Jean-Philippe Harvey

Simulations of immiscible two-phase flows involving surface tension (ST) require a robust high-fidelity framework. State-of-the-art multi-phase models, such as the Conservative Level-Set (CLS) approach, use Eulerian representations of the fluids and their interface, and require reinitialization methods to ensure volume conservation and accurate ST force modeling. This work proposes a new geometric reinitialization strategy for CLS formulations as an alternative to the typical PDE-based reinitialization methods. Building on the geometric reinitialization developed in context of level-set frameworks, the proposed method is an extension to the CLS approach within an open-source finite element framework that allows for fully distributed and adaptively refined, two- and three-dimensional meshes. This extension enables application of the geometric reinitialization method to large-scale three-dimensional problems with strongly deforming interfaces, including breakup. The method is quantitatively compared to two established reinitialization approaches: the PDE-based reinitialization proposed in the original CLS method and a simple projection-based approach. The assessment comprises three 3D application cases of increasing complexity: the capillary migration of a droplet, the rise of a bubble, and the Rayleigh-Plateau instability development in a capillary jet. The geometric method leads to high-quality, spatially-converged results in good agreement with benchmark and reference solutions. It robustly and accurately recovers expected interface topology-based metrics (e.g., the volume, surface area and sphericity), and relevant flow quantities. In addition, the proposed method has only two parameters and is robust across parameter choices and cases.

Simulations of immiscible flows involving surface tension (ST) require a robust high-fidelity framework. State-of-the-art multi-phase models, such as the Conservative Level-Set (CLS) approach, rely on Eulerian representations of the fluids and interface and require reinitialization methods to ensure volume conservation and accurate ST force modeling. This work focuses on the complete description of a CLS solver and proposes a novel geometric reinitialization method, based on the level-set literature. It includes a quantitative and objective comparison of this new geometric method to two reinitialization approaches: the PDE-based reinitialization proposed in the original CLS method and a simple projection-based approach. This comparison tackles three 3D application cases: the rise of a bubble, the capillary migration of a droplet, and the Rayleigh-Plateau instability development in a capillary jet. The PDE-based and geometric methods lead to high-quality, spatially-converged results in good agreement with benchmark and analytic solutions, while the projection-based reinitialization fails to capture complex 3D interfacial dynamics. The results also highlight the robustness of the novel geometric method which offers a two-parameter framework in comparison to the PDE-based method that necessitates a case-dependent selection of four parameters.

This work investigates the mixed site occupancy of aluminium and silicon atoms in the β-AlFeSi phase. For this purpose, the six mixed Al/Si sites of the β-AlFeSi structure were considered independent and alternatively substituted by Al or Si, thus generating 64 ordered structures or end-members. The enthalpy of formation of each end-member was calculated by DFT. These calculations allowed us to derive the enthalpy of mixing of the solid solution at 0 K, over a wide range of chemical compositions, from the Al–Fe binary system to the Si–Fe binary system. In addition, the heat capacities of the solid solution were determined using a Debye model based on the calculation of the elastic constants and the equation of state of each end-member. These heat capacity values were used along with the enthalpy of formation we calculated to determine the Gibbs free energies of all the end-members of the β-AlFeSi structure. Finally, the configurational entropy of mixing from the Compound Energy Formalism (CEF) for the configurational entropy of mixing was subsequently used to calculate the occupation fractions of the Si sites on the Al sites of the β-AlFeSi structure, at 300 K and 938 K, the latter being the thermal decomposition temperature of this compound. These original site occupancy data were used to quantify the chemical ordering of the solid solution and to compare different sublattice (SL) models. We thus highlight that the SL model of the β-AlFeSi solution most commonly accepted in the literature generates considerable errors in its thermodynamic description, contrary to the model proposed in this paper, which is both simple and particularly accurate, consisting in merging the sites Al(1)–Al(6), the sites Al(2)–Al(3) as well as the sites Al(4)–Al(5).

Classical molecular dynamics simulations of metallic systems have been extensively applied in recent years for the exploration of the energetic behavior of mesoscale structures and for the generation of thermodynamic and physical properties. The evaluation of the conditions leading to the melting of pure metals and alloys is particularly challenging as it involves at one point the simultaneous presence of both a solid and a liquid phase. Defects such as vacancies, dislocation, grain boundaries and pores typically promote the melting of a solid by locally increasing its free energy which favors the destruction of long-range ordering at the origin of this phase transition. In real materials, many of these defects are microscopic and cannot yet be modelled via conventional atomistic simulations. Still, molecular dynamics-based methodologies are commonly used to estimate the melting temperature of solids. These methods involve the use of mesoscale supercells with various nanoscale defects. Moreover, the deterministic nature of classical MD simulations requires the adequate selection of the initial configuration to be melted. In this context, the main objective of this paper is to quantify the precision of the existing classical molecular dynamics computational methods used to evaluate the melting point of pure compounds as well as the solidus/liquidus lines of Al-based binary metallic systems. We also aim to improve the methodology of different approaches such as the void method, the interface method as well as the grain method to obtain a precise evaluation of the melting behavior of pure metals and alloys. We carefully analyzed the importance of the local chemical ordering on the melting behavior. The ins and outs of different numerical methods in predicting the melting temperature via MD are discussed through several examples related to pure metallic elements, congruently and non-congruently melting compounds as well as binary solid solutions. It is shown that the defect distribution of the initial supercell configuration plays an important role upon the description of the melting mechanism of solids leading to a poor predictive capability of melting temperature if not properly controlled. A new methodology based on defect distribution within the initial configuration is proposed to overcome these limitations.

Multi-component and multiphasic materials are continually being developed for electronics, aircraft, automotive, and general applications. Integrated Computational Materials Engineering (ICME) is a multiple-length scale approach that greatly benefits from atomistic scale simulations to explore new alloys. Molecular Dynamics (MD) allows to perform large-scale simulations by using classical interatomic potentials. The main challenge of using such a classical approach is the transferability of the interatomic potentials from one structure to another when one aims to study multi-component systems. In this work, the reliability of Zr, Al–Cu, Al–Cr and Al–Zr–Ti force field potentials is examined. It has been found that current interatomic potentials are not completely transferable due to the structure dependence from their parameterization. Besides that, they provide an appropriate description of unary and binary systems, notably for liquids, isotropic solids, and partially isotropic compounds. For solidification purposes, it has been found that coherent primary solidification of the FCC-phase in pure Al is highly dependent on the formalism to tune interatomic interactions. For Al–Cr alloys, the icosahedral short-range ordering (ISRO) increased by adding Cr to the melts. The different steps of solidification (formation of nuclei, effective germination of the α-Al phase and end of solidification) have been related to the evolution of the ISRO. The addition of Cr in melts prevented undercooling via icosahedral-enhanced nucleation of the α-Al phase. Precipitation of primary intermetallics in hyper-peritectic Al–Cr alloys was also tested. Contrary to classical thermodynamics predictions, α-Al phase was the primary precipitate for these alloys. This implies that Cr supersaturated the α-Al phase rather than forming intermetallic phases due to the high cooling rates.

Metals and alloys are among the most technologically important materials for our industrialized societies. They are the most common structural materials used in cars, airplanes and buildings, and constitute the technological core of most electronic devices. They allow the transportation of energy over great distances and are exploited in critical parts of renewable energy technologies. Even though primary metal production industries are mature and operate optimized pyrometallurgical processes, they extensively rely on cheap and abundant carbonaceous reactants (fossil fuels, coke), require high power heating units (which are also typically powered by fossil fuels) to calcine, roast, smelt and refine, and they generate many output streams with high residual energy content. Many unit operations also generate hazardous gaseous species on top of large CO₂ emissions which require gas-scrubbing and capture strategies for the future. Therefore, there are still many opportunities to lower the environmental footprint of key pyrometallurgical operations. This paper explores the possibility to use greener reactants such as bio-fuels, bio-char, hydrogen and ammonia in different pyrometallurgical units. It also identifies all recycled streams that are available (such as steel and aluminum scraps, electronic waste and Li-ion batteries) as well as the technological challenges associated with their integration in primary metal processes. A complete discussion about the alternatives to carbon-based reduction is constructed around the use of hydrogen, metallo-reduction as well as inert anode electrometallurgy. The review work is completed with an overview of the different approaches to use renewable energies and valorize residual heat in pyrometallurgical units. Finally, strategies to mitigate environmental impacts of pyrometallurgical operations such as CO₂ capture utilization and storage as well as gas scrubbing technologies are detailed. This original review paper brings together for the first time all potential strategies and efforts that could be deployed in the future to decrease the environmental footprint of the pyrometallurgical industry. It is primarily intended to favour collaborative work and establish synergies between academia, the pyrometallurgical industry, decision-makers and equipment providers. Graphical Highlights: A more sustainable production of metals using greener reactants, green electricity or carbon capture is possible and sometimes already underway. More investments and pressure are required to hasten change. Discussion: Is there enough pressure on the aluminum and steel industries to meet the set climate targets? The greenhouse gas emissions of existing facilities can often be partly mitigated by retrofitting them with green technologies, should we close plants prematurely to build new plants using greener technologies? Since green or renewable resources presently have limited availability, in which sector should we use them to maximize their benefits?

This paper presents investigations on the thermodynamic stability of the Al13Fe4 solid solution in the Al-Fe-Mn ternary system as well as its crystal chemistry characterisation. In order to carry out this study, the isobaric heat capacity of the solution was measured at high temperature using a high precision three-dimensional probe. The heat capacity of the Al13Fe4 binary compound measured in this study between 600 K and 1223 K is CP(T) = 23.97 + 8.18.10−2T − 7.63.105T2. This value is significantly different from other measurements in the literature and we show in this paper that our measurements are not only more accurate than those in the literature but also more thermodynamically consistent with all other measurements and calculations of the enthalpy of formation of this phase. Measurements of the enthalpy of formation of the solid solution were also performed by in − situ synthesis in a DSC. These new measurements were complemented by DFT calculations of the enthalpy of formation at 0 K of the solid solution. Our calculations and measurements show that the substitution of Fe by Mn is responsible for a large increase in the solid solution enthalpy of formation. These new experimental and calculated data were used to develop a thermodynamic model of the solution. Finally, we utilized our model to calculate the Fe sof of the solid solution structure over its entire chemical composition range (simulating the complete substitution of all Fe atoms with Mn) as a function of temperature. The chemical ordering of the solid solution was thus quantified, revealing its ideal nature near its melting temperature. These results allowed the development of a new SL-model for the solution, both simpler and more reliable than those used in the literature.

The crystal chemistry of the Al13(Fe,TM)4 (TM = Co, Cr, Ni, Pt) solid solutions has been investigated by combining new formation enthalpy measurements by differential scanning calorimetry (DSC), new density functional theory (DFT) calculations and thermodynamic modelling. The formation enthalpies of seven alloys of the Al13(Fe,Co)4 solid solution were measured by DSC at 920 K, allowing the determination of the mixing enthalpy of the solution. These measurements are presented here for the first time and highlight the ideal nature of this solid solution. In addition, the mixing enthalpy of the Al13(Fe,TM)4 solid solutions (TM = Co, Cr, Ni, Pt) was determined by DFT at 0 K. These new calculated and measured data (in the case of the Al13(Fe,Co)4 solid solution) were used to perform thermodynamic modelling of the solid solutions and better understand their thermodynamic stability. In addition, our modelling was used to calculate the TM occupancy on the Fe sites of the Al13(Fe,TM)4 solid solution structure at different temperatures. These new data were used to quantify the chemical ordering of the solid solutions as a function of temperature. While these solid solutions show significant chemical ordering at low temperatures, only the Al13(Fe,Pt)4 solution remains highly ordered at high temperatures. These new data are presented for the first time in this paper and have allowed us to design an optimal sublattice (SL) model for the Al13Fe4 solid solutions.

Electronic products contain a wide range of materials including pure metals and alloys, ceramics, and polymers. Disassembling each individual component of such products to recycle is impossible. For that reason, end‐of‐life electronic products like waste printed circuit boards (WPCB) are shredded and sent to pyrometallurgical processes to recover valuable metals. One major issue with recycling is the release of gaseous brominated species that need to be captured or stabilized. It is crucial to have a fundamental understanding of the chemical interactions that occur between each component of the WPCB in these processes. The thermal degradation mechanism of WPCB is investigated here using differential scanning calorimetry coupled to thermogravimetric analysis of both synthetic samples and shredded WPCB. Computational thermochemistry is used to support the identified reaction mechanisms which involve the release of gaseous hydrogen bromide evolving from Tetrabromobisphenol A used as a flame retardant. The chemical reactivity between this compound and each major WPCB component is quantified. It is proven that HBr(g) reacts with copper, iron, and CaO to form bromides which stay in the solid pyrolysis residue up to a temperature of 580 °C. Above this temperature, CuBr₂ and FeBr₂ start to evaporate and are lost in the gas phase.