Synthesis and Electron Microscopy of Superalloy Nanowires

Abstract

An electrodeposition based methodology for synthesizing Ni-Cr-Fe nanowires is provided. As-synthesized nanowires were 200 nm in diameter and more than 5 μm in length. Detailed characterization of the nanowires using electron microscopy technique revealed an amorphous microstructure for the nanowires with uniform distribution of Ni, Fe and Cr atoms. Annealing of the nanowire using the electron beam inside electron microscope resulted in gradual crystallization of amorphous microstructure into a nanocrystalline one which illustrated the potential for microstructural engineering of the nanowires. © 2014 The Electrochemical Society. [DOI: 10.1149/2.0061502eel] All rights reserved.Manuscript submitted October 13, 2014; revised manuscript received November 21, 2014. Published December 12, 2014 Family of Ni-rich, Ni-Fe-Cr alloys which fall in the group of materials known as Ni based superalloys possess remarkable resistance to degradation when exposed to extreme conditions such as high temperatures and highly corrosive environments.1,2 Ni provides high resistance to stress corrosion cracking and degradation due to corrosive attack by several inorganic and organic compounds.1,2 Cr provides resistance to oxidizing environments in corrosive solutions or high temperatures.1,2 Although the literature contains wealth of data on physical, thermal and mechanical properties of Ni-Fe-Cr alloys, one important aspect that has not been explored yet for superalloys in general is their response when they are formed in isolated nano-dimensional solids such as nanoparticles and nanowires with ultra-fine crystalline or amorphous microstructures. Although much is known about the grain size effect on mechanical properties, a synergistic effect of factors such as ultrafine crystalline or amorphous microstructure and nano-dimensional geometry still remains scarcely explored. It has been shown by researches that the mechanical behavior of systems when they are present as isolated nanosolids can be considerably different from the case when they are formed in bulk geometries. 3,4The present work provides a template assisted electrochemistry based methodology for synthesizing Ni-Fe-Cr nanowires of 200 nm diameter. This methodology has been widely used for synthesizing single component and alloyed nanowires. [5][6][7][8][9][10][11] It is also illustrated that by suitably annealing the as-synthesized nanowires a microstructural engineering can be performed which can be used to tune the mechanical properties of the nanowires. ExperimentalThree component Ni-Cr-Fe nanowires were synthesized by the conventional electrodeposition technique. Anodic alumina membrane having cylindrical pores with an average diameter of 200 nm, a nominal thickness of 60 μm and pore density of 10 9 pores/cm 2 was used as template for obtaining nanowire morphology. A platinum foil was used as anode. A copper foil attached to the alumina disc using a conductive adhesive tape (carbon tape) was used as cathode. A schematic showing the arrangement of electrodes in the electroch...

Synthesis and electrochemical behaviour of NiFeCr nanoparticle coatings

“…There are extremely few reports in the literature on the synthesis and properties of superalloys in isolated ultra-ne geometries such as nanowires and nano-particles. 5 Investigation of the properties of superalloys in isolated nano-scale geometries or in geometries made from consolidating individual nanosolids can be scientically interesting and technologically relevant as these investigations may reveal some completely novel properties emerging from the synergy between extremely high specic surface area, elemental composition and size dependent microstructure. Dispersions of crystalline superalloy nanoparticles can provide important advantages such as (a) they can be conveniently sprayed over an engineered surface, (b) they can form ultra-thin protective lms and thus facilitate weight reduction, (c) annealing of thin nanoparticle coatings can cause particle-to-particle sintering which can facilitate gradual tuning of the grain size dependent attributes such as mechanical properties, 6,7 corrosion resistance 8 etc., (d) superalloy nanoparticles can be mixed with Ag nanoparticles to provide ultra thin coatings with anti-microbial properties, 9 (e) foreign materials such as graphene can be mixed in superalloy nanoparticle dispersion to produce coating with tunable electrical and thermal conductivities 10,11 etc.…”