Fabrication and Applications of Lotus-type Porous Metals through Hydride Decomposition

Lotus-type porous metals with aligned long cylindrical pores were fabricated by unidirectional solidification using high-pressure gas (hydrogen) method (PGM) and thermal decomposition method (TDM). The pores are evolved from insoluble gas when the molten metal dissolving the gas is solidified. In the conventional PGM, the hydrogen pressurized in a high-pressure chamber is used as the dissolving gas. However, the use of high-pressure hydrogen is not desirable because of flammable and explosive gas, in particular, for scaling up to mass production of lotus metals. Thus, we propose the thermal decomposition method as an alternative simple fabrication method. The compound containing gas elements is added into the molten metal to fabricate lotus metals. Since the high-pressure gas is not required, TDM is superior method. Lotus metals exhibit various peculiar features and various applications have been developing such as heat sinks, dental implants, parts of machine tools and airplane engines.