Highly Regular Hexagonally-Arranged Nanostructures on Ni-W Alloy Tapes upon Irradiation with Ultrashort UV Laser Pulses

Abstract

Nickel tungsten alloy tapes (Ni—5 at% W, 10 mm wide, 80 µm thick, biaxially textured) used in second-generation high temperature superconductor (2G-HTS) technology were laser-processed in air with ultraviolet ps-laser pulses (355 nm wavelength, 300 ps pulse duration, 250–800 kHz pulse repetition frequency). By employing optimized surface scan-processing strategies, various laser-generated periodic surface structures were generated on the tapes. Particularly, distinct surface microstructures and nanostructures were formed. These included sub-wavelength-sized highly-regular hexagonally-arranged nano-protrusions, wavelength-sized line-grating-like laser-induced periodic surface structures (LIPSS, ripples), and larger irregular pyramidal microstructures. The induced surface morphology was characterized in depth by electron-based techniques, including scanning electron microscopy (SEM), electron back scatter diffraction (EBSD), cross-sectional transmission electron microscopy (STEM/TEM) and energy dispersive X-ray spectrometry (EDS). The in-depth EBSD crystallographic analyses indicated a significant impact of the material initial grain orientation on the type of surface nanostructure and microstructure formed upon laser irradiation. Special emphasis was laid on high-resolution material analysis of the hexagonally-arranged nano-protrusions. Their formation mechanism is discussed on the basis of the interplay between electromagnetic scattering effects followed by hydrodynamic matter re-organization after the laser exposure. The temperature stability of the hexagonally-arranged nano-protrusion was explored in post-irradiation thermal annealing experiments, in order to qualify their suitability in 2G-HTS fabrication technology with initial steps deposition temperatures in the range of 773–873 K.

Laser‐Textured Surfaces: A Way to Control Biofilm Formation?

“…Top row a,b): triangular nanopillars (TNP) (Reprinted from [ 30 ] S. van der Poel, et al., Fabricating laser‐induced periodic surface structures on medical grade cobalt–chrome–molybdenum: tribological, wetting and leaching properties, Lubricants 7:70, Copyright 2019 under Creative Commons BY 4.0 license. Retrieved from https://doi.org/10.3390/lubricants7080070); Bottom row c,d): hexagonally‐arranged nanostructures (HAN) (Reprinted from [ 31 ] L. Porta‐Velilla, et al., Highly regular hexagonally‐arranged nanostructures on Ni‐W alloy tapes upon irradiation with ultrashort UV laser pulses, Nanomaterials 12:2380, Copyright 2022 under Creative Commons BY 4.0 license. Retrieved from https://doi.org/10.3390/nano12142380).…”

“…These highly regular nanostructures were formed on a Ni–W alloy upon line processing with linearly polarized ultraviolet ps‐laser pulses. [ 31 ] The top‐view scanning electron microscopy (SEM) micrograph (Figure 9c) reveals the hexagonal symmetry of circular nanopillars arranged at periods Λ HAN ≈400 nm somewhat exceeding the laser wavelength (λ = 355 nm), while the cross‐sectional transmission electron microscopy (TEM) view (Figure 9d) indicates nanopillar diameters and heights of ≈130 nm, i.e., an aspect ratio around A ≈ 1.…”

Grain Orientation, Angle of Incidence, and Beam Polarization Effects on Ultraviolet 300 ps‐Laser‐Induced Nanostructures on 316L Stainless Steel

“…This phenomenology has been experimentally observed on many metals, such as Pt, W, Ni, or steel. [17,18] In a previous work, [19] it was found that the laser-induced nanostructures formed on a nickel alloy surface upon irradiation with a 300-ps ultraviolet (UV) laser were strongly dependent on the crystallographic grain orientation. In particular, this behavior was observed on a biaxially textured nickel alloy tape using a broad range of laser fluence values, and contrasts with typical LIPSS generated with fs-lasers.…”

“…On the other hand, from the processing point of view, it is also important to develop laser scanning protocols that can be scaled to process large surface areas. One approach is to use the Laser Line Scanning (LLS) methodology, [19][20][21] where the focused laser beam repeatedly describes a line in a given direction, while the sample moves continuously in the perpendicular one. The control of beam overlapping in the direction of laser beam scanning is performed by adjusting the repetition frequency and the laser scanning velocity.…”

Special Issue “Dynamics and Processes at Laser-Irradiated Surfaces—A Themed Issue in Honor of the 70th Birthday of Professor Jürgen Reif”

“…Our Special Issue attracted high-quality contributions from both academics and from industry and finally bundles together 1 review paper of Jürgen Reif [ 3 ], 1 perspective article [ 4 ], and 17 original research articles [ 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ]. These publications are focusing on the latest achievements in areas of laser–matter interaction [ 16 , 18 , 22 , 23 , 27 , 30 , 31 ], nonlinear optics and photonics [ 22 , 23 , 26 ], spatial beam shaping [ 15 , 28 ], surface dynamics [ 4 , 17 , 22 , 23 ], micro- and nanotechnology [ 16 , 18 , 20 , 24 , 26 , 27 , 31 ], laser-induced periodic surface structures (LIPSS) [ 3 , 4 , 19 , 20 , 21 , 27 ,…”