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By utilizing previously established catalytic model reactions, a method for probing the topological location of transition metal sites incorporated in hierarchical silicoaluminophosphates (SAPOs) is presented. For the first time, iron(III)-incorporated hierarchical SAPO-11 (FeCTAB-11) was prepared and thoroughly characterized with conventional iron(III)-incorporated SAPO-11 (FeSAPO-11) as a reference. Initially, inductively coupled plasma - mass spectrometry (ICP-MS) indicated that the FeSAPOs contained similar amounts of metal (∼2.0 wt%), while N

Manganese cobalt spinel oxides are promising coating materials for the protection of ferritic stainless steel interconnects in solid oxide fuel cell (SOFC) stacks. The interaction between such coatings and the steel is here studied using diffusion couples as a model system. The interaction between MnCo2O4, MnCo1.7Fe0.3O4 and MnCo1.7Cu0.3O4 spinels and Cr2O3 was studied in air at 900 °C. In allcases, a reaction layer rich in Co and Cr formed at the interfaces. Using Pt-particles to mark the original interface reveals that the reaction layers grow by diffusion of Co (and Mn) from the spinel oxides to the Cr2O3/reaction layer interface. The growth of the reaction layers followed parabolic kinetics with rate constants of 1.3×10−5 μm2 s−1 for the MnCo2O4/Cr2O3 couple, 8.6×10−6 μm2 s−1 for the MnCo1.7Fe0.3O4/Cr2O3 couple, and finally 1.2×10−4 μm2 s−1 for the MnCo1.7Cu0.3O4/Cr2O3 couple.

First-year university students’ knowledge and conceptual understanding of general chemistry has been investigated using a multiple-choice concept inventory (Chemical Concept Inventory 3.0/CCI 3.0) as a pre-test (n = 221) and a post-test (n = 90) in two first-semester chemistry courses. This paper discusses the students’ answers to two questions about bond energy. Student interviews (n = 7) were performed for further insight in the students’ thought processes and validation of the CCI questions. Although many students appeared to recall that breaking a chemical bond demands energy, most were not able to use this fact to reason about the heat released in a chemical reaction, and the alternative conception that bond breaking releases energy seemed deeply ingrained and prevalent among the students. For one of the questions, more students gave the correct answer on the pre-test than on the post-test. Student interviews indicated that some students’ failure to pick the correct alternative for this question might be influenced by use of the word “always” in the correct answer, which discouraged those students that find chemistry to be a subject full of exceptions.

Hierarchical SAPO-11 molecular sieves were synthesized with three different mesopore structure directing agents (meso-SDAs): cetyltrimethylammonium bromide (CTAB), polyvinyl alcohol (PVA) and [3-(trimethoxysilyl) propyl] dimethyloctadecylammonium chloride (TPOAC). Two model reactions, methanol-to-hydrocarbons (MTH) and the Beckmann rearrangement (BMR) of cyclohexanone oxime, were employed to evaluate the pore topology and acid site locations of the hydrothermally synthesized hierarchical SAPO-11s. Initially, the modified porosity of the hierarchical SAPO-11s was thoroughly probed by employing a set of general characterization methods and by comparing the results to the conventional microporous C-SAPO-11. The nitrogen physisorption results revealed that CTAB-11 had a uniform distribution of mesopores centered at 2.8 nm, whereas the presence of mesopores in PVA-11 could not be convincingly resolved through conventional methods. Instead, the pore topology of PVA-11 was determined by utilizing model reactions, where the shape selective MTH model reaction revealed that the sample had mesopores present through an increased production of large products compared to the conventional C-SAPO-11. Additionally, the MTH model reaction showed that while PVA shifted the location of the Bronsted acid sites (BAS) towards the mesopores, CTAB did not affect the BAS location of SAPO-11. Finally, the BMR model reaction elucidated the excellent intrapore connectivity of the hierarchical SAPO-11s through an increased lifetime compared to the conventional C-SAPO-11.

Atmospheric icing on structures and equipment represents a challenge for operation and safety. Passive ice removal by ice-phobic coatings has received much attention over the last decades. The current state-of-the-art methods for quantifying the ice-release properties of such coatings suffer from a range of drawbacks, including poor reproducibility and high complexity test setups. Here, a facile rotational tribometer approach for measuring the static friction between polymeric coatings and ice is presented. The torque necessary to initiate motion at the coating-ice interphase was used as a measure of ice release. For a polydimethylsiloxane-based coating (Sylgard 184), the effects of ice-temperature, normal force, coating thickness, and dwell time (contact time between coating and ice at rest with fully applied normal force prior to applying torque) were established along with the conditions resulting in least data variation. With these conditions, tribology-based friction measurements were carried out on two additional coatings; a two-component polyurethane, and a commercial foul release coating. The outcome of the method, i.e., grading of the coatings in terms of antiicing effect, matched those obtained with a widely used ice adhesion test method based on ice shear adhesion testing. The same trends are revealed by the two methods. However, the findings from the proposed tribology-based method result in consistently lower variation in outcomes and offer more detail on the ice adhesion and friction mechanisms. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

The mechanism and structure requirements of selective and total oxidation of methane in a chemical looping process are both experimentally and theoretically examined on La1–xSrxFeO3−δ (x = 0, 0.2, and 0.5) and La0.5Sr0.5Fe1–xCoxO3−δ (x = 0.5 and 1) perovskites. The oxygen mobility in the perovskites described by the formation energy of oxygen vacancy is found to have a pronounced effect on the catalytic activity and selectivity. In particular, the selectivity is controlled largely by the surface oxygen concentration or the oxygen vacancy concentration on perovskites, which depends strongly on the bulk oxygen concentration and the relative rate of the lattice oxygen diffusion with respect to the surface reaction. The substitution of Sr for La at the A site and the substitution of Co for Fe at the B site of the ABO3 perovskites dramatically increase the oxygen mobility. A higher oxygen diffusion rate, and hence enrichment of oxygen on the surface, would improve the catalyst selectivity toward total oxidation. This document is the Accepted Manuscript version of a Published Work that appeared in final form in [JournalTitle], copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acscatal.9b05154

Hierarchical SAPO-5 molecular sieves were synthesized with three different mesopore structure-directing agents (meso-SDAs) (cetyltrimethylammonium bromide (CTAB), myristyltrimethylammonium bromide (MTMAB) and [3-(trimethoxysilyl)propyl] dimethyloctadecylammonium chloride (TPOAC)) based on a soft-template hydrothermal synthesis procedure. To investigate the modified porosity of the hierarchical SAPO-5s, they were characterized thoroughly with the results being compared to the conventional microporous SAPO-5. Nitrogen sorption measurements revealed considerable hysteresis loops for the hierarchical SAPO-5s as well as larger mesopore volumes (�0.15 cm3 g-1) compared to the conventional SAPO-5 (0.05 cm3 g-1). The relative number of acid sites for each sample was calculated from FTIR adsorption data and was in the order of C-SAPO-5>HCTAB>H-MTMAB>H-TPOAC. The hierarchical SAPO-5s had a significantly increased lifetime (>150 h) in the methanol to hydrocarbons (MTH) model reaction compared to the conventional SAPO-5 (

Icing on surfaces has always been a problem if water is present under freezing conditions. The ice can cause large damage to equipment and installations, and it is therefore of greatest interest to look into possibilities to avoid icing. Passive icephobic coatings are one way to impede ice formation. Hydrophobic surfaces will limit the amount of water available for nucleation and ice formation. The surface structure is important to minimize the contact area to the water, and hierarchical structures may give superhydrophobic surfaces. In real applications, some water will always be present, and due to the resulting ice formation, surfaces with low ice adhesion are preferred. An anti-icing surface combines these properties: ensures high degree of water repellency, delays any ice nucleation, and show low ice adhesion. Finally, the mechanical properties and the durability of such surfaces/coatings are of the greatest importance to ensure lifelong functionality.

The ferritic stainless steel Crofer 22 APU is attractive for the use as interconnects in solid oxide fuel cell stacks. The oxidation rate of this alloy in air at 800 °C was reduced by pre-oxidation at higher temperatures in either air or N2-9%H2-1%H2O. Conversely, the oxidation rate increased when the alloy grain size was increased by heat-treating in H2 (pO2 ∼ 10−21 atm). In all cases the scale formed on Crofer 22 APU consisted of an outer (Mn,Cr)3O4 layer, an inner Cr2O3 layer and sub-scale MnCr2O4 nodules that preferentially formed at alloy grain boundaries.

Manganese cobalt spinel oxides are promising coating materials for corrosion protection of metallic interconnects in solid oxide fuel cell stacks. This work investigates how Fe and Cu doping affect the crystal structure, thermal expansion and electrical conductivity of the MnCo2−xMxO4 (M = Cu, Fe; x = 0.1, 0.3, 0.5) spinel oxides. Single phase cubic spinels were successfully prepared by spray pyrolysis. The electrical conductivity between room temperature and 1000 °C increased with addition of Cu and decreased with addition of Fe. The thermal expansion coefficient (TEC) between 50 and 800 °C decreased from 14.4 to 11.0 × 10−6 K−1 going from MnCo2O4 to MnCo1.5Fe0.5O4. The TEC of the Cu substituted materials did not follow any obvious trend with composition and was likely influenced by precipitation of CuO during heating. Based on their physical properties, the Fe doped materials are the most attractive for application as SOFC interconnect coatings.

The top layer of a typical high pressure floor laminate (HPL) consists of a melamine formaldehyde (MF) impregnated special wear layer (overlay) with alumina particles. This top layer plays a crucial role in determining the mechanical properties of the laminate. For HPLs, scratch resistance and scratch visibility are particularly important properties. This study aimed to improve the mechanical properties, particularly the scratch resistance, by adjusting the composition of the overlay. Laminates containing alumina particles were prepared and tested. These alumina particles were additionally functionalized with a silane coupling agent to ensure better adhesion between the particles and the resin. The functionalized particles led to enhanced scratch resistance of the laminates as well as improved dispersion of the particles within the resin. Micro scratch testing revealed that by using functionalized particles, the scratch surface damage was reduced and the recovery characteristics of the surface layer were improved. Higher scratch resistance and scratch hardness were thus obtained, along with a reduced scratch visibility. © 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

Vertical cracks are beneficial in thermal barrier coatings due to enhanced thermo-mechanical compliance. Accordingly, an aqueous nitrate based precursor solution was atomized on stainless steel substrates by spray pyrolysis to deposit thick crack-designed lanthanum zirconate coatings. Coatings with designed crack patterns were deposited and characterized by electron microscopy, tribology, Vickers indentation, and thermal diffusivity. The crystallization of the coatings was investigated by in situ high temperature X-ray diffraction. The green coatings crystallized from 600 °C and the pyrochlore structure was formed after heat treatment at 1000 °C. Crystalline lanthanum zirconate multilayered coatings with small crack spacing and crack opening exhibited a higher density, a higher hardness, lower thermal diffusivities, and higher thermal conductivities compared to crystalline monolayered coatings of similar thickness with large crack spacing and crack opening. The thermal diffusivity of the coatings, ∼28 mm2/s at room temperature, was similar to the values reported for yttria-stabilized zirconia plasma sprayed coatings. © 2013. This is the authors’ accepted and refereed manuscript to the article. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/

The fabrication of thick nanostructured lanthanum zirconate thermal barrier coatings deposited by spray pyrolysis from aqueous nitrate based precursor solutions is presented. After deposition, the green coatings are decomposed to introduce vertical cracks which are beneficial to enhance the thermo-mechanical compliance of the coatings. The cracks were stable after crystallization of the coatings to the cubic pyrochlore structure by further heat-treatment. Nanocrystalline mono- and multi-layered coatings with contrasting crack patterns were produced based on the knowledge of the influence of the different parameters. Multilayered coatings with small crack spacing and crack opening exhibited a higher density, a lower thermal diffusivity, and a higher thermal conductivity of ~ 0.34 W/(m·K) at elevated temperatures compared to monolayered coatings of similar thickness with larger crack spacing and crack opening. The low thermal properties of the crystalline coatings were attributed to the nanostructure of the coatings.

Manganese cobalt spinel oxides are promising materials for protective coatings for solid oxide fuel cell (SOFC) interconnects. To achieve high density such coatings are often sintered in a two-step procedure, involving heat treatment first in reducing and then in oxidizing atmospheres. Sintering the coating inside the SOFC stack during heating would reduce production costs, but may result in a lower coating density. The importance of coating density is here assessed by characterization of the oxidation kinetics and Cr evaporation of Crofer 22 APU with MnCo1.7Fe0.3O4 spinel coatings of different density. The coating density is shown to have minor influence on the long-term oxidation behavior in air at 800 °C, evaluated over 5000 h. Sintering the spinel coating in air at 900 °C, equivalent to an in-situ heat treatment, leads to an 88% reduction of the Cr evaporation rate of Crofer 22 APU in air-3% H2O at 800 °C. The air sintered spinel coating is initially highly porous, however, densifies with time in interaction with the alloy. A two-step reduction and re-oxidation heat treatment results in a denser coating, which reduces Cr evaporation by 97%. © 2017. This is the authors’ accepted and refereed manuscript to the article. Locked until 12.4.2019 due to copyright restrictions. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/

MnCo2O4, MnCo1.7Cu0.3O4 and MnCo1.7Fe0.3O4 are investigated as coatings for corrosion protection of metallic interconnects in solid oxide fuel cell stacks. Electrophoretic deposition is used to deposit the coatings on Crofer 22 APU alloy. All three coating materials reduce the parabolic oxidation rate in air at 900 °C and 800 °C. At 700 °C there is no significant difference in oxidation rate between coated samples and uncoated pre-oxidized Crofer 22 APU. The cross-scale area specific resistance (ASR) is measured in air at 800 °C using La0.85Sr0.1Mn1.1O3 (LSM) contact plates to simulate the interaction with the cathode in a SOFC stack. All coated samples have three times lower ASR than uncoated Crofer 22 APU after 4370 h aging. The ASR increase with time is lowest with the MnCo2O4 coating, followed by the MnCo1.7Fe0.3O4 and MnCo1.7Cu0.3O4 coatings. LSM plates contacted to uncoated Crofer 22 APU contain significant amounts of Cr after aging, while all three coatings effectively prevent Cr diffusion into the LSM. A complex Cr-rich reaction layer develops at the coating-alloy interface during oxidation. Cu and Fe doping reduce the extent of this reaction layer at 900 °C, while at 800 °C the effect of doping is insignificant.

Processing of dense and thin ceramic membrane layers for high temperature selective oxygen separation is addressed in this study. Mixed oxygen-ionic and electronic conducting perovskite oxide system based on La 0.2 Sr 0.8 Fe 0.8 Ta 0.2 O 3− δ composition is employed for processing of structural and functional layers. Special focus is aimed at obtaining thin layer and final microstructure with particle size in the sub-micron range. Thin layer deposition is performed by dip coating technique using stable colloidal suspension of perovskite particles dispersed within ethanol media. Two polymer based surfactants were screened for their effect on particle agglomeration and rheological response. By using optimum quantity of 2.5 wt.% addition of selected surfactant it is possible to obtain dense 15–60 μm thick functional layers. The thermal cycle applied resulted in final particle sizes within sub-micron range. By employing suspension with pore former it was possible to significantly increase the surface area of the functional layer.

An aqueous nitrate-based precursor solution was deposited on stainless steel substrate by spray pyrolysis to produce thick lanthanum zirconate coatings for thermal barrier coating application. The as-deposited, dried, and further annealed coatings were characterized by thermogravimetry, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The influence of the substrate temperature on the film formation and microstructure has been carefully studied for a better understanding of the deposition mechanisms. A temperature range corresponding to the deposition of an ionic salt liquid was found to be critical to obtain thick crack-free green coatings. Further heat treatment was necessary to decompose the nitrate species into an oxide coating with a fine porous microstructure.

A spray pyrolysis route to BaZrO 3 (BZ) and BaZr 0.9 Y 0.1 O 2.95 (BZY) powders was developed starting from nitrate solutions. Homogeneous powders with a grain size of ~ 100 nm were achieved. A calcination of the powder was necessary to remove carbonates formed during the spray pyrolysis. Hot pressing was in comparison with conventional sintering more effective to enhance densification and suppress grain growth, and dense (> 96%) materials with homogeneous microstructure were obtained. The Y-substitution decreased the densification rate. Minor amounts of a secondary phase was observed at the grain boundary triple points of BZY, but the grain boundaries were otherwise found to be coherent and without significant secondary phase accumulation. Impedance spectroscopy vs T, pO 2 and pH 2 O of conventionally sintered BZ and hot-pressed BZY demonstrated that the conductivity of BZ was orders of magnitude lower than compared to BZY. The conductivity of BZ displayed mixed proton and p-type electronic conduction characteristics in the grain interior which was depressed at the grain boundaries. The grain boundaries showed an additional n-type electronic conduction under reducing conditions. The conductivity characteristics were according to core-space charge layer theory. BZ seems to exhibit a larger ratio of p-type electronic to protonic conduction as compared to BZY, contrary to the prediction of simple defect chemistry.

High temperature proton conducting solid oxide fuel cells (PC-SOFCs) are in a developing state. Electrolytes in these cells should exhibit proton conductivity with essentially no electronic and little other ionic conductivity, as well as long-term stability in acidic atmospheres. Acceptor substituted rare-earth ortho-niobates and ortho-tantalates were recently demonstrated to exhibit proton conductivity in wet atmospheres, with a maximum of ∼10–3 S cm–1 for 1% Ca-doped LaNbO4. This modest proton conductivity requires that the electrolyte thickness is in the micron range to reach acceptable PC-SOFC performances. The long-term chemical stability and a proton transference number close to unity make these materials highly interesting for high temperature fuel cell applications, in contrast to the more investigated acceptor-doped BaCeO3 that shows instability towards acidic atmospheres. Here, we describe collaborative efforts between Norwegian partners: SINTEF, Norwegian University of Science and Technology (NTNU) and the University of Oslo for developments towards a fuel cell based on LaNbO4. This comprises identification of materials for the electrodes, interconnect and sealing, optimisation of the microstructures of all cell components, development of shaping processes and design of the fuel cell stack. We address the crucial technological issues of building and testing a PC-SOFC stack, as well as the comprehensive fundamental understanding of all the processes involved – from fabrication and behaviour of individual components to fabrication of PC-SOFC fuel cell stacks.

Thermal and mechanical properties of polycrystalline La 1− x A x NbO 4 ( x = 0, 0.005, 0.02 and A = Ca, Sr and Ba) are reported. The materials possess a ferroelastic to paraelastic phase transition close to 500 °C, and the linear thermal expansion is significantly lower (∼8.6 ± 0.5 × 10 −6 °C −1 ) for the paraelastic phase compared to the ferroelastic phase (∼15 ± 3 × 10 −6 °C −1 ). The hardness was significantly higher for acceptor doped materials (∼6 GPa) compared to pure LaNbO 4 (∼3 GPa) due to a significantly smaller average grain size. The fracture toughness of La 0.98 Sr 0.02 NbO 4 , measured by single edge V-notched beam method, was 1.7 ± 0.2 MPa m 1/2 independent of temperature up to 600 °C. The ferroelastic properties of the materials were confirmed by non-linear relationships between stress and strain during compression/decompression, a remnant strain after decompression and the presence of ferroelastic domains. The mechanical properties of LaNbO 4 -based materials are discussed with focus on ferroelasticity, microcracking due to crystallographic anisotropy and pinning of ferroelastic domain boundaries.

The characteristics of the profiles of elastic modulus and hardness of the steel fiber-matrix and fiber-matrix-aggregate interfacial zones in steel fiber reinforced mortars have been investigated by using nanoindentation and Scanning Electron Microscopy (SEM), where two sets of parameters, i.e. water/binder ratio and content of silica fume were considered. Different interfacial bond conditions in the interfacial transition zones (ITZ) are discussed. For sample without silica fume, efficient interfacial bonds across the steel fiber-matrix and fiber-matrix-aggregate interfaces are shown in low water/binder ratio mortar; while in high water/binder ratio mortar, due to the discontinuous bleeding voids underneath the fiber, the fiber-matrix bond is not very good. On the other hand, for sample with silica fume, the addition of 10% silica fume leads to no distinct presence of weak ITZ in the steel fiber-matrix interface; but the effect of the silica fume on the steel fiber-matrix-aggregate interfacial zone is not obvious due to voids in the vicinity of steel fiber.

Ferroelastic domain reorientation in polycrystalline rhombohedral LaCoO 3 has been demonstrated by backscatter electron (BSE) imaging and electron backscatter diffraction (EBSD) combined with in situ compression testing. Four different domain orientations were confirmed in line with expectation from crystallography. During in situ compression reorientation of domains were observed favoring domains with the c-axis close to perpendicular to the stress field. In situ compression combined with BSE/EBSD is shown to be an excellent tool for studying the influence of mechanical stress on grain/domain structure in polycrystalline ceramics.

Compressive creep tests have been performed on perovskite-type Ba0.5Sr0.5Co0.8Fe0.2O3 − δ ceramics. The activation energy, stress exponent and inverse grain size exponent of the steady-state creep rates are evaluated at p(O2) = 0.21 ∙ 105 Pa and 0.01 ∙ 105 Pa in the stress, temperature and grain size ranges 5–20 MPa, 1078–1208 K and 2.5–17.4 µm, respectively. The results indicate that the creep rate of Ba0.5Sr0.5Co0.8Fe0.2O3 − δ is controlled by diffusion of cations via both the oxide lattice (bulk diffusion) and along grain boundaries. The creep rate of Ba0.5Sr0.5Co0.8Fe0.2O3 − δ increases profoundly by more than one order of magnitude at 1153–1178 K, which is tentatively linked with the onset of the hexagonal-to-cubic phase transition in this compound.

Asymmetric proton conducting membranes and fuel cells based on Sr-doped LaNbO 4 have been prepared. Porous supports were made by aqueous tape casting, where the porosity was ensured by adding pore fillers. The viscosity of the slips was found in the range 410–500 cP at a shear rate of 50 s − 1 , depending on type of pore filler. Particle size and particle size distribution of the slips were investigated by wet-SEM technique, and demonstrating sub-micron size powders well dispersed in the slips. Carbon black was shown to be the best pore filler with connected pores and only open porosity. The O 2 -flux was measured to 13.8 ml min − 1 cm − 2 mm for a 42% porous substrate in an O 2 -He gradient, normalized with respect to the thickness. Dense asymmetric membranes were deposited on porous substrates by spray coating. Fuel cells were prepared by spray coating of electrolyte and cathode on an anode support made by tape casting.

Twin structures in rhombohedrally distorted polycrystalline LaCoO3, La0.8Ca0.2CoO3-δ and La0.5Sr0.5Co0.5Fe0.5O3-δ have been studied by transmission electron microscopy. Normal {100} and {110} twinning was predominant in LaCoO3 and La0.8Ca0.2CoO3-δ. In addition, ferroelastic domains with a one-dimensional superstructure corresponding to a tripling of the pseudocubic lattice parameter, a c, were found in some grains. The monoclinic superstructure vanished over time and was sensitive to external mechanical stress. In La0.5Sr0.5Co0.5Fe0.5O3-δ no normal twinning was observed, but domains with a one-dimensional superstructure of two times a c were observed. The superstructures have been interpreted as atomic scale twinning, which reduce the crystal symmetry from rhombohedral to monoclinic.

Oxygen deficiency, thermal and chemical expansion of La 0.5 Sr 0.5 Fe 1− x Co x O 3− δ ( x = 0, 0.5, 1) have been measured by thermogravimetry, dilatometry and high temperature X-ray diffraction. The rhombohedral perovskite materials transformed to a cubic structure at 350 ± 50 °C. The thermal expansion of the materials up to the onset of thermal reduction was 14–18 × 10 − 6 K − 1 . Above 500 °C in air (400 °C in N 2 ), chemical expansion contributed to the thermal expansion and the linear thermal expansion coefficients were significantly higher, 16–35 × 10 − 6 K − 1 . The chemical expansion, e c , showed a maximum of 0.0045 for x = 0.5 and 0.0041 for x = 1 at 800–900 °C. The normalized chemical expansion, e c /Δ δ , was 0.036 for x = 0.5 and 0.035 for x = 1 at 800 °C. The chemical expansion can be correlated with an increasing ionic radius of the transition metals with decreasing valence state.

Oxygen flux through La 0.5 Sr 0.5 Fe 1− x Co x O 3− δ ( x = 0, 0.5 and 1) membranes has been determined as a function of oxygen partial pressure, temperature and time. The flux was diffusion controlled for low pO 2 gradients while larger pO 2 gradients caused a surface exchange controlled flux. The activation energy of the oxygen flux varied in the range 67–105 kJ/mol. After about 1 month at 1150 °C in an O 2 /N 2 gradient the membranes were examined for kinetic demixing and decomposition. On the reducing side only the original perovskite phase was observed at the surface, while on the oxidizing side various secondary phases were observed dependent on the composition at the Fe/Co-site and the Sr + La/Fe + Co ratio of the materials. Moreover, kinetic demixing of the main perovskite phase was also observed, particularly near the surfaces. Grain growth and pore coalescence resulting in membrane expansion were also observed in some cases. The present findings are discussed with regard to the long term chemical stability of the membranes.

Steady-state compressive creep rate of La0.5Sr0.5Fe0.5Co0.5O3−δ (LSFC) and La0.5Sr0.5CoO3−δ (LSC) is reported in the temperature region 900°–1050°C and stress range 5–28 MPa. The stress exponents for the two materials were 1.71±0.18 and 1.24±0.15, respectively. The activation energy for creep was considerably higher for LSC (619±56 kJ/mol) than for LSFC (392±28 kJ/mol). The grain size exponent for LSC was 1.28±0.14. Considerably higher creep rates were observed for both materials in N2 compared with air. Relaxation by creep of chemical-induced stresses in oxygen-permeable membranes is addressed, especially at low partial pressure of oxygen.

Young’s modulus, strain–stress behavior, fracture strength, and fracture toughness of % MathType!Translator!2!1!AMS LaTeX.tdl!TeX -- AMS-LaTeX! % MathType!MTEF!2!1!+- % feaaeaart1ev0aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX % garmWu51MyVXgatuuDJXwAK1uy0HwmaeHbfv3ySLgzG0uy0Hgip5wz % aebbnrfifHhDYfgasaacH8qrps0lbbf9q8WrFfeuY-Hhbbf9v8qqaq % Fr0xc9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qq % Q8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeWaeaaakeaaca % qGmbGaaeyyamaaBaaaleaacaaIWaGaaiOlaiaaiwdaaeqaaOGaae4u % aiaabkhadaWgaaWcbaGaaGimaiaac6cacaaI1aaabeaakiaabAeaca % qGLbWaaSbaaSqaaiaaigdacqGHsislcaWG4baabeaakiaaboeacaqG % VbWaaSbaaSqaaiaadIhaaeqaaOGaae4tamaaBaaaleaacaaIZaGaey % OeI0IaeqiTdqgabeaaaaa!4B94! $$ {\text{La}}_{{0.5}} {\text{Sr}}_{{0.5}} {\text{Fe}}_{{1 - x}} {\text{Co}}_{x} {\text{O}}_{{3 - \delta }} $$ (0≤×≤1) materials have been investigated in the temperature range 20–1,000°C. Young’s moduli of % MathType!Translator!2!1!AMS LaTeX.tdl!TeX -- AMS-LaTeX! % MathType!MTEF!2!1!+- % feaaeaart1ev0aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX % garmWu51MyVXgatuuDJXwAK1uy0HwmaeHbfv3ySLgzG0uy0Hgip5wz % aebbnrfifHhDYfgasaacH8qrps0lbbf9q8WrFfeuY-Hhbbf9v8qqaq % Fr0xc9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qq % Q8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeWaeaaakeaaca % WGmbGaamyyamaaBaaaleaacaaIWaGaaiOlaiaaiwdaaeqaaOGaam4u % aiaadkhadaWgaaWcbaGaaGimaiaac6cacaaI1aaabeaakiaadAeaca % WGLbWaaSbaaSqaaiaaicdacaGGUaGaaGynaaqabaGccaWGdbGaam4B % amaaBaaaleaacaaIWaGaaiOlaiaaiwdaaeqaaOGaam4tamaaBaaale % aacaaIZaGaeyOeI0IaeqiTdqgabeaaaaa!4C5A! $${{\rm La}}_{{0.5}} {{\rm Sr}}_{{0.5}} {{\rm Fe}}_{{0.5}} {{\rm Co}}_{{0.5}} {{\rm O}}_{{3 - \delta }}$$ and % MathType!Translator!2!1!AMS LaTeX.tdl!TeX -- AMS-LaTeX! % MathType!MTEF!2!1!+- % feaaeaart1ev0aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX % garmWu51MyVXgatuuDJXwAK1uy0HwmaeHbfv3ySLgzG0uy0Hgip5wz % aebbnrfifHhDYfgasaacH8qrps0lbbf9q8WrFfeuY-Hhbbf9v8qqaq % Fr0xc9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qq % Q8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeWaeaaakeaaca % WGmbGaamyyamaaBaaaleaacaaIWaGaaiOlaiaaiwdaaeqaaOGaam4u % aiaadkhadaWgaaWcbaGaaGimaiaac6cacaaI1aaabeaakiaadoeaca % WGVbGaam4tamaaBaaaleaacaaIZaGaeyOeI0IaeqiTdqgabeaaaaa!45E3! $${{\rm La}}_{{0.5}} {{\rm Sr}}_{{0.5}} {{\rm CoO}}_{{3 - \delta }}$$ , measured by resonant ultrasound spectroscopy, were 130±1 and 133±3 GPa, respectively. The nonlinear stress–strain relationship observed by four-point bending at room temperature was inferred as a signature of ferroelastic behavior of the materials. Above the ferroelastic to paraelastic transition temperature, the materials showed elastic behavior, but due to high-temperature creep, a nonelastic respond reappeared above ∼800°C. The room temperature fracture strength measured by four-point bending was in the range 107–128 MPa. The corresponding fracture toughness of % MathType!Translator!2!1!AMS LaTeX.tdl!TeX -- AMS-LaTeX! % MathType!MTEF!2!1!+- % feaaeaart1ev0aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX % garmWu51MyVXgatuuDJXwAK1uy0HwmaeHbfv3ySLgzG0uy0Hgip5wz % aebbnrfifHhDYfgasaacH8qrps0lbbf9q8WrFfeuY-Hhbbf9v8qqaq % Fr0xc9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qq % Q8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeWaeaaakeaaca % WGmbGaamyyamaaBaaaleaacaaIWaGaaiOlaiaaiwdaaeqaaOGaam4u % aiaadkhadaWgaaWcbaGaaGimaiaac6cacaaI1aaabeaakiaadAeaca % WGLbWaaSbaaSqaaiaaicdacaGGUaGaaGynaaqabaGccaWGdbGaam4B % amaaBaaaleaacaaIWaGaaiOlaiaaiwdaaeqaaOGaam4tamaaBaaale % aacaaIZaGaeyOeI0IaeqiTdqgabeaaaaa!4C5A! $${{\rm La}}_{{0.5}} {{\rm Sr}}_{{0.5}} {{\rm Fe}}_{{0.5}} {{\rm Co}}_{{0.5}} {{\rm O}}_{{3 - \delta }}$$ , measured by single edge V-notch beam method, was 1.16±0.12 MPa·m1/2. The measured fracture strength and fracture toughness were observed to increase with increasing temperature. The fracture mode changed from intragranular at low temperature to intergranular at high temperature. Tensile stress gradient at the surface of the materials caused by a frozen-in gradient in the oxygen content during cooling was proposed to explain the low ambient temperature fracture strength and toughness.

LaCoO3 and LaFeO3 based perovskites have been studied as model materials for oxygen permeable membranes. To avoid gas leakages it is of crucial importance to obtain dense membranes, hence the densification behavior in terms of temperature, stoichiometry (AB-ratio), presence of secondary phases and substituents (Ca and Sr) have been investigated. Only a narrow temperature window for the sintering is available and it is important to avoid the formation of secondary phases. The upper temperature to obtain high density materials is limited by a severe swelling. Mechanical properties such as bending strength and fracture toughness have been determined both at ambient- and elevated temperatures. Non elastic behaviour due to ferroelasticity is reported for pure LaFeO3, LaCoO3 and La0.8Ca0.2CoO3. The ferroelasticity is found to influence the behavior of the fracture toughness and fracture strength as a function of temperature. The electrical conductivity of pure LaFeO3 at 1000°C is determined in terms of partial pressure of oxygen. Cation diffusion is found to be rate controlling for the establishment of a time independent conductivity in the p-conductivity regime.

Begroing er en utfordring for mange deler av industri, inkludert skipsfart, vannrensing og fiskeoppdrett. Bunnstoff har blitt brukt for å takle problemet siden det 17. århundre. Økologiske skader som følge av bruk av tributyltin (TBT) som tilsetningsstoff gjennom det 20. århundre har gjort det nødvendig med nye løsninger. Grafenmaterialer er en ny klasse av vidundermaterialer som har blitt undersøkt grundig siden oppdagelsen i 2004. Grafenoksid (GO) et av materialene og har vist lovende resultater når det kommer til veksthindring. Grafenmaterialer kan også brukes som tilsetningsstoff i produksjon av nano-kompositter, ved gi økt styrke til polymerbelegg. I denne oppgaven var målet å syntetisere et veksthemmende belegg ved å tilsette GO til en sol basert på Tetraetylenortosilikat (TEOS) monomer. En passende syntese ble funnet ved å se på topologi og morfologi av belagte prøver. Hovedutfordringen var å produsere stabil sol ved tilsats av GO. Prøver med ulike konsentrasjoner av GO ble testet for veksthemmende effekt i biofilmreaktor. Til sist ble slitestyrke testet for å se om komposittbeleggene fikk økt styrke. Resulatene viste belegg med økende vekstprosent GO viste betydaelig veksthemmende effekt, sammenlignet med referanse. 1 vektprosent var de mest lovende prøvene. Økt slitestyrke som følge av økt mengde ble undersøkt. Friksjonen under testing var noe lavere jevnt over for prøvene med GO sammenlignet med referanse. Ingen konklusjon kunne derimot dras på bakgrunn av enkelte anomalier. Resultatene for slitestyrke belyser nødvendigheten for videre testing. Biofouling is a challenge for many fields of industry including shipping, water treatment and fish farms. Antifouling coatings have been used to prevent the biofouling since the 17th century. The ecological damage caused by TBT coatings during the 20th century, highlighted the need for new alternatives. Graphene Materials is a new group of wonder materials that has been researched extensively since it was discovered in 2004. Graphene Oxide (GO) is one of those materials and has documented promising antifouling properties. GO can also be used as an additive in the production of nanocomposites, adding strength to polymer coatings. The object of this thesis was to synthesise an antifouling coating by adding GO to a siloxane coating made by sol gel method. A suitable synthesis route was found by looking at the morphology and topology of coated samples. The main challenge was producing a stable sol solution upon addition of GO. Samples with different concentrations of GO was tested for antifouling ability in biofilm reactor. Lastly wear resistance of coatings were tested to see if the nanocomposite had increased strength relative to the reference. The results showed that increasing weight percents of GO showed significant reduction in fouling compared to reference. 1 wt% was the most promising concentration. Addition of GO did reduce friction during wear in 1 and 10 wt% sample compared to reference. However, the results were not conclusive, due to several anomalies. The results for wear resistance highlights the need for further testing.