RESEARCH ON THE SELECTIVELY DISSOLUTION CHARACTERISTICS OF Cu–Mn ALLOYS AND FABRICATION OF NANOPOROUS COATINGS BY LASER CLADDING HYBRID ELECTROCHEMICALLY DEALLOYING

Abstract

Nanoporous metals have attracted considerable attention for a wide range of applications in catalysis,sensing and bio-detection due to their large surface-to-volume ratios and excellent thermal and electrical conductivities.It has been proven that dealloying is the most effective method to yield nanoporous metals.Recently,a number of nanoporous metals,including Au,Ag and Pt have been synthesized by dealloying.Most of the research focused on etching the more active components from the precursors in different electrolyte owing to their higher reactivity,such as Ag,Al,Zr and Mn.In this paper selective dissolution of Cu or Mn components from Cu-Mn alloys was reported, and nanoporous coatings were fabricated by a two-step process involving high power laser cladding of a homogeneous Cu40Mn60 alloy coatings followed by selectively electrochemical dealloying.Cu-Mn alloy coatings with fine shape,low dilute ratio and refined microstructure were fabricated on mild steel by means of laser processing.The second dendrite arm spacing(SDAS) decreased with the increasing of laser remelting speed.The SDAS can be refined to be 1.6μm with the laser remelting speed 83 mm/s.Polarization curve indicates that Cu-Mn alloy shows selective dissolution characteristics for different electrolytes.Nanoporous Cu and nanoporous Mn were fabricated with optimal electrochemically dealloying parameters in 0.1 mol/L HCl and 0.1 mol/L KNO_3 solution respectively.Nanoporous Cu with pore size ranges from 30 nm to 50 nm,while the surface morphology of the porous Mn was a ribbon-like structure with ultrahigh roughness factor up to 900.