The rapid advancement in electronics, driven by intricate circuit design and manufacturing miniaturisation, has enabled the development of compact devices used in a wide range of applications. To ensure the performance and reliability of these sophisticated devices, it is crucial to study corrosion behaviour and performance at micro- and nanoscale levels. Traditional methods often fall short in addressing these challenges, highlighting the need for advanced localised techniques to understand corrosion mechanisms and develop strategies that ensure the durability of these critical devices in harsh conditions. This thesis investigates the localised aqueous corrosion study of Electroless Nickel Immersion Gold (ENIG) final finishing on copper substrates, which are widely used in printed circuit boards (PCBs) for electronic applications. Through a series of experimental studies, the research explores how micro-defects, phosphorus content, and bath parameters influence the corrosion resistance of ENIG and electroless nickel-phosphorus (NiP) coatings. Utilising advanced electrochemical and surface analysis techniques, the findings provide valuable insights into optimising coating processes to enhance the reliability and longevity of electronic components in harsh environments... ... Read more

Atmospheric corrosion is a major challenge for infrastructure and industry, yet predicting corrosion under realistic environmental conditions remains difficult. Existing empirical and machine-learning approaches typically relate environmental conditions directly to corrosion outcomes without capturing the electrolyte layer that physically mediates the corrosion process. This thesis develops an end-to-end experimental and computational framework to link the dynamics of realistic multi-droplet electrolytes to macroscopic corrosion kinetics.
-A custom climate chamber and electrical resistance sensor system were developed to continuously monitor corrosion under discontinuous, droplet-based conditions.
-An automated computer vision pipeline was developed to track droplet geometry and corrosion product formation across thousands of individual droplets.
-Larger droplets showed earlier onset and faster corrosion, with two distinct spatial patterns of attack identified and quantified.
-A weakly supervised machine learning framework was developed to infer individual droplet corrosion kinetics from the global sensor signal without requiring droplet-level ground-truth labels.
-Surface roughness was shown to influence corrosion by promoting larger, more elongated droplets through enhanced pinning and coalescence.
Together, these results establish a framework for making the electrolyte population visible, measurable, and directly linkable to atmospheric corrosion kinetics. ... Read more

In the petroleum industry, acidic corrosion is a frequent challenge, particularly in environments containing hydrogen sulfide (H₂S), where it accounts for approximately 18% of total failures. Among various forms of acidic corrosion, hydrogen-induced cracking (HIC) is most common in oil pipelines constructed from plate materials, leading to a decline in mechanical performance. Previous studies have shown that Hastelloy C276 coatings prepared by high velocity air fuel (HVAF) spraying can effectively prevent HIC. However, due to issues of high cost and coating porosity, extending the service life of HVAF sprayed Hastelloy C276 remains an open question. This study explores a sol-gel sealing strategy using SiO₂/ZrO₂ as the sealing material. HVAF Hastelloy C276 coated samples without sol–gel sealing served as the control group, while samples sealed with two and five layers formed the experimental groups. All samples were tested for mechanical strength, corrosion resistance, and HIC resistance. The results of these properties were compared to evaluate whether sol-gel sealing improves durability and how the number of layers influences coating performance. ... Read more

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The global transition to sustainable energy has accelerated the demand for hydrogen as a
clean fuel source. Carbon steel pipelines play a vital role in hydrogen transport and storage infrastructure, but their potential susceptibility to hydrogen embrittlement poses a significant challenge.
Hydrogen ingress, facilitated by environmental and operational factors, undermines the
structural integrity of these steel pipelines, making it critical to develop strategies to mitigate
hydrogen-induced degradation. The formation of internal surface oxide layers on these steels
significantly influences hydrogen-material interaction processes, underscoring the need for
further investigation and understanding, a focus of this study.
This study focuses on a naturally formed oxide layer on pipeline steel API 5L X65 and its role in
influencing hydrogen permeation behaviour. Using characterization techniques including optical microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Raman spectroscopy, the composition and thickness of the oxide layer were studied.
Electrochemical hydrogen permeation experiments using the Devanathan–Stachurski (D-S)
cell were performed on bare steel samples (with oxide removed from the surface) and oxide-covered steel samples. The results showed a significant delay in hydrogen permeation in the
case of oxide-covered steel. An estimation of the hydrogen diffusion coefficient (D_eff) was
carried out, showing significantly lower values for oxide-covered steel (5.57×10⁻¹⁰ cm²/s and
7.13 × 10⁻¹¹ cm²/s) compared to bare steel (3.46 × 10⁻⁶ cm²/s).
Electrochemical analysis by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) of the surface before and after hydrogen charging revealed a significant degradation of the barrier properties of the oxide after charging. Further optimization of the experimental conditions during the D-S method will be necessary to verify that the oxide integrity is solely affected by hydrogen ingress and not by the potential or current applied during charging.
This research provides a better understanding of the properties of naturally formed oxide layers on pipeline steel and their role in mitigating hydrogen permeation. These insights contribute to a deeper understanding of the role of oxide layers in the hydrogen transportation steel infrastructure.
Recognizing the significance of these interactions is crucial for developing accurate
testing and qualification protocols to ensure the reliability and performance of these materials in hydrogen transport applications. ... Read more

An effective way for the automotive industry to tackle the growing concern of increasing CO2 emissions is to reduce the vehicle's overall weight, without compromising its performance and passenger safety. With the increasing demand for steels with enhanced properties in the last decades, the development of advanced high-strength steels (AHSSs) has been focused on the design of complex microstructures, leading to exceptional combinations of strength and ductility. On the other hand, stainless steels also offer significant potential in automotive lightweight applications to complement carbon steel AHSS grades. Stainless steels can offer additional advantages, including better corrosion resistance (no need for galvanising) and increased strength and fatigue resistance. However, a significant barrier to their application is the alloying cost (nickel in austenitic stainless steels) or low ductility and formability (standard martensitic stainless steels).... ... Read more

With the depletion of energy resources and escalating environmental issues, the development of new energy sources and advanced energy storage devices has become increasingly critical. Zinc-ion batteries have attracted significant attention due to their lower cost and safer chemistry. A major focus of zinc-ion battery research is the development of zinc anodes and electrolyte design. Zinc-free anodes have emerged as a promising strategy, offering higher zinc utilization compared to traditional zinc metal anodes (approximately 10%). Among many zinc-free anodes, Ti₃C₂Tx, a MXene (transition metal nitride/carbide layered material), stands out due to its lower lattice mismatch (~10%), higher conductivity, superior mechanical properties, and good hydrophilicity. However, the higher zinc utilization of zinc-free anodes presents challenges for the stable plating/stripping of zinc. Co-solvent engineering is a convenient and direct approach to improving the stability of zinc-free anodes.

In this study, we propose the use of PEG and IPA as co-solvents added to a 1M Zn(OTF)₂-H₂O electrolyte to enhance the stability of Ti₃C₂Tx zinc-free anodes. We found that the addition of PEG reduced the hydrogen evolution current by 0.42 mA (at -1.3 V vs. Ag wire), indicating suppression of the hydrogen evolution reaction. Furthermore, the addition of PEG in the electrolyte inhibits the 2D diffusion of zinc on the Ti₃C₂ surface and promotes zinc deposition along the (002) crystal direction, increasing the (002)/(001) ratio from 0.59 to 0.86, leading to more uniform zinc deposition. Consequently, the Ti₃C₂ zinc-free anode achieved a coulombic efficiency of 97.67% and a cycle life of 268 hours. Similarly, the addition of IPA reduced the hydrogen evolution current by 0.39 mA (at -1.3 V vs. Ag wire), indicating a weaker hydrogen evolution reaction. Moreover, the addition of IPA in the electrolyte inhibits 2D diffusion on the Ti₃C₂ surface and facilitates zinc deposition along the (002) crystal direction, increasing the (002)/(001) ratio from 0.59 to 0.87. The formation of an SEI containing ZnCO₃, ZnFx, and F-rich organics helps to homogenize the Zn ion gradient. Ultimately, the Ti₃C₂ zinc- free anode achieved a high coulombic efficiency of 98.95% and a cycle life of over 1200 hours in the IPA-containing electrolyte. ... Read more

Nanomechanical tests to investigate Diamond-Like Carbon (DLC) coating abrasive wear behavior were carried out under different load and strain rate conditions. Nanomechanical tests performed include nanoindentation, single and multi-asperity scratching tests. Characterization methods used are confocal optical microscopy, SEM/EDS, and (high-resolution) AFM. The counterpart material used is diamond.
Results show that DLC abrasive wear behavior is predominantly plowing. Increasing normal load results in wear debris at the edge and inside the wear scar. Failure occurs between DLC and substrate (in this case SiC), upon further increasing the normal load which is in agreement with the literature. In addition, it is found that strain rate influences DLC wear behavior with increasing normal load. This implies that DLC/SiC interfacial adhesion strength presents strain rate dependency rather than DLC itself. This is supported by nanoindentation measurements, where no strain rate dependency was observed. Therefore, for a DLC coating operating under high loading (≥100mN per asperity) in an engineering application, single-asperity testing is not representative of the engineering application. This is caused by the limitations of single-asperity test setup reaching strain rates close to that of the engineering application.
Further, it is reported that in multi-asperity scratching tests increasing the normal load affected the scratch density rather than scratch depth and width. This implies that there is a range of macroscopic normal loads that corresponds to similar single-asperity wear behavior. Scratching tests performed at the edge of DLC/SiC wafers showed that edge wear depends on the rate of change of asperity interference (ω ̇) during collision with the edge. Moreover, an analytical model was developed which predicts that minimization of the impact force (and thus wear) is accomplished when ω ̈ takes minimum value. Based on this criterion minimized edge wear takes place when the asperities are relatively sharp (~1μm) and their initial interference does not exceed 30% of the coating thickness.
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The transition to methanol as a promising alternative fuel for maritime applications, presents unique design and material challenges, particularly in retrofitting existing integrated aluminum tanks for methanol storage. Methanol’s toxicity, flammability, and corrosive nature, particularly with respect to aluminum alloys, complicate this process. This research adopts a multi-disciplinary approach, integrating ship design and material science to address these challenges. A complete analysis of regulatory frameworks and material compatibility was conducted to explore viable solutions for converting integrated aluminum tanks, with a focus on incorporating an inner barrier that ensures both compliance with classification societies and the optimization of net volume.

Key methods used in this research include Multi-Criteria Decision-Making (MCDM) analysis and static immersion followed by tensile tests experiments. The MCDM was conducted to ascertain the most viable inner barrier solution for retrofitting integra. ... Read more

This study aims to assess the suitability of iron oxyfluoride (FeOF) as cathode material for fluoride-ion batteries based on the electrochemical performance and fluorination capability of ferrous oxide (FeO), as well as the defluorination of FeOF. Due to the pressing demand for electrochemical storage, alternatives to the widespread lithium-ion battery must be sought. One alternative can be the fluoride-ion battery (FIB). By trying to combine the stability of intercalation-based electrode materials and the high energy density of conversion-based materials, oxyfluorides might be the answer, especially if based on an abundant transition metal such as iron. In this report, the suitability of iron oxyfluoride as cathode material was evaluated. This was done by synthesising the electrode composites, evaluating their performance in a custom-made electrochemical cell and investigating the phase transitions of the researched materials. It was found that the ferrous oxide could not be fluorinated in an electrochemical environment and only reached a capacity of 0.75 mAh/g, which is equal to 0.2% of the theoretical capacity. It was also found that the iron oxyfluoride could not be electrochemically defluorinated. Therefore it is concluded that iron oxyfluoride is not suitable as cathode material for fluoride ion batteries. ... Read more

The corrosion of bearing steel often leads to accelerated damage and loss of properties that condition their service life. This damage is further exacerbated with the absorption of hydrogen into the material, generated from corrosion reactions happening at the surface. A remanufacturing process is proposed to recover the operating capabilities of bearings after exposure to corrosive environments, during which the bearings are polished until the surface is visually clean, out of any corrosion product. The process offers the recoverability of the operating capabilities and turns the corroded bearings into a reconditioned useful part avoiding the operational effort, economic cost, and repair that the replacement of a bearing entails. However, atomic hydrogen in the bulk can be entrapped and might still condition bearings operation, often resulting in hydrogen enhanced damage in the steel.

The goal of the current research is to quantify the hydrogen uptake and critically evaluate the reapplication of such remanufactured bearings. The study analyses a bearing that experienced corrosion during its operation in the pulp and paper industry (P&P), primarily due to the cooling water used in the machines. For a better understanding of the effects of the operating environment on bearings, extreme corrosive environments were simulated in a climate corrosion chamber (CCC). The absorbed bulk hydrogen is quantified through the Melt Extraction Tester (MET), and the trapping behaviour analysed through Thermal Desorption Spectrometry (TDS). The effect of the environmental conditions is studied through a microscopical characterization of the formed corrosion product. Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), and X-ray Photoelectron Spectroscopy (XPS) are the laboratory equipment used for this purpose.

It was found that the remanufacturing did not ensure meeting the acceptable hydrogen content limit in extreme environments, suggesting that the polishing process is often not sufficient, and should be adapted to specific operating conditions. However, due to material inhomogeneities such as surface pits and plastic deformation-induced traps, no clear correlation could be established between polished material and bulk hydrogen. Nonetheless, a smooth polished surface was proven to minimize the presence of microreaction sites and subsurface defects, thus reducing the absorbed hydrogen. Additionally, corrosive media also affect hydrogen behaviour in the material. In the present work the trapped hydrogen concentration is seen to be dominant, reducing the risk of hydrogen damage. However, reversibly trapped, and diffusible hydrogen is also detected, and can be desorbed or redistributed into other trapping sites during the corrosion process.
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The reliability of battery performance is crucial for the implementation of long-term large-scale energy storage. The promising Iron-Air battery is known for its suitable properties relying on its advantageous iron-based anode, characterized by its high volumetric energy density, robustness, material abundance, low cost and scalability. The anode does however present drawbacks, such as self-discharge, hydrogen evolution reaction (HER) and initial- and gradual surface passivation. In previous studies the effect of porosity and specific additives have been presented as important factors in tackling these drawbacks. This multidisciplinary research aimed to study porosity and additive effects on the electrochemical behaviour and performance of iron-based mechanically-stable anodes, manufactured at elevated temperature and pressure. Specifically, the effect of 10wt% pore former K2CO3 on the initial capacity and on the passivation behaviour was studied by galvanostatic charge-discharge, with prior investigation on pore formation. In addition, the effect of high-performance additives (Bi2S3, Bi2O3, ZnS and FeS) was investigated on HER kinetics and the passivation behaviour, by cyclic voltammetry (CV) and galvanostatic cycling, respectively. Surface characterization was performed by optical microscopy, scanning
electron microscopy (SEM), and profilometry. Post-test analysis was carried out by optical microscopy and X-ray Photoelectron Spectroscopy (XPS). An intensification of surface cracks was observed for the K2CO3-rich sample before testing and its initial discharge capacity is 27 mAh/g less than a sample without pore former, but passivated later than the pristine sample in the full cell. Amongst the additives, the highest cycle of 100% capacity retention was marked at cycle 41 for FeS and for Bi2S3 at cycle 29 in the full cell, both showing 100% retention in the half cell up to 36 cycles. FeS might benefit from its readily available soluble reservoir of S2− ions. Bi2O3 showed the lowest capacity retention which might be explained by low conductivity, low solubility and/or lack of beneficial role of S2− ions. However, the additive Bi2O3 showed great reversibility of discharge products in the CV, confirmed by the lower O1s peaks and the lower respective Fe2O3 and FeOOH peak in XPS spectra. The pristine sample showed in the CV over the cycles increased current density and slope near the HER potential, with low reversibility. Apart from Bi2O3 and ZnS, the pristine sample showed lower capacity retention than FeS and Bi2S3, confirming the effective working of these additives. This systematic study portrays a good starting point for further studying porosity and additive effects on the electrochemical behaviour in hot-pressed anodes for the upcoming Iron-Air battery. Improvements can be assigned to cell design, electrolyte control and further detailed porosity characterization. Another type of current collector
might withstand higher current densities and anode thickness reduction can lead to higher discharge capacities over its lifespan. ... Read more

Pursuing sustainable and efficient energy storage technologies has led to advancements in iron-air batteries. Understanding the intricate relationship between the microstructural features of iron electrodes and their oxidation and reduction behaviour is crucial for optimizing battery performance and lifespan. This thesis aims to investigate the impact of microstructural characteristics, such as phases, grain size, and defect density, on the formation of stable iron oxide/hydroxide compounds and the evolution of hydrogen gas (HER), using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) experiments in 6M KOH. The influence of an electrolyte additive, sodium stannate trihydrate, and an iron foam functioning as alternative electrode material are also examined.
Hot-rolled, pure iron samples were subjected to annealing heat treatments, resulting in different grain-sized specimens. A dual-phase steel, DP1000 steel composed of ferrite and martensite phases as well as hot-rolled and cold-rolled iron electrodes, completed the materials that formed this study’s basis. Initial surface identification via optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), atomic force microscopy (AFM) and X-ray diffraction (XRD) have been performed.
Results indicate a relatively lower formation of FeOOH for a DP1000 steel anode compared to cold-rolled alpha iron over 12 cycles. A marginally larger decline in HER kinetics is observed for a hot-rolled small grained anode compared to a coarse grained anode, while a clear effect of grain size on the development of Fe₃O₄ and FeOOH could not be established. An iron foam electrode showcases greatly enhanced anodic and cathodic current densities in comparison to solid sheet iron electrodes, due to its cellular structure. The effect of 0.01M sodium stannate added to the electrolyte illustrates a significant reduction in HER intensity for both foam and solid iron samples.
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Many applications requiring light weight, good strength, and corrosion resistance use 5xxx and 6xxx series aluminium alloys. One such application is cooling channels in ASML cooling systems, where AA5083 and AA6082 Cu-free alloys are employed to carry the flow of semiconductor-grade ultra-pure water. Due to several reasons, even under ultra-pure water conditions, corrosion of aluminium channels is unavoidable. Localised corrosion due to the galvanic coupling formed between the intermetallic phase and the aluminium matrix is known to be the reason behind corrosion initiation and propagation. However, the behaviour and role of different types of intermetallic phases are not completely understood.

This study attempts to better understand the role of intermetallic phases in the corrosion initiation of AA5083 and AA6082 alloys. For this purpose, localised techniques are employed to evaluate the electrochemical properties of intermetallic phases and to study the activity of the sample surface through SKPFM and in-situ SECM experiments, respectively. The study also performs potentiodynamic polarisation tests to understand the overall corrosion performance of the alloys in ultra-pure water, an artificial mixture of impure water, and a 0.1 M NaCl solution.

In addition, regarding the electrochemical behaviour of the intermetallic phases, it is found that the alloy composition and the surface distribution of the intermetallic phases also contribute to and have a significant effect on localised corrosion initiation. The results of the localised techniques carried out using a 0.1 M NaCl solution agree with the observations obtained for ultra-pure water and the artificial mixture conditions. ... Read more

Studies on the impact of Hydrogen on the electrochemical and mechanical behaviour of Iron-based materials have been increasingly conducted in the past few years. This is mainly due to the ever-growing demand for sustainable energy sources, which involve Hydrogen and to meet the high structural and economic demands from the automobile sector and other industrial demands for which high strength steels like dual-phase steels have been developed. Steels may absorb hydrogen both throughout the production process and during different phases of use. High-strength steels (particularly dual phase steels) and martensitic stainless steels are highly susceptible to hydrogen embrittlement. Moreover, hydrogen embrittlement is already possible at quantities as low as 0.1 ppm[1]. Therefore, understanding Metal-hydrogen interactions is essential.

This thesis aims to study the effect of Hydrogen charging on three different
iron-based materials and the possible effect on the electrochemical/corrosion performance. The Iron-based materials used in the study are Pure Iron, DP1000 and AISI 420. The methodology involves using an electrochemical procedure based on potentiostatic Hydrogen charging and Cyclic Voltammetry (CV), applied on these Iron-based materials having different phases to monitor H-uptake in the materials. The materials are charged with Hydrogen both on the active and passive surfaces. The electrochemical method is capable of measuring the diffusible H concentration (including mobile Hydrogen) for the steel alloys under H-charging conditions. Using X-Ray Diffraction (XRD) Technique, microstructural analysis is carried out on Pure Iron, DP1000 and AISI 420 stainless steel to identify the different phases interacting with Hydrogen. To gain additional insights relating to the electrochemical/corrosion performance of the investigated materials and into the H-related findings, potentiostatic polarization techniques, Electrochemical Impedance Spectroscopy (EIS) and Scanning Kelvin Probe (SKP) are carried out.

As a result, it was discovered that Pure Iron had the maximum amount of diffusible Hydrogen under the charging conditions tested, followed by DP1000 and then AISI 420 Steel with the lowest amount. EIS technique was useful in identifying a trend between the barrier properties of the passive layer and the H desorption values for the three materials. The results also revealed that materials charged with Hydrogen on active and passive surfaces behaved differently with respect to the amount of Hydrogen desorption. The microstructural features of the active surface and the passive oxide film that formed on the materials are further discussed in relation to this. ... Read more

Atmospheric corrosion is one of the most widespread types of metal corrosion in the world. Commonly, atmospheric corrosion is affected by the electrochemical properties of the metal and environmental factors, such as humidity, temperature and the properties of the electrolyte on the metal surface. Currently, there still lack of laboratory studies which investigated the effect of changing electrolyte thickness on corrosion behaviours. In this study, a corrosion cell with adjustable electrolyte thickness was used to simulate the atmospheric corrosion process of carbon steel and zinc under thin-film sodium chloride electrolyte conditions. The effects of electrolyte thickness and chloride ion concentration on the atmospheric corrosion of these two metals were investigated by open circuit potential, polarization and galvanic coupling techniques. To perform the experiments under thin-film conditions a novel electrochemical cell was employed. Experiments confirmed the effect of electrolyte thickness on the corrosion rate of the metals. Particularly, it was established the role of oxygen transport in the kinetics of the process. At large electrolyte thickness (several hundred micrometers), oxygen is limited at the proximities of the metal, leading to corrosion rates comparable to the values under bulk electrolyte conditions. With the reduction of the electrolyte thickness, a higher concentration of oxygen is available, due to the faster oxygen equilibrium between air-electrolyte, leading to a substantial increase in both corrosion rate and the diffusion control limiting current. Corrosion current density under approximately 40μm thin-film electrolytes were two orders of magnitude higher than the currents measured for both carbon steel and zinc metals under immersed conditions (bulk electrolyte). The effect of chloride ion concentration on corrosion rate under thin-film electrolytes was also revealed. The higher solubility of oxygen on low chloride-concentration electrolytes showed also an acceleration of the process. Carbon steel and zinc metals presented the highest corrosion rates under 0.01M NaCl electrolyte with 40μm thickness. ... Read more

Microchips are made from circular silicon discs called wafers and are manufactured with photolithography. A critical step of a photolithography process is when a wafer with a photoresist is placed on a wafer table (WT) and exposed to light to form patterns that build up components of an integrated circuit (IC). The dimensions of the IC are in nanometer scale and are becoming increasingly smaller. Any changes to the wafer table can contribute to alignment issues or increase overlay between successive exposures and is dependent on interaction with the wafer backside.
Common wafer backside materials are silicon, silicon oxide and silicon nitride, which are hydrophilic, so they readily interact with water and adsorb it from the atmosphere. Furthermore, their surface conductivity is highly dependent on the relative humidity (RH) of the air. Additionally, silicon oxide and silicon nitride generate surface charge from single-wafer wet spin tools that are a part of the critical toolset for advanced IC fabrication.
In the presence of water, a charged wafer backside can conduct unwanted current through the surface. The occurrence of this phenomena can affect both the performance and yield of the components that the wafer backside comes in contact with during photolithography.
This thesis studies reducing the charge generation and surface conductivity of a hydrophilic silicon and silicon nitride wafer backside by depositing hydrophobic self-assembled monolayers (SAM) with silane coupling agents. They are less likely to form surface charge and have lower surface conductivity. The hydrophobic monolayers that are studied are deposited from hexamethyldisilazane (HMDS) and a non-disclosed fluorinated molecule, called F-SAM. HMDS is already used in photolithography on the wafer frontside to promote adhesion to the photoresist and fluorinated molecules are known to be hydrophobic, inert and with high electrical resistance.
This surface modification tackles both the water content on the surface and the charging via single wafer wet-spin tools. The monolayers are characterized in terms of surface chemistry, surface free energy, wear resistance, zeta potential, surface charge and conductivity. Lastly, the charge diffusion is measured when a wafer is put in contact with a wafer table in an experimental setup, where the discharge current is registered.
The outcome of this study shows that modified surfaces are found to be homogenous to a sub nanometer level and uniform. Compared to typical silicon nitride wafers, the surface conductivity is lowered by a factor of 1000 and is not affected by the RH. This results in the total measured charge diffused to a wafer table to be reduced by at least a factor of 17. As a conclusion, modified surface can be considered a promising option in reducing any unwanted current leakage from a wafer backside to surrounding components. ... Read more

Epoxy resins are one of the most relevant and widely used thermosets in the market covering a wide range of applications. Industries are being forced to quickly transition towards sustainable alternatives due to the pressure from emerging environmental concerns, the depletion of petrochemical supplies, and compliance with environmental legislation. Since the primary component of epoxy resins is derived from petroleum (Bisphenol A (BPA)), companies like Westlake Epoxy have joined the search for innovative, environmentally friendly solutions. Many bio-based substitutes have surfaced in recent years, in efforts to eliminate or reduce the quantity of BPA in epoxy resins. Attention has been focused on lignin biomass as a viable feedstock in the manufacturing of these thermosets because of its large production volume and some structural characteristics.

This study addresses the synthesis of novel lignin-based epoxy resins and the evaluation of their potential application in the field of coatings and composites. For this research, different sources of technical Kraft lignin were employed. Since technical lignin is not very reactive due to the large molecular weight polymers, a Confidential Fractionation process has been developed. For its synthesis, both small- and large-scale glycidation processes were successfully implemented. To understand the chemical structure of lignin and its corresponding resins, different analytical techniques were used such as Gas Chromatography (GC), titrations, Nuclear Magnetic Resonance (NMR), Fourier-Transform Infrared Spectroscopy (FT-IR) and Gel Permeation Chromatography (GPC). Additionally, for the development and characterisation of coatings and composites, a variety of material testing techniques were employed, namely Differential Scanning Calorimetry (DSC), Dynamical Mechanical Analysis (DMA), Thermogravimetric Analysis (TGA), Interlaminar Shear strength (ILSS), Impact testing, Pendulum hardness, among many others.

Experimental results showed an average fractionation yield of 50-60% of technical Kraft lignin using the Confidential Fractionation process. Compositional differences in the fractionated lignin substrates studied via NMR analysis, predict some differences in the reactivity of these substrates towards glycidation, which is supported by different Epoxy Group Content (EGC) of the corresponding epoxy resins. The EGC of the lignin-based epoxy resin is significantly lower than that of the reference resin due to the presence of bulky moieties that hinder the reactivity of active sites. While lignin-based coatings exhibit comparable performance in hardness and direct impact resistance, however, its high viscosity and stiffness results detrimental in other areas. On the other hand, this high viscosity is a major challenge in the processes of prepreg laminates leading to poor adhesion of the fibres to the matrix, which has a negative effect when it comes to mechanical performance. However, adding lignin to epoxy resins has proved to improve the thermal stability of these materials.
... Read more

Excess CO2 in the atmosphere has been a troublesome problem for humanity for the last few decades now. Academics, governments and industries are working together to tackle this problem to avert a global warming disaster. Research on many technologies is in progress to tackle global warming, with carbon capture being one exciting solution. The process of converting this captured carbon dioxide into something useful has gained momentum in research and academia since the 1980s. Out of the many catalysts worked upon to convert the excess CO2, copper has gained particular limelight because of its exceptional ability to reduce CO2 into valuable products such as methane, formic acid, ethane, methanol, to name a few.

The literature study associated with this project identified a knowledge gap between the present literature and the understanding of the microstructural impact on CO2 reduction. The thesis project studied the effect of microstructure changes on the electrochemical properties of copper and its subsequent impact on CO2 reduction capabilities to bridge the knowledge gap. Sigma- Aldrich copper of purity 99.999% was selected for this thesis work, and four samples: as received, electropolished, and two annealed samples were prepared. Optical microscopy and XRD measurements were used for microstructural characterization, and it was found that annealed samples lost their rolling direction, and their grain sizes increased. Evaluation of electrochemical behaviour through CV and EIS results indicated the formation of a complex triple passivation layer on the copper samples. Through evaluation of EIS results, we found that the electropolished sample had the most robust Cu2O layer.

From the CO2 reduction experiments, it was found that as-received samples had the highest F.E. for CO2 reduction, and non-electropolished samples had a high F.E. for hydrogen production. The performance of the electropolished sample stood out with a high F.E. of 46.3% for hydrocarbon production. The reason for this behaviour was, possibly, the presence of robust Cu2O layers that prevented the sample from catalyst poisoning and helped form a strong bond with CO* (carbon monoxide free radical).

The thesis opened up avenues for further research. By further investigation of factors like grain orientation and grain boundary density combined with XPS results, the understanding of the complex nature of passive layers formed on copper during CO2 reduction can be improved, which will ultimately help develop better catalysts. ... Read more

A long standing research field in material science has been the trade-off between strength and ductility of steels. Advanced High Strength Steels (AHSS) aim to combine these two properties and provide steels that can increase safety and lower CO2 consumption in automotive applications, by decreasing weight. To further decrease the environmental impact, novel quenched and partioned (Q&P) martensitic stainless steel is considered to prevent corrosion. Quenching and partitioning is a heat treatment that aims for a martensite/retained austenite microstructure with specific phase fractions to optimize strength and ductility. While mechanical properties are well researched for Q&P treated martensitic stainless steel, the corrosion properties are not that widely documented. This thesis aims to discover the influence of the microstructural development in terms of phase fractions due to the Q&P treatment, and the manganese content on the corrosion properties of martensitic stainless steel. Two alloys with chemical composition 0.2C-12.5Cr-0.35Si-XMn, where X stands for 0.7 for the low manganese alloy, and 3 for high manganese alloy, are considered for this study, and are compared to a commercial AISI 420 martensitic stainless steel. The microstructure was investigated by the use of optical microscopy, energy dispersive X-ray spectroscopy (EDS), electron probe microanalysis (EPMA), scanning Kelvin probe force microscopy (SKPFM). This was combined with electrochemical experiments including Open-circuit potential measurements, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). When compared to commercially available AISI 420 martensitic stainless steel, the novel Q&P MSS showed improved corrosion properties. This can mainly be attributed to the lack of chromium rich carbides (Cr23C6 or Cr7C3) in the Q&P treated MSS. However, this improvement in corrosion properties was only observed for the samples with low manganese content. The increase of fraction retained austenite did show an increase in corrosion potential, making the steel more cathodic, but the improvements in terms of pitting potential and passive film properties are limited. Samples with high fresh martensite fractions also showed an increase in corrosion potential, but only marginally increased in terms of length of the passive region. EIS data shows that the addition of fresh martensite reduces the passivity properties of the material. Volta-potential measurements done by SKPFM showed a clear difference between primary martensite and fresh martensite of up to 20mV and were overlapping with the topography maps. This can be an indication of increased tendency to form micro-galvanic cells between martensite phases. Manganese was found to be detrimental for the corrosion properties of the Q&P treated MSS. A clear drop in the length of the passive region shows that the high manganese samples are more susceptible to pitting. EDS measurements and EPMA elemental distribution maps showed local zones of decreased chromium and increased manganese and silicon. This indicates that there are secondary phase particles present in the material in the form of manganese silicide or manganese sulfide. Volta-potential measurements done by SKPFM showed these particles behave more anodic in comparison to the matrix of the material. The number of particles per unit area was increased for the samples with high manganese content. These inclusions greatly reduce corrosion performance, showing that the addition of manganese is detrimental for corrosion performance. Several other microstructural features are discussed in terms of influence on the corrosion performance of the material. Which include prior austenite grain boundaries, elemental banding of chromium and manganese and Volta-potential differences between martensite laths. ... Read more