Prakt. Met. Sonderband 47 (2015) 9 
copy (see Figure 7). We designed a reaction chamber that fits into the beam path of the X-ray mi- 
öblem and croscope. Using this attachment, the morphological change in the iron/iron oxide powder during the 
ochemical cyclic oxidation and reduction reaction, which influences the life time and the storage capacity of 
ES, gig. the storage material, can be observed. If nano-sized iron powders are used, the process temperature 
nee of can be lowered due to the high surface area causing high reactivity. The oxidation reaction of very 
itfsion and fine iron powder with a particle size below 100 nm was investigated by in-situ experiments with 
affet aly temperatures up to 500°C in wet nitrogen atmosphere. The formation of a dense oxide layer ham- 
device per pers the gas exchange — release of hydrogen and entry of water vapor — and leads to the expansion 
direct rel. of the powder agglomerates. The formation of such an oxide layer has to be prevented by material 
ie perf and process parameter selection. The in-situ X-ray microscopy is a suitable method for the charac- 
terization of processes at the microscopic scale within the development of new storage technologies 
[15]. An optimized powder composition and a pretreatment applying ball-milling lead to an im- 
of fuel cell proved storage capacity throughout cycling. 
gation, like 
ther possible 
0-Sized iron 
Fe+dH0 
I storage ca- 
ch results in 
(ide as addi- 
oughout cy- 
5 before and 
atmospheric 
eam path of 
‚merates dur- 
Wa Fig. 7: Powder agglomerates, kinetics imaged using nano X-ray tomography. 
je size 0 
arget powder 
(.rqy mICTOS-