Scientific direction Development of key enabling technologies
Transfer of knowledge to industry

PhD : selection by topics

Definition and validation of an innovative powder metallurgy process for high performance materials

Département Thermique Biomasse et Hydrogène (LITEN)

Laboratoire Conception et Assemblages

01-10-2018

SL-DRT-18-0682

emmanuel.rigal@cea.fr

This PhD project deals with the study, modeling and simulation of a key stage of Hot Isostatic Pressing, a fabrication process that involves the densification of gas atomised metallic powders. This stage, namely outgassing, allows to decrease the oxygen content of the material. As a result its mechanical properties improve and reach, or even exceed, those of the equivalent forged material. Yet, the process has other advantages: it is material efficient, it provides homogeneous and isotropic materials with a good ability to non destructive evaluation. So, a control of the outgassing step will contribute to a better acceptance of the process in industries which use components manufactured according to rules and standards, such like nuclear components or pressure vessels. The main items of the project will be: a study of the initial powder (made of a X2CrNiMo17-12-2(N2) steel), a study of its outgassing behavior using thermogravimetric analysis coupled with mass spectrometry and thermodynamics modelling, the definition of a model describing the gaseous flow in the porous material under anisotherm conditions and taking into account the gas sources and sinks, an experimental validation and a study of the properties of the achieved materials. The study will be hosted by a laboratory of CEA Liten which is well recognized in the field of HIP since many years. It will benefit from recent studies on this topic as well as from a favorable environment in terms of characterisation means.

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Bipolar lead-acid batteries with laminated current collectors

Département des Technologies Solaires (LITEN)

Laboratoire Stockage Electrique

01-10-2018

SL-DRT-18-0684

nicolas.guillet@cea.fr

New batteries with bipolar architecture: The thesis project aims the development of high-power / high-energy density / long-life / low cost lead acid batteries with bipolar architecture of the battery module innovative current collector materials and 3D printed components. The bipolar construction of the battery allows enhanced operation at high rates of charge and discharge typical for the energy storage systems used in some smart-grid and hybrid electric vehicle applications. One part of the thesis is focused on the optimisation of thin laminated composite structures composed of titanium and lead foils and their encapsulation in 3D printed plastic structures intended to use as bipolar current collectors. The latter will be used to develop and test lab-scale bipolar lead-acid batteries with optimized compositions and ratios of the positive and the negative active materials. The prototype batteries will be studied at different stages of their ageing using a variety of methods for physical, physico-chemical and electrochemical characterisation in order to estimate the potential failure mores and how to avoid them.

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Phase-Change Memory for high density Storage Class Memory applications

Département Composants Silicium (LETI)

Laboratoire de Composants Mémoires

01-10-2018

SL-DRT-18-0691

gabriele.navarro@cea.fr

Nowadays, the need of a data storage infrastructure allowing Big Data processing requires memory devices with improved performance. The objective of this PhD is the development of innovative Phase-Change Memory (PCM) devices to target Storage Class Memory applications (SCM) that require higher programming speed and endurance. To achieve this goal, the phase change material engineering becomes fundamental, in particular exploring new alloys capable of higher crystallization speed and higher stability. The candidate will contribute to the following tasks: development and electrical characterization of PCMs based on innovative materials, also co integrated with new BackEnd selectors developed in LETI, from single device analysis to full matrix statistics; physico-chemical characterization of the different alloys by resistivity measurements, XRD, FTIR, TEM etc.; multi-physical simulations to correlate the device performances with the material properties. In addition, the student will contribute to industrial projects, and will interact with experts at the international level in the field of the phase change materials.

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New wake up radio for an energy efficient integration of interacting IoTs in Cyber-Physical Systems

Département Systèmes

Laboratoire Communication des Objets Intelligents

01-09-2018

SL-DRT-18-0693

mickael.maman@cea.fr

With the massive deployment of sensor network applications, long lifetime networks are mandatory and very challenging. To optimize the network lifetime, it is crucial to design ultra-low power communication systems. Several technologies are competing for low power uplink communications (e.g., LoRa, Sigfox, Bluetooth LE, Thread, Zigbee, WiFi). But when interaction with IoT devices is mandatory (e.g., command in Cyber Physical System, interaction with the real environment in Augmented Reality), ultra-low power as well as predictable latency Downlink communications are missing. A lot of efforts were devoted to the design of energy efficient communication protocols, and especially MAC protocols. MACs have a critical role in the energy efficiency of communications as they control the transceiver. The aim of MAC protocols is to allow point-to-point communication between two neighboring nodes. Some technologies (e.g., LoRa, SigFox) proposes to open a window for Downlink communications after each Uplink communication in case of traffic. This approach does not work for latency constraint applications since a Downlink command could be process only after an Uplink communication. Other MAC solutions propose to periodically listen to Another approach is the use of ultra-low power wake-up receivers (WRX) which can significantly reduce the overall power consumption of the system. In this approach, the device can continuously listen to a wake up signal in the channel. The drawbacks of these solutions are their low maturity (proof of concept) and their very low sensitivity. During this PhD, we propose a cross-layer approach (RF/PHY/MAC). Our goal is to make a tradeoff between the energy consumption, the latency and the performance (e.g., range of communication).

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Spectral unmixing and classification in X-ray hyperspectral imaging

Département Microtechnologies pour la Biologie et la Santé (LETI)

Laboratoire Détecteurs

01-10-2018

SL-DRT-18-0731

caroline.paulus@cea.fr

As part of its X-ray (RX) imaging developments, LETI is studying the contribution of new CdTe-based hyperspectral RX detectors combined with advanced processing methods. The main applications are medical imaging, scientific instrumentation and control for security. The laboratory works in particular on X-ray detection systems of illicit substances such as explosive materials in air transport. Current data processing methods for discriminating materials or tissues analyzed from measurements are derived from techniques used with dual energy detectors. The aim of the thesis is to design advanced unmixing and classification algorithms taking into account all the spectral information provided by the detectors to improve the performances of the systems in terms of false alarm rate and good detection rate. The challenge is to demonstrate that these detectors and their associated data processing make it possible to achieve performances specified by equipment certification authorities. The proposed methods might be inspired by spectral unmixing and classification techniques widely developed in the context of hyperspectral imaging for Earth observation. The candidate must be specialized in signal processing and show interest in physics and instrumentation.

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Raman microspectroscopy coupled to isotopic labelling for the monitoring of antibiotic stress on single bacterial cells

Département Microtechnologies pour la Biologie et la Santé (LETI)

Laboratoire Imagerie et Systèmes d'Acquisition

01-10-2018

SL-DRT-18-0738

veronique.rebuffel@cea.fr

The antibiogram (antibiotic sensitivity test) test is in the heart of the rationalization of the antibiotic therapies. Faster novel antibiogram methods (answer in less than 2:00) will have a decisive impact in the fight against the extension of the multiresistances of pathogenic bacteria. The current methods, based on the capacity of a molecule to inhibit or not the growth of pathogens, cannot satisfy these speed requirements, because of latency time preliminary to any culture. The Raman microspectroscopy makes it possible to meet this need, with an approach authorizing the characterization of single cells. A time consuming culture, preliminary to the test itself, would not be thus necessary any more. Moreover, the sensitivity to antibiotic would be determined by evaluation of metabolism decrease, a criterion of sensitivity much earlier than growth inhibition. The objective of the thesis is to explore a new method of isotopic marking to measure, thanks to the Raman microspectroscopy, metabolism variations at the level of the single bacterium. Work will implement existing optical devices, as well as techniques of clinical microbiology. Algorithmic developments will concern both spectra and multivariate analysis, and modelling. The candidate must be titular of a diploma of engineer and/or Master degree in signal or data processing, eventually instrumentation, with knowledges in biophysics or optics. Strong interest for microbiology is required.

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