Torsten Markus

Interdiffusion in ternary Fe–Cr –Al alloys with variable molar volume

Abstract For interdiffusion profiles obtained at 1000ºC in the Fe-rich corner of the ternary system Fe –Cr – Al the evaluation of these profiles with the method proposed by Dayananda and Sohn in 1999 has been performed. Further, an alternative mathematical model is presented which directly yields element mobilities and Kirkendall velocities from experiments if the Gibbs free energy of the system is given as a function of composition, temperature and pressure. Computer simulations show that, interestingly enough, already fairly weak deviations from (thermodynamic) ideality will lead to pronounced up-hill diffusion effects for the majority component, i.e. Fe.

Long-term Testing and Analysis of a ScSZ / LaSrCuFe Cell

An electrolyte supported SOFC cell was tested at 800℃ in air for 3600 h with an applied current density of 200 mA/㎠ to examine possible cathode degradation issues. A scandium- stabilized zirconia (ScSZ) with additional manganese doping (ScSZ: Mn) was used as electrolyte. A strontium and copper-doped lanthanum ferrite (LaSrCuFe) and platinum were used as cathode and quasi-anode material, respectively. The DC resistance was logged over the complete testing period. Additionally, impedance spectroscopy was used from time to time to track changes of the cell in-situ. Post-test analysis of the cell using methods like scanning electron microscopy imaging and other electrochemical testing methods allow the identification of different degradation sources. The results indicate a promising combination of electrolyte and cathode material in terms of chemical compatibility and electrical performance.

Interlaboratory study of the heat capacity of LiNi1/3Mn1/3Co1/3O2 (NMC111) with layered structure

Abstract An interlaboratory study was performed to determine the heat capacity of an active material for lithium-ion batteries with layered structure and nominal composition LiNi1/3 · Mn1/3Co1/3O2 (NMC111). The commercial sample, which was characterized using powder X-ray diffraction and inductively coupled plasma–optical emission spectroscopy, is single phase (α-NaFeO2 crystal structure) with a composition of Li1.02Ni0.32Mn0.31Co0.30O2. Heat capacity measurements of the homogeneous sample were performed at five laboratories using different operators, methods, devices, temperature ranges, gas atmospheres and crucible materials. The experimental procedures from each laboratory are presented and the results of the individual laboratories are analyzed. Based on a comprehensive evaluation of the data from each laboratory, the heat capacity of the NMC111 sample from 315 K to 1 020 K is obtained with an expanded reproducibility uncertainty of less than 1.22 %.

Influence of the Ba2+/Sr2+ content and oxygen vacancies on the stability of cubic Ba(x)Sr(1-x)Co(0.75)Fe(0.25)O(3-δ).

We present a theoretical and experimental study on the influence of the Ba/Sr and Co/Fe ratios as well as the oxygen-non-stoichiometry on the stability of Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF). Thin-layer depositions are analysed by looking at TEM images and EDX spectra. Bond-analytical calculations are performed to explain the stability difference between hexagonal and cubic BSCF. Finally, annealing experiments analysed using XRD give an insight into the differences of phase-fraction growth with respect to the Ba/Sr ratio.

Preparation and Electrical Conductivity of Scandia Stabilized Zirconia by using Ultrasonic Spray Pyrolysis

Scandia stabilized zirconia (ScSZ) is adapted for electrolyte material of solid oxide fuel cell (SOFC) because of its high ionic conductivity and chemical stability. ScmnSZ1 powder having a composition of ((ZrO₂) 0.89 (Sc₂O₃) 0.1 MnO₂) 0.01 ) is synthesized by ultrasonic spray pyrolysis (USP) method. Porous ScmnSZ1 powder is obtained by using a pore forming agent. Microstructure and morphology, particle size distribution of porous powder synthesized with ₃ wt% pore forming agent are investigated. Sintered ScmnSZ1 sample with ground fine powder are also investigated their microstructure and electrical conductivity. The electrical conductivity of sintered ScmnSZ1 samples with ground fine powder was 0.082 S/㎝, 0.127 S/㎝ and 0.249 S/㎝ at 750℃, 800℃ and 900℃, respectively.