This research aimed to optimize the process parameters of small copper parts printed with binder jetting. The optimisation was distinguished by dividing the parameters in print and post-process parameters. Binder jetting is an additive manufacturing technique that combines layers of the material in powder form with a binder. After the printing process the printed samples need curing, debinding and sintering. The binder acts as a temporary glue to hold the shape and is later removed during the debinding. The sintering fuses the powder particles together, below the melting temperature. With binder jetting it is the aim to achieve the high density parts, as there is no compression of powder during the printing process. This often leads to low density parts with binder jetting. The two problems that needed to be solved, were: how can the bleeding issues be stopped and at what temperature, time and environment can the printed copper be sintered. Multiple print sessions were done to: first test the known print parameters, second optimize the print parameters and third, print with optimized print parameters. ThermoGravimetric Analysis (TGA) was conducted to determine the correct debinding and sintering temperature of the copper samples. The bleeding issues could be solved by adjusting the saturation level. The saturation level was reduced from 104 % to 72 %. The lower percentage gave 0.5 mm dimensional accurate samples and no bleeding issues. Compression testing was done to compare the mechanical behaviour to that of conventionally manufactured copper. However the discs used for compression testing needed to be bigger in size than the cubes used for optimizing the sintering process. This lead to not fully sintered discs used for the compression testing. Meaning the achieved compressive strength and elasticity modulus were 1 % of conventionally manufactured copper. Three working sinter sessions were compared to see which gave the highest achieved density. Sintering 10 hours in argon at 1093 ℃ or in vacuum at 1080 ℃ both achieved the same high densities. Shell printed cubes performed better with an average density of 73 ± 8 % in argon and 74 ± 7 in vacuum. The samples placed on the top level inside the sintering oven achieved higher densities than in lower levels. Two shell printed cubes in argon achieved a density of 83 ± 0.5 % with a volumetric shrinkage of 40 ± 1 % and two shell printed cubes in vacuum achieved a density of 82 % with a volumetric shrinkage of 40 %. Solid cubes reached lower densities, with 67 ± 10 % in argon and 71 ± 7 % in vacuum. As with the shell printed cubes, the solid cubes have a high deviation due to the placement of the samples on different levels. The solid cubes had less volumetric shrinkage and rather high deviation due to the same reason, with 25 ± 16 % in argon and 35 ± 11 % in vacuum. The density is measured with a caliper and with Archimedes which gave quite different results. Densities measured with Archimedes were up to 22 % higher due to the porosity of the samples. All the measurements done by other copper binder jetted parts are done with Archimedes. Thus it seems the 74 % and 82 % is low when compared to 91 % density achieved in literature, but it is not known how accurate these measurements are.

For in-­situ resource utilisation start-up Maana Electric, an investigation was undertaken to determine whether a cover glass for solar panels can be produced using only desert sand as the raw material. During this investigation, the composition of desert sand, melt formation, processing temperatures, and mechanical and optical properties were considered. The composition of 18 desert sands was analysed by means of X­ray fluorescence and estimations of mineralogical composition were made, after which an attempt was made to melt the unmodified sand samples in a microwave furnace built for the purpose. Melt formation was further observed by melting binary combinations of store bought minerals that were found in the desert sands. The composition data and modelling of temperature-viscosity curves were employed to explore lowering the practical melting of the sand point by modification of the composition through benificiation. `Synthetic benificiated desert sand' was produced and melted based on the results. Glass samples produced were characterized using X­ray fluorescence, visual inspection, optical spectrometry, and fracture mirror analysis. It was found that about half of the desert sand samples assessed contain over 90 wt% silica, making it less feasible for use as raw material for glass due to high melting temperatures and/or large waste streams from benificiation, while sands containing larger fractions of carbonates and/or feldspars will form a melt at less than 1650 degrees Celsius if the SiO2 content is less than 55 wt%. Transmission of 85 % of ~550 nm wavelength light was shown to be possible for desert sand glass of 3 mm thickness if Fe2O3 content is lower than 0.1 wt%, while for the same transmission in the complete effective spectrum of silicon based solar cells the iron content needs to be lowered further. Known absorbing species such as Cr2O3, NiO and CuO were detected in desert sand in trace amounts, but were not present in the synthetic mixtures, the influence of these contaminants on transmission requires further research. Mechanical analysis was inconclusive due to a limited number and low quality of the samples produced, but a review of the literature implies that a Young's modulus of >70 GPa and flexural strength of >45 MPa are attainable in a glass produced from desert sand components.

Research has shown the Circumferentially Notched Tensile (CNT) Specimen to potentially be a size-independent fracture toughness specimen. This research focusses on expanding the practical applicability of the CNT specimen as well as using it to perform fracture toughness tests on S690QT steel and simulated CGHAZ material in S690. Based on literature research the research goals of the research were to investigate different pre-cracking methods with the focus of creating cracks with little or no eccentricity, improve the accuracy of CTOD measurements, determine the equivalency between CNT and conventional fracture toughness, determine the size of the plastic zone at the crack tip specimen and find alternative methods of microstructure simulation. In order to improve pre-cracking rotational bending (RB) and standalone compression – compression (C-C) fatigue were used, both lead to low eccentricity cracks, where the length of the crack could be influenced by changing the process parameters or specimen geometry. Room temperature CTOD measurements were performed on both, where RB specimen showed an average CTOD of 0.12 mm and C-C specimen of 0.18 mm. This difference is believed to be caused by the unique stress free situation at the crack tip of the C-C specimen. By using digital image correlation (DIC) and optical microscopy, the most accurate approximation of the CTOD was determined by comparing extensometer data to optical measurements. Influence of the eccentricity of the ligament was on the fracture toughness was found to increase for brittle material. Equivalency between CNT and conventional specimen was determined by comparing both RB and C-C specimen’s CTOD at low temperature (-100 °C). C-C specimen were found to show comparable fracture toughness, while RB showed an increased value. The size of the plastic zone was measured using EBSD, measurements on annealed S690 and low carbon steel failed to show distinctive plasticity, possibly caused by insufficient plastic strain. Inductive heating was tested as a replacement for Gleeble heat treatment with promising results, however the Gleeble was used for producing all S690 CGHAZ samples. C-C was found to be the only viable pre-fatiguing method, creating average crack length extensions of 0.49mm and an eccentricity of 0.18 mm. CNT results showed a slightly lower room temperature CTOD compared to conventional specimen (0.12 mm vs 0.08 mm), low temperature results showed comparable CTOD values. More research is recommended in further development of the new standalone C-C pre-fatiguing method, improving the inductive heating and cooling setup, expanding the DIC test setup, determining the plastic zone size by performing more EBSD measurements or by performing nanoindentation measurements and using CNT specimen on very brittle materials.

The so-called “hydrogen economy” became one of the scientific targets among the different renewable energies alternatives, as a result of the efforts to transition from fossil fuels to environmentally-friendly energy sources. In this context, various options to transport and store hydrogen are being explored. Gaztransport & Technigaz (GTT) company, intending to be part of this challenge, is exploring the possibility to transport liquid hydrogen (LH2) in pre-existent ship’s containers initially designed for liquid natural gas (LNG) transportation. This project is about the study of the surface effect of the interaction between hydrogen with iron-based alloys in the case of 304L stainless steel (uncoated and coated with TiO2) and Invar alloy.The methodology consisted of electrochemical induced hydrogen evolution on an iron-based austenitic metal cathode taking advantage of the intermediate adsorbates (atomic hydrogen) generated during the reaction to study the electrochemical adsorption efficiency. Characterisation of the materials, by techniques like XRF, XRD, optical microscopy, and SEM, is conducted before and after hydrogen exposureso that it was possible to evaluate the effect of hydrogen ingress.The results showed that the chemistry of the surfaces is irreversible changed after the electrochemical induced hydrogen sorption/desorption process due to the formation of oxides. The amounts of hydrogen desorbed were quantified after different H2 loading times. In all cases, the amount of hydrogen desorbed showed a maximum after which the hydrogen desorbed decreased significantly. The maximum for uncoated 304L stainless steel was after 24 h, 90 min for the coated 304L, and 2 hfor Invar. The welds are the most vulnerable sections to hydrogen ingress in both cases. XRD results before hydrogen exposure revealed that 304L consists of an austenitic matrix with around 5% of ferrite. An increment of the austenitic volume fraction of 2.2% was observed after the H2 sorption/desorption process. Invar is a purely austenitic phase, and no changes in the phase composition were observed after the H2 sorption/desorption process.

Bioengineered skin was initially developed for clinical application in reconstructive surgery, but nowadays it is also considered as a suitable skin model for research. Research applications range from assessment of cosmetic and pharmaceutical products to the modeling of pathological skin conditions. For example, psoriasis is a complicated skin disease that strongly concerns the scientific community because of its unclear pathogenesis and the current inability to cure it. The Pharmacogenomics Lab of ETH has been working on the development of psoriatic skin models in order to investigate the driving mechanisms of the disease and to later implement high-throughput drug screening to explore treatment possibilities. However, the manual production into transwell inserts results in unstable, self-contracting and inconsistent skin models, pain points that the Pharmacogenomics Lab would like to eliminate. A recent collaboration between the Product Development Group and the Pharmacogenomics Lab has been recently initiated in an attempt to standardize the fabrication of the psoriatic skin models. For this purpose, this Master Thesis focused on the investigation of the potentials and limitations of automated injection molding, a method developed by the Product Development Group, in the generation of consistent and representative dermo-epidermal models for psoriatic skin. After a series of experiments, it was seen that in-mold fabrication achieves homogeneous and consistent dermal hydrogels that maintain their dimensions throughout the whole cultivation period regardless of the collagen concentration employed for the dermal matrix, while automated injection molding allows the utilization of collagen concentrations higher than the unstable 5mg/ml, traditionally used in the manual fabrication method. All collagen concentrations exhibited similar biological performance, but the optimum fibroblasts viability was achieved in case of 5mg/mL, meaning that the whole injection molding process should be faster and even simpler to fully prevail over manual fabrication of skin models and better fit the requirements of skin disease research. Keratinocytes viability and differentiation was similar for all mold designs, all collagen concentrations and both fabrication methods. Development of a first psoriatic model, consisting of psoriatic fibroblasts and healthy keratinocytes, did not show any direct effect of diseased fibroblasts on keratinocytes proliferation and differentiation as the epidermal layer of the psoriatic model was very similar to this one of the healthy model. Evaluation of the automated seeding of keratinocytes for further standardization of the process and elongation of the psoriatic model’s cultivation period for a more thorough study should be the next steps. In the long-term, incorporation of all the psoriasis-related cells and molecules in a simple and fast way, as well as further advancements in the mold design to facilitate a direct high-throughput drug screening should be considered.

Fatigue failure is a governing limit state for marine structures. Marine structures are composed of the numerous structural members connected by the welded joints which are the typically governing fatigue sensitive locations. In this thesis, attention has been paid to fatigue of welded joints from design and from testing perspective. The double sided longitudinal attachment is a common structural detail in marine structures and available resistance information, SN data, has been used to investigate the life time estimate accuracy in case the total stress is adopted as fatigue damage criterion. The single sided butt joint is a common structural detail in marine structures like steel catenary risers and a specimen has been designed for testing using the hexapod in order to ensure fatigue induced failure at the required location.Fatigue design of double sided welded longitudinal attachments using a Total Stress criterion The recently developed total stress concept considers both the weld notch and far field characteristic contributions. The total through-thickness weld notch stress distribution has been adopted to establish the total stress fatigue damage criterion and corresponding fatigue resistance curve. Thanks to a semi-analytical formulation, it is easy to determine the total weld notch stress distribution. The involved weld load carrying stress component is a characteristic one and unique for each weld notch location. A double weld element beam model has been developed to replace the original single weld finite element beam model in order to capture correct estimates for the double sided longitudinal attachments. Alternatively, a parametric has been established as well. The weld notch angle has turned out to be a governing parameter. Evaluation of the fatigue resistance of the welded double sided longitudinal attachment using the Total Stress concept shows a better accuracy in comparison to the nominal stress, hot spot structural stress and effective notch stress concept results. A governing factor for double sided longitudinal attachments is investigated which is the base plate thickness tb. Although, the IIW classifies the longitudinal attachment based on the attachment length la, the base plate thickness tb is much more dominant. Fatigue testing of single sided butt joints using a Hexapod The riser system forms a significant part of the development costs for floating offshore oil production facilities. The SCReen joint industry project aims to optimise the fatigue design and maintenance costs for Steel Catenary Risers (SCR’s). Generally, published fatigue resistance data of SCR welded joints are performed using resonance bending tests, which have two major limitations: a very high mean stress state and unrealistic variable amplitude loading. In order to obtain realistic fatigue resistance data, the SCReen project plans to do the fatigue tests with the Hexapod. A dedicated specimen containing the critical single sided butt joint has been designed  in order to obtain fatigue failure at the required location, involving two girth welds at the flange-pipe connection and the single sided butt joint at the middle of the specimen. With a post welding improvement, fatigue failure at the intended weld root location can be obtained.

With fossil fuels being phased out and growing global interest in a hydrogen economy, there is demand for re-purposing existing pipelines for transportation of hydrogen gas. However, hydrogen is known to have adverse affects on the properties of steels. Hydrogen will dissolve in the steel matrix and contribute to a reduction of mechanical properties, causing Hydrogen Embrittlement (HE). There is currently a knowledge gap about the behaviour of pipeline steels and their welds in a gaseous hydrogen environment that prevents re-purposing of pipelines for hydrogen transport. In this work, a combined approach of modelling and in-situ mechanical testing was used to assess the HE susceptibility of X60 pipeline steel and its girth welds. To this end, a novel tensile setup featuring in-situ charging with high pressure H2 gas and a sample geometry representing miniature pipelines was developed and validated. To our best knowledge, this setup design has not been reported elsewhere, making this a breakthrough design. An FEA modelling approach was used to estimate the pre-charging duration as well as to gain an insight into the stress states inside the notched samples. It was found that both the base and weld metals lose ductility when subjected to gaseous H2. The base metal showed 27% loss of ductility when subjected to 100 bar H2, which further increased to 40% in notched samples. A trend of increasing loss of ductility was found with increasing pressure for the weld metal, which showed up to 14% loss of ductility at 100 bar H2. The weld metal also retained more of its reduction in cross-sectional area after fracture in H2 as compared to N2 than the base metal. Other characteristics like yield strength and UTS were not affected by the hydrogen gas. The fracture mechanism in the both metals was found to change from microvoid coalescence (MVC) fracture to quasi-cleavage (QC) fracture. The base metal fracture mechanism changed to QC completely, while the weld metal only showed partial QC fracture. In the base metal, ductile fracture mechanisms like HELP and possibly AIDE were found to be dominant even in the QC fracture mode. It was concluded that the weld metal is less susceptible to HE than the base metal in a gaseous hydrogen environment. For both metals, HE effects were only observed at high amounts of plastic strain, which is outside of the operating conditions of a pipeline. However, before pipelines can be repurposed for hydrogen transport, fatigue testing should be performed to assess the influence of existing defects and cyclic loading conditions on the HE performance of both steels.

Refractories are widely used as lining material in the steelmaking industry. This class of materials is known for its superior creep resistance. However, creep of refractory linings is a known phenomenon in refractory science. Therefore, knowledge on creep behaviour is critical for furnace lining life predictions and selection of materials. This work, in collaboration with Tata Steel IJmuiden, focuses on creep development in magnesia carbon (MgO-C), a refractory often found in Basic Oxygen Furnaces (BOF). In this research, the influence of binder and aluminium content on creep development in MgO-C was investigated. This was addressed, based on the microstructural changes, phase transformations and thermo-mechanical properties. Microscopy, scanning electron microscopy, X-Ray diffraction, cold crushing strength, hot modulus of rupture, dilatometry, refractoriness under load and hot compressive strength tests were conducted in order to explain creep behaviour. For creep testing, a nonstandardised set-up was designed to be able to retrieve creep data more efficiently. The experimental configuration increased the load every 5 hours (multi-stage). Resulting creep rates were validated against a single-load stage creep measurement. A small difference of 5% in creep rates was observed. This indicated that the multi- and single-stage results are within range of each other. Therefore, the proposed multi-stage creep test can be considered a viable creep testing method. A trend of decreasing creep rates with increasing binder content was found. Increasing the content from 2% to 3% showed a maximum decrease in creep rates of 80%. A further increase of binder content from 3% to 4% showed a maximum decrease in creep rates of 30%. This behaviour was mainly attributed due to volatilisation of the binder and magnesium, and densification due to carbonisation of the binder. Increasing the aluminium content from 0 to 1% resulted in a maximum decrease in creep rates of 70%. This was mainly attributed due to spinel formation. The irreversible volume expansion due to spinel formation, increased the density and the stress state within the material. As a result, micro cracks formed which strengthened the material and improved creep resistance. The outcomes of this work are an important contribution to refractory science. However, further development of refractories is still necessary, especially due to the increasing pressure on the steelmaking sector to make its processes more sustainable.

High Manganese Austenitic Steel (HMnAS) is a novel steel exhibiting excellent mechanical properties at arctic temperatures. Defense Material Organisation (DMO) is interested in the feasibility of using HMnAS in their navy's ships alongside EH36 high-strength shipbuilding steel, using 307PF stainless steel weld filler metal. The feasibility of using HMnAS is investigated by performing mechanical tests on both the base materials and the weld. Microstructure and fractographs were analysed using optical and electron microscopy, and the chemical composition was measured using EDS, EPMA and XRD. The results of mechanical tests were compared to current standards for EH36. This study yielded three main observations. The first important result is the finding of severe anisotropy in the HMnAS. Impact toughness in the L-T direction was threefold the amount in the T-L direction. This is thought to be because of stringer MnS inclusions, elongated in the rolling direction. The second observation was the inadequate mechanical behaviour at the EH36 fusion line and the weld, these did not meet the requirements of IACS standards. Lastly, after observing a crack path along the fusion line of the CTOD fatigue pre-cracking, microhardness tests over the fusion lines were conducted and pointed out a hard band along the EH36 fusion line. This band is found to be a martensitic band (15-108 microns in width) that hampers mechanical performance. This investigation concludes that the current weld joint is not as desired. More research is required to improve the weld joint before HMnAS can be implemented on navy ships. Future research for DMO should mainly focus on the welding characteristics and the filler metal composition, to improve weld performance.

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.