PhD opportunities

Self-engineering in molecular solids, applications to planetary science and energy transport and storage

Thesis proposal

Area of expertiseEnergétique et génie des procédés
Doctoral SchoolISMME - Systems Engineering, Materials, Mechanics, Energy
SupervisorM. Paolo STRINGARI
Research unitEnergy and Processes
Starting dateOctober 1st 2021
Keywordsenergy transport and storage, planetary science, thermodynamics, crystallization, hydrogen, methane
AbstractContext
Molecular solids, or Van der Waals solids, form when Van der Waals forces prevail on the kinetic energy of the molecules, allowing these last to arrange themselves in organized structures (self-engineering), with interesting properties and applications. Molecular solids can be constituted by pure components, solid solutions (with partial or total miscibility) or co-crystals, depending on the characteristics of the molecules. Few studies attempt to connect the molecular structure to the type of solid phase formed and, as a consequence, its stability and equilibrium with fluid phases.
Despite the general knowledge on low temperature Van der Waals solids is still scarce, interesting progress has been produced for industrial applications (production of industrial and medical gasses, and energy transport and storage) and in planetary science.

Planetary science
Liquefied gases are common on planets, moons, and other celestial bodies of the outer Solar System, namely beyond the main asteroid belt roughly located between the orbits of Mars and Jupiter, also known as the Solar System’s Frost Line. In addition to that, the cryogenic temperature and low-pressure conditions of some of these celestial bodies lead not only to the liquefaction of gases but also to their solidification. Examples are the clouds of NH3 in the H2-rich atmosphere of Jupiter and Saturn and their internal structures partially composed by liquid and metallic H2 with some He, the presence of CH4 and C2H6 lakes and seas on the surface of Titan (the largest moon of Saturn and the 2nd largest natural satellite in the Solar System), the solid mixture of H2O, NH3 and CH4 characterizing the mantle of the ice giants Uranus and Neptune, and the heterogeneous mix of solid N2, CH4, CO, CO2 and C2H6 of the surfaces of Pluto (largest dwarf planet in the Kuiper belt) and Triton (the largest natural satellite of Neptune). The study of the phenomena occurring in these celestial bodies has recently lead to the discovery of a number of co-crystals, able to stabilize some molecules in the solid phase at temperatures higher than their triple point temperature. The unique properties of these co-crystals is at the origin of the development of a new research field, named cryomineralogy.

Energy transport and storage
The transition toward energy carriers made up of small molecules, such as methane and hydrogen, is a fundamental step in the fight against global warming. However, because these molecules are in a gaseous state at room conditions, their large-scale adoption is contingent not only on production from renewable resources, as in the case of biogas and green hydrogen, but also on increasing their energy density, allowing them to be transported and stored efficiently.
Liquefaction, occurring at cryogenic temperature, is the most promising process to increase the energy density. The knowledge of low temperature phase equilibria, including Van der Waals solids, is fundamental for the design of safe and energy efficient liquefaction processes. In addition, Van der Waals solids could have interesting properties for energy transport and storage.

Objectives
This thesis aims at creating a bridge between the knowledge on Van der Waals solids developed in planetary science and industrial applications, as cryogenic separation processes and energy transport and storage.
The main objective of the thesis is the study of the properties of a certain number of molecules of interest for energy transport and storage and planetary science in the low-to-cryogenic temperature region down to the boiling temperature of nitrogen. These properties include the thermodynamic and transport properties of these molecules and their mixtures in both liquid and solid states, and will be evaluated by means of experimental measurements and molecular simulation. With respect to the experimental work, existing apparatuses will be used for the characterization of phase equilibria (vapor-liquid, solid-liquid,…); in addition, the PhD candidate will be involved in the conception/design of an apparatus for the characterization of the Van der Waals solids in the low-temperature region.
The thesis is proposed by the Centre of Thermodynamics of Processes of MINES ParisTech, PSL University, and it inserts in the context of industrial projects in the energy field and international academic collaborations in the field of planetary science.

Approach - Methods
The thesis is mainly organized into four parts:
- the development of a database (from literature data) of low temperature thermodynamic and transport properties of a selected number of gases and heavier components of interest for energy transport and storage and planetary science.
- the realization of original measurements (thermodynamic and transport properties) with existing apparatuses for covering the lack of literature data for the systems that will be selected for the thesis.
- the development of a new apparatus for the determination of low-temperature properties of interest of fluids and/or solids.
- the modeling of thermophysical properties by means of molecular simulation.
ProfileResearched candidates are chemical/energy engineers, chemists, and physicists, with strong motivation for fundamental research applied to liquefaction and solidification processes. The student is expected to actively participate to the meetings with partners. Interest for the experimental activity and very good level of English is required.

The thesis will be carried out at the Centre of Thermodynamics of Processes (CTP) in Fontainebleau, France (http://www.ctp.mines-paristech.fr/About-us/). Applications must be sent by email to Dr. Paolo Stringari (paolo.stringari@mines-paristech.fr) attaching the following documents:

- CV
- Motivation letter
- Recommendation letters of two Referees
- Results of examinations
- Diploma
- Level of English (TOEIC, or others)
- Copy of passport
FundingConcours pour un contrat doctoral
PartnershipContrat doctoral