Oxidation Mechanisms of Metallic Carrier Materials for Gas Separation Membranes

A major goal of research worldwide is the development of new concepts for reducing CO2
emissions in power plants and other industry sectors. Very promising concepts are the
“carbon capture and storage” (CCS) technologies. These contain gas separation units
requiring the use of gas separation membranes. The need to reduce membrane thickness in
combination with a high susceptibility for mechanically-induced failure of the ceramic
membrane material makes the use of a metallic support structure for the membranes
necessary. The requirements for the supports can be fulfilled by α-Al2O3 forming NiCrAlbase
alloys. The membrane carriers have to withstand different aggressive atmospheres at
temperatures up to 1000°C. As the formation of a protective Al2O3 surface scale is crucial for
the operation of the membrane carrier, the present study deals with the influence of
temperature and gas atmosphere on the selective oxidation of aluminum thereby using the
commercially available alloys 602 CA and Haynes 214 with different aluminum contents of
2.4 wt.-% and 4.5 wt.-%, respectively. As these amounts are far below the high aluminum
contents of MCrAlY alloys (10 – 13 wt.-% Al) considered as promising materials for the use
as support structure, the investigation of possible effects of gas composition and/or
temperature on the protective Al2O3 scale formation was possible in relatively short-term
experiments (up to 1000 h). The studies were focused on the temperature range 800 – 1100°C
in different atmospheres [...]