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. 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. 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

This research thesis covers work done on building an atomic layer deposition (ALD) reactor followed by the development and optimization of an ALD process for indium oxide thin films on crystalline silicon substrates from new precursors using this new homebuilt cost-effective tool. This work describes the design, building and testing of the ALD system using an indium triazenide precursor and water in a novel precursor combination. The reactor was built to be capable of depositing films with comparable results to commercially built systems.Indium oxide thin films were deposited as the deposition temperature was varied from 154 to 517 0C to study the effects of deposition temperature on the obtained film thicknesses and ascertain the ALD temperature window between 269-384 0C. The presence of indium oxide films was confirmed with X-ray diffraction analysis, which was also used to study their crystallinity. The films were found to have a polycrystalline structure with a cubic phase. Measurement of film thickness was performed using X-ray reflectivity which determined a growth rate of approximately 1 Å/cycle. Elemental composition was determined by X-ray photoelectron spectroscopy which confirmed contamination-free indium rich films. Scanning electron microscope imaging was used to examine the surface morphology of the films as well as thick cross-sectional thicknesses.Since indium oxide films are potentially useful in various electronic, optical, and catalytic applications, emphasis is also placed on the accurate characterization of the chemical and physical properties of the obtained thin films. Optical and electrical properties of the produced transparent conducting oxide films were measured for transparency (and optical band gap) and electrical characterization by resistivity measurements, from UV-Vis spectrophotometry and 4-point probe data respectively. A high optical transmission >70 %, a wide band gap 3.99-4.24 eV, and low resistivity values ∼0.2 mΩcm, showed that In2O3 films have interesting properties for various applications confirming indium oxide a key material in transparent electronics.

This master thesis was a part of an ongoing project at Research institutes of Sweden (RISE) and Chalmers University of technology, studying the formation of white layers (WLs) upon hard machining AISI 52100 steel. With a focus on the nanocrystalline microstructure of the machined steel, X-ray diffraction (XRD), white light interferometry (WLI), optical microscopy (LOM) and scanning electron microscopy (SEM) was utilized in the analysis of gathering an in-depth understanding of the WL formation mechanism. By introducing varying cutting parameters as part of the machining process, the effect of cutting speed and tool wear could be observed to directly impact the WL formation and could be linked to the thermomechanical contribution to the formation mechanism. Both thermal and mechanical WLs were observed and could be distinguished by the occurrence of dark layers in thermal WLs. The purpose of this thesis was to observe the influence of retained austenite (RA) on WL formation and from the XRD analysis the residual stress for different RA content could not be concluded. Furthermore, SEM concluded differences in the microstructure where a higher abundance of carbides was observed in the case of lower RA, a phenomenon most likely originating in the heat treatment process. Indications of facilitated mechanical WL formation for lower RA was observed but could not be deemed conclusive. The RA content could not be concluded to have an impact on the surface roughness nor the residual stress where variations were rather linked to the cutting parameters.

There is a constant search for new sustainable materials. A material that has become increasingly more interesting is cellulose, since it is both renewable and biodegradable. By combining cellulose nanofibrils (CNF) and the polymer complex poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), a conductive hydrogel can be made. The hydrogel can subsequently be used to 3D-print various structures, which further can be used in multiple applications such as microrobots, sensors and smart devices. The aim of this bachelor thesis was to develop a 3D-printable hydrogel composed of PEDOT:PSS and CNF was made. The goal was to print and crosslink a conductive structure, and subsequently induce electrical current through the structure to facilitate movement (i.e. artificial muscles). Several hydrogel inks composed of CNF and PEDOT:PSS were prepared across a range of concentrations. Homogenisation of the hydrogels was achieved through various mixing techniques. Both freeze-drying and evaporation were tested to concentrate the hydrogels. Furthermore, crosslinking tests were performed using iron(III)chloride hexahydrate and citric acid, followed by a conductivity measurement. Lastly, rheology tests were performed on four of the inks. The optimal concentration of solid material was determined to be 4.8 wt% and the most favourable way of concentrating the hydrogels was by freeze drying. Furthermore, iron(III)chloride hexahydrate was found to be more favourable when crosslinking the hydrogels. The conductivity measurements showed that crosslinking with iron(III)chloride hexahydrate resulted in a notable increase in conductivity in the material. Lastly, the rheology measurements showed that the 4.8 wt% hydrogel ink had high elasticity, viscosity and exhibited shear thinning behaviour. / Det söks konstant efter nya hållbara material. Ett material som har blivit alltmer intressant är cellulosa, eftersom det både är förnybart och bionedbrytbart. Genom att kombinera cellulosa nanofibriller (CNF) och polymer komplexet poly(3,4-etylendioxitiofen) polystyrensulfonat (PEDOT:PSS), kan en konduktiv hydrogel framställas. Denna hydrogel kan sedan användas för att 3D-printa en mängd olika strukturer, vilka senare kan används i olika tillämpningar så som mikrorobotar, sensorer och smarta enheter. Målet med detta kandidatarbete var att utveckla en hydrogel av PEDOT:PSS och CNF för användning i 3D-skrivare. Målet var att printa och korslänka en struktur med konduktiva egenskaper, vilken senare skulle induceras med elektricitet för att främja rörelse, med andra ord artificiella muskler. Ett flertal hydrogeler av CNF och PEDOT:PSS förbereddes i en rad olika koncentrationer. Homogenisering av hydrogelerna uppnåddes genom att testa olika metoder för omrörning. Både frystorkning och avdunstning testades för att koncentrera hydrogelerna. Dessutom undersöktes tvärbindning genom järn(III)kloridhexahydrat och citronsyra, följt av en konduktivitetsmätning. Slutligen utfördes reologimätningar på fyra av de framställda hydrogelerna. Den optimala koncentrationen av fast material i en hydrogel bestämdes till 4,8 vikt% och det mest gynnsamma sättet att koncentrera hydrogeler var genom frystorkning. Vidare, var järn(III)kloridhexahydrat ett mer fördelaktigt alternativ vad gällde tvärbindning av hydrogelerna. Konduktivitetsmätningarna visade att tvärbindning med hjälp av järn(III)kloridhexahydrat ökade konduktiviteten märkbart hos materialet. Slutligen visade reologimätningarna att hydrogelen med 4,8 vikt% hade hög elasticitet, viskositet och den uppvisade även skjuvningstunnande beteende.

Lithium-ion battery (LIB) technology is currently the most promising candidate for power sources in applications such as portable electronics and electric vehicles. In today's state-of-the-art LIBs, non-aqueous electrolytes are the most widely used family of electrolytes. In the present thesis work, efforts are devoted to improve the conventional LiPF6-based electrolytes with additives, as well as to develop alternative lithium 2-trifluoromethyl-4,5-dicyanoimidazole (LiTDI)-based electrolytes for silicon anodes. In addition, electrode/electrolyte interfacial chemistries in such battery systems are extensively investigated. Two additives, LiTDI and fluoroethylene carbonate (FEC), are evaluated individually for conventional LiPF6-based electrolytes combined with various electrode materials. Introduction of each of the two additives leads to improved battery performance, although the underlying mechanisms are rather different. The LiTDI additive is able to scavenge moisture in the electrolyte, and as a result, enhance the chemical stability of LiPF6-based electrolytes even at extreme conditions such as storage under high moisture content and at elevated temperatures. In addition, it is demonstrated that LiTDI significantly influences the electrode/electrolyte interfaces in NMC/Li and NMC/graphite cells. On the other hand, FEC promotes electrode/electrolyte interfacial stability via formation of a stable solid electrolyte interphase (SEI) layer, which consists of FEC-derivatives such as LiF and polycarbonates in particular. Moreover, LiTDI-based electrolytes are developed as an alternative to LiPF6 electrolytes for silicon anodes. Due to severe salt and solvent degradation, silicon anodes with the LiTDI-baseline electrolyte showed rather poor electrochemical performance. However, with the SEI-forming additives of FEC and VC, the cycling performance of such battery system is greatly improved, owing to a stabilized electrode/electrolyte interface. This thesis work highlights that cooperation of appropriate electrolyte additives is an effective yet simple approach to enhance battery performance, and in addition, that the interfacial chemistries are of particular importance to deeply understand battery behavior.

This PhD thesis presents investigations of hydrogen incorporation in Zintl phases and transition metal oxides. Hydrogenous Zintl phases can serve as important model systems for fundamental studies of hydrogen-metal interactions, while at the same time hydrogen-induced chemical structure and physical property changes provide exciting prospects for materials science. Hydrogen incorporation in transition metal oxides leads to oxyhydride systems in which O and H together form an anionic substructure. The H species in transition metal oxides may be highly mobile, making these materials interesting precursors toward other mixed anion systems.  Zintl phases consist of an active metal, M (alkali, alkaline earth or rare earth) and a more electronegative p-block metal or semimetal component, E (Al, Ga, Si, Ge, etc.). When Zintl phases react with hydrogen, they can either form polyanionic hydrides or interstitial hydrides, undergo full hydrogenations to complex hydrides, or oxidative decomposition to more E-rich Zintl phases. The Zintl phases investigated here comprised the CaSi2, Eu3Si4, ASi (A= K, Rb) and GdGa systems which were hydrogenated at various temperature, H2 pressure, and dwelling time conditions. For CaSi2, a regular phase transition from the conventional 6R to the rare 3R took place and no hydride formation was observed. In contrast, GdGa and Eu3Si4 were very susceptible to hydrogen uptake. Already at temperatures below 100 ºC the formation of hydrides GdGaH2-x and Eu3Si4H2+x was observed. The magnetic properties of the hydrides (antiferromagnetic) differ radically from that of the Zintl phase precursor (ferromagnetic). Upon hydrogenating ASi at temperatures around 100 oC, silanides ASiH3 formed which contain discrete complex ion units SiH3-. The much complicated β – α order-disorder phase transition in ASiH3 was evaluated with neutron powder diffraction (NPD), 2H NMR and heat capacity measurements.  A systematic study of the hydride reduction of BaTiO3 leading to perovskite oxyhydrides BaTiO3-xHx was done. A broad range of reducing agents including NaH, MgH2, CaH2, LiAlH4 and NaBH4 was employed and temperature and dwelling conditions for hydride reduction examined. Samples were characterized by X-ray powder diffraction (XRPD), thermal gravimetric analysis and 1H NMR. The concentration of H that can be incorporated in BaTiO3-xHx was found to be very low, which is in contrast with earlier reports. Instead hydride reduction leads to a high concentration of O vacancies in the reduced BaTiO3. The highly O-deficient, disordered, phases - BaTiO3-xHy□(x-y) with x up to 0.6 and y in a range 0.05 – 0.2 and (x-y) &gt; y – are cubic and may represent interesting materials with respect to electron and ion transport as well as catalysis. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 5: Manuscript.</p>

Additive manufacturing (AM) for metals is a manufacturing process that has increased a lot in popularity last few years as it has experienced significant improvements since its beginning, both when it comes to accuracy and deposition rates. There are many different AM processes where the energy sources and deposition methods varies. But the common denominator is their layer wise manufacturing process, melting layer on layer. AM has a great design freedom compared to conventional manufacturing, making it possible to design new structures with decreased weight and increased performance.  A drawback is slow manufacturing speeds, making it more expensive. But when it comes to low lot sizes and complex structures AM is very competitive. So, for the aerospace and space industry AM is a good option as manufacturing cost is less of an issue and where saving weight is of great concern, both environmentally and economically.  There are however many topics left to research before additive manufactured titanium can be widely adopted for critical components, such as microstructure and texture development and its correlation to mechanical properties. The aim of this work has been to investigate the microstructure and texture of various AM processes. Microstructural features such as prior β grains, grain boundary α (GB-α), α laths, α colonies have been characterized along with hardness measurements for 5 different AM processes. Some of these AM processes have also been investigated in the SKAT instrument in Dubna, Russia, to obtain their texture. These textures have then been compared with one another and correlated to previous microstructural investigations and mechanical properties. This is important knowledge as the microstructure and the texture sets the basis for the mechanical properties. In case there is a high texture, the material can have anisotropic mechanical behavior, which could be either wanted or unwanted for different applications.   Some the findings are that α phase was found to increase in the prior β grain boundary for the AM processes with low cooling rates, while it was discontinuous and even non-present for the AM processes with high cooling rates. The prior β size are larger for the directed energy deposition (DED) processes than for the powder bed fusion (PBF) processes. Parallel bands were present for the DED process while being non-present for the PBF processes. Concerning the texture, it was found that LMwD had a higher texture than EBM and SLM. Texture inhomogeneity was also found for the LMwD process., where two parts of the same sample was investigated and the material closer to the surface had higher texture.

Diamond is an important material in many industrial applications (e.g., machining of hard materials, bio-electronics, optics, electronics, etc.) because of its exceptional properties such as hardness, tolerance to aggressive environments, compatibility with human tissues, and high carrier mobility. However, a highly controlled method for growing artificial high-purity diamond on a range of different substrates is needed to exploit these exceptional properties. The Chemical Vapour Deposition (CVD) method is a useful tool for this purpose, but the process still needs to be developed further to achieve better control of growth. In this context, the introduction of dopant species into the gas phase has been shown to strongly influence growth rate and surface morphology. Density Functional Theory (DFT) methods are used to deepen our atomic-level understanding of the effect of dopants on the mechanism for CVD growth on diamond. More specifically, the effect of four dopants (N, P, B and S) has been studied on the important reaction steps in the growth mechanism of diamond. Substitution of N into the diamond lattice has generally been found to disfavour critical reaction steps in the growth of the 100-face in diamond. This negative effect has been related to electron transfer from the N dopant into an empty surface state, e.g., a surface carbon radical. In addition, strong surface stabilization is observed for N substitution in certain sites via a beta-scission reconstruction, with the formation of sp2 carbon. These observations correlate well with observed surface degradation and decrease in growth rate when a high concentration of nitrogen gas is introduced into the CVD growth process. The effect of co-adsorbed P, S and B onto the diamond surface has also been investigated for two reaction steps: CH3 adsorption and H abstraction. While P and B are observed to influence these reaction steps, the effect of S is rather limited.

The unique features of the Spark plasma sintering (SPS) were used to investigate the sintering and deformation behaviour of titanium and titanium–titanium diboride composites, and to control the sintering and grain growth of ferroelectric Na0.5K0.5NbO3 (NKN) and of hydroxyapatite (HAp). In the SPS the samples experience a temperature different from that recorded by the thermocouple (pyrometer) used and this temperature difference has been estimated for Ti and NKN.   Sintering and deformation of titanium was investigated. Increasing heating rate and/or pressure shifted the sintering to lower temperatures, and the sintering and deformation rates changed when the α→β phase transition temperature was passed. Fully dense Ti/TiB2 composites were prepared. The Ti/TiB2 composites could be deformed at high temperatures, but the hardness decreased due to the formation of TiB.    The kinetic windows within which it is possible to obtain fully dense NKN and HAp ceramics and simultaneously avoid grain growth are defined. Materials have a threshold temperature above which rapid and abnormal grain growth takes place. The abnormal grain growth of NKN is due to a small shift in the stoichiometry, which in turn impairs the ferroelectric properties. Fully transparent HAp nanoceramics was prepared, and between 900 and 1050 oC elongated grains are formed, while above 1050 oC abnormal grain growth takes place.NKN samples containing grains of the sizes 0.35–0.6 µm yielded optimum ferroelectric properties, i.e. a high remanent polarization (Pr = 30 µC/cm2) and high piezoelectric constant (d33= 160 pC/N). The ferroelectric domain structure was studied, and all grains exhibited a multi-domain type of structure. / At the time of doctoral defense the following articles were unpublished and had a status as follows: Article 4: Manuscript; Article 5 : Manuscript

The role of sodium chloride (NaCl) particles and ammonium sulfate ((NH4)2SO4) particles on the initial atmospheric corrosion of copper and zinc was investigated under in situ and ex situ conditions using microgravimetry, FTIR spectroscopy, ion chromatography, scanning electron microscopy with x-ray microanalysis and the scanning Kelvin probe. For the first time, in situ infrared spectra were collected on a micron level during particle induced atmospheric corrosion using a recently developed experimental set-up for in situ FTIR microspectroscopy. Lateral distribution of corrosion and reaction products on copper and zinc surfaces was determined and could be connected with the mechanisms of the initial particle induced corrosion. The recently discovered secondary spreading effect from NaCl electrolyte droplets on metal surfaces was studied under in situ conditions and the effect of CO2 on the spreading process was elaborated. The ambient level of CO2 (350 ppm, 1 ppm = 10-6 volume parts) results in a relatively low secondary spreading effect, whereas the lower level of CO2 (&lt;5 ppm) causes a much faster secondary spreading effect over a large area. At low CO2 concentration alkaline conditions will prevail in the cathodic area, leading to large changes in the surface tension at the oxide/electrolyte interface in the peripherical parts of the droplet. This induces a surface tension driven convective flow of electrolyte from the NaCl droplet. The continuous growth of the secondary spreading area at low CO2 concentration is possible due to the galvanic coupling with the droplet leading to transport of sodium ions to this region and maintenance of the alkaline conditions. At 350 ppm CO2, carbonate formation in the secondary spreading area results in lowering of the pH, increasing the surface tension of the oxide/electrolyte interface and inhibiting the secondary spreading. CO2 strongly affects the NaCl-induced atmospheric corrosion rate of copper. The overall influence of CO2 and NaCl depends on at least three identified mechanisms. At low NaCl particle density, CO2 affects the secondary spreading effect from the electrolyte droplet. This leads to a larger effective cathodic area at low CO2 concentration and a higher corrosion rate. The more alkaline surface electrolyte present at low CO2 concentration also affects the formation of corrosion products and the amount of soluble copper chloride. Whereas the presence of larger amounts of soluble chloride tends to increase the corrosion rate, the formation of CuO results in a more protective surface film which decreases the corrosion rate. This effect was observed at higher NaCl particle densities, where the secondary spreading areas overlapped with adjacent NaCl particle clusters. The formation of CuO leads to lower corrosion rates compared to ambient CO2 concentration in which this phase was not formed. For zinc, the formation of a more protective corrosion product layer was not observed and the corrosion rate is generally higher for low than for ambient CO2 concentration. The presence of NaCl particles on the metal surfaces strongly affects the SO2 interaction with the metal surfaces. The oxidation of S(IV) turned out to be fast at the area of the NaCl-containing electrolyte droplet, both for copper and zinc. On copper surfaces, both sulphate (SO4 2-) and dithionate (S2O6 2-) ions formed which is consistent with a copper catalysed reaction route for sulfite oxidation including the formation of a Cu(II)–sulfito complex as an important step. For zinc, a surface mediated sulfite oxidation process leads to rapid formation of sulphate in the electrolyte droplet area. The presence of SO2 strongly inhibits the secondary spreading due to the decrease in pH induced by absorption of SO2 in the cathodic areas. The presence of gaseous oxidants, such as NO2 and O3, has previously been considered as an important prerequisite for the oxidation of sulfite on copper. The results obtained here suggest that the formation of local electrochemical cells induced by deposited NaCl particles could be another important route for S(IV)- oxidation to sulfate formation. On copper, SO2 was also found to promote the formation of less soluble copper chlorides, such as paratacamite (Cu2(OH)3Cl) and nantokite (CuCl). The electrolyte droplet was dried after 24 hours of exposure due to the formation of less soluble paratacamite (Cu2(OH)3Cl) and nantokite (CuCl) and led to a decrease in the corrosion rate. Thus, SO2 alone promotes the corrosion rate of copper, whereas in the presence of NaCl particles the corrosion rate of copper may slow down due to the formation of insoluble copper chloride compounds. The lateral distribution of corrosion products after exposure of NaCl contaminated copper and zinc surfaces to humid air with gaseous pollutants is a result of the formation of local electrochemical cells at the particles and concomitant differences in chemical composition and pH. For (NH4)2SO4 deposited copper and zinc surfaces the corrosion effects increase with the amount of pre-deposited particles and with the exposure time. On copper, the size of the particles affects the corrosion rate, smaller particles resulting in a higher corrosion rate than larger particles at equal amount of deposition. The formation of Cu2O was the dominant corrosion product after exposure longer than 10 days. (NH4)2SO4 particles result in enhanced Cu2O formation on copper due to a reaction sequence involving catalysis by NH3. The corrosion of copper by (NH4)2SO4 particles was much larger than that induced by NaCl particles. However, for zinc, the (NH4)2SO4 particles lead to smaller corrosion effects than those of NaCl particles. For both particles, significant corrosion attack was observed at relative humidity (RH) lower than the deliquescence point of the salts. / QC 20101001