Research Dirk Lamoen

Abstract

The development of innovative next-generation materials and technologies, by combining physics, chemistry and engineering methods, will help to increase the service life and durability of road pavements. The use of cold recycled foamed pavement base layer is drawing extensive attention due to its environmental and economic advantages. In addition, the use of fibres in warm mix foamed asphalt, showed potential to improve mechanical properties and adhesion behaviour. Despite these potential benefits of fibres in asphalt, there is limited experience and literature available on the bonding mechanism of the Fibre-Foamed Aggregate matrix (FIFA). This project aims to gain a deep understanding of the physicochemical bonding mechanism of FIFA mixtures, a new composite material with a unique visco-elastoplastic behaviour, caused by the complex interactions between the mixture constituents. Moreover, this project uses Molecular Dynamics simulations to fundamentally map the adhesion mechanism of FIFA interfaces on the one hand, and on the other hand, to explain the degradation of nanostructure by moisture action and the corresponding interface debonding. The surface free energy method will be used to acquire a reliable mechanistic approach for evaluating the moisture damage mechanism of FIFA mixtures. The results are expected to scientifically assist in the future selection of optimal material properties taking into account adhesion and moisture sensitivity.

Researcher(s)

• Promoter: Van den bergh Wim
• Co-promoter: Lamoen Dirk
• Fellow: Barisoglu Ecem Nur

Research team(s)

• Sustainable Pavements and Asphalt Research (SuPAR)

Project type(s)

• Research Project

Abstract

Platinum Group Metal (PGM) nanoparticles, more specifically platinum, rhodium, and palladium, are essential components in autocatalysts in the outlets of cars, since they work as active sites for catalytic reactions. Due to increasingly stringent environmental regulations, the demand for these metals increases yearly. Since PGMs are very scarce, efficient recycling of these metals has become an important issue. Currently, the smelting process is the most commonly employed pyrometallurgical approach for concentrating PGMs. The behavior of the PGM particles during the process cannot be observed directly in experiments, due to the scale of the industrial furnaces and the small size of the PGM nanoparticles. Computational modeling of this process can thus provide a very useful addition to fill this gap. This PhD aims to develop a modeling framework combining a multi-phase-field model with DFT calculations to study the local dissolution behavior of PGM nanoparticles from spent auto-catalysts in a metallurgical slag containing collector metal droplets. This framework will be used to uncover the dominant dissolution mechanism, leading to new insights into the effects of pyrometallurgical process parameters on the dissolution of these PGM particles, useful for interpreting observations from and optimizing industrial recovery operations. Once the framework is established, it could be applied to different recovery processes as well, increasing its relevance towards the industry.

Researcher(s)

• Promoter: Partoens Bart
• Co-promoter: Lamoen Dirk

Research team(s)

• Condensed Matter Theory

Project type(s)

• Research Project

Abstract

Titanium-dioxide-based materials (titania) are semiconductors with many versatile applications in chemical catalysis, electrochemical sensing, food industry, energy conversion and many more. A considerable part of these applications rely on the electron-hole formation in titania by the absorption of light in the UV range. However, this restricts many practical applications, since sunlight has a limited UV content. Coloured titania, such as grey and black titania, can be formed via thermal, chemical or sonochemical reduction pathways. Although these materials absorb light in the visible range, there is many conflicting data reported about their activity and involved mechanistic pathways. There is also no consensus on the optimal synthesis routes to enhance specific favorable material characteristics. The large heterogeneity in coloured titania materials and their syntheses used in literature hampers a clear correlation between synthesis, electronic structure and activity. In this concerted action, we aim at a controlled alteration of the reduction conditions of porous titania linked to a direct determination of a variety of properties, such as electron traps, surface-adsorbed and surface-reacted species, bulk defects, band gap, polymorphs and pore sizes, and to activity measurements. For the latter we will test their capacity for photocatalytic reduction of CO2 and their applicability as electrode material in the electrochemical sensing of phenolic compounds in water. With this approach we guarantee that the results of the different experiments can be directly compared and correlated. This will allow determining the key factors governing the relation between synthesis, electronic and geometric structure and activity of coloured titania. This knowledge will be translated in optimal synthesis conditions for the here proposed applications, of importance in sustainable chemistry and development. The project makes use of the unique complementary expertise in the synthesis, experimental and theoretical characterization and application of titanium-dioxide-based materials available at UAntwerp.

Researcher(s)

• Promoter: Van Doorslaer Sabine
• Co-promoter: De Wael Karolien
• Co-promoter: Lamoen Dirk
• Co-promoter: Meynen Vera
• Co-promoter: Verbruggen Sammy

Research team(s)

• Theory and Spectroscopy of Molecules and Materials (TSM²)
• Biophysics and Biomedical Physics

Project type(s)

• Research Project

Abstract

Individual point defects in diamond crystals belong to an important class of quantum systems denoted as solid-state qubits. Such point defects, as for example NV, SiV, are intensively studied in the field of quantum sensing and metrology but also quantum information science. The applicants recently developed a novel technique, photoelectrically detected spin resonances in diamond, which brings promises for a new category of quantum devices that can be coupled with classical semiconducting electronics. The photoelectric readout is fundamentally based on charge state transitions in single point defects. In this respect, the photoelectric method differs from optical detection in two level quantum systems. In our proposal we would like to use this basic property of photoelectric readout and realise a novel type of qubit - charge-state solid qubit - using the transition between the different charge state of the same defect. Combining with the spin manipulations a hybrid quantum systems can be conceived. The proposal is based on preliminary results demonstrating the SiV charge state readout. To devise the mechanism of charge state transitions we will use predictive ab initio calculations theoretical methodology, permitting to determine the energy position of charge state levels in the diamond gap, photoionisation cross section, rates and the electron transport coherence with respect to the driving field. We will demonstrate charge-qubit superposition and two qubit entanglement.

Researcher(s)

• Promoter: Lamoen Dirk
• Co-promoter: Partoens Bart

Research team(s)

• Electron microscopy for materials research (EMAT)

Project type(s)

• Research Project

Abstract

Computational modeling is an essential factor in the study of the properties of materials. Nowadays, computational modeling is extensively used to predict and develop new materials. This requires a thorough knowledge of the local atomic (structural and electronic) structure and its influence on the macroscopic properties. Although, in principle, all materials can be described with the laws of quantum mechanics, it is impossible in practice to derive all material properties from these. Even with today's most powerful supercomputers, quantum mechanical electronic structure calculations are limited to a thousand atoms and to a maximum of 1 ns. To study length and time scales that go beyond these atomic scales, (semi-) empirical techniques are used and further developed through multiscale modeling. Transitions between models describing at different time and length scales are achieved by studying the relevant scale with the appropriate computational techniques. In order to have a thorough understanding of materials properties it is therefore important for collaborations between computational groups with expertise on different methods to flourish.

Researcher(s)

• Promoter: Lamoen Dirk

Research team(s)

• Electron microscopy for materials research (EMAT)

Project type(s)

• Research Project

Abstract

Chiral features in metal nanoparticles (NP) result in chiroptical properties, of interest to many applications, such as enantioselective catalysis or separation, chiral sensing or drug delivery. These applications arise from the different interactions of chiral plasmonic NPs with left- and right-handed circularly polarized light (CPL). Therefore, much effort has been put into the development of NPs with complex structures and morphologies. The properties of such nanomaterials are usually characterized by measuring their circular dichroism (CD), which quantifies the interaction of an ensemble of particles with CPL. Multiple factors can be at the origin of the recorded CD signal, such as a helical morphology, chiral features in the crystalline structure, or the presence of chiral molecules at or near the surface of the chiral NPs. Unfortunately, there is no consensus on the relative importance of these different aspects. To obtain NPs with tailored chiroptical properties, it is thus important to understand the connection between the CD signal and the NP morphology. Transmission electron microscopy (TEM) is an excellent technique to investigate the structure of nanomaterials. Several approaches, within the field of expertise of EMAT, can be used to investigate the morphology, structure or properties of chiral nanoparticles. Examples include 3D structural characterization by scanning electron microscopy (SEM), electron tomography in real and reciprocal space and electron beam induced current measurements (SEEBIC). Moreover, there is still debate in the field on the application of electron energy loss spectroscopy (EELS) to measure chiral features of nanoparticles. Although these techniques are already being developed at EMAT in the framework of other projects, their combined application to chiral nanoparticles will require further development. For example, identification of chiral surface facets is currently impossible due to a lack of 3D resolution by electron tomography or SEEBIC. Visualisation of chiral molecules and micelles that lie at the origin of the growth of chiral nanoparticles is another challenge that will require the development of low-dose imaging techniques, ideally combined with in situ TEM to generate a relevant, liquid, environment. Moreover, quantification procedures, e.g. to define the degree of helicity will need to be developed. Such computational techniques, eventually based on the use of training a neural network as well as modeling of the connection between structure and properties are challenging aspects but the knowhow to help talented postdocs to overcome current limitations is available at EMAT.

Researcher(s)

• Promoter: Bals Sara
• Co-promoter: Lamoen Dirk
• Co-promoter: Verbeeck Johan
• Fellow: Mychinko Mikhail

Research team(s)

• Electron microscopy for materials research (EMAT)

Project type(s)

• Research Project

Abstract

In this project we provide an atomistic description by means of quantum mechanical density functional theory calculations of the defects that occur during the corrosion of UO2 to U3O8. In particular we investigate the properties of the intermediate oxide U3O7, which is the main precursor to the formation of U3O8. We investigate the influence of external factors like water and grain boundaries on the oxidation of UO2. The formation mechanisms of U3O8 are essential to understand the degradation of spent fuel under storage conditions.

Researcher(s)

• Promoter: Lamoen Dirk

Research team(s)

• Electron microscopy for materials research (EMAT)

Project type(s)

• Research Project

Abstract

The performance of Li-ion batteries is still far below the threshold for automotive and grid applications. This largely depends on the cathode. The commercially most developed cathode is LiCoO2, but there is a better alternative in LiNixMnxCo1-2xO2(NMC). However, even the best NMC still suffers poor electrode kinetics and large voltage decays on cycling, due to structural rearrangements upon charge-discharge. We propose to engineer the reversibility of the structural transformation also in NMC by coupling the TM cation migration with redox changes at the oxygen sublattice through dedicated TM cation replacement. We also propose to develop a Li-ion conducting coating to prevent contact between electrolyte and cathode to stop oxygen and cation loss and improve the capacity retention.

Researcher(s)

• Promoter: Hadermann Joke
• Co-promoter: Abakumov Artem
• Co-promoter: Lamoen Dirk

Research team(s)

• Electron microscopy for materials research (EMAT)

Project type(s)

• Research Project

Abstract

The objective of FONSENS is to develop breakthrough technologies in gas sensing that will provide higher sensitivity and superior selectivity at reduced cost and power consumption. This objective will be pursued by integrating complementary skills of EU and Russian groups. The main strategy in FONSENS for achieving enhanced sensor performances is to develop new nanostructured materials, which will allow control of concentration of active centers over a broad range for selective detection of toxic gases of different nature. The development of new generation of gas sensing materials will be supported by computational modeling with ab initio DFT calculations and a wide range of high resolution morphological and physico-chemical characterization techniques including (scanning) transmission electron microscopy and electron diffraction.

Researcher(s)

• Promoter: Lamoen Dirk
• Co-promoter: Abakumov Artem
• Co-promoter: Hadermann Joke

Research team(s)

• Electron microscopy for materials research (EMAT)

Project type(s)

• Research Project

Abstract

This project will quantify the concentration of cargo vapours around the ship's accommodation and investigate how to improve the situation. Wind tunnel experiments and CFD calculations will in addition to the existing on‐board measurements help to visualise the streamlines around the accommodation. Based on these results we will draw up guidelines to the crew on how to minimize cargo vapour concentrations around the superstructure in relation to the different cargo handling operations

Researcher(s)

• Promoter: Lamoen Dirk

Research team(s)

• Electron microscopy for materials research (EMAT)

Project website

Project type(s)

• Research Project

Abstract

The overall objective of the research proposal is to elucidate the chemical composition of the target surface under different experimental conditions, and using this chemical information to calculate the electron yield by first-principles techniques and the sputter yield by Monte Carlo techniques. In this way, the project combines experiments and calculations to obtain quantitative data about two fundamental processes during reactive magnetron sputtering.

Researcher(s)

• Promoter: Lamoen Dirk

Research team(s)

• Electron microscopy for materials research (EMAT)

Project type(s)

• Research Project

Abstract

Grain boundaries in polycrystalline materials are known to play a critical role in determining their electronic properties. For several reasons, polycrystalline materials are at the heart of many present day electronic devices. Thus, a thorough understanding of the physics of grain boundaries is of fundamental importance for the design of devices with increased efficiency. The problem is compounded by the fact that the typical presence of nonnegligible concentrations of impurities and defects leads to a phenomenology that can be very different from that occurring in the bulk. In this project we will consider as a case study the chalcopyrite CuIn1-xGaxSe2 (CIGS) systems, which are of great current interest. Indeed, although today photovoltaic cells are still largely built with Si-based absorber layers, the low absorption coefficient of Si has prompted research on cells based on thin-film absorber layers, with higher power-to-weight ratios.

Researcher(s)

• Promoter: Lamoen Dirk

Research team(s)

• Electron microscopy for materials research (EMAT)

Project type(s)

• Research Project

Abstract

This project represents a research contract awarded by the University of Antwerp. The supervisor provides the Antwerp University research mentioned in the title of the project under the conditions stipulated by the university.

Researcher(s)

• Promoter: Lamoen Dirk
• Fellow: Govaerts Kirsten

Research team(s)

• Electron microscopy for materials research (EMAT)

Project type(s)

• Research Project

Abstract

The goal of this Scientific Research Community (Wetenschappelijke Onderzoeksgemeenschap, WOG) of the FWO-Vlaanderen is to intensify the collaboration between the different research groups in Flanders which are active in the field of the computational modeling of materials. In addition a collaboration with the external partners will be set up or intensified.

Researcher(s)

• Promoter: Lamoen Dirk

Research team(s)

• Electron microscopy for materials research (EMAT)

Project website

Project type(s)

• Research Project

Abstract

The project aims to confront and compare the results of two related techniques for obtaining information on the structural environment of metals in solid materials: X-ray absorption near-edge spectroscopy (XANES) and electron loss near-edge spectroscopy (ELNES). Both probe the density of unoccupied electron states in atoms and the manner in which this distribution is influenced by the neighbours of these atoms. Both methods employ different primary projectiles (resp photons and electrons) and different ways modes of detection; as a result they operate on different length scales.

Researcher(s)

• Promoter: Janssens Koen
• Co-promoter: Lamoen Dirk
• Co-promoter: Verbeeck Johan

Research team(s)

Project type(s)

• Research Project

Abstract

The primary objective of this SBO is to develop advanced tools for pragmatic materials modeling. However, to stimulate the interaction with experimental work at Flamac and their industrial partners early on, we have targeted one application area; particularly optical thin film materials. These applications have been chosen on the basis of their high technological relevance, industrial interest in Flanders, environmental issues, and feasibility to make impact with modeling.

Researcher(s)

• Promoter: Lamoen Dirk
• Co-promoter: Partoens Bart

Research team(s)

• Electron microscopy for materials research (EMAT)

Project website

Project type(s)

• Research Project

Abstract

Within this project we will study in a systematic way the relation between composition and structure versus the electronic and optical properties of transparent conducting oxides (TCO) by means of ab initio electronic structure calculations.

Researcher(s)

• Promoter: Lamoen Dirk
• Co-promoter: Partoens Bart

Research team(s)

• Electron microscopy for materials research (EMAT)

Project website

Project type(s)

• Research Project

Abstract

The phase stability of Ge-Sb-Te alloys is investigated as a function of composition and temperature by means of ab initio electronic structure calculations, cluster expansions and data mining techniques. The presence of vacancies on the Ge/Sb sublattice is fully taken into account and for the ground state structures the optical properties are investigated through a calculation of the dielectric function.

Researcher(s)

• Promoter: Lamoen Dirk

Research team(s)

• Electron microscopy for materials research (EMAT)

Project type(s)

• Research Project

Abstract

Researcher(s)

• Promoter: Van Dyck Dirk
• Co-promoter: Lamoen Dirk
• Fellow: Jorissen Kevin

Research team(s)

• Electron microscopy for materials research (EMAT)

Project type(s)

• Research Project

Abstract

The local (electronic) structure of perovskite-based interfaces will be investigated computationally by means of ab initio electronic bandstructure calculations and the Multiple Scattering technique. In particular the finestructure of the electron energy loss spectrum will be calculated and interpreted in terms of the local (electronic) structure of the interface.

Researcher(s)

• Promoter: Lamoen Dirk

Research team(s)

Project type(s)

• Research Project

Abstract

The aim of the suggested research project is the computation and measurement of electron scattering data in ternary semiconductors, needed for accurate compositional analysis of semiconductor nanostructures such as In(x)Ga(1-x)As quantum wells and quantum dots by high resolution transmission electron microscopy. The planned research project is a collaboration between an experimental group (EMA T, Electronenmicroscopie voor Materiaalonderzoek) and a theory group (TSM, Theoretical Study of Matter) of the University of Antwerp. The goal of the project is twofold. First, structure amplitudes, Debye-Waller factors and static displacement effects will be computed theoretically for technologically interesting materials such as e.g. InGaAs, AIGaAs, GaAsSb, CdZnSe and CdZnS. Second, intensities of diffracted beams will be measured in these materials and compared with our theoretical data. In this way, we aim at providing more reliable data for structure amplitudes and Debye-Waller factors. Our research will improve the accuracy of composition determination in ternary semiconductor nanostructures, and will provide accurate data for any quantitative transmission electron microscopy investigation of these materials. Furthermore, methods developed for theoretical calculation of structure amplitudes and Debye-Waller factors will be applicable to almost any type of material. Therefore, this work will make a substantial contribution to improved quantitative analysis of transmission electron micrographs in general.

Researcher(s)

• Promoter: Lamoen Dirk

Research team(s)

• Electron microscopy for materials research (EMAT)

Project type(s)

• Research Project

Abstract

The goal of the network is to revitalize actinide research and to ensure the highest level of expertise in Europe through the dissemination of knowledge and the organization of education and training activities. The research activities of the participating partners will be brought together and a strong collaboration between the laboratories will be organized e.g. through the exchange of scientists. The network aims at making nuclear research more attractive to young scientists.

Researcher(s)

• Promoter: Lamoen Dirk

Research team(s)

• Electron microscopy for materials research (EMAT)

Project type(s)

• Research Project

Abstract

Calculation of EELS and XAS spectra of actinide oxides e.g. U02, PU02, Am203 by means of ab initio electronic structure calculations. The calculations are performed with the LAPW method within the DFT methodology. In order to get an accurate description of the strong correlation of the 5f electrons we consider both the LDA and the LDA+U approximation for the Exchange-Correlation functional.

Researcher(s)

• Promoter: Lamoen Dirk

Research team(s)

Project type(s)

• Research Project

Abstract

For quantitative electron holography it is essential to know the mean inner potential V0, which describes the phase shift of an electron wave transmitted through a crystalline specimen of thickness t with respect to a reference wave going propagating in vacuum. With an accurate knowledge of the mean inner potential one can precisely determine the specimen thickness. We perform first-principles calculations within the density functional theory formalism to determine the mean inner potential of II-VI semiconductors (e.g. ZnSe, CdSe, ZnS, CdS, ZnO, CdO). In addition we calculate the Debye-Waller factor of those materials, which are needed for quantitative determination of the composition of sphalerite type semiconductor heterostructures by the CELFA method. CELFA compares the local (002) Fourier coefficients of transmission electron microscopy images with (002) Fourier coefficients calculated by Bloch-wave simulations. The local (002) Fourier coefficients strongly depend on the local composition of the heterostructure. The accurate knowledge of the Debye Waller factors of the semiconductors is needed as an input parameter for the Bloch-wave simulations, because the accuracy of the measured composition is directly effected by the accuracy of the Debye-Waller factors used as input.

Researcher(s)

• Promoter: Lamoen Dirk

Research team(s)

Project type(s)

• Research Project

Abstract

Researcher(s)

• Promoter: Lamoen Dirk

Research team(s)

Project type(s)

• Research Project

Abstract

The dynamics of C60 (and C70) molecules encapsulated in single-wall nanotubes, (C60)n@SWNT, will be studied by analytical and numerical theory. Molecular and site symmetry adapted rotator functions will be constructed. A model for the intermolecular potential and the molecule'wall potential will be established. Orientational density distribution functions and correlation functions will be studied. The possibility of orientational and structural phase transitions will be investigated. Raman and NMR experiments will be explained.

Researcher(s)

• Promoter: Michel Karl
• Co-promoter: Lamoen Dirk

Research team(s)

Project type(s)

• Research Project

Abstract

Researcher(s)

• Promoter: Lamoen Dirk
• Promoter: Van Alsenoy Kris
• Fellow: March Norman H.

Research team(s)

Project type(s)

• Research Project

Abstract

This Scientific Research Network of the FWO-Vlaanderen brings brings together several research groups active in the field of Density Functional Theory.

Researcher(s)

• Promoter: Lamoen Dirk

Research team(s)

• Electron microscopy for materials research (EMAT)

Project type(s)

• Research Project

Abstract

The dynamical, thermal and optical properties of carbon nanotubes will be studied computationally within empirical, semi-empirical and ab-initio approaches. In particular, the phonons, elastic moduli, heat capacity, absorption, and Raman spectra will be calculated.

Researcher(s)

• Promoter: Lamoen Dirk

Research team(s)

Project type(s)

• Research Project

Abstract

Researcher(s)

• Promoter: Lamoen Dirk

Research team(s)

Project type(s)

• Research Project

Abstract

It is the purpose of this project to unify a number of theoretical methods and techniques from different fields (quantum chemistry, condensed matter physics and statistical physics) related to molecules and materials into a coherent software package allowing to tackle a wide variety of problems of interest to the industry.

Researcher(s)

• Promoter: Lamoen Dirk
• Promoter: Van Doren Victor
• Co-promoter: Lamoen Dirk

Research team(s)

Project type(s)

• Research Project

Abstract

Study of the thermoelastic behaviour of amorphous polymers (polyglycine and nylons) by using Molecular Dynamics and Monte Carlo simulations. The atomistic calculations are based on empirical interatomic interaction potentials. The elastic constants (and moduli e.g. Young's modulus) are derived from the strain-strain fluctuations within the Parrinello-Rahman approach. The effect of temperature, pressure and additives on the elastic behaviour of the polymers is also investigated.

Researcher(s)

• Promoter: Lamoen Dirk

Research team(s)

Project type(s)

• Research Project

Abstract

In this project the structural, elastic and electronic properties of MgSiO3 will be investigated by means of ab-initio density functional theory. This will be done in collaboration with foreign groups.

Researcher(s)

• Promoter: Lamoen Dirk
• Co-promoter: Van Doren Victor

Research team(s)

Project type(s)

• Research Project

Abstract

Microscopic study of ferroelectricity and structural phase transitions in mixed crystals. Phase transitions in nitrites and perovskites. Dielectric properties. Influence of substitutional disorder on various properties.

Researcher(s)

• Promoter: Michel Karl
• Fellow: Lamoen Dirk

Research team(s)

Project type(s)

• Research Project