applications such as hologram recording, optical data storage, or spectral filters. Although this induced index modulation (Δn) has been characterized in terms of its optical ramifications, glass scientists are working to understand more clearly, the underlying mechanisms associated with the photo-induced crystallization process. For example, the phase, concentration and size of crystals responsible for the induced index change, the diffusion and growth process leading to the resultant optical behavior, and the precise role of the active components of PTR glasses, has yet to be completely elucidated. Numerous techniques have been employed to address these questions and this paper reports results of sample preparation and analysis of PTR glasses using Transmission Electron Microscopy (TEM).
Colloids and Surfaces A: Physicochemical and Engineering Aspects, Nov 1, 2017
The use of cerium dioxide manufactured nanoparticles (CeO2 MNPs) at a large scale in the industry... more The use of cerium dioxide manufactured nanoparticles (CeO2 MNPs) at a large scale in the industry, automotive and everyday products is resulting in a continuous emission and release of CeO2 MNPs to the aquatic environments. In such complex systems, MNPs interact with water components, including biopolymers, resulting in MNP coating which give a new environmental identity to the MNPs and greatly influence their fate, transport and biological impact. MNP surface properties, aggregation, media composition such as ionic composition and pH, strongly influence the importance of natural organic matter coating and coating stability with time. In our study, we are using alginate, a relevant surrogate of natural organic polysaccharides, to coat CeO2 MNPs under different conditions from ultrapure water to synthetic and natural waters. First, the most favourable conditions of alginate coating are defined and then the stability of this coating in changing pH condition is investigated. Then alginate coating impact, at variable alginate concentration, is studied in synthetic and natural waters and comparison is made with ultrapure water. The possible interaction mechanisms between alginate, CeO2, dissolved ions (in particular divalent cations) and natural inorganic compounds are discussed. Our finding demonstrates that alginate concentration, solution pH and presence of divalent cations are key parameters defining the stability and effect of alginate coating and that once formed the biopolymer coating is found irreversible with time and when changing the solution chemistry.
The green micro-alga Chlamydomonas reinhardtii sequesters Cd as vacuolar Cd polyphosphate granule... more The green micro-alga Chlamydomonas reinhardtii sequesters Cd as vacuolar Cd polyphosphate granules and Cd–thiol, diffused in the whole cell.
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Papers by Philippe Le Coustumer