Papers by Author: K.G. Nickel

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Authors: E. Butchereit, K.G. Nickel
1592
Authors: C. Berthold, K.G. Nickel
1588
Authors: K.G. Nickel, U. Däumling, K. Weisskopf
295
Authors: N. Maier, K.G. Nickel, Georg Rixecker
Abstract: Corrosion experiments on a number of rare earth di-silicates containing Y, Yb and Lu have been conducted in flowing air with 30 vol.% H2O at 1500°C. Nominally the corrosion rate is slower by a factor 5 to 10 compared to silica. However, alumina impurity incorporation has a profound influence on the process of corrosion as it masks not only the gravimetric results but also changes the surface phase assemblages to contain rare earth garnets and liquid phases. It is presumed that silica loss occurs under those conditions via the liquid phase and does not necessarily follow the same kinetics as direct silicate corrosion. Furthermore, atmospheric silicon hydroxide saturation effects contribute to the corrosion process. Currently all determined corrosion rates of rare earth silicates are viewed as system specific only.
1780
Authors: K.G. Nickel, S. Merkel
Abstract: Sodium-rich glasses of the system Na2O-SiO2 are well known to be easily soluble in water. This is not true for silica-rich compositions. We have manufactured quenched glasses with silica contents between 65 and 80 wt.% SiO2 and followed the water interaction at 100°C by measuring mass and sample dimensions in intervals. Comparing the path of edge length, mass and volume to a general shrinking core model for cuboids we conclude that only compositions between 65 and 70 wt% SiO2 can be described well by a simple dissolution process. The logarithm of the dissolution rate constant varies linearly with the SiO2 content. At higher silica contents the mechanism changes towards leaching of sodium. We propose changing glass structures to be responsible for the change in mechanism.
1823
Authors: M. Lehmann, C. Berthold, W. Pabst, Eva Gregorová, K.G. Nickel
1387
Authors: K.G. Nickel, Günter Petzow
11
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