Fabrication of Porous Metals with Directional Pores through Unidirectional Solidification of Gas-Dissolved Melt
Lotus-type porous metals with long cylindrical pores aligned in one direction are fabricated by unidirectional solidification through thermal decomposition method (TDM). The pores are evolved from insoluble gas when the molten metal dissolving the gas is solidified. In the conventional pressurized gas method, hydrogen pressurized in a high-pressure chamber is used to dissolve hydrogen in the melt. However, the use of high-pressure hydrogen is not desirable because of its inflammability and explosive nature. This is particularly true when scaling up to mass production of lotus/Gasar metals. In order to overcome this shortcoming, the thermal decomposition method was developed. Gas-forming compounds such as hydrides were added into the molten metal to fabricate lotus/Gasar metals. The porosity and pore size were controlled by the amount of gas-forming compounds, solidification rate, atmospheric pressure, etc. TDM method is applied to fabricate lotus copper, aluminium and iron.
Jian-Feng Nie and Allan Morton
H. Nakajima "Fabrication of Porous Metals with Directional Pores through Unidirectional Solidification of Gas-Dissolved Melt", Materials Science Forum, Vols. 654-656, pp. 1452-1455, 2010