The final objective of this study is to produce chemical models of flotation- like systems, including oxidation products of magnetite (maghemite and hematite) together with apatite. This is started by investigating the acid base properties, surface complexation and surface characteristics of the systems hematite-H+ and maghemite-H+ (paper I), fluorapatite-OH- (paper II) and a mixed system of maghemite-fluorapatite-OH- (paper III). Synthetic minerals were prepared and characterised with BET, SEM, XRD, FT-IR and FT- Raman. The acid base properties were investigated using high precision emf potentiometric titrations and z-potential measurements. Titration data were interpreted using models based on the theory of surface complexation, assuming the formation of surface complexes with charge dependent formation constants. The constant capacitance model was applied to interpret titration data for all three systems. The obtained models will contribute to a better understanding of the reactions during the apatite/magnetite separation by flotation. The surface site density Ns (sites/nm2) for maghemite was found to be very low compared to other iron oxides. The mixed system of maghemite and fluorapatite was interpreted with two different models. FT-Raman together with the Ns (sites/nm2) value reveals that interactions occurred between the fluorapatite and maghemite particles in the system. These interactions have to be chemical or sterical, because both surfaces are negatively charged in the actual pH-range. / Godkänd; 2004; 20070127 (ysko)

Godkänd; 1997; 20070418 (ysko)

No description available.

Climate change is one of the greatest challenges of the 21st century and is the reason for several environmental changes on earth. One reason behind climate change includes the rise ingreenhouse gas emissions in the atmosphere due to the burning of coal, gas and oil, i.e. fossil fuels. Fossil fuels are currently the world’s primary source of energy and alternative solutions are there for necessary to mitigate climate change, for example by utilizing solar cells. Perovskite solar cells have gain a lot of attention due to its rapid improvement in power conversion efficiency. In parallel with the advances in performance and stability, the challenges of commercialization have arisen. Therefore scalable technology is required to facilitate for large-area fabrication as well as a quality improvement in the perovskite film. The purpose of this project was to characterize the optical properties and functions of the perovskite solar cell when using the precursor solution of Cs0.1FA0.9Pb(I0.9Br0.1)3 for semi-upscaled technique. Additionally, this project investigated different elements in the slot-die coater process to optimize the performance of the solar cell, including the fabrication process of the precursor solution, the size of the substrates and to optimize the functionality of the electron transport layer. Four different trials were conducted in this study using a solution-based technique from  Cs0.1FA0.9Pb(I0.9Br0.1)3 perovskite powder while varying different parameters in the cell design and geometric shapes of the substrates. These trials were compared to a reference trial using Cs0.1FA0.9PbI3 through solar cell characterization and material characterization, including current-voltage measurements, incident photon-to-current efficiency, X-ray diffraction, UV/vis/NIR spectrophotometry and scanning electron microscopy. The results show that the power conversion efficiency increased when adding bromide into the perovskite structure. Furthermore, a shift in the band gap was observed during the material characterization. Trial 4 consisted of using SnO2 as the electron transport layer, developing a powder perovskite and adding a 2D additive layer to the cell design, displayed the best performance. In conclusion, the addition of bromide in Cs0.1FA0.9Pb(I0.9Br0.1)3 did increase the performance of the solar cells and the band gap of the perovskite solar cells was tunable.

This project investigates how different types of perovskite solar cells, differentiated by choice of materials and processing techniques, compares to each other regarding performance and characterization. The purpose of the project is to further develop perovskite solar cells and to improve the method of manufacturing for better performance. A total of 160 perovskite solar cells are constructed, divided into eight distinct types. Two different perovskites, MAPbI3 and MAFAPbI3, are used and prepared using two different solvents: isopropanol (IPA) and pentanol (PenOH). Furthermore half of the solar cells contain phenethylammonium iodide (PEAI). When completed, the solar cells' performances are measured and compared. Lastly, the solar cells and the perovskites are compared through characterization measurements. An incident-photon-to-current-efficiency (IPCE) spectroscopy is performed on the solar cells to get a better understanding of the efficiency depending on the wavelength of the incident light. An UV-vis-NIR spectroscopy is performed on the thin film to analyze the absorbance and determine the band gap of the material. The pre-crystallized perovskite powders are compared through characterization measurements, such as X-ray Photoelectron Spectroscopy (XPS) characterization and scanning electron microscopy (SEM) measurements. This results in comparing material compositions and optical properties of the solar cells. The results indicate that MAPbI3 (PenOH) is the highest performing type independent of the presence of PEAI. The measured mean power conversion efficiency (PCE) are 15.47% and 13.84% for MAPbI3 (PenOH) with and without PEAI respectively. The best performing individual solar cell contains MAPbI3 (PenOH) with PEAI and has a PCE of 20.21%. On the contrary, MAFAPbI3 (PenOH) with and without PEAI perform the worst. The best improvement of the PCE after two weeks is +22.13%, given by MAPbI3 (PenOH) with PEAI. Generally, solar cells with MAPbI3 have a larger band gap, 1.61 eV, compared to MAFAPbI3's 1.55 eV, regardless of the presence of PEAI. MAPbI3 (PenOH) can convert a larger portion of incident photons to electrical energy, up to almost 80%. MAFAPbI3 (IPA) converts almost as much, over 70%, while MAPbI3 (IPA) and MAFAPbI3 (PenOH) in some measurements barely has a 50% conversion rate.

Organic photovoltaics is a promising environmentally friendly technology, due to their printability, light-weight nature and mechanical flexibility, and the possibility to use off-grid. Research and development in this field has resulted in power conversion efficiencies of over 15%. To further improve the efficiency, it is important to understand the connection between the morphology of the active layer and the performance of the device.  This thesis focuses on understanding on a molecular level of the morphology formation in a thin coated film of a polymer bend, using two different approaches. One approach will focus on the thermodynamics of conjugated polymers in relation to the morphology, by using the Hansen solubility Parameters (HSP) and solution chemistry. The second approach focuses on understanding phase separation between the two polymers in the active layer. To be able to study phase separation, films were fabricated under microgravity conditions, as previous studies show that in these conditions phase separation mechanism is slowed down. Atomic force microscopy is used to characterize the resulting morphology of the thin films.  Preliminary studies in this thesis showed that using HSP is a good tool, to understanding solvent-solute and solute-solute interactions in solution and to guide the final film morphology in relation to solubility. Furthermore, HSP is a good tool for the preliminary screening of alternative solvents and solvent blends for environmentally friendly processing solvents for upscaling. It was also found that dip coating of films under microgravity conditions provides a tool to study the early stages of the phase separation, as well as facilitate the study of the dependence of the morphology on the thicknesses of the coating. More work is needed to be able to separate the complex effect of hypergravity and to eliminate uncertainty concerning if the deposited wet film is completely dried under the microgravity phase.

The main objectives for this licentiate thesis have been to study and model the reactions at the water-mineral interface of two subsystems: maghemite-H+-silicate and olivine-H+. An increased knowledge of these systems will make it possible to further extend the complexity of the aqueous phase in future experiments. This will make it possible to further approach a composition that resembles the flotation and agglomeration process water in the production of iron ore pellets. To be able to characterise and predict the influence of different species from the process water on the different mineral particle surfaces, is an important step towards optimisation of the pellet production process and increased recirculation of the process water. Both synthetic and natural minerals were used in the experiments, in which the protolytic surface exchange reactions of the subsystems were analysed by high precision potentiometric titrations. The minerals and their surfaces were characterised using XRD, XPS, SEM-EDS and BET, both before and after the experiments. The zeta potential of olivine and silicate modified maghemite particles were also determined as a function of pH. Surface complexation models were derived to describe the reactions in the systems. The Constant Capacitance Model (CCM) was used to model the experimental results.The evaluation of the potentiometric data from the studies of the maghemite-H+-silicate system indicates that soluble silicates will mainly adsorb to maghemite as monodentate surface species at the defined experimental conditions. Models including polymerisation of adsorbed silicates and/or bidentate silicate ligands were tested, but could not well be fitted to titration data. The adsorption maximum of silicates was found to be within the range pH 9.0 to 9.5. At the experimental conditions used, approximately 82 % of the added silicate was adsorbed. At higher pH, the silicate started to desorb from the maghemite surface and at pH 11.1 only 60 % was still adsorbed. Olivine ((Mg,Fe)2SiO4), one of the major rock forming silicate minerals in nature, is added in the agglomeration process to improve the performance of the iron ore pellets in the blast furnace. The results from the studies of the olivine - H+ system shows that the dissolution of olivine is essentially incongruent, with an excess of magnesium ions released in to the aqueous suspension. Studies of olivine samples equilibrated in electrolytes with magnesium ions added using XPS, SEM and zeta potential measurements have also shown that the magnesium ion release and adsorption at the surface layers is reversible, no support for surface precipitation of new phases as Mg(OH)2 could be found. Experimental potentiometric data of olivine-H+ at alkaline conditions was successfully fitted to a two pKa electrostatically corrected model. The importance of steady state conditions when acquiring titration data was illustrated by comparing the amount of active surface sites detected by steady state titrations and considerably faster titrations.

Developing new technological solutions, such as use of lightweight materials, less harmful fuels, controlled fuel combustion processes or more efficient exhaust gas after-treatment, are possible ways to reduce the environmental impact of machines. Both the reduction of wear and the friction control are key issues for decreasing of energy losses, improving efficiency and increasing of the life-span of an engine. Dialkyldithiophosphates (DTPs) of different metals have been extensively used as multifunctional additives in lubricants to control friction and reduce wear in mechanical systems. Among these DTP-compounds, zinc dialkyldithiophosphates (ZnDTPs) are the most common additives used for more than 60 years. These additives form protective films on steel surfaces and, thus, control friction and reduce wear. However, ZnDTPs contain zinc and large amounts of phosphorus and sulphur, which are human health hazards and cause environmental pollution by degrading catalytic converters in automobiles. Therefore, replacement of ZnDTPs byzinc free compounds with reduced amounts of sulphur and phosphorus are urgently needed.Boron-containing compounds are known as corrosion inhibitors, antioxidants, friction modifiers and effective anti-wear additives either dissolved in oil or as an insoluble and inorganic borate salts dispersed in oil in the nanoparticulate form. These compounds are emerging as attractive replacements for the compounds already used as additives in lubricants. The focus of the present work is on the development and tribological investigations of new boron compounds as highperformance additives in lubricants. These should be ashless with significantly reduced amounts sulphur and phosphorus, which is favourable for the environment protection. The work was carried out in the following steps: (1) Synthesis of new additives; (2) Characterization of the additives with FTIR, (1H, 13C, 31P, 11B) NMR spectroscopy, elemental analysis and thermal analysis (TG/DTG, DTA and QMS); (3) Tribological evaluation using four ball Tribometer; (4) Surface analysis using an optical profiler and Scanning Electron Microscopy coupled with X-ray Energy Dispersive Spectroscopy (SEM/EDS). It was found that the novel boroncompounds have considerably better antiwear performance and higher stability of the coefficient of friction with time as compared with ZnDTP. These novel compounds are ashless with reduced amounts of sulphur and phosphorus. They also have excellent tribological properties, high thermal stability, good miscibility with oils and positive environmental issues which make them an attractive alternative to ZnDTP.

Lubricants are used to control friction and reduce wear by preventing direct contact between surfaces in a relative motion. Most of the modern lubricants and lubricant additives have been designed and optimized for ferrous materials. A growing trend towards wider use of lightweight and wear resistant non-ferrous materials calls for new efficient and environmentally friendly Lubricants. Boron compounds are attractive alternatives for the commercially available lubricants and lubricant additives. Some boron compounds have already been proven as efficient friction modifiers, antioxidants, corrosion inhibitors and antiwear additives in lubricants.In this work we focus on design, synthesis, physicochemical characterization and tribological studies of novel boron compounds. Boron based ionic liquids (ILs) and dithiocarbamates (B-DTCs) were designed, synthesized and tribologically characterized. The work was carried out in the following steps: (i) design and synthesis of novel boron compounds; (ii) physicochemical characterization of the synthesized compounds by FTIR, liquid-state (1H, 13C, and 11B) and solid-state (13C and 11B) nuclear magnetic resonance (NMR) spectroscopy, elemental analysis, thermal analysis (TG, DTA, DSC and QMS), powder XRD, density and viscosity measurements; (iii) tribological characterization using four-ball and pin-on-disc tribometers and (iv) surface analysis using Scanning Electron Microscopy coupled with X-ray Energy Dispersive Spectroscopy (SEM/EDS), optical interferometer and stylus profilometer. Some of these new boron-based compounds revealed significantly better antiwear and friction reducing performance on steel-steel contacts compared with fully formulated engine oils. (i) Nine novel ILs of pryrrolidinium bis(salicylato)borate were synthesized and physicochemically characterized. They are solid at room temperature and some of them behave as plastic crystals. Some of these ILs were tested as lubricants at 100 ºC, i.e. above their melting points. These ILs have shown significantly better antiwear and friction reducing performance in lubrication of steel-steel contacts compared to fully formulated synthetic engine oil 5W40.(ii) Nine novel room temperature ionic liquids (RTILs) of pyrrolidinium bis(mandelato)borate were synthesized and physicochemically characterized. These ILs were tribologically tested as 3 wt % additives in polyethylene glycol (PEG) and they have shown considerably better antiwear and friction reducing properties in boundary lubrication of steel-steel contacts at room temperature compared with neat PEG and engine oil 5W40.(iii) Boron based compounds containing alkylborate and dithiocarbamate groups with alkyl substitutes in one molecule were synthesized and physicochemically characterized. The influence of alkyl chain length (butyl and/or octyl substitutes at DTC and borate groups) and heterocyclicity in boron based dithiocarbamate compounds (B-DTCs) on their tribophysical properties as additives in a mineral oil was studied for steel-steel lubricated contacts.

Decontamination of industrially polluted waters has been enclosed in REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) since 2007, when it entered into force in the European Union, which emphasized the need to search for more effective sorbents. Many studies on inorganic ion-exchangers have been carried out due to the scientific interest towards their high mechanical and thermal stabilities, high resistance to oxidation and high sorption capacity regarding transition and radioactive metal ions. Titanium phosphates (TiP) in particular, have revealed very good cation-exchange properties in relation to different transition metal ions in aqueous solutions. It has been demonstrated that their physicochemical properties as well as their structural characteristics can be altered by carefully choosing the conditions of synthesis: the temperature, acidity, Ti(IV) speciation in solution and reaction time. Since the ‘classical’ crystalline TiP ionites have been divided into two main groups: alfa type; α-TiP [α-Ti(HPO4)2•H2O] and gamma type; γ-TiP [Ti(H2PO4)(PO4)•H2O] with different functional groups (–H2PO4, –HPO4 and –PO4) present, the researchers have focused on synthesis of various metastable TiP with different functional properties. In this work, three different synthetic routes for TiP ion-exchangers were explored in order to obtain a sorbent composed solely of –H2PO4 exchange units. The ─H2PO4 groups were expected to considerably increase the pH working range of the sorbents and to nearly double the theoretical exchange capacity of TiP ion-exchangers containing mostly –HPO4 functional groups. Among the synthesized ion-exchangers (TiP1, TiP2 and TiP3), TiP1 has shown very good sorption characteristics and therefore, most of the studies were performed on it. TiP1 was synthesized at mild thermal conditions using cobalt(II) ions as a modifying agent and HCl-washes as post-synthetic treatments. This sorbent was characterized by different spectroscopic techniques and its chemical formula was established to be: TiO(OH)(H2PO4)•H2O. The sorption capacity of TiP1, estimated about 4.8 meq.g-1, is higher than the reported exchange capacity for various amorphous TiP. The sorption characteristics of TiP1 towards divalent ions such as Cu2+, Zn2+, Ni2+, Mn2+ and Co2+, were investigated in this work. The results of the sorption experiments (in the 1-20 mmol.L-1 range) were fitted to the Langmuir and Temkin models with the latter one being somewhat preferred for most of the metal ions studied. This indicates that interactions between adsorbed molecules cannot be neglected. It was also found that the kinetics of the ion-exchange process was very fast and the equilibrium was reached within 10 minutes. The kinetic data were modeled using the pseudo-second order reaction rate and the obtained curves were consistent with chemisorption being the rate limiting step of the reactions. The selectivity order of the metal ions studied towards TiP1 here was found to be: Cu2+ > Zn2+ > Mn2+ > Co2+ > Ni2+. The TiP1 sorbent has also shown to be a very good cation-exchanger when batch experiments were performed using heavy metals polluted waters from closed mines, supplied by Boliden AB. These studies delineated that TiP1 has displayed exclusive sorption capacities and imminent ion-exchange kinetics. It has been distinctly shown that a modest change in the synthesis could facilitate the fabrication of titanium phosphate ion-exchangers with improved and versatile sorption properties.