Microstructure and photocatalytic activity of APS coatings obtained from different TiO2 nanopowders

In recent years, intense research has shown that thermal spray techniques, especially atmospheric plasma spraying (APS), can be used to obtain nanostructured TiO2 coatings with effective photocatalytic activity. This study compares the photocatalytic activity of APS coatings obtained from different powders: two nanostructured TiO2 powders produced by spray-drying of two TiO2 nanosuspensions with different solids contents, one spray-dried powder obtained from a suspension comprising a mixture of submicronic and nanometric TiO2 particles and finally one commercial, nanostructured, TiO2 spray-dried powder. All powders were characterised by XRD, FEG-ESEM, granule size distribution, and a flowability evaluation. Feedstock powders were then deposited on austenitic stainless steel coupons using APS. Hydrogen or helium was used as secondary plasma gas. Coating microstructure and phase composition were characterised using FEG-ESEM and XRD techniques; coating anatase content was quantified by the Rietveld method. A significant amount of anatase to rutile transformation was found to take place during the plasma spraying process. In general, the coatings had a bimodal microstructure characterised by the presence of completely fused areas in addition to non-molten areas consisting of agglomerates of anatase nanoparticles. Results also showed that anatase content and porosity of the coatings largely depend on the secondary plasma gas nature, as well as on the characteristics of the feedstock. Finally the photocatalytic activity of the coatings was determined by measuring the degradation of methylene blue dye in an aqueous solution. A reasonably good fit of a first-order kinetic model to the experimental data was found for all coatings. The values of the kinetic constant were related to feedstock characteristics as well as to plasma spraying conditions. (C) 2012 Elsevier B.V. All rights reserved.Bordes, MC.; Vicent, M.; Moreno, A.; Moreno, R.; Borrell Tomás, MA.; Salvador Moya, MD.; Sanchez, E. (2013). Microstructure and photocatalytic activity of APS coatings obtained from different TiO2 nanopowders. Surface and Coatings Technology. 220:179-186. doi:10.1016/j.surfcoat.2012.08.059S17918622

Life cycle assessment of using powder and liquid precursors in plasma spraying : the case of yttria-stabilized zirconia

International audiencePlasma spraying using liquid precursors makes possible the production of finely-structured coatings and thin coatings. This technology has been investigated for nearly ten years in many laboratories and applications are now emerging, using conventional plasma equipment except for the feedstock injection system. While superior quality is expected from the nano-structured coatings, the question remains as to the impacts of using liquid precursors on the environment. In this study, we used the life cycle assessment (LCA) methodology to compare the conventional plasma spray process using powder feedstock, with injection of the precursor in the form of a liquid solution or suspension. The LCA methodology consists of identifying and comparing the environmental impacts of feedstock, energy inputs, products and emissions (solid, liquid and gaseous) of these two alternatives. The LCA study was carried out using the SimaPro program developed in the Netherlands and a peer-reviewed database of upstream materials and energy (EcoInvent v.2). The specific application studied was the plasma spraying of yttria-stabilized zirconia

GOULET ET RADE DE BREST : ESSAI DE GÉOLOGIE SOUS-MARINE

National audienceDes études géophysiques et des carottages effectués dans la partie nord de la rade de Brest et des levés géologiques nouveaux dans les régions côtières permettent aux auteurs de préciser la géologie sous-marine de ce secteur et d’en proposer une carte. Celle-ci est conforme au style des régions émergées avoisinantes. On y note toutefois la disparition, par laminage le long de la faille de l’Elorn, des quartzites skiddaviens de la Roche Maurice.L’étude des sédiments meubles récoltés au cours des carottages permet de retracer l’histoire quaternaire récente de la rade de Brest

Le problème des strandflats en cinq pays de hautes latitudes

No abstract available

Analysis of current research addressing complementary use of life-cycle assessment and risk assessment for engineered nanomaterials: have lessons been learned from previous experience with chemicals?

While it is generally agreed that successful strategies to address the health and environmental impacts of engineered nanomaterials (NM) should consider the well-established frameworks for conducting life cycle assessment (LCA) and risk assessment (RA), scientific research and specific guidance on how to practically apply these methods are still very much under development. This paper evaluates how research efforts have applied LCA and RA together for NM, particularly reflecting on previous experiences with applying these methods to chemicals. Through a literature review and a separate analysis of research focused on applying LCA and RA together for NM, it appears that current research efforts have taken into account some key “lessons learned” from previous experience with chemicals while many key challenges remain for practically applying these methods to NM. We identified two main approaches for using these methods together for NM: “LC-based RA” (traditional RA applied in a life cycle perspective) and “RA-complemented LCA” (conventional LCA supplemented by RA in specific life cycle steps). Hence, the latter is the only identified approach which genuinely combines LC- and RA-based methods for NM-risk research efforts to date as the former is rather a continuation of normal RA according to standard assessment procedures (e.g. REACH). Both these approaches along with recommendations for using LCA and RA together for NM are similar to those made previously for chemicals, and thus, there does not appear to be much progress made specific for NM. We have identified one issue in particular that may be specific for NM when applying LCA and RA at this time: the need to establish proper dose metrics within both methods.JRC.I.4-Nanobioscience