Observation of Gas Pores Inside the Columnar Grains of a Lotus Type Porous Copper

Gas pores growing inside the columnar grains, instead of at grain boundary regions were observed in a lotus type porous copper. It is suggested that the lack of effective nucleation substrate in the pure copper melt makes the nucleation and subsequent growth of gas pores difficult. Therefore the melt must be sufficiently undercooled to provide enough free energy for the nucleation, and as a result the gas saturated melt will transform into a higher energy state of gas pores inside the columnar grains. Keywords: Porous material; Solidification; Gas Pore; Nucleation.