Investigation of micro and nanostructure on porous high-entropy alloy surface influences its hydrophobicity

The micro and nanostructures of materials have an important effect on the wettability of materials' surfaces. For AlCoCrFeNi_2.1 and AlCoCrFe Ni High-entropy alloy, the special porous micro and nanostructure can be fabricated by electrochemical dealloying in 5 wt.% sulfuric acid solution aiming to improve the hydrophobicity of the material surface. The surface crystal structure of the prepared porous HEAs was characterized by x-ray diffraction, the micromorphologies were characterized by a scanning electron microscope, and the static water contact angles were measured by a contact angle goniometer. The results showed that AlCoCrFeNi_2.1 HEA showed nanoscale pores and smooth surfaces, while AlCoCrFeNi HEA showed microscale pores, but rough surfaces generated from nanoscale short rod-like particles. AlCoCrFeNi_2.1 HEA showed FCC (Fe-, Cr- and Ni-rich) and BCC (Al- and Ni-rich) dual phase structures and AlCoCrFeNi HEA showed BCC (Al- and Ni-rich) and B2 (Fe- and Cr-rich) phase structure. The prepared porous AlCoCrFeNi HEA possessed quite good hydrophobicity than that of AlCoCrFeNi_2.1 HEA, and this can be explained as the result of the "lotus effect"formed by the aggregation of nanoscale short rod-like particles.