Download flyer for Advanced Materials Poster Day 2022
The Field-of-Expertise Advanced Materials Science is an interdisciplinary network of researchers at the TU Graz in chemistry, physics, architecture, mechanical engineering, civil engineering, electrical engineering and geodesy who discover, characterize and model materials, functional coatings and components. The 2022 AMS Poster day will be held in presence on 22.04.
Welcome and FoE AMS update
FAIR with RDM
Biopolymers in Biomedical Applications
Influence of energy distribution on porosity during EBW of thin-walled aluminum components
Poster Session with Buffet
The aim of the poster session is to gather as many contributions as possible from students and postdocs of the AMS FoE and promote an exchange of ideas and networking. When you upload your poster information, please include a link to a one minute video presenting your poster and a link to the poster in pdf format.
Electron Transfer Reactions of Acylgermanes: A new Synthon for Custom-Made Photoinitiators
Abstract: Although heavier group 14 acyl-compounds seemed to play a minor role in research for a long time, such derivatives have gained attraction in the last few years, due to their superior properties for light-induced polymerization. Especially tetraacylgermanes stand out due to their high addition rates to the monomer and their high absorption intensities. Additionally, their good photobleaching together with their low toxicity restricts their potential not only to the use for microelectronic, adhesives and inks, but rather predestines them medical application (e.g. for dental fillings). However, a poor solubility in various monomers and a low curing depth still require an improvement.
The use of a tertiary solvent mixture to study solvent dynamic effects in the photoinduced electron transfer reaction of excited singlet pyrene and indole
Abstract: Photoinduced electron transfer (PET) plays an important role in many areas of chemistry. The physical properties of the solvent influence the rate constant of PET reactions in many ways. Classical electrodynamical de
Smart Core-Shell Nanostructures for Force, Humidity and Temperature Sensing
Abstract: The work summarized in this abstract presents a multi-stimuli responsive sensor for artificial skin applications. The sensor can detect surrounding changes in temperature, humidity and force. The developed design consists of a hydrogel core, responsive to temperature and humidity changes; and a piezoelectric shell for force sensing. Swelling of the hydrogel core, in response to stimuli, mechanically strains the piezoelectric shell and a measurable electric charge is generated. The two materials are combined into core-shell nanorod structures, using state-of-the-art vapor-based deposition techniques. These deposition techniques provide control over material’s mechanical, optical and electrical properties in addition to film’s conformity and uniformity. Moreover, the core-shell nanorods are deposited into a nanostructured UV-curable resin, providing mechanical stability against structural collapse.
Liquid Phase Deposition of Single-Source Precursors
Abstract: Recently, solution processing of silicon based electronic devices has attracted considerable attention. Especially the low costs and the possibility of large area depositions and patterning materials offer great advantage to similar processes. Recent studies demonstrated the principal feasibility of liquid phase deposition (LPD) and processing of silicon films of high quality. Therefore, the aim of this work was the synthesis of different heteroelement substituted higher silicon hydrides, which contain one or more heteroatoms covalently linked to silicon. The resulting materials are then applied as single source precursors for the deposition of functional silicon films. Therefore, different oligomeric compounds were synthesized by UV-activated oligomerization of neopentasilane, 2-methyl-2-silyltrisilane and 1,1,1-trimethyl-2,2-disilyltrisilane.
Flow localization during hot deformation of a Ti-17 alloy
Abstract: Flow localization occurs in titanium alloys during hot deformation. This phenomenon must be avoided to prevent damage and guarantee a correct material flow. In this work, a mesoscale physically-based hot deformation model that couples the microstructure and stress evolution was combined with a phenomenological flow localization model to correlate the thermomechanical history with the microstructure evolution and the susceptibility to flow localization during hot deformation. The onset of flow localization is related to a fast production of new dislocations and new high angle grain boundaries.
Tunable wettability of laser-induced graphene
Abstract: Laser-Induced Graphene (LIG) created by laser scribing on a polymer precursor like polyimide exhibits many interesting properties. Along with creating conductive patterns embedded in flexible substrates the wettability of these materials can be finely tuned by simply changing the IR laser processing parameters. The water contact angle (CA) of LIG could be tuned from a superhydrophilic state -with a CA φ = 0° - to a superhydrophobic state with a CA φ = 150°. Two different strategies were investigated: 1) tuning of the scribing pattern, 2) change of the O2 content of processing atmosphere through local air/N2 purging. The resulting CA of the different LIG types were investigated together with the chemical surface composition, measured by XPS (X-ray Photoelectron Spectroscopy). A correlation between the oxygen content of the surface and the CA could be observed. This opens up the possibility to manipulate and direct fluids on the LIG surface; demonstrators like a fluidic device were fabricated based on these findings. Inspired by the Namib desert beetle a biomimetic application in fog basking was demonstrated. Sheets of polyimide patterned with various types of LIG were used to collect water from fog, with a collection rate similar to other recent but more complicated approaches. An environmental scanning electron microscope (ESEM) was used to investigate the condensation and wetting of water on LIG at the microscale.
Structural evolution of dealloyed nanoporous copper from copper-manganese alloy
Abstract: Nanoporous electrode materials are highly promising for a broad variety of applications, such as catalysis, sensing, or energy storage due to their high surface-to-volume ratio, free standing porous structure, and freedom of design. The nanoporous structure is obtained by selective etching  of the less noble component of an alloy, so called dealloying. The most studied dealloyed materials are noble metals including nanoporous Au, Pt or Pd, but also nanoporous copper (npCu) is known in literature. Because of its low cost, mild fabrication conditions as well as mechanical and electrical properties, npCu is particularly interesting and gained a lot of research interest over the last years. However, the structural evolution is not yet fully understood.
Fatigue assessment of deep rolled components based on numerical analysis
Abstract: Weight reduction and associated increasing energy efficiency, enhanced service life and of course reduction of maintenance costs are requirements which are placed on the development of wheelset axles of railway vehicles. A manufacturing process that can contribute to fulfil these requirements is deep rolling. Thereby a deep rolling tool is pressed onto the rotating railway axle with a defined force at a constant feed rate. The surface material layer of the component is smoothed, work-hardened and residual compressive stresses are introduced into the area near the surface. Especially the residual compressive stresses, of course depending on the selection of process parameters, have a positive effect on the service life of the component. Within the framework of this PhD thesis a valid finite element simulation of the deep rolling process will be developed and necessary material investigations for the parametrization and validation will be carried out. Numerical parameter studies to analyse the main process influences, the transferability to real wheelset axles and the consideration of the deep rolling process in the fatigue design are the further main points of the thesis.
Unraveling the timescale of the structural photo-response within oriented Metal-Organic Framework films
Abstract: Fundamental knowledge on the intrinsic timescale of structural transformations in photo-switchable Metal-Organic Framework films, is crucial to tune their switching performance and to facilitate their applicability as stimuli-responsive materials. In this work, for the first time, an integrated approach to study and quantify the temporal evolution of structural transformations is demonstrated on an epitaxially oriented DMOF-1-on-MOF film system comprising azobenzene in the DMOF-1 pores (DMOF-1/AB). We employed time-resolved Grazing Incidence Wide-Angle X-Ray Scattering measurements (GIWAXS) to track the structural response of the DMOF-1/AB film upon altering the length of the azobenzene molecule by photo-isomerization (trans-to-cis, 343 nm; cis-to-trans, 450 nm). Within seconds, the DMOF-1/AB response occurred fully reversible and over several switching cycles by cooperative photo-switching of the entire oriented film, as confirmed further by infrared measurements. Our work thereby suggests a new avenue to elucidate the timescales and photo-switching characteristics in structur-ally responsive MOF film systems.
Tuning the Porosity of Zinc Oxide Thin Films Derived from Molecular Layer Deposited “Zincones”
Abstract: To establish metal-oxide thin films in crucial fields of application, such as microelectronics or energy conversion, an inexpensive synthesis technique is needed, which excels at scalability and controllability. These requirements are met by chemical vapor deposition methods, which allow for the synthesis of highly conformal layers with precise thickness control and excellent conformality. Additional benefits can be gained by introducing porosity into metal oxide thin films, as this significantly increases the available surface area.
Phenylene-Bridged Perylene Monoimides as Acceptors for Organic Solar Cells: A Study on the Structure–Property Relationship
Abstract: A series of non-fullerene acceptors based on perylene monoimides coupled in the peri position through phenylene linkers were synthesized via Suzuki-coupling reactions. Various substitution patterns were investigated using density functional theory (DFT) calculations in combination with experimental data to elucidate the geometry and their optical and electrochemical properties. Further investigations of the bulk properties with grazing incidence wide angle X-ray scattering (GIWAXS) gave insight into the stacking behavior of the acceptor thin films. Electrochemical and morphological properties correlate with the photovoltaic performance of devices with the polymeric donor PBDB-T and a maximum efficiency of 3.17 % was reached. The study gives detailed information about structure–property relationships of perylene-linker-perylene compounds.
Microstructure-dependent mesh for crack growth modeling in wheel-rail contacts
Abstract: Pearlitic steel is commonly used for wheels and rails in rail transport. This work focuses on the prediction of fatigue crack growth by considering microstructural details of pearlitic steel. Some microstructural properties like prior austenitic grain size, pearlitic colony size, and lamellae orientation as well as the effect of plastic deformation are implemented in the model explicitly by geometrical features of a hierarchical mesh. The meshes generated for this purpose are done based on the Voronoi Tessellation method. The mesh generated with this method shows a strong resemblance to the actual pearlitic microstructure both geometrically and statistically. The mesh can predict anisotropy of fatigue crack growth in different orientations.
Setting up a new dislocation creep model for Ni-based alloy 617
Abstract: Alloy 617 is a solid-solution strengthened (SSS), γ‘- and carbide-forming Ni-based alloy. It is a promising candidate for aircraft and power plant applications at 700°C and beyond. In this work, we present a new dislocation creep model for Ni-based alloys with a low γ‘ phase fraction (<10%) and apply it to A617 in a stress range of 165 to 200 MPa at 700°C. The model is capable of predicting creep strain and rupture times based on microstructural evolution, showing good agreement to measurements and literature data.
Material Compatibility Analysis of 316L, AlSi10Mg, AW 6063 and CuAl10Fe5Ni5 for PEM Fuel Cell System Application
Abstract: Four different materials, CuAl10Fe5Ni5, AlSi10Mg, AW 6063 and 316L, were investigated upon their compatibility within a proton exchange membrane fuel cell system.
Fatigue Behavior of Cord Rubber Composite Materials used in Air Spring Bellows
Abstract: In the chassis of a rail vehicle for passenger coaches and traction units, it is common to use air spring systems as secondary spring stages. In the development of spring stages, it is necessary, among other things, to have the most precise knowledge possible about the material properties of the air spring bellows at an early stage of the project. However, with the existing state of knowledge, empirical methods have to be used in most cases.
Design meets Alginate - Synergy of alginate and natural fibres
Abstract: The embodied carbon emissions from building materials and construction are today responsible for 38% of annual global GHG emissions in the current global environment. If we are to reach the European energy plan with net-zero emissions by 2050, now is the time to rethink our construction principles, as well as building elements and materials.
In operando monitoring templated electrodeposition of Pt films with hexagonal pore structure by GISAXS
Abstract: Liquid crystal (LC) templated electrodeposition is a facile and versatile method to electrodeposit metal films with highly structured mesopores. These mesopores are essential to increase surface area for electrocatalysis and sensing. Previous studies showed that LC templating allowed to tailor pore size, shape, and orientation of the pores in the deposited film. Generally, these studies suggest that the pores in the film inherit the structure of the LC template.
Thermo-responsive shape-memory EPDM/thermoplastic-blends
Abstract: Shape-memory polymers (SMPs) are a class of smart materials with the ability to recovery from one or more temporary shape deformations into a predetermined configuration upon exposure to external stimuli. Triggers include temperature changes, electricity, light or magnetism. Research on SMPs has been fueled by their potential applications in numerous fields. Within a variety of possible routes, polymer blending is a convenient approach to fabricate material systems exhibiting shape memory behavior.
Zinc oxide ALD growth on different substrates monitored by in-situ ellipsometry
Abstract: Atomic layer deposition (ALD) is a powerful technique to deposit highly conformal thin films with a thickness control in the Angstrom range. The technique is based on a cyclic process during which a precursor gas and a co-reactant are sequentially introduced into the deposition chamber. In our lab, we use oxygen plasma as the co-reactant, which is then commonly referred to as plasma-enhance atomic layer deposition (PE-ALD).
Wire-based electron beam additive manufacturing of NiTi shape memory alloy: influence of heat treatment on the functional behaviour
Abstract: The fabrication of Shape Memory Alloys (SMA) by wire-based electron beam additive manufacturing (w-EBAM) has started only recently. In previous studies, solidification aspects, comparison with other directed energy deposition techniques, and crystallographic aspects of the deposition along the building direction were clarified. Despite all the aforementioned cases that have assessed the manufactured material mechanically, one has to highlight the fact that the influence of thermal treatments on the functional behaviour is still scarce. Moreover, it is well known the influence of the precipitation caused by such treatments on the improvement of the superelastic effect, especially the coherent Ni4Ti3 particles. In this sense, it is fundamental to understand how w-EBAM fabrication may impact this metallurgical phenomenon as well as the mechanical behaviour. Therefore, the present work aims to shed light on the metallurgical behaviour of SMA fabricated by w-EBAM, investigating the functional properties and correlating their responses to thermal treatment time and temperature.
Transport of organic volatiles through paper: physics-informed neural networks for solving inverse and forward problems
Abstract: Transport of volatile organic compounds (VOCs) through porous media with active surfaces takes place in many important applications, such as in cellulose-based materials for packaging. Generally, it is a complex process that combines diffusion with sorption at any time. To date, the data needed to use and validate the mathematical models proposed in literature to describe the mentioned processes are scarce and have not been systematically compiled.
On the printability and superelasticity of NiTi shape memory alloy by selective laser melting with Ni-rich elementally blended powder
Abstract: The fabrication of NiTi shape memory alloy by laser powder bed fusion has gained much interest since NiTi shows a lack of machinability in terms of conventional routes. Previous studies successfully produced dense and defect-less NiTi with pre-alloyed powder; typically produced on a prior heated NiTi substrate plate. However, these pre-alloyed NiTi powders are costly and diﬃcult to produce due to their reactivity, becoming a drawback thus hindering NiTi application. For this reason, the achievement would be to produce high-quality parts by using elementally blended Ni and Ti powder printed on a dissimilar material substrate plate – such as titanium –, as a cost-effective alternative. Furthermore, the elementally blended powder gives freedom in varying chemical composition of the NiTi alloy since pre-alloyed powders have a ﬁxed narrow composition range. It is well known that the chemical composition of NiTi alloys influences mechanical behaviour such as the shape memory effect (SME) and superelasticity (SE). Therefore, the present work is focused on a process parameter study to correlate machine-related parameters with the printability and defects in the material additionally investigating its superelastic response.
INJECTION OVERMOULDED POLYMER-METAL HYBRID STRUCTURES
Abstract: Polymer-metal hybrid (PMH) structures are specially designed and manufactured to bring together the relevant characteristics of each component into a single structure. In this sense, these structures can combine the mechanical strength of metals with the lightness and durability of polymers. They are used in various sectors such as transportation, household appliances, energy and biomedical. Metal insert injection over-molding is an important technique for assembling polymer-metal hybrid structures. It is based on the injection molding of thermoplastics, an automated process that makes it possible to obtain parts with complex geometries and dimensional precision in very short molding cycles. In this context, hybrid structures of polycarbonate (PC) and aluminum alloy AA6061 were obtained by direct-adhesion injection over-molding. The surface of the AA6061 substrate was structured by laser under different conditions. The effects of laser speed and frequency on the depth of grooves drawn on the surface of the aluminum substrate were evaluated and a correlation with the lap-shear strength of half-lap splice PC/AA6061 joints was obtained. A strong joint with maximum lap shear strength of 6.2 0.3 MPa was reached.
Modelling the hot deformation of a microalloyed steel
Abstract: During the continuous casting process, alloys are exposed to mechanical and thermal stresses which might lead to damage. The strain hardening effect and dynamic softening behavior of a microalloyed steel are correlated to the damage behavior occurring during hot deformation.
Studies of Ionizing Radiation Effects in Nano-Scale CMOS (SIRENS)
Abstract: High energy physics experiments are creating an increasing demand for integrated circuits (ICs) that can reliably work at higher frequencies, with smaller signal levels and under the influence of large doses of high energy radiation. A leading example of this trend is the next upgrade of large hadron collider (LHC) at Conseil Européen pour la Recherche Nucléaire (CERN). The integrated circuit technologies used in applications with high energy radiation environment have to be carefully selected and characterized both at single transistor and circuit level. The focus of this project is to examine total ionizing dose (TID) influence on 28 nm and 40 nm CMOS "high-dielectric-constant-metal-gate" (high-K) technology nodes and establish reliable models for DC, 1/f noise and Random Telegraph Noise (RTN) behavior under different operating conditions.
In-situ alignment of dielectric fibers with electric fields in extrusion processes
Abstract: Biological systems found in nature exhibit highly complex hierarchically ordered 3D structures with many degrees of organization and functionalization to achieve their unique mechanical and biological properties. While biological systems grow theses anisotropic reinforcement architectures, the fiber alignment in polymer processing and especially 3D printing requires external forces such as shear force, electric – or magnetic fields and is often limited to specific scenarios.
Computer-aided topology optimization of through-the-thickness reinforcements for metal-composite hybrid joints produced via U-Joining
Abstract: This work presents an alternative for the topology optimization of the through-the-thickness reinforcements (TTRs) used for Ultrasonic Joining (U-Joining) of hybrid structures in lap-shear configuration. Hybrid joints were considered between stainless steel 316L and 20% short-carbon-fiber reinforced polyether-ether-ketone (PEEK-20CF). For the optimization, a finite element (FE) model was developed in Abaqus and implemented into an optimization workflow in ISight. Metallic samples featuring the optimized geometry were manufactured using laser powder bed fusion (LPBF), joined using U-Joining with a polymeric counterpart printed via fused filament fabrication (FFF), and tested. The obtained optimum geometry can reach a maximum force of 2940.0 N during loading (34% higher than standard TTRs) based on the simulation outcomes. With such geometry, full penetration into the polymer and total wetting of the metal surface was achieved during U-joining, demonstrating its overall suitability for this technique. Moreover, the lap-shear mechanical testing results indicated that the average maximum force that the optimized TTRs can reach is 2746.3 N, which showed good agreement with the simulation results.
Optimization of metal-polymer hybrid joints fully produced by Additive Manufacturing using Decision Tree Algorithm
Abstract: The advantages provided by Additive Manufacturing (AM) techniques for both metals and polymers with respect to possible part geometries and reduction of manufacturing steps are well known. However, coupling different AM techniques to produce polymer-metal hybrid is yet to be thoroughly explored. While conventional joining technologies such as fastening and adhesive bonding would be capable of joining polymer and metal AM parts, this work aims towards using AM itself as a joining technology for that. Known as AddJoining, this approach resorts to Fused-Filament Fabrication (FFF) principles to manufacture parts directly onto metallic substrates, dispensing any kind of joining step, fasteners or bolts. Since the AddJoining relies on the hot, softened extruded polymer flowing through surface irregularities, using a substrate with an appropriate roughness is important. In a scenario where the substrate has been produced by powder-based AM techniques, its as-printed surface (which normally would need to be milled out for most applications) can be utilized to provide anchoring spots for the semi-liquid extruded polymer. The objective of this work is to evaluate the influence of the as-printed surface roughness, as well of subsequent FFF parameters on the strength of Ti-6Al-4V/PA-CF joints produced by AddJoining. In order to test the joints, a 3-point bending method based on ISO 14679:1997 standard was deployed. The roughness was varied by 3D-printing the substrate with different leaning angles (from 40 to 90 degrees). As for the polymer part, layer height and printing speed of the coating layer (the polymer layer immediately in contact with the metal) were also varied. The influence of the aforementioned parameters on the bending force was interpreted using single Decision Tree Regression, as well as Ensemble methods combining several trees to produce better predictive performance (e.g. Random Forests, Adaboost, Bagging, etc.). Random Forests was deemed to be the most promising model, to which further hyperparameter tuning was conducted. As a result, a coefficient of determination (R2) of 0.97 was obtained for both training and test sets . The model clearly suggests that printing speed is the prominent parameter followed by leaning angle. Additionally, the combined effect of low printing speed and leaning angle yield the highest bending force. This result is agreement with experimental trials.
PRODUCTION OF BORON-MODIFIED STAINLESS-STEEL POWDERS FOR LASER POWDER BED FUSION
Abstract: Metallic components employed in harsh applications in the oil & gas, marine, and chemical industries are subjected to surface degradation such as wear and corrosion. Stainless steel alloys are corrosion-resistant, but not considered as significantly wear-resistant. Addition of high boron contents (0.3–4 wt.%) has demonstrated to be effective to enhance the hardness and wear resistance of stainless steels due to the formation of hard and rigid borides. However, due to low machinability of these alloys, the manufacture of components with complex geometries is difficult. Hence, laser powder bed fusion (L-PBF) process is an interesting additive manufacturing route for boron-modified stainless steels, since it is possible to produce near-net-shape components with a variety of dimensions and geometries. Moreover the process offers the possibility to control printed part’s microstructure by adjusting the processing parameters, with reduced waste of material, and the possibility to produce and/or repair specific components in a short time. This study reports the production of boron-modified stainless-steel powders by gas atomization focusing on its application in the production of parts by L-PBF. Current studies at TU Graz are addressing the L-BPF-parameters optimization, and the systematic analyzes of the microstructure, mechanical, wear and corrosion resistance of the printed parts.
The effect of an in-situ consolidation process on the microstructure of additive manufactured continuous carbon fiber reinforced polyamide 6 material.
Abstract: The additive manufacturing (AM) of continuous fiber reinforced composites (CFC) is becoming increasingly important in the field of lightweight construction. The major advantage lies particular in the automated manufacturing process and in the production of complex geometries. Recent works on AM CFCs printed by traditional fusion filament fabrication (FFF) have revealed increased consolidation-related volumetric flaws -i.e. deconsolidation defects decreasing mechanical performance. The presence of deconsolidation defects, normally indicates either poor process parameters selection or inadequate in situ consolidation. This work is an intrinsic characteristic of traditional FFF, where there is no application of additional in situ consolidation pressure. Recently, there were several efforts in modifying the FFF of CFCs to minimize deconsolidation defects through in situ thermo-mechanical pressing. However, there are only limited fundamental knowledge on the in situ thermo-mechanical consolidation of FFF-CFCs. This work analyses the stated problem and proposes ways to decrease deconsolidation in FFF CF-PA6 laminates. For this purpose we used a self-developed FFF printing head coupled with a thermo-mechanical pressing unit. The influence of extrusion-, consolidation temperature, printing speed and in situ consolidation pressure on laminate microstructure and flexural strength was investigated. A comparison with FFF laminates printed in a common 3D printer was performed.
Azacryptand-based Dinuclear Rare-Earth Metal Compounds: A Platform for Cooperative Chemistry
Abstract: Rare-earth metals are essential in numerous technological applications due to their magnetic and photophysical properties. Playing key roles in electric vehicle motors and wind turbines, an average smartphone for instance contains around eight different rare-earth metals with applications in color displays, touch screens, vibration motors, and speakers. On the level of coordination chemistry rare-earth metal are on the forefront of small molecule activation such as dinitrogen and carbon oxides. Activation of these gases, which are key in the in the production of chemical products like fertilizers and synthetic hydrocarbons, is typically accomplished by two rare-earth metal centers working together.
Investigation on the optoelectronic properties and photo-degradation of PM6:Y6 organic solar cells and their correlation to the device architecture
Abstract: PM6:Y6 based solar cells have emerged as some of the best performing organic solar cells in the last five years: not only their power conversion efficiencies (PCEs) are among the highest performances reported so far, but, under optimized fabrication conditions, PM6:Y6 blends have also shown outstanding photo- and storage stability.
Preparation of honeycomb-structured metal sulfide thin films via polystyrene microsphere templates
Abstract: Metal sulfides currently experience increased interest due to their well-suited properties for a broad area of applications such as photovoltaics, photocatalysis, or energy storage. In literature, there are many reports for the synthesis, characterization and application of metal sulfide films, but only a few deal with structured metal sulfide films. Most of the routes towards structured metal sulfides employ templates. There are two main template-assisted methods, the soft-templating with directing agents, such as lyotropic liquid crystalline templates, and the hard-templating with templates such as mesoporous silica. Nanosphere colloidal lithography is a technique that is classified in the soft-templating technique and utilizes monodispersed colloidal particles, such as polystyrene microspheres (PS-MS), as template for the formation of periodically ordered arrays.
A micromechanical model of cellulosic foams – validation and results of first parametric studies
Abstract: Cellulosic network structures are a potential sustainable and ecological alternative to current synthetic foams. The EU funded project ‘BreadCell’ explores porous cellulosic structures generated through a biological foaming process employing yeasts.
Corrosion resistance of cast AlSi10MgCu(x) alloys
Abstract: Aluminium has a high strength-to-weight ration making it an attractive alloy for automotive industry. Among the aluminium alloys, cast Al-Si-Mg are typically used in near net-to-shape components, such as engines and motors. Currently, recyclability is of great importance. Although aluminium can be easily recycled, contamination intake can occur. The typical ones are iron, manganese and copper. Copper is typically added in aluminium alloys to increase the strength but it decreases the corrosion resistance. In this work the effect of the added copper on the corrosion resistance is examined on AlSi10Mg alloys with different copper concentrations. Salt spray measurements were conducted to determine the corrosion rate and electrochemical tests were performed to investigate the corrosion behaviour. With linear polarization measurements the corrosion current was examined while impedance measurements were conducted to simulate and better understand the aluminium dissolution process. Finally, the effect of copper on the corrosion degradation of the AlSi10Mg alloys is determined.
The Characterisation of Materials at High Strain Rates with a Universal Split Hopkinson Bar System
Abstract: The mechanical response of most materials is significantly influenced by the applied loading-rate. Knowlegde on the strain-rate dependency of strength- and stiffness-values as well as on damage accumulation is relevant for a mulititude of engineering problems, like metal forming, vehicle crash safety, or bird strike impact tolerance on airplanes.
Solvent-Free Amide Bond Formation using a variety of Methoxysilanes as Coupling Agent
Abstract: Amide bond formation is one of the cornerstones of organic chemistry. Amide bonds are found in a variety of products like pharmaceuticals and polymers. About 25% of all pharmaceuticals currently contain an amide bond. Due to this the investigation of alternative coupling reagents is an important task in contemporary chemistry. In this context silane-mediated coupling has become popular over the past few years, owing their low toxicity and good availability. We investigated the reaction of different carboxylic acids with primary and secondary amines with tetramethyoxysilane 1, hexamethoxydisilane 2 and dodecamethoxyneopentasilane 3 as coupling agent (Scheme 1). Moreover, we implimented that the reaction can be performed solvent free and without exclusion of air and moisture.
Additive manufacturing of an Fe-Cr-Co permanent magnet alloy with a novel approach of in-situ alloying
Abstract: In recent years, the method of additive manufacturing has become more and more important in the production of magnetic materials due to higher demands for miniaturisation and complex- shaped magnet parts. With the method of Laser beam- powder bed fusion (LB-PBF), an in- situ alloying process for the additive manufacturing of the Fe-Cr-Co system has been developed. With this novel method the production of complex alloys with a composition accustomed to each specific case of application can be achieved directly in the printing chamber by the use of elemental powders or simpler commercial alloy powders as base materials.
High entropy alloys produced by laser powder bed fusion assisted by in-situ alloying
Abstract: High-entropy alloys (HEAs) are materials of interest due to their excellent mechanical properties such as high strength and high ductility under both cryogenic- and high-temperature conditions. Currently, their production on an industrial scale is still being established. Innovative manufacturing techniques can facilitate the production of HEA structural parts. Additive manufacturing combined with in-situ alloying enables the production of complex alloys using high-quality powders of pure individual elements or pre-alloyed powders. Laser Powder Bed Fusion enables the production of complex shapes with internal closed fine features, which are not feasible via any other state-of-the-art metal formative or subtractive process. With this technique, various adjustable process conditions are possible due to the wide range of possible printing parameters. In this work, high entropy alloys are produced using laser powder bed fusion assisted by in-situ alloying. The microstructure is characterised and correlated to the main printing parameters. Moreover, the relations between crystallographic textures and printing parameters are inferred. The partial powder melting inherent from the in-situ alloying method and the micro-segregation due to laser powder bed fusion are successfully minimised with solution heat treatments.
Wire-Based Additive Manufacturing of Tungsten
Abstract: In present study, the feasibility of wire-based additive manufacturing of commercially pure tungsten using electron beam technique could be demonstrated. Three different representative volumetric AM structures were built and subsequently characterized. The parts show a sound visual appearance with the absence of (macroscopic-) cracks or severe distortion. The fabricated parts exhibit high density and the value depends on the welding sequence applied. The mean hardness value of the fabricated AM structures is about 366 - 380 HV1 and is in the range of about 89 - 93% of the conventionally fabricated substrate. Microstructural changes for all AM structures could be observed; a coarsening of the grains from the bottom to the top and a change in morphology can be noted for all AM structures.
Physical upset butt welding simulation for high performance Q&T steels
Abstract: High-performance Q&T steels are widely used for steel chains and therefore the chain joining process has to be taken into account in an early stage of development of new steel grades. To guarantee high availability and cost efficiency, a scheme for the physical welding simulation of the upset butt welding process was elaborated within this study by applying it to the Q&T steel 23MnNiCrMo5-2. By conducting thermo-mechanical simulations on the Gleeble® 3800 (Dynamic Systems Inc.) the influence of different process parameters on the joint performance could be determined. Furthermore, feasibility was shown for simulating the weld zone by conducting upset butt welding under controlled ambient influences by the use of the stated Gleeble® simulator. By establishing a suitable welding procedure with appropriate control parameters, high-quality joints with geometrical features and microstructure, comparable to the industrial welding process, could be observed.
Ultrasonic joining parameters optimization and surface corrosion behavior of additively manufactured 316L and PEEK-20CF hybrid structures
Abstract: Ultrasonic Joining (U-Joining) is a novel friction-based joining technique capable of producing through-the-thickness reinforced (TTRs) hybrid joints between surface-structured metals and unreinforced/fiber-reinforced thermoplastics. The process feasibility has been successfully demonstrated and optimized to join injection-molded Ti-4Al-6V and extruded unreinforced and glass-fiber-reinforced polyetherimide parts, resulting in joints with improved quasi-static out-of-plane mechanical properties. In addition, a previous study explored the joining process of additively manufactured 316L stainless steel with 20% short-carbon-fiber reinforced poly-ether-ether-ketone (PEEK-20CF). However, further investigation of joining process parameters’ effect on joint mechanical performance is needed to understand joint formation and strength. This work intends to evaluate the influence of U-Joining parameters on the mechanical performance and surface corrosion behavior of laser powder bed fusion (LPBF) printed 316L stainless steel and fused filament fabricated (FFF) PEEK-20CF hybrid single-lap joints. The joining parameters were optimized through Design of Experiments (DoE) to maximize the single-lap joint ultimate lap shear force (ULSF). Furthermore, the corrosion behavior of optimized joints was analyzed via potentiodynamic polarization techniques performed in simulated seawater saline corrosion medium (3.5 wt.% NaCl). The obtained results showed that the mechanical performance of the produced joints strongly depends on the joining energy and pressure. In addition, a similar corrosion behavior was observed between the as-built base material and optimized joined hybrid parts, indicating that U-Joining is suitable for transportation applications since it is not detrimental to the corrosion resistance of the investigated materials.
Dissimilar joints of additive manufactured and wrought aluminium alloy produced by refill friction stir spot welding
Abstract: With refill friction stir spot welding (RFSSW) solid-state joining of aluminium alloys, not weldable with fusion-based processes, is possible. Hence the process is used in this study to join AlSi10Mg, processed by laser powder bed fusion (LPBF), with high-strength wrought alloy AA7075-T6. Rotational speed was varied to investigate different heat inputs at constant plunge depth and welding time. The investigation showed the best mechanical properties and integrity for medium heat input joints, where the best balance between hook height and integrity was observed. The feasibility of RFSSW for joining AlSi10Mg with high strength wrought alloys was confirmed showing high potential for further investigations and industrial applications.