■ Internal field NMR for in-situ characterization of Cobalt metal nanostructures in energy materials

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Description of the PhD project

The main objective of this PhD project is to use magnetic interactions between metal particles to characterize Cobalt metal nanoparticles assemblies (size, shape, structure, interface and dispersion) in catalysts and battery materials.
Co metal nanoparticles and their composites find wide application in different technological spheres, from medicine to information storage, supercapacitors, battery materials and catalysis. To date there are no ways to measure Co nanoparticles size, shape, structure, interface and dispersion in situ. This impedes understanding and progress of critical technologies related to clean fuel (catalysis) and energy storage (batteries). It is thus decisive to find new ways to characterize Co metal nanoparticles assemblies under near operando conditions. To address this issue, our strategy is to correlate the Internal Field Nuclear Magnetic Resonance (IF NMR) spectra with the structure and dispersion features of Co metal assemblies.
Below a given temperature, nanoparticles of Cobalt are soft ferromagnets. This allows characterizing them by IF NMR (aka ferromagnetic NMR) in the absence of an applied field. The physics is however richer than for traditional NMR since the resonance does not depend solely on the molecular structure but also on magnetic interactions between particles. It thus reflects on the structures at the nanometer scale.

First, the proof-of-concept will be established on model systems, and then we will apply it to characterize catalytic nanoreactors and the conversion reaction occurring in battery materials.

This project presents several instrumental challenges. The main advantage of IF NMR is that it does not require a permanent magnet. The geometry of the probe is thus very open and can be adapted to the experiment without geometric constraint. Compared to a traditional NMR probe, it can be more easily fitted with vacuum and gas feed lines as well as temperature control, making this technique particularly suitable for the study of catalysts and battery materials. The main challenge in the project is the broadband nature of the signal which expands over several MHz due to fluctuations in the hyperfine and demagnetization fields. Furthermore, the radio frequency field is not directly responsible for the nuclear spin transitions but only drives the oscillations of the hyperfine internal field. This results in an enhancement of the effect of the radio-frequency field which depends on the geometry of the magnetic domains and is particularly strong within the domain walls. As a consequence, a quantitative analysis of the signal requires controlling precisely the intensity of the radiofrequency field in order to assess this enhancement effect over the whole frequency range. The SIMM laboratory’s experience in designing custom made probes and experimental setups for non-conventional NMR in open geometries makes it particularly well suited for finding a solution to these experimental issues.


Metal Support Interaction
Heterogeneous catalysis

Research unit

Soft Matter Sciences and Engineering

Description of the research Unit/subunit

The SIMM laboratory (UMR CNRS 7615) leans on its established competencies to clarify links between complex objects (which characteristic sizes are typically between ten microns and ten nanometers) and their macroscopic properties. We try to solve problems which originate in industrial questions, at the intersection of the traditional disciplines of physical-chemistry and chemical engineering. This approach can be illustrated by some of the recent studies developed in the lab : polymers at the interface, nano-rheology, photo-stimulable molecules or glass transition.
Industrial questions are both sources of inspiration and a motor. The complexity of the problems asks for a fundamental analysis of phenomena and the development of an engineering of macroscopic properties. From this point of view, we must keep at a high level, both the industrial and academic outcomes of our research. Typical field of implementations are reinforced elastomers, rheostimulables polymers, cements, adhesion or wetting.

Name of the supervisor
Jean-Baptiste d’Espinose de Lacaillerie

3i Aspects of the proposal

This project requires crossing borders between disciplines. It necessitates a good understanding of magnetism as well as of inorganic chemistry and electrochemistry. Expertise in each field will be mobilized at the best international level and the PhD candidate will have to perform experiments not only in Paris but also in Amiens and in Russia (Institute of Metal Physics and Boreskov Institute of Catalysis). Finally, the research program is designed with French industrial partners who are key players in the field of materials for energy such as TOTAL and the French Petroleum Institute. Interaction with industrial research groups will thus be required.

Expected Profile of the candidate

• Specialization
Physics or Physical Chemistry

• Knowledge
Solid-state nuclear magnetic resonance, solid-state physics and magnetism, colloid chemistry

• Soft skills
Ability to work with scientists of different disciplines (spectroscopy, solid-state physics, polymer chemistry, inorganic chemists) and cultures.
Desire to work at the crossroads of experimental physics, chemistry and instrumental developments.
Balanced interest for fundamental progress and industrial applications.

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