Θέματα Διπλωματικών Εργασιών Προπτυχιακών Φοιτητών του Τμήματος Χημικών Μηχανικών

Η διπλωματική είναι σε συνεπίβλεψη με τον καθ. Α. Νένε του EPFL.

ΕΠΙΒΛΕΠΩΝ : ΕΙΡΗΝΗ ΓΟΥΔΕΛΗ, Αναπλ. Καθ. Χημ. Μηχ. Παν/μιο Πατρών (πληροφορίες: eirini.goudeli@unimelb.edu.au)

The high reaction temperatures (>3000 K) accessible in aerosol synthesis routes, such as flame spray pyrolysis, allow for rapid nucleation and nanoparticle growth, while downstream in the aerosol reactor rapid quenching (cooling rates of >10⁴ K/s) takes place. This delicate control of high-temperature particle residence time in the flame allows capturing non-equilibrium nanostructures that are not in their lowest energy state but are stable under specific conditions, kinetically trapping them upon rapid cooling. This has led to the successful manufacture of high entropy materials (HEMs), metastable structures [1] and, nanomaterials with engineered defects containing more than 20 components [2].

Recently, FSP has been used to engineer an array of thermodynamically unstable nanomaterials, such as photocatalysts for pollutant removal [3], and molecular sensing of volatile organic compounds [1], circumventing the thermodynamic immiscibility limitations of solids. Thus, fundamental understanding of the thermodynamics and kinetics of defects and phase transitions during flame aerosol synthesis is at the heart of modern material design and innovation. 

Coalescence is dominant at high temperatures of the flame, while sintering (partial coalescence) may still take place even at low temperatures further downstream in the flame, especially for small (sub-5 nm) nanoparticles (e.g., see Fig. 2) [4] that exhibit melting points far below the bulk one [5]. Coalescence and sintering can alter the configurational order of HEMs by providing diffusion pathways that allow partial or full reorganization, potentially leading towards ordering, segregation or phase separation. Thus, the system can depart from high-entropy configurations even if the composition remains multicomponent. In this project, the effect of coalescence on short-range order would be elucidated as a function of the nanoparticle size, initial crystalline state, and process temperature, following the approach of Goudeli and Pratsinis [6]. Easy-to-use expressions for the HEMs coalescence rate will be proposed as a function of flame process parameters that can be readily used in particle dynamics models for process design.

ΕΠΙΒΛΕΠΩΝ : ΕΙΡΗΝΗ ΓΟΥΔΕΛΗ, Αναπλ. Καθ. Χημ. Μηχ. Παν/μιο Πατρών (πληροφορίες: eirini.goudeli@unimelb.edu.au)

Non-equilibrium nanomaterials are rapidly emerging owing to their unparalleled catalytic, electrochemical and sensing properties. By accessing compositions and crystal phases unattainable under equilibrium conditions, they can unlock potential for advanced materials in catalysis, healthcare, and energy applications, outperforming conventional equilibrium materials. These otherwise unattainable non-equilibrium nanostructures can be captured in flame synthesis methods those by kinetically “trapping” them upon rapid heating-cooling. Little is known, however, about the role of operating conditions and reactor design on crystal phase formation and compositional homogeneity. 

This project atomistic-level simulations would be used to explore how multi-metallic high entropy materials (HEMs) with well-controlled nanostructured characteristics form in flames. Amorphous multicomponent nanoparticles would be generated upon extreme heating to mimic nanoparticle formation at the high temperature region of the flame. A Fe/Co/Ni/Mo/Cu composition would be used as a model HEM, upon validation of available interatomic potentials [1]. 

The crystallization of these nanoparticles would be simulated by molecular dynamics (MD) simulations upon cooling at different target temperatures. The effect of temperature history on the kinetic trapping of high entropy alloys would be explored by XRD calculations of the MD-obtained atomic trajectories, Steinhardt parameters [2], and disorder variable [3] analysis to quantify the local crystalline structure. Distinct crystallization pathways that may occur depending on the cooling rate will be investigated, as demonstrated by such simulations for Au (Fig. 1) [4].

The role of process conditions on atomic mixing would also be explored, identifying conditions that lead to good atomic-scale mixing versus segregation, for a range of atomic compositions. The short-range order and potential non-random local bonding would be described by radial distribution function calculations and bond length distribution analysis. These metrics would be also used to determine metal-oxygen bond lengths within high-entropy oxide nanoparticles, aiming to reveal the mechanism by which oxygen vacancies affect the nanostructure. This project will contribute to the rational design of truly new non-equilibrium nanostructured materials by advancing the knowledge base of their formation by a proven scalable synthesis technology. A systematic investigation of process conditions affecting structural, compositional, and physical properties of HEMs will establish structure-property relationships, essential for process scale-up and industrial exploitation.

ΕΠΙΒΛΕΠΩΝ : ΕΙΡΗΝΗ ΓΟΥΔΕΛΗ, Αναπλ. Καθ. Χημ. Μηχ. Παν/μιο Πατρών (πληροφορίες: eirini.goudeli@unimelb.edu.au)

The aviation sector is a major contributor to anthropogenic climate change and among the most difficult sectors to decarbonize as it requires high-energy-density liquid fuels, strict safety and operation requirements, and long travel distances of aircraft fleets. Sustainable aviation fuels (SAFs) offer a realistic pathway for sustainable emission reductions, while being compatible with existing engines and infrastructure. So, bio-derived and synthetic jet fuels are being developed through a range of routes, including lipid-based pathways, alcohol upgrading, biomass-derived intermediates, and power-to-liquid processes. Even though demonstration of feasibility of SAFs (yield, selectivity, and basic fuel properties) has been largely explored, a mechanistic understanding of the effect of molecular structure, reaction pathways, and catalyst on final fuel composition and quality is limited. In addition, owing to the lack of kinetic information (activation energies, reaction rate constants, structure-activity relationships), catalyst development and pathway selection remains empirical.

Reactive atomistic simulations (ReaxFF) allow tracking of atomic position and velocities while explicitly accounting for chemical reactions. Recently, the catalytic combustion of p-menthane, a bio-derived isoprenoid fuel, over Pd and Pt nanocatalysts (Fig. 3), revealing that Pd-rich catalysts may require alloying or engineering to mitigate coke deposition, while Pt catalysts promote efficient low-temperature oxidation [1].

In this project, literature review will focus on existing and emerging jet biofuel pathways, identifying reaction classes and catalysts. Following the approach of Wang et al. [1], the catalytic conversion of selected jet-fuel-range hydrocarbons will be explored by ReaxFF simulations, and the effect of process conditions (temperature, pressure) and catalyst type and characteristics on catalytic performance and reaction pathways will be elucidated for different SAFs and blending ratios. The developed framework will support rational catalyst selection and discovery of new sustainable jet-fuel components.

(Modelling of the self-pressurization in liquid hydrogen tanks).

Ενδεικτική δημοσίεση: https://doi.org/10.1016/j.ijhydene.2026.154071

(Anomaly/Fault detection using AI/ML and deep Neural Networks) 

Ενδεικτική δημοσίεση: https://doi.org/10.1021/acs.iecr.4c04042  

(Thermochemical Properties Prediction using Artificial Inteligence/Machine Learning) 

Ενδεικτική δημοσίεση: http://dx.doi.org/10.1021/acs.jpca.9b04771

(Modelling of Smart Grids for Electricity Production from Renewable Enegy)

Ενδεικτική δημοσίεση: https://doi.org/10.1016/j.ijhydene.2024.07.117