Fuegetechniken fuer hochbelastbare oxidkeramische Geraete- und Apparatebauteile. Teilprojekt Heraeus: Elektrodenherstellung Abschlussbericht

The present subproject aimed on the improvement of the junction between platinum and ZrO_2-doped alumina in high-level service Pt electrodes for magnetic-inductive flowmeters. Five different approaches have been studied: 1. application of massive Pt metal or PtIr10 alloy; 2. coating of ceramical bodies with platinum containing ceramical dyes; 3. impregnation of ceramical bodies with hexachloro platinum acid; 4. application of Pt/oxide-ceramical composites with ceramics as the matrix, and 5. application of Pt/oxide-ceramical composites with platinum as the matrix. Only by method (5.) conductive cermet electrodes of high temperature resistance (1720 C) could be reproducibly obtained using a powder metallurgically prepared Pt-Al_2O_3 mixture. Parallel studies on the Pt-Zr-O system revealed the formation of an Haegg phase: the solubility of oxygen in Zr-doped Pt increases with increasing Zr content on account of the Pt host lattice expansion due to Zr substitution. (WEN)SIGLEAvailable from TIB Hannover: F96B75+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman

Collective Excitation in Silver Cluster Anions and Kations

Positive and negative silver cluster ions are produced by sputtering of solid silver by 25 keV Xe+ bombaxdment. After mass selection, collinear ion beam depletion is used to measure absolute photofragmentation cross-sections in the photon energy range from ħω = 2.0 to 5.7 eV. Giant resonances are found which can be interpreted in terms of a collective electron oscillation. For spherical clusters (e.g., Ag19−, Ag21+) single resonances dominate the spectra, whereas deformation (e.g., Ag9−, Ag11+) induces a splitting into two components

Collective Excitation in Silver Cluster Anions and Kations

Positive and negative silver cluster ions are produced by sputtering of solid silver by 25 keV Xe+ bombaxdment. After mass selection, collinear ion beam depletion is used to measure absolute photofragmentation cross-sections in the photon energy range from ħω = 2.0 to 5.7 eV. Giant resonances are found which can be interpreted in terms of a collective electron oscillation. For spherical clusters (e.g., Ag19−, Ag21+) single resonances dominate the spectra, whereas deformation (e.g., Ag9−, Ag11+) induces a splitting into two components

Structural periodicity in laser additive manufactured Zr-based bulk metallic glass

Additive manufacturing of bulk metallic glasses (BMGs) allows for effective bypassing of critical casting thickness constraints for glassy alloys, opening up this exciting material class to new applications. An open question is how the laser processing of such materials affects the short-range structural order, a critical mediating parameter for glass deformation. Synchrotron X-ray microdiffraction was used to understand structural heterogeneity across the build-planes of a selective laser melted Zr-based BMG. While negligible macroscopic heterogeneity in the structure was observed over a 10 mm build height for the X-ray amorphous material, small periodic variations were observed on the order of 40-80 μm. This dimensional scale was rationalized as a consequence of melt-pool solidification from laser processing, which imparts a calculated local strain variation of ±0.1%. It is anticipated that this structural insight will help to rationalize microscale deformation effects from the periodic structural variation of selective laser melting produced BMGs

Structural periodicity in laser additive manufactured Zr-based bulk metallic glass

Additive manufacturing of bulk metallic glasses (BMGs) allows for effective bypassing of critical casting thickness constraints for glassyalloys, opening up this exciting material class to new applications. An open question is how the laser processing of such materials affects theshort-range structural order, a critical mediating parameter for glass deformation. Synchrotron X-ray microdiffraction was used to under-stand structural heterogeneity across the build-planes of a selective laser melted Zr-based BMG. While negligible macroscopic heterogeneityin the structure was observed over a 10 mm build height for the X-ray amorphous material, small periodic variations were observed on theorder of 40–80 $\mu$m. This dimensional scale was rationalized as a consequence of melt-pool solidification from laser processing, which impartsa calculated local strain variation of $\pm$ 0.1%. It is anticipated that this structural insight will help to rationalize microscale deformation effectsfrom the periodic structural variation of selective laser melting produced BMGs