Considering the global effort to combat climate change, a promising solution in reducing CO2 emissions is the Carbon Capture and Storage (CCS) application. Such projects aim to store CO2 inside subsurface geological formations. Depleted gas reservoirs are considered as one of the best options for CCS projects to take place. However, one of the main challenges that can be encountered is the impairment of CO2 injectivity near the well caused by the formation of CO2 hydrates which further result in porosity and permeability reduction of the reservoir rock. While the thermodynamic boundaries have been extensively studied, the kinetics of CO2 hydrates inside porous media remain less investigated. So, this study investigates the kinetic behavior of CO2 hydrate during both formation and dissociation within Bentheimer sandstone core samples under varying thermal conditions, aiming to get a better understanding of how thermal delivery either during hydrate formation with cooling or during hydrate dissociation with heating can affect the hydrates. On top of that, the effect of subcooling as a driving force is also investigated. During the experimental work of the study multiple core flood experiments with constant CO2 injection (dynamic conditions) were conducted, applying different cooling and heating methods, with a specific focus on subcooling and the rates of thermal stimulation. A combination of pressure and temperature monitoring, computed tomography (CT) imaging and permeability measurements were employed to evaluate hydrate behavior in real time. The results showed that subcooling is a dominant driving force and higher degrees of subcooling resulted in shorter induction times, increased hydrate saturation, and greater permeability reductions. Very fast cooling rates led to faster hydrate formation which further resulted in greater permeability losses. Conversely, constant higher heating rates caused more hydrate dissociation and faster permeability recovery. A temperature threshold below the hydrate equilibrium temperature was consistently identified, where significant dissociation occurred, indicating that the porous medium inhibits hydrate formation and promotes hydrate dissociation. Hydrates formed under non-constant cooling dissociated more easily, while slow constant cooling resulted in hydrates that were more resistant. Despite full dissociation across all experiments a residual permeability loss of 8-10 % was observed. Additionally, hydrates formed under constant cooling methods displayed different permeability behavior compared to those formed under non-constant cooling methods, indicating a potential difference in pore-scale hydrate distribution. This thesis will delve into how temperature and subcooling can impact the kinetics of CO2 hydrates formation and dissociation within the context of CCS in depleted gas reservoirs.

Indium tin oxide (ITO) has been extensively used as a transparent conductive oxide (TCO) material due to its excellent optical and electrical properties. The ITO layer is applied on the front and rear sides of the front-back contact (FBC) SHJ cells. As the front TCO layer, ITO provides anti-reflective features and facilitates the lateral transport of electrons. Conversely, a well-engineered rear TCO layer facilitates favorable band alignment for charge carrier collection and enhances the reflection of near-infrared light. However, the consumption of indium for solar cell applications competes with the growing demand across other industries. Furthermore, indium is scarce and expensive, contributing to the increase in capital expenditure. As a result, research into the feasibility of eliminating the TCO layer has gained significant interest in the past few years. While the concept of TCO-free solar cells has been demonstrated in limited studies with efficiencies exceeding 20%, TCO-free FBC-SHJ solar cells employing copper- based metallization remain unexplored. This work extends the TCO-free contacts by integrating the copper-plated metallization on the front side of SHJ cells.

Direct contact between silver and silicon, following the elimination of the TCO layer, fails to withstand wet-chemical processing due to weak adhesion of silver to silicon. A thin titanium layer was introduced between the silicon and silver layers to improve adhesion. In addition, direct metal deposition onto the silicon surface induced sputtering-related defects, which degrade the passivation quality of the solar cells. Thus, the effect of annealing treatment on the surface passivation is studied. Furthermore, annealing plays a crucial role in decreasing the contact resistivity on the front side, which is essential for efficient electron extraction.

In this study, an efficiency of 22.62% was achieved for front TCO-free FBC-SHJ solar cells with copper-plating metallization, attributed to an open-circuit voltage (Voc) of 720 mV and a fill factor (FF) of 80%. It was observed that Voc and FF were influenced by the annealing duration and the thickness of the hydrogenated nanocrystalline silicon oxide layer, respectively. On the other hand, efficiencies of 19.24% are attained for rear TCO-free FBC-SHJ solar cells featuring a localized-area front ITO layer with Ti/Ag back contact, respectively. Electrical characterizations revealed negligible passivation quality degradation upon front TCO localization. However, the introduction of rear Ti interlayer decreased the short-circuit current density (Jsc) due to the lower near-infrared wavelengths reflectivity of titanium compared to silver. Combining the optimized front and rear TCO-free developments yielded a completely TCO-free contact featuring front copper-plated metallization with an efficiency of 21.19%. The device demonstrated good passivation quality, evidenced by Voc exceeding 710 mV and FF above 80%. Future development may consider the feasibility of depositing anti-reflective coating on the rear side to increase the Jsc further. In addition, the stability of TCO-free devices under prolonged light exposure remains a concern, as indicated by a 7% FF relative decrease after 100 hours of continuous illumination.

Carbon fibre reinforced polymer (CFRP) composites have become integral to modern day society, forming the backbone of lightweight, high performance structures in aerospace, renewable energy and automotive applications amongst other. Their exceptional strength-to-weight ratio, stiffness and corrosion resistance in such applications make them indispensable for improving fuel efficiency, thereby contributing to lower greenhouse gas emissions. However, their end-of-life management and recycling remains a critical challenge. The thermoset polymer matrix used in most high-performance CFRP composites, makes fibre-matrix separation difficult leading to limited recyclability and continues reliance on energy- and cost- intensive virgin carbon fibre production.

Among the emerging approaches for CFRP recycling, electrochemical processes have gained attention as promising low-energy and environmentally friendly alternatives to traditional thermal or chemical processes. The electrochemical recycling of CFRP operates under mild conditions, without the need of hazardous solvents or external heating. Despite these advantages, current literature focuses predominantly on fibre recovery efficiency with limited understanding of the gaseous, liquid and solid by-products formed during such process. These by-products may significantly influence the true environmental footprint and industrial feasibility of this technique.

To address this gap, this study systematically investigated the influence of constant applied voltage (4, 6 and 8 V) on by-product generation and CFRP degradation behaviour in an alkaline saline electrolyte composed of 3wt.% NaCl and 0.01M KOH. The by-products were characterised using gas chromatography and proton nuclear magnetic resonance spectroscopy. Additionally, the pH of the electrolytes after electrolysis was monitored and surface analysis techniques were employed to evaluate the degradation mechanisms and fibre integrity.

Results revealed that higher voltages increase current density, gas evolution and epoxy degradation, but also produced greater quantities of CO2, hydrocarbons and liquid by-products, alongside visible fibre damage. Conversely, lower voltages achieved sufficient resin removal while maintaining fibre integrity and reducing emissions. Liquid-phase analysis identified ethanol, acetone and formate, whose decomposition correlated with increasing CO2 evolution at higher potentials.

Carbon dioxide (CO₂) detection is vital in various fields, such as environmental monitoring, healthcare, and industry. Metal oxides are the sensing material because of their high sensitivity and stability. However, they have limitations in detecting CO₂ as CO₂ is a chemically stable gas, which can be mitigated by post-treatment such as annealing or doping noble metals. Spark ablation, a versatile technique for synthesizing nanoparticles with controlled size and composition, was utilized in this study to produce SnO₂ nanoparticles, which were subsequently integrated into a specifically designed interdigitated electrode (IDE) structure for CO₂ sensing. The IDE configuration featured a fixed finger width of 5 μm, with the gap width ranging from 2 to 15 μm, and devices were fabricated with SnO₂ sensing areas of 1×1 cm and 1×4 cm. Noble metals such as Ag and Ru were decorated on the SnO₂ layer to enhance the catalytic activity and promote the CO₂ adsorption reaction. Surface densities of Ag and Ru under various printing conditions were analyzed using spark ablation. Based on these results, decorated SnO₂ layers were fabricated with surface coverages of 19% Ag and 12% Ru, respectively. Annealing was performed later at 450°C and 600°C, and XRD results revealed that the grain size of SnO₂ increased from 7 nm at 450°C to 12 nm at 600°C. Gas tests conducted in an N₂ atmosphere demonstrated CO₂ detection at 200°C, with a higher response observed for samples with Ru nanoparticle decoration, approximately twice that of the undecorated sample. However, no recovery was observed. Overall, samples annealed at 450°C exhibited higher responses compared to the ones annealed at 600°C. In an N₂/O₂ atmosphere, the sensor exhibited almost no response to CO₂. Further investigation revealed a response to O₂, suggesting that the low operating temperature may hinder the reaction between CO₂ and adsorbed oxygen species, failing CO₂ sensing. An anomalous p-conductive behaviour was also observed in response to O₂. Experimental results showed no correlation between device area, gap width, and sensing performance.

Over two million bone grafts are performed worldwide, each year. The preferred method is using autografts, but there are two important downsides. There is often insufficient tissue to harvest and the scar at the harvesting side is painfull for the patient. Therefore there exists a great need to improve synthetic grafts.

Traditionally, synthetic bone scaffolds are made from only one material, this can either be a (bioactive) ceramic or metal. The former has the benefit of promoting bone growth, but has insufficient mechanical properties. Metals on the other hand have no issue competing with bone in terms of mechanical properties, but they may not be biocompatible nor aid osteo-induction.

In this study direct ink writing was used to produce multimaterial Ti6Al4V and akermanite scaffolds. The goal was to combine the favourable mechanical properties of Ti6Al4V alloy with the osteo-inductive properties of akermanite. Composites of Ti6Al4V and akermanite were evaluated as well, but similar to akermanite ceramic on itself, their mechanical performance was deemed insufficient. Akermanite and Ti6Al4V was found to react and form titanium silicide and a calicum compound, presumed to be calcium oxide. A core shell scaffold was designed which uses a Ti6Al4V shell and an akermanite composite core in order to achieve both adequate mechanical and improved bioactive properties. This scaffold performed comparable to cortical bone in stiffness, and boasted superior strength.

Roller bearings are one of the most important industrial components with a large variety of challenging environmental applications. Under water-contaminated lubricant conditions, a pro- tective layer of oxide forms on the surface of the most used 100Cr6 bearing steel, which helps suppress the corrosion rate, while adding corrosion-resistant alloying elements can improve this corrosion resistance further. Recent research suggests that the Cu alloying element in high- carbon steels contains numerous carbide precipitates, which can help to form a stronger passive layer and, thus, more effective in protecting the steel against corrosion. Meanwhile, the accu- mulation of Cu as a tramp element can degrade the quality and performance of scrap-based steel. This limits the proportion of scrap that can be used in new products and may require adding ore-based steel to dilute the copper content and maintain the required properties. This study investigates the effect of incorporating copper in high-carbon bearing steel manufactured from scrap on enhancing long-term atmospheric corrosion resistance. The effective usage of this tramp element will contribute to boosting the circular economy of steel.
In this project, high-carbon bearing steel containing a high amount of Cu (0.5 wt %) was hardened using martensitic or bainitic hardening and compared with the baseline hardened steel with no excessive Cu. The microstructures of the steel were characterized by LOM, SEM (EDS), XRD and XPS to study the retention/segregation of Cu. Electrochemical corrosion tests were used to validate the prediction. Finally, LOM, SEM (EDS), XRD and XPS were utilised to characterise the corroded surfaces.

The exposure of certain carbon steels to sour environments can result in severe hydrogen induced cracking (HIC) damage in the oil and gas industry. Current mitigation techniques in this field have low reliability or are not able to provide long-term protection against such damage. Recent advancements in thermal spray technology have resulted in a promising and cost-effective solution. Improvements in particle velocity and deposition efficiency have enabled coatings to achieve higher density and uniformity. High-velocity air fuel (HVAF) thermal sprayed NiCrMoW coatings are particularly interesting due to their outstanding corrosion resistance and mechanical properties. To ensure that equipment is sufficiently protected against the harsh environment of this industry, a thick coating is desired. However, as coating thickness increases, the performance of thermal sprayed coatings is frequently affected by residual stresses and unfavourable microstructural features.

To identify this effect, three NiCrMoW coatings with thicknesses of 250, 375, and 500 \textmu m were applied with HVAF thermal spray technology on S235JR carbon steel. Samples were analyzed in order to evaluate differences in terms of microstructure, mechanical behaviour, HIC resistance, and corrosion resistance. An AK07 HVAF instrument in a controlled setting at the IOT research centre of the University of Aachen was used to ensure consistency among the coatings during the spraying process. Experiments to evaluate HIC resistance and corrosion resistance involved prolonged immersion in a sour environment, cathodic charging, open circuit potential measurements, and potentiodynamic polarization tests. Microstructural variation was examined with the use of SEM-EDS and optical microscopy. Additionally, subsurface microhardness measurements of the coating and underlying substrate were used to evaluate hardness and give an indication of the presence of residual stresses.

Findings indicate that the coatings exhibit excellent corrosion resistance. A small but noticeable decrease in resistance was however observed with increasing coating thickness. This decline can be attributed to two factors: an increase in the degree of oxidation and accumulation of residual stresses within the thicker coatings. Additionally, it is noteworthy that while the degree of oxidation and residual stresses increased with coating thickness, the porosity fraction decreased. Microstructural features in the coatings varied as a result of differences in thermal input, cooling passes and the influence of shot peening effects. Resistance to HIC of carbon steel in a sour environment was significantly improved by the application of the coatings in comparison with uncoated samples. This can be attributed to the excellent corrosion resistance, uniformity and absence of through-coating porosity in the coatings, the thickness did not have an influence. Furthermore, it was found that the galvanic interaction between the NiCrMoW coating and the S235JR carbon steel significantly accelerates the corrosion of the underlying substrate. Thicker coatings might be able to provide a greater physical defect-free barrier which can resist breaking, damage and erosion to prevent this galvanic effect.

Aluminium alloy AA2024-T3 is a lightweight and damage tolerant material, and is therefore often used in aerospace applications. However, this alloy is difficult to weld using conventional fusion welding techniques due to defects caused by the meld pool.

Friction stir welding (FSW) was developed by The Welding Institute (TWI) in 1991 in order to overcome welding difficulties associated with the conventional fusion welding of difficult to fusion weld materials such as AA2024-T3. Since then, efforts have been made to improve the process parameters. One such improvement was the development of a stationary shoulder tool, which reduces heat input by 30% and enables stronger welds with smaller heat affected zones (HAZ). However, since AA2024-T3 is susceptible to pitting corrosion, intergranular corrosion (IGC) and stress corrosion cracking (SCC), the welds need to be protected in order for any product to function in the long term. AA1050 is an often applied clad layer, which acts as a sacrificial anode with respect to the cathodic substrate. The microstructure and corresponding corrosion mechanisms are known for unwelded and FSW’d AA2024-T3, however, little research exists on the corrosion behaviour of stationary shoulder friction stir welded (SSFSW’d) bare and Alclad AA2024-T3 butt welds. Therefore, the main focus of this project is to investigate the mechanical and corrosion properties of SSFSW’d bare and Alclad AA2024-T3. This was done by performing optical microscopy, microhardness tests, open circuit potential measurements, linear polarisation resistance tests and potentiodynamic polarisation tests on the cross-sections of three weld configurations and thicknesses: 1.6 mm bare, 1.6 mm Alclad and 3.2 mm Alclad AA2024-T3 sheets. Simultaneously, tensile tests and immersion tests were also performed using dedicated tensile test and immersion specimens.

Analysis shows that the 1.6 mm bare weld is the strongest weld but also the most susceptible to pitting corrosion, compared to the Alclad welds. Cladding provides sufficient corrosion protection, even to an exposed section of the weld and when mixed into the weld. However, cladding lowers the tensile strength overall, and cladding mixed into the weld reduces the ductility of the weld compared to the bare weld. Furthermore, possible material flow issues at the root of the Alclad welds may cause voids, which lowers ductility and enables pitting at these locations. Nevertheless, even though specimens were immersed in 3.5% NaCl solution for 24 hours and small to severe pitting was visible on the specimens, the ultimate tensile strength was not affected compared to uncorroded weld specimens. However, a reduction of the maximum elongation of the bare specimen was observed after immersion. Similar to conventional FSW, the HAZ/TMAZ was the most susceptible to corrosion, due to the most active corrosion potential at this zone. Based on literature, this was deemed to be due the formation of S-phase precipitates along the grain boundaries in this zone. In all, stationary shoulder friction stir welded bare AA2024-T3 provide the best welds regarding mechanical properties, and should be protected against corrosion after welding instead of using preclad sheets, to avoid issues with the macrostructure and corresponding mechanical properties.

In this research, the effect of curing with different types of current, current densities/voltage intensity on mortar is studied. The main objective is to explore the outcomes of electric curing on the setting time of CEM-I mortar. For achieving the main objective, an electrical curing setup is designed to accommodate curing with direct current, alternating current and pulsed direct current and the conventional vicat apparatus and its test procedure are modified in order to carry out the testing while a sample is being cured with current. Additionally, the effect of passing current on material properties such as compressive strength and resistivity is also studied. The temperature development during the curing process has also been monitored in the research. The electric charge and power calculation are done, for possible current/voltage regimes. The experiments revealed that the setting time can be altered by electrical curing of CEM-I mortar. The influence of electric curing for the chosen curing period is not significant as revealed from the compressive strength testing while the development of resistivity and temperature reveals that there is a correlation between these two properties. The effect of electric power applied to a sample is reflected in the results of the setting times. In the last chapter the findings of the study are summarised and recommendations, keeping in mind the possibility of expanding research in this field of study, have been made.

Pretreatment has become a necessary process to enhance the surface chemistry and morphology of aluminium alloys before implementing subsequent corrosion protection measures, especially organic coating application. Traditionally, hexavalent-chromium-based pretreatment processes were frequently used in many industries, but hexavalent-chromium-based chemistries are now recognized as a potentially carcinogenic hazard and environmentally harmful. The development of alternative, non-toxic and eco-friendly corrosion inhibitor and pretreatment technologies has become of pivotal importance to industries as a basic license to operate and to reach a sustainable society as a whole.
In this work, sodium galactarate (NaGal) was investigated as a potential green corrosion inhibiting chemical for hexavalent-chromium-free pretreatment and to serve as a coating adhesion promoter on aluminium alloy AW3003. The pretreatment layer formation was examined at five different pHs; 3, 4, 7, 10, and 11. The surface analysis was performed by Fourier transform infrared – reflection absorption spectroscopy (FTIR-RAS), contact angle measurement and white light interferometry (WLI). Samples with pretreatment layers formed in acidic and alkaline environment showed an increase in polar energy and surface roughness, which are strongly related to the coating adhesion properties, in line with the failure stresses obtained from the pull-off adhesion tests. The corrosion resistance was evaluated through the electrochemical behavior that was measured by linear polarization resistance (LPR), potentiodynamic polarization (PP), electrochemical impedance spectroscopy (EIS) and open circuit potential (OCP) measurements. Immersion testing was performed to evaluate the pitting corrosion behavior. The pretreated sample exhibited less pitting than the reference sample, especially in an alkaline environment where aluminium alloys severely corrode due to limited protectiveness of the oxide layer. The pretreatment prevented the corrosion products from accumulating on the sample surface, limiting stain and smut layer redeposition, subsequently reducing the pitting corrosion.

Currently, as the utilization of offshore wind energy continues to increase, floating wind turbines are expected to be widely used. As the fixed system of the turbine, the safety of the mooring chain has gradually attracted the attention of researchers. Mooring chains immersed in seawater are mainly subjected to various mechanical loads and corrosion. Therefore, premature failure and frequent replacement are the main problems of mooring chain systems. In order to avoid huge losses of safety caused by structural failure, it is urgent to establish mooring integrity management, accurately identify hazards, and evaluate the service life of the mooring system. Considering the requirements of sufficient mechanical properties and economic benefits, high-strength low-alloy steel has gradually replaced low-carbon steel as the main material for mooring chains. However, there are few studies on the detailed corrosion process of mooring chain steel.
This research aims to explore the corrosion process of mooring chain steel and the influence of marine environmental factors on the corrosion process. Traditional electrochemical techniques, morphology observation and new in-situ non-destructive technique acoustic emission are used to investigate the corrosion process. The experiment includes the exploration of the corrosion process of steel under natural and accelerated conditions. Experiments on the influence of flow velocity and temperature are also included. The corrosion process of mooring chain steel is successfully explored during the monitoring process. Acoustic emission signals related to corrosion are separated. Their sources are reasonably identified. The effects of water flow velocity and temperature of the corrosion process are summarized.

Trivalent chromium (Cr(III)) is one of the most promising non-toxic replacements for hexavalent chromium (Cr(VI)) coatings in the steel packaging industry. The application of a chromium layer to packaging steel is essential for providing a protective layer on the steel packaging’s external surface area, which prevents corrosion during its use. However, the deposition process of Cr-metal from Cr(III) solution cannot produce a deposit thicker than 10 μm with sufficient corrosion and wear resistance without the application of a complexing agent. This study provides both an experimental research as an comparative computational model. Experiments are set up to analyse the effect of the formate ion HCOO(-) concentration as a complexing agent in Cr_2(SO_4)_3 electrolytes, which results are compared to the output of the used computational model. The results provide insights into the initial composition of species in plating electrolytes, which is essential for the determination of the deposition mechanism from Cr(III) electrolytes to improve the electroplating process. Ligand exchange and bonding with HCOO(-) in chromium complexes is studied with Ultraviolet-visible light (UV-VIS) spectroscopy and Attenuated Total Reflectance Fourier InfraRed spectroscopy (ATR-FTIR) at various concentrations of HCOO(-). Additionally, computational modelling is performed with Density functional theory (DFT) to predict the spontaneous character of various ligand substitutions, and simulations of spectroscopic spectra are performed as a reference to mimic the experimentally observed data. It was found that ligand exchange with HCOO(-) in Cr_2(SO_4)_3 solutions occurs spontaneously within two days at elevated temperatures at the analysed concentrations. The experimental data shows, there is a transition point in the complex formation between the ratio of [Cr(3+)]:[ HCOO(-)] is respectively [1]:[1.61] and [1]:[3.32]. This indicates that the complex formation decreases past the ratio of [Cr(3+)]:[ HCOO(-) ] = c.a.[1]:[3] and that the concentration at which the most chromium-formate complexes can be observed is within the range of [Cr(3+)]:[ HCOO(-) ] = [1]:[1.61] to [Cr(3+)]:[ HCOO(-) ]= [1]:[3.32]. The formation of chromium-formate complexes is beneficial for the deposition process, as the addition of formate increases the amount of chromium deposited on the steel surface. Furthermore, it is found that the presence of SO_4(-2), originating from the chromium salt, is beneficial for the ligand exchange of HCOO(-). Also, the bonding of formate to chromium is found to be as monodentate binding.

The presence of harmful pollutants and toxic pathogens in water is a risk to both living beings and the environment. Water treatment plays a crucial role in the removal of these contaminants through different stages of filtration. Among the existing pollutants, a family of per-and polyfluoroalkyl substances (PFAS) escapes from all treatment methods and ends up in our food, water and, finally, in our blood. Current treatment methods are not effective due to their inability to break the strong C-F bonds in PFAS. Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS) are the most widely studied PFAS due to their widespread contamination of various environmental and biological matrices. Due to the global ban of PFOA, a short-chain fluorinated compound named GenX (the ammonium salt of hexafluoropropylene oxide dimer acid) is currently used as an alternative. However, recent studies have shown that GenX has higher toxicity compared to PFOA and is more easily soluble in water, thus making it more difficult for removal. Hence, this research surveys the potential of using boron-doped diamond (BDD) anodes, which are known to have the largest potential window and high stability over time, for GenX degradation. During the electrochemical advanced oxidation process (EAOP), the highly reactive hydroxyl radicals (OH•) produced at the BDD surface break the C-F bonds to form fluoride (Fˉ) and CO2 products. Till date, very limited research is reported on the GenX degradation and they present a contradiction on the effect of sulfate radicals (SO4•ˉ), considered for their high redox potential, in the GenX degradation. In the present study, we investigate the degradation and defluorination efficiency of GenX using boron-doped diamond anodes in EAOP. This study aims to elucidate the first step in the degradation mechanism of GenX and to clarify the contradictions previously reported on the role of sulfate radicals. Experiments are performed separately with sodium sulfate and sodium perchlorate to assess the effect of SO4•ˉ. The results demonstrate that sulfate radicals are ineffective in GenX degradation due to the steric hindrance by the -CF3 branch which blocks the trajectory of SO4•ˉ for electron transfer reaction. The effects of electrolyte concentration, current density, and chloride radicals on the degradation and defluorination are investigated for the first time to provide in-depth understanding of the degradation mechanism. A possible degradation pathway is proposed by determination of the intermediate products using mass spectrometry. From the proposed pathway, it is inferred that GenX completely mineralizes to CO2 and Fˉ via formation of three intermediates. By comparing the electrochemical degradation of GenX with that of PFOA, it is observed that the presence of the -CF3 branch increases the complexity of electron transfer in the GenX degradation even though the mineralization rate is faster for GenX than for PFOA due to lesser number of intermediates. Hence, the direct electron transfer from GenX to the BDD anode is observed to be the rate-determining step in the GenX degradation. Additionally, by comparing different BDD anodes based on their material properties and surface morphology, it is observed that the presence of sp2 regions which act as active sites for effective electron transfer is necessary to initiate the GenX degradation mechanism. Electrochemical degradation of GenX using the BDD anodes has resulted in the complete mineralization to CO2 and Fˉ which supports EAOP using BDD anodes as a promising approach towards effective PFAS degradation.

For decades, developments towards a chromate-free protective system have been a crucial quest in the aerospace industry. In this search, innovation starts with a comprehensive understanding of the aircraft complex multi-material structures and the corrosion mechanisms involved. These complex structures, with aluminium the most dominant substrate, are used to optimize the strength to weight ratio, fatigue properties and operational performance in aircraft design. On the other hand, the use of multi-materials can cause an accelerated corrosion attack, called galvanic corrosion. This type of corrosion can be advantageously applied to galvanically protect a material but can also occur undesirably with serious accelerated degradation as result.

This thesis aims to increase our understanding of corrosion on AA7XXXClad alloys as stand-alone material, as well as in configurations relevant for galvanic corrosion with other metals. The understanding of these phenomena should support the definitions of new hypotheses on how these alloys can be better protected using chromate-free coating technologies. Two commonly used aluminium alloys in the aerospace industry have been investigated in this study because a selective galvanic stimulated dissolution of the cladding layer material was found after an accelerated corrosion test. This selective dissolution makes it difficult for the corrosion inhibitors to reach the exact site of corrosion propagation in the cladding layer, reducing the inhibition efficiency and allowing corrosion to propagate.

Since Zinc is the main alloying element in the substrate and cladding material, the role of Zn with respect to corrosion initiation and propagation was investigated first. Subsequently, the behaviour of clad alloys under galvanic corrosion conditions, and finally how inhibition under these conditions can be reliably assessed. This was performed by a combination of multiple electrochemical techniques and microscopic analysis. The results demonstrate that Zn plays a significant role in the dissolution of the cladding layer and may be held responsible for the selective dissolution observed. In addition, an experimental procedure was developed to measure the coupled galvanic parameters and to simulate the galvanic corrosion degradation in industrial desired timeframes. Although simulation of the phenomenon has shown to be promising with in-situ experiments, it was not fully observed. Furthermore, to test the performance of corrosion inhibitors, a procedure is developed with and without the use of coatings. In general, it can be concluded that limiting the cathodic reactions is of paramount importance to reduce the galvanic corrosion current.

Among the emerging photovoltaic (PV) technologies under development, perovskite solar cells (PSCs) stood out in the last decade as one the fastest advancing solar technology to date, reaching a power conversion efficiency of 25.5% in 2020. Perovskite (PVK) absorbers show great versatility thanks to compositional and bandgap engineering. In this MSc Thesis Project, multications mixed-halides PVK thin-films of composition CsxFA1-xPbI3-xBrx are developed. Multiple-source layer-by-layer thermal evaporation and sequential thermal evaporation/spin coating hybrid synthesis techniques are investigated because of their compatibility with non-flat substrates. As they would enable the conformal growth of PVK on the microsized pyramidal textured surface of a c-Si- based solar cell, the long-term goal is the application in a monolithic (2-T) PVK/Si tandem. PVK engineering is carried out through tuning the main processing parameters with the aim of obtaining high-quality absorber layers. The optimisation of the PVK thin-films is based on criteria such as composition, phase, bandgap, crystallinity, homogeneity, uniformity and charge carrier transport properties. After optimising the annealing thermal treatment, the homogeneous and uniform thin-films resulting from the thermal evaporation of CsBr, PbI2 and FAI show a highly crystalline photoactive α phase of PVK, as well as a sharp-edge absorption onset corresponding to a bandgap (Eg) of Eg=1.60 eV and high absorption coefficient (α) in the order of α=10^4-10^5 cm^-1. Then, the two-step spin coating technique is explored as a preliminary study to develop the hybrid method, with the aim of analysing the surface wettability and reactivity of an inorganic layer of PVK inorganic precursors (CsBr and PbI2) when an organic solution (FAI in IPA) is spun on it. In spite of the optimisation of the FAI solution spun volume and concentration and the annealing parameters, the spin-coated thin-films present a mixture of photoactive and non-photoactive phases, i.e. PbI2-xBrx and α-, γ- and δ-PVK phases. The ineffective interdiffusion reaction leading to inhomogeneous and non-uniform PVK thin-films shows that the processing parameters need further fine-tuning. However, as spin coating does not allow to deposit PVK on top of non-flat substrates, the thermal evaporation/spin coating hybrid method is developed. The solution of FAI in IPA has been spun on a thermally evaporated inorganic bilayer of CsBr/PbI2. Albeit incomplete conversion to PVK is under suspicion, the resulting α-PVK thin-film shows good crystallinity and homogeneity and acceptable uniformity. It also presents high absorption (A=70%) for λ<500 nm (blue light) and low absorption for λ>500 nm (from green to red light), although the bandgap of Eg=1.53 eV needs to be further optimised by adjusting the content of Cs+ and most importantly Br–. On top of that, for all the synthesis techniques under research some unsuccessfully deposited PVK thin-films show signs of thermal and atmospheric degradation, leading to the decomposition of the α phase of PVK and formation of PbI2 and other non-photoactive phases, along with poor optical properties. Such degradation phenomena, which might be ascribed to the ineffective incorporation of Cs+ leading to structural instabilities, highlights the difficulties and limitations of PVK engineering.

Literature reports a great deal of contradictory results concerning the effect of microstructure on the corrosion and passivity behaviour of advanced high strength steels. The difficulty in identifying the controlling cause of corrosion results from the inability of disentangling the coupled effects of individual microstructural features in a scientifically rigorous manner, thereby attributing the core behaviour to the wrong sources.
The aim of this thesis is to isolate and identify the effect of phases on the electrochemical response of high strength steels. To this end, a combined computational and experimental approach is taken. This work starts by analysing the connection between heat treatment, microstructure, and the resulting corrosion properties. After clarification of this interdependence, a finite element electrochemical model illuminates the corrosion behaviour of idealised two phase ferrite-martensite and ferrite-pearlite systems for different phase volume fraction combinations. The results from the simulations guide the microstructure creation for electrochemical experiments, where employed heat treatments result in ferrite-martensite and ferrite-pearlite microstructures with similar ferrite volume fractions. Potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) experiments in 0.1M and 0.01M H₂SO₄ solutions; potentiostatic polarisation, EIS and Mott-Schottky analysis in 0.1M NaOH solutions reveal the corrosion response and passive film barrier properties of the microstructures. Results demonstrate a clear phase dependency for both active and passive conditions, and are further discussed in light of microstructural features of secondary martensite and pearlite phases.

Due to their simple structure and the possibility for in situ doping, light emitting electrochemical cells (LECs) are shaping up to be a cheap and easily produced alternative to LEDs. To date, little research has been done to combine the luminescent properties of colloidal quantum dots (QDs) with the LEC concept. In this thesis, steps are taken towards developing a QD-based LEC. The LECs were produced based on the semiconducting polymer MEH-PPV, ZnO and CdSe/CdS/ZnS quantum dots. Furthermore, drift-diffusion simulations were performed to discover general trends in LECs. MEH-PPV devices performed as expected. ZnO QDs were found to be unsuitable for LECs due to their high intrinsic conductivity and low luminescence efficiency, while CdSe/CdS/ZnS QDs were identified as promising candidates. Results from the drift-diffusion simulations suggested that unlike in LEDs, the type of electrode material has little effect on device operation. Charge carrier mobility was identified as the limiting parameter for luminescence intensity. It is thus suggested that improving carrier mobility in QD films is the most important step towards QD-based LECs.

Rapid industrialization and use of carbon based fuels has caused a drastic increase in the atmospheric CO₂ levels in the last few decades. The rising anthropogenic CO₂ levels pose a significant threat to the environment as evidenced by the increase in the mean global temperature levels, and the rising ocean levels. To mitigate the challenges associated with rising CO₂ levels, there is an urgent need to move towards carbon neutral sources of energy and to curb carbon emission from large scale point emitters such as industries. Additionally, emitted CO₂ could be converted into energy dense organic fuels using carbon-neutral forms of energy. This not only helps in reducing the carbon emissions but also balances the intermittent nature of renewable energy supply. CO₂ could also be converted into platform chemicals such as ethylene/CO, which can be further up-converted or directly used in industry. Ethylene is particularly interesting due to its high
energy density and wide industrial usage as a precursor in the polymer industry. Electroreduction of CO₂ provides one such approach to electrochemically convert CO₂ produced at large scale emitters to useful organic compounds. Different metallic catalysts are known to catalyse the electrochemical reduction towards different products, which follows from Sabatier’s principle. In this study copper is used as the model catalyst due to its unique ability to electrochemically convert CO₂ to multi-carbon products, such as ethylene. From a cell design perspective conventional electrochemical reduction of CO₂ in aq. media suffers from low production rates due to the low solubility of CO₂ in aq. electrolytes which makes it not feasible from an industrial standpoint. To overcome the low production rates, this study was carried out on novel gas diffusion electrodes. Another factor limiting the implementation of CO₂ electrolysers on an industrial scale, is the scalability of the catalyst synthesis. To improve this, electrodeposition of copper catalysts was employed. Electrodeposition is a well-established industrial technique and integrable within the existing infrastructure. Electrodeposition facilitates in-situ growth of the catalyst on gas diffusion layers, thereby providing a facile alternative to the conventional multi-step process for catalyst synthesis. Different morphologies of copper were synthesized by varying the electrodeposition process parameters. Copper nanowires were also synthesized by using templated electro-deposition techniques. The catalysts were characterised before and after the CO₂ reduction experiments by Scanning ElectronMicroscopy, and X- Ray Diffraction. CO₂ reduction experiments using the synthesised copper catalysts were carried out over a range of potentials. A peak Faradaic Efficiency (FE%) of 15% was measured at -1.5 V vs RHE (uncompensated) for ethylene, 19% FE at -1.1 V vs RHE for formic acid, and 13% FE at -1.5 V vs RHE for methane. It was also seen that the catalyst suffered from stability issues which were overcome by using pulsed electrolysis. Using pulsed electrolysis the lifetime of the catalyst was increased from 30 minutes to 15 hours.

Microstructure-corrosion property correlation is an open question in the field of materials science. The microstructure of metals and alloys consists of several features with different individual corrosion response. The corrosion behavior of the macroscopic system is an outcome of the complex interaction of the components of microstructure. Hence, a definitive understanding of the corrosion response of the microstructural features is needed for improving the material durability and design.In the present work, the effect of grain size  on the active corrosion behavior of pure iron is investigated. Samples with different grain sizes are obtained by annealing heat-treatment. The microstructure of samples is characterized by optical microscopy, electron backscatter diffraction and X-ray diffraction. Electrochemical characterization using potentiodynamic polarization and electrochemical impedance spectroscopy are performed on the samples in deaerated 0.1 M and 0.01 M H₂SO₄ solutions. The surface topography of the corroded sample surface is characterized by atomic force microscopy. Following the experiments, a numerical corrosion model is attempted to replicate the observations. The results reveal an aggregate effect of grain size and crystallographic orientation of grains on the corrosion behavior of the samples.