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      25
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    From Plasticity to Entropic Recovery - Investigating Reversible Deformation Mechanisms in Thermosets through Spectroscopy and Molecular Modeling
    Epoxy resins generally behave rather brittle, but microscale samples show increased ductility. Thin epoxy films (<100 µm) exhibit pronounced ductility, localized shear bands and mechanically induced necking under tensile load. The formation of shear bands was identified as a cascade of macromolecular mechanisms involving polymer chain stretching, orientation and molecular bond stretching. This interplay of structural reorganizations under tensile loading characterizes the emergence of localized network adaptations and provides a central contribution to the understanding of ductile deformation. These findings raise fundamental questions about the physical prerequisites of plastic deformation in amorphous, close-meshed polymer networks. In particular, it must be clarified whether irreversible plastic network adaptations are involved or whether reversible viscoelastic relaxation processes predominate, which could be understood under thermal activation procedures. Epoxy films of different chemical compositions and reproducible sample thickness are investigated in terms of mechanical deformation using in-situ infrared spectroscopy. The focus is on spectral shifts of aromatic groups of the polymer backbones, especially within the para-substituted phenylene groups, which show stress sensitivity at the molecular level. The resulting peak shifts correlate with macroscopically visible deformation zones, which allow conclusions regarding intermolecular interactions, local orientation and potential network relaxations. Complementary to this, Molecular Dynamics Simulations, supported by AI-based spectrum predictions, allow a direct assignment of vibrations to intra- and intermolecular structural motifs. The elastic response of the polymer networks and thermally induced recovery processes are investigated. The targeted comparison of different network architectures allows an evaluation of the role of molecular connectivity and local mobility for the observed ductility. Temperature-controlled post-treatments are used to test the extent to which mechanically induced structural changes relax due to thermal activation and whether a complete regression of the initial state can be observed. The interplay of mechanical loading, molecular reorganization and thermal recovery facilitates to differentiate between reversible network mobility and irreversible plastic restructuring. The combination of experimental observations with simulation-based structure-property correlations enables a profound understanding of those molecular mechanisms. This knowledge creates the basis for the development of structurally adaptive, energy-absorbing and reusable thermoset materials for demanding technical applications.
      53
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    EXC 3120 BlueMat - Research Topic D1: Energy Storage in Supercapacitors
    We will create advanced electrochemical double-layer capacitors (EDLCs) using environmentally friendly materials and aqueous electrolytes. These supercapacitors, known for their rapid charging rates, high power density, and long cycle life, demand high-performance electrolytes and electrode materials. To prevent electrolyte decomposition, we will study high-concentration water-in-salt solutions and strong confinement. A combination of electrochemical studies, advanced in-situ/in-operando techniques, and molecular modeling will help us to understand the hydration/dehydration processes and ion transport dynamics, which are crucial for forming and structuring the EDL. Additionally, we introduce the consideration of the role of strong confinement on the electrolyte dielectric properties and optimize the microstructure of nanoporous carbons and clay-carbon composites to achieve highly energy-dense supercapacitors. Key scientific questions include: How does ion hydration influence EDL structure? Is there a specific dehydration mechanism for ions? How can ion-ion interactions be tuned, and how do they affect EDL formation? What is the impact of carbon porosity on the performance of waterin- salt electrolytes in EDLCs? Is there a correlation between the degree of carbon graphitization and EDL structure? How do the dielectric properties water and electrolyte solutions change with strong confinement in natural 2D materials?
      61
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    EXC 3120 BlueMat - Research Topic B2: Selective Electrosorption
    Reversible electrochemical processes offer promising options in water treatment for removing oxyanions, dissolved organic carbon, and partial desalination by ion adsorption. Sorbent effectiveness depends on pore size, volume, surface area, and charge. However, current electrode fabrication processes limit control over multiscale porosity and surface charge, reducing their effectiveness in selective ion removal. Additionally, these properties are static, limiting adaptivity to avoid clogging and the ability to switch between adsorption and desorption. This RT advances the field by tailoring multiscale porosity of material systems for utilization as selective ion adsorbents and membrane filters. Innovative control of adsorption and desorption via adjustable surface potentials and selective ion sorption will transform materials into reversible, selective electrosorption systems. This facilitates strategic ion removal with low energy consumption, like lithium from seawater, marking a significant leap in harvesting engineering-valuable elements. The key scientific questions are: How can we functionalize 3D structured materials with locally and reversibly tunable adsorption and desorption of water-dissolved ions? How can we study the ion structure (+ hydration shell) and the spatiotemporal ion concentration evolution under electric potential and external flow, as well as the coupling of both, in a multiscale porous medium? How can we use multiscale modeling for functional optimization of materials for fast ion adsorption and desorption and low electrode degeneration rates resulting either in selective removal (water treatment) or selective ion (element) harvesting?
      66
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    EXC 3120 BlueMat - Research Topic D2: All-Water Redox Batteries
    D2 focuses on pioneering new battery solutions using water-based electrolytes and elucidating the critical interactions between water and aqueous electrolyte components at electrified interfaces. We will investigate the interactions between novel electrode materials and water within the context of battery technology. Our approach integrates advanced in-situ and in-operando characterization of material interfaces with modeling to bridge theoretical predictions and experimental observations. Such batteries use zinc metal anodes and cathodes with materials capable of intercalating anions. Dual ion batteries (DIBs) have a high energy density and relatively low cost, making them promising for use in various devices. By understanding the dynamic interactions of water within the pores of hierarchically structured cathode materials combined with layered double hydroxides (LDH), we aim to gain insights into the electrochemical performance and stability of these materials. On the anode side, we will explore the dynamic interactions of water during charge/discharge cycles and the effects of electrolyte additives on Zn dendrite formation. Key scientific questions include: What are new efficient electrolyte additives capable of controling charge/discharge processes on metallic Zn anodes? What is the mechanism at the atomistic scale? How can we develop the effective anion intercalation cathode assembled on hierarchically designed current collectors and open a pathway for the implementation of DIBs? What is the role of water in the ion-exchange processes and in the charge transfer within double hydroxide layers and in the interlayer spaces?
      58
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    Interaction between matrix, semi-finished product and component properties of processing-optimized furan resin prepregs
    Furan resins based on furfuryl alcohols (polyfurfuryl alcohols) represent an ecologically significant alternative to petrochemical thermosets such as phenolic resins as they are entirely based on renewable raw materials. However, the great ecological and material potential of furan resins for their use as matrix materials in fiber-reinforced plastics (high resistance to heat, chemicals and corrosion, good mechanical properties, advantageous fire behavior, etc.) is not yet being exploited to an economically relevant extent. In particular, the release of water during curing associated with polycondensation is critical and leads to composite parts either being cured very slowly or exhibiting a high degree of porosity, which greatly reduces the mechanical performance. For the research project within the Walter Benjamin-Program, it is hypothesized that purposive pre-curing (B-staging) of furan resin-based semi-finished fiber products (prepregs and towpregs) can reduce the release of water and the associated component porosity to such an extent that components with high thermo-mechanical properties can be produced by short cure cycles. At the same time, however, processing-relevant properties are to be maintained or optimized. As a result, an optimization problem is faced that requires an interdisciplinary approach from polymer chemistry, production engineering and materials science using experiments and material modelling methods. Based on the presented research approach, the overarching project objective persists in the exploration of interactions during the development of furan resin-based prepregs and towpregs with optimized processing properties. This results in two sub-goals to be achieved for the successful implementation of the project: Sub-goal 1 consists in producing the processable semi-finished product by varying the catalyst content, toughening content and B-staging levels. Therefore, model resins made from furfuryl alcohol, maleic anhydride and epoxidized soybean oil are formulated and characterized. The resins are used in combination with a glass fiber reinforcement for the production of semi-finished products and transferred to a defined B-stage based on a modeling approach (cure kinetics). Sub-objective 2 comprises exploring the influence of variation on the processing and component properties achieved. For this purpose, drapability, tack and shelf life are characterized in the B-stage and curing cycles are derived. Cured laminates are used for mechanical characterization with regard to tensile properties, interlaminar shear strength and impact strength as well as for the analysis of porosity and fire resistance.
      59
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    SPP 2240: Multistep Bioelectrochemical Reaction Cascade in Continuously Operated Flow Reactors
    The main objective of this project is to elucidate the key scientific questions to enable multistep bioelectrochemical reaction cascades in continuously operated flow reactors. The transition from AiO electrode setup in a batch to a continuously operated bioelectrochemical process starts from the established one-step bioelectrochemical system in the first project phase. This will be extended to a three-step bioelectrochemical reaction cascade, the oxidative valorization of 5-hydroxymethylfurfural (HMF) to valuable 2,5-furandicarboxylic acid (FDCA) catalyzed by two different unspecific peroxygenases (UPO). This cascade setup will allow the detailed study of different steady-state conditions through different reactor configurations, operating points as well as systematic properties of enzyme/electrode interactions. The reactor cascade can be operated with immobilized UPOs on the electrode surface as a sequence of plug flow reactors (PFR) as well as circulation loop reactors in continuously operated stirred tank reactor mode (CSTR). Alternatively, homogeneously solubilized UPOs can be applied that are recycled via an additional ultrafiltration membrane unit in the recirculation stream. By these two fundamental different reactor cascade configurations, a deepened understanding on affecting key performance parameters will be generated. Furthermore, challenges pointed out in the previous project will be addressed by designing improved porous Globugraphite (GG) electrodes. Key objective is to improve H₂O₂ productivity and Faradaic efficiency (F.E.). Several approaches will be explored, such as varying the polyvinyl butyral (PVB) content to influence the porosity of the GG and implementing multiple segmented GG modules. The latter ones might be separated by isolation or connected as units of different porosity. This will allow for a gradient of the H₂O₂ generation rate needed in a PFR setup to minimize H₂O₂ accumulation and enzyme deactivation. The following key scientific questions will be addressed: • How do the flow reactor geometry and increased flow rate influence mass transfer across/through the electrode, possible diffusion limitation as well as enzyme stability? • How does the morphology of the GG need to be varied by polyvinyl butyral (PVB) content, ZnO particle size and wall thickness to affect pore size in a way to maximize / tailor H₂O₂ productivity and F.E.? • How can the durability of GG electrodes be increased by thermal treatment and/or wall thickness to withstand the internal gas pressure? • How is a segmented graphite electrode to be designed to enable a length gradient in H₂O₂ generation rate? • How do different reactor operation modes (e.g. batch, PFR, CSTR) and resulting different linear flow rates influence performance indicators such as total turnover number (TTN), turnover frequency (TOF), enzyme deactivation constants and productivity?
      136
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    CRC 1615 - Project A06: Development of novel, highly active, and selective multifunctional carbon nanotube-supported catalysts for the chemical hydrogenolysis of glycerol to 1,2 propanediol
    In this project, CNT-supported catalysts for hydrogenolysis are developed and optimised. First, the multifunctional carbon nanotube-supported catalyst is optimized with respect to its activity by incorporating additional transition metals. The application and fabrication of CNT forests on glass will be investigated and adjusted in parallel. Subsequently, this synthesis method is applied to 3D-printed metal surfaces, which serve as support material for the catalyst. The resulting catalyst will then be subjected to in-depth reaction engineering studies. Continuous characterization of the obtained products will be carried out during the whole project.
      164
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    CRC 1615 - Project A05: Tailored functional electrode structures for SMART bioreactors
    New carbon foam electrodes will be developed based on a ceramic template CVD process. By tailoring a porous microstructure for optimal microorganism activity and biofilm growths measured by small flow cell reactors for rapid testing of small electrode samples. To propose generic rules for the prediction of microbe electrode interactions, we will elucidate the molecular basis of the cellular response to the different materials using transcriptomic analyses. With a promising subset of materials, we aim for a first upscaling step in a plug flow reactor system with a reactor volume of up to 5 litres.
      171
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    Damage-tolerant, delamination-free high-performance fibre-reinforced polymer composites
    The multi-scale, anisotropic structure of fibre-reinforced polymer composites (FRP) leads to complex failure behaviour. Thus, different types of failure occur and the matrix failure at the micro level influences the failure process at all higher levels of observation. Delamination refers to the layer separation (delamination) of differently oriented layers in an FRP and is a critical failure mode as it leads to a significant reduction in the load-bearing capacity of the laminates, especially under compressive loading or loads outside the laminate plane. Thin-ply refers to composites with a layer thickness less than 60 m. Quasi-static UD tensile tests on unnotched, multidirectional thin-ply laminates have shown that the initiation of matrix cracking is delayed until just before complete fracture, significantly increasing strength. However, suppression of matrix damage results in a significant reduction in the strength of notched laminates, as no degradation of stress concentrations due to delamination occurs. The suppression of matrix damage in thin-ply laminates also affects the resulting damage from low velocity impact loading. However, thin-ply laminates also allow completely new approaches to influence the failure behaviour due to the extended degrees of freedom in the design of the layer structure. Thus, a new approach to influencing the damage behaviour of FRP is the use of novel, nature-inspired layer structures. Promising are helicoidal layer structures found in impact-loaded body parts of crustaceans, so-called Bouligand structures.As shown in the applicant's preliminary work, the use of bio-inspired helicoidal ply structures can control the failure behaviour of FRP such that delamination is completely suppressed and only subcritical matrix damage occurs before ultimate failure:- Delamination-free ply constructions can be realised by thin-ply and small angles between the plies.- Layer build-ups with almost no notch effect can be achieved by thin-ply and small layer angles.- The residual strength after impact damage was improved by 15% compared to conventional laminate structures.However, questions also arise from the results:- How thin must the single ply be and how small must the angle between the plies be to take full advantage of the effects? It must be taken into account that these geometric factors are essentially determined by the stiffness of the fibres and the interlaminar energy release rate GIIc.- What are the critical angle and the boundary layer thickness at which the damage mode changes from subcritical matrix cracking to interlaminar delamination?This research project aims to fully understand the mechanical behaviour of helicoidal laminate structures and to model the behaviour in order to reduce the high experimental effort and thus make helicoidal laminates technically usable.
      315