A preliminary study of the fabrication of rhenium nanowires by directional solidification of NiAl-Re eutectic alloys

The investigations of the metallic nanowires have received great attention due to their excellent properties of predominate sensibility, field emission and great memory functions. Rhenium nanowires were fabricated through directional solidification and selective etching of a NiAl-Re eutectic alloy, which is called the DSW (Directional Solidification Nanowires) technique. A NiAl-1.5at%Re eutectic alloy was directionally solidified in a Bridgman-type directional solidification furnace under a temperature gradient of 300 K/cm. Different size and morphologies of NiAl-Re eutectics were obtained by changing the growth rate. The microstructures of the NiAl-Re eutectic alloys and the relationship between growth rate and the spacing of the fibers as well as the size were analyzed. It is found that the fiber spacing and the fiber sizes decrease gradually with the increasing of the growth rate, and both of them have well linear relation with the square of the growth rate. The selective dissolution of the NiAl matrix was achieved with a mixture of HCl:H₂O₂. This procedure produces an anisotropic etching of the eutectic. The corroded surface is dominated by rhenium fibers (diameter of 450-500 nm) with different length. The fibers obtained might subsequently be applied for the preparation of nanoelectrode arrays.