Comparison between TWI and OPC techniques for studying porous metallic slabs

Abstract
The aim of this study is to compare thermal diffusivity of the pressed iron powder measured by contact photoacoustic method and remote thermal wave techniques, which were performed by open photoacoustic cell (OPC) and thermal wave interferometry (TWI), respectively. The samples were prepared using iron powder 99.9%, which were cold pressed (2 to 22 ton) and no sintered. OPC technique shows values of thermal diffusivity with wide variation and poor reproducibility ( cm²/s). These results can indicate that porous materials should present pressure leak using OPC method. On the other hand, TWI showed a neat behavior from 2 to 22 tons, with thermal diffusivity increasing with compacting pressure from 0.008 to 0.101 cm²/s, approaching to the value of the molten Iron (~ 0.23 cm²/s).