Novel multicomponent equiatomic pyrochlores for future thermal barrier coatings

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Kupfer- und Eisenoxide als Konversions-Elektrodenmaterialien für Lithium-Ionen-Batterien: Thermodynamische und Elektrochemische Untersuchungen

Konversionselektroden sind vielversprechende Elektrodenmaterialien für zukünftige Lithium-Ionen-Batterien, da sie sehr hohe spezifische Kapazitäten im Vergleich zu Interkalationselektroden aufweisen. In dieser Arbeit wird ein thermodynamischer Ansatz gewählt, um den elektrochemischen Prozess anhand der Modell-Systeme Li-Cu-O und Li-Fe-O zu beleuchten. Mit konsistenten thermodynamischen Beschreibungen können charakteristische elektrochemische Eigenschaften berechnet werden

Kupfer- und Eisenoxide als Konversions-Elektrodenmaterialien für Lithium-Ionen-Batterien: Thermodynamische und Elektrochemische Untersuchungen

Konversionselektroden sind vielversprechende Elektrodenmaterialien für zukünftige Lithium-Ionen-Batterien, da sie sehr hohe spezifische Kapazitäten im Vergleich zu Interkalationselektroden aufweisen. In dieser Arbeit wird ein thermodynamischer Ansatz gewählt, um den elektrochemischen Prozess von Konversions-Elektroden anhand der Modell-Systeme Li-Cu-O und Li-Fe-O zu beleuchten. Mit den konsistenten thermodynamischen Beschreibungen können elektrochemische Eigenschaften berechnet werden

Investigation of the oxidation resistance of ZrB2-based monoliths using polymer-derived Si(Zr,B)CN as sintering aid

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Synthesis, structure and electrical conductivity of a new perovskite type barium cobaltate BaCoO1.80(OH)0.86

Perovskite oxides exhibiting mixed protonic and electronic conductivities have interesting applications in protonic ceramic fuel cells. In this work, we report on a hydrated phase of BaCoO1.80(OH)0.86 synthesized using nebulized spray pyrolysis. Structural analysis based on X-ray and neutron powder diffraction data showed that the compound is isotypic to BaFeO2.33(OH)0.33. The water loss behaviour was studied using simultaneous thermal analysis and high temperature X-ray diffraction, indicating that protons (respectively water) can be stabilized within the compound up to temperatures significantly above 673 K, confirmed by ex situ Fourier transform infrared spectroscopy studies. Impedance spectroscopy was used to determine the conductivity characteristics of BaCoO1.80(OH)0.86, finding and a total electrical conductivity in the order of 10−4 S cm−1 at ambient temperature with an activation energy of 0.28 eV

CrB-type, ordered α -MnB: Single crystal structure and spin-canted magnetic behavior

Manganese monoboride has a low- (α) and a high-temperature (β) modification, as well as a defect-rich low-temperature variant (α′). The crystal structure (FeB-type structure, s.g. Pnma) and properties of high-temperature MnB are well-known. In this work, single crystals were grown via chemical vapor transport reactions, both of β-MnB and the low-temperature modification, α-MnB. This allowed for determining the crystal structure of defect-free α-MnB [CrB-type structure, s.g. Cmcm, a = 3.0098(6) Å, b = 7.6390(2) Å, and c = 2.94620(6) Å]. Furthermore, α′-MnB, the stacking fault-dominated CrB-variant, was obtained as crystalline powder and characterized by X-ray powder diffraction and transmission electron microscopy. Direction-resolved measurements of the magnetic properties of α-MnB revealed spin-canted magnetic behavior along c and ferromagnetism along a and b with a Curie temperature of 456 K; ferromagnetic β-MnB has a Curie temperature of 568 K

Oxidation resistance of ZrB₂‐based monoliths using polymer‐derived Si(Zr,B)CN as sintering aid

The focus of the present work is the investigation of the influence of polymer‐derived ceramics, used as sintering aids for preparing ZrB₂‐based monoliths, on their high‐temperature oxidation behavior. For the preparation of the monoliths, ZrB₂ powder was coated with polymer‐derived SiCN, SiZrCN, or SiZrBCN and subsequently densified via hot‐pressing at temperatures as low as 1800°C. To investigate the oxidation kinetics, thermogravimetric analysis (TGA) was performed at 1300°C in synthetic air with exposure times of 50 and 100 h. A detailed study of the materials oxide scale and subsurface microstructure was conducted using optical microscopy, electron probe microanalysis, scanning electron microscopy, and X‐ray diffraction. The experimental findings were compared to thermodynamic equilibrium calculations using the CALPHAD method, which led to a better understanding of the oxidation mechanism. In comparison to the literature data of ZrB₂–SiC, the results show improved oxidation resistance for all three investigated materials. The formation of gaseous species during oxidation, in particular CO, CO₂, B₂O₃, and SiO, within the oxide scale of the monoliths was rationalized via CALPHAD calculations and used to explain the oxidation behavior and kinetics and also the formation of bubbles in the subsurface region of the oxidized specimens

Kupfer- und Eisenoxide als Konversions-Elektrodenmaterialien für Lithium-Ionen-Batterien: Thermodynamische und Elektrochemische Untersuchungen

Conversion-type electrodes are promising electrode materials for future lithium ion batteries since they exhibit high specific capacities compared to intercalation-type eclectrodes. In this work, a thermodynamic approach was used to elucidate the electrochemical behavior of conversion-type electrodes using Li-Cu-O and Li-Fe-O as model material systems. electrochemical properties can be calculated using self-sonstistent thermodynamic descriptions developed in this work