Hydrogen is an efficient, carbon-free and safe energy carrier. However, its compact and weight-efficient storage is an ongoing subject for research and development. Among the intensively investigated hydrogen storage materials, lithium aluminum hydride (LiAlH4) is an attractive candidate because of its high theoretical hydrogen density (volumetric: 96.7g H2/l material; gravimetric: 10.6 wt.%-H2) in combination with rather low decomposition temperatures (onset temperature <100°C after doping). Although the reversible dehydrogenation of LiAlH4 must be carried out with the help of organic solvent, LiAlH4 can serve as single-use hydrogen storage material for various special applications, for example, hydrogen fuel cell systems. This thesis deals with transition metal (TM)-doped LiAlH4 aiming at tailored dehydrogenation properties. The crystal structure and morphology of TM-doped LiAlH4 is characterized by XRD and SEM respectively. The positive effects of four dopants (NiCl2, TiCl3, ZrCl4 and TiCl4) on promoting the dehydrogenation kinetics of LiAlH4 are systematically studied by thermal analysis. Based on the state of each TM chloride (solid or liquid), three low-energy-input doping methods (1. ball-milling at low rotation speed; 2. manual grinding or magnetic stirring; 3. magnetic stirring in ethyl ether) are compared in order to prepare LiAlH4 with the maximum amount of hydrogen release in combination with fast dehydrogenation kinetics. The dehydrogenation properties of the TM-doped LiAlH4 powders are measured under isothermal conditions at 80°C at a H2 pressure of 1 bar, which is within the operating temperature range of proton exchange membrane (PEM) fuel cells, aiming at applications where the exhaust heat of the fuel cell is used to trigger the dehydrogenation of the hydrogen storage material. Furthermore, the mid-term dehydrogenation behavior of TM-doped LiAlH4 was monitored up to a few months in order to test its mid-term storability. In addition, the pelletization of TM-doped LiAlH4 is investigated aiming at a higher volumetric hydrogen storage capacity. The effects of compaction pressure, temperature and the H2 back-pressure on the dehydrogenation properties of TM-doped LiAlH4 pellets are systematically studied. Moreover, the volume change through dehydrogenation and the short-term storage of the TM-doped LiAlH4 pellets are discussed in view of practical applications for PEM fuel cell systems. / Wasserstoff ist ein effizienter, kohlenstofffreier und sicherer Energieträger. Jedoch die kompakte und gewichtseffiziente Speicherung ist ein permanentes Forschungs- und Entwicklungsthema. Unter den intensiv untersuchten Materialien für die Wasserstoffspeicherung ist aufgrund der hohen theoretischen Speicherdichte (volumetrisch: 96,7 g H2/L, gravimetrisch: 10.6 Gew.%-H2) in Kombination mit sehr niedrigen Zersetzungstemperaturen (Anfangstemperatur < 100°C nach Dotierung) Lithium Aluminiumhydrid (LiAlH4) ein vielversprechender Kandidat. Obwohl die reversible Dehydrierung von LiAlH4 mit Hilfe von organischen Lösungsmitteln durchgeführt werden muss, kann LiAlH4-Pulver als Einweg-Speichermaterial für verschiedene Anwendungen dienen, beispielsweise für Wasserstoff/Brennstoffzellensysteme. Diese Doktorarbeit beschäftigt sich mit LiAlH4 dotiert mit Übergangsmetall, mit dem Ziel maßgeschneiderte Dehydrierungseigenschaften zu erreichen. Die Kristallstruktur und die Morphologie der mit Übergangsmetallen dotierten LiAlH4-Pulver wurden mit Röntgenbeugung (XRD) und Rasterelektronenmikroskopie (REM) charakterisiert. Weiterhin wurde der positive Effekt der Dotanden auf die reaktionsfördernde Dehydrierung von LiAlH4 systematisch mit Hilfe thermoanalytischer Methoden untersucht. Für jedes Übergangsmetall, welches in Form von Übergangsmetallchloriden vorlag, wurden drei Dotierungsmethoden mit niedrigem Energieeintrag (Kugelmahlen mit geringer Rotations-geschwindigkeit, manuelles Schleifen/Magnetrühren, Magnetrühren mit Ethylether) verglichen, um LiAlH4-Pulver mit einer maximalen Wasserstofffreisetzungsmenge in Kombination mit einer schnellen Dehydrierungskinetik zu erzielen. Die Dehydrierung des dotierten LiAlH4-Pulvers wurde unter isothermen Bedingungen bei 80°C und einem H2-Druck von 1 bar gemessen, was im Bereich der Betriebstemperatur von PEM-Brennstoffzellen (Proton Exchange Membran) liegt. Dadurch sollen Anwendungen anvisiert werden, bei denen die entstehende Abwärme der Brennstoffzelle genutzt wird, um die Dehydrierung des Wasserstoffspeichermaterials auszulösen. Zudem wurde das Dehydrierungsverhalten des dotierten LiAlH4 bis zu einigen Monaten kontrolliert, um die mittelfristige Haltbarkeit zu testen. Weiterhin wurde die Pelletierung des mit Übergangsmetallen dotierten LiAlH4 mit dem Ziel untersucht, eine hohe volumetrische Speicherkapazität zu erreichen. Der Einfluss des Pressdrucks, der Dehydrierungstemperatur und des H2-Gegendrucks auf die Dehydrierungseigenschaften der mit Übergangsmetallen dotierten LiAlH4-Presslinge wurde systematisch analysiert. Außerdem wird die Volumenveränderung durch die Dehydrierung und die Kurzzeitspeicherung der mit Übergangsmetallen dotierten LiAlH4-Presslinge im Hinblick auf praktische Anwendungen unter Nutzung der Brennstoffzelle diskutiert.

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The present work is the fourth (and final) contribution to an inter-laboratory collaboration that was planned at the 3rd International Summit on Organic Photovoltaic Stability (ISOS-3). The collaboration involved six laboratories capable of producing seven distinct sets of OPV devices that were degraded under well-defined conditions in accordance with the ISOS-3 protocols. The degradation experiments lasted up to 1830 hours and involved more than 300 cells on more than 100 devices. The devices were analyzed and characterized at different points of their lifetimes by a large number of non-destructive and destructive techniques in order to identify specific degradation mechanisms responsible for the deterioration of the photovoltaic response. Work presented herein involves time-of-flight secondary ion mass spectrometry (TOF-SIMS) in order to study chemical degradation in-plane as well as in-depth in the organic solar cells. Various degradation mechanisms were investigated and correlated with cell performance. For example, photo-oxidation of the active material was quantitatively studied as a function of cell performance. The large variety of cell architectures used (some with and some without encapsulation) enabled valuable comparisons and important conclusions to be drawn on degradation behaviour. This comprehensive investigation of OPV stability has significantly advanced the understanding of degradation behaviour in OPV devices, which is an important step towards large scale application of organic solar cells. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

In this thesis, the effect of mechanical deformation on structure, thermal stability and hardness of a single-phase spray-deposited quasicrystalline alloy with composition Al62.5Cu25Fe12.5 has been investigated in detail. The purpose of the investigation was to study the effect of mechanical milling at different milling speeds (which approximately scale with the milling intensity) on mechanically-induced phase transformations during milling and on the phase evolution during subsequent heating. The results of the milling experiments indicate that, irrespective of the milling speeds used, mechanical milling of Al62.5Cu25Fe12.5 quasicrystals leads to the formation of a disordered CsCl-type ß phase with grain size of about 10 – 20 nm. The analysis of the kinetics of the QC–to–ß phase transformation reveals that the milling intensity has a considerable effect on the characteristics of the transformation. The increase of the milling speed considerably shortens the incubation time needed to start the QC–to–ß phase transformation. Also, the overall transformation is much faster for milling at high speeds. The QC–to–ß phase transformation starts when the grain size of the quasicrystals is reduced to about 10 nm irrespective of the milling speed used and clearly indicates that a critical grain size of the quasicrystals for initiating the transformation exists. On the other hand, no critical value of lattice strain was found for the QC–to–ß transformation. This indicates that the phase transformation is controlled by the local length scale (i.e. the grain size) and by the corresponding grain boundaries rather than by the energy stored in the lattice. Energetic considerations obtained through a simple model based on the mass and velocity of the milling balls reveal that the energy needed for the QC–to–ß transformation increases with increasing the milling speed, that is, the energetic efficiency of the process decreases with increasing the milling intensity. This indicates that part the extra energy supplied during milling at high intensities is not used to induce the phase transformation but it is dissipated by heat. During heating, the milled powder displays a multi-step thermal behavior characterized by the grain growth of the disordered ß phase at low temperatures, followed, at higher temperatures, by its transformation into the original icosahedral quasicrystalline phase. The transformation is gradual and the quasicrystals and the disordered ß phase coexist over a temperature interval of more than 250 K. The phase transformations occurring during milling and subsequent annealing have a remarkable effect on the hardness, which can be tuned within a wide range of values (7–9.6 GPa) as a function of the volume fraction of the different phases. This suggests that a composite material with optimized mechanical properties can be produced by an appropriate thermo-mechanical treatment. The quasicrystals milled at a very low speed show a transition between Hall-Petch to inverse Hall-Petch behavior at a grain size of about 40 nm, which represents the critical value for grain size softening of the present Al62.5Cu25Fe12.5 quasicrystals. This behavior may be attributed to the complexity of the quasicrystalline structure and to its peculiar deformation mechanism at room temperature (i.e. shear banding), where meta-dislocation-assisted deformation is almost absent. In order to analyze the effectiveness of the Al62.5Cu25Fe12.5 quasicrystals as reinforcing agent in metal matrix composites, Al-based composites were synthesized by hot extrusion of elemental Al blended with different amounts of Al62.5Cu25Fe12.5 quasicrystalline particles. The work was focused on two specific aspects: evaluation of the mechanical properties through room temperature compression tests and modeling of the resulting properties. The addition of the quasicrystalline reinforcement is very effective for improving the room temperature mechanical properties of pure Al. The compressive strength increases from 155 MPa for pure Al to 330 and 407 MPa for the composites with 20 and 40 vol.% of reinforcement, respectively, reaching an ultimate strain of 55 % and 20 % before fracture occurs. These results indicate that the addition of the QC reinforcement leads to composite materials with compressive strengths exceeding that of pure Al by a factor of 2 – 2.5, while retaining appreciable plastic deformation. The mechanical properties of the composites have been modeled by taking into account the combined effect of load bearing, dislocation strengthening and matrix ligament size effects. The calculations are in very good agreement with the experimental results and reveal that the reduction of the matrix ligament size, which results in a similar strengthening effect as that observed for grain refinement, is the main strengthening mechanism in the current composites. Finally, the interfacial reaction between the Al matrix and the QC reinforcement has been used to further enhance the strength of the composites through the formation of a new microstructure consisting of the Al matrix reinforced with Al7Cu2Fe w-phase particles. The optimization of the structure-property relationship was done through the systematic variation of the processing temperature during consolidation. The mechanical behavior of these transformation-strengthened composites is remarkably improved compared to the parent material. The yield strength of the composites significantly increases as the Al + QC -> ω transformation progresses from 195 MPa for the sample reinforced only with QC particles to 400 MPa for the material where the Al + QC -> ω reaction is complete. These results clearly demonstrate that powder metallurgy, i.e. powder synthesis by ball milling followed by consolidation into bulk specimens, is an attractive processing route for the production of novel and innovative lightweight composites characterized by high strength combined with considerable plastic deformation. In addition, these findings indicate that the mechanical behavior of Al-based composites reinforced with Al62.5Cu25Fe12.5 quasicrystalline particles can be tuned within a wide range of strength and plasticity depending on the volume fraction of the reinforcement as well as on the extent of the interfacial reaction between Al matrix and QC reinforcing particles.

Internalin J (InlJ) gehört zu der Klasse der bakteriellen, cysteinhaltigen (leucine-rich repeat) LRR Proteine. Bei den Internalinen handelt es sich um meist invasions-assoziierte Proteine der Listerien. Die LRR-Domäne von InlJ ist aus 15 regelmäßig wiederkehrenden, stark konservierten Sequenzeinheiten (repeats, 21 Aminosäuren) aufgebaut. Ein interessantes Detail dieses Internalins ist das stark konservierte Cystein innerhalb der repeats. Daraus ergibt sich eine ungewöhnliche Anordnung von 12 Cysteinen in einem Stapel. Die Häufigkeit von Cysteinen in InlJ ist für ein extrazelluläres Protein von L. monocytogenes außergewöhnlich, und die Frage nach ihrer Funktion daher umso brennender. Im Vergleich zum ubiquitären Vorkommen der sogenannten repeat-Proteine in der Natur sind Studien zu ihrer Stabilität und Faltung nicht äquivalent vertreten. Die zentrale Eigenschaft der repeat-Proteine ist ihr modularer Aufbau, der durch einfache Topologie gekennzeichnet ist und auf kurzreichenden Wechselwirkungen basiert. Diese Topologie macht repeat-Proteine zu idealen Modellproteinen, um die stabilitätsrelevanten Wechselwirkungen zu separieren und zuzuordnen. In der vorliegenden Arbeit wurde die Faltung und Entfaltung von InlJ umfassend charakterisiert und die Relevanz der Cysteine näher beleuchtet. Die spektroskopische Charakterisierung von InlJ zeigte, dass dessen Faltungszustand durch zwei Tryptophane im N- und C-Terminus fluoreszenzspektroskopisch gut zugänglich ist. Die thermodynamische Stabilität wurde mittels fluoreszenz-detektierten, Guanidiniumchlorid-induzierten Gleichgewichtsexperimenten bestimmt. Um die kinetischen Eigenschaften von InlJ zu erfassen, wurden die Faltungs- sowie die Entfaltungsreaktion spektroskopisch untersucht. Die Identifizierung der produktiven Faltungsreaktion war lediglich durch die Anwendung des reversen Doppelsprungexperiments möglich. Die Auswertung erfolgte nach dem Zweizustandsmodell, wonach die Faltung dem „Alles-oder-Nichts“ Prinzip folgt. Die Gültigkeit dieser Annahme wurde durch die kinetische Charakterisierung bestätigt. Es wurde sowohl in den Gleichgewichtsexperimenten als auch in den kinetisch erhaltenen Daten eine hohe freie Stabilisierungsenthalpie festgestellt. Die hohe Stabilität von InlJ geht mit hoher Kooperativität einher. Die kinetischen Daten zeigen zudem, dass die hohe Kooperativität hauptsächlich der Faltungsreaktion entstammt. Der Tanford-Wert von 0.93 impliziert, dass die Oberflächenänderung während der Faltung bereits zum größten Teil erfolgt ist, bevor der Übergangszustand ausgebildet wurde. Direkte strukturelle Informationen über den Übergangszustand wurden mit Hilfe von Mutationsstudien erhalten. Zu diesem Zweck wurden 12 der 14 Cysteine gegen ein Alanin ausgetauscht. Die repeats 1 bis 11 von InlJ beinhalten jeweils ein Cystein, deren Anordnung eine Leiter ergibt. Deren Substitutionen haben einen vergleichbar destabilisierenden Effekt auf InlJ von durchschnittlich 4.8 kJ/mol. Die Verlangsamung der Faltung deutet daraufhin, dass die Interaktionen der repeats 5 bis 11 im Übergangszustand bereits voll ausgebildet sind. Demnach liegt bei InlJ ein zentraler Faltungsnukleus vor. Im Rahmen dieser Promotionsarbeit wurde eine hohe Stabilität und ein stark-kooperatives Verhalten für das extrazelluläre Protein InlJ beobachtet. Diese Erkenntnisse könnten wichtige Beiträge zur Entwicklung artifizieller repeat-Proteine leisten, deren Verwendung sich stetig ausweitet. / Internalin J (InlJ) is a member of the family of bacterial cysteine-containing leucine-rich repeat (LRR) proteins. Internalins are invasion-associated surface proteins of Listeria monocytogenes. The LRR domain of InlJ consists of 15 repeating units, which are arranged in tandem. The consensus sequence consists of 21 residues. Interestingly, a leucine residue which is highly conserved among the Internalins is replaced by cysteine. This results in a continuous cysteine ladder of 12 repeats. This frequency of cysteines is remarkable for an extracellular protein of L. monocytogenes. Stability and folding of repeat proteins are not equivalently studied considering their ubiquitous distribution in nature. Their modular structure results in simple topology and is dominated by short-range interactions. These characteristic features of repeat proteins facilitate the separation and identification of stabilizing interactions, making repeat proteins to ideal model systems for folding studies. In this work the folding and unfolding of InlJ has been extensively characterized, shedding light on the relevance of the cysteines. Two tryptophans located in the N- and C-terminus allowed monitoring the folding state of the entire protein via fluorescence. Thermodynamic stability was therefore derived by guanidinium chloride induced equilibrium experiments. Furthermore, the chemically induced unfolding and folding reactions were characterized with respect to their kinetics. Interrupted refolding experiments were essential for tracking the productive folding reaction of InlJ. Analysis of the kinetic and equilibrium data leads to the conclusion that the results are compatible with a two-state model. The study presented here reveals high stability of the protein InlJ in conjunction with high cooperativity. Kinetic data disclosed the origin of high cooperativity in the folding reaction; with a Tanford value of about 0.93. This high value implicates that the major change of the accessible surface area occurs before the transition state is formed. Mutational studies provided more detailed structural information about the transition state. 12 of 14 cysteine residues were mutated to alanine for this purpose. The cysteines in repeats 1 to 11 stack over each other and form a ladder of reduced cysteines. The substitution of one of these cysteines has an average destabilizing effect of 4.8 kJ/mol. The deceleration of the folding reaction by the substitution shows that repeats 5 to 11 are already fully structured in the transition state, pointing to a central nucleus in the folding of the LRR-protein InlJ. The extracellular protein InlJ reveals extreme stability and high cooperativity. The insights into the folding of this LRR motif could facilitate the design of further artificial repeat proteins.

The electrostatic actuation with its several advantages is the main principle for micro-electro-mechanical systems (MEMS). One major drawback is the nonlinear behavior, which results into instability, known as the electrostatic pull-in effect. This effect might also push a closed-loop configuration into instability and thus makes a linear time-invariant control inapplicable to the system. The paper investigates the stability of an acceleration sensor in closed-loop operation with this setting. A simplified controller adjustment gives a first insight into this topic. Practical implementations saturate on the quantizer's full-scale value, which is also considered in the stability analysis. Numerical phase-plane analysis verifies the stability and shows further surprising results.

This dissertation is concerned with invertibility and one-sided invertibility of Toeplitz operators over the half plane whose generating functions admit homogenous discontinuities, and with stability of their pseudo finite sections. The invertibility criterium is given in terms of invertibility of a family of one dimensional Toeplitz operators with piecewise continuous generating functions. The one-sided invertibility criterium is given it terms of constraints on the partial indices of certain Toeplitz operator valued function.

The present work is the fourth (and final) contribution to an inter-laboratory collaboration that was planned at the 3rd International Summit on Organic Photovoltaic Stability (ISOS-3). The collaboration involved six laboratories capable of producing seven distinct sets of OPV devices that were degraded under well-defined conditions in accordance with the ISOS-3 protocols. The degradation experiments lasted up to 1830 hours and involved more than 300 cells on more than 100 devices. The devices were analyzed and characterized at different points of their lifetimes by a large number of non-destructive and destructive techniques in order to identify specific degradation mechanisms responsible for the deterioration of the photovoltaic response. Work presented herein involves time-of-flight secondary ion mass spectrometry (TOF-SIMS) in order to study chemical degradation in-plane as well as in-depth in the organic solar cells. Various degradation mechanisms were investigated and correlated with cell performance. For example, photo-oxidation of the active material was quantitatively studied as a function of cell performance. The large variety of cell architectures used (some with and some without encapsulation) enabled valuable comparisons and important conclusions to be drawn on degradation behaviour. This comprehensive investigation of OPV stability has significantly advanced the understanding of degradation behaviour in OPV devices, which is an important step towards large scale application of organic solar cells. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Hydrogen is an efficient, carbon-free and safe energy carrier. However, its compact and weight-efficient storage is an ongoing subject for research and development. Among the intensively investigated hydrogen storage materials, lithium aluminum hydride (LiAlH4) is an attractive candidate because of its high theoretical hydrogen density (volumetric: 96.7g H2/l material; gravimetric: 10.6 wt.%-H2) in combination with rather low decomposition temperatures (onset temperature <100°C after doping). Although the reversible dehydrogenation of LiAlH4 must be carried out with the help of organic solvent, LiAlH4 can serve as single-use hydrogen storage material for various special applications, for example, hydrogen fuel cell systems. This thesis deals with transition metal (TM)-doped LiAlH4 aiming at tailored dehydrogenation properties. The crystal structure and morphology of TM-doped LiAlH4 is characterized by XRD and SEM respectively. The positive effects of four dopants (NiCl2, TiCl3, ZrCl4 and TiCl4) on promoting the dehydrogenation kinetics of LiAlH4 are systematically studied by thermal analysis. Based on the state of each TM chloride (solid or liquid), three low-energy-input doping methods (1. ball-milling at low rotation speed; 2. manual grinding or magnetic stirring; 3. magnetic stirring in ethyl ether) are compared in order to prepare LiAlH4 with the maximum amount of hydrogen release in combination with fast dehydrogenation kinetics. The dehydrogenation properties of the TM-doped LiAlH4 powders are measured under isothermal conditions at 80°C at a H2 pressure of 1 bar, which is within the operating temperature range of proton exchange membrane (PEM) fuel cells, aiming at applications where the exhaust heat of the fuel cell is used to trigger the dehydrogenation of the hydrogen storage material. Furthermore, the mid-term dehydrogenation behavior of TM-doped LiAlH4 was monitored up to a few months in order to test its mid-term storability. In addition, the pelletization of TM-doped LiAlH4 is investigated aiming at a higher volumetric hydrogen storage capacity. The effects of compaction pressure, temperature and the H2 back-pressure on the dehydrogenation properties of TM-doped LiAlH4 pellets are systematically studied. Moreover, the volume change through dehydrogenation and the short-term storage of the TM-doped LiAlH4 pellets are discussed in view of practical applications for PEM fuel cell systems. / Wasserstoff ist ein effizienter, kohlenstofffreier und sicherer Energieträger. Jedoch die kompakte und gewichtseffiziente Speicherung ist ein permanentes Forschungs- und Entwicklungsthema. Unter den intensiv untersuchten Materialien für die Wasserstoffspeicherung ist aufgrund der hohen theoretischen Speicherdichte (volumetrisch: 96,7 g H2/L, gravimetrisch: 10.6 Gew.%-H2) in Kombination mit sehr niedrigen Zersetzungstemperaturen (Anfangstemperatur < 100°C nach Dotierung) Lithium Aluminiumhydrid (LiAlH4) ein vielversprechender Kandidat. Obwohl die reversible Dehydrierung von LiAlH4 mit Hilfe von organischen Lösungsmitteln durchgeführt werden muss, kann LiAlH4-Pulver als Einweg-Speichermaterial für verschiedene Anwendungen dienen, beispielsweise für Wasserstoff/Brennstoffzellensysteme. Diese Doktorarbeit beschäftigt sich mit LiAlH4 dotiert mit Übergangsmetall, mit dem Ziel maßgeschneiderte Dehydrierungseigenschaften zu erreichen. Die Kristallstruktur und die Morphologie der mit Übergangsmetallen dotierten LiAlH4-Pulver wurden mit Röntgenbeugung (XRD) und Rasterelektronenmikroskopie (REM) charakterisiert. Weiterhin wurde der positive Effekt der Dotanden auf die reaktionsfördernde Dehydrierung von LiAlH4 systematisch mit Hilfe thermoanalytischer Methoden untersucht. Für jedes Übergangsmetall, welches in Form von Übergangsmetallchloriden vorlag, wurden drei Dotierungsmethoden mit niedrigem Energieeintrag (Kugelmahlen mit geringer Rotations-geschwindigkeit, manuelles Schleifen/Magnetrühren, Magnetrühren mit Ethylether) verglichen, um LiAlH4-Pulver mit einer maximalen Wasserstofffreisetzungsmenge in Kombination mit einer schnellen Dehydrierungskinetik zu erzielen. Die Dehydrierung des dotierten LiAlH4-Pulvers wurde unter isothermen Bedingungen bei 80°C und einem H2-Druck von 1 bar gemessen, was im Bereich der Betriebstemperatur von PEM-Brennstoffzellen (Proton Exchange Membran) liegt. Dadurch sollen Anwendungen anvisiert werden, bei denen die entstehende Abwärme der Brennstoffzelle genutzt wird, um die Dehydrierung des Wasserstoffspeichermaterials auszulösen. Zudem wurde das Dehydrierungsverhalten des dotierten LiAlH4 bis zu einigen Monaten kontrolliert, um die mittelfristige Haltbarkeit zu testen. Weiterhin wurde die Pelletierung des mit Übergangsmetallen dotierten LiAlH4 mit dem Ziel untersucht, eine hohe volumetrische Speicherkapazität zu erreichen. Der Einfluss des Pressdrucks, der Dehydrierungstemperatur und des H2-Gegendrucks auf die Dehydrierungseigenschaften der mit Übergangsmetallen dotierten LiAlH4-Presslinge wurde systematisch analysiert. Außerdem wird die Volumenveränderung durch die Dehydrierung und die Kurzzeitspeicherung der mit Übergangsmetallen dotierten LiAlH4-Presslinge im Hinblick auf praktische Anwendungen unter Nutzung der Brennstoffzelle diskutiert.

Transition metal oxide coupling with carbon is an effective method for improving electrical conductivity of battery electrodes and avoiding the degradation of their lithium storage capability due to large volume expansion/contraction and severe particle aggregation during the lithium insertion and desertion process. In our present work, we develop an effective approach to fabricate the nanocomposites of porous rod-shaped Fe₃O₄ anchored on reduced graphene oxide (Fe₃O₄/rGO) by controlling the in situ nucleation and growth of β-FeOOH onto the graphene oxide (β-FeOOH/GO) and followed by dielectric barrier discharge (DBD) hydrogen plasma treatment. Such well-designed hierarchical nanostructures are beneficial for maximum utilization of electrochemically active matter in lithium ion batteries and display superior Li uptake with high reversible capacity, good rate capability, and excellent stability, maintaining 890 mA h g⁻¹ capacity over 100 cycles at a current density of 500 mA g⁻¹.