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PhD subjects

6 sujets IRAMIS

Dernière mise à jour : 19-04-2018


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• Ultra-divided matter, Physical sciences for materials

 

Linen analysis by R-ray microdiffraction and in-situ tensile test

SL-DRF-18-0741

Research field : Ultra-divided matter, Physical sciences for materials
Location :

Centre de recherche sur les Ions, les Matériaux et la Photonique (CIMAP)

Centre de recherche sur les Ions, les Matériaux et la Photonique (CIMAP)

Saclay

Contact :

Magali MORALES

Starting date : 01-10-2018

Contact :

Magali MORALES

Université de Caen - CIMAP / Centre de recherches sur les Ions, les Matériaux et la Photonique

+33 2 31 45 26 58

Thesis supervisor :

Magali MORALES

Université de Caen - CIMAP / Centre de recherches sur les Ions, les Matériaux et la Photonique

+33 2 31 45 26 58

Personal web page : http://cimap.ensicaen.fr/spip.php?article263

Laboratory link : http://cimap.ensicaen.fr/spip.php?rubrique99

The macroscopic behaviour of plant fiber reinforced polymers is strongly related to cellulose fibrillar reorganization during loading. This current assumption needs to be verified in case of flax fiber composite. The PhD student will first develops specific experimental procedures for in-situ (during tensile test) measurement of microfibrill orientation on isolated fiber, bundle of fibers, and flax composite micro-specimen. The relationships between the mechanic behavior of flax fibers at the microscopic scale and the mechanics of flax composites at the macroscopic scale will then be analyzed. The final objective of the research is to establish the mechanical micro-macro laws for plant fiber reinforced polymers. The expertise of CIMAP/PM2E team in digital image correlation, X-ray diffraction, and micro-specimen tensile test, will provide a precious input for the purpose.

Synthesis of aligned carbon nanotubes on metal at low temperature: growth development and study of mechanisms

SL-DRF-18-0826

Research field : Ultra-divided matter, Physical sciences for materials
Location :

Service Nanosciences et Innovation pour les Materiaux, la Biomédecine et l'Energie (NIMBE)

Laboratoire Edifices Nanométriques (LEDNA)

Saclay

Contact :

Emeline Charon

Martine Mayne

Starting date : 01-10-2018

Contact :

Emeline Charon

CEA - DRF/IRAMIS/NIMBE/LEDNA

0169089187

Thesis supervisor :

Martine Mayne

CEA - DRF/IRAMIS/NIMBE/LEDNA

01 69 08 48 47

Personal web page : http://iramis-i.cea.fr/Phocea/Membres/Annuaire/index.php?uid=echaron

Laboratory link : http://iramis.cea.fr/nimbe/ledna/

The CVD method (Chemical Vapour Deposition) using aerosols allows to obtain dense carpets of aligned carbon nanotubes (CNT) which applications are varied and promising. The objective of the thesis is to develop CNT synthesis at low temperature (= 650°C) according to two steps : (1) a parametric study according to the nature of carbon and catalytic precursors, and (2) a study of growth mechanisms by ex and in situ analyses.

The approach will consist of adjusting synthesis parameters (temperature, gaseous reactive atmosphere, nature of the carbon precursors or the substrate) in order to control CNT characteristics (alignment, length…). At low temperature, the decomposition of catalytic and carbonaceous precursors usually used is less effective. To solve this problem, the nature of the gaseous phase must be modified in terms of carbon precursor and carrier gas. Indeed, to limit the decrease of nanotube growth rate, it is necessary to use precursors with a more favorable catalytic and thermal decomposition around 600°C, as acetylene or ethylene or other carbon sources. Furthermore, we will perform in situ studies to characterize precisely the growth mechanisms of carbon nanotubes. A particular attention will be concerned by the control of diameter and density though electron microscopy analysis (SEM and TEM) and by the CNT structural quality analysis through Raman spectrometry and high-resolution transmission electron microscopy (HRTEM).

Curvature-induced charge separation in oxide semiconductor nanotubes: towards photocatalysis

SL-DRF-18-0439

Research field : Ultra-divided matter, Physical sciences for materials
Location :

Service Nanosciences et Innovation pour les Materiaux, la Biomédecine et l'Energie (NIMBE)

Laboratoire Interdisciplinaire sur l'Organisation Nanométrique et Supramoléculaire (LIONS)

Saclay

Contact :

Sophie LE CAER

Antoine THILL

Starting date : 01-10-2018

Contact :

Sophie LE CAER

CNRS - DRF/IRAMIS/NIMBE/LIONS

01 69 08 15 58

Thesis supervisor :

Antoine THILL

CEA - DSM/IRAMIS/NIMBE/LIONS

01 69 08 99 82

Personal web page : http://iramis.cea.fr/Pisp/antoine.thill/thill_fr.html

Laboratory link : http://iramis.cea.fr/nimbe/lions/

Imogolite are natural nanotubes having a well-defined very high curvature. It is possible to produce large quantities of synthetic version of this nanomaterial thanks to the PRODIGE pilot at NIMBE. It has been recently predicted by DFT calculation that the strong curvature of the imogolite wall induces a surface density of dipole at the imogolite wall. Such radially symmetric polarization is in favour of electron/hole charge separation during photo-induced events.

In this PhD project, we propose to investigate the existence of such polarization and quantify its magnitude. Different complementary experimental strategies are proposed to reach this goal for both native and hybrid imogolite nanotubes. Iron doping of the tubes will also be tested to modulate the band gap of the nanotubes.

Intermediate amorphous states during precipitation of cerium oxalate: towards a new nucleation model

SL-DRF-18-0111

Research field : Ultra-divided matter, Physical sciences for materials
Location :

Service Nanosciences et Innovation pour les Materiaux, la Biomédecine et l'Energie (NIMBE)

Laboratoire Interdisciplinaire sur l'Organisation Nanométrique et Supramoléculaire (LIONS)

Saclay

Contact :

Sophie CHARTON

David CARRIÈRE

Starting date : 01-11-2018

Contact :

Sophie CHARTON

CEA - DEN/DMRC

+33 (0)4.66.79.62.29

Thesis supervisor :

David CARRIÈRE

CEA - DSM/IRAMIS/NIMBE

0169085489

Personal web page : http://iramis.cea.fr/Pisp/68/david.carriere.html

Laboratory link : http://iramis.cea.fr/nimbe/lions/index.php

The formation of crystals by liquid reaction takes place in the many natural and artificial processes, and in particular in reactive crystallization processes. The control of the kinetics of the formation, the size and the morphology of the precipitates is still very challenging. Size control of precipitated powder is also an important issue of nuclear fuel treatment, where plutonium is precipitated as oxalate, before being converted into the oxide used in the manufacture of MOX.

The reference theory for predicting rate of crystal formation, used in process modeling, is the classical theory of nucleation (CNT), which is based on the thermodynamic description of the liquid-vapor equilibrium proposed by Gibbs in 1876. But this model sometimes dramatically fails because it ignores all the disordered intermediate states possibly achieved between the initial solution and the final crystal: clusters, liquid-liquid phase separations, amorphous particles or networks, etc. In particular, such amorphous intermediate states were observed in the precipitation of cerium oxalate, one of the reference simulating systems for plutonium, suggesting a two-stage nucleation process in contradiction with the CNT.

The general objective of this thesis is to characterize the intermediate states of the nucleation of cerium oxalate and their impact on the predictions of classical theory. As a close collaboration between CEA Marcoule and CEA Saclay, this thesis will combine techniques known to be able to tackle this difficult problem: X-ray scattering in laboratory and synchrotron facilities (SAXS/WAXS), microfluidics, thermodynamic and kinetic models.

Bio-inspired synthetic crystals

SL-DRF-18-0435

Research field : Ultra-divided matter, Physical sciences for materials
Location :

Service Nanosciences et Innovation pour les Materiaux, la Biomédecine et l'Energie (NIMBE)

Laboratoire Interdisciplinaire sur l'Organisation Nanométrique et Supramoléculaire (LIONS)

Saclay

Contact :

Corinne CHEVALLARD

Starting date : 01-11-2018

Contact :

Corinne CHEVALLARD

CEA - DRF/IRAMIS/NIMBE/LIONS

01-69-08-52-23

Thesis supervisor :

Corinne CHEVALLARD

CEA - DRF/IRAMIS/NIMBE/LIONS

01-69-08-52-23

Personal web page : http://iramis.cea.fr/Pisp/corinne.chevallard/

Laboratory link : http://iramis.cea.fr/nimbe/lions/index.php

More : http://www.fresnel.fr/spip/spip.php?article1099

Calcifying organisms (molluscs, corals, sponges) are able to produce crystallized mineral structures (shells, exoskeletons) with perfectly controlled morphology to target a particular biological function (protection, flotation, etc.). The physicochemical processes associated with this limestone biocrystallization are still poorly known. An ongoing hypothesis is that a liquid precursor could initially be formed during a liquid-liquid phase separation and then solidify as amorphous granules. These granules of size 50-500 nm would aggregate and crystallize to give the known biomineral structures, with their granularity and crystalline order at the micrometric range. In order to test such a hypothesis, the PhD student will perform calcium carbonate syntheses under biomimetic conditions, using either synthetic or biological organic additives. A detailed structural study will be performed to compare these synthetic crystals with their biogenic counterparts. The work will ultimately allow us to formulate a model of calcareous biocrystallization. It will be conducted in collaboration with the Fresnel Institute (V. Chamard, co-supervisor of this PhD thesis), and is part of a European project associating the IFREMER laboratory of French Polynesia.

Identification and characterization metrology of nanoparticles in complex systems

SL-DRF-18-0858

Research field : Ultra-divided matter, Physical sciences for materials
Location :

Service Nanosciences et Innovation pour les Materiaux, la Biomédecine et l'Energie (NIMBE)

Laboratoire Interdisciplinaire sur l'Organisation Nanométrique et Supramoléculaire (LIONS)

Saclay

Contact :

Valérie GEERTSEN

Fabienne TESTARD

Starting date : 01-09-2018

Contact :

Valérie GEERTSEN

CEA - DRF/IRAMIS/NIMBE/LIONS

0169084798

Thesis supervisor :

Fabienne TESTARD

CEA - DRF/IRAMIS/NIMBE/LIONS

Personal web page : http://iramis.cea.fr/Pisp/fabienne.testard/

Laboratory link : http://iramis.cea.fr/nimbe/lions/

The statutory requirements (obligation of labeling nano ingredient in foodstuffs, cosmetic or biocides) impose on the users of "classic" additives to know if these compounds contain nanomaterials or not. With the increasing exposure to nanomaterials within the life cycle of products, it is crucial to understand their impact on the health and on the environment and thus to have reliable measures for the risk assessment.



The classical analytical methods used for molecular compounds or colloids cannot be directly transposed for nanoparticles analysis. Today, it is thus necessary to develop standard methods for characterizations of nano-objects and the associated standards. The proposed phD is in this framework of nanometrology. The objective is to estimate the performance of the existing characterization methods of nanoparticles (SAXS, DLS, DRX, MEB and AFM) and to quantify their capacity, their limits, their tolerance and their uncertainties to measure the size and shape distributions, their concentration and the roughness of surfaces. The accent will focus on the evaluation on the measurements of the influence of the environment, the size and the form of particles, as well as their cristallinity or nature of defects.



The aim is attain a new achievement with metrology for the evaluation and the characterization of nanomaterials and to estimate performance levels associated to this combination of techniques for direct measurement in complex systems. On the longer term, the coupling of these methods can be of use to the industry to make of "safer by design".

 

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