Experimental
2.1. Copper foam preparation
Elemental copper powder (99% purity) with a mean powder size of
75 μmwas used as the initialmaterial,while commercial rawcane sugar
was the space holder material. To ensure the cell size of the final foam
was within a desired range, the raw cane sugar powder was sieved
into two size groups: 0.5–1.0 and 0.125–0.5 mm, with nominal mean
sizes of 0.70 and 0.35 mm, respectively. The production method, describedindetail
in ref. [22],was then applied as discussed below(Fig. 1).
Initially, the copper powder was mixed thoroughly with the crystalline
raw cane sugar at a pre-specified weight ratio depending on the
desired relative density of the final product. A small amount of water
(∼2% in weight) was sprinkled in the Cu powders to ensure homogenousmixing.
The mixture was uniaxially pressed at 210 MPa in a stainless
steel cylindrical die with a diameter of 16 mm. The crystalline raw
cane sugar was removed from the green compact by water leaching at
room temperature. The final stage involved sintering performed in a
vacuum furnace (p= 10−3 Torr).