Modélisation thermodynamique et cinétique de la réduction de l'acide nitrique concentré.

In the process of treatment of spent nuclear fuel, the dissolution step in concentrated nitric acid is essential. These environments of dissolution, very acid and oxidants have a corrosive significant power to the constituent materials of the facilities Industrial (titanium, zirconium, stainless steels). In some very specific cases (areas condensation, media not renewed), reduction of nitric acid can lead to international displacement of the corrosion potential of these steels, resulting in their field transpassif. The passive layer is then dissolved and a phenomenon of intergranular corrosion is generally observed. The acceleration of the reduction of nitric acid is originally from. This phenomenon, but the causes of this acceleration, closely related to the mechanism of reduction are still unclear. The objective of this study is to determine and quantify thebasic steps of the mechanism of reduction of concentrated nitric acid. As a first step, a thermodynamic simulation helped identify themajority species in liquid and gaseous nitric acid of 0,5 solutions phases MOL. L - 20 mol 1. L - 1 at 25 ° C. Some stable compounds such as nitrous acid or dioxide nitrogen, could then be seen as reactive in the mechanism of reduction. Then, an electrochemical experimental study, coupled with analytical techniques (spectroscopies infrared and UV-visible) allowed to speculate on the reactions put into play during the reduction of nitric acid 4 mol. L - 1 at 40 ° C in inert electrode (gold and) Platinum). It appears that the process of reduction depends on the cathodic overvoltage, and three areas of potential were identified. However, some elements of the mechanism could not be identified by the experience. A kinetic modeling of steady state and the impedance was then made for a device to gold disc rotating, in order to raise some uncertainties, discuss and quantify the reduction process. Finally, the application of this kinetic model to the first results of a study electrochemical on steel 304L allowed to discuss if the mechanism proposed on electrode inert is similar on this material.Dans le processus de traitement du combustible nucléaire usé, l’étape de dissolution dans l’acide nitrique concentré est essentielle. Ces milieux de dissolution, très acides et oxydants possèdent un pouvoir corrosif important vis-à-vis des matériaux constitutifs des installations industrielles (titane, zirconium, aciers inoxydables). Dans certains cas très spécifiques (zones de condensation, milieux non renouvelés), la réduction de l’acide nitrique peut entrainer un déplacement du potentiel de corrosion de ces aciers, les entrainant dans leur domaine transpassif. La couche passive se dissout alors et un phénomène de corrosion intergranulaire est généralement observé. L’accélération de la réduction de l’acide nitrique est à l’origine de ce phénomène, mais les causes de cette accélération, étroitement liées au mécanisme de réduction sont encore mal connues. L’objectif de cette étude est de déterminer et quantifier les étapes élémentaires du mécanisme de réduction de l’acide nitrique concentré. Dans un premier temps, une simulation thermodynamique a permis d’identifier les espèces majoritaires dans les phases liquide et gazeuse de solutions d’acide nitrique de 0,5 mol.L-1 à 20 mol.L-1 à 25°C. Certains composés stables, tels que l’acide nitreux ou le dioxyde d’azote, ont alors pu être envisagés comme réactifs dans le mécanisme de réduction. Ensuite, une étude expérimentale électrochimique, couplée à des techniques analytiques (spectroscopies infrarouge et UV-visible) a permis d’émettre des hypothèses sur les réactions mises en jeu lors de la réduction de l’acide nitrique 4 mol.L-1 à 40°C sur électrode inerte (or et platine). Il apparaît alors que le processus de réduction dépend de la surtension cathodique, et trois zones de potentiels ont été identifiées. Cependant, certains éléments du mécanisme n’ont pas pu être identifiés par l’expérience. Une modélisation cinétique de l’état stationnaire et de l’impédance a alors été effectuée pour un dispositif à disque d’or tournant, afin de lever certaines indéterminations, discuter et quantifier le processus de réduction. Enfin, l’application de ce modèle cinétique aux premiers résultats d’une étude électrochimique sur acier 304L a permis de discuter si le mécanisme proposé sur électrode inerte est similaire sur ce matériau

Automatic generation of alignments for 3D QSAR analyses

Many 3D QSAR methods require the alignment of the molecules in a dataset, which can require a fair amount of manual effort in deciding upon a rational basis for the superposition. This paper describes the use of FBSS, a pro-ram for field-based similarity searching in chemical databases, for generating such alignments automatically. The CoMFA and CoMSIA experiments with several literature datasets show that the QSAR models resulting from the FBSS alignments are broadly comparable in predictive performance with the models resulting from manual alignments

Modélisation thermodynamique et cinétique de la réduction de l'acide nitrique concentré

Dans le processus de traitement du combustible nucléaire usé, l étape de dissolution dans l acide nitrique concentré est essentielle. Ces milieux de dissolution, très acides et oxydants possèdent un pouvoir corrosif important vis-à-vis des matériaux constitutifs des installations industrielles (titane, zirconium, aciers inoxydables). Dans certains cas très spécifiques (zones de condensation, milieux non renouvelés), la réduction de l acide nitrique peut engendrer un déplacement du potentiel de corrosion de ces aciers, les entrainant dans leur domaine transpassif. La couche passive se dissout alors et un phénomène de corrosion intergranulaire est généralement observé. L accélération de la réduction de l acide nitrique est à l origine de ce phénomène, mais les causes de cette accélération, étroitement liées au mécanisme de réduction sont encore mal connues. L objectif de cette étude est de déterminer et quantifier les étapes élémentaires du mécanisme de réduction de l acide nitrique concentréPARIS-BIUSJ-Biologie recherche (751052107) / SudocSudocFranceF

Electrochemical Li-ion batteries modelisation for EV

International audienc

Electrochemical impedance spectroscopy applied for investigating cathodic and anodic processes of corrosion in HNO3

International audienc

Operando nuclear magnetic resonance spectroscopy: Detection of the onset of metallic lithium deposition on graphite at low temperature and fast charge in a full Li-ion battery

International audienceLithium-ion batteries are at the core of the democratisation of electric transportation and portative electronic devices. However, fast and/or low temperature charge induce performance loss, mainly through lithium plating, a degrading mechanism. In this report, 7 Li operando Nuclear Magnetic Resonance spectroscopy is used to detect the onset of metastable lithium deposits in an NMC622/graphite cell at 0°C and fast charge. An operando setup, compatible with low temperatures, was developed with special attention to the pressure applied on the electrodes/separator stack and noise reduction to enable early detection and good time-resolution. Direct detection of metallic lithium enables drawing correlations between lithium plating and electrochemical data

A PEG-borate ester solid-state polymer electrolyte to fabricate a Li 6 PS 5 Cl-rich composite for a Li metal battery

A Li 6 PS 5 Cl-rich composite is prepared using a PEG-borate ester solid-state polymer electrolyte (BSPE)

Study protocol comparing the ethical, psychological and socio-economic impact of personalised breast cancer screening to that of standard screening in the "My Personal Breast Screening" (MyPeBS) randomised clinical trial.

BACKGROUND: The MyPeBS study is an ongoing randomised controlled trial testing whether a risk-stratified breast cancer screening strategy is non-inferior, or eventually superior, to standard age-based screening at reducing incidence of stage 2 or more cancers. This large European Commission-funded initiative aims to include 85,000 women aged 40 to 70 years, without prior breast cancer and not previously identified at high risk in six countries (Belgium, France, Italy, Israel, Spain, UK). A specific work package within MyPeBS examines psychological, socio-economic and ethical aspects of this new screening strategy. It compares women's reported data and outcomes in both trial arms on the following issues: general anxiety, cancer-related worry, understanding of breast cancer screening strategy and information-seeking behaviour, socio-demographic and economic characteristics, quality of life, risk perception, intention to change health-related behaviours, satisfaction with the trial. METHODS: At inclusion, 3-months, 1-year and 4-years, each woman participating in MyPeBS is asked to fill online questionnaires. Descriptive statistics, bivariate analyses, subgroup comparisons and analysis of variations over time will be performed with appropriate tests to assess differences between arms. Multivariate regression models will allow modelling of different patient reported data and outcomes such as comprehension of the information provided, general anxiety or cancer worry, and information seeking behaviour. In addition, a qualitative study (48 semi-structured interviews conducted in France and in the UK with women randomised in the risk-stratified arm), will help further understand participants' acceptability and comprehension of the trial, and their experience of risk assessment. DISCUSSION: Beyond the scientific and medical objectives of this clinical study, it is critical to acknowledge the consequences of such a paradigm shift for women. Indeed, introducing a risk-based screening relying on individual biological differences also implies addressing non-biological differences (e.g. social status or health literacy) from an ethical perspective, to ensure equal access to healthcare. The results of the present study will facilitate making recommendations on implementation at the end of the trial to accompany any potential change in screening strategy. TRIAL REGISTRATION: Study sponsor: UNICANCER. My personalised breast screening (MyPeBS). CLINICALTRIALS: gov (2018) available at: https://clinicaltrials.gov/ct2/show/NCT03672331 Contact: Cécile VISSAC SABATIER, PhD, + 33 (0)1 73 79 77 58 ext + 330,142,114,293, [email protected]