This thesis explores the possibility of alternatives to copper lining inside the water heater tank in water heaters. The need for an alternative is based on the increasing copper prices the recent years. The aim of this thesis is to compare three different materials, stainless steel, copper and a nickel coated plain carbon steel. This comparison is based on a basic corrosion test and a literature survey to render a merit value for each environment/metal interface. The testing solution consists of 100ppm Cl - concentration the specimens are tested in three different pH levels and at three different temperatures. The specimens have their weight measured before and after the test. The 15μm thick nickel coating was performed by Ferroprodukter AB, composing of 9% P and 91% Ni. The copper and stainless steel specimens are both from Thermia’s actual water heater tank. The copper lining is made of pure copper and the stainless steel hull is made of ferritic stainless steel. The results from the corrosion test are measured in weight change by modulus, |Δw|/w, for the comparison of the three materials. It was found that stainless steel was the worst material, performing better at higher temperatures and higher pH , but overall performance is far from copper and nickel’s corrosion properties. The nickel coating and copper specimen showed comparable results and perform more or less equally well. Regarding identification of corrosion mechanics, it may consist of either pitting and general corrosion damage or a mixture of both. To avoid the fact that weight change may be both negative and positive, the solution to this was to incorporate a merit value based on the absolute value of the weight change, divided by the initial weight of the specimen. In conclusion, stainless steel total weight change by modulus accumulates to 16.072g, nickel coated specimen accumulates a weight change by modulus equal to 8.544g, important note: two of the nickel coated specimen account for ~72.4% of the total weight change by modulus which then accumulates to 2.36g. Copper’s total weight change by modulus was 2.937g thus the lowest. However, disregarding from the 90캜 regime; stainless steel scores 13.496g, copper 2.151g, and nickel 1.095g.

Since the Nobel Prize awarded discovery that some polymers or “plastics” can be made electronically conducting, the scientific field of organic electronics has arisen. The use of conducting polymers in electronic devices is appealing, because the materials can be processed from a liquid phase, much like ordinary non-conducting plastics. This gives the opportunity to utilize printing technologies and manufacture electronics roll-to-roll on flexible substrates, ultimately at very low costs. Even more intriguing are the possibilities to achieve completely novel functionalities in combination with the inherent compatibility of these materials with biological species. Therefore, organic electronics can be merged with biology and medicine to create organic bioelectronics, i.e. organic electronic devices that interact with biological samples directly or are used for biological applications. This thesis aims at giving a background to the field of organic bioelectronics and focuses on how electrochemical devices may be utilized. An organic electronic wettability switch that can be used for lab-on-a-chip applications and control of cell growth as well as an electrochemical ion pump for cell communication and drug delivery are introduced. Furthermore, the underlying electrochemical structures that are the basis for the above mentioned devices, electrochemical display pixels etc. are discussed in detail. In summary, the work contributes to the understanding of electrochemical polymer electronics and, by presenting new bioelectronic inventions, builds a foundation for future projects and discoveries.

<p>Porphyrins consist of twenty-atom rings containing four nitrogen atoms and can be used as sensor to detect odours and gases.</p><p>This thesis investigates whether or not porphyrins can be used as functional materials on grid gate devices.  Drops of PVC embedded porphyrins were deposited on the surface of a grid gate which is a Metal Oxide Semiconductor (MOS) capacitor. In order to detect the gas sensing properties of the porphyrins a light addressable method called Scanning Light Pulse Technique (SLPT) has been used.</p><p>Drops of porphyrins were deposited with a stretched capillary tube (1 mm diameter).</p><p>The MOS capacitor has been exposed to nitrogen atmosphere as reference environment, while the target gases were carbon monoxide (100 ppm) and ammonia (500 ppm).</p><p>The result from the eight porphyrins is that one of them [Pt(II) TPP] has a response for both gases, ammonia induces a change in both the work function and surface resistance, while the carbon monoxide induces only a change in the surface resistance.</p>

<p>The rheological behaviour of cementitious pastes has been studied by various means. Six different cements have been studied in main parts of the work and all of them have been characterized according to the Rietveld method in order to determine the exact content of minerals. Easily soluble alkalis were measured by plasma-emission- spectroscopy of the fluid filtered from paste. Three types of plasticizers namely naphthalene sulfonate formaldehyde condensate (SNF), lignosulphonate and polyacrylate grafted with polyether (PA) have been used throughout the work. The influence of the plasticizer type on the rheological properties of the cementitious pastes, their adsorption characteristics and their effects on heat of hydration of the pastes has been studied. Limestone has been used as a nonreactive model material for cement in some parts of the work. </p><p>All rheological measurements were performed with a parallel plate rheometer. Rather than describing the shear stress-shear rate flow curve with the usual Bingham model resulting in plastic viscosity and yield stress, the area under the curve (Pa/s) was used as a measure of “flow resistance”. </p><p><b>The effect of silica fume and limestone on the rheology of cementitious pastes</b> </p><p>The rheological behaviour of cementitious pastes, with the cement being increasingly replaced by densified and untreated silica fume (SF) or limestone was studied. Three plasticizers were investigated namely two types of polyacrylate (PA1 and PA2) and SNF. PA2 proved to be the most efficient plasticizer of the three while PA1 and SNF provided comparable results. </p><p>The flow resistance was found to increase with increasing silica fume replacement when SNF and polyacryalte (PA1) were added as plasticizers which was explained by ionization of the silica fume surface and possible bridging with polyvalent cations like calcium. The flow resistance decreased, however, with increasing silica fume replacement when the second and more efficient type of polyacrylate (PA2) was utilized which was believed to occur since the cement pastes were better dispersed by PA2 than SNF and PA1. The silica fume particles could thus pack between the cement grains and displace water. An alternative explanation for reduced flow resistance with increasing silica fume replacement could be a ball-bearing effect of silica spheres. </p><p>There was found a trend of <i>increasing</i> gel strength with increasing silica fume replacement of cement even though the pastes seemed to be dispersed by PA2. Cement pastes with densified SF developed lower gel strengths than pastes with untreated SF. This phenomenon was attributed to more grain shaped agglomerates with lower outer surface in densified SF compared to dendritic agglomerated in untreated SF. Decreasing gel strength was found for pastes with increasing limestone filler replacement. Thus silica fume may be advantageous as stabilizing agent for self-compacting concrete preventing segregation upon standing due to a more rapid gel formation. </p><p><b>Effect of cement characteristics on flow resistance</b> </p><p>Rheological experiments were performed on pastes prepared from 4 cements originating from the same clinker, but ground to different finenesses (Blaine). The results showed that the flow resistance increased exponentially with increasing Blaine number. No correlations between single cement characteristics such as Blaine, content of C₃A, cubic C₃A (cC₃A) and C₃S with the flow resistance were however found when cements from different clinkers were used. This finding indicates that cement should not be treated as a univariable material. However, the combined cement characteristic (Blaine•{d•cC₃A+[1-d]•C₃S}) was found to correlate with flow resistance, where the factor d represents relative reactivity of C₃A and C₃S. The flow resistance was found to be either a linear or exponential function of the combined cement characteristic depending on plasticizer type and dosage. Correlations were found for a mix of pure cement and cement with fly ash, limestone filler (4%), as well as pastes with constant silica fume dosage when the minerals were determined by XRD. </p><p><b>Influence of cement and plasticizer type on the heat of hydration</b> </p><p>The initial heat of hydration peak was measured for the 6 main cements with 0.32% SNF, lignosulphonate and PA2 by cement weight. Correlations were attempted between the maximum heat of hydration rates of the initial peaks with various cement characteristics. The maximum heat of hydration rate seemed to correlate with the product of the cement fineness and C₃A content regardless of plasticizer type. The fly ash cement had to be left out of the correlation plots due to its low initial heat of hydration. </p><p>The second, third and fourth hydration peaks were measured on the cement pastes with 0-0.8% SNF, lignosulphonate and PA2 by weight of cement. Lignosulphonate was found to be the strongest retarder while SNF had the least effect on the setting time of the three plasticizers. No correlations could be found between the setting times and cement characteristics such as cement fineness, aluminate and alkali contents for un-plasticized pastes probably because the setting times might have been too close to each other to be able to obtain accurate values. Correlations between setting time and cement characteristics were however found for pastes with plasticizers. The setting times did not correlate with the cement fineness (Blaine) as a single parameter. The product of cement Blaine and C₃A content, however, resulted in a correlation. Furthermore the setting time correlated with the cubic modification of C₃A. It may seem that the setting times depend more on the cubic modification of C₃A than the sum of orthorhombic and cubic aluminate. This finding indicates that the cubic aluminate modification is more reactive than the orthorhombic. The setting time decreased with increasing content of easily soluble K-ions in the cements probably due to the formation of syngenite, K₂SO₄·CaSO₄·H₂O, which removes some sulphate from solution that would otherwise retard C₃A hydration. A similar correlation was not found between the setting time and the sodium equivalent.</p><p><b>Cement interactions with plasticizers </b></p><p>Three plasticizers were studied namely SNF, lignosulphonate and polyacrylate (PA2). PA2 was the most efficient plasticizer of the three tested even thought it was found to adsorb to a lesser extent on cement than SNF and lignosulphonate. SNF and lignosulphonate brought about comparable results. </p><p>PA2 was observed to induce flow gain within the 2 hours of rheological measurements which might be caused by the polymer expanding in the water phase and thus improve the dispersion of the paste. Furthermore the grafted side chains of the polymer are considered to be long enough to provide steric dispersion even thought the backbone might be embedded in the hydration products. Cement pastes with SNF and lignosulphonate exhibited flow loss as a function of time which indicates that the plasticizer molecules were consumed by the hydration products. </p><p>The concentrations of superplasticizer in the pore water were not found to change markedly in the time range 20-95 min after water addition, indicating that most of the plasticizer molecules were consumed (i.e. adsorbed or intercalated in surface hydration products) within the first 20 minutes after water addition. </p><p>The adsorption characteristics were found to depend on the plasticizer type. The adsorption curves of SNF and lignosulphonate reached a plateau at saturation characterizing high-affinity adsorption or increased continuously as a sign of low affinity adsorption. The adsorbed amounts of polyacrylate decreased, however, after saturation had been reached which might indicate that surplus molecules in the water phase compress the ionic double layer or that adsorbed molecules expand and hinder molecules in the water phase to attach at the surface (i.e. osmosis). </p><p>The plasticizer saturation dosages were found to depend on cement surface area (Blaine), amount of cubic C₃A and easily soluble sulphates. The saturation dosage of lignosulphonate seemed to have a dependency on the amount of soluble alkali that was somewhat stronger than observed for pastes with SNF. This difference might be caused by lignosulphonate forming complexes with solvated ions in a higher degree than SNF. Moreover alkali sulphates are furthermore often added to commercial SNF based products as the one used in this work. The best correlation, overall, was found for the product of cubic C₃A and Blaine which is logical since high surface and cubic aluminate contents accounts for high cement reactivity and since the plasticizers are known to coordinate with calcium sites. Correlations were also found between saturation dosage with the product of Na_eqvand Blaine as well as the product of Na_eqv and cubic C₃A. The investigations seemed to indicate that the plasticizer saturation concentration increase with increasing alkali content. These findings, however, are rather unclear. According to literature an increased concentration of alkali sulphate in solution results in both an increased hydration rate (which would lead to a higher plasticizer intercalation) and a reduced plasticizer adsorption (due to SO₄^2- - superplasticizer competition). The easily soluble sulphates might, of course, entail the opposing effects of Blaine and C₃A in a way that smoothen the correlation plots of the plasticizer saturation dosage with the cement characteristics.</p><p><b>Effect of temperature on rheology and plasticizer adsorption</b> </p><p>Flow resistance and adsorbed amounts of SNF, lignosulphonate and PA2 were measured at temperatures ranging from 11 to 40^oC. Limestone was used as a nonreactive model material for cement. The adsorbed amounts of SNF and lignosulphonate on limestone were found to decrease after reaching a maximum which occurred at approximately 25^oC. Decreased amounts of adsorbed plasticizer with increasing temperature might be explained by increased kinetic energy to the molecules or by an entropy effect. The adsorption of PA2 on limestone seemed to be independent of paste temperature in the range of 16-34^oC which might be caused by low reduction of entropy at adsorption due to its short backbone and long, grafted side chains. The flow resistance of the limestone pastes generally increased with increasing temperature which may be caused by reduced amounts of adsorbed plasticizer and/or dehydration of the paste during the rheological measurements. </p><p>Two types of cements were used to study adsorption and flow resistance with increasing temperature namely CEM I 42.5 RR and CEM I 52.5 R-LA. Amounts of plasticizer adsorbed and intercalated (consumed) by cement reached a plateau or even decreased with increasing temperature in the case of SNF and lignosulphonate. This finding might be caused by two opposing effects namely: increased number of adsorption sites due to increased hydration rate with increasing temperature and reduced adsorption due to increased kinetic energy and/or reduced entropy of the plasticizer. Amounts of PA2 consumed by cement increased linearly with increasing temperature as might be explained by the experiments with limestone where the adsorbed amounts of PA2 seemed to be independent of temperature. Increased consumption of plasticizer by the cements with rising temperature is thus probably governed by the increased number of adsorption cites due to increased hydration rate. The flow resistance of CEM I 52.5 R-LA cement increased exponentially with increasing temperature as a function of temperature most likely because of the increased hydration rate. The pastes of CEM I 42.5 RR cement were generally highly viscous and probably agglomerated. The flow resistance reached a plateau value with increasing temperature in this case.</p>

<p>Perovskites and perovskite related materials are materials that are candidates for applications such as oxygen permeable membranes, cathodes for SOFC and high-temperature oxygen sensors. This arises from the potential high ionic conductivity and the chemical stability even at low partial pressures of oxygen. From an application point of view, it is important to have knowledge about the oxygen transport properties in these materials. Oxygen transport in mixed conducting oxides involves two inherently different processes; oxygen exchange between bulk gas and surface and solid state diffusion. The objective of this work has been to obtain fundamental understanding of these transport properties in mixed ionic and electronic conductors. For that purpose two materials systems with significant differences in electronic conductivty and oxygen vacancy concentration were chosen as objectives for the investigation, viz.: Sr-substituted LaCoO₃ and Al-substituted SrTiO₃.</p><p>All transport properties (diffusion and surface exchange) have been assessed by electrical conductivity relaxation, and the work also evaluate the pros and cons using this specific method to obtain transport data for the materials in question.</p><p>In the first two papers (Paper 1 and Paper 2) transport properties are derived for La_1-xSr_xCoO_3-δ (x=0 (LC), 0.2 (LSC-02) and 0.5 (LSC-05)). In Paper 1 “chemical transport coefficients”, D_chem and k_chem, are reported. More fundamental transport coefficients, such as oxygen component diffusion coefficient (D_O) and vacancy diffusion coefficients (D_V), are also deduced and discussed. Activation energies for D_O and D_V, were determined. The activation energies for D_O varies from 279 kJ/mol for LC to 174-222 kJ/mol for LSC-02 and 90-105 kJ/mol for LSC-05, decreasing with increasing Srcontent. The activation energies for the vacancy diffusion coefficient, DV, are smaller than for the component diffusion coefficients and typical values are 77 kJ/mol for LC, 85 kJ/mol for LSC-02 and 75 kJ/mol for LSC-05, that is, almost independent of Sr-content. The enthalpies of vacancy formation decreases with increasing Sr content. The values are 206 kJ/mol for LC, 75 kJ/mol for LSC-02 and 15 kJ/mol for LSC-05, which agrees well with values reported in the literature. However, the vacancy diffusion coefficient showed an unexpected increase at high concentrations of oxygen vacancies, corresponding to δ=0.27-0.30. The phenomena with a PO₂ dependent D_V is discussed.</p><p>In Paper 2, the oxygen surface exchange coefficient, k₀, is derived from “chemical values” reported in Paper 1, and used as a basis to deduce probable reaction mechanisms associated with surface exchange. The temperature dependency plots showed that for the composition with x = 0.5, the k0 made a shift in activation energy from ~120 kJ/mol to ~15 kJ/mol above 950 °C. It is suggested that this significant shift in activation energy might be due to an oxygen adsorption/desorption mechanism on the surface becoming rate controlling at high temperatures. The composition with x=0.2 did not show this shift in activation energy. Relations between possible rate controlling reactions and reaction rates (k₀) were established, and formed the basis for discussions on probable rate controlling processes. There are reasons to assume that for oxidation prosesses a rate controlling reaction involving a direct “installation” of an oxygen molecule into two vacancies is dominating, while a dissociation of an oxygen molecule generally gives a better description for a reduction process.</p><p>In Paper 3 the oxygen transport properties in SrTi_1-xAl_xO₃ (x=0 (ST), 0.02 (STA-02) and 0.05 (STA-05)) were determined in O2/N2 mixtures. In this contribution the electrical conductivity is also presented in a large P_O2- interval (O₂/N₂- and CO/CO₂-mixtures). Electrical conductivity for pure SrTiO₃ (ST) in terms of P_O2 applied well with defect chemistry reported in the literature. For the two Al-substituted compositions the electrical conductivity followed predicted behaviour at high and low P_O2’s. However, in the medium P_O2 range we were not able to describe the conductivity behaviour in terms of classical defect chemistry. Reasons for the discrepancy is discussed.</p><p>D_chem for ST and STA-02 are reported and are, along with their corresponding activation energies, 187 and 104-180 kJ/mol, respectively, in good accordance with values from literature. Furthermore, values for the component diffusion coefficient, D_O, and the vacancy diffusion coefficient, D_V, are reported for ST at 950 °C, the only composition where oxygen vacancy concentrations are available in the literature. Values for kchem in STA-02 and STA-05 are also reported, and show pronounced P_O2 dependencies. For STA-05 the activation energy for k_chem is found to vary between 90 and 105 kJ/mol. Due to a high uncertainty, activation energies are not reported for STA-02.</p><p>Reported D_chem and k_chem values for related materials in literature indicate increasing numeric values with decreasing concentration of oxygen vacancies. It is reasoned that this is due to an ever increasing thermodynamic factor with decreasing population of vacancies. The implications for the component diffusion coefficient is discussed.</p><p>In Paper 4 the oxygen transport properties in SrTiO₃ pure and with Al were investigated in mixtures of CO/CO₂. D_chem are reported for ST and STA-02 while k_chem are reported for ST, STA-02 and STA-05. The D_chem showed a P_O2-dependency, which can be explained by the variation in the thermodynamic factor. The introduction of Al in the sample increases the value of D_chem, probably due to the introduction of more oxygen vacancies. STA-02 showed a discrete increase in D_chem in the CO-rich atmospheres, this may be due to phase transition or phase separation at P_O2~10^-17 atm. The k_chemshowed a maximum at P_CO/P_CO2 = 1 for STA-02 and STA-05. This behaviour corresponds well with a rate controlling reaction involving a charged and adsorbed CO₂ molecule. The same maximum is also reported in the literature for BaTiO₃ wihtout and with 1.8 % Al and for La_0.9Sr_0.1FeO₃.</p><p>This work has examined chemical diffusion and surface exchange coefficients with electrical conductivity relaxation in two material systems with distinct differences in electrical conductivity and oxygen vacancy concentrations. The main focus has been to elucidate properties of the transport coefficients based on own measurements, but also include transport coefficients from other material systems from literature as references. The vacancy diffusion coefficients have been examined, showing that they increase with increasing concentration of oxygen vacancies in materials where the concentration of vacancies is high. No obvious reason for this behaviour has been found, however, it may be related to a change in activation energy. It is rather well established in the literature that for materials where the concentration of vacancies may be characterized as dilute, we should expect a D_V independent of the population of vacancies. Finally, based on own results and data reported in the literature it appears that with respect to the oxygen surface flux the oxygen vacancy concentration seems to be the property of most importance. That is, for oxidation processes the oxygen exchange flux will increase with vacancy population.</p>

<p><p>This thesis explores the possibility of alternatives to copper lining inside the water heater</p><p>tank in water heaters. The need for an alternative is based on the increasing copper prices the</p><p>recent years. The aim of this thesis is to compare three different materials, stainless steel,</p><p>copper and a nickel coated plain carbon steel. This comparison is based on a basic corrosion</p><p>test and a literature survey to render a merit value for each environment/metal interface. The</p><p>testing solution consists of 100ppm Cl</p><p>- concentration the specimens are tested in three<p>different pH levels and at three different temperatures. The specimens have their weight</p><p>measured before and after the test.</p><p>The 15μm thick nickel coating was performed by Ferroprodukter AB, composing of 9% P</p><p>and 91% Ni. The copper and stainless steel specimens are both from Thermia’s actual water</p><p>heater tank. The copper lining is made of pure copper and the stainless steel hull is made of</p><p>ferritic stainless steel.</p><p>The results from the corrosion test are measured in weight change by modulus, |Δw|/w, for</p><p>the comparison of the three materials. It was found that stainless steel was the worst</p><p>material, performing better at higher temperatures and higher pH , but overall performance is</p><p>far from copper and nickel’s corrosion properties. The nickel coating and copper specimen</p><p>showed comparable results and perform more or less equally well. Regarding identification</p><p>of corrosion mechanics, it may consist of either pitting and general corrosion damage or a</p><p>mixture of both. To avoid the fact that weight change may be both negative and positive, the</p><p>solution to this was to incorporate a merit value based on the absolute value of the weight</p><p>change, divided by the initial weight of the specimen.</p><p>In conclusion, stainless steel total weight change by modulus accumulates to 16.072g, nickel</p><p>coated specimen accumulates a weight change by modulus equal to 8.544g, important note:</p><p>two of the nickel coated specimen account for ~72.4% of the total weight change by modulus</p><p>which then accumulates to 2.36g. Copper’s total weight change by modulus was 2.937g thus</p><p>the lowest. However, disregarding from the 90캜 regime; stainless steel scores 13.496g,</p><p>copper 2.151g, and nickel 1.095g.</p></p></p>

The rheological behaviour of cementitious pastes has been studied by various means. Six different cements have been studied in main parts of the work and all of them have been characterized according to the Rietveld method in order to determine the exact content of minerals. Easily soluble alkalis were measured by plasma-emission- spectroscopy of the fluid filtered from paste. Three types of plasticizers namely naphthalene sulfonate formaldehyde condensate (SNF), lignosulphonate and polyacrylate grafted with polyether (PA) have been used throughout the work. The influence of the plasticizer type on the rheological properties of the cementitious pastes, their adsorption characteristics and their effects on heat of hydration of the pastes has been studied. Limestone has been used as a nonreactive model material for cement in some parts of the work. All rheological measurements were performed with a parallel plate rheometer. Rather than describing the shear stress-shear rate flow curve with the usual Bingham model resulting in plastic viscosity and yield stress, the area under the curve (Pa/s) was used as a measure of “flow resistance”. <b>The effect of silica fume and limestone on the rheology of cementitious pastes</b> The rheological behaviour of cementitious pastes, with the cement being increasingly replaced by densified and untreated silica fume (SF) or limestone was studied. Three plasticizers were investigated namely two types of polyacrylate (PA1 and PA2) and SNF. PA2 proved to be the most efficient plasticizer of the three while PA1 and SNF provided comparable results. The flow resistance was found to increase with increasing silica fume replacement when SNF and polyacryalte (PA1) were added as plasticizers which was explained by ionization of the silica fume surface and possible bridging with polyvalent cations like calcium. The flow resistance decreased, however, with increasing silica fume replacement when the second and more efficient type of polyacrylate (PA2) was utilized which was believed to occur since the cement pastes were better dispersed by PA2 than SNF and PA1. The silica fume particles could thus pack between the cement grains and displace water. An alternative explanation for reduced flow resistance with increasing silica fume replacement could be a ball-bearing effect of silica spheres. There was found a trend of increasing gel strength with increasing silica fume replacement of cement even though the pastes seemed to be dispersed by PA2. Cement pastes with densified SF developed lower gel strengths than pastes with untreated SF. This phenomenon was attributed to more grain shaped agglomerates with lower outer surface in densified SF compared to dendritic agglomerated in untreated SF. Decreasing gel strength was found for pastes with increasing limestone filler replacement. Thus silica fume may be advantageous as stabilizing agent for self-compacting concrete preventing segregation upon standing due to a more rapid gel formation. <b>Effect of cement characteristics on flow resistance</b> Rheological experiments were performed on pastes prepared from 4 cements originating from the same clinker, but ground to different finenesses (Blaine). The results showed that the flow resistance increased exponentially with increasing Blaine number. No correlations between single cement characteristics such as Blaine, content of C3A, cubic C3A (cC3A) and C3S with the flow resistance were however found when cements from different clinkers were used. This finding indicates that cement should not be treated as a univariable material. However, the combined cement characteristic (Blaine•{d•cC3A+[1-d]•C3S}) was found to correlate with flow resistance, where the factor d represents relative reactivity of C3A and C3S. The flow resistance was found to be either a linear or exponential function of the combined cement characteristic depending on plasticizer type and dosage. Correlations were found for a mix of pure cement and cement with fly ash, limestone filler (4%), as well as pastes with constant silica fume dosage when the minerals were determined by XRD. <b>Influence of cement and plasticizer type on the heat of hydration</b> The initial heat of hydration peak was measured for the 6 main cements with 0.32% SNF, lignosulphonate and PA2 by cement weight. Correlations were attempted between the maximum heat of hydration rates of the initial peaks with various cement characteristics. The maximum heat of hydration rate seemed to correlate with the product of the cement fineness and C3A content regardless of plasticizer type. The fly ash cement had to be left out of the correlation plots due to its low initial heat of hydration. The second, third and fourth hydration peaks were measured on the cement pastes with 0-0.8% SNF, lignosulphonate and PA2 by weight of cement. Lignosulphonate was found to be the strongest retarder while SNF had the least effect on the setting time of the three plasticizers. No correlations could be found between the setting times and cement characteristics such as cement fineness, aluminate and alkali contents for un-plasticized pastes probably because the setting times might have been too close to each other to be able to obtain accurate values. Correlations between setting time and cement characteristics were however found for pastes with plasticizers. The setting times did not correlate with the cement fineness (Blaine) as a single parameter. The product of cement Blaine and C3A content, however, resulted in a correlation. Furthermore the setting time correlated with the cubic modification of C3A. It may seem that the setting times depend more on the cubic modification of C3A than the sum of orthorhombic and cubic aluminate. This finding indicates that the cubic aluminate modification is more reactive than the orthorhombic. The setting time decreased with increasing content of easily soluble K-ions in the cements probably due to the formation of syngenite, K2SO4·CaSO4·H2O, which removes some sulphate from solution that would otherwise retard C3A hydration. A similar correlation was not found between the setting time and the sodium equivalent. <b>Cement interactions with plasticizers </b> Three plasticizers were studied namely SNF, lignosulphonate and polyacrylate (PA2). PA2 was the most efficient plasticizer of the three tested even thought it was found to adsorb to a lesser extent on cement than SNF and lignosulphonate. SNF and lignosulphonate brought about comparable results. PA2 was observed to induce flow gain within the 2 hours of rheological measurements which might be caused by the polymer expanding in the water phase and thus improve the dispersion of the paste. Furthermore the grafted side chains of the polymer are considered to be long enough to provide steric dispersion even thought the backbone might be embedded in the hydration products. Cement pastes with SNF and lignosulphonate exhibited flow loss as a function of time which indicates that the plasticizer molecules were consumed by the hydration products. The concentrations of superplasticizer in the pore water were not found to change markedly in the time range 20-95 min after water addition, indicating that most of the plasticizer molecules were consumed (i.e. adsorbed or intercalated in surface hydration products) within the first 20 minutes after water addition. The adsorption characteristics were found to depend on the plasticizer type. The adsorption curves of SNF and lignosulphonate reached a plateau at saturation characterizing high-affinity adsorption or increased continuously as a sign of low affinity adsorption. The adsorbed amounts of polyacrylate decreased, however, after saturation had been reached which might indicate that surplus molecules in the water phase compress the ionic double layer or that adsorbed molecules expand and hinder molecules in the water phase to attach at the surface (i.e. osmosis). The plasticizer saturation dosages were found to depend on cement surface area (Blaine), amount of cubic C3A and easily soluble sulphates. The saturation dosage of lignosulphonate seemed to have a dependency on the amount of soluble alkali that was somewhat stronger than observed for pastes with SNF. This difference might be caused by lignosulphonate forming complexes with solvated ions in a higher degree than SNF. Moreover alkali sulphates are furthermore often added to commercial SNF based products as the one used in this work. The best correlation, overall, was found for the product of cubic C3A and Blaine which is logical since high surface and cubic aluminate contents accounts for high cement reactivity and since the plasticizers are known to coordinate with calcium sites. Correlations were also found between saturation dosage with the product of Naeqv and Blaine as well as the product of Naeqv and cubic C3A. The investigations seemed to indicate that the plasticizer saturation concentration increase with increasing alkali content. These findings, however, are rather unclear. According to literature an increased concentration of alkali sulphate in solution results in both an increased hydration rate (which would lead to a higher plasticizer intercalation) and a reduced plasticizer adsorption (due to SO42- - superplasticizer competition). The easily soluble sulphates might, of course, entail the opposing effects of Blaine and C3A in a way that smoothen the correlation plots of the plasticizer saturation dosage with the cement characteristics. <b>Effect of temperature on rheology and plasticizer adsorption</b> Flow resistance and adsorbed amounts of SNF, lignosulphonate and PA2 were measured at temperatures ranging from 11 to 40oC. Limestone was used as a nonreactive model material for cement. The adsorbed amounts of SNF and lignosulphonate on limestone were found to decrease after reaching a maximum which occurred at approximately 25oC. Decreased amounts of adsorbed plasticizer with increasing temperature might be explained by increased kinetic energy to the molecules or by an entropy effect. The adsorption of PA2 on limestone seemed to be independent of paste temperature in the range of 16-34oC which might be caused by low reduction of entropy at adsorption due to its short backbone and long, grafted side chains. The flow resistance of the limestone pastes generally increased with increasing temperature which may be caused by reduced amounts of adsorbed plasticizer and/or dehydration of the paste during the rheological measurements. Two types of cements were used to study adsorption and flow resistance with increasing temperature namely CEM I 42.5 RR and CEM I 52.5 R-LA. Amounts of plasticizer adsorbed and intercalated (consumed) by cement reached a plateau or even decreased with increasing temperature in the case of SNF and lignosulphonate. This finding might be caused by two opposing effects namely: increased number of adsorption sites due to increased hydration rate with increasing temperature and reduced adsorption due to increased kinetic energy and/or reduced entropy of the plasticizer. Amounts of PA2 consumed by cement increased linearly with increasing temperature as might be explained by the experiments with limestone where the adsorbed amounts of PA2 seemed to be independent of temperature. Increased consumption of plasticizer by the cements with rising temperature is thus probably governed by the increased number of adsorption cites due to increased hydration rate. The flow resistance of CEM I 52.5 R-LA cement increased exponentially with increasing temperature as a function of temperature most likely because of the increased hydration rate. The pastes of CEM I 42.5 RR cement were generally highly viscous and probably agglomerated. The flow resistance reached a plateau value with increasing temperature in this case.

Perovskites and perovskite related materials are materials that are candidates for applications such as oxygen permeable membranes, cathodes for SOFC and high-temperature oxygen sensors. This arises from the potential high ionic conductivity and the chemical stability even at low partial pressures of oxygen. From an application point of view, it is important to have knowledge about the oxygen transport properties in these materials. Oxygen transport in mixed conducting oxides involves two inherently different processes; oxygen exchange between bulk gas and surface and solid state diffusion. The objective of this work has been to obtain fundamental understanding of these transport properties in mixed ionic and electronic conductors. For that purpose two materials systems with significant differences in electronic conductivty and oxygen vacancy concentration were chosen as objectives for the investigation, viz.: Sr-substituted LaCoO3 and Al-substituted SrTiO3. All transport properties (diffusion and surface exchange) have been assessed by electrical conductivity relaxation, and the work also evaluate the pros and cons using this specific method to obtain transport data for the materials in question. In the first two papers (Paper 1 and Paper 2) transport properties are derived for La1-xSrxCoO3-δ (x=0 (LC), 0.2 (LSC-02) and 0.5 (LSC-05)). In Paper 1 “chemical transport coefficients”, Dchem and kchem, are reported. More fundamental transport coefficients, such as oxygen component diffusion coefficient (DO) and vacancy diffusion coefficients (DV), are also deduced and discussed. Activation energies for DO and DV, were determined. The activation energies for DO varies from 279 kJ/mol for LC to 174-222 kJ/mol for LSC-02 and 90-105 kJ/mol for LSC-05, decreasing with increasing Srcontent. The activation energies for the vacancy diffusion coefficient, DV, are smaller than for the component diffusion coefficients and typical values are 77 kJ/mol for LC, 85 kJ/mol for LSC-02 and 75 kJ/mol for LSC-05, that is, almost independent of Sr-content. The enthalpies of vacancy formation decreases with increasing Sr content. The values are 206 kJ/mol for LC, 75 kJ/mol for LSC-02 and 15 kJ/mol for LSC-05, which agrees well with values reported in the literature. However, the vacancy diffusion coefficient showed an unexpected increase at high concentrations of oxygen vacancies, corresponding to δ=0.27-0.30. The phenomena with a PO2 dependent DV is discussed. In Paper 2, the oxygen surface exchange coefficient, k0, is derived from “chemical values” reported in Paper 1, and used as a basis to deduce probable reaction mechanisms associated with surface exchange. The temperature dependency plots showed that for the composition with x = 0.5, the k0 made a shift in activation energy from ~120 kJ/mol to ~15 kJ/mol above 950 °C. It is suggested that this significant shift in activation energy might be due to an oxygen adsorption/desorption mechanism on the surface becoming rate controlling at high temperatures. The composition with x=0.2 did not show this shift in activation energy. Relations between possible rate controlling reactions and reaction rates (k0) were established, and formed the basis for discussions on probable rate controlling processes. There are reasons to assume that for oxidation prosesses a rate controlling reaction involving a direct “installation” of an oxygen molecule into two vacancies is dominating, while a dissociation of an oxygen molecule generally gives a better description for a reduction process. In Paper 3 the oxygen transport properties in SrTi1-xAlxO3 (x=0 (ST), 0.02 (STA-02) and 0.05 (STA-05)) were determined in O2/N2 mixtures. In this contribution the electrical conductivity is also presented in a large PO2- interval (O2/N2- and CO/CO2-mixtures). Electrical conductivity for pure SrTiO3 (ST) in terms of PO2 applied well with defect chemistry reported in the literature. For the two Al-substituted compositions the electrical conductivity followed predicted behaviour at high and low PO2’s. However, in the medium PO2 range we were not able to describe the conductivity behaviour in terms of classical defect chemistry. Reasons for the discrepancy is discussed. Dchem for ST and STA-02 are reported and are, along with their corresponding activation energies, 187 and 104-180 kJ/mol, respectively, in good accordance with values from literature. Furthermore, values for the component diffusion coefficient, DO, and the vacancy diffusion coefficient, DV, are reported for ST at 950 °C, the only composition where oxygen vacancy concentrations are available in the literature. Values for kchem in STA-02 and STA-05 are also reported, and show pronounced PO2 dependencies. For STA-05 the activation energy for kchem is found to vary between 90 and 105 kJ/mol. Due to a high uncertainty, activation energies are not reported for STA-02. Reported Dchem and kchem values for related materials in literature indicate increasing numeric values with decreasing concentration of oxygen vacancies. It is reasoned that this is due to an ever increasing thermodynamic factor with decreasing population of vacancies. The implications for the component diffusion coefficient is discussed. In Paper 4 the oxygen transport properties in SrTiO3 pure and with Al were investigated in mixtures of CO/CO2. Dchem are reported for ST and STA-02 while kchem are reported for ST, STA-02 and STA-05. The Dchem showed a PO2-dependency, which can be explained by the variation in the thermodynamic factor. The introduction of Al in the sample increases the value of Dchem, probably due to the introduction of more oxygen vacancies. STA-02 showed a discrete increase in Dchem in the CO-rich atmospheres, this may be due to phase transition or phase separation at PO2 ~10-17 atm. The kchem showed a maximum at PCO/PCO2 = 1 for STA-02 and STA-05. This behaviour corresponds well with a rate controlling reaction involving a charged and adsorbed CO2 molecule. The same maximum is also reported in the literature for BaTiO3 wihtout and with 1.8 % Al and for La0.9Sr0.1FeO3. This work has examined chemical diffusion and surface exchange coefficients with electrical conductivity relaxation in two material systems with distinct differences in electrical conductivity and oxygen vacancy concentrations. The main focus has been to elucidate properties of the transport coefficients based on own measurements, but also include transport coefficients from other material systems from literature as references. The vacancy diffusion coefficients have been examined, showing that they increase with increasing concentration of oxygen vacancies in materials where the concentration of vacancies is high. No obvious reason for this behaviour has been found, however, it may be related to a change in activation energy. It is rather well established in the literature that for materials where the concentration of vacancies may be characterized as dilute, we should expect a DV independent of the population of vacancies. Finally, based on own results and data reported in the literature it appears that with respect to the oxygen surface flux the oxygen vacancy concentration seems to be the property of most importance. That is, for oxidation processes the oxygen exchange flux will increase with vacancy population.

Porphyrins consist of twenty-atom rings containing four nitrogen atoms and can be used as sensor to detect odours and gases. This thesis investigates whether or not porphyrins can be used as functional materials on grid gate devices.  Drops of PVC embedded porphyrins were deposited on the surface of a grid gate which is a Metal Oxide Semiconductor (MOS) capacitor. In order to detect the gas sensing properties of the porphyrins a light addressable method called Scanning Light Pulse Technique (SLPT) has been used. Drops of porphyrins were deposited with a stretched capillary tube (1 mm diameter). The MOS capacitor has been exposed to nitrogen atmosphere as reference environment, while the target gases were carbon monoxide (100 ppm) and ammonia (500 ppm). The result from the eight porphyrins is that one of them [Pt(II) TPP] has a response for both gases, ammonia induces a change in both the work function and surface resistance, while the carbon monoxide induces only a change in the surface resistance.

Stainless steels often exhibit complex transformation and precipitation behaviour due to a high content of alloying elements. Secondary phases can be formed in the temperature range of 300-1000°C and are generally undesirable due to their detrimental effect on mechanical properties and corrosion resistance of stainless steels. Of all precipitate types, sigma phase is the major concern due to its effect on both toughness and resistance to corrosion. However, the effect of the phase itself cannot be separated from that of associated changes in the surrounding matrix if macroscopic techniques are used. The situation is similar for investigations of chromium nitrides, which are the precipitated phases frequently observed in high nitrogen stainless steels. High resolution techniques are required to characterize such small individual precipitates to be able to examine their actual effect on the corrosion resistance of stainless steels.   In this work, magnetic force microscopy (MFM) and scanning Kelvin probe force microscopy (SKPFM) were used to investigate the magnetic properties and the Volta potential difference of precipitated phases. The magnetic domain distribution was used to distinguish between ferrite (ferromagnetic), austenite (paramagnetic), and sigma phase (non-magnetic). The Volta potential differences reflect the relative nobility of the phases and thus their tendency to corrode. The MFM and SKPFM techniques are shown to achieve a high lateral resolution of at least 100 nm. This means that small particles or precipitated phases can be characterized separately from the surrounding matrix.   Two grades of duplex stainless steels, the standard 2205 and the super duplex 2507, and an electroslag strip weld with a multi-phase microstructure were investigated using a combination of local probing techniques. The duplex stainless steels underwent various heat treatments to precipitate a sufficient amount of secondary phases. Scanning electron microscopy in backscattered electron mode and energy dispersive X-ray spectroscopy yielded information on the phase distribution and chemical composition of individual phases. Detailed marking of the surfaces was used so that exactly the same areas could be investigated with the MFM and SKPFM techniques. Transmission electron microscopy (TEM) was also employed to characterize the chemical composition of depleted phase boundaries.     The general observation is that, austenite exhibited a higher Volta potential compared with ferrite, most likely due to a higher nickel content in the austenite phase. When sigma phase was present, it showed an intermediate Volta potential between the austenite and ferrite phases. This indicates that austenite is, in general, more noble than sigma phase, and that ferrite is the most active phase. However, austenite showed a lower Volta potential than sigma phase when a long-term isothermal heat treatment at 800°C was used. This is attributed to the depletion of alloying elements in the austenite phase as a result of the formation of chromium nitrides and sigma phase. Synergistic interactions between chromium, molybdenum, and nitrogen may contribute to the effect on the Volta potential, since such small changes of these elements result in reversed Volta potentials of the austenite and sigma phase.   Results from SKPFM and TEM analyses are in concordance and indicate local drops in Volta potential at the phase boundaries due to the depletion of alloying elements caused by sigma phase formation. Immersion tests in acidic mixtures also confirmed that these depleted regions are more susceptible to selective corrosion.   Precipitated chromium nitrides showed a higher Volta potential compared with the other phases. This indicates that any deterioration in the corrosion resistance is unlikely caused by the nitride particles themselves, but rather by the alloying element depleted regions surrounding the nitride particles. The size of nitride particles affected the measured Volta potential, and the measured Volta potentials of small particles are tended to be concealed by the surrounding matrix. When the size of nitride particles is below the resolution limit of the SKPFM technique, the Volta potential differences of these particles relative to the matrix could not be detected.   Volta potential measured in air with the SKPFM technique correlated better to the tendency to active dissolution than to pitting corrosion in acidic mixtures. The magnetic force showed a certain influence on the electrostatic force, thus Volta potential measurements are recommended to be performed with a non-magnetic tip. Although many factors may affect the measured Volta potential, the SKFPM technique combined with other local probing techniques is a promising approach to evaluate corrosion tendency of precipitated phases in multi-phase alloys. With optimal conditions, the detectable size was down to approximately 100 nm. / QC 20100518