Redox Cycling of Fe/FeO Microstructures
Stephen Wilke, Jacob Mack, and *Pedro Javier Lloreda Juardo,
Our group has used freeze casting to prepare highly porous foams of numerous metals, including copper [2,3], nickel , cobalt , tungsten , and iron [7,8]. Freeze casting typically requires suspensions containing submicron or nanometric particles to ensure suspension stability, but these sizes of particles are not practical for metals due to their high propensity for surface oxidation. Instead, we freeze-cast foams of the corresponding metal oxides and then reduce and sinter the oxide green bodies under H2 gas.
This reduction and sintering step results in large structural changes in the green body, due to volume contraction associated with the reduction transformation and densification during sintering . We are using in situ X-ray microtomography to observe this structural evolution in foams created with various pore sizes and total porosity, to better understand the processing-structure relationships for metal foams created via freeze casting.
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