IRMA seeks to develop efficient and non-invasive strategies for manipulating the morphology and the opto-electronic properties of vapor-deposited Ag nanostructures grown by magnetron sputtering at room temperature (i.e., 3D islands and ultrathin continuous layers). This will be achieved via selective deployment of additives (i.e., gaseous species and solute metals), either at the growth front (acting like surfactants) or using a seed layer, to improve wetting of Ag layers with the ultimate goal to produce conductive layers at sufficiently low thickness to ensure optical transparency. In order to capture the structural, morphological, and chemical evolutions at the nano- and atomic-scales while the materials are ‘alive’, IRMA proposes a novel and challenging experimental approach combining: - A detailed, real-time lab-based study providing simultaneous information on the optical, electrical, and stress evolution during growth and establishing a knowledge base for the impact of different surfactant approaches on the growth of ultrathin Ag films (work package 1). - An in situ ultra-high vacuum surface-characterization study providing complementary information about chemical state and local morphology of the as-grown films (work package 2). - A synchrotron-based study giving real-time information about the growth dynamics, structure evolution, and stress development, through X-ray diffraction, X-ray reflectivity and grazing incidence small-angle X-ray scattering combined with wafer curvature measurements (work package 3). - The determination of optical and electrical properties in situ and ex situ, including ageing effects on the structural and functional properties (work package 4). More specifically, different sputter-deposited Ag layers will be critically examined and benchmarked against reference Ag films grown in pure argon on silicon oxide surfaces: 1) the use of gas additives by performing Ag growth in argon/nitrogen plasma discharge, and 2) the growth of Ag on amorphous Ge seed layers, as these two approaches are the most efficient in promoting metal wetting, according to the literature. Additionally, we will explore the intelligent deployment of these surfactants, such as the use of Ag(1-x)-Ge(x) seed layers grown by co-deposition or the addition of nitrogen at specific nanostructure-formation key stages. Three main research objectives are foreseen: - To gain fundamental understanding on the impact of additives on the early-growth stages of Ag ultrathin films, in terms of interface chemistry, growth morphology, crystal structure, stress development, and surface roughness. - To study relaxation processes after short-time growth interruptions as well as long-term and thermal stability of the investigated systems. - To propose guidelines for efficient design strategies with the aim of achieving ultrathin metal layers with optimal optical transmittance, electrical conductivity, and improved durability for use as transparent conductive electrodes. The IRMA project leverages on the complementary expertise and existing collaboration of three academic partners, Pprime Institute and SOLEIL in France, and Karlsruhe Institute of Technology in Germany, which offer unique research facilities to reach these objectives. On a grander scale, the fundamental knowledge generated by the IRMA project paves the way toward intelligent in-line control of industrial nanostructure synthesis processes.

Electrification of vehicles and improved efficiency of internal combustion engines (ICE) are the main levers to reduce greenhouse gas emissions. Recent studies indicate that in 2040 thermal cars sales will still remain an important part of the market and the spark-ignition engine (SIE) is seen as the most interesting ICE technology. However, technological challenges must be tackled before meeting real driving emissions expectation due to the diversification and complexity of hybrid applications. For flow aerodynamics, mixing and combustion down to the individual engine cycle, challenges are for example associated to robustness of concepts on a cycle basis, rapid variations of engine loads observed in hybrid technologies during transients, the occurrence of extreme cycles for a wider range of operating conditions. Numerical, experimental and analyzing tools have made significant progress in recent years for the analysis of spatial and temporal scales of the unsteady in-cylinder flows. Large-Eddy Simulation (LES) is an essential tool for the design of robust concepts. While LES has been validated against well-defined experiments, the prediction of internal turbulent dynamics and combustion during a cycle is affected by epistemic uncertainties. Therefore, progress is still needed to obtain optimal and robust design. The main objective of ALEKCIA is to develop game-changing tools for augmented prediction and analysis of turbulent reactive flows with a focus on real SIE operations to better capture time-resolved events and increase understanding and control of the origins of undesired behaviors. The key hypothesis is that future progress and success is tied to the synergistic, strong combination of experimental and numerical tools at every stage of the project, which will provide advancement in the analysis of physical scales and boundary conditions (BCs). The major scientific challenges addressed by ALEKCIA are to 1/ quantify and reduce uncertainties (UQ) due to model parameters and BCs, 2/ develop new Data Assimilation (DA) approaches for coupling LES with experimental measurements, 3/ develop new decomposition methods to analyse big data generated by LES and high-speed PIV, 4/ combine them with UQ and DA methods for detailed analysis of individual SIE cycles during steady operations and fast transients. We stress that this methodology could also be used more widely for industry and energy applications. To achieve its ambitious objectives, work in ALEKCIA is structured into one management task (T0) and three technical tasks (T1 to T3). We will address non-cyclic phenomena under transient and fired operations and develop novel analysis from the acquired experimental and LES databases of a SIE performed respectively at PRISME (T1) and IFPEN (T3) laboratories. The partners of the project will also collaborate on the development of crank-angle resolved spatio-temporal EMD decomposition (T1 and T3) for engine flows to obtain an unprecedented detailed understanding of the mechanisms involved in the generation of in-cylinder flow, turbulent dynamics and their impact on combustion. The development of UQ tools to quantify and reduce uncertainties in complex LES of SIE flows is also targeted (T3). Finally, the capabilities of DA methods to calibrate realistic BCs on-the-fly is investigated by PPRIME (T2 and T3). This task is particularly relevant when assimilating experimental data (in the form of BC and in-cylinder large-scale flow patterns from EMD) obtained in extreme cycles. EMD obtained from a selected number of measured cycles presenting very slow or fast combustion rates will be coupled with UQ and DA tools for their inclusion in LES (T3). In this scenario, LES will be able to properly follow the assimilated aerodynamic behaviour of these cycles while turbulent dynamic will be modelled. Finally, the application of the developed tools will allow to identify the main key parameters controlling internal aerodynamics.

Understanding detonation behaviours in non-uniform explosive mixtures is one of the oldest and most challenging problem on explosion dynamics. Variable initial states are commonly encountered in most situations of practical interest such as safety of goods and people, advanced aerospace propulsion and defence security. They can be accidental such as leaks of hydrogen from pipes, tanks or the inner envelopes of nuclear reactors, those of hydrocarbon gases, the clouds of combustible particles in silos or mines. They can also result from technological constraints, such as the non-uniform distributions of fuel, oxidizer and burned gases in chambers of rotating detonation engines (RDE). The safe distribution and use of hydrogen combined with more thermally efficient propulsion modes are one of the thematic sets favoured by the scientific community to contain global warming. Obviously enough, anticipating all configurations of non-uniform explosive distributions is basically impossible. Rather, this project addresses four generic configurations designed as representative limits of a large range of real-life situations that consider one-phase gaseous or two-phase gas-liquid fluids. - Initial layers of composition normal to the direction of the detonation propagation. The configuration retained in this work is the succession of vertical layers of inert and premixed reactive gases normal to the propagation direction of the detonation. This is an idealization of jet-injection technologies (i) in RDE chambers when the jets are parallel to the exhaust, since the detonation rotates azimuthally, and (ii) for the mitigation of deflagrations or detonations that accidentally propagate in reactive gases. This work will address this configuration with either jets of an inert gas in a premixed reactive composition or jets of premixed reactive gas in an inert gas (subtask 3.2). - Initial layers of composition parallel to the direction of the detonation propagation. The configuration retained in this work is two superimposed horizontal layers parallel to the propagation direction of the detonation, with reactive or inert, liquid or gaseous fluids. This is an idealization of the stratified layers that can be formed accidentally from slow leaks from tanks and pipes, or designed specifically to shape discontinuity waves. This work will address this configuration with two gaseous layers, one inert and the other premixed-reactive (subtask 3.1), an inert liquid layer below a premixed-reactive gaseous layer (subtask 4.1), and a liquid fuel layer below a premixed-reactive gaseous layer (subtask 4.2). This project thus aims at contributing to compressible reactive fluid dynamics with reliable and controlled experimental observations on several interface phenomena specific to high-pressure, high-velocity physics that include oblique and normal shock interactions, mixing, vaporization, and fragmentation. The importance of the latter phenomena is that they drive the physics of both the causes and the effects of deflagration and detonation existences in many configurations of practical interest. The results will also contribute help numerical simulations to get more realistic if not predictive.

It is well known that the earth’s atmosphere has a transparency window for electromagnetic waves between 8 and 13 µm. This transparency window coincides with thermal radiation wavelengths at typical ambient temperatures. Using this phenomenon, a body can be cooled just because its heat is radiated into cold outer space. It is the so-called passive radiative cooling. This mechanism is very interesting in the current context where we look for improve energy efficiency. This passive radiative cooling can, for example, be used in air-conditioning or to chill photovoltaic cells. The goal of this project is to design and optimize passive daytime radiative cooling systems based on nano/microstructured materials with specifics radiative properties. This project will be divided in three parts. A first part will concern the design and optimization of radiative coolers. Based on the expertise of the coordinator in the field of nano/micro structured systems thermal emission control and on the optimization numerical tools that he has developed, highly reflective systems for solar radiation and emitting only between 8 and 13 µm will be designed. The coordinator has already developed first numerical models based on systems coupling multilayer structures and surface gratings to obtain the desired radiative properties. The second part of this project will deal with the fabrication of the system. Based on the results obtained in the first part, samples will be fabricated. Firstly, the coordinator will rely on the technology available in his laboratory. P' Institute has indeed a research bench composed of a dual-beam FIB (focused ion beam) that can etch the surface grating. The coordinator plan also to use the DRIE technique (Deep Reactive Ion Etching) available at ESIEE Paris. He will also collaborate with the team PPNa "Physics and Properties of Nanostructures" of the P' Institute. This team has extensive experience in the development of nanostructured materials. Two techniques will be used: the thin films deposits will be first done by sputtering and then by evaporation The third part will concern the measurements of the radiative properties of the samples and the refractive index of each material composing the whole structure. To characterize the samples, the team TNR has an optical measurements bench using FTIR (Fourier Transform Infrared Spectroscopy). This experimental bench has already helped characterizing the selective thermal emitters that the coordinator has developed for thermophotovoltaics applications. The samples reflectivity spectra will be measured and compared with those obtained numerically. Spectral measurements can also be made at the LTEN (Nantes Thermal and Energy Laboratory). This team has recently acquired advanced equipment. This is an FTIR coupled to an IR microscope. To calculate the radiative properties of the system, each material is defined by its refractive index and at a first step, the coordinator will use the values available in the literature. However, the risk of having differences between these literature data and the actual properties of the synthesized thin layers is not negligible. Therefore, in order to carry out numerical simulations with input parameters closest to reality, measurements of refractive indexes over the entire range of wavelength under consideration will be systematically carried out. A great opportunity is the recent acquisition by the P' Institute of an IR spectroscopic ellipsometer. This experimental bench will be coupled with a visible ellipsometer. It is important to say that only two French laboratories have such an experimental bench. Through these three scientific work packages, the final objective is the realization of one or more prototype of passive radiative coolers with high efficiency.

This project deals with an important part of lubrication science, namely the mixed lubrication regime, where rough surfaces are not fully separated and both contacting asperities and areas separated by a lubricant film share the load between two solids. The aim is to understand, in the case of a compressible fluid, this very specific regime in which mechanical seals often have to operate. A dedicated experimental test rig will enable original experimental investigations to be performed to visualize the interface and understand how a pressurized gas percolates through the asperities. The results will be then used as entry to develop predictive models of gaseous mixed lubrication in order to increase the reliability and lifetime of mechanical seals.