Traditional carbon capture processes require large amounts of energy to regenerate the solvents used. Recent research has proposed to decrease the energy requirements of this process by integrating the system of carbon capture and electrochemical conversion, removing the need for the traditional regeneration step. The integration of these two steps involves the use of the same medium for both the carbon capture solvent and for the electrolyte for electrochemical conversion of the captured CO2. The proposed methodology takes advantage of the inherent elevated temperatures resulting from ohmic losses in the electrochemical system, especially at an industrial scale and helps optimize the efficiency of the conversion process. This study investigates the use of non-aqueous solutions of 1:4 choline chloride to ethylene glycol coupled with monoethanolamine as the medium for this process, particularly focussing on its use as the catholyte in this system. Specifically, this project targets the production of carbon monoxide using silver cathodes in small laboratory scale compact H-cells, with an anolyte of 0.5 M sulphuric acid and a Nafion-117 cation exchange membrane separating the compartments. Different operating conditions, including pulsed electrolysis, are utilised to attempt to modify the levels of carbon monoxide production and stabilise the system for long term operation.
Initial investigations into this system found that carbon monoxide could successfully be produced at constant reduction potentials vs. Ag/AgCl of -1.5 V and -1.7 V for approximately 10 minutes of operation when operating at 65 °C. Pulsed electrolysis has been proven to be able to increase the stability of carbon monoxide production for up to an hour of operation. The study found that the most promising conditions for the pulsed electrolysis are using positive anodic potentials vs. Ag/AgCl of either + 0.1 V or + 1.5 V for between 5 and 40 seconds in combination with cathodic potentials vs. Ag/AgCl of - 1.5 V. The faradaic efficiency of carbon monoxide production was able reach up to 24 % for one hour of operation with relatively stable production profiles when using pulsed electrolysis.
The results of this project show that this system can produce the desired carbon dioxide reduction reaction and with the use of pulsed electrolysis this can be achieved for at least one hour with faradaic efficiencies of carbon monoxide production greater than 20%. These findings showed a better overview for the next stage of this research. In particular, further work involving longer term operation of the cells is of interest after this research.

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 presence of retained austenite (RA) has been proven beneficial for the formability of Advanced High Strength Steels. Therefore, multiple thermal austenite stabilization methods have been researched, such as Mn-partitioning during intercritical annealing in medium Mn steels. The Cyclic Partial Phase Transformation (CPPT) approach has been successful in obtaining localized Mn-enrichment at the ferrite/austenite interface through cyclic annealings at intercritical temperatures in a medium Mn steel. In this thesis, the possible application of CPPT heat treatments towards interfacial austenite stabilization at room temperature in medium Mn Dual Phase (DP) steels is studied. ThermoCalc modelling and dilatometry measurements were used to determine the optimal CPPT parameters for fully martensitic Fe-Mn-C-Si samples with varying concentrations of manganese. Scanning Electron Microscopy acquisitions of the resulting microstructure showed a strong influence from the initial microstructure. Samples which went through a full austenitization formed coarse martensitic islands and equiaxed ferrite grains. However, samples which were intercritically annealed from a fully martensitic state resulted in fine and elongated ferrite grains surrounded by martensite. X-Ray Diffraction analysis revealed that CPPT treated samples with 2wt.%Mn and 4wt.%Mn had a maximum RA volume fraction of 1wt.% and 4wt.% respectively. Up to 16wt.% of RA was obtained at room temperature through CPPT heat treatments for samples with 6wt.% Mn. This difference in results has been attributed to the concentration spike of Mn at the ferrite/austenite interface characterizing the NPLE austenite growth, as well as to the widening of the Mn-enriched zone through repeated isothermal intercritical annealing cycles. While a relatively high volume fraction of RA has been successfully obtained at room temperature in 6wt.% Mn DP steels, its interfacial morphology could not be confirmed due to the interference of the fine ferrite/martensite microstructure with the Electron Back-Scattered Diffraction analysis.

The high theoretical volumetric capacity, abundance of magnesium in the earth’s crust, and the relatively good safety features of Mg metal, have drawn great attention to developing Magnesium batteries as a follow-up to the success of Li-ion battery technology. However, the magnesium metal is incompatible with most electrolyte solvents and salts, which passivates the surface of magnesium and causes the battery failure. One of the crucial approaches to address this problem is to seek novel electrolytes which have good metallic Mg compatibility and subsequently improve the cycling performance.

In this research, the feasibility of combing PEO, Mg-alginate and MgCl2 to design a solid polymer electrolyte (SPE) for Mg-ion batteries has been assessed. The SPE membrane shows a conductivity of ~10-5 S·cm-1 at 60 °C and an increased value up to ~10-4 S·cm-1 at 80 °C and above. The XRD results have suggested there is no real interaction in between the two polymers which can cause reconstruction of the polymer structure. Moreover, this electrolyte material is highlighted with an excellent cycling stability of up to 150 hours. At last, a possible model which could explain the Arrhenius behavior of temperature-dependent ion conduction is proposed for this SPE material. Overall, this research demonstrates the potential application of Mg-alginate for Mg energy storage in terms of developing a polymer electrolyte, despite further modification in the future is needed.

Mycelium based composites (MBC) have revolutionised the field of material production, where a living fungus is employed to overgrow and bind lignocellulosic substrate materials together. Their bio-based nature, low embodied energy, and biodegradability, mark their great potential to reduce the increasing pressure conventional materials put on the environment. Unfortunately, the material's applications are limited due to its low mechanical properties, that are equivalent to those of foams or natural fibre boards. Furthermore, where the material is primarily used and studied in its heat-treated non-living form, harnessing the biological power of the fungus shows to give the material self-healing and sensing capabilities. The required hydrolysed state is however shown to further decrease its mechanical properties, and yet hardly evaluated in literature. Especially the mechanics of the mycelium-lignocellulose interface are inadequately studied, and important to evaluate for a broadening of the living composite material's applications.

In this study we present the development of a double cantilever beam (DCB) test according to ASTM D5528, setup to quantify the interlaminar fracture toughness (G_I) of Ganoderma lucidum (G. lucidum) grown in between wood veneers. The data was evaluated using an analytical approach based on a decrease in the beams' compliance. The specimens were fabricated with the use of additive manufacturing, allowing precise control over the placement of the fungus and its provided nutrients. Its growth behaviour into the substrate was qualitatively assessed through optical microscopy and scanning electron microscopy (SEM), and its digestive ability on the surface by fourier-transform infrared spectroscopy (FTIR).

A mycelium-laden ink presented by Gantenbein et al. (2023) was reproduced with a 75% lower agar content to serve a stable source of mycelium on the DCB specimens [1]. A growth period between 3 and 4 weeks from the printed hydrogel was required for substantial mycelium-substrate binding, which stabilised after 4 weeks of growth. Furthermore, the provision of malt extract (ME) was required, but not needed to be higher than 5% of the ink's weight. The G_I was in these conditions reported to be 1.83 J/m² on hornbeam veneers, where a maximum value of 3.46 J/m² was reached. Variable growth generated substantially different mechanical properties, which resulted in the lower G_I of mycelium grown on beech and spruce samples, caused by the use of an older fungal inoculum of a different reference plate. A stronger binding on beech than spruce did suggest a more important role of the substrate chemistry than its density. The mycelium always showed cohesive failure, showing the low G_I to not result from poor substrate adhesion, but rather from the mechanics of the hyphae network developed. Microscopy and FTIR evaluations showed the ability of G. lucidum to digest the hornbeam's lignin. The full depths of hornbeam and beech veneer substrates with 5 and 3 mm thickness were colonised, where vessel elements served as the main pathway for the hyphae.

This study was, to the best of our knowledge, the first to isolate the binding behaviour of a living mycelium in a mode-I loading condition. It thereby provides valuable new insights in the field of living MBC, and contributes to the further development of this advanced, eco-friendly, and living material. The setup can now be utilised to study the binding behaviour of different fungi on substrates of varying chemistry and porosity. Furthermore, aiming to elucidate the use of additive manufacturing in the composite production, this study opened up pathways into controlling the composite's properties in the future.

[1] Silvan Gantenbein et al. “Three-dimensional printing of mycelium hydrogels into living complex materials”. In: Nature Materials 22.1 (2023), pp. 128–134.

Accelerated tests have been commonly used by the marine coating industry to evaluate the performance of a coating in a short duration of time. Replicating natural exposure in an artifi- cially simulated manner is a challenging task due to the various factors that induce corrosion in the natural environment. Continuous salt spray testing is a popular accelerated test, but it does not replicate the actual exposure scenario as intensifying the factors inducing corrosion does not produce the same result as natural exposure. However, it was found that alternating between wetting and drying of the coating correlates well with natural exposure. ISO 12944- 9, a standardized accelerated test for corrosion protection in the marine environment, is one such test which alternates between different exposure conditions. This is performed in order to replicate the exposure conditions that a marine structure experiences. This ultimately aids in understanding the performance and durability of the coating within a shorter period. Besides, accelerated tests can be used to correlate with the natural exposure, in order to circumvent the issue of testing coatings in the natural environment for years to understand the coatings performance and durability. This thesis aims to correlate the performance of a commercial marine vinylester coating re- inforced with glass platelets named Ecospeed, when exposed in a natural service life envi- ronment versus that when tested in an accelerated environment. For accelerated ageing, the standard ISO 12944-9 was used, which is the standard exposure conditions for coating sys- tems undergoing extreme conditions in the marine environment. For the natural exposure, two in-service vessels coated with Ecospeed were selected to test its performance. Both vessels were coated with Ecospeed for 10 and 15 years. The coating’s performance is evaluated using electrochemical impedance spectroscopy (EIS) in both the natural and accelerated environments. EIS measurements were performed at peri- odic intervals of 1000 hours until 3000 hours for the accelerated exposure. EIS measurements were obtained on the 10 and 15 years old ship at multiple locations on the hull. This was done to check the uniformity of corrosion protection and variation of coating performance across the ship. Pull-off adhesion tests were also conducted after 2000 hours of accelerated exposure and the strength was reduced to more than half its initial strength prior to exposure in ISO 12944-9. The results of the accelerated test indicated gradual reduction in the impedance of the coating over 3000 hours of accelerated test exposure. The magnitude of impedance at the lowest frequency of 10 ́1 Hz was 4.23 x 1010 Ω cm2 after 3000 hours of accelerated exposure and for the 15 year field exposure the magnitude of impedance was 4.27 x 109 Ω cm2, which is well above the minimum industry standard of 107Ω cm2. Considering the impedance values for both the accelerated and natural exposure, it can be said that the impedance of Ecospeed is atleast 2 orders of magnitude higher than the minimum industry standard requirement even after 15 years of natural exposure. The accelerated results of 1000 hours had good correlation with the impedance measurements performed on the 10 year old ship. The magnitude of impedance of the 15 year old ship was lower than the magnitude of impedance obtained from 2000 and 3000 hours of accelerated exposure. This means further exposure in the accelerated environment is needed to correlate with a 15 year old ship.

Essential criteria to a shaving blade include wear resistance, corrosion resistance and a sharp cutting edge. The material selection for improved cutting elements as well as increasing the longevity of the blade would provide benefits not only to the consumer experience of a more efficient shaving performance, but also a more sustainable solution to the recurring disposal of blunt razors.

Quenching and Partitioning (Q&P) is a novel steel heat treatment to create microstructures containing martensite and retained austenite. In recent years, there has been a growing interest in applying Q&P treatments to martensitic stainless steels with the aim to create stainless steels with the mechanical properties of Advanced High-Strength Steels (AHSS). The development of Q&P stainless steels for lightweight structural applications could be a game changer for the automotive industry. The application of Q&P stainless steels can increase the service life of a car, reduce maintenance cost and contribute to lowering CO2 emissions. In this thesis, Q&P treatments with varying quenching temperatures were applied to two novel stainless steel alloys with composition 0.2C-0.35Si-0.7Mn-12.5Cr and 0.2C-0.35Si-3.0Mn-12.5Cr. The effect of quenching temperature and Mn content on the microstructure development was investigated using dilatometry, X-ray diffraction (XRD), optical microscopy, electron backscatter diffraction (EBSD), electron probe micro analysis (EPMA) and phase field simulations. It was found that Mn addition lowers the optimal quenching temperature and increases the maximum retained austenite fraction that can be obtained by Q&P treatment. Austenite phase fractions of approximately 0.22 and 0.3 were stabilized in the microstructures of the low-Mn and the high-Mn alloy, respectively. The carbon concentration of retained austenite increases with decreasing quenching temperature but is much lower than expected from the full partitioning assumption. The non-uniform distribution of primary martensite and untransformed austenite as well as carbide precipitation was seen as a means by which austenite enrichment and retention are reduced. Additionally, results from this study indicate that segregation of Mn and Cr affects the local Ms temperature and causes microstructural banding of primary martensite which leads to a non-uniform retained austenite distribution in the final microstructure.

In recent years, the world has witnessed a dramatic advancement in sustainable energy development. Due to the inconsistent supply of such energy, a more efficient energy storage method is in need. Among many options, lithium-ion battery stands out due to its lightweight, high energy density, and high discharge potential. Currently, the most commonly adapted anode materials in lithium-ion batteries are carbon-based, most often graphite. It shows a layered structure that can be used to store Li+ ions based on the intercalation and de-intercalation mechanism. Although this material is stable and successfully commercialized, due to its low specific capacity efforts have been put into searching other potential anode materials. Potential materials are aluminum, tin, and silicon. Among them, silicon shows an ultra-high (theoretical) specific capacity that is 12 times higher than that of carbon. However, the volume taken up by the material increases by about 300% upon lithiation and de-lithiation. Hence, silicon anodes show a poor capacity retention ability comparing to its graphite counterpart. In this work, by using a silicon alloy, we aim to alleviate the effects of volume expansion of Si by introducing alloying species and by providing a porous structure. In this work it is demonstrated that this material structure is able to absorb the expansion, while still rendering a high specific capacity. Silicon alloy samples over a wide range of alloy concentration and porosity were synthesized using PECVD. Samples were assembled into pouch-cells and coin-cells and tests were performed to compare the battery performance of each sample. A FEM model was built, enabling more investigation opportunities. Together with the experiments, they revealed how alloy concentration and porosity influence the specific capacity and cycling ability of the anode.

Salts of trivalent cerium (Ce(III)) are known to successfully hinder localised corrosion phenomena typical of aerospace aluminium alloys by forming a thin passivation layer on top of the corrosion-active intermetallic phases. This is generally observed to happen when the alloy is under immersion conditions in a solution containing Ce3+ ions. However, some very preliminary works suggest that protection provided by this layer is lost once the passivated metal is re-exposed to a corrosive solution in absence of inhibitor (for example, aqueous solution of sodium chloride). This (in)stability process has not been directly addressed in literature and is, therefore, not well understood. A deeper understanding of such process and the strategies that could lead to a higher passive layer stability are needed to bring Ce-based inhibitor technologies closer to application and replacement of the harmful Cr(VI)-based primers. In this work we studied the inhibition mechanism and stability of cerium inhibiting layers created on AA 2024-T3 upon exposure to electrolytic solutions containing Ce(NO3)3 and NaCl. The stability of Ce(III) layers after re-exposure to corrosive electrolytes (i.e. without inhibitors) is investigated. Furthermore, the interaction between Ce(III) layers and different organic compounds, namely 2,5-Dimercapto-1,3,4-thiadiazole (DMTD), phytic acid and sodium alginate, was also explored as a potential strategy for stabilisation of Ce-based inhibitive layers.
Due to the complex interpretation of electrochemical signals typically used in corrosion studies (e.g. electrochemical noise and impedance spectroscopy), it was decided to combine such electrochemical methods with highly spatio-temporally resolved in-situ microscopy in order to assess both corrosion of AA 2024-T3 and its inhibition. For this purpose, a home made optical-electrochemical experimental setup was used, together with a protocol for optical data analysis. This hyphenated in-situ protocol is further supported with SEM-EDS, Raman and SKPFM analysis after exposure. In the work here presented, the unstable nature of Ce-inhibitive deposits was found to be associated to their dissolution after re-exposure to inhibitor-free electrolytes. Studies devoted to the stabilisation of Ce(III)-inhibitive layers with organic molecules indicated different behaviours and outcomes. Alginate oligomers efficiently passivate the Ce-protected intermetallic phase, but, at the same time, destabilise the Al-rich matrix, which became subject to general corrosion. Phytic acid was found to provide synergy with Ce(III) layers, which however lacked in stability. Treatment of Ce-passivated surfaces with DMTD, on the other hand, shows a significantly delayed onset of optical-electrochemical activity upon re-immersion in NaCl solution, which suggested the accomplishment of a more stable system. The results obtained confirm the power of in-situ (i.e. under immersion) optical investigation not only to support the understanding of complex electrochemical signals, but also to deliver quantitative information relevant in corrosion and inhibition studies. The approach proposed in this research is believed to be of future help for an improved design of Cr(VI)-free anticorrosion coating systems.

The prevalence of additive manufacturing (AM), or 3D printing, has grown in recent decades as a method of manufacturing complex geometries, prototype parts, or high tuned microstructures. One method of additive manufacturing is selective laser melting (SLM), a powder bed fusion technique which utilizes a laser to melt a metal alloy powder layer by layer to form the final geometry. Inconel 718 is a nickel-based superalloy commonly used in high temperature applications due to its superior mechanical and corrosion resistance properties. Owing to a difficult in machining, additive manufacturing has become particularly advantageous method for the production of Inconel 718. The SLM process is associated with a greater degree of process defects as compared to a traditional production method, in particular a poor surface condition, porosity and an anisotropic microstructure. These surface defects pose an issue in response to cyclic loading, as they serve as stress concentrators and can become crack initiation sites. As a result, post-processing treatments are typically required to improve the quality and mechanical properties. This master work focused on two primary aims. First, the characterization of SLM Inconel 718 processed with different layer thicknesses, build directions and post-processing surface treatments and second, the development of a prediction model for fatigue life based on process defects. Smaller layer thickness was found to result in lower surface roughness, which in turn resulting in fatigue performance as compared to larger thicknesses. Differences in surface quality and properties were identified on samples built at an incline. The plane opposite the build direction (the ‘downskin’ side) exhibited higher surface roughness and increased near surface hardness. Mechanical polishing of the surface led to a significant improvement in fatigue performance associated with dramatic reduction in surface roughness and near-surface voiding. Electropolishing as a post-processing treatment did not have a significant impact on surface quality or on fatigue performance. Surface defects were identified as the location of fatigue crack initiation. Removal of these defects by post-processing would therefore provide the greatest improvement in the fatigue performance of SLM Inconel 718. The Murakami-Endo method of fatigue life prediction showed promising results in predicting fatigue life of a sample population based on defects, with good agreement to experimental data.

Selective laser melting (SLM) is an additive manufacturing technique, which is currently on the rise of being used for manufacturing bone implants. Spinal cage, dental and hip implants can for example be manufactured using SLM. Ti6Al4V lattice structures, categorised as metamaterials, can be printed by SLM with mechanical properties close to bone tissue. Due to the lattice structure the stiffness of the Ti6Al4V is decreased, by which stress shielding can be reduced. The lattice structures enhance bone ingrowth which in turn improves the implant’s integration into bone tissue. In light of this potential, this research is focused on biomechanical properties of additively manufactured Ti6Al4V metamaterials.

The current research is aimed at improving the fatigue resistance and wettability of diamond lattice structured Ti6Al4V by applying different microstructural designs and surface engineering through hot isostatic pressing (HIP), sand blasting (SB) and chemical etching (CE). Furthermore a comparison is made between the two SLM processes in terms of continuous and pulsed laser scanning. In order to verify the developed herein post treatment procedures, the tests were also upscaled to actual spinal cage implants. Furthermore, surface modifications affect its wettability which can be linked to cell adhesion and ultimately healing time of the implant. Hence Sessile drop tests were performed to assess the wettability and compare the effect of the various surface modifications.

For both SLM methods it was found that HIP reduces porosity of Ti6Al4V metamaterials, which reduces crack initiation sites and it also serves as a heat treatment increasing the b-phase fraction and thus increasing ductility
and fatigue resistance. SB and CE were found to reduce surface indiscrepancies, which decrease the effect of stress concentration and fatigue initiation sites. Finally SB induces compressive residual surface stresses which means the surface is work hardened, increasing the overall mechanical properties.

For continuous SLM samples an increase in yield strength from 89 MPa up to 115 MPa was found by applying HIP treatment. It should be noted, however, that static mechanical properties were not affected by SB and CE treatments. Fatigue resistance, both low cycle (LCF) and high cycle fatigue (HCF), was significantly improved by a combination of HIP, SB and CE. The observed trend was similar for both pulsed and continuous SLM samples. It is worth noting that SLM samples manufactured with pulsing laser were found in general to be inferior to the
continuous laser SLM, both in terms of static and dynamic properties. The difference is likely attributed to the nature of the laser scanning process, where for pulsing laser method each bead interconnection serves as stress concentration, while for continues laser it is rather the strut interconnections that act as weakest points. Furthermore, for the continuous SLM a preferred grain growth direction was observed which indicates anisotropy. This was not observed for pulsed SLM samples.

For the wettability results it was observed that SB decreases and CE increases the contact angle. A decrease in contact angle means the surface has become more hydrophilic, hence the in this study developed SB modification could be considered as more favourable for osseointergration.

The upscaled spinal cage implants post treatment procedure showed a decrease in yield strength and an increase in fatigue resistance for the HIP+SB+CE as compared to as-processed implants. The rather limited post treatment
improvement on implants was linked to the post process treatment method, which should be modified to account for the complex geometry of these structures.

Although many studies have been performed on porous absorbable iron scaffolds created by the space holder method, no studies have considered the influence of variations in space holders on absorbable scaffolds. The present study aimed to clarify the effects of space holder particle size and volume fraction, on the pore structure, resultant mechanical properties and absorbability of iron scaffolds.
Spherical iron particles were used as the matrix powder and mixed with coarse and fine rectangular urea space holding particles in volume fractions of 20, 40 and 60%, to create six different scaffolds with the space holder method. Scanning electron microscopy and energy-dispersive X-ray spectroscopy were used to observe the scaffolds surface. Thereafter x-ray microtomography and Archimedes’ tests were used to characterize the scaffolds topology. The absorbability of scaffolds was characterized by potentiodynamic polarization measurements and weight loss measurements after 3 and 11 of days immersion in modified simulated body fluid (m-SBF). Mechanical properties were determined by performing diametral compression of the scaffolds, both before and after immersion in m-SBF. SEM images showed that morphology of the final pores was similar to that of space holder particles. Pores at lower porosities are isolated and become more connective or fully connected at higher porosities. Archimedes’ data showed that space holder fraction was directly related to porosity. Pore connectivity, measured by 휇CT, is higher for fine space holding particles. Until at 60% space holder volume fraction, the high amount of space holder particles agglomerated. Furthermore, it was observed that space holding particles had a large preference to move in a plane perpendicular to the applied compaction pressure. Diametral compression showed that increasing porosity resulted in lower yield strength and elastic modulus of scaffolds. The effects of space holder particle size and immersion time on mechanical properties were less pronounced. PDP measurements showed that the corrosion mechanism of scaffolds did not change due to change in space holder particle size or volume fraction. Weight loss measurements after 3 and 11 day immersion in m-SBF showed that increasing porosity resulted in higher weight loss of scaffolds. Weight loss was marginally affected by space holder particle size. Space holder particle size affected the created pore size and surface area yet also changed the pore connectivity. Similarly, the space holder volume fraction affected the created porosity and pore connectivity yet also changed the pore size and shape. This means that the pore structure not independently changes due to space holder particle size or fraction, but rather as a combination of both. Furthermore, in this study it was mainly the created porosity that influenced the mechanical properties and absorption rate of the scaffold. Space holder particle size did not show the same differentiating results, although this might be caused by agglomerating space holder particles and its dependency on volume fraction. Differentiating the created pore structure more and using a longer immersion time should be the next objectives in the determination of the effect of space holder particles on the performance of absorbable iron scaffolds for orthopedic applications.

Within the photovoltaic industry, a lot of research is done in order to minimize losses which are created during the conversion of solar light to electrical energy. In a crystalline silicon solar cell light has to pass through several layers before it enters the silicon wafer where the electron-hole pairs are generated. As one can imagine, if more light reaches the active layer, more electron-hole pairs can be generated. It is highly desired that only one layer, the active layer, is absorbing photons of the solar spectrum. The active layers at the sunny side of the silicon wafer should be highly transparent for solar light. In addition to being transparent, these layers should be conductive to extract the generated charge carriers to the metal contacts. Current layers applied at the sunny side are not optimally transparent, so it is still possible to increase the efficiencies in the crystalline silicon solar cells. In this study, doped silicon oxide layers have been explored as a potential more transparent layer for passivation of both the silicon surface and the metal contacts. Two routes for the fabrication of doped silicon oxide layers were investigated: post-oxidation of doped polycrystalline silicon layers and post-doping of in-situ grown silicon oxide layers. To characterize this new type of material, several different measurement techniques have been applied to improve our understanding of Low-Pressure Chemical Vapor Deposition deposited silicon oxide passivating contact layers. It was found that the structure and composition of the layers is very different for these different routes. However, very good and stable surface passivation (minority carrier lifetime of >3ms) can be achieved with both types of silicon oxide layers. Also, sheet resistance measurements have indicated that phosphorus doping in silicon oxides is possible. For better insight into the electrical properties of these layers, further testing in electronic test structures is advised.

As the population ages and the know-how of the medical field progresses, the number of surgical interventions is rapidly expanding. Heart valve replacement surgery is no exception to this phenomenon; every year 280 000 heart valve replacement surgeries are performed worldwide.Despite the success of heart valve replacement surgeries, various notable drawbacks hinder its advancement. Mechanical heart valves require anticoagulant therapy to reduce the risk of thromboembolisms, thereby also introducing anticoagulant-induced haemorrhage. Further-more, the need for anticoagulant therapy makes the mechanical valve undesirable for woman who desire a pregnancy. Bioprosthetic heart valves suffer from structural valve deterioration and therefore need to be replaced after less than 15 years. Replacement surgery is dangerous,with an increased mortality rate of up to 20%. Furthermore, heart valve prosthetics do not allow for native cell tissue ingrowth, limiting their ability to self-repair and grow, the latter being of especially high importance in pediatric heart valve surgeries.A promising new concept is the tissue engineered prosthetic heart valve, which would hypothetically remove the need for anticoagulent use, allow for self-repair and growth and increase the durability of heart valve prosthetics. The process of creating a Tissue Engineered Heart Valve (TEHV) is, however, complex, and an optimal scaffold is yet to be found.Bacterial Cellulose (BC) is hypothesised to be a feasible scaffold and material for use in heart valve prostheses. BC is a biogenic polymer with a chemical structure not unlike collagen. The material is produced by, among others, the bacterium Acetobacter Xylinus. BC has been shown to have considerable mechanical strength and low thrombogenicity. Furthermore,a study in rat models has indicated no inflammatory or foreign body response to implanted cellulose. Bacterial cellulose is already successfully in use as wound dressing, and has been utilised to produce feasible vascular grafts. However, to the knowledge of the author, pure BC has not yet been used for the production of prosthetic heart valves.BC has been cultured statically with a novel method of automatic medium exchange, and rotational with a specially designed rotation device.The BC cultured with the novel method of automatic medium exchange, is more stable and stronger than patches cultured with the previous culturing protocol. However, BC cultured using the rotary device is unstable and fragile. The rotary culturing protocol needs to be improved in order to result in feasible BC tubes for the production of heart valves.The BC shows strain levels slightly stiffer, but relatively similar to those of human pericardium. Furthermore, creep behaviour is, as with pericardium, insignificant under cyclic loading conditions.More patches need to be cultured in order to increase the sample size, and thereby produce more conclusive results. The results already gathered in this master thesis research, show that BC material has promising mechanical characteristics, possibly rendering it a feasible option for the use in bioprosthetic heart valves

Electrochemical sensing is a powerful tool for the rapid detection of (bio)molecules in fluids, and is frequently used in clinical analysis and diagnostics. Diamond is arguably the best electrode material for its robustness, wide potential window, very low background current, biocompatibility and self-cleaning features.
Nowadays, there is a new trend leading to electrodes getting smaller. One of the current challenges in the development of diamond micro-electrodes is to increase the sensitivity of the diamond electrode, while the electrode’s dimensions decrease.
An interesting biomolecule to detect is glucose. 2.8% of the world population suffers from diabetes, these people need to measure their blood sugar level and manage this level by dispensing insulin in their body when needed. A glucose sensor is used to determine the amount of glucose in the blood. Boron-doped diamond (BDD) is an interesting material for the non-enzymatic detection of glucose.
In this thesis project, study has been done to the nanostructuring and functionalisation effects on the performance of sensing glucose by using diamond electrodes. Measurements have been done with different types of electrodes: bare BDD, acid cleaned BDD, BDD functionalised with gold nanoparticles, BDD with a nanowire surface structure, and BDD with a nanowire surface structure and gold nanoparticles on top. It was found possible to detect glucose with three of these samples: bare BDD, BDD with gold nanoparticles, and the nanostructured BDD functionalised with the gold nanoparticles. The other two electrode types did not give any reduction/oxidation peaks, which is attributed to the oxygenated surface resulting from their fabrication processes. The three glucose-detecting electrodes showed linear behaviour in a range of 1-10 $mM$, which is in line with the detection range of glucose in human blood. The sensitivities achieved with bare BDD, BDD with gold nanoparticles, and the nanostructured BDD functionalised with the gold nanoparticles are 0.022, 0.429, and 0.136 mA/mMcm^{2}, respectively. The addition of gold particles improves the sensitivity for glucose substantially and works like an electrocatalyst. Making use of electrocatalysts is an interesting and useful functionalisation for direct non-enzymatic glucose sensing, because sensing glucose with bare BDD is a kinetically very slow process. Results of such high sensitivities for BDD with gold nanoparticles were not published in literature yet, so this is a promising achievement that asks for continuation of research in this field.