This thesis summarizes experimental results on mass transport of small hydrocarbons in micro-porous crystals obtained via interference microscopy (IFM). The transport process has been investigated in three difffferent materials with difffferent pore structures : the metal-organic framework Zn(tbip) with one-dimensional pores, a FER type zeolite with two-dimensional anisotropic pore structure and zeolite A, a LTA type material with isotropic three-dimensional pore structure. Mass transport is described in terms of diffffusivity and surface permeability, both derived from the detected transient concentration profiles. The results on intra-crystalline diffffusion are discussed under consideration of the influences of pore diameter and molecule diameter, which are both found to have a strong influence on the diffffusivity. Based on experimental results measured on the Zn(tbip) material, a new model for the description of surface barriers is developed and proved by experiment. It is demonstrated that the observed surface barrier is created by the total blockage of a large number of pore entrances at the surface and not by a homogeneous surface layer.

Quellfähige Verbundwerkstoffe aus Ton und Polyakrylamid können große Quantitäten von Wasser absorbieren, behalten aber dabei eine hohe mechanische Festigkeit und gute Dämpfungseigenschaften und stellen daher eine neue Klasse von Hydrogelen mit potentiell interessanten technologischen Eigenschaften dar. Solche superabsorbierende Verbundwerkstoffe (SAPC) werden durch Polymerisation mit einem Elektronenstrahl oder Bestrahlung mit UV-Licht hergestellt. Die Untersuchung der Eigenschaften von SAPC mit Hilfe von XRD, SEM, DSC, TGA, FTIR und NMR (27Al, 29Si und C) zeigen, dass in der SAPC-Struktur das Akrylamid (AM) mit Montmorillonit in dreierlei unterschiedlichen Weisen verbunden ist: a. AM interkaliert in den Zwischenschichtraum von Montmorillonit in bimolekularen Schichten, die durch van-der-Waals-Kräfte und Wasserstoffbindungen verknüpft sind; b. AM gebunden an der Oberfläche von Montmorillonit durch Wasserstoffbindungen; c. AM als freies Polymernetzwerk. Die Ergebnisse der rheologischen, mechanischen und thermischen Untersuchungen von SAPC zeigen eine völlig vernetzte Struktur mit vergleichsweise hoher mechanischer Festigkeit und thermischer Stabilität. Die Verwendung von SAPC bei der Ölgewinnung (Erhöhung der Ausbeute), im Umweltschutz (Reduzierung sauerer Berge), der Agri- und Silvikultur (Pflanzen, Samenbau), der petrochemischen Industrie (Entwässern), im Bauingenieurwesen (Zementbeimischung) und als Sensorsubstanz demonstriert, dass SAPC ein hohes Potential für umweltfreundliche und wirtschaftliche alternative Zwecke hat.

Polymer brushes can be used to tailor the physical and chemical properties of materials on demand to meet potential applications. Therefore, fabrication of polymer brushes with well-defined structure and functional groups enables the engineering of new materials with diverse functions. In addition, two-dimensional (2D) materials have their unique physical/chemical properties and potential applications in (opt)electronics, catalysis, energy storage, sensing, and other related fields. However, the dispersibility, chemical stability, charge transport behavior, mechanical properties of the 2D materials hinder their further applications. Therefore, combining polymer brushes and 2D materials may bring in new properties which are not available by either of them alone. This thesis focuses on brushing up 2D materials (from inorganic to organic) with universal photografting techniques. (1) The first chapter introduces the outline and research content of the thesis. (2) The second chapter describes the background of 2D materials and polymer brushes. In particular, this chapter analyzes mechanisms, drawbacks and benefits of different polymerization methods, and also summarizes the general approaches to grow polymer brushes on 2D material surfaces, coupling with potential applications of polymer functionalized 2D materials. (3) The third chapter shows the motivation and aim of this thesis. (4) The fourth chapter discusses the results of the functionalization of hexagonal boron nitride (hBN), MoS2, graphitic-carbon nitride (gCN), alkyl-polydopamine (alkyl-PDA), and conjugated 2D polymers (2DPs) with polymer brushes by the same self-initiated photografting and photopolymerization (SIPGP) method and their related applications in detail, respectively. First, the direct photopolymerization of vinyl monomers results in the formation of thick and homogeneous polymer brushes covalently bounded to hBN. The brush layer mechanically and chemically stabilizes the material and allows facile handling as well as long-term use in water splitting hydrogen evolution reactions. Second, the chapter demonstrates the MoS2 can be directly modified with polymer brushes by SIPGP. After modifying MoS2 with polymer brushes, the dispersibility of polymer brushes-modified MoS2 was obviously improved. Third, the polymer brushes functionalized gCN significantly improves the dispersibility. Application of polymer brush functionalized gCN as excellent recyclable substrates for an outstanding SERS as well as photocatalytic degradation of dyes is demonstrated. Fourth, to directly obtain the 2D materials with functional groups, the chapter proposes a facile method to prepare amphiphilic polymeric Janus nanosheets with hydrophilic PDA and hydrophobic alkyl chains at both sides. Benefiting from the Janus property of the alkyl-PDA nanosheets, the nanosheets can be grafted polymer brushes through photografting and be conjugated Fe3O4 nanoparticles selectively onto the PDA side. Finally, the chapter shows that various polymer brushes can be directly grafted onto 2DPs and freestanding system is also obtained. Moreover, it is found that the morphology of freestanding system quickly and reversibly responds to solvent quality by shrinking/stretching. (5) The fifth chapter addresses the general conclusion and future prospective of the whole work. (6) The sixth chapter describes the experiment part of the whole thesis.

Die erfolgreiche Optimierung der Leistung von thermoelektrischen Materialien, die durch zT beschrieben wird, ist entscheidend für ihre Anwendung für das Wärmemanagement und die Kühlung von Leistungselektronik. Im Gegensatz zu Bulk-Proben bleibt die vollständige zT-Charakterisierung von Dünn- und Dickfilmmaterialien eine große Herausforderung. Dies ist insbesondere relevant für Filme, die durch elektrochemische Abscheidung synthetisiert werden, wo das Material auf eine elektrisch leitende Schicht abgeschieden wird. In dieser Dissertation habe ich ein Transport-Device für eine vollständige zTCharakterisierung von elektrochemisch abgeschiedenen Materialien entwickelt, während der Einfluss der elektrisch leitenden Schicht, sowie des Substrats beseitigt wird. Die zT-Charakterisierung erfolgt unter Verwendung eines auf einer freistehenden Membran suspendierten thermoelektrischen Materials innerhalb des entwickelten Transport-Devices, die durch eine Kombination von Fotolithografie und Mikrostrukturierungstechnik zusammen mit Ätzprozessen hergestellt wurde. Für die Messung der Wärmeleitfähigkeit habe ich eine eindimensionale, analytische, stationäre Methode eingesetzt, welche mit Hilfe von dreidimensionalen Finite-Elemente-Simulationen bestätigt wurde. Darüber hinaus habe ich die temperaturabhängigen thermoelektrischen Eigenschaften von zwei Dickschichten mit Hilfe des entwickelten Devices untersucht und mit Bulk-Proben und Dünnfilmen verglichen. Auf diese Weise konnte die Validität des Transport-Devices nachgewiesen werden. Neben der Optimierung von mikro-thermoelektrischen Materialien, die mit dem Transport- Device charakterisiert werden, ist die Leistung von thermoelektrischen Devices von den Faktoren Design, Geometrie und Konstruktion beeinflusst. Daher habe ich den Einfluss der Geometrie auf die Leistung eines elektrochemisch hergestellten mikrothermoelektrischen Generators mit Hilfe einer Finite-Elemente-Simulation untersucht.

Quellfähige Verbundwerkstoffe aus Ton und Polyakrylamid können große Quantitäten von Wasser absorbieren, behalten aber dabei eine hohe mechanische Festigkeit und gute Dämpfungseigenschaften und stellen daher eine neue Klasse von Hydrogelen mit potentiell interessanten technologischen Eigenschaften dar. Solche superabsorbierende Verbundwerkstoffe (SAPC) werden durch Polymerisation mit einem Elektronenstrahl oder Bestrahlung mit UV-Licht hergestellt. Die Untersuchung der Eigenschaften von SAPC mit Hilfe von XRD, SEM, DSC, TGA, FTIR und NMR (27Al, 29Si und C) zeigen, dass in der SAPC-Struktur das Akrylamid (AM) mit Montmorillonit in dreierlei unterschiedlichen Weisen verbunden ist: a. AM interkaliert in den Zwischenschichtraum von Montmorillonit in bimolekularen Schichten, die durch van-der-Waals-Kräfte und Wasserstoffbindungen verknüpft sind; b. AM gebunden an der Oberfläche von Montmorillonit durch Wasserstoffbindungen; c. AM als freies Polymernetzwerk. Die Ergebnisse der rheologischen, mechanischen und thermischen Untersuchungen von SAPC zeigen eine völlig vernetzte Struktur mit vergleichsweise hoher mechanischer Festigkeit und thermischer Stabilität. Die Verwendung von SAPC bei der Ölgewinnung (Erhöhung der Ausbeute), im Umweltschutz (Reduzierung sauerer Berge), der Agri- und Silvikultur (Pflanzen, Samenbau), der petrochemischen Industrie (Entwässern), im Bauingenieurwesen (Zementbeimischung) und als Sensorsubstanz demonstriert, dass SAPC ein hohes Potential für umweltfreundliche und wirtschaftliche alternative Zwecke hat.

In der vorliegenden Arbeit wurde die Methode der Kernmagnetischen Resonanz im Niedrigfeld für poröse Materialien unter hohem statischen Gasdruck entwickelt, getestet und angewendet. Die Entwicklung erstreckte sich von dem Design des NMR-Sensors über der Aufbau mit der Hochdruckapparatur bis hin zur Inbetriebnahme. Mit diesem experimentellen Aufbau wurden zunächst aus der Literatur bekannte Wissenstand zu NMR-Experimenten mit Methan nachvollzogen und die technischen Eigenschaften erprobt. Diese Grundlagen wurden in die Untersuchung von porösen Proben überführt. Es wurden Adsorbtionskapazitäten bestimmt und Modelle für die Adsorbtion und Diffusion in den Poren entwickelt.:1. Einleitung 2. Grundlagen der kernmagnetischen Resonanz NMR 3. Entwicklung und Aufbau des NMR-Experiments für hohe Gasdrücke 4. Experimente zum Einstellen und Testen des Hochdruck-NMR-Sensors 5. Untersuchung von Proben mit Porenfluiden unter hohem statischen Druck mittels NMR 6. Zusammenfassung und Bewertung der Ergebnisse

In this thesis the influence of different growth conditions on the structural and the magnetic properties of magnetite were analyzed. Therefore, ultrathin Fe3O4 films were grown on MgO(001) substrates, on NiO, and on Fe pre-covered MgO(001) substrates. In the first part of this thesis magnetite films with different film thicknesses were deposited directly on MgO by RMBE to investigate the thickness dependence of the anomalous strain and the in-plane magnetic anisotropy. Surface sensitive methods like XPS and LEED have shown that all films in the investigated thickness range are stoichiometric and epitactic magnetite. Bulk sensitive XRD experiments at the specular rod point to well-ordered films with homogenous film thickness indicated by the distinct Laue oscillations. However, the vertical layer distances are smaller than expected even for strained magnetite. Raman measurements were carried out to clarify this contradiction between surface sensitive and bulk sensitive measurements. While the 20 nm and 30 nm films exhibit the typical bands for magnetite, no distinct bands can be observed for the 7.6 nm film. Due to this results we first assume a partial formation of a thin maghemite layer on top of the uncapped magnetite film under ambient conditions. Nevertheless, additional XPS measurement exclude the complete oxidation of magnetite to maghemite since there is no significantly increased Fe3+-signal visible. Thus, the low vertical layer distance can be attributed to the presence of APBs causing an anomalous strain relaxation as reported in literature. Although all films feature ferromagnetic behavior there are differences in the characteristic of the magnetic in-plane anisotropy. The 7.6 nm film has an in-plane magnetic isotropy while the 20 nm and 30 nm film have an in-plane fourfold magnetic anisotropy. Here, the fourfold magnetic anisotropy is stronger for the 20 nm magnetite film than for the 30 nm film. The critical film thickness for the transition from magnetic isotropy to magnetic fourfold anisotropy may be influenced by film thickness and lattice strain induced by the substrate. The second part of this thesis features the thickness dependence of the structural quality of Fe3O4/NiO bilayers. Each film of the Fe3O4/NiO bilayer on MgO(001) have been successfully grown by RMBE. LEED and XPS experiments have proven that the surface near regions of the distinct films have high structural and stoichiometric properties. Here, too, the detailed ’bulk’ structural characterization of Fe3O4/NiO bilayers were carried out using XRD. It was shown that the Fe3O4 films grow homogeneously and smoothly on NiO films if the NiO film thickness is below 24 nm. Above this NiO film thickness the structural quality of the magnetite films gets distinctly worse. This behavior can be attributed to the fact that the interface roughness between NiO and Fe3O4 depends on the NiO film thickness. The roughness of the 3 nm NiO film is rather small and it is rising obviously with increasing NiO film thickness. Thus, the structural quality of the magnetite films grown on 30 nm NiO films is constantly reduced with increasing magnetite film thickness since the quality of the Fe3O4 films is influenced by the quality of the Fe3O4/NiO interface. In the third study the influence of initial iron buffer layers on the magnetic properties of magnetite grown on MgO(001) substrates has been investigated. In situ XPS and LEED indicate that the structural and stoichiometric properties of the surface near region of the magnetite films are not influenced by the iron buffer layer. However, the structural and magnetic properties of the whole film have changed compared to magnetite grown directly on MgO as shown by XRD and MOKE. The crystalline quality is poor and the magnetic easy axis of the magnetic in-plane anisotropy is rotated by 45◦ compared to magnetite films grown directly on MgO. Both crystalline quality and the rotation of the magnetic in-plane anisotropy show no dependence on the film thickness. However, the strength of the magnetocrystalline anisotropy decreases with increasing film thickness. XPS and XRD measurements have indicated that the iron buffer layer is completely oxidized during the second growth stage of the magnetite. The small Kerr rotation in the MOKE experiments of the samples with film thicknesses up to 28 nm confirms this result since a remaining iron film would cause a higher Kerr rotation. In the last part of this thesis the structural and magnetic properties of a partially oxidized, a completely oxidized and a metallic iron film are analyzed. The partially oxidized iron film is a bilayer with a metallic iron film and an iron oxide film. The surface near stoichiometry of both oxidized iron films correspond to magnetite as proven by XPS. The structural analysis by XRD reveals that though these magnetite films are crystalline, they have an inhomogeneous thickness. The magnetization curves of the partially oxidized film (bilayer) measured by MOKE exhibit a magnetic saturation which is comparable to the magnetic saturation of the single metallic iron film. However, the coercive field is higher compared to the single metallic iron film due to the high interface roughnesses. Considering the coercive field as a function of the sample rotation α the bilayer exhibits a fourfold anisotropy with eight maxima. However, the angular dependence of the magnetic remanence features a simple fourfold anisotropy with easy axes in h110i directions of MgO(001). Vector MOKE analysis displays that the magnetic reversal processes of the bilayer are similar to single metallic iron films. Thus, the bilayer exhibits mostly the magnetic properties of a single iron film. The bilayer has the same magnetic easy axis and a similar magnetic saturation. The magnetic easy axis of the magnetic in-plane anisotropy of the completely oxidized iron film is rotated by 45◦ compared to magnetite films grown directly on MgO as already observed in Ref. [148]. The completely oxidized iron film exhibits also a significantly increased coercive field due to high surface roughness. A magneto-dynamic investigation of the exchange-coupling of the Fe3O4/Fe bilayer system was carried out to yield all relevant magnetic parameters, such as anisotropies, as well as the coupling constant J1. Here, also a complex fourfold anisotropy was observed, which might be due to a coupling of a perpendicular spin-wave mode in the magnetite layer with the acoustical coupling mode. We have also successfully calculated the angular dependence of the resonance field of all films using the eighth order of the magnetocrystalline anisotropy. Although we have applied many measurement methods, we have found no explanation for the complex fourfold angular dependence of the coercive field of the bilayer. Nevertheless, this bilayer provides interesting properties for application in MTJs due to its enhanced magnetic properties like complex fourfold magnetic anisotropy and higher coercive field and remanence. All in all, we have shown that the structural and magnetic properties of magnetite films are strongly influenced by interlayers between film and substrate. While magnetite films directly deposited on MgO exhibit a homogeneous film thickness, both NiO interlayers with a thickness above 24 nm and initially grown iron films deteriorate the structural quality of the on top grown magnetite films. In addition, the magnetic fourfold anisotropy is rotated by 45◦ in comparison to magnetite films grown directly on MgO for the structurally disturbed magnetite on iron pre-covered MgO substrates. Here, further investigations are necessary to understand why this anisotropy rotation occurs and how we can improve the structural quality of magnetite on iron and NiO. The growth of magnetite by oxidizing previously deposited iron films leads to crystalline magnetite films but with inhomogeneous film thicknesses. In case of a Fe3O4/Fe bilayer, the magnetic properties are drastically changed due to the magnetic coupling between the iron and the magnetite film.

Metals and semiconductors are widely used for making technological devices as they carry electricity. Discovery of topological insulator (TI) has enriched the list of such materials . TIs are different than conventional insulators in the sense that, even though the bulk of the system remains insulating, the boundary of the system can carry current, due to the presence of conducting states. Moreover, these states are usually symmetry protected, and show robustness feature. This can be made use for making energy efficient spintronic devices, and fault-tolerant quantum computers. As the search for novel topological phases of matter is on the rise, this thesis mostly deals with the realization of non-interacting TI phases theoretically, in both real materials and toy model scenarios. In particular, it focuses on exploring the topological crystalline insulating (TCI) phases, which are basically TIs with protected crystalline symmetries. In connection to the TCI phases based on layered systems, chapter 2 discusses about how one can attain TCIs protected by mirror symmetry in heterostructures consisting of graphene monolayers separated by two-dimensional polar spacers. In chapter 3, we first focus on the naturally occurring mineral called Jacutingaite (Pt$_{2}$HgSe$_{3}$), and show based on density-functional calculations that it realizes dual topological phase (weak TI and TCI) and that the same conclusion holds for Pd$_{2}$HgSe$_{3}$. What makes this layered system more interesting is the fact that monolayer version of Jacutingaite is predicted to have a sizable band gap of $~0.5$eV, featuring a novel quantum spin Hall insulator. Further, we introduce tight-binding models that capture the essential topological properties of this dual topological phase in materials with three-fold rotation symmetry and use these models to describe the main features of the surface spectral density of different materials in the class. Following this, chapter 4 aims at exploring topological phases for two cubic three dimensional half-Heusler materials belonging to the space group 216. We investigate from first-principles the possibility of hinge modes in very proximate topological phases tunable by moderate uniaxial strain. We consider the compounds LiSbZn and LiBiZn. While LiSbZn has a topologically trivial band structure, the larger spin-orbit coupling of Bi causes a band inversion in LiBiZn. We predict the existence of topologically trivial hinge states in both cases. The hinge modes are affected by the bulk topological phase transitions, but in an indirect way: topological surface modes, when present, hybridize with the hinge states and obscure their visibility. Thus, we find that the most visible hinge modes actually occur when no band inversions are present in the material. Our work highlights the interplay and competition between surface and hinge modes in half-Heuslers, and may help guide the experimental search for robust boundary signatures in these materials. Finally, in chapter 5, the thesis presents a flavor of newly discovered topological transport phenomena, namely Magnus Hall effect in two and three dimensional systems. Effects of strain, warping, and tilt on response have been explored in detail. Starting with two-dimensional (2D) topological systems, we find that warping induced asymmetry in both the Fermi surface and Berry curvature can in general enhance the Magnus response for monolayer graphene and surface states of topological insulator. The strain alone is only responsible for Magnus valley responses in monolayer graphene while warping leads to finite Magnus response there. Interestingly, on the other hand, strain can change the Fermi surface character substantially that further results in distinct behavior of Magnus transport coefficients as we observe in bilayer graphene. And finally, going beyond 2D systems, we also investigate the Magnus responses in three-dimensional multi-Weyl semimetals (mWSMs) to probe the effect of tilt and anisotropic nonlinear energy dispersion. Remarkably, Magnus responses can only survive for the WSMs with chiral tilt. In particular, our study indicates that the chiral (achiral) tilt engenders Magnus (Magnus valley) responses. Therefore, Magnus responses can be used as a tool to distinguish between the untilted and tilted WSMs in experiments.

Paper is renewable, recyclable, sustainable and biodegradable material and, as a result, paper-based materials are widely used in the world packaging market. However, paper-based materials cannot compete with plastics in terms of processability into various 3D shapes. This is due to poor formability of paper, which is closely associated with its toughness. To improve paper formability, we report on a facile and green method that combines fiber and paper mechanical modifications at different structural levels as well as biopolymer treatment via spraying. As a result, a remarkable elongation of ∼30% was achieved after proposed combined approach on the laboratory scale. At the same time, a significant increase in tensile strength and stiffness (by ∼306% and ∼690%, respectively) was observed. Overall, an inexpensive, green, and scalable approach is introduced to improve formability of fiber networks that in turn allows preparation of 3D shapes in the processes with fixed paper blanks such as vacuum forming, hydroforming, hot pressing, etc.

Commons offer an opening for imagining care-based alternatives to growth-based economies and their implications on the use of urban resources, trajectories of technological development and infrastructural path dependencies. Commons are resources used and consumed by a specified community, which negotiates, regulates, and manages the resource’s distribution or production. Commoning as a practice refers not only to the management of resources but also to creating the frameworks and infrastructures in which resources turn into commons. Rescued food is a resource that can turn into commons after being ejected from shelves and before turning into food waste.