This work addresses the growth of ultrathin magnetite (Fe3O4) and cobalt ferrite (CoFe2O4) films and their thorough structural, electronic, and magnetic characterization. In a first step, ultrathin Fe3O4 films are grown on SrTiO3(001) substrates by reactive molecular beam epitaxy (RMBE) and the substrate-induced anomalous strain behavior of the films is investigated by complementary high-resolution transmission electron microscopy (HRTEM) and (grazing incidence) X-ray diffraction [(GI)XRD] measurements. Next, an additional CoO film is deposited on similar Fe3O4/SrTiO3(001) heterostructures to demonstrate an alternative route for the synthesis of cobalt ferrite films through the thermally mediated interdiffusion of both oxide films. The evolution from the initial bilayer stacks to completely reacted cobalt ferrite films is extensively monitored by soft and hard X-ray photoelectron spectroscopy (soft XPS and HAXPES) and (GI)XRD. Complete intermixing and formation of single cobalt ferrite films is confirmed by angular-resolved HAXPES (AR-HAXPES) and X-ray reflectivity (XRR). The study of the cationic distribution resulting from this novel synthesis technique and its effects on the magnetic properties of the cobalt ferrite films is the subject of the subsequent part. Here, X-ray magnetic circular dichroism (XMCD) and superconducting quantum interference device (SQUID) magnetometry serve as key investigation techniques, which are further complemented by AR-HAXPES and atomic force microscopy (AFM) measurements. In a final step, highly crystalline cobalt ferrite films with different cationic stoichiometries are grown on MgO substrates using RMBE while their growth behavior is captured in real-time using operando XRD. Further structural characterization of the films is carried out by low-energy electron diffraction and XRR, whereas HAXPES and SQUID provide fundamental information on the electronic, chemical, and magnetic properties of the films.

No description available.

This study was motivated by the excess oxygen that likely results from the current transition to hydrogen-based Swedish steel production. The potential usability of large amounts of oxygen in a process gas for iron ore pellet induration could improve the process efficiency in terms of fuel consumption and productivity. Iron ore pellets constitute the main raw material used in Scandinavian steel production. Knowledge of the effects of the process-gas oxygen level on induration is a prerequisite for establishing if, how, and to what extent oxygen enrichment can be exploited in an optimum manner to control temperature development and oxidation, while maintaining pellet quality. The objectives of this study are as follows: 1) to investigate the effects of the oxygen level in the inflow gas on pellet bed oxidation during induration, as well as the effects on the bed-scale temperature, oxidation degree, and cold compression strength (CCS) development; and 2) to identify the oxidation mechanisms corresponding to various oxygen levels and thermal histories. The current knowledge regarding the effects of high oxygen levels in the gas on oxidation is based on small-scale experiments; this study was conducted on a larger bed-scale and will thus contribute significantly to the knowledge pool of bed-scale effects resulting from different oxygen levels in the inflow process gas. An interrupted pot furnace experimental method was used, with the highest investigated oxygen level in the gas at 40% and an approximate bed-scale of 100 kg of pellets. The following conclusions were drawn from this study. First, efficient heating and a high degree of oxidation of an entire bed were rapidly achieved with the highest investigated oxygen level (40% O₂) compared to the results of the lower oxygen levels (6%, 13% and 30% O₂). The gas with 40% O₂ yielded improved pellet properties and a more uniform oxidation degree along the bed, compared to beds exposed to gas with lower O₂. Second, the temperature at the bottom of the bed increased more rapidly when exposed to a higher oxygen content in the gas compared to when only the gas temperature was increased. Third, the mechanical pellet properties (CCS and macrostructure) were improved in a bed exposed to gas with 40% O₂ compared to beds exposed to gas with lower oxygen levels. Finally, pellets from local conditions with comparable thermal histories oxidised according to similar mechanisms regardless of the oxygen level. Hence, it was demonstrated that the oxygen level influences the oxidation rate, whilst the temperature affects the oxidation mechanism. The overall trends in terms of the positive effect from the high oxygen content in the gas are promising, as they serve as a starting point for enabling faster production rates in the future. / <p>E632 and a digital meeting in Zoom or Teams. Maximum 8 people will be allowed in E632 due to the covid-19 pandemic situation.</p> / HYBRIT research program 1

No description available.

Superhydrophobic coatings (SHC) with excellent self-cleaning and corrosion resistance property is developed on magnetite coated AISI SAE 1020 steel by using a simple immersion method. Roughness measurement, scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), contact angle measurement (CAM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), potentiodynamic polarization test, electrochemical impedance spectroscopy (EIS), and qualitative characterization of self-cleaning behavior, antifouling property and durability of the coatings are assessed. A water contact angle as high as 152o on the coated surface with excellent self-cleaning and resistivity to corrosion and good longevity in atmospheric air is obtained. Self-cleaning test results prove that these surfaces can find applications in large scale production of engineering materials. Potentiodynamic polarization tests and EIS tests confirm that the superhydrophobic low carbon steel surfaces have better resistance to corrosion compared to bare steel and magnetite coated steel in 3.5% NaCl solution. But the longevity of the coated steel surfaces in 3.5% salt solution is limited, which is revealed by the immersion durability test. However, hydrophobic coatings (HC) have better stability in normal tap water, and it can stay unharmed up to 15 days. Finally, hydrophobic coatings on low carbon steel surface retains hydrophobic in open atmosphere for more than two months. Results of this investigation show surface roughness is a critical factor in manufacturing hydrophobic steel surfaces. Higher contact angles are obtained for rougher and more uniform surfaces. A linear mathematical relationship (y =6x+104; R2 = 0.93) is obtained between contact angle (y) and surface roughness (x).

No description available.

No description available.

Polylactide homopolymers with pendent carboxylic acid functional groups have been designed and synthesized to be studied as magnetite nanoparticle dispersion stabilizers. Magnetic nanoparticles are of interest for a variety of biomedical applications including magnetic field-directed drug delivery and magnetic cell separations. Small magnetite nanoparticles are desirable due to their established biocompatibility and superparamagnetic (lack of magnetic hysteresis) behavior. For in-vivo applications, it is important that the magnetic material be coated with biocompatible organic materials to afford dispersion characteristics or to further modify the surfaces of the complexes with biospecific moieties. The acid-functionalized silane endgroup was utilized as the dispersant anchor to adsorb onto magnetite nanoparticle surfaces and allowed the polylactide to extend into various solvents to impart dispersion stability. The homopolymers were complexed with magnetite nanoparticles by electrostatic adsorption of the carboxylates onto the iron oxide surfaces, and these complexes were dispersible in dichloromethane. The polylactide tailblocks extended into the dichloromethane and provided steric repulsion between the magnetite-polymer complexes. The resultant magnetite-polymer complexes were further incorporated into controlled-size nanospheres. The complexes were blended with poly(ethylene oxide-b-D,L-lactide) diblock copolymers to introduce hydrophilicity on the surface of the nanospheres with tailored functionality. Self-assembly of the PEO block to the surface of the nanosphere was established by utilizing an amine terminus on the PEO to react with FITC and noting fluorescence. / Ph. D.

Superparamagnetic nanoparticles have potential applications in targeted drug delivery and as magnetic resonance imaging contrast agents. Magnetite clusters are of particular interest for these applications because they provide higher magnetic flux (under a magnetic field) than individual magnetite nanoparticles, are biocompatible, and their size and compositions can be controlled. This thesis involves the controlled synthesis and characterization of clusters composed of magnetite nanoparticles stabilized with an amphiphilic block copolymer. It outlines a method to design and form well-defined and colloidally stable magnetite clusters. A Multi Inlet Vortex mixer (MIVM) was used because it is a continuous process that yields particles with relatively narrow and controlled size distributions. In the MIVM, four liquid streams collide under turbulent conditions in the mixing chamber where clusters form within milliseconds. The formation of magnetite clusters was studied in the presence of amphiphilic block copolymers containing poly (ethylene oxide) to provide steric stabilization and control of size distributions using flash nanoprecipitation. First, the mixer was tested using β-carotene as a model compound to form nanoparticles stabilized with an amphiphilic triblock copolymer poly(propylene oxide)-b-poly(ethylene oxide) (F127) at different Reynolds numbers and supersaturation values. Size analysis was done using dynamic light scattering and nanoparticle tracking analysis techniques. The cluster structure was studied using electron microscopy and magnetite compositions were measured using thermogravimetric analysis. Finally, the stability of magnetite clusters was studied over time and the effect of an applied magnetite field on the colloidal stability was investigated. / Master of Science

Interaction between minerals and bacteria represents an abundant natural phenomenon depictingnature's complexity and how abiotic and biotic components are intertwined. This interaction is evidentin modern-day ecosystems, and it significantly shaped the early stage of life on Earth by influencinggeochemical processes. Evidence of this interaction includes microbialites. In the first part, this master's thesis explores the impact of iron-redox bacteria on the magneticproperties of synthetic and natural magnetic materials, with significant implications for understandingearly Earth conditions and paleoenvironments. In the second part, the magnetic signal recorded in thesediment core from the Baltic Sea is examined to identify the ferrimagnetic minerals responsible for itand their origin (biotic versus abiotic). A better understanding of the origin of ferrimagnetic mineralsallows for a more conclusive interpretation of palaeomagnetism and palaeoenvironmental history of theBaltic Sea. In both parts, the change in magnetic susceptibility was used as the main method to depictmechanisms of mineral-bacteria interaction. Experiment with iron-oxidising bacteria (Leptothrix mobilis) showed a decrease in magneticsusceptibility over time, consistent with the oxidation of solid iron/magnetic materials. However, asmall difference between bacteria culture and control samples points out that the decrease is caused byabiotic oxidation rather than bacterial. Supporting evidence is the absence of viable cells in all bacterialsamples, suggesting that L. mobilis did not grow in these experiments. In experiments with iron-reducing bacteria (Geobacter sulfurreducens), magnetic susceptibility increased by 7%. Controlsamples with the same reducing media did not show a change in magnetic susceptibility, indicating thatthe susceptibility change is caused by bacterial reduction of iron oxides. Magnetic susceptibility signal obtained in the sediment core from the Baltic Sea indicates rapidlyoxidising, ferrimagnetic nanoparticles in two organic-rich sapropels. The pattern of the signal isconsistent with the presence of bacterial greigite (magnetofossils). Contrary to previous research, nomagnetic enhancement is observed in these layers.  Magnetic susceptibility, as a non-destructive and relatively simple method, may serve as a significantindicator of mineral-bacterial interactions. Combining it with other techniques and methods can providedeeper insights into the mechanisms behind these interactions. This approach can reveal the importanceof these interactions on early Earth, enhance our understanding of palaeomagnetism, and unveil possibleconditions of ancient environments.