After the reduction of Ni/Al2O3 with 5 wt.% Ni
loading at both temperatures, small, island-like Ni particles
were formed. Ni islands were isolated and submicron-
sized particles were noted, as presented in Figs.
2a and 3a. No significant changes in the microstructures
were noted after the reduction at each temperature.
With 20 wt.% Ni loading, the samples reduced
at both temperatures had similar microstructures: Ni
coating relatively uniformly covered the foam surface,
as presented in Figs. 2b and 3b. The reduction with H2
led to disappearance of visible cracks. Formation of
these microstructures could be explained by complex
mass transport mechanism that occurred at elevated
temperature during the reduction. At the reduction
conditions, Ni particles gained sufficient mobility and
migrated, which resulted in formation of contacts
between particles and their growth. No agglomerates
occurred in any of the reduced samples