Lotus-type porous materials whose long cylindrical pores are aligned in one direction were fabricated by unidirectional solidification from the melt dissolving gas. The pores were evolved by supersaturation of gas atoms when the liquid was solidified. Although such porous metals with high thermal conductivity were produced by Gasar process, the process could not produce porous metals with low thermal conductivity, which possess uniform pore size and porosity. In order to obtain uniform pore size and porosity in metals with low thermal conductivity, we developed a new "continuous zone melting technique". Using this technique various metals, alloys, intermetallic compounds and semiconductors were fabricated. Mechanical properties of tensile and compressive strength of lotus-type porous metals and alloys exhibit significant anisotropy, depending on the pore growth direction. Furthermore, lotus-type porous iron fabricated using a pressurized nitrogen gas instead of hydrogen exhibits superior strength.
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