Universität Stuttgart
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Item Open Access Field evaporation and atom probe tomography of pure water tips(2020) Schwarz, T. M.; Weikum, E. M.; Meng, K.; Hadjixenophontos, E.; Dietrich, C. A.; Kästner, J.; Stender, P.; Schmitz, G.Measuring biological samples by atom probe tomography (APT) in their natural environment, i.e. aqueous solution, would take this analytical method, which is currently well established for metals, semi-conductive materials and non-metals, to a new level. It would give information about the 3D chemical structure of biological systems, which could enable unprecedented insights into biological systems and processes, such as virus protein interactions. For this future aim, we present as a first essential step the APT analysis of pure water (Milli-Q) which is the main component of biological systems. After Cryo-preparation, nanometric water tips are field evaporated with assistance by short laser pulses. The obtained data sets of several tens of millions of atoms reveal a complex evaporation behavior. Understanding the field evaporation process of water is fundamental for the measurement of more complex biological systems. For the identification of the individual signals in the mass spectrum, DFT calculations were performed to prove the stability of the detected molecules.Item Open Access Adjustable polystyrene nanoparticle templates for the production of mesoporous foams and ZnO inverse opals(2020) Abitaev, Karina; Qawasmi, Yaseen; Atanasova, Petia; Dargel, Carina; Bill, Joachim; Hellweg, Thomas; Sottmann, ThomasThe manifold applications of porous materials, such as in storage, separation, and catalysis, have led to an enormous interest in their cost-efficient preparation. A promising strategy to obtain porous materials with adjustable pore size and morphology is to use templates exhibiting the appropriate nanostructure. In this study, close-packed polystyrene (PS) nanoparticles, synthesized by emulsion polymerization, were used to produce porous PS and ZnO inverse opals. The size and distribution of the polystyrene nanoparticles, characterized by dynamic light scattering (DLS), small-angle neutron scattering (SANS), and scanning electron microscopy (SEM), were controlled via the concentration of sodium dodecyl sulfate (SDS). Systematic measurements of the water/styrene-interfacial tension show that the critical micelle concentration (CMC) of the ternary water–styrene–SDS system, which determines whether monodisperse or polydisperse PS particles are obtained, is considerably lower than that of the binary water–SDS system. The assemblies of close-packed PS nanoparticles obtained via drying were then studied by small-angle X-ray scattering (SAXS) and SEM. Both techniques prove that PS nanoparticles synthesized above the CMC result in a significantly unordered but denser packing of the particles. The polystyrene particles were subsequently used to produce porous polystyrene and ZnO inverse opals. While the former consists of micrometer-sized spherical pores surrounded by extended open-cellular regions of mesopores (Rpore ≈ 25 nm), the latter are made of ZnO-nanoparticles forming a structure of well-aligned interconnected pores.Item Open Access Identification of the first sulfobetaine hydrogel‐binding peptides via phage display assay(2023) Ihlenburg, Ramona B. J.; Petracek, David; Schrank, Paul; Davari, Mehdi D.; Taubert, Andreas; Rothenstein, DirkUsing the M13 phage display, a series of 7- and 12-mer peptides which interact with new sulfobetaine hydrogels are identified. Two peptides each from the 7- and 12-mer peptide libraries bind to the new sulfobetaine hydrogels with high affinity compared to the wild-type phage lacking a dedicated hydrogel binding peptide. This is the first report of peptides binding to zwitterionic sulfobetaine hydrogels and the study therefore opens up the pathway toward new phage or peptide/hydrogel hybrids with high application potential.Item Open Access Chemically induced local lattice distortions versus structural phase transformations in compositionally complex alloys(2021) Ikeda, Yuji; Gubaev, Konstantin; Neugebauer, Jörg; Grabowski, Blazej; Körmann, FritzRecent experiments show that the chemical composition of body-centered cubic (bcc) refractory high entropy alloys (HEAs) can be tuned to enable transformation-induced plasticity (TRIP), which significantly improves the ductility of these alloys. This calls for an accurate and efficient method to map the structural stability as a function of composition. A key challenge for atomistic simulations is to separate the structural transformation between the bcc and the ω phases from the intrinsic local lattice distortions in such chemically disordered alloys. To solve this issue, we develop a method that utilizes a symmetry analysis to detect differences in the crystal structures. Utilizing this method in combination with ab initio calculations, we demonstrate that local lattice distortions largely affect the phase stability of Ti-Zr-Hf-Ta and Ti-Zr-Nb-Hf-Ta HEAs. If relaxation effects are properly taken into account, the predicted compositions near the bcc–hcp energetic equilibrium are close to the experimental compositions, for which good strength and ductility due to the TRIP effect are observed.Item Open Access Slow‐moving phase boundary in Li4/3+xTi5/3O4(2021) Joshi, Yug; Lawitzki, Robert; Schmitz, GuidoLithium titanate is one of the most promising anode materials for high‐power demands but such applications desire a complete understanding of the kinetics of lithium transport. The poor diffusivity of lithium in the completely lithiated and delithiated (pseudo spinel) phases challenges to explain the high‐rate performance. This study aims at clearing the kinetics of lithium transport using an innovative technique that employs optical microscopy in a constrained region of sputter‐deposited thin‐film samples. It enables the in situ observation of the transport of lithium through the electrode. Furthermore, with a thermostatically controlled cell, the Arrhenius‐like temperature dependence is revealed. The quantitative findings demonstrate that indeed the end phases have poor diffusivity which is, however, accelerated at intermediate Li concentrations in the spinel structured Li4/3+δTi5/3O4 phase. Surprisingly, the slow migration of the phase boundary hinders the formation of the Li‐rich (rock‐salt) phase in the initial stages. Such kinetic control by the phase boundary stands in obvious contrast to a prior (theoretical) study postulating almost “liquid” behavior of the interface. Only after the Li diffusion into the Li‐poor (spinel) phase has faded, when approaching the solubility limit, the further growth of the rock‐salt phase becomes diffusion controlled.Item Open Access Recycling of all‐solid‐state Li‐ion batteries : a case study of the separation of individual components within a system composed of LTO, LLZTO and NMC(2023) Waidha, Aamir Iqbal; Salihovic, Amila; Jacob, Martine; Vanita, Vanita; Aktekin, Burak; Brix, Kristina; Wissel, Kerstin; Kautenburger, Ralf; Janek, Jürgen; Ensinger, Wolfgang; Clemens, OliverWith the current global projection of over 130 million electric vehicles (EVs), there soon will be a need for battery waste management. Especially for all‐solid‐state lithium‐ion batteries (lithium ASSBs), aspects of waste management and circular economy have not been addressed so far. Within such ASSBs, the use of solid‐electrolytes like garnet‐type Li6.5La3Zr1.5Ta0.5O12 (LLZTO) may shift focus on strategies to recover not only the transition metal elements but also elements like La/Zr/Ta. In this work, we present a two‐step recycling approach using citric acid as the leaching agent to separate and recover the individual components of a model cell comprising of Li4Ti5O12 (LTO) anode, Li6.5La3Zr1.5Ta0.5O12 (LLZTO) garnet electrolyte and LiNi1/3Mn1/3Co1/3O2 (NMC) cathode. We observe that by adjusting the concentration of citric acid, it was possible to separate the materials from each other without strong mixing of individual phases and also to maintain their principle performance characteristics. Thus, the process developed has a potential for upscaling and can guide towards considering separation capability of battery components in the development of lithium ASSBs.Item Open Access Bioinspired structure tailoring of tin oxide based materials for high capacity electrodes(2021) Jahnke, Timotheus; Bill, Joachim (Prof. Dr.)Item Open Access Hydrosilylation of alkynes under continuous flow using polyurethane‐based monolithic supports with tailored mesoporosity(2022) Acikalin, Hande; Panyam, Pradeep K. R.; Shaikh, Abdul Wasif; Wang, Dongren; Kousik, Shravan R.; Atanasova, Petia; Buchmeiser, Michael R.Non‐porous polyurethane‐based monoliths are prepared under solvent‐induced phase separation conditions. They possess low specific surface areas of 0.15 m2 g-1, pore volumes of 1 µL g-1, and a non‐permanent, solvent‐induced microporosity with pore dimensions ≤1 nm. Mesoporosity can be introduced by varying the monomers and solvents. A tuning of the average solubility parameter of the solvent mixture by increasing the macroporogen content results in a decrease in the volume fraction of micropores from 70% to 40% and an increase in the volume fraction of pores in the range of 1.7-9.6 nm from 22% to 41% with only minor changes in the volume fraction of larger mesopores in the range of 9.6–50 nm. The polymeric monoliths are functionalized with quaternary ammonium groups, which allowed for the immobilization of an ionic liquid that contained the ionic Rh‐catalyst [1‐(pyrid‐2‐yl)‐3‐mesityl)‐imidazol‐2‐ylidene))(η4‐1,5‐cyclooctadiene)Rh(I) tetrafluoroborate]. The supported catalyst is used in the hydrosilylation of 1‐alkynes with dimethylphenylsilane under continuous flow using methyl‐tert‐butyl ether as second liquid transport phase. E/Z‐selectivity in hydrosilylation is compared to the one of the analogous biphasic reactions. The strong increase in Z‐selectivity is attributed to a confinement effect provided by the small mesopores.Item Open Access Towards recycling of LLZO solid electrolyte exemplarily performed on LFP/LLZO/LTO cells(2022) Ali Nowroozi, Mohammad; Iqbal Waidha, Aamir; Jacob, Martine; Aken, Peter A. van; Predel, Felicitas; Ensinger, Wolfgang; Clemens, OliverAll‐solid‐state lithium ion batteries (ASS‐LIBs) are promising due to their safety and higher energy density as compared to that of conventional LIBs. Over the next few decades, tremendous amounts of spent ASS‐LIBs will reach the end of their cycle life and would require recycling in order to address the waste management issue along with reduced exploitation of rare elements. So far, only very limited studies have been conducted on recycling of ASS‐LIBS. Herein, we investigate the recycling of the Li7La3Zr2O12 (LLZO) solid‐state electrolyte in a LiFePO4/LLZO/Li4Ti5O12 system using a hydrometallurgical approach. Our results show that different concentration of the leaching solutions can significantly influence the final product of the recycling process. However, it was possible to recover relatively pure La2O3 and ZrO2 to re‐synthesize the cubic LLZO phase, whose high purity was confirmed by XRD measurements.Item Open Access Structural design of advanced electrodes employing nanostructured V2O5 nanofibers for metal-ion battery application(2021) Diem, Achim M.; Bill, Joachim (Prof. Dr.)