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Two dimensional (2D) materials have received growing interest because of their unique properties compared to their bulk counterparts. Graphene is the archetype 2D solid, but other materials beyond graphene, such as MoS2 and BN have become potential candidates for several applications. Recently, a new family of 2D materials of early transition metal carbides and carbonitrides (Ti2CTx, Ti3C2Tx, Ti3CNTx, Ta4C3Tx, and more), labelled MXenes, has been discovered, where T stands for the surface-terminating groups. Before the present work, MXenes had only been synthesized in the form of exfoliated and delaminated powders, which is not suitable for electronic applications. In this thesis, I demonstrate the synthesis of MXenes as epitaxial thin films, a more suitable form for electronic and photonic applications. Results show that 2D epitaxial Ti3C2Tx films - produced by HF and NH4HF2 etching of magnetron sputter-grown Ti3AlC2 - exhibit metallic conductive behaviour down to 100 K and are 90% transparent to light in the visible-infrared range. The results from this work may open the door for MXenes as potential candidates for transparent conductive electrodes as well as in electronic, photonic and sensing applications. MXenes have been shown to intercalate cations and molecules between their layers that in turn can alter the surface termination groups. There is therefore a need to study the surface chemistries of synthetized MXenes to be able to study the effect of intercalation as well as altering the surface termination groups on the electronic structure and chemical states of the elements present in MXene layers. X-ray Photoelectron Spectroscopy (XPS) in-depth characterization was used to investigate surface chemistries of Ti3C2Tx and Ti2CTx. This thesis includes the discussion of the effect of Ar+ sputtering and the number of layers on the surface chemistry of MXenes. This study serves as a baseline for chemical modification and tailoring of the surface chemistry groups to potential uses and applications. New MXene phases, Nb2CTx and V2CTx, are shown in this thesis to be produced from HF chemical etching of Nb2AlC and V2AlC powders. Characterization of the produced MXenes was carried out using Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Transmission Electron Microscope (TEM) and XPS. Nb2CTx and V2CTx showed promising performance as electrodes for Li-ion batteries. In this thesis, electrochemical etching was used in an attempt to produce 2D metal carbides (MXene) from their ternary metal carbides, Ti3SiC2, Ti3AlC2 and Ti2AlC MAX phases. MAX phases in the form of highly dense bulk produced by Hot Isostatic Press. Several etching solutions were used such as HF, NaCl and HCl. Unlike the HF chemical etching of MAX phases, which results in MXenes, the electrochemical etching resulted in Carbide Derived Carbon (CDC). Here, I show the characterization of the produced CDC using several techniques such as XRD, TEM, Raman spectroscopy, and XPS. Electrochemical characterization was performed in the form of cyclic voltammetry, which sheds light on the etching mechanism. / <p>The series name <em>Linköping Studies in Science and Technology Licentiate Thesis</em> in this publication is incorrect. Correct name is <em>Linköping Studies in Science and Technology. Thesis</em>.</p>

In the agricultural industry, cultivator tines are used for stubble cultivation and seedbed preparation. They are exposed to rapidly developing abrasive wear, which becomes a major economic problem. The occurring wear in the tines is heavily dependent on the characteristics of the soil which it passes through. In this master thesis the goal is to produce a method which, in a laboratory environment, can reproduce the circumstances which real cultivator tines are exposed to in the field. The method will enable analysis and evaluation of the initial wear mechanisms causing the wear. In order to simulate the tillage, a pendulum setup was constructed. With this, a series of repeated impact tests were performed into a soil sample. Throughout the tests, the “cultivator tine” samples were made of aluminium. This material choice would enable an accelerated wear rate, following its low hardness. All tests were performed in the same soil, with moisture content being the only varying parameter;~0% and 18% respectively. The samples which had passed through soil with higher moisture showed reduced wear compared to those which had passed through dry soil. The pendulum setup contributed to the tests being executed in a controlled and reliable manner. Hence, it is determined to be suitable for further use in any future project work related to the subject.

In this project, different molecules have been investigated with the purpose of creating anohmic contact between metals and carbon nano materials. In particular, we considered simplemolecules connecting a graphene layer and a copper-slab. In order to determine the capability of such systems, the electronic structure was computedusing Density Functional Theory (DFT). Structural relaxation was performed in order to findcandidates where the metal and the graphene binds chemically with the hypothesis that thehybridization of the states will induce more states at the Fermi level. Six different molecularchains were tested and three of them were found to chemisorb to the graphene sheet and thecopper surface simultaneously. The electronic properties for these systems were then furtherinvestigated using the density of states (DOS). An overlap density of states (ODOS) wasdefined in order to evaluate the respective contribution of the graphene, metal and molecule. From the DOS analysis, we report that these systems did not form ohmic contacts as the resultshows too few states close to the Fermi level. The most interesting case was using a hexanolchain which had some partially overlapping states seen from the ODOS of the graphenemoleculeand graphene-Cu at the Fermi level. However, these were only small contributions.Further research is crucial in order to find a more suitable molecular chain between thegraphene and the copper for an ohmic contact.

Manganese-Aluminium is an alloy with attractive ferromagnetic propertieswhenL10-structured ( -phase). If sucient permanent magnetic propertiescan be achieved at a low cost, it has potential to be a new permanentmagnet material on the market. In this thesis, drop synthesized ingots ofMn55Al45C2 were crushed and examined as solid pieces and as powders.The goal was to better understand how the material behaves magneticallyafter synthesis in relation to its chemical composition and cooling rate. Representativecross-sections of solid ingot pieces were created by mounting thepieces in polyfast followed by polishing. The surfaces were studied withScanning Electron Microscopy and Energy-dispersive X-ray spectroscopy tomap the chemical composition and then by Magnetic Force Microscopy andMagneto-optic Kerr eect to see how the chemical composition inuencesthe magnetic properties. It was found that areas richer in aluminium (Al),compared with the rest of the surface, behaved non-magnetically. The resultsfrom X-ray diraction on the powders suggests that the Al-rich areasconsists of the non-magnetic- and 2-phases.The powder that was extracted from the top of one of the drop synthesizedingots was nearly pure -phase but did not have an impressive magnetization.A complementary magnetic measurement was done on a solid piece from thetop part. This piece was found to reach a higher magnetization at a lowereld. The result indicates that crushing the material, even just by hand witha mortar and pestle, greatly reduces the magnetization.

The thesis has dealt with transparent conducting oxide (TCO) materials, with a focus on Al:ZnO and with studies on Sn:In2O3 and ZnO. TCOs are a material group that is used for its properties of being conductive and at the same time transparent. In solar cells, a top layer of TCO is often used to allow light to transmit into the cell and then conduct the resulting current.   A set of growth parameters was chosen and optimized through a literature study and experiments. The depositied thin films were characterized by optical and electrical characterization methods. Rf-magnetron-sputtering was used as the deposition method, where the influence of O2, argon and substrate temperature were the parameters to be studied. As a part of the characterization a model for spectroscopic ellipsometry on Al:ZnO was made, enabling faster measurement of transport properties. The main parameter affecting the TCO properties was found to be oxygen flow and the optimum flow value for each material has been determined. Substrate heating did not show any significant improvement on the resistivity of Al:ZnO with a minimum value of ~5.0*10-4 Ωcm while no heating resulted in a value of ~6.0*10-4  Ωcm. These values are comparable to the state-of-the-art from the literature.   As a demonstration of application, the developed AZO and ZnO were applied to CIGS solar cells and these were compared to a reference. The newly developed AZO and ZnO was comparable to the reference but a lower mean fill factor indicates that improvements can be made.

The aim of this thesis is to obtain a basic knowledge of the factors that affect corrosion of aluminium in tap water for different kinds of applications like water pipes for tap water, solar systems, HVAC&amp;R-applications (like fan coil units on chillers) and heat sinks for electronic or industrial applications. Open systems are used in some applications and closed systems in others. There is a clear difference in the corrosion behaviour of these two systems. The main reasons for this difference are that the content of oxygen differs between the two systems and also that inhibitors can be used in closed systems to hinder corrosion. In this thesis focus will be on corrosion in open systems. The corrosion properties in tap water for different alloys of aluminium and different surface treatments have been examined. The influences on corrosion of the oxygen content in water and the iron content in aluminium alloys have been investigated. The corrosion properties of an aluminium alloy in deionised water have also been examined.

<p>This project involves the fabrication and testing of microporous, polymer membranes designed to remove minute amounts of toxic air pollutants such as formaldehyde from air streams. The hypothesis to be tested is that active, the silver contained within the porous polymer membranes results in high formaldehyde retention.</p><p>Monolayers consist of different sizes of sPS particles are assembled first on the silicon wafers by spin coating method and convective assembly method, respectively. Then each kind of monolayer with one dimension of sPS particles is deposited with a nanometer scaled silver thin film with a bench top metal evaporator. The porous membranes are produced by assembly of close-packed colloidal crystals of silver capped polystyrene template particles and subsequent infiltration with polyurethane prepolymer. The prepolymer is cured by UV exposure. The sPS particles are removed from the particle polymer membrane by treatment with organic solvents resulting in the formation of inverse opal structures. Silver does not dissolve in the organic solvents and cannot leave the pores due to the small size of connecting holes in an inverse opal. All the monolayers, cylindrical colloidal crystals and microcapillaries after infiltration of polyurethane had been characterized by optical microscope, and the porous membranes had been characterized by SEM.</p><p>The application of porous membranes with silver caps is to absorb formaldehyde in the air, while in fact the silver caps are oxidized and become Ag2O, which will initiate a gas-phase/solid reaction with formaldehyde. In the future, TiO2 will be applied together with Ag2O, since TiO2 is another good absorbent for formaldehyde</p>

Transparent conducting oxides (TCOs) are an important class of materials with many applications such as low emissivity coatings, or transparent electrodes for photovoltaics and flat panel displays. Among the possible TCO materials, Al-doped ZnO (AZO) is studied due to its relatively low cost and abundance of the raw materials. Thin films of AZO are commonly produced using physical vapour deposition techniques such as magnetron sputtering. However, there is a problem with the homogeneity of the films using reactive direct current magnetron sputtering (DCMS). This homogeneity problem can be related to the bombardment of the growing film with negative oxygen ions, that can cause additional acceptor defects and the formation of insulating secondary phases. In this work AZO films are deposited by high power impulse magnetron sputtering (HiPIMS), a technique in which high instantaneous current densities are achieved by short pulses of low duty cycle. In the first part of this thesis, the possibility to improve the homogeneity of the deposited AZO films by using HiPIMS is demonstrated. This improvement can be related to the high instantaneous sputtering rate during the HiPIMS pulses, so the process can take place in the metal mode. This allows for a lower oxygen ion bombardment of the growing film, which can help to avoid the formation of secondary phases. Another problem of AZO is the stability of the properties in humid environments. To assess this problem, the degradation of the electrical properties after an aging procedure was investigated for films deposited by both DCMS and by HiPIMS. A method was proposed, to restore the properties of the films, using a low temperature annealing under N2 atmosphere. The improvement of the electrical properties of the films could be related to a diffusion process, where water is diffusing out of the films. Then, the influence of the substrate temperature on the properties of AZO films deposited by HiPIMS was studied. The electrical, optical and structural properties were found to improve with increasing substrate temperature up to 600 ◦C. This improvement can be mostly explained by the increase in crystalline quality and the annealing of defects. Finally, the deposition of AZO films on flexible PET substrates was investigated. The films are growing as a thick porous layer of preferentially c-axis oriented columns on top of a thin dense seed layer. The evolution of the sheet resistance of the films after bending the films with different radii was studied. There is an increase in the sheet resistance of the films with decreasing bending radius, that is less pronounced for thicker films.

The electric vehicle itself today outlives its battery, necessitating battery replacement. Lithium titanium oxide (LTO) has, in this context, been suggested as a new anode material in heavy electric vehicle applications due to intrinsic properties regarding safety, lifetime and availability. The work presented here is focused on the LTO electrode/electrolyte interface. Photoelectron spectroscopy (PES) has been applied to determine how and if the usage of LTO could prevent extensive anode-side electrolyte decomposition and build-up of a surface layer. The presence of a solid electrolyte interphase (SEI) comprising LiF, carbonates and ether compounds was found in half-cells utilizing a standard ethylene:diethylcarbonate electrolyte with 1 M LiPF6. Via testing of symmetrical LTO-LTO cells, the stability of the formed SEI was put in to question. Moreover, the traditional polyvinylidene difluoride (PVdF) binder was replaced by more environmentally benign carboxylmethyl cellulose (CMC) and polyacrilic acid (PAA) binders in LTO electrodes, and it was found that CMC helped to form a more stable surface-layer that proved beneficial for long term cycling. Following the half-cell studies, full-cells were investigated to observe how different cathodes influence the SEI of LTO. The SEI in full-cells displayed characteristics similar to the half-cells, however, when utilizing a high voltage LiNi0.5Mn1.5O4 cathode, more electrolyte decomposition could be observed. Increasing the operational temperature of this battery cell generated even more degradation products on the LTO electrodes. Mn was also found on the anode when using Mn-based cathodes, however, it was found in its ionic state and did not significantly affect the composition or behavior of the observed SEI layer. Furthermore, by exchanging the electrolyte solvent for propylene carbonate, the thickness of the SEI increased, and by replacing the LiPF6 salt for LiBF4 the stability of the SEI improved. Thus is it demonstrated that such a passivation can be beneficial for the long-term surface stability of the electrode. These findings can therefore help prolong the lifetime of LTO-based battery chemistries.