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Fully ceramic anodes such as LSTN-CGO offer some specific advantages compared to conventional cermet anodes. Ceria- and titanate-based phases are both mixed ionic and electronic conductors (MIEC), which leads to very different reaction mechanisms and associated requirements for the microstructure design compared to e.g. Ni-YSZ. Due to the MIEC-property of both solid phases, the transports of neither the electrons nor the oxygen ions are limited to a single phase. As a consequence, composite MIEC electrodes reveal a remarkable property that can be described as ‘composite conductivity’ (for electrons as well as for ions), which is much higher than the (hypothetical) single phase conductivities of the same microstructure. In composite MIEC anodes, the charge carriers can reach the reaction sites even when the volume fraction of one MIEC phase is below the percolation threshold, because the missing contiguity is automatically bridged by the second MIEC phase. The MIEC properties thus open a much larger design space for microstructure optimization of composite electrodes. In this contribution, the composite conductivities of MIEC-based anodes are systematically investigated based on virtual materials testing and stochastic modeling. For this purpose, a large number of 3D microstructures, representing systematic compositional variations of composite anodes, is created by microstructure modeling. The underlying stochastic model is fitted to experimental data from FIB-SEM tomography. For the fitting of the stochastic model, digital twins of the tomography data are created using the methodology of gaussian random fields. By interpolation between and beyond the digital twin compositions, the stochastic model then allows to create numerous virtual 3D microstructures with different compositions, but with realistic properties. The effect of microstructure variation on the composite conductivity is then determined with transport simulations for each 3D microstructure. Furthermore

Reference: 1. P. Marmet et al., Phys. Chem. Chem. Phys., 2021, 23(40), 23042–23074, doi: 10.1039/d1cp01962g., Fully ceramic anodes such as LST-CGO offer some specific advantages compared to conventional Ni-based cermets. Ceria- and titanate-based phases are both mixed ionic and electronic conductors (MIEC), which leads to very different reaction mechanisms and associated requirements for the microstructure design compared to e.g. Ni-YSZ. In MIEC anodes, the reaction mainly takes place on the twophase boundaries of ceria (instead of the three-phase boundaries). Due to the MIEC-property of both solid phases, the transports of neither the electrons nor the oxygen ions are limited to a single phase. This leads to an effective composite conductivity (for electrons as well as for ions), which is much higher than the (hypothetical) single phase conductivity. In such a system, the charge carriers can reach the reaction sites even when the phase volume fraction(s) is/are below the percolation threshold. In this contribution, methodologies for the digital materials design (DMD) are presented to investigate the much larger design space opening for composite MIEC electrodes. Stochastic digital twins representing the 3D microstructure are constructed based on Gaussian random fields for real structures obtained from 3D-tomography. Based on stochastic parameters of digital twins, a large variation of virtual 3D microstructures is then realized using massive simultaneous cloud computing (MSCC) with GeoDict software. All relevant microstructure characteristics are determined by image analysis and/or transport simulation (e.g. the relative ionic composite conductivity and the specific pore-CGO interface area). The effect of the microstructure properties on the cell-performance is then determined with a suitable multiphysics model (see Marmet et al.1). This combination of DMDmethodologies (3D imaging and image analysis, stochastic modelling, numerical simulation) allows for a systematic and data driven optimization to provide robust design guidelines for MIEC-based anodes.

Highly ordered titania nanotubes (TNTs) as a 1D nanostructured material have received a lot of interest for supercapacitor applications due to their large surface area and relatively low cost. In this study, TNTs was synthesized by anodization in glycerol-based electrolytes. Electrochemical reduction process was used to modify the TNTs to overcome its high resistivity. The reduced titania nanotubes (R-TNTs) show improved capacitance of 2.28 mF cm-2 which is 7 times higher than TNTs. The R-TNTs exhibit a rectangular cyclic voltammograms and symmetrical triangular charge-discharge curves which are ideal characteristics of electric double layer capacitors (EDLCs). Furthermore, MnO2, NiO and binary NiMn2O4 were incorporated into the nanotubular structures of R-TNTs by pulse electrodeposition (PED) to enhance the capacitive performance of R-TNTs. The capacitance increased to 50.81 mF cm-2, 16.57 mF cm-2 and 97.52 mF cm-2 for MnO2/R-TNTs, NiO/R-TNTs and NiMn2O4/R-TNTs, respectively. All cyclic voltammograms and galvanostatic charge-discharge curves from these samples measured in 1M KCl using three electrode-configuration indicate a pseudocapacitive contribution from the deposited metal oxides. The highest capacitance obtained for the NiMn2O4/R-TNTs composite is attributed to the synergistic effects of the MnO2 and NiO deposited onto high conductivity RTNTs. Physical characterization of all the synthesized samples was conducted by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Higher energy and power density of 5.31 mWh cm-2 and 190.91 mW cm-2 respectively were obtained for NiMn2O4/R-TNTs asymmetric cell in two-electrode configuration.

Highly ordered titania nanotubes (TNTs) as a 1D nanostructured material have received a lot of interest for supercapacitor applications due to their large surface area and relatively low cost. In this study, TNTs was synthesized by anodization in glycerol-based electrolytes. Electrochemical reduction process was used to modify the TNTs to overcome its high resistivity. The reduced titania nanotubes (R-TNTs) show improved capacitance of 2.28 mF cm-2 which is 7 times higher than TNTs. The R-TNTs exhibit a rectangular cyclic voltammograms and symmetrical triangular charge-discharge curves which are ideal characteristics of electric double layer capacitors (EDLCs). Furthermore, MnO2, NiO and binary NiMn2O4 were incorporated into the nanotubular structures of R-TNTs by pulse electrodeposition (PED) to enhance the capacitive performance of R-TNTs. The capacitance increased to 50.81 mF cm-2, 16.57 mF cm-2 and 97.52 mF cm-2 for MnO2/R-TNTs, NiO/R-TNTs and NiMn2O4/R-TNTs, respectively. All cyclic voltammograms and galvanostatic charge-discharge curves from these samples measured in 1M KCl using three electrode-configuration indicate a pseudocapacitive contribution from the deposited metal oxides. The highest capacitance obtained for the NiMn2O4/R-TNTs composite is attributed to the synergistic effects of the MnO2 and NiO deposited onto high conductivity RTNTs. Physical characterization of all the synthesized samples was conducted by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Higher energy and power density of 5.31 mWh cm-2 and 190.91 mW cm-2 respectively were obtained for NiMn2O4/R-TNTs asymmetric cell in two-electrode configuration.

Cesium and sodium titanates with the respective stoichiometries of CsxTi2-x/4□x/4O4 (x ≈ 0.7) and Na2Ti6O13 was synthesized by making use of the Pechini sol-gel method. Direct intercalation of hydrazine hydrate in cesium and sodium titanates proved unsuccessful with the direct intercalation of ammonium into cesium titanate achieved. The protonated form of cesium titanate was successfully intercalated with hydrazine hydrate. Findings of the structural properties of the various titanates obtained from X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, Fourier-Transform Infra-Red spectroscopy, Raman spectroscopy and transmission electron microscopy are presented

Cesium and sodium titanates with the respective stoichiometries of CsxTi2-x/4□x/4O4 (x ≈ 0.7) and Na2Ti6O13 was synthesized by making use of the Pechini sol-gel method. Direct intercalation of hydrazine hydrate in cesium and sodium titanates proved unsuccessful with the direct intercalation of ammonium into cesium titanate achieved. The protonated form of cesium titanate was successfully intercalated with hydrazine hydrate. Findings of the structural properties of the various titanates obtained from X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, Fourier-Transform Infra-Red spectroscopy, Raman spectroscopy and transmission electron microscopy are presented

Titania nanotubes array and nickel cobaltite are both widely studied metal oxide materials for applications in the field of energy storage and delivery. However, the electrochemical capacitive charge storage of titania nanotubes is generally poor because of their inferior electrical conductivity. A number of attempts at chemical modifications by doping and making composites have been performed but the effect of decorating the surface of titania nanotubes with ternary metal oxide has not been adequately addressed. This study aims to evaluate the electrochemical performance of combining titania nanotubes array with nickel cobaltite for the purpose of fabricating composite electrochemical capacitors. Further, this study also aims to evaluate the possibility of using wet impregnation method to introduce metal oxides onto titania nanotubes array. The techniques that were used in the characterisation of the samples were X-ray diffraction (XRD), cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), electrochemical impedance spectroscopy (EIS), field-emission–scanning electron microscopy (FESEM), and energy dispersive X-ray microanalyses (EDX). Parameters that were studied included anodisation duration, anodisation potential, initial molar concentration of nickel(II) nitrate solution and cobalt(II) nitrate solution, thermal treatment temperature of the precursor solution, impregnation duration, and types of electrolytes. The optimum synthesis conditions for the unmodified titania nanotubes were 60 minutes anodisation duration and 17 V anodisation potential, whereas the optimum synthesis conditions for the nickel cobaltite – titania nanotubes composite were 1.0 M initial molar concentration of nickel (II) nitrate solution and cobalt(II) nitrate solution, thermal treatment temperature of the precursor solution was 375 °C, and an impregnation duration of 60 minutes. The nickel cobaltite – titania nanotubes composite performed optimally in 1.0 M KOH. ii By the use of o

Titania nanotubes array and nickel cobaltite are both widely studied metal oxide materials for applications in the field of energy storage and delivery. However, the electrochemical capacitive charge storage of titania nanotubes is generally poor because of their inferior electrical conductivity. A number of attempts at chemical modifications by doping and making composites have been performed but the effect of decorating the surface of titania nanotubes with ternary metal oxide has not been adequately addressed. This study aims to evaluate the electrochemical performance of combining titania nanotubes array with nickel cobaltite for the purpose of fabricating composite electrochemical capacitors. Further, this study also aims to evaluate the possibility of using wet impregnation method to introduce metal oxides onto titania nanotubes array. The techniques that were used in the characterisation of the samples were X-ray diffraction (XRD), cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), electrochemical impedance spectroscopy (EIS), field-emission–scanning electron microscopy (FESEM), and energy dispersive X-ray microanalyses (EDX). Parameters that were studied included anodisation duration, anodisation potential, initial molar concentration of nickel(II) nitrate solution and cobalt(II) nitrate solution, thermal treatment temperature of the precursor solution, impregnation duration, and types of electrolytes. The optimum synthesis conditions for the unmodified titania nanotubes were 60 minutes anodisation duration and 17 V anodisation potential, whereas the optimum synthesis conditions for the nickel cobaltite – titania nanotubes composite were 1.0 M initial molar concentration of nickel (II) nitrate solution and cobalt(II) nitrate solution, thermal treatment temperature of the precursor solution was 375 °C, and an impregnation duration of 60 minutes. The nickel cobaltite – titania nanotubes composite performed optimally in 1.0 M KOH. ii By the use of o

In strongly correlated electron systems, the independent electron approximation fails and electron-electron correlations must be taken into consideration. Such systems display an abundance of technologically useful behaviors including metal-insulator transitions, superconductivity, and colossal magnetoresistance. Within the broad class of correlated materials, Mott insulators are a canonical example. These compounds have repulsive Coulomb interactions between on-site electrons large enough to open an energy gap between two portions of a valence band, thereby turning what conventional band theory would predict to be a metal into a (Mott) insulator. Despite many years of investigation, Mott insulators remain an exciting area of materials research owing in part to their proximity to quantum critical points and spin liquid ground states.Here we have studied thin films of the Mott insulating rare earth titanates RTiO3 (R = Gd, Sm), and heterostructures of these compounds with the band insulator SrTiO3. At the RTiO3/SrTiO3 interface, electrostatic doping creates a two-dimensional electron liquid (2DEL) that resides within the SrTiO3 layers near the interface. In the case of thin SrTiO3 quantum wells between magnetic RTiO3 barriers, we used polarized neutron reflectometry and muon spin rotation to show that there is a critical well thickness below which the 2DEL electrons exhibit magnetic correlations. This critical thickness was found to be independent of the sign of the magnetic exchange interactions in the neighboring RTiO3 barriers. A follow up study on thin GdTiO3 layers embedded within SrTiO3 revealed magnetic dead layers at the interface of the two materials, but bulk-like ferrimagnetism within the center of the thin GdTiO3 layers. The independence of magnetism from the notable structural distortions observed within the thin GdTiO3 layers highlights the weak coupling between the magnetic exchange interactions and electronic bandwidth in this material. Finally, eleme

Pollution control to avail the protection of the environment is one of the key challenges of the current world. TiO2 based photocatalytic systems has the unique combination of activity, selectivity, stability, environmental benignity, availability and low price to tackle the environmental pollution. These allows TiO2-based photocatalytic system to be the most promising in environmental research. In this current research, different one dimensional TiO2 nanostructures are synthesized successfully using hydrothermal method. Spiral wall titanate nanotubes are prepared from the anatase TiO2 nanoparticles in both conventional and microwave-assisted alkaline hydrothermal approach. TiO2 nanowire arrays (TiNWA) were prepared on the FTO substrate from the titanium isopropoxide precursor by acid hydrothermal process. It is found that with different modified technique it is possible to alter the crystal phase, nanowire length, width and density of the TiNWAs. The produced nanostructures are then directly doped with B+, F+, P+, As+ and BF2+ ions by ion implantation method. Different acceleration energies and ion fluxes are used to optimize the implantation parameters to reduce the band gap energies of the multiwalled titanate nanotubes (TiNT). Different transition metals (Ni, Cr, Fe and Mn) are decorated on the outer wall of the multiwalled titanate nanotubes. Transition metals are deposited from the fulminating complex solution of the respective metals. Finally, different novel nonmetal/metal co-functionalized titanate nanotubes are obtained for the first time of its type. The morphology, texture, structure and composition of the novel nanostructures are characterized with different state-of-the-art techniques. The performance of the nanostructured photocatalysts are analyzed in terms of degree of degradation of different chlorophenols in different water matr

Pollution control to avail the protection of the environment is one of the key challenges of the current world. TiO2 based photocatalytic systems has the unique combination of activity, selectivity, stability, environmental benignity, availability and low price to tackle the environmental pollution. These allows TiO2-based photocatalytic system to be the most promising in environmental research. In this current research, different one dimensional TiO2 nanostructures are synthesized successfully using hydrothermal method. Spiral wall titanate nanotubes are prepared from the anatase TiO2 nanoparticles in both conventional and microwave-assisted alkaline hydrothermal approach. TiO2 nanowire arrays (TiNWA) were prepared on the FTO substrate from the titanium isopropoxide precursor by acid hydrothermal process. It is found that with different modified technique it is possible to alter the crystal phase, nanowire length, width and density of the TiNWAs. The produced nanostructures are then directly doped with B+, F+, P+, As+ and BF2+ ions by ion implantation method. Different acceleration energies and ion fluxes are used to optimize the implantation parameters to reduce the band gap energies of the multiwalled titanate nanotubes (TiNT). Different transition metals (Ni, Cr, Fe and Mn) are decorated on the outer wall of the multiwalled titanate nanotubes. Transition metals are deposited from the fulminating complex solution of the respective metals. Finally, different novel nonmetal/metal co-functionalized titanate nanotubes are obtained for the first time of its type. The morphology, texture, structure and composition of the novel nanostructures are characterized with different state-of-the-art techniques. The performance of the nanostructured photocatalysts are analyzed in terms of degree of degradation of different chlorophenols in different water matr

In strongly correlated electron systems, the independent electron approximation fails and electron-electron correlations must be taken into consideration. Such systems display an abundance of technologically useful behaviors including metal-insulator transitions, superconductivity, and colossal magnetoresistance. Within the broad class of correlated materials, Mott insulators are a canonical example. These compounds have repulsive Coulomb interactions between on-site electrons large enough to open an energy gap between two portions of a valence band, thereby turning what conventional band theory would predict to be a metal into a (Mott) insulator. Despite many years of investigation, Mott insulators remain an exciting area of materials research owing in part to their proximity to quantum critical points and spin liquid ground states.Here we have studied thin films of the Mott insulating rare earth titanates RTiO3 (R = Gd, Sm), and heterostructures of these compounds with the band insulator SrTiO3. At the RTiO3/SrTiO3 interface, electrostatic doping creates a two-dimensional electron liquid (2DEL) that resides within the SrTiO3 layers near the interface. In the case of thin SrTiO3 quantum wells between magnetic RTiO3 barriers, we used polarized neutron reflectometry and muon spin rotation to show that there is a critical well thickness below which the 2DEL electrons exhibit magnetic correlations. This critical thickness was found to be independent of the sign of the magnetic exchange interactions in the neighboring RTiO3 barriers. A follow up study on thin GdTiO3 layers embedded within SrTiO3 revealed magnetic dead layers at the interface of the two materials, but bulk-like ferrimagnetism within the center of the thin GdTiO3 layers. The independence of magnetism from the notable structural distortions observed within the thin GdTiO3 layers highlights the weak coupling between the magnetic exchange interactions and electronic bandwidth in this material. Finally, eleme

Pollution control to avail the protection of the environment is one of the key challenges of the current world. TiO2 based photocatalytic systems has the unique combination of activity, selectivity, stability, environmental benignity, availability and low price to tackle the environmental pollution. These allows TiO2-based photocatalytic system to be the most promising in environmental research. In this current research, different one dimensional TiO2 nanostructures are synthesized successfully using hydrothermal method. Spiral wall titanate nanotubes are prepared from the anatase TiO2 nanoparticles in both conventional and microwave-assisted alkaline hydrothermal approach. TiO2 nanowire arrays (TiNWA) were prepared on the FTO substrate from the titanium isopropoxide precursor by acid hydrothermal process. It is found that with different modified technique it is possible to alter the crystal phase, nanowire length, width and density of the TiNWAs. The produced nanostructures are then directly doped with B+, F+, P+, As+ and BF2+ ions by ion implantation method. Different acceleration energies and ion fluxes are used to optimize the implantation parameters to reduce the band gap energies of the multiwalled titanate nanotubes (TiNT). Different transition metals (Ni, Cr, Fe and Mn) are decorated on the outer wall of the multiwalled titanate nanotubes. Transition metals are deposited from the fulminating complex solution of the respective metals. Finally, different novel nonmetal/metal co-functionalized titanate nanotubes are obtained for the first time of its type. The morphology, texture, structure and composition of the novel nanostructures are characterized with different state-of-the-art techniques. The performance of the nanostructured photocatalysts are analyzed in terms of degree of degradation of different chlorophenols in different water matr

Perovskite oxides remain a material class with properties that can be difficult to predict. Strong electron correlations, coupling between electron, lattice, spin and orbital degrees of freedoms, combined with the versatility of the structure itself, result in a wide range of properties, with unique emergent phenomena that occur only at heterointerfaces. Structure plays an especially important role in determining the properties of perovskite oxides. Small distortions in the lattice, particularly rotations or tilts of the oxygen octahedra, can have large effects on the material’s electrical and magnetic properties. One way we can tune these rotations is by growing thin film heterostructures, allowing us to tailor the properties of these materials in ways not possible in the bulk. Therefore, determining the local atomic structure in these films is critical for understanding the structure-property relationships, and the origin of any emergent behavior that may exist at an interface.To that end, we utilize scanning transmission electron microscopy (STEM) to develop a link between the atomic structure and electrical/magnetic properties of three different systems: SrTiO3 quantum wells between GdTiO3 and SmTiO3, GdTiO3 quantum wells between SrTiO3, and strained NdNiO3. Using real-space and diffraction techniques, we obtain quantitative information on local octahedral rotations and observe the presence/absence of structural transitions. This information gives us new insight into thedriving forces behind the metal-insulator transition and magnetic behavior of the different material systems. We also continue the development of quantitative STEM for precise and accurate determination of 3D dopant atom configurations by using variable detector angles in the high angle annular dark field regime. By demonstrating the usefulness of obtaining angle-resolved scattering data, we provide a new avenue for improving STEM image contrast and atom visibility for future studies.

TiO2nanostructures are being sought after as flexibly utilizable building blocks for the fabrication of the mesoporous thin-film photoelectrodes that are the heart of the third-generation photovoltaic devices, such as dye-sensitized solar cells (DSSCs), quantum-dot-sensitized solar cells (QDSSCs), and the recently promoted perovskite-type solar cells. Here, we report deliberate tailoring of TiO2nanostructures for superior photovoltaic cells. Morphology engineering of TiO2nanostructures is realized by designing synthetic protocols in which the precursor hydrolysis, crystal growth, and oligomer self-organization are precisely controlled. TiO2nanostructures in forms varying from isolated nanocubes, nanorods, and cross-linked nanorods to complex hierarchical structures and shape-defined mesoporous micro-/nanostructures were successfully synthesized. The photoanodes made from the shape-defined mesoporous TiO2microspheres and nanospindles presented superior performances, owing to the well-defined overall shapes and the inner ordered nanochannels, which allow not only a high amount of dye uptake, but also improved visible-light absorption. This study provides a new way to seek an optimal synthetic protocol to meet the required functionality of the nanomaterials.

Perovskite oxides remain a material class with properties that can be difficult to predict. Strong electron correlations, coupling between electron, lattice, spin and orbital degrees of freedoms, combined with the versatility of the structure itself, result in a wide range of properties, with unique emergent phenomena that occur only at heterointerfaces. Structure plays an especially important role in determining the properties of perovskite oxides. Small distortions in the lattice, particularly rotations or tilts of the oxygen octahedra, can have large effects on the material’s electrical and magnetic properties. One way we can tune these rotations is by growing thin film heterostructures, allowing us to tailor the properties of these materials in ways not possible in the bulk. Therefore, determining the local atomic structure in these films is critical for understanding the structure-property relationships, and the origin of any emergent behavior that may exist at an interface.To that end, we utilize scanning transmission electron microscopy (STEM) to develop a link between the atomic structure and electrical/magnetic properties of three different systems: SrTiO3 quantum wells between GdTiO3 and SmTiO3, GdTiO3 quantum wells between SrTiO3, and strained NdNiO3. Using real-space and diffraction techniques, we obtain quantitative information on local octahedral rotations and observe the presence/absence of structural transitions. This information gives us new insight into thedriving forces behind the metal-insulator transition and magnetic behavior of the different material systems. We also continue the development of quantitative STEM for precise and accurate determination of 3D dopant atom configurations by using variable detector angles in the high angle annular dark field regime. By demonstrating the usefulness of obtaining angle-resolved scattering data, we provide a new avenue for improving STEM image contrast and atom visibility for future studies.

This work reports on magnetocapacitance (MC) effects in epitaxial heterostructures of nominally 15 unit cells (u.c.) LaMnO(LMO) and 2 u.c. SrTiO(STO) with an alternating layer-repetition rate of 8: (LMO/STO). Epitaxial multilayer growth at high temperatures (900 °C) activates a selective inter-diffusion of Laand Srcations across the interfaces, which gives rise to Sr p-doping of the LMO and La n-doping of the STO layers. MC effects at the buried LaSrMnO/SrLaTiO(LSMO/SLTO) interfaces are probed by frequency, temperature and magnetic field dependent AC impedance spectroscopy. The technique is shown to be appropriate to account for the separate analysis of different resistance and capacitance contributions at the buried interfaces. As a result of the La/Sr inter-diffusion process, Schottky barriers are formed at the LSMO/SLTO interfaces, which give rise to massive MC of up to ≈ −200% in the out-of-plane film direction. The capacitance of the manganite-titanate LSMO/SLTO interfaces may be coupled indirectly to the resistance of the LSMO layers, because the Schottky space-charge layers and their capacitance can be modulated by varying the concentration of highly mobile charge carriers in the LSMO with a magnetic field.

This study proposes a direct synthetic route to single titanate sheets through the mild and versatile conditions of the >chimie douce>. The stages of the production include the complexation of the titanium alkoxide precursor by benzoic acid, the formation of titanium oxo-clusters and their controlled transformation into single sheet titanates during the hydrolysis stage. The resulted material appears to be an excellent precursor for self-organized TiO2 nanotubes formation which presents an excellent activity as photocatalyst in the photo-degradation of phenol

This study proposes a direct synthetic route to single titanate sheets through the mild and versatile conditions of the >chimie douce>. The stages of the production include the complexation of the titanium alkoxide precursor by benzoic acid, the formation of titanium oxo-clusters and their controlled transformation into single sheet titanates during the hydrolysis stage. The resulted material appears to be an excellent precursor for self-organized TiO2 nanotubes formation which presents an excellent activity as photocatalyst in the photo-degradation of phenol

This study proposes a direct synthetic route to single titanate sheets through the mild and versatile conditions of the >chimie douce>. The stages of the production include the complexation of the titanium alkoxide precursor by benzoic acid, the formation of titanium oxo-clusters and their controlled transformation into single sheet titanates during the hydrolysis stage. The resulted material appears to be an excellent precursor for self-organized TiO2 nanotubes formation which presents an excellent activity as photocatalyst in the photo-degradation of phenol

This study proposes a direct synthetic route to single titanate sheets through the mild and versatile conditions of the >chimie douce>. The stages of the production include the complexation of the titanium alkoxide precursor by benzoic acid, the formation of titanium oxo-clusters and their controlled transformation into single sheet titanates during the hydrolysis stage. The resulted material appears to be an excellent precursor for self-organized TiO2 nanotubes formation which presents an excellent activity as photocatalyst in the photo-degradation of phenol

This study proposes a direct synthetic route to single titanate sheets through the mild and versatile conditions of the >chimie douce>. The stages of the production include the complexation of the titanium alkoxide precursor by benzoic acid, the formation of titanium oxo-clusters and their controlled transformation into single sheet titanates during the hydrolysis stage. The resulted material appears to be an excellent precursor for self-organized TiO2 nanotubes formation which presents an excellent activity as photocatalyst in the photo-degradation of phenol

This study proposes a direct synthetic route to single titanate sheets through the mild and versatile conditions of the >chimie douce>. The stages of the production include the complexation of the titanium alkoxide precursor by benzoic acid, the formation of titanium oxo-clusters and their controlled transformation into single sheet titanates during the hydrolysis stage. The resulted material appears to be an excellent precursor for self-organized TiO2 nanotubes formation which presents an excellent activity as photocatalyst in the photo-degradation of phenol. © 2014 Elsevier B.V.

The US Army has an urgent need for robust, high-energy-density, lightweight energy storage devices, and the lithium (Li)-air battery is one promising solution due to its high-energy density and lower weight compared with Li-ion batteries. The ceramic electrolytic membrane is currently the bottleneck for successful implementation of Li-air batteries. The density of the electrolytic membrane material, Li0.35La0.57TiO3 (LLTO), must be optimized for LLTO to attain its maximum ionic conductivity because previous work done by the US Army Research Laboratory has demonstrated a relationship between density and conductivity in LLTO. The sintering behavior of LLTO requires comprehensive study to synthesize dense ceramics with high ionic conductivity. Therefore, the sintering temperature was varied from 1,100 C to 1,350 C, and the density of LLTO pellets was measured using 3 different techniques X-ray diffraction, optical microscopy, and scanning electron microscopy, which were also used to determine the phases, crystal structure, crystallite size, and microstructure of the sintered LLTO pellets. It was found that sintering at 1,200 C produced tetragonal LLTO ceramics with the highest density more than 95% of the theoretical density. Lower sintering temperatures yielded LLTO samples with lower densities and smaller crystallite sizes. Sintering at 1,300 C produced concave pellets with slight preferred crystallographic orientation., The original document contains color images. Prepared in collaboration with the Department of Chemistry, Rochester Institute of Technology, Rochester, NY.

Elastic modulus measurements were made using a three-point configuration testing method. Samples of barium strontium titanate (BST) were made using a regular powder pressing, sintering, pelletizing, and sawing method (pelletizing method), as well as a tape casting technique. Samples of aluminum oxide (alumina) were made by a tape casting method. For BST, a value of elastic modulus between 99 to 114 GPa was obtained for the pelletizing method and 161 GPa for the tape casting BST material. For the alumina, an average value of elastic modulus of 249 GPa was measured., The original document contains color images.

This research work has invented a novel general synthesis method for producing spatial doping of 1D titanium based nanotubes. For this, we divided our work in two phases. In the first phase of the work, we present general synthesis methods for producing Ti-based nanostuctures, more precisely nanotubes, and elucidate their formation mechanisms based on ex-situ microscopic analysis and in-situ spectroscopic analysis. Titanium based nanostructures are produced from different Ti-sources by using alkaline microwave hydrothermal irradiation techniques. There are number of factors that affect its nanostructure. Post-treatment washing is the main crucial step which effects Ti-nanotube structure and morphology, crystal size, textural properties and composition. In the second phase of this work, we present a new synthesis method to prepare metal and metal oxide doped on different spatial locations of the titania nanotubes (i.e. core, surface and interlayer spaces). The precursors are introduced by either in-situ or ex-situ techniques to the titania precursor materials. Dopants from the Group IB, IIB, IVB, V and VIII element including Ag, Au, Co, Cu, Pd, Pt and V and their oxides etc were successfully doped on the surface, in the core and within the interlayer spaces of the titania nanotubes. The location of the dopants was manipulated by controlling the affinity of the dopant precursor to the titania surface during the preparation. Precursor with low affinity will preferentially decorate the nanotube surface, whereas strong affinity will lead to metal being embedded between the interlayer spaces of the nanotube. Intermediate affinity allows core-filling to produce metal particles, slugs or nanowires within the core of the nanotubes. Microscopy and spectroscopy studies were carried out to investigate the structural, chemical and electronic properties of these new nanotube materials and explore their application for catalytic conversions, biomedical applications etc. To examine

This research work has invented a novel general synthesis method for producing spatial doping of 1D titanium based nanotubes. For this, we divided our work in two phases. In the first phase of the work, we present general synthesis methods for producing Ti-based nanostuctures, more precisely nanotubes, and elucidate their formation mechanisms based on ex-situ microscopic analysis and in-situ spectroscopic analysis. Titanium based nanostructures are produced from different Ti-sources by using alkaline microwave hydrothermal irradiation techniques. There are number of factors that affect its nanostructure. Post-treatment washing is the main crucial step which effects Ti-nanotube structure and morphology, crystal size, textural properties and composition. In the second phase of this work, we present a new synthesis method to prepare metal and metal oxide doped on different spatial locations of the titania nanotubes (i.e. core, surface and interlayer spaces). The precursors are introduced by either in-situ or ex-situ techniques to the titania precursor materials. Dopants from the Group IB, IIB, IVB, V and VIII element including Ag, Au, Co, Cu, Pd, Pt and V and their oxides etc were successfully doped on the surface, in the core and within the interlayer spaces of the titania nanotubes. The location of the dopants was manipulated by controlling the affinity of the dopant precursor to the titania surface during the preparation. Precursor with low affinity will preferentially decorate the nanotube surface, whereas strong affinity will lead to metal being embedded between the interlayer spaces of the nanotube. Intermediate affinity allows core-filling to produce metal particles, slugs or nanowires within the core of the nanotubes. Microscopy and spectroscopy studies were carried out to investigate the structural, chemical and electronic properties of these new nanotube materials and explore their application for catalytic conversions, biomedical applications etc. To examine

This research work has invented a novel general synthesis method for producing spatial doping of 1D titanium based nanotubes. For this, we divided our work in two phases. In the first phase of the work, we present general synthesis methods for producing Ti-based nanostuctures, more precisely nanotubes, and elucidate their formation mechanisms based on ex-situ microscopic analysis and in-situ spectroscopic analysis. Titanium based nanostructures are produced from different Ti-sources by using alkaline microwave hydrothermal irradiation techniques. There are number of factors that affect its nanostructure. Post-treatment washing is the main crucial step which effects Ti-nanotube structure and morphology, crystal size, textural properties and composition. In the second phase of this work, we present a new synthesis method to prepare metal and metal oxide doped on different spatial locations of the titania nanotubes (i.e. core, surface and interlayer spaces). The precursors are introduced by either in-situ or ex-situ techniques to the titania precursor materials. Dopants from the Group IB, IIB, IVB, V and VIII element including Ag, Au, Co, Cu, Pd, Pt and V and their oxides etc were successfully doped on the surface, in the core and within the interlayer spaces of the titania nanotubes. The location of the dopants was manipulated by controlling the affinity of the dopant precursor to the titania surface during the preparation. Precursor with low affinity will preferentially decorate the nanotube surface, whereas strong affinity will lead to metal being embedded between the interlayer spaces of the nanotube. Intermediate affinity allows core-filling to produce metal particles, slugs or nanowires within the core of the nanotubes. Microscopy and spectroscopy studies were carried out to investigate the structural, chemical and electronic properties of these new nanotube materials and explore their application for catalytic conversions, biomedical applications etc. To examine

In this article the influence of ball miling process on structure of MgO–TiO2 system, as well as the electrical properties of samples after sintering, was investigated. The mixtures of MgO–TiO2 powders were mechanically activated in a planetary ball mill for the time period from 0 to 120 min. The influence of mechanical activation and sintering on the lattice vibrational spectra was studied by Raman spectroscopy at room temperature. Structural investigations have been performed on produced powders. Nitrogen adsorption method was used to determine the BET specific surface area and pore size distribution. Unusual results have been obtained: specific surface area continuously decreased up to 40 min of activation and increased after that, reaching its minimum value of 5.5 m2/g. The Raman spectra of activated powders have shown that anatase modes have been decreasing in intensity and broadening as the time of activation extended. Also, the additional modes attributed to TiO2 II, srilankite and rutile phases started to appear as a consequence of activation. The small differences noticed in the Raman spectra of sintered samples have been explained by structural modification of MgTiO3 phase due to the presence of defects. The effects of activation and sintering process on microstructure were investigated by scanning electron microscopy (SEM). The electrical measurements showed difference in dielectric constant (εr), loss tangent (tg δ) and specific resistance (ρ) as a function of time of mechanical treatment.

A spatial non-uniformity of the switching properties during the fatigue cycling in lead zirconate titanate ceramics was investigated by a quasi-static piezoelectric and a polarization switching measurements. The agreement between the local piezoelectric properties and the switching behavior of segmented samples was demonstrated. The observed spatial variation of the properties and its evolution with cycle number provides clear evidence of the presence of heterogeneous regions that possess a local fatigue state and the local switching behavior. These results can be explained as a result of the build-up of the spatially non-uniform field and the formation of frozen domains in the ceramics during cycling. The statistical analysis of spatial variation of the switching properties and its evolution with cycle number provides the evidence that the heterogeneity of the switching properties during the fatigue cycling in lead zirconate titanate ceramics is mostly related to the non-uniform change of the local characteristic switching time. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Anatase TiO2 nanocrystals were painted on H-titanate nanofibers by using an aqueous solution of titanyl sulfate. The anatase nanocrystals were bonded solidly onto the titanate fibers through formation of coherent interfaces at which the oxygen atoms were shared by the nanocrystals and the fiber. This approach allowed us to create large anatase surfaces on the nanofibers, which are active in photocatalytic reactions. This method was also applied successfully to coat anatase nanocrystals on surfaces of fly ash and layered clay. The painted nanofibers exhibited a much higher catalytic activity for the photocatalytic degradation of sulforhodamine B and the selective oxidation of benzylamine to the corresponding imine (with a product selectivity >99%) under UV irradiation than both the parent H-titanate nanofibers and a commercial TiO2 powder, P25. We found that gold nanoparticles supported on H-titanate nanofibers showed no catalytic activity for the reduction of nitrobenzene to azoxybenzene, whereas the gold nanoparticles supported on the painted nanofibers and P25 could efficiently reduce nitrobenzene to azoxybenzene as the sole product under visible light irradiation. These results were different from those from the reduction on the gold nanoparticles photocatalyst on ZrO2, in which the azoxybenzene was the intermediate and converted to azobenzene quickly. Evidently, the support materials significantly affect the product selectivity of the nitrobenzene reduction. Finally, the new photocatalysts could be easily dispersed into and separated from a liquid because of their fibril morphology, which is an important advantage for practical applications.

Cerium ions (Ce3+) can beselectively doped into the TiO2(B) core of TiO2(B)/anatase core–shell nanofibers by means of a simple one-pot hydrothermal treatment of a starting material of hydrogen trititanate (H2Ti3O7) nanofibers. These Ce3+ ions (≈0.202 nm) are located on the (110) lattice planes of the TiO2(B) core in tunnels (width≈0.297 nm). The introduction of Ce3+ ions reduces the defects of the TiO2(B) core by inhibiting the faster growth of (110) lattice planes. More importantly, the redox potential of the Ce3+/Ce4+ couple (E0(Ce3+/Ce4+)=1.715 V versus the normal hydrogen electrode) is more negative than the valence band of TiO2(B). Therefore, once the Ce3+-doped nanofibers are irradiated by UV light, the doped Ce3+ ions in close vicinity to the interface between the TiO2(B) core and anatase nanoshell can efficiently trap the photogenerated holes. This facilitates the migration of holes from the anatase shell and leaves more photogenerated electrons in the anatase nanoshell, which results in a highly efficient separation of photogenerated charges in the anatase nanoshell. Hence, this enhanced charge-separation mechanism accelerates dye degradation and alcohol oxidation processes. The one-pot treatment doping strategy is also used to selectively dope other metal ions with variable oxidation states such as Co2+/3+ and Cu+/2+ ions. The doping substantially improves the photocatalytic activity of the mixed-phase nanofibers. In contrast, the doping of ions with an invariable oxidation state, such as Zn2+, Ca2+, or Mg2+, does not enhance the photoactivity of the mixed-phase nanofibers as the ions could not trap the photogenerated holes.

A spatial non-uniformity of the switching properties during the fatigue cycling in lead zirconate titanate ceramics was investigated by a quasi-static piezoelectric and a polarization switching measurements. The agreement between the local piezoelectric properties and the switching behavior of segmented samples was demonstrated. The observed spatial variation of the properties and its evolution with cycle number provides clear evidence of the presence of heterogeneous regions that possess a local fatigue state and the local switching behavior. These results can be explained as a result of the build-up of the spatially non-uniform field and the formation of frozen domains in the ceramics during cycling. The statistical analysis of spatial variation of the switching properties and its evolution with cycle number provides the evidence that the heterogeneity of the switching properties during the fatigue cycling in lead zirconate titanate ceramics is mostly related to the non-uniform change of the local characteristic switching time. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In this article the influence of ball miling process on structure of MgO-TiO2 system, as well as the electrical properties of samples after sintering, was investigated. The mixtures of MgO-TiO2 powders were mechanically activated in a planetary ball mill for the time period from 0 to 120 min. The influence of mechanical activation and sintering on the lattice vibrational spectra was studied by Raman spectroscopy at room temperature. Structural investigations have been performed on produced powders. Nitrogen adsorption method was used to determine the BET specific surface area and pore size distribution. Unusual results have been obtained: specific surface area continuosly decreased up to 40 min of activation and increased after that, reaching its minimun value of 5.5 m(2)/g. The Raman spectra of activated powders have shown that anatase modes have been decreasing in intensity and broadening as the time of activation extended. Also, the additional modes attributed to TiO2 II, srilankite and rutile phases started to appear as a consequence of activation. The small differences noticed in the Raman spectra of sintered samples have been explained by structural modification of MgTiO3 phase due to the presence of defects. The effects of activation and sintering process on microstructure were investigated by scanning electron microscopy (SEM). The electrical measurements showed difference in dielectric constant (epsilon(r)), loss tangent (tg delta) and specific resistance (rho) as a function of time of mechanical treatment.

Titania nanotubes (TNT) have gained increasing interest due to their high surface area, fewer interfacial grain boundaries and excellent charge transfer between interfaces; all are critical properties in photoelectrochemical and photocatalysis application. In this study, TNT thin film electrodes were synthesized by electrochemical anodisation of pure Ti in a standard two-electrode cell containing NH4F solution. Parameters affecting the morphological, structural and geometry of TNT were investigated in three different electrolytic medium namely the acidic aqueous solution (NH4F/H2O), mixture of aqueous-organic solution (NH4F/H2O/EG) and an organic neutral solution (NH4F/EG). The characteristic of TNT were analyzed using Field Emission Scanning Electron Microscopy (FESEM), X-ray Diffractometry (XRD), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Analysis (EDX) and UV Visible Diffuse Reflectance Spectroscopy (UV-DRS). Meanwhile, the photoelectrochemical responses of TNT were investigated using Liner Sweep Photovoltammetry (LSPV) and their photoefficiency was evaluated in 0.1 M KOH under UV illumination. The thermal stability of short TNT (400 nm in length) and its morphological, structural, optical and photoelectrochemical changes as a result of heat treatment at 200-800 oC were also studied. In NH4F/H2O electrolyte, sample morphology was affected by electrolyte pH and fluoride concentration whereby nanotubes dimensions and their growth rate can be manipulated via anodisation voltage, bath temperature, anodisation duration and the addition of EDTA. Voltage range and NH4F concentration used for TNT formation varied depending on the electrolytic medium used during anodisation. Higher voltage range could be used in NH4F/EG to obtain larger diameter and longer length tube. An optimum fluoride concentration is required to achieve well-defined and long tube as higher amount of F- leads to faster chemical dissolution. Choice of electrolytic medium also has a

In this article the influence of ball miling process on structure of MgO-TiO2 system, as well as the electrical properties of samples after sintering, was investigated. The mixtures of MgO-TiO2 powders were mechanically activated in a planetary ball mill for the time period from 0 to 120 min. The influence of mechanical activation and sintering on the lattice vibrational spectra was studied by Raman spectroscopy at room temperature. Structural investigations have been performed on produced powders. Nitrogen adsorption method was used to determine the BET specific surface area and pore size distribution. Unusual results have been obtained: specific surface area continuosly decreased up to 40 min of activation and increased after that, reaching its minimun value of 5.5 m(2)/g. The Raman spectra of activated powders have shown that anatase modes have been decreasing in intensity and broadening as the time of activation extended. Also, the additional modes attributed to TiO2 II, srilankite and rutile phases started to appear as a consequence of activation. The small differences noticed in the Raman spectra of sintered samples have been explained by structural modification of MgTiO3 phase due to the presence of defects. The effects of activation and sintering process on microstructure were investigated by scanning electron microscopy (SEM). The electrical measurements showed difference in dielectric constant (epsilon(r)), loss tangent (tg delta) and specific resistance (rho) as a function of time of mechanical treatment.

In this article the influence of ball miling process on structure of MgO-TiO2 system, as well as the electrical properties of samples after sintering, was investigated. The mixtures of MgO-TiO2 powders were mechanically activated in a planetary ball mill for the time period from 0 to 120 min. The influence of mechanical activation and sintering on the lattice vibrational spectra was studied by Raman spectroscopy at room temperature. Structural investigations have been performed on produced powders. Nitrogen adsorption method was used to determine the BET specific surface area and pore size distribution. Unusual results have been obtained: specific surface area continuosly decreased up to 40 min of activation and increased after that, reaching its minimun value of 5.5 m(2)/g. The Raman spectra of activated powders have shown that anatase modes have been decreasing in intensity and broadening as the time of activation extended. Also, the additional modes attributed to TiO2 II, srilankite and rutile phases started to appear as a consequence of activation. The small differences noticed in the Raman spectra of sintered samples have been explained by structural modification of MgTiO3 phase due to the presence of defects. The effects of activation and sintering process on microstructure were investigated by scanning electron microscopy (SEM). The electrical measurements showed difference in dielectric constant (epsilon(r)), loss tangent (tg delta) and specific resistance (rho) as a function of time of mechanical treatment.

Titania nanotubes (TNT) have gained increasing interest due to their high surface area, fewer interfacial grain boundaries and excellent charge transfer between interfaces; all are critical properties in photoelectrochemical and photocatalysis application. In this study, TNT thin film electrodes were synthesized by electrochemical anodisation of pure Ti in a standard two-electrode cell containing NH4F solution. Parameters affecting the morphological, structural and geometry of TNT were investigated in three different electrolytic medium namely the acidic aqueous solution (NH4F/H2O), mixture of aqueous-organic solution (NH4F/H2O/EG) and an organic neutral solution (NH4F/EG). The characteristic of TNT were analyzed using Field Emission Scanning Electron Microscopy (FESEM), X-ray Diffractometry (XRD), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Analysis (EDX) and UV Visible Diffuse Reflectance Spectroscopy (UV-DRS). Meanwhile, the photoelectrochemical responses of TNT were investigated using Liner Sweep Photovoltammetry (LSPV) and their photoefficiency was evaluated in 0.1 M KOH under UV illumination. The thermal stability of short TNT (400 nm in length) and its morphological, structural, optical and photoelectrochemical changes as a result of heat treatment at 200-800 oC were also studied. In NH4F/H2O electrolyte, sample morphology was affected by electrolyte pH and fluoride concentration whereby nanotubes dimensions and their growth rate can be manipulated via anodisation voltage, bath temperature, anodisation duration and the addition of EDTA. Voltage range and NH4F concentration used for TNT formation varied depending on the electrolytic medium used during anodisation. Higher voltage range could be used in NH4F/EG to obtain larger diameter and longer length tube. An optimum fluoride concentration is required to achieve well-defined and long tube as higher amount of F- leads to faster chemical dissolution. Choice of electrolytic medium also has a

The first (Part I.) is Developing Sensitive and Selective Nanosensors. The partnership of Altairnano, Inc. and Western Michigan University produced one compound which could be used to identify nerve gas analogs selectively in the presence of fuel-based interference compounds. This research developed the framework for a developed the framework for a prototype sensor which can be easily augmented to demonstrate function based on sensing requirments. The research described in the final report consists of sensor selection, sample preparation, library development and analysis, and prototype development. The second (Part II.) is Altairnano Lithium Ion Nano-scaled Titanate Oxide Cell and Module Abuse Test Report. The partnership of Altairnano, Inc. and the Naval Surface Warfare Center in Crane, Indiana produced a set of abuse test results which could be used to evaluate the use of Altairnano's lithium ion cells in US Army applications such as the M119/105mm Gun batteries. The abuse testing focused on exposure to extreme heat and flame, on the analysis of gases released due to exposure, and on fire suppression methods., The original document contains color images.

This work presents a study of the domain wall dynamics in Pb(Zr1−xTix)O3 (PZT)-based piezoceramics by means of the temperature dependence non-linear dielectric response and hysteresis loop measurements. In soft PZT, non-linear response gradually increases as the temperature is raised. A similar response is displayed by hard PZT at low temperatures. However, rather more complex behavior is detected at temperatures above 200 K. The anomalous response, which is very marked at room temperature, becomes even greater when the electric field is increased. The non-linear dielectric response is analyzed in the framework of the Rayleigh model. The results suggest a clear change in the domain wall dynamics in hard PZT, which is not observed in soft PZT. Observation of the hysteresis loops confirms that a strong effect of domain wall pinning emerges near room temperature. The change in domain wall dynamics appears as the main cause of the dielectric response difference between both kinds of materials at room temperature, Postprint (published version)

Seminarvortrag zu: - Switching – Electrostatic field at interfaces - Strontium Titanate & Defects - Aluminium Oxide Boundaries - Quantification by DFT – EELS – HRTEM

The determination of the characteristic frequencies of an electromechanical resonance is not enough data to obtain material properties of piezoceramics, including all losses, from complex impedance measurements. Besides, values of impedance around resonance and antiresonance frequencies are also required to determine the material losses. Uncoupled resonances are needed for this purpose. The shear plates used for the material characterization present unavoidable mode coupling of the shear mode and other modes of the plate. A study of the evolution of the complex material coefficients as the coupling of modes evolves with the change in the aspect ratio (lateral dimension/thickness) of the plate is presented here. These are obtained by Alemany et al. software. A soft commercial PZT ceramic was used in this study and a number of shear plates amenable to material characterization were obtained in the range of aspect ratios below 15. The validity of the material properties for 3-D modelling of piezoceramics is assessed by means of Finite Element Analysis (FEA), which shows that uncoupled resonances are virtually pure thickness driven shear modes.

Potassium-rich titanate nanofibers were produced by digesting TiO2 in concentrated KOH solutions under hydrothermal conditions. The nanofibers were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and thermogravimetric analysis. A hexatitanatestructure was assigned, in contrast to the trititanate structure usually resulting from NaOH treatment of TiO2. The potassium cations could be exchanged with others, such as sodium, hydrogen, and ammonium. The potassium-rich hexatitanate was found to be photocatalytic in its as-synthesized condition. The thermal stability of the fibers during calcination was followed in situ using X-ray diffraction and was found to be strongly dependent on the chemical composition. The potassium-rich titanate converted to anatase at only 480 °C, whereas the hydrogen- and ammonium-rich materials had to be heated to over 600 °C before conversion took place. Conversion was notably slowest in the ammoniumrich material. Surprisingly, the sodium-rich hexatitanate did not form anatase at temperatures up to 800 °C and insteadrecrystallized.

High-Performance, High-Power-Density Solid Oxide Fuel Cells: Materials - Solid oxide fuel cell electrodes based on catalyst coatings offer substantial potential for creating more effective anode and cathode structures. Infiltrated anodes based on nickel metal can yield finer catalyst phase distribution at volumetric concentrations well below percolation for traditional cermets. The coarsening of nickel after high temperature thermal treatment poses substantial degradation to the deposited structure; therefore, methods of anchoring the nickel metal to the YSZ scaffold have been evaluated to stabilize fine scale electro-catalyst particles. Aluminum titanate was introduced into the porous YSZ anode scaffold to facilitate a step-wise chemical reaction to anchor the nickel metal catalyst. SEM observation of thermally treated nickel infiltrated scaffolds indicates excellent preservation of the nickel network at 800 degrees C for 100 hours. Electrochemical tests show not only decreased degradation rates, but also increased initial performance levels due to the additive. High Performance, High-Power-Density Solid Oxide Fuel Cells: Load Control - With currently foreseeable technology, a fuel cell stack capable of supplying the dynamic power requirements for turns, climb, and sprint maneuvers is so heavy as to negate the advantage of using a fuel cell in level flight. This essentially requires the hybridization of the fuel cell using a zero-average power source such as a battery or capacitor. In this report, we discuss the development of an extremely simple hybrid controller that combines the current/voltage characteristics of a battery and fuel cell. This controller could be readily adapted to current fuel cell powered vehicles., Performed in cooperation with Universal Technology Corporation, Dayton, OH.

When grown on miscut SrTiO3 substrates, significant microstructural changes are observed in BaZrO3-doped YBa2Cu3O7-x thin films when compared to those on non-vicinal substrates. Scanning Electron Microscopy indicates a surface morphology strongly influenced by the vicinal angle, and an accumulation of BaZrO3 particles is observed near the step edges. Cross-sectional Transmission Electron Microscopy reveals that while the columnar formations of BaZrO3 rods typically seen on non-vicinal substrates are present, a significant increase in planar defects in a 10 vicinal film are observed. The effects observed with increasing miscut angle indicate that the modulated surface provided by the vicinal substrate influences the crystalline quality of the YBCO matrix and BZO columnar formation through the thickness of the film., Published in IEEE Transactions on Applied Superconductivity, v19 n3 p3371-3374, June 2009.

Metal oxide semiconductor field-effect transistors, formed using silicon dioxide and silicon, have undergone four decades of staggering technological advancement. With fundamental limits to this technology close at hand, alternatives to silicon dioxide are being pursued to enable new functionality and device architectures. We achieved ferroelectric functionality in intimate contact with silicon by growing coherently strained strontium titanate (SrTiO3) films via oxide molecular beam epitaxy in direct contact with silicon, with no interfacial silicon dioxide. We observed ferroelectricity in these ultrathin SrTiO3 layers by means of piezoresponse force microscopy. Stable ferroelectric nanodomains created in SrTiO3 were observed at temperatures as high as 400 kelvin., Published in the Journal of Science, v324 p367-370, 17 April 2009.

The most important aim in the design and processing of functionally graded materials (FGMs) is to produce devices free from any deformation. Smart choices of different combination of graded layers, as well as the heating rate during sintering, are important for the fabrication of high-quality FGMs. In this study, BaTi0.975Sn0.025O3/BaTi0.85S n0.15O3 (noted as BTS2.5 and BTS15, respectively) FGM was used as a model system for the construction of master sintering curves (MSCs) and estimation of the effective activation energies of sintering for different BTS graded layers. The MSCs were constructed, for BTS2.5 and BTS15 graded layers in FGMs, using shrinkage data obtained by a heating microscope during sintering at four constant heating rates, 2, 5, 10 and 20 °/min. The effective activation energies were determined using the concept of MSC; values of 359.5 and 340.5 kJ/mol were obtained for graded layers BTS2.5 and BTS15, respectively. A small difference of the effective activation energies of chosen powders made it possible for us to prepare high-quality FGMs, without delamination, distortion or other forms of defects. © 2009 Elsevier Ltd. All rights reserved.

The most important aim in the design and processing of functionally graded materials (FGMs) is to produce devices free from any deformation. Smart choices of different combination of graded layers, as well as the heating rate during sintering, are important for the fabrication of high-quality FGMs. In this study, BaTi0.975Sn0.025O3/BaTi0.85S n0.15O3 (noted as BTS2.5 and BTS15, respectively) FGM was used as a model system for the construction of master sintering curves (MSCs) and estimation of the effective activation energies of sintering for different BTS graded layers. The MSCs were constructed, for BTS2.5 and BTS15 graded layers in FGMs, using shrinkage data obtained by a heating microscope during sintering at four constant heating rates, 2, 5, 10 and 20 °/min. The effective activation energies were determined using the concept of MSC; values of 359.5 and 340.5 kJ/mol were obtained for graded layers BTS2.5 and BTS15, respectively. A small difference of the effective activation energies of chosen powders made it possible for us to prepare high-quality FGMs, without delamination, distortion or other forms of defects. © 2009 Elsevier Ltd. All rights reserved.

The aim of the present work is to explore the possibility of incorporate a small amount of ZnO to improve the microstructure control of W-doped BIT based materials. Two different processing routes have been used according to previous results reported for other materials: reaction and sintering in one single step and a previous calcination step. The sintering behaviour of the samples, the obtained crystalline phases and the microstructure analysis indicate that the reaction between ZnO and Bi2O3 plays a critical role during sintering. Both Bi2Ti2O7 and Zn2TiO4 secondary phases are stabilised when adding ZnO. Actually, when WO3 and ZnO are incorporated simultaneously to BIT materials, they interact stabilizing the Bi2Ti2O7 phase and avoiding the incorporation of W6+ into the BIT lattice. As a consequence, the electrical conductivity of the samples with ZnO is two orders of magnitude higher than that of the samples doped only with WO3, suggesting that WO3 does not form a solid solution with BIT. The curve dielectric constant vs temperature also reveals the role played by the Bi2Ti2O7 phase.

High Performance, High Power Density Solid Oxide Fuel Cells: Materials: The current geometry and materials set of the state-of-the-art anode supported cell (ASC) yields several deficiencies that limit the performance and robustness of the cell/stack under demanding aero based operational requirements. These deficiencies are embodied in poor gas transport through mechanically strong anodes, the limited use of cerium oxide in the anode due to unfavorable thermal expansion, and the poor thermal stability of ultra fine nickel catalyst under higher temperature operation for maximum output. These deficiencies are being addressed with the development of engineered porous substrates, additives to tailor thermal expansion in ceria based anode systems, and methods for complete infiltration of anode catalysts. Novel ceramic anodes were synthesized and fabricated at Montana State University and characterized through electron microscopy, dilatometry, thermal gravimetry, x-ray diffraction, and electrochemical testing. Modified processing techniques have generated a means for preparing controlled pore morphologies over large areas by freeze casting suitable for anode supported cell fabrication. The use of aluminum titanate additives has demonstrated a 30% decrease in thermal expansion in nickel/ceria anodes and the addition of aluminum titanate to nickel/zirconia porous scaffolds has shown to limit nickel coarsening from high temperature exposure. This report provides a physically-based model for design and optimization of a fuel cell powered electric propulsion system for an unmanned aerial vehicle. Components of the system include a solid oxide fuel cell providing power, motor controller, brushless DC motor, and a propeller. The simulation allows an operator to select constraints and explore design trade-offs between components, including fuel cell, controller, motor, and propeller options., The original document contains color images. All DTIC reproductions will be in black and white. Prepared in cooperation with Universal Technology Corp., Dayton, OH.