| Records |
| Author |
Poppe, R. |
| Title |
Refining short-range order parameters from diffuse electron scattering |
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Doctoral thesis |
| Year |
2023 |
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iv, 150 p. |
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Doctoral thesis; Electron microscopy for materials research (EMAT) |
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Electrons, X-rays and neutrons that pass through a thin crystalline sample will be diffracted. Diffraction patterns of crystalline materials contain Bragg reflections (sharp discrete intensity maxima) and diffuse scattering (a weak continuous background). The Bragg reflections contain information about the average crystal structure (the type of atoms and the average atomic positions), whereas the diffuse scattering contains information about the short-range order (deviations from the average crystal structure that are ordered on a local scale). Because the properties of many materials depend on the short-range order, refining short-range order parameters is essential for understanding and optimizing material properties. The refinement of short-range order parameters has previously been applied to the diffuse scattering in single-crystal X-ray and single-crystal neutron diffraction data but not yet to the diffuse scattering in single-crystal electron diffraction data. In this work, we will verify the possibility to refine short-range order parameters from the diffuse scattering in single-crystal electron diffraction data. Electron diffraction allows to acquire data on submicron-sized crystals, which are too small to be investigated with single-crystal X-ray and single-crystal neutron diffraction. In the first part of this work, we will refine short-range order parameters from the one-dimensional diffuse scattering in electron diffraction data acquired on the lithium-ion battery cathode material Li1.2Ni0.13Mn0.54Co0.13O2. The number of stacking faults and the twin percentages will be refined from the diffuse scattering using a Monte Carlo refinement. We will also describe a method to determine the spinel/layered phase ratio from the intensities of the Bragg reflections in electron diffraction data. In the second part of this work, we will refine short-range order parameters from the three-dimensional diffuse scattering in both single-crystal electron and single-crystal X-ray diffraction data acquired on Nb0.84CoSb. The correlations between neighbouring vacancies and the displacements of Sb and Co atoms will be refined from the diffuse scattering using a Monte Carlo refinement and a three-dimensional difference pair distribution function refinement. The effect of different experimental parameters on the spatial resolution of the observed diffuse scattering will also be investigated. Finally, the model of the short-range Nb-vacancy order in Nb0.84CoSb will also be applied to LiNi0.5Sn0.3Co0.2O2. |
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UA @ admin @ c:irua:200610 |
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9084 |
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| Author |
Vervloessem, E. |
| Title |
The role of pulsing and humidity in plasma-based nitrogen fixation : a combined experimental and modeling study |
Type |
Doctoral thesis |
| Year |
2023 |
Publication |
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Issue |
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Pages |
358 p. |
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Doctoral thesis; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT) |
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Nitrogen (N) is an indispensable building block for all living organisms as well as for pharmaceutical and chemical industry. In a nutshell, N is needed for plants to grow and beings to live and nitrogen fixation (NF) is the process that makes N available for plants as food by converting N2 into a reactive form, such as ammonia (NH3) or nitrogen oxides (NOx), upon reacting with O2 and H2. The aim of this thesis is to elucidate (wet) plasma-based nitrogen fixation with a focus on (1) the role of pulsing in achieving low energy consumption, (2) the role of H2O as a hydrogen source in nitrogen fixation and (3) elucidation of nitrogen fixation pathways in humid air and humid N2 plasma in a combined experimental and computational study. Furthermore, this thesis aims to take into account the knowledge-gaps and challenges identified in the discussion of the state of the art. Specifically, (1) we put our focus on branching out to another way of introducing water into the plasma system, i.e. H2O vapor, (2) we de-couple the problem for pathway elucidation by starting with characterization of the chosen plasma, next a simpler gas mixture and building up from there, (3) we include modelling, though not under wet conditions and (4) we focus on also analyzing species and performance outside liquid H2O. Firstly, based on the reaction analysis of a validated quasi-1D model, we can conclude that pulsing is indeed the key factor for energy-efficient NOx- formation, due to the strong temperature drop it causes. Secondly, the thesis shows that added H2O vapor, and not liquid H2O, is the main source of H for NH3 generation. Related to this, we discuss how the selectivity of plasma-based NF in humid air and humid N2 can be controlled by changing the humidity in the feed gas. Interestingly, NH3 production can be achieved in both N2 and air plasmas using H2O as a H source. Lastly, we identified a significant loss mechanism for NH3 and HNO2 that occurs in systems where these species are synthesized simultaneously, i.e. downstream from the plasma, HNO2 reacts with NH3 to form NH4NO2, which decomposes into N2 and H2O. This reduces the effective NF when not properly addressed, and should therefore be considered in future works aimed at optimizing plasma-based NF. In conclusion, this thesis adds further to the current state of the art of plasma-based NF both in the presence of H2O and in dry systems. |
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| Call Number |
UA @ admin @ c:irua:197038 |
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9088 |
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| Author |
Peeters, H. |
| Title |
Solar active photocatalytic self-cleaning coatings based on plasmon-embedded titania |
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Doctoral thesis |
| Year |
2023 |
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XX, 125 p. |
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Doctoral thesis; Engineering sciences. Technology |
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UA @ admin @ c:irua:201390 |
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9093 |
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Dingenen, F. |
| Title |
Solar-driven H2 production from seawater using stabilized plasmon-enhanced photocatalysts |
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Doctoral thesis |
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2023 |
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XXXVIII, 210 p. |
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Doctoral thesis; Engineering sciences. Technology |
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As natural gas prices proved to be very volatile, sustainable alternatives are highly needed. Water-derived H2 was revealed as a promising substitute, allowing to produce a green energy carrier with a minimum of harmful emissions. Direct splitting of earth-abundant seawater provides an eco-friendly route for the production of clean H2, but is hampered by selectivity and stability issues due to the presence of salts.Photocatalytic seawater splitting is particularly promising for this purpose, as it seems less affected by adversary seawater effects and might rely on free and renewable solar power. Unfortunately, the benchmark photocatalyst, TiO2, still suffers from its low solar light activity. It is only actived upon illumination with energetic ultraviolet light (<5% of the sunlight). In order to broaden the activity window to the visible light, the concept of the 'plasmonic rainbow' was explored. Here, TiO2 is modified with various gold-silver composites that possess the unique optical phenomenon of Surface Plasmon Resonance (SPR). This phenomenon enables the absorption of light at very specific wavelengths, depending on the metal type, size, shape and dielectric environment. The light energy might then be converted into hot carriers, strong local electromagnetic fields and/or heat. By combining multiple composites with various sizes and compositions, a broadband absorption could be obtained, resulting in significantly enhanced activity in photocatalytic model reactions under simulated sunlight. The major disadvantage of these plasmonic nanoparticles is their tendency to oxidize and deactivate. To overcome this, polymer shell stabilization strategies were found to be effective to protect the metal cores. Both conductive and non-conductive polymers were studied. For the former, a mix-and-wait strategy generating polyaniline shells of 2-5 nm was used, whille the latter was based on a Layer-by-Layer approach, allowing (sub) nanometer thickness control. For the actual H2 production experiments, the plasmonic loading was optimized in a pure water:methanol scavenger (7:1) mixture and initially the stabilization strategies proofed to be effective for simulated seawater (0.5M NaCl), even after 2 years. However, in real seawater, the activity decreased drastically due to aggregation of the photocatalyst in the presence of multivalent cations. Finally, facile immobilization strategies using 3D printing showed to be able to yield stable, solar active photocatalyst for real seawater splitting. |
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UA @ admin @ c:irua:203196 |
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9094 |
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Grünewald, L.; Chezganov, D.; De Meyer, R.; Orekhov, A.; Van Aert, S.; Bogaerts, A.; Bals, S.; Verbeeck, J. |
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Supplementary Information for “In-situ Plasma Studies using a Direct Current Microplasma in a Scanning Electron Microscope” |
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Dataset |
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2023 |
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Dataset; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT) |
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Supplementary information for the article “In-situ Plasma Studies using a Direct Current Microplasma in a Scanning Electron Microscope” containing the videos of in-situ SEM imaging (mp4 files), raw data/images, and Jupyter notebooks (ipynb files) for data treatment and plots. Link to the preprint: https://doi.org/10.48550/arXiv.2308.15123 Explanation of the data files can be found in the Information.pdf file. The Videos folder contains the in-situ SEM image series mentioned in the paper. If there are any questions/bugs, feel free to contact me at lukas.grunewaldatuantwerpen.be |
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Most recent IF: NA |
| Call Number |
UA @ admin @ c:irua:203389 |
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9100 |
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Biondo, O. |
| Title |
Towards a fundamental understanding of energy-efficient, plasma-based CO<sub>2</sub> conversion |
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Doctoral thesis |
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2023 |
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221 p. |
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Doctoral thesis; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT) |
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Plasma-based CO2 conversion is worldwide gaining increasing interest. The aim of this work is to find potential pathways to improve the energy efficiency of plasma-based CO2 conversion beyond what is feasible for thermal chemistry. To do so, we use a combination of modeling and experiments to better understand the underlying mechanisms of CO2 conversion, ranging from non-thermal to thermal equilibrium conditions. Zero-dimensional (0D) chemical kinetics modelling, describing the detailed plasma chemistry, is developed to explore the vibrational kinetics of CO2, as the latter is known to play a crucial role in the energy efficient CO2 conversion. The 0D model is successfully validated against pulsed CO2 glow discharge experiments, enabling the reconstruction of the complex dynamics underlying gas heating in a pure CO2 discharge, paving the way towards the study of gas heating in more complex gas mixtures, such as CO2 plasmas with high dissociation degrees. Energy-efficient, plasma-based CO2 conversion can also be obtained upon the addition of a reactive carbon bed in the post-discharge region. The reaction between solid carbon and O2 to form CO allows to both reduce the separation costs and increase the selectivity towards CO, thus, increasing the energy efficiency of the overall conversion process. In this regard, a novel 0D model to infer the mechanism underlying the performance of the carbon bed over time is developed. The model outcome indicates that gas temperature and oxygen complexes formed at the surface of solid carbon play a fundamental and interdependent role. These findings open the way towards further optimization of the coupling between plasma and carbon bed. Experimentally, it has been demonstrated that “warm” plasmas (e.g. microwave or gliding arc plasmas) can yield very high energy efficiency for CO2 conversion, but typically only at reduced pressure. For industrial application, it will be important to realize such good energy efficiency at atmospheric pressure as well. However, recent experiments illustrate that the microwave plasma at atmospheric pressure is too close to thermal conditions to achieve a high energy efficiency. Hence, we use a comprehensive set of advanced diagnostics to characterize the plasma and the reactor performance, focusing on CO2 and CO2/CH4 microwave discharges. The results lead to a deeper understanding of the mechanism of power concentration with increasing pressure, typical of plasmas in most gases, which is of great importance for model validation and understanding of reactor performance. |
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| Call Number |
UA @ admin @ c:irua:197213 |
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9108 |
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Ahmadi Eshtehardi, H. |
| Title |
Combined computational-experimental study on plasma and plasma catalysis for N2 fixation |
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Doctoral thesis |
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2024 |
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160 p. |
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Doctoral thesis; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT) |
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Humanity feels the urge of shifting to a sustainable society more than at any other time in its history. Electrification of chemical industry plays a key role in this transition. The possibility of producing fertilizers from air using renewable electricity, and simultaneously, no greenhouse gas emission, resulted in an increasing interest toward plasma technology as a solution for electrification of a part of the chemical industry in the past few years. Additionally, the activation of nitrogen molecules by vibrational and electronic excitation reactions in plasma can lead to an energy-efficient process. Last but not least, the modularity (fast on/off characteristic) of plasma technology makes it capable of using intermittent renewable electricity on site for the production of fertilizers using air. All these advantages offered by plasma technology make it a potential solution for the on-site production of fertilizers in small and decentralized plants using air and renewable electricity, which leads to a considerable reduction in fertilizer production and transportation costs. However, industrialization of plasma-based NF suffers from several challenges, including challenges of plasma catalysis for the selective production of desired species, the high energy cost of plasma-based NF compared to current industrial processes, and the design and development of scaled up and energy-efficient plasma reactors for industrial purposes. In the framework of this thesis we have tried to add to the state-of-the-art (SOTA) in plasma-based NOx production and deal with its limitations using a combination of experimental and modelling work. |
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2024-06-14 |
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UA @ admin @ c:irua:205246 |
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9139 |
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Cioni, M.; Delle Piane, M.; Polino, D.; Rapetti, D.; Crippa, M.; Arslan Irmak, E.; Pavan, G.M.; Van Aert, S.; Bals, S. |
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Data for Sampling Real‐Time Atomic Dynamics in Metal Nanoparticles by Combining Experiments, Simulations, and Machine Learning |
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2024 |
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Dataset; Engineering sciences. Technology; Electron microscopy for materials research (EMAT) |
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Even at low temperatures, metal nanoparticles (NPs) possess atomic dynamics that are key for their properties but challenging to elucidate. Recent experimental advances allow obtaining atomic‐resolution snapshots of the NPs in realistic regimes, but data acquisition limitations hinder the experimental reconstruction of the atomic dynamics present within them. Molecular simulations have the advantage that these allow directly tracking the motion of atoms over time. However, these typically start from ideal/perfect NP structures and, suffering from sampling limits, provide results that are often dependent on the initial/putative structure and remain purely indicative. Here, by combining state‐of‐the‐art experimental and computational approaches, how it is possible to tackle the limitations of both approaches and resolve the atomistic dynamics present in metal NPs in realistic conditions is demonstrated. Annular dark‐field scanning transmission electron microscopy enables the acquisition of ten high‐resolution images of an Au NP at intervals of 0.6 s. These are used to reconstruct atomistic 3D models of the real NP used to run ten independent molecular dynamics simulations. Machine learning analyses of the simulation trajectories allows resolving the real‐time atomic dynamics present within the NP. This provides a robust combined experimental/computational approach to characterize the structural dynamics of metal NPs in realistic conditions. |
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UA @ admin @ c:irua:205843 |
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9143 |
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De Luca, F.; Abate, S.; Bogaerts, A.; Centi, G. |
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Electrified CO2 conversion : integrating experimental, computational, and process simulation methods for sustainable chemical synthesis |
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Doctoral thesis |
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2024 |
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xv, 152 p. |
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Doctoral thesis; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT) |
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Nowadays, the burning of fossil fuels, particularly petroleum, natural gas, and coal, meets the rising need for power and fuels for automobiles and industries. This has given rise to ecological and climate challenges. This thesis explores these issues from three distinct perspectives: (i) experimental, (ii) computational, and (iii) process simulation, with a focus on studying CO2 as an alternative and economically viable raw material. Firstly, the experimental study is focused on the synthesis, characterization, and testing of novel catalysts for electroreduction of CO2 and oxalic acid, an intermediate product of CO2. Electrocatalysts based on Cu supported by citrus (orange and lemon) peel biomass are prepared. These catalysts exhibit activity in the electrochemical reduction of CO2, emphasizing the effectiveness of biomasses, particularly orange peels, as environmentally friendly precursors for sustainable and efficient electrocatalysts. In addition, graphitic carbon nitrides/TiO2 nanotubes (g-C3N4/TiNT) composites are prepared for the electrocatalytic reduction of oxalic acid to glycolic acid, revealing superior electrocatalytic properties compared to pristine TiNT. Characterization by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electronic microscopy were performed for all the prepared electrocatalysts. Delving into the reduction of CO2 on Cu catalysts, a computational study about the synthesis of methanol on Cu(111) surface is performed by using the Vienna Ab initio Simulation Package. A systematic study is carried out to define the activation energies of the elementary reactions by using mGGA DF. Consequently, it is shown that the rate-controlling step is CH3O* hydrogenation and the formate pathway on Cu(111) proceeds through the HCOOH* intermediate. Finally, the process simulation, performed by using the software Aspen Plus 11 from AspenTech Inc., is based on the comparison of a catalytic (oxidation of ethylene glycol) and an electrocatalytic process (CO2 electroreduction chain) to synthesize glycolic acid. An economic analysis of the operational and investment costs reveals that the catalytic process is more cost-effective due to the current instability of electrocatalysts and proton exchange membranes, resulting in increased maintenance costs and, consequently, higher prices for the product. |
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UA @ admin @ c:irua:205262 |
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9147 |
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Vlasov, E. |
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Exploiting secondary electrons in transmission electron microscopy for 3D characterization of nanoparticle morphologies |
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2024 |
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x, 118 p. |
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Doctoral thesis; Electron microscopy for materials research (EMAT) |
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Electron tomography (ET) is an indispensable tool for determining the three-dimensional (3D) structure of nanomaterials in (scanning) transmission electron microscopy ((S)TEM). ET enables 3D characterization of a variety of nanomaterials across different fields, including life sciences, chemistry, solid-state physics, and materials science down to atomic resolution. However, the acquisition of a conventional tilt series for ET is a time-consuming process and thus cannot capture fast transformations of materials in realistic conditions. Moreover, only a limited number of nanoparticles (NPs) can be investigated, hampering a general understanding of the average properties of the material. Therefore, alternative characterization techniques that allow for high-resolution characterization of the surface structure without the need to acquire a full tilt series in ET are required which would enable a more time-efficient investigation with better statistical value. In the first part of this work, an alternative technique for the characterization of the morphology of NPs to improve the throughput and temporal resolution of ET is presented. The proposed technique exploits surface-sensitive secondary electron (SE) imaging in STEM employed using a modification of electron beam-induced current (EBIC) setup. The time- and dose efficiency of SEEBIC are tested in comparison with ET and superior spatial resolution is shown compared to conventional scanning electron microscopy. Finally, contrast artefacts arising in SEEBIC images are described, and their origin is discussed. The second part of my thesis focuses on real applications of the proposed technique and introduces a high-throughput methodology that combines images acquired by SEEBIC with quantitative image analysis to retrieve information about the helicity of gold nanorods. It shows that SEEBIC imaging overcomes the limitation of ET providing a general understanding of the connection between structure and chiroptical properties. |
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2024-06-17 |
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UA @ admin @ c:irua:204905 |
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9149 |
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Kummamuru, N.B. |
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Methane and hydrogen storage in clathrate hydrates |
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2024 |
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XXV, 260 p. |
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Doctoral thesis; Engineering sciences. Technology; Antwerp engineering, PhotoElectroChemistry & Sensing (A-PECS); Laboratory for the electrification of chemical processes and hydrogen (ElectrifHy) |
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In a world increasingly reliant on alternative energy sources, the quest for efficient and secure storage solutions is paramount. This doctoral thesis explores the exciting potential of a familiar material – water – to act as a vault for next-generation energy sources like hydrogen (H2) and methane (CH4). Nature offers a solution in the form of clathrate hydrates, fascinating cage-like structures formed from water molecules that can trap these gas molecules within their framework. This research investigates on improving the formation kinetics and gas storage capabilities of clathrate hydrates utilizing porous materials and the interstitial space between non-porous materials to augment the contact between gas and water thereby catalysing the growth of hydrates and unlocking their full potential as efficient and secure energy storage reservoirs. A key outcome of this research is the formulation of an empirical correlation, offering predictive insights into CH4 hydrate phase equilibrium conditions. Innovative approaches utilizing thermally conductive beads have yielded substantial enhancements in CH4 uptake. Furthermore, the identification of optimal water content within porous materials showcases a pathway to maximize CH4 storage capacity and hydrate growth kinetics. In the domain of hydrogen storage, attention is also directed towards unstirred systems, where the integration of functionalized porous materials has demonstrated a significant improvement in the rate of hydrate formation and the overall H2 storage capacity. A noteworthy achievement of this research lies in the successful storage of H2 within confined CH4 hydrates through a gas exchange process and the preliminary results show the potential for safer and more sustainable method for H2 storage at mild thermodynamic conditions, offering promising prospects for future energy systems. |
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Approved |
Most recent IF: NA |
| Call Number |
UA @ admin @ c:irua:206258 |
Serial |
9160 |
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| Author |
Lu, Q. |
| Title |
Precipitation behavior and heat resistance properties of Al-Cu-Mg-Ag-(Si) alloy |
Type |
Doctoral thesis |
| Year |
2024 |
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Pages |
VIII, 212 p. |
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Doctoral thesis; Engineering sciences. Technology; Electron microscopy for materials research (EMAT) |
| Abstract |
With the rapid increase in the speed of new-generation aerospace vehicles, conventional heat-resistant aluminum alloys cannot meet the long-term service of the equipment. Therefore, the development of new high-strength heat-resistant aluminum alloys is of great strategic for the sustainable and high-quality development of industries. Al-Cu-Mg-Ag alloy is an age-hardenable heat-resistant aluminum alloy and has high strength and heat resistance. The addition of alloying elements such as Si and Sc to Al-Cu-Mg-Ag alloy introduces a competitive relationship among the σ-Al5Cu6Mg2, θ′-Al2Cu, and Ω phases. Therefore, a systematic investigation of precipitation behavior and heat resistance of Al-Cu-Mg-Ag-(Si) is essential for guiding the design of high-strength heat-resistant aluminum alloys. Combined characterization testing methods such as scanning electron microscopy, transmission electron microscopy, atom probe tomography, microhardness testing, and tensile testing with simulation calculation methods such as calculation of phase diagram, first-principles calculations, and Ab initio molecular dynamics, the effects of heat treatment processes and element content on the precipitation behavior, mechanical properties, and heat resistance of Al-Cu-Mg-Ag-(Si) alloys were systematically investigated. Furthermore, a multiple interface segregation structure was constructed at the θ′/Al interface, and a new Al-Cu-Mg-Ag-Si-Sc alloy with synergistically improved strength and heat resistance was developed. The main conclusions are as follows: (1) Based on the Kampmann-Wagner-Numerical theory, the relationship between the coarsening rate of the Ω phase and the aging process was analyzed, revealing for the first time that the critical size of Ω phase ( ) under thermal exposure temperature was the key factor determining the coarsening rate of Ω phase during long time thermal exposure heat treatment. After artificial ageing, when the size of Ω phase was smaller than the critical size , the dissolution of smaller Ω phase leaded to a rapid decrease in the number density of Ω phases, thereby reducing the heat resistance of the alloy. When the size of Ω phase was greater than or equal to the critical size , the coarsening rate of Ω phase was consistent, but a larger initial size would result in a larger final size after long-term thermal exposure. Therefore, the closer the size of Ω phase in the alloy is to the critical size under heat exposure temperature, the better the heat resistance of the alloy. (2) A concept of constructing a multiple interface segregation structure at the precipitate/matrix interface was proposed, and based on this concept, a multiple interface segregation structure containing the C/L-AlMgSiCu interfacial phase, newly discovered χ-AgMg interfacial phase, and Sc segregation layer was successfully constructed at the θ′/Al interface. The existence of the multiple interface segregation structure ensured that the designed Al-Cu-Mg-Ag-Si-Sc alloy maintains a yield strength of 400 MPa after thermal exposure at 200 C for 100 h, with a strength retention rate of 97%, creating a new record for the synergistic improvement of strength and heat resistance in aluminum alloys. In addition, combining transmission electron microscopy ex-situ/in-situ characterization with first-principles calculations, it is shown that the χ-AgMg interface phase will be destroyed due to the diffusion of the outer Ag layer during thermal exposure, and gradually dissolve into the matrix, but it can still delay the coarsening behavior of θ′-Al2Cu phase. (3) The criteria for determining whether Ω phase can precipitate are updated in Al-Cu-Mg-Ag-Si alloys with low Mg/Si ratio based on phase diagram thermodynamic calculations and multi-scale structural characterization. When W(Mg)/W(Si) > 1.4 and X(Ag)/X(Mgexcess) > 1, Ω phase can precipitate in Al-Cu-Mg-Ag-Si alloys, where X(Mgexcess) represents the atomic percentage of residual Mg elements after the formation of the AlMgSiCu quaternary precipitate phase C/L phase in the supersaturated solid solution, and the W(Mg) is the mass fraction of Mg in the supersaturated solid solution before artificial ageing. (4) The effects of alloy element content on precipitation behavior and heat resistance of Al-Cu-Mg-Ag-Si alloys were systematically analyzed. Critical conditions for the precipitation of σ-Al5Cu6Mg2 and Ω phase in Al-Cu-Mg-Ag-Si alloys are revealed. Based on calculation of phase diagram results, the conditions for precipitating σ-Al5Cu6Mg2 phase in the alloy are: ① W(Mg)/W(Si) > 1.8; ② W(Cu) > 2.7W(Mg) – 5W(Si). When W(Mg)/W(Si) < 1.8, the alloy is mainly precipitated with C/L/Q′-AlMgSiCu. When W(Cu) < 2.7W(Mg) – 5W(Si), the alloy will generate GPB zone. In addition, W(Ag)/W(Si) > 4 is the critical condition which the Ω phase can the main precipitates in Al-Cu-Mg-Ag-Si alloys. Furthermore, the correlation between precipitate types and heat resistance was summarized, showing that Al-Cu-Mg-Ag-(Si) alloys with Ω phase as the main strengthening phase are more suitable for the preparation of structures with short service time but high temperature, while Al-Cu-Mg-Ag-(Si) alloys with low Mg content and multiple segregation structures are more suitable for structures requiring long-term service at medium to high temperatures. This study, for the first time, combines calculation of phase diagram with multi-scale microstructure characterization, systematically unraveling the effects of element content on precipitation behavior, strength, and heat resistance of Al-Cu-Mg-Ag-(Si) alloys. In addition, a concept of constructing a multiple interface segregation structure at the precipitate/matrix interface was proposed to synergistically improve alloy strength and heat resistance. This work provides theoretical guidance for optimizing the composition and processing of Al-Cu-Mg-Ag-(Si) alloy and regulating the microstructure. Furthermore, it also offers new ideas and theoretical guidance for the development of novel high-strength heat-resistant alloys in other systems. |
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Most recent IF: NA |
| Call Number |
UA @ admin @ c:irua:206180 |
Serial |
9167 |
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| Author |
Manaigo, F. |
| Title |
Study of a gliding arc discharge for sustainable nitrogen fixation into NOx |
Type |
Doctoral thesis |
| Year |
2024 |
Publication |
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Issue |
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Pages |
xxiv, 114 p. |
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Doctoral thesis; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT) |
| Abstract |
With the growth of the world population, the agricultural sector is required to meet an increasing demand for nutrients and currently relies on industrially produced fertilizers. Among them, nitrogen-based fertilizers are the most common choice and require N2 to be converted into more reactive molecules in a process called “nitrogen fixation”. This is mainly performed through the Haber-Bosch process, which, is not ideal since it requires large-scale facilities to be economical and is associated with a high energy cost and high CO2 emissions, resulting in an environmental impact that is pushing for the study of greener alternatives. Among these, plasma-based nitrogen fixation into NOx is promising, and gliding arc plasma, specifically, proved to be suitable for nitrogen fixation. This thesis aims to study plasma-based nitrogen fixation focusing on an atmospheric pressure gliding arc plasma on three different levels. On a fundamental level, an approach dealing with laser-based excitation of separate rotational lines was successfully developed. This method can be implemented on atmospheric discharges that produce rather high NOx densities and, thus, can impose essential restrictions for the use of “classical” laser-induced fluorescence methods. The approach is then implemented, providing a discussion on the two-dimensional distributions of both the gas temperature and the NO ground state density. A clear correlation between these quantities is found and the effects of both the gas temperature and the plasma power on NO and NO2 concentrations are discussed, revealing how the NO oxidation is already significant in the plasma afterglow region and how the gas flow rate is a crucial parameter affecting the temperature gradients. >From a technological level, the conventional approach of introducing external resistors to stabilize the arc is challenged by studying both its performance and its stability replacing the external resistor with an inductor. We conclude that similar stabilization results can be obtained while significantly lowering the overall energy cost, which decreased from up to a maximum of 7.9 MJ/mol N to 3 MJ/mol N. Finally, we study whether a small-scale fertilizer production facility based on a gliding arc plasma can be a local competitive alternative. This is done by proposing a comparative model to understand how capital, operative expenditures and transport costs affect the production costs. The model highlights how, with the current best available technology, plasma-based nitrogen fixation, while being an interesting alternative for NOx synthesis, still requires a more efficient use of H2 for direct NH3 production. |
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Most recent IF: NA |
| Call Number |
UA @ admin @ c:irua:205259 |
Serial |
9175 |
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| Author |
Verbruggen, S.; Van Acker, M.; Furlan, C.; Mercelis, S.; Durt, A. |
| Title |
ATLANTES : the mATeriaL spAtial dimeNsion of wasTE flowS: visualising waste streams in the Province of Antwerp |
Type |
Minutes and reports |
| Year |
2023 |
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Minutes and reports; Economics; Engineering sciences. Technology; Internet Data Lab (IDLab); Research Group for Urban Development; Henry van de Velde |
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Approved |
Most recent IF: NA |
| Call Number |
UA @ admin @ c:irua:199837 |
Serial |
9187 |
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| Author |
Van Hoecke, L. |
| Title |
CFD-Assisted design of fluidized reactors for H2 release from LOHC |
Type |
Doctoral thesis |
| Year |
2024 |
Publication |
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Issue |
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Pages |
XXXIII, 181 p. |
| Keywords |
Doctoral thesis; Engineering sciences. Technology |
| Abstract |
Hydrogen (H2) is expected to become a key molecule in the transition towards a society running on renewable energy. It can be used to store excess renewable energy at peak production moments and release this energy at a later stage when renewable energy production is less. However, storing H2 is challenging due to the low density of this gas. As a solution, Liquid Organic Hydrogen Carriers or LOHC molecules have been proposed in the passed to increase volumetric energy density of H2. LOHC are a class of molecules that have storage sites available, to which the H2 gas can be chemically bounded. The LOHC molecule under investigation was dibenzyltoluene (DBT), which is an oil like liquid, that is easy to transport and poses little fire or explosion risks. To release the H2 from the DBT carrier, via a so-called dehydrogenation reaction, efficient mass and heat transfer is required during the process, since a large volume increase is expected from H2 release and the reaction is endothermic, i.e., a self – cooling process that takes place at temperatures around 300 C. The heat has to be supplied specifically to the active sites of catalyst particles that are present inside the reactor and which enable the dehydrogenation to proceed. For heat transfer limited processes fluidized bed reactors are often used, which is a type of reactor where the particle phase is being agitated by the fluid flow. The research proposed in this work, was to explore via computational fluid dynamics (CFD) simulations the possibilities and challenges of using fluidized bed reactors for the dehydrogenation of LOHC. The model selection required for CFD simulations of a three-phase system was investigated in this work, with a main emphasis on the drag model selection. The CFD modelling study was focused on the use of swirling fluidized bed reactors, since it was hypothesised that the swirling effect could also aid in increased removal of the gas phase from the reaction medium to increase the efficiency of the process. Ultimately, it was shown that the main challenges in the design of fluidized bed reactors will be to create uniform particle distribution inside the reactor. A new design for a dehydrogenation reactor is proposed based on the insights gained in this thesis. |
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2024-06-14 |
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Approved |
Most recent IF: NA |
| Call Number |
UA @ admin @ c:irua:205645 |
Serial |
9192 |
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Lembrechts, J.; Clavel, J.; Lenoir, J.; Haider, S.; McDougall, K.; Nunez, M.; Alexander, J.; Barros, A.; Milbau, A.; Seipel, T.; Verbruggen, E.; Nijs, I. |
| Title |
Dataset: Roadside disturbance promotes plant communities with arbuscular mycorrhizal associations in mountain regions worldwide |
Type |
Dataset |
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2024 |
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Dataset; Plant and Ecosystems (PLECO) – Ecology in a time of change |
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Aim: We aimed to assess the impact of road disturbances on the dominant mycorrhizal types in ecosystems at the global level and how this mechanism can potentially lead to lasting plant community changes. Location: Globally distributed mountain regions Time Period: 2007-2018 Taxa studied: Plants (linked to their associated mycorrhizal fungi) Methods: We used a database of coordinated plant community surveys following mountain roads from 894 plots in 11 mountain regions across the globe in combination with an existing database of mycorrhizal-plant associations in order to approximate the relative abundance of mycorrhizal types in natural and disturbed environments. Results: Our findings show that roadside disturbance promotes the cover of plants associated with arbuscular mycorrhizal (AM) fungi. This effect is especially strong in colder mountain environments and in mountain regions where plant communities are dominated by ectomycorrhizal (EcM) or ericoid-mycorrhizal (ErM) associations. Furthermore, non-native plant species, which we confirmed to be mostly AM plants, are more successful in environments dominated by AM associations. Main Conclusions: These biogeographical patterns suggest that changes in mycorrhizal types could be a crucial factor in the worldwide impact of anthropogenic disturbances on mountain ecosystems. Indeed, roadsides foster AM-dominated systems, where AM-fungi might aid AM-associated plant species while potentially reducing the biotic resistance against invasive non-native species, often also associated with AM networks. Restoration efforts in mountain ecosystems will have to contend with changes in the fundamental make-up of EcM- and ErM plant communities induced by roadside disturbance. |
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Approved |
Most recent IF: NA |
| Call Number |
UA @ admin @ c:irua:206132 |
Serial |
9198 |
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Clavel, J. |
| Title |
Plant-mycorrhizal interactions and their role in plant invasions in mountains |
Type |
Doctoral thesis |
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2024 |
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Pages |
182 p. |
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Doctoral thesis; Plant and Ecosystems (PLECO) – Ecology in a time of change |
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Non-native species invasions are one of the most impactful drivers of biodiversity and ecosystem services loss worldwide. One aspect of plant species invasion, which is only recently starting to be recognized as a determinant of invasion success, is the symbiosis between plant and mycorrhizal fungi. Here, I focus on anthropogenic disturbance in mountain ecosystems and its impact on plant communities and mycorrhizal fungi to answer how these communities are impacted by disturbance and whether non-native plants can benefit to establish and spread. To this end I used a combination of different approaches: 1) repeated surveys of plants and arbuscular mycorrhizal fungi along disturbed roadsides in the mountains of Norway, 2) combining a global dataset of native and non-native plants along mountain roads with a database associating plants with their mycorrhizal types, and 3) an in-situ experiment measuring non-native plant success and changes in fungal community following different types of disturbances. Through these methods, I could assess the effects of anthropogenic disturbance on mycorrhizal symbiosis and non-native plant species at multiple scales and resolutions. We found that road disturbance has a globally consistent effect on mycorrhizal types in mountain systems, as plants associated with arbuscular mycorrhizal (AM) fungi were more abundant following disturbance. Conversely, vegetation associated with either ectomycorrhizal (EcM) or ericoid mycorrhizal (ErM) fungi was less abundant in disturbed sites. In the regional study, AM fungi were most abundant and diverse in the roots of plant communities affected by road disturbance. Non-native plants were also restricted to these disturbed sites. The experimental results showed that physical disturbance and nutrient addition have negative effects on EcM fungi and positive effects on fungal pathogens, and facilitate non-native plant success. Our results show that anthropogenic disturbance does have an effect on mycorrhizal fungi that in turn impacts the distribution of plant species in disturbed mountain systems. The resulting shift in mycorrhizal fungi benefiting AM fungi and AM plant species could have implications for non-native plant invasions. Indeed, we know that non-native plants predominantly form associations with AM fungi. Therefore, anthropogenic disturbance can facilitate non-native plant success through disruption of the native fungal communities, and especially so in high elevation and cold climate regions which are naturally less dominated by AM plants. I believe this highlights the importance of mycorrhizal symbiosis in understanding plant invasions and emphasizes the importance of monitoring sources of anthropogenic disturbance in mountains to prevent future establishment of non-native plants. |
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Most recent IF: NA |
| Call Number |
UA @ admin @ c:irua:204154 |
Serial |
9219 |
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Ramirez-Rojas, I. |
| Title |
Underground connections : the interplay between tropical rainforest trees and soil microbial communities |
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Doctoral thesis |
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2024 |
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205 p. |
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Doctoral thesis; Plant and Ecosystems (PLECO) – Ecology in a time of change |
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Tropical rainforests host an exceptional biodiversity and play a fundamental role in the regulation of global climatic cycles. Soil fungi and bacteria are key players in the transformation and processing of nutrients in terrestrial ecosystems while having an essential role as tree mutualists or antagonists. Still, there are gaps in our understanding of the main variables driving soil microbes on these forests and it is unclear how future climate change scenarios may impact soil microbes and further affect the ecosystem. In this thesis, we first explored the drivers of the microbial community composition in two pristine forests in French Guiana by using amplicon DNA sequencing. The neighboring tree species were found to be a crucial factor influencing the fungal and bacterial community composition at our sites regardless of the season. Additionally, within the environmental factors explored, soil moisture, phosphorus (P) and nitrogen (N) availability were consistently the main soil properties controlling the composition of soil microbial communities. Secondly, as increased nutrient deposition due to anthropogenic activities are expected to affect tropical forests ecosystems N and P availability, a factorial N and P nutrient addition experiment in the same sites was used to assess the effects of changes in the soil nutrient stoichiometry on the soil microbial communities. These results showed that after 3 years of nutrient additions, the bacterial and fungal community composition was affected by both the N and P additions. Besides, the fungal community composition had a stronger response to the nutrient addition, especially when P was added. Moreover, when the nutrient addition effect was assessed in bacteria and fungi with different life strategies, we found different nutrient optima between them. Furthermore, to study the effect of the connection to an existing mycorrhizal mycelium on tree seedlings, I established a mycelium exclusion experiment. Interestingly, we could not detect an effect of the mycorrhizal mycelium exclusion on the seedling N uptake, performance, or fungal community composition in roots after one year. All together this work provides a deeper understanding of the factors influencing the soil microbial communities on these lowland tropical forests, demonstrating that the tree community composition exerts a higher influence on the soil microbial community composition than previously expected. Moreover, our results show that the fungal and bacterial community composition and its relationship with trees in the vicinity is highly dependent on the ecosystem nutrient availability. |
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Most recent IF: NA |
| Call Number |
UA @ admin @ c:irua:204907 |
Serial |
9237 |
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| Author |
Li, L. |
| Title |
Untangling microbial community assembly in rainforest and grassland soils under increasing precipitation persistence |
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Doctoral thesis |
| Year |
2023 |
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179 p. |
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Doctoral thesis; Integrated Molecular Plant Physiology Research (IMPRES); Plant and Ecosystems (PLECO) – Ecology in a time of change |
| Abstract |
Climate change is causing alterations in precipitation patterns, leading to adverse ecological consequences in many ecosystems. Recently, an increasingly persistent weather pattern has emerged, characterized by lengthening the duration of alternating dry and wet periods, which is more complex than exclusively drought or increasing precipitation. It is currently unclear how soil microbial communities respond to these new regimes in relation to their interactions with plants, especially in precipitation-sensitive ecosystems, such as tropical rainforests and grasslands. In this thesis, we explored responses of soil bacterial and fungal communities to increasing weather persistence in rainforests and grasslands, using high throughput sequencing technology. We firstly investigated the resistance and resilience of microbial communities to prolonged drought in a mature seasonal tropical rainforest which experiences unusually intensive dry seasons in the current century. Through excluding rainfall during and after the dry season, a simulated prolongation of the dry season by five months was compared to the control. Our results indicate that as rain exclusion progressed, the microbial communities increasingly diverged from the control, indicating a moderate resistance to prolonged drought. However, when the drought ceased, the composition and co-occurrence patterns of soil microbial communities immediately recovered to that in the control, implying a high resilience. To further investigate the ecological roles of soil microbial communities in response to increasing weather persistence, we set up grassland mesocosm experiments. In these experiments, precipitation frequency was adjusted along a series, ranging from 1 to 60 consecutive days alternating of dry and wet periods, while keeping the total precipitation constant. Our results show that microbial community assembly tended to be more stochastic processes at intermediate persistence of dry and wet alternations while more deterministic processes dominated at low and high persistence within 120 days regime exposure. Moreover, more persistent precipitation reduced the fungal diversity and network connectivity but barely impacted that of bacterial communities. The prior experiences of persistent weather events for one year caused legacy effects. The soil microbial legacy induced by soil microbial communities subjected to prior persistent weather events was more enduring in subsequent fungal communities than bacterial communities, likely due to slower growth of fungi compared to bacteria. However, a minor effect of soil microbial legacy was observed on plant performance. In addition, we kept the grassland mesocosm experiment for two growing seasons. The effects of precipitation persistence on soil microbial communities increased in the second year. The dissimilarities of microbial communities between the first and second year were less with more persistent precipitation, potentially resulting in more vulnerable microbial communities, due to some taxa disappearing and a reduction in functional redundancy under more persistent weather. To conclude, our findings provide a comprehensive theoretical understanding of soil microbial communities in response to the current and future climate change, drawing from both natural and experimental systems. It helps in predicting and managing the impacts of future climate change on ecosystems mediated by microbial communities. Additionally, the findings of microbe-mediated legacy effects on grassland ecosystems can provide practical guidance for their application in agriculture, specifically for using an inoculum to mitigate the impacts of climate change. |
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Most recent IF: NA |
| Call Number |
UA @ admin @ c:irua:198498 |
Serial |
9240 |
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Montiel, F.N. |
| Title |
Voltage against illicit drug trafficking : capabilities of electrochemical fingerprinting to detect illicit drugs |
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Doctoral thesis |
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2024 |
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256 p. |
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Doctoral thesis; Pharmacology. Therapy; Engineering sciences. Technology; Antwerp Electrochemical and Analytical Sciences Lab (A-Sense Lab) |
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Most recent IF: NA |
| Call Number |
UA @ admin @ c:irua:204707 |
Serial |
9243 |
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Schryvers, N. |
| Title |
De hoogspanningselektronenmicroscoop JEM 1250 |
Type |
H3 Book chapter |
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2024 |
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54-55
T2 - Verhalenvertellers : academisch erfgoed |
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H3 Book chapter; Documentation and information; Engineering sciences. Technology; History; Electron microscopy for materials research (EMAT) |
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Abbreviated Series Title |
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Edition |
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ISBN |
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Additional Links |
UA library record |
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Times cited |
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Open Access |
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| Notes |
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Approved |
Most recent IF: NA |
| Call Number |
UA @ admin @ c:irua:208055 |
Serial |
9282 |
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| Author |
Vanhooydonck, A.; Vleugels, J.; Parrilla Pons, M.; Clerx, P.; Watts, R. |
| Title |
Digital Repository : Optimizing high accuracy 8K LCD 3D-printed Hollow Microneedles: Methodology and ISO-7864:2016 Guided Evaluation for Enhanced Skin Penetration |
Type |
Dataset |
| Year |
2024 |
Publication |
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Abbreviated Journal |
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Issue |
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Pages |
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| Keywords |
Dataset; Engineering sciences. Technology; Product development; Antwerp Electrochemical and Analytical Sciences Lab (A-Sense Lab); Antwerp engineering, PhotoElectroChemistry & Sensing (A-PECS) |
| Abstract |
This dataset contains 30 STL files of different geometries of microneedles (face angle, inner diameter, outer diameter, wall thickness) which are 3D printable using mSLA printers. |
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Wos |
https://github.com/AndresVHD/Optimizing_high_accuracy_8K-LCD_3D-printed_Hollow_Microneedles-Digital_ |
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Abbreviated Series Title |
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Additional Links |
UA library record; https://github.com/AndresVHD/Optimizing_high_accuracy_8K-LCD_3D-printed_Hollow_Microneedles-Digital_Supplement/tree/main/CAD_Files/MN_Configurations |
| Impact Factor |
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Times cited |
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Open Access |
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| Notes |
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Approved |
Most recent IF: NA |
| Call Number |
UA @ admin @ c:irua:208524 |
Serial |
9283 |
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| Author |
Gao, C. |
| Title |
Exploring electron ptychography for low dose imaging |
Type |
Doctoral thesis |
| Year |
2024 |
Publication |
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Abbreviated Journal |
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Issue |
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Pages |
xii, 146 p. |
| Keywords |
Doctoral thesis; Electron microscopy for materials research (EMAT) |
| Abstract |
Transmission electron microscopy is an important technique in the exploration of materials’ structures. This is especially true since the development of electron optical aberration correctors greatly facilitated atomic resolution imaging. We are currently experiencing an ongoing revolution in electron microscopy with the widespread adoption of direct electron detectors. Scientists have reported a lot of key scientific findings facilitated by direct electron detectors. One particular research domain is electron ptychography, which holds promise for unraveling the intricate structures of highly beam-sensitive materials like bio samples and achieving super-resolution without the limitation of aperture in the condenser lens system. Nevertheless, challenges persist both in experimental setups and algorithmic processes. Issues such as the comparatively sluggish scanning speed of cameras and contrast reversals of the reconstructed phase for relatively thick specimens, disrupting phase or weak phase approximations, remain noteworthy limitations. This thesis addresses these challenges by the event-driven Timepix3 detector, presenting a viable solution to the speed bottleneck. Moreover, innovative approaches for applying electron ptychography to relatively thick samples, employing a middle focusing strategy, are proposed. This research aims to push the boundaries of electron microscopy, offering solutions to existing limitations and advancing the field towards more efficient and accurate imaging techniques. |
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Wos |
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Publication Date |
2024-07-18 |
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Abbreviated Series Title |
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Series Issue |
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Edition |
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Additional Links |
UA library record |
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Times cited |
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Open Access |
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| Notes |
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Approved |
Most recent IF: NA |
| Call Number |
UA @ admin @ c:irua:206777 |
Serial |
9289 |
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| Author |
Chinnabathini, V.C. |
| Title |
Gas phase bimetallic nanoclusters-modified TiO2 supports as efficient photo(electro)catalysts for self-cleaning surfaces and water splitting |
Type |
Doctoral thesis |
| Year |
2024 |
Publication |
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Abbreviated Journal |
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Issue |
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Pages |
xviii, 149 p. |
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Doctoral thesis; Antwerp engineering, PhotoElectroChemistry & Sensing (A-PECS) |
| Abstract |
In the context of global challenges such as climate change and environmental pollution, photocatalysis evolved as one of the promising strategies for sustainable energy conversion and pollutant degradation. In this thesis, photocatalysis using gas phase deposited bimetallic nanoclusters (BNCs) on TiO2 supports is studied in the context of self-cleaning surfaces and photoelectrochemical (PEC) water splitting applications. Thanks to their plasmonic properties, BNCs made of coinage metals can serve as efficient cocatalysts for the degradation of organic pollutants and surface contaminants under light irradiation. They also hold great promise for PEC water splitting, a promising pathway for renewable hydrogen production, which can be used in hydrogen fuel cells or for the environmentally friendly production of fuels in, for example, CO2 hydrogenation processes. The small size and high surface-to-volume ratio of plasmonic BNCs play pivotal roles in influencing the efficiency and selectivity of photocatalytic processes. BNCs have unique optical, physical, chemical, and structural properties distinctly different from their bulk and monometallic counterparts. These properties can be fine-tuned at the single particle level by their size, composition, and atomic arrangement, but also by interaction with other particles through the coverage and through interaction with the support. To design better photocatalysts it is crucial to carefully understand the BNCs’ characteristic properties, especially at the atomic level where synergies between different elements are sought. To achieve this objective, BNCs with well-defined sizes and compositions are deposited on TiO2 supports and we studied their structural properties and their influence on the photocatalytic activity. The general procedure followed in this thesis is the production and deposition of BNCs on TiO2 by the cluster beam deposition (CBD) technique, followed by structural and optical characterization to understand their tailored properties, and photocatalytic testing either for photodecomposition of organic molecules or PEC water splitting. In a first study, AuxAg1-x (x = 1, 0.9, 0.7, 0.5, 0.3, and 0) alloy BNCs with different compositions are synthesized in the gas phase and deposited from a molecular beam on TiO2 P25 supports. The photocatalytic self-cleaning activity of as-prepared samples is tested under UV and visible light towards stearic acid (SA) degradation. SA is a widely accepted model contaminant, which represents the group of organic fouling compounds that typically contaminates glass surfaces. A composition-dependent activity is observed with the Au0.3Ag0.7 nanocluster modified TiO2 exhibiting the highest photoactivity. Scanning transmission electron microscopy (STEM) measurements reveal that, for a mass loading corresponding to an equivalent of 4 atomic monolayers (MLs), the BNCs are uniformly distributed over the surface. The clusters have an average size of 3.5 ± 0.5 nm and are crystalline in nature. The atomic structure is characterized by X-ray absorption fine structure (XAFS) spectroscopy and their electronic structure by X-ray photoelectron spectroscopy (XPS). These measurements demonstrate a charge redistribution between the Ag and Au atoms when alloyed at the nanoscale. The effect of this charge redistribution is likely the stabilization of Ag against oxidation and directly affects the catalytic properties of the clusters. It is suggested that the highest photoactivity of 4 ML loaded Au0.3Ag0.7 under solar light results from a combination of four main possible contributing factors: (i) injection in TiO2 of excited carriers that are generated by the localized surface plasmon resonance (LSPR) effect of the BNCs in the visible light wavelength range which overlaps with the sun’s irradiance spectrum. (ii) a strong near-field enhancement that increases the photoabsorption by the TiO2 for photons that have enough energy to overcome the high bandgap, (iii) the optimized total metal loading of 4 ML leaves enough of the TiO2 surface accessible for light absorption, and finally (iv) an effective charge distribution between Au and Ag. This study demonstrates that CBD is an efficient approach for fabricating well-defined, tunable AuAg plasmon-based photocatalysts for self-cleaning applications, outperforming their monometallic counterparts as well as bimetallic alternatives obtained through colloidal methods. In a second study, titania nanotubes (TNTs) are modified with a series of AuxCu1-x (x = 1, 0.75, 0.5, 0.25, and 0) BNCs using the CBD technique. Based on the results of the first study, we opted again for a loading of 4 ML. TNTs are known for their high surface area, fast charge transfer, and corrosion resistance, while keeping the inherent strengths of traditional TiO2 materials. They prove to be promising photoanodes, enhancing photocurrent in PEC applications for water oxidation. In this work the TNTs are grown via anodic oxidation of a titanium metal foil. The crystalline anatase phase of the grown TNTs is confirmed by the X-ray diffraction technique (XRD), while transmission electron microscopy (TEM) provides information about the size and composition of the deposited BNCs. XAFS provides further structural information, while XPS measurements reveal charge redistribution between Au and Cu, which can aid in the enhancement of the PEC activity. Oxidation of as-prepared electrodes over the time results in structural changes with CuxO at the outer shell functioning as a protective layer, while the majority of the core is an alloy. The optical properties, studied through UV-Vis spectroscopy confirm the extended absorption range of the cluster-modified TNTs towards the visible region. The charge carrier recombination rate is derived from photoluminescence (PL) measurements. The as-prepared electrodes are tested photoelectrochemically for the generation of an anodic photocurrent using simulated sunlight. It is found that the AuxCu1-x (x = 1, 0.75, 0.5, 0.25 and 0) BNC modified TNTs show a remarkable enhancement in the anodic photocurrent relative to pristine TNTs, with Au0.25Cu0.75 exhibiting the highest photocurrent. This is due to the combination of many possible factors. Firstly, the charge redistribution between Au and Cu and increase stability of the Au0.25Cu0.75 electrode as observed in XAFS, indicates that the electronic effect in the cluster is also one of the governing factors for PEC activity. Secondly, formation of a surface CuOx layer, protects against further corrosion of the metallic AuCu BNCs cores. Third, reduced recombination of charge carriers is indicated by lower photoluminescent (PL) intensity compared to pristine TNTs and all other electrodes except pure gold, as observed in PL spectra. This implies that the generated charge carriers are efficiently separated by Au0.25Cu0.75 NCs acting as electron sinks and easily available for redox reactions. Fourth, the highest interfacial charge transfer efficiency is evidenced by the electrochemical impedance spectroscopy (EIS), leading to more efficacious charge migration and separation, facilitating the water oxidation surface reaction. A final beneficial factor is the uniform deposition of well-defined, size- and composition-controlled, ligand-free BNCs. Such BNCs provide more effective surface sites to the reaction medium, in contrast to electrodes synthesized by e.g. sol-gel methods, where (in)organic residues on metal surfaces may decrease the efficiency. |
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Publication Date |
2024-07-04 |
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Additional Links |
UA library record |
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Times cited |
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Open Access |
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| Notes |
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Approved |
Most recent IF: NA |
| Call Number |
UA @ admin @ c:irua:206758 |
Serial |
9293 |
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| Author |
Abadeen, A.Z.U.; Omranian, S.R.; Abdellati, Y.; Ag, K.R.; Verbruggen, S.; Vuye, C. |
| Title |
Investigating the potential effects of limestone and bitumen substrates on photocatalytic NOx degradation |
Type |
P1 Proceeding |
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2024 |
Publication |
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1 |
Issue |
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Pages |
3-12
T2 - Proceedings of the 10th International Co |
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P1 Proceeding; Engineering sciences. Technology; Sustainable Pavements and Asphalt Research (SuPAR); Antwerp engineering, PhotoElectroChemistry & Sensing (A-PECS) |
| Abstract |
NOx emissions commonly emitted by vehicles, pose environmental and health challenges worldwide. Photocatalytic asphalt pavements, used in urban settings, are in close contact with these emissions. In this study, the contribution and role of asphalt mix components—stone and bitumen—were analyzed in the degradation process. The effectiveness of TiO2 coatings on limestone-bitumen composites of varying ratios (100%, 75%, 50%, 25%, and 0%) was assessed using X-ray diffraction analysis (XRD), Confocal Laser Scanning Microscopy (CLSM), Fourier-transform infrared spectroscopy (FTIR), and the modified ISO 22197-1:2016 standard for NO removal. XRD verified the presence of calcite in limestone. CLSM revealed surface modifications and coating morphology, FTIR verified successful TiO2 PF2 coating deposition and NOx degradation quantified the NOx degradation (%), NO degradation (%) and NO2 formation (%) during photocatalytic activity. It was evident that samples with a higher ratio of stone-to-bitumen exhibited an elevated NOx degradation, reaching up to 29.11% for NOx, 43.79% for NO, and 13.96% for NO2 formation. Conversely, samples with a lower stone-to-bitumen ratio recorded values as low as 8.93% for NOx degradation (%), 10.30% for NO degradation (%), and 0.95% for NO2 formation (%). These outcomes firmly establish the inhibitory effect of the bitumen substrate on NOx and NO degradation but a positive effect on NO2 formation. |
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Publication Date |
2024-07-20 |
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978-3-031-63587-8 |
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UA library record |
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Open Access |
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Approved |
Most recent IF: NA |
| Call Number |
UA @ admin @ c:irua:207349 |
Serial |
9299 |
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| Author |
Janssens, K.; Van der Snickt, G. |
| Title |
De macroscopische X-straal fluorescentiescanner voor schilderijen |
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H3 Book chapter |
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2024 |
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Pages |
36-37
T2 - Verhalenvertellers : academisch erfgoed |
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H3 Book chapter; Documentation and information; Engineering sciences. Technology; Art; History; Antwerp Cultural Heritage Sciences (ARCHES); Antwerp X-ray Imaging and Spectroscopy (AXIS) |
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Additional Links |
UA library record |
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Open Access |
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Approved |
Most recent IF: NA |
| Call Number |
UA @ admin @ c:irua:208047 |
Serial |
9303 |
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| Author |
Pascucci, F. |
| Title |
Superfluidity in exciton bilayer systems : Josephson effect and collective modes as definitive identification-markers |
Type |
Doctoral thesis |
| Year |
2024 |
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Pages |
xiii, 126 p. |
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Doctoral thesis; Theory of quantum systems and complex systems; Condensed Matter Theory (CMT) |
| Abstract |
This thesis explores superfluidity in exciton bilayer systems, semiconductor structures with two thin conducting layers, one doped with electrons and the other with holes, separated by a few nanometers. Theoretical predictions suggest these systems can exhibit superfluid, supersolid, exciton normal solid, and Wigner crystal phases. Identifying clear markers of superfluidity is crucial due to experimental challenges in confirming excitonic superfluidity. This thesis focuses on two phenomena: the Josephson effect and density collective modes. For the Josephson effect, we propose an exciton bilayer Josephson junction in double monolayer Transition Metal Dichalcogenides. We suggest using the Shapiro method to measure the exciton Josephson current and propose fabricating the device with a tunable potential-barrier height. In low potential-barrier regions, the exciton superfluid flows over the barrier, while in high potential-barrier regions, flow is driven by quantum tunnelling. This helps delineate the boundary between Bose-Einstein Condensate (BEC) and BCS-BEC crossover regimes. For density collective modes, we examine low-temperature behaviour to identify the normal-superfluid transition as a function of density. In the normal state at high density, the system exhibits low-energy optic and acoustic modes. As density decreases, entering the superfluid phase, the response changes, with the superfluid gap blocking these modes. We expect pair-breaking collective modes to appear at the onset of exciton superfluidity due to the Coulomb interaction. Our theoretical model developed using a path-integral approach and the Hartree-Fock approximation, includes screening and intralayer correlations. We calculate gap and number equations governing superfluid phase behaviour, showing that intralayer correlations enhance screening, especially in the BCS-BEC crossover regime. This leads to a reduced superfluid gap, a shift in the BEC to BCS-BEC crossover boundary to lower densities, and the disappearance of a predicted minimum in electron-hole pair size. This study advances the understanding of superfluidity in exciton bilayer systems, providing theoretical predictions and experimental proposals. By identifying clear markers of superfluidity, this work contributes to the broader effort of realizing and characterizing excitonic condensed phases in realistic systems. |
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Publication Date |
2024-09-13 |
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Open Access |
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Approved |
Most recent IF: NA |
| Call Number |
UA @ admin @ c:irua:207852 |
Serial |
9318 |
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| Author |
Zhang, Y.; Grünewald, L.; Cao, X.; Abdelbarey, D.; Zheng, X.; Rugeramigabo, E.P.; Zopf, M.; Verbeeck, J.; Ding, F. |
| Title |
Supplementary Information and Data for “Unveiling the 3D Morphology of Epitaxial GaAs/AlGaAs Quantum Dots” |
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Dataset |
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2024 |
Publication |
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Issue |
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Dataset; Engineering sciences. Technology; Electron microscopy for materials research (EMAT) |
| Abstract |
Raw and processed TEM and AFM data for the article Unveiling the 3D Morphology of Epitaxial GaAs/AlGaAs Quantum Dots. |
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Additional Links |
UA library record |
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Times cited |
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Open Access |
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| Notes |
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Approved |
Most recent IF: NA |
| Call Number |
UA @ admin @ c:irua:208086 |
Serial |
9319 |
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| Author |
Ninakanti, R. |
| Title |
Synthesis and electron microscopy characterization of novel core-shell and self-assembled nanostructures for plasmon-enhanced photocatalysis |
Type |
Doctoral thesis |
| Year |
2024 |
Publication |
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Abbreviated Journal |
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Issue |
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Pages |
163 p. |
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Doctoral thesis; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Antwerp engineering, PhotoElectroChemistry & Sensing (A-PECS) |
| Abstract |
The global challenge posed by increasing levels of greenhouse gases and the associated detrimental impacts of global warming necessitate a strategic shift from traditional fossil fuel-based energy systems to more sustainable, renewable, and circular energy and material solutions. Consequently, the potential of photoactive nanoparticles, particularly those that harness light-driven processes, has captured extensive scientific interest as a viable approach to mitigating energy and environmental challenges on a global scale. Although, the adoption of solar light based solutions in the chemical industry has been very less due to sluggish reaction rates and its cascading effects on its economics. The primary focus of this dissertation is the study of plasmonic metal nanoparticles and metal oxide nanoparticles, emphasizing their applications in light-driven energy conversion. The distinctive properties of plasmonic materials, especially surface plasmon resonance (SPR), are pivotal in these applications. SPR involves the oscillation of electron clouds at the surface of nanoparticles when resonating with incident electromagnetic radiation, significantly enhancing solar radiation absorption. This feature is crucial for addressing the limitations of semiconductor photocatalysts like TiO2, which typically exhibit restricted absorption of solar irradiation. The objective of this dissertation is to further optimize the plasmonic enhancement mechanisms by strategically tuning the interactions between plasmonic nanoparticles and TiO2. This is achieved through the development of core-shell nanostructures and the self-assembly of supraparticles, designed to enhance plasmonic photocatalytic systems. The dissertation begins by elucidating the basic concepts and ideations behind the construction of these nanostructures and their roles in enhancing plasmonic photocatalysis, focusing on mechanisms such as near-electric field enhancement, electron transfer, and enhanced photon absorption. To achieve these objectives, modified synthesis techniques were developed to fabricate novel Au@TiO2 core-shell structures with precisely controlled TiO2 shell thickness and self-assembled Au-TiO2 supraparticles with variable sizes. The thesis further delves into the structural characterization of these synthesized nanoparticles, introducing both basic and advanced electron microscopy techniques. For the specific applications of these structures, it was found that Au@TiO2 core-shell nanoparticles with an optimal 4nm TiO2 shell thickness show significant enhancement in the hydrogen evolution reaction. Additionally, the largest Au-TiO2 supraparticles demonstrate superior efficacy in hydrogen peroxide generation. This work not only deepens the scientific understanding of plasmonic materials but also contributes to the development of renewable energy materials. |
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Publication Date |
2024-07-04 |
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Abbreviated Series Title |
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Series Issue |
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Edition |
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ISBN |
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Additional Links |
UA library record |
| Impact Factor |
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Times cited |
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Open Access |
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| Notes |
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Approved |
Most recent IF: NA |
| Call Number |
UA @ admin @ c:irua:206768 |
Serial |
9320 |
| Permanent link to this record |
