Optical sensor development for in-situ and operando Li-ion battery monitoring
To improve the battery management system, it is required to have a better knowledge of the physical and chemical phenomena inside the cells. The next generation of cells will integrate sensors for deepest monitoring of the cell to improve the performances, safety, reliability and lifetime of the battery packs. The main challenge is thus to measure relevant physico-chemical parameters in the heart of the cell to get a direct access to the real state of the cell and thus to optimize its management. To address this challenge, a research project will start at CEA at the beginning of 2020 to develop innovative optical sensors for Li-ion battery monitoring. He / She will participate, in a first step, to the development of optical probes and their integration on optical fibres. The work will focus on the synthesis of a photo-chemical probe (nanoparticle and/or molecule) as active part of the sensor. Then, theses probes will be put on the optical fibre surface to form the sensor. The candidate will also participate to the realization of an optical bench dedicated to the testing of the sensors. In a second step, he / she will work on integrating the sensors into the Li-ion cells and test them in different conditions. The objective is to demonstrate the proof of concept: validation of the sensors efficiency to capture the behaviour of the cell and correlate it to electrochemical measurements.
Modeling silicon-on-insulator quantum bit arrays
A post-doctoral position is open at the Interdisciplinary Research Institute of Grenoble (IRIG, formerly INAC) of the CEA Grenoble (France) on the theory and modeling of arrays of silicon-on-insulator quantum bits (SOI qubits). This position fits into an ERC Synergy project, quCube, aimed at developing two-dimensional arrays of such qubits. The selected candidate is expected to start between October and December 2019, for up to three years.
Many aspects of the physics of silicon qubits are still poorly understood, so that it is essential to support the experimental activity with state-of-the-art modeling. For that purpose, CEA is actively developing the “TB_Sim” code. TB_Sim relies on atomistic tight-binding and multi-bands k.p descriptions of the electronic structure of materials and includes, in particular, a time-dependent configuration interaction solver for the dynamics of interacting qubits.
The aims of this post-doctoral position are to improve our understanding of the physics of these devices and optimize their design, and, in particular,
- to model spin manipulation, readout, and coherence in one- and two-dimensional arrays of SOI qubits.
- to model exchange interactions in these arrays and assess the operation of multi-qubit gates.
The candidate will have the opportunity to interact with the experimental teams from CEA/IRIG, CEA/LETI and CNRS/Néel involved in quCube, and will have access to data on state-of-the-art devices.
Artificial Intelligence applied to Ion Beam Analysis
A one year contract postdoctoral research position is open at the laboratory for light element studies (LEEL, CEA/DRF) and the Data Science for Decision Laboratory (LS2D, DRT/LIST) and focuses on data processing based on AI and machine learning, here in the scope of Ion Beam Analysis (IBA).
In the context of this project, the successful candidate will have to fulfill the following tasks:
1- Design of a multispectral dictionary.
2- Learning module development.
3- Main code programming.
4- Development of a module dedicated to multispectral mappings.
5- Benchmarking.
The postdoctoral research associate will be hosted and supervised within LEEL and LS2D.
Strudy and processing of C/SiC composites
For different applications, we are looking for materials having superior mechanical properties at high temperature (1000 ° C or higher) and that are resistant to oxidation. The family of ceramic matrix composite materials (CMC), especially C / SiC, seems the most relevant to our needs. However, it is necessary to conduct studies to determine the most efficient solutions among the wide variety of fibrous architectures and possible matrix microstructures, while taking into account the constraints related to available processes and targeted geometries. This work will be conducted in collaboration with other CEA laboratories.
Leaching foams to extract metals from electronic waste
The subject is part of the ANR "Foamex" project covering TRL from 1 to 5 and focussing on the development of recycling of some metals from a shred of electronic cards, this recycling being carried out in a fluid foam (minimization of the volume of solvents) that can be considered at the first level as a dynamic chromatography column. The principle is to use the foam as a reservoir containing an acid solution and specific oxidizing agents to dissolve and extract metals in the form of ionic species, a phenomenon enhanced by friction between bubbles and simultaneously to concentrate them via the fluid and mobile liquid/air interfaces by flow.
Nanostructured negative electrodes for magnesium-ion batteries
The subject is part of an ANR project on the development of negative electrodes for magnesium (Mg)-ion batteries. Magnesium is an excellent alternative to lithium due to its high specific capacity, low cost, abundance on Earth and low reactivity. However, conventional electrolytes interact strongly with metallic magnesium to form a blocking layer on the surface of metallic Mg, inhibiting reversible electrochemical reactions. An interesting solution to overcome this problem is to replace the Mg metal electrode with a material compatible with electrolyte solutions having a large electrochemical stability window. Interestingly, Mg alloy compounds have adequate stability in conventional electrolytes, slightly higher potentials than pure metallic Mg with however lower specific capacities than Mg. As part of an ANR project, the LEEL laboratory develops new alloy compounds for Mg batteries in the form of nanostructured electrodes to overcome volume expansion and slow diffusion of ions during the alloying with Mg.
In this project, the postdoctoral associate will first be in charge of the fundamental understanding of the reactivity towards the electrolyte of the alloys developed in the laboratory, notably through impedance spectroscopy and XPS. Secondly, the postdoctoral associate will deal with the electrode and electrolyte formulation’s optimization with a systematic comparison of electrochemical performances in half-cell. Finally, full Mg-ion cells will be made with the better electrode/electrolyte combination.
Spectroscopy of AlN colored centers
The study of QD-like emission from deep emission centers in semiconductor has become an important topic in the general framework of quantum information processing and nanoscale sensing, the emblematic emission center being the N-V defect in diamonds. Recently, research has been conducted to evaluate the potential of other defects in various materials, for instance in GaN and BN. Oddly, not much is known on color centers in AlN, despite the many assets of this material : it can be epitaxially deposited, high quality bulk substrates are available, it can be processed as high quality factor microcavities.
We propose in this 12 months post-doc to explore the optical properties of deep luminescing centers in AlN. We will study by microphotoluminescence (either cw or time-resolved) various types of AlN : thin AlN grown on Si (possibly processed as membranes), thick AlN grown on sapphire, ensembles and single AlN nanowires.
Structural characterization, reactivity and physico-chemical properties of Pu(IV) colloidal suspensions
Pu(IV) is known to be highly prone to hydrolysis leading to the formation of extremely stable Pu(IV) colloidal suspensions (known as intrinsic colloids). The lack of knowledge concerning the speciation and reactivity of these Pu colloids hinders the development of reliable models allowing to predict their behavior in industrial and environmental systems. The behavior of these colloidal species towards dissolution, complexation, or aggregation has been very poorly described in the literature. It thus appears essential to study and characterize Pu(IV) colloids and in particular their surface charge properties which ensure their stability and their interactions with their environment. This pioneering project in the nuclear field aims to study and characterize colloidal Pu(IV) suspensions whose size, concentration and dispersion medium can be controlled by our approaches. It comprises: (i) the preparation of intrinsic Pu(IV) colloidal suspensions and the study of their chemical and sonochemical reactivity; (ii) the electrophoretic characterization of various colloidal suspensions and the study of their behavior under the influence of an electric field; (iii) the characterization of their multi-scale structural properties by small and large angle scattering (SAXS / WAXS) coupled with EXAFS / XANES measurements (MARS line, SOLEIL synchrotron).
Nano-silicon/graphene composites for high energy density lithium-ion batteries
This postdoctoral fellowship is part of the Graphene Flagship Core 2 H2020 european project (2018-2020) on the energy storage applications of graphene. In lithium-ion batteries, graphene associated to nanostructured silicon in a proper composite helps increase the energy capacity. Indeed graphene wraps silicon, reducing its reactivity with electrolyte and the formation of the SEI passivation layer. It also maintains a high electrical conductivity within the electrode.
The study will compare two technologies: graphene-silicon nanoparticles and graphene-silicon nanowires. The former composite, already explored in the above mentioned project, will be optimized in the present study. The latter is a new kind of composite, using a large scale silicon nanowire synthesis process recently patented in the lab. The postdoc will work within two laboratories: a technological research lab (LITEN) with expertise in batteries for transportation, and a fundamental research lab (INAC) with expertise in nanomaterial synthesis.
The postdoc will synthesize silicon nanowires for his/her composites at INAC. Following LITEN know-how, she/he will be in charge of composite formulation, battery fabrication and electrochemical cycling. He/she will systematically compare the electrochemical behavior of the nanoparticle and nanowire based silicon-graphene composites. Comparison will extend to the mechanism of capacity fading and SEI formation, thanks to the characterization means available at CEA Grenoble and in the European consortium: X-ray diffraction, electronic microscopy, XPS, FTIR, NMR spectroscopies. She/he will report her/his work within the international consortium (Cambride UK, Genova Italy, Graz Austria) meetings.
A 2-year post-doctoral position is open.
PhD in materials science is requested. Experience in nanocharacterization, nanochemistry and/or electrochemistry is welcome.
Applications are expected before May 31st, 2018.
Tunnel Junction for UV LEDs: characterization and optimization
Besides existing UV lamps, UV LEDs emitting in the UV-C region (around 265 nm) are considered as the next solutions for cost efficient water sterilization systems. But existing UV-C LEDs based on AlGaN wide band gap materials and related quantum well heterostructures still have low efficiencies which precludes their widespread use in industrial systems.
Analysing the reasons of the low efficiencies of present UV-C LEDs led us to propose a solution based on the use of a Tunnel Junction (TJ) inserted within the AlGaN heterostructure diode. p+/ n+ tunnel junctions are smart solutions to cope with doping related problems in the wide band gap AlGaN materials but give rise to extra tunneling resistances that need to be coped with. The post-doctoral work is dedicated to understanding the physics of tunneling processes in the TJ itself for a better control of the tunneling current.
The post-doctoral work will be carried out at the “Plate-Forme de Nanocaractérization” in CEA/ Grenoble, using different optical, structural and electrical measurements on stand-alone TJs or on TJs inserted within LEDs. The candidate will have to interact strongly with the team in CNRS/CRHEA in Sophia Antipolis where epitaxial growth of the diodes will be undertaken. The work is part of a collaborative project named "DUVET" financed by the Agence Nationale de la Recherche (ANR).