Sujet de thèse pour la rentrée 2020

Fundamental investigation of Zr(IV) solubility and surface processes in alkaline systems: a combined solubility, spectroscopic and theoretical study

For a multidisciplinary research project involving extensive work in chemistry laboratories, use of advanced spectroscopic methods, in combination with thermodynamic and theoretical model calculations, we are looking for a highly motivated

PhD Student
Fundamental investigation of Zr(IV) solubility and surface processes in alkaline systems: a combined solubility, spectroscopic and theoretical study.

Background of the project and expected tasks within this PhD
The concept of solubility equilibrium of solids (e.g. metal oxides) in water is an integral part of the thermodynamic assessment of the behavior of nuclear waste in geological formations. Zirconium is an element relevant to the safety assessment of radioactive waste disposal, since it is produced with high yield in fission of uranium and Zr metal is used as a fuel cladding in light water reactors. Zirconium dioxide (zirconia) exists as corrosion product on used nuclear fuel rods and it may be the solubility-controlling phase for the neutron-activated product, 93Zr (t1/2 = 1.53106 a). As other tetravalent metals (e.g. Tc, Re, U, Np, Pu, among others), saturated solutions of Zr(IV) precipitate as sparingly soluble nanoparticulate hydrous oxides. Although the transformation of these amorphous phases into ZrO2(cr) is thermodynamically favored, the process is kinetically hindered and strongly driven by surface reactivity. In this context, the overall goal of this PhD is the investigation of solubility phenomena from a fundamental perspective, looking at surface processes and energetics using a combined experimental and theoretical approach. The study will target the transition between amorphous to crystalline phases, which arises as key process in the solution chemistry of M(IV) (with M = Zr, Tc, An, …). Special efforts will be dedicated to evaluate the fundamental role of water / hydration, particle size and particle growth on solubility.
In the first part of this PhD performed at KIT, you will synthesize amorphous Zr(IV) hydroxide in the laboratory, and will thoroughly characterize the resulting material with a multi-method approach including X-ray diffraction, thermogravimetric analysis (TGDTA), synchrotron-based techniques (e.g. XAFS, HR-XANES), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), among other techniques. You will study the solubility of this solid phase in well-defined aqueous, alkaline solutions, and will evaluate the impact of the temperature on the solubility of the aged solid phases, using the concepts of established solution thermodynamics.
In the second part of this PhD performed at SUBATECH, you will investigate the solubility of crystalline ZrO2 under analogous conditions as in KIT, and will contribute to the improvement of specific analytical methods for the quantification of trace concentrations of Zr. Modern complementary experimental methods will be used for
the characterization of the solid phases, with special focus on surface-sensitive techniques. During the second part of your PhD, you will also become acquitted with theoretical calculations looking at attachment / detachment reactions, surface energetics and eventually molecular dynamics. This will provide a fundamental understanding of the processes taking place at the interface ZrO2-water, and thus the link between amorphous / disordered systems and crystalline phases.
This challenging PhD project will be partially developed at KIT (Karlsruhe, Germany, 1.5 years), partially at SUBATECH (Nantes, France, 1.5 years). During the research period in Nantes, regular stays at the Laboratoire de Chimie Théorique LCT, Université P. M. Curie in Paris will be scheduled under the supervision of Dr. Monica CalatayudAntonino.

Your profile
We are looking for a student with a master in Chemistry, Materials Science, Earth Sciences, or related fields, who has good verbal and written knowledge in English. Knowledge of French or German language is positive but not mandatory. A strong background in materials science or inorganic chemistry, good skills in design and operation of experimental set-ups are an advantage. Interest in theoretical methods is expected. If you are motivated researcher who likes to work in an excellent, international, interdisciplinary environment, then you are the person we are looking for.

We offer
Our institutions are based on an interdisciplinary, innovative and dynamic collaboration. You will profit from a systematic training on the job, in addition to personal development possibilities and our pronounced vocational training culture. If you wish to optimally combine work and family life or other personal interests, we are able to support you with our modern employment conditions and the on-site infrastructure, both at KIT and SUBATECH.

For further information please contact :
Prof. Horst Geckeis, phone +49 721 608 22231 (Cette adresse e-mail est protégée contre les robots spammeurs. Vous devez activer le JavaScript pour la visualiser.),
Dr. Tomo Suzuki-Muresan, phone +33 251 858 671 (Cette adresse e-mail est protégée contre les robots spammeurs. Vous devez activer le JavaScript pour la visualiser.) or
Prof. Bernd Grambow, phone +33 251 858 686 (Cette adresse e-mail est protégée contre les robots spammeurs. Vous devez activer le JavaScript pour la visualiser.).

Applications should be accompanied by a short CV and university certificates.

Please submit your application online (including addresses of referees) for the position as a PhD Student (index no. …………).

SUBATECH is a mixed research unit (UMR 6457), co-operated by IMT Atlantique, the National Institute of Nuclear Physics and Particle Physics (IN2P3) of National Scientific Research Centre (CNRS) and the University of Nantes. The core research activities at SUBATECH are centered on nuclear physics and nuclear chemistry, in their fundamental and applied aspects, as well as their experimental and theoretical incarnations. The activities of SUBATECH display three major topics: Universe and High Energy Universe, Nuclear and Environment, and Nuclear science and health. The radiochemistry group focuses on the chemistry of radionuclides in solution, their interaction at mineral/water interfaces, and radiation induced chemical reactions by radiolysis. The issues related to disposal of nuclear waste, radioecology issues,
nuclear decommissioning and the development of radionuclides for cancer therapy and diagnostics have a strong societal impact and thus are actively studied.
Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany, is one of the largest science and engineering research institutions in Europe. Its research and development program is embedded in the superordinate program structure of the Helmholtz Association of National Research Centers. The Institute for Nuclear Waste Disposal (INE) at KIT is strongly focusing on safety research for radioactive waste disposal by investigation of geochemical processes relevant for assessing long-term behavior of waste forms and (geo-)technical and natural barriers.
The LCT is a mixed research unit co-operated by under Sorbonne University (Faculty of Science and Engineering) and the National Institute of Chemistry (INC) of CNRS. The laboratory's fields of interest cover all the fundamental aspects and fields of application of theoretical chemistry: eg. catalysis, molecular toxicology, chemistry of extreme environments in the gas or condensed phase. Its competences range from theoretical or methodological innovation in DFT (Density Functional Theory), QMC (Quantum Monte Carlo) or QM/MM (force field development) approaches to numerical modelling and simulations of complex systems involving organic, inorganic or organometallic molecular chemistry, interface chemistry, astrochemistry, or biology. The "materials for energy and environment" group focuses on modelling technological materials using state of the art quantum chemical tools, to provide insight in their structural, energetic and electronic (reactivity) properties.