Fabrication of Porous Copper with Directional Pores through Thermal Decomposition of Compounds

Abstract

Lotus-type porous copper with aligned long cylindrical pores was fabricated by unidirectional solidification in an argon atmosphere. The hydrogen dissolved in molten copper through thermal decomposition of titanium hydride contained in the mold, which then formed hydrogen gas that evolved into the gas pores in the solidified copper. On the other hand, titanium may form oxides in the melt that serve as nucleation sites for insoluble hydrogen. The porosity and pore size decreased with increasing atmospheric argon pressure during the solidification, which can be explained by the Boyle–Charles law and the possible suppression of the decomposition due to external pressure. The addition of titanium hydride was more effective when it was added just before the melt solidified than when it was added to the melt. Moreover, the thermal decomposition method (TDM) is superior to the conventional fabrication method, which requires high pressure hydrogen gas. Thus, TDM is a promising fabrication technique for various lotus metals.