Durability and wear resistance of laser-textured hardened stainless steel surfaces with hydrophobic properties

Hydrophobic surfaces are of high interest to industry. While surface functionalization has attracted significant interest, from both industry and research, the durability of engineered surfaces remains a challenge, as wear and scratches deteriorate their functional response. In this work, a cost-effective combination of surface engineering processes on stainless steel was investigated. Low-temperature plasma surface alloying was applied to increase surface hardness from 172 to 305 HV. Then, near-infrared nanosecond laser patterning was deployed to fabricate channel-like patterns that enabled superhydrophobicity. Abrasion tests were carried out to examine the durability of such engineered surfaces during daily use. In particular, the evolution of surface topographies, chemical composition, and water contact angle with increasing abrasion cycles were studied. Hydrophobicity deteriorated progressively on both hardened and raw stainless steel samples, suggesting that the major contributing factor to hydrophobicity was the surface chemical composition. At the same time, samples with increased surface hardness exhibited a slower deterioration of their topographies when compared with nontreated surfaces. A conclusion is made about the durability of laser-textured hardened stainless steel surfaces produced by applying the proposed combined surface engineering approach

Laser polishing of 3D printed mesoscale components

Laser polishing of various engineered materials such as glass, silica, steel, nickel and titanium alloys, has attracted considerable interest in the last 20 years due to its superior flexibility, operating speed and capability for localised surface treatment compared to conventional mechanical based methods. The paper initially reports results from process optimisation experiments aimed at investigating the influence of laser fluence and pulse overlap parameters on resulting workpiece surface roughness following laser polishing of planar 3D printed stainless steel (SS316L) specimens. A maximum reduction in roughness of over 94% (from ∼3.8 to ∼0.2 μm Sa) was achieved at the optimised settings (fluence of 9 J/cm2 and overlap factors of 95% and 88–91% along beam scanning and step-over directions respectively). Subsequent analysis using both X-ray photoelectron spectroscopy (XPS) and glow discharge optical emission spectroscopy (GDOES) confirmed the presence of surface oxide layers (predominantly consisting of Fe and Cr phases) up to a depth of ∼0.5 μm when laser polishing was performed under normal atmospheric conditions. Conversely, formation of oxide layers was negligible when operating in an inert argon gas environment. The microhardness of the polished specimens was primarily influenced by the input thermal energy, with greater sub-surface hardness (up to ∼60%) recorded in the samples processed with higher energy density. Additionally, all of the polished surfaces were free of the scratch marks, pits, holes, lumps and irregularities that were prevalent on the as-received stainless steel samples. The optimised laser polishing technology was consequently implemented for serial finishing of structured 3D printed mesoscale SS316L components. This led to substantial reductions in areal Sa and St parameters by 75% (0.489–0.126 μm) and 90% (17.71–1.21 μm) respectively, without compromising the geometrical accuracy of the native 3D printed samples

NLO properties of new stryquinolinium dye thin films deposited by pulsed laser deposition

International audienc

Large nonlinear optical properties of new styrylquinolinium dye thin films deposited by pulsed laser deposition

Date du colloque&nbsp;: 09/2011</p

Effects of mould wear on hydrophobic polymer surfaces replicated using plasma treated and laser-textured stainless steel inserts

YesThe mass production of polymeric parts with functional surfaces requires economically viable manufacturing routes. Injection moulding is a very attractive option however wear and surface damage can be detrimental to the lifespan of replication masters. In this research, the replication of superhydrophobic surfaces is investigated by employing a process chain that integrates surface hardening, laser texturing and injection moulding. Austenitic stainless steel inserts were hardened by low temperature plasma carburising and three different micro and nano scale surface textures were laser fabricated, i.e. submicron triangular LaserInduced Periodic Surface Structures (LIPSS), micro grooves and Lotus-leaf like topographies. Then, a commonly available talc-loaded polypropylene was used to produce 5000 replicas to investigate the evolution of surface textures on both inserts and replicas together with their functional response. Any wear orsurface damage progressively built up on the inserts during the injection moulding process had a clear impact on surface roughness and peak-to-peak topographies of the replicas. In general, the polymer replicas produced with the carburised inserts retained the wetting properties of their textured surfaces for longer periods compared with those produced with untreated replication masters.European Union’s H2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 675063 (www.laser4fun.eu). The work was also supported by three other H2020 projects, i.e. “HighImpact Injection Moulding Platform for mass-production of 3D and/or large micro-structured surfaces with Antimicrobial, Self-cleaning, Anti-scratch, Anti-squeak and Aesthetic functionalities” (HIMALAIA, No. 766871), “Process Fingerprint for Zero-defect Net-shape Micromanufacturing” (MICROMAN, No. 674801) and “Modular laser based additive manufacturing platform for large scale industrial applications” (MAESTRO, No. 723826). Further support was provided by the UKIERI DST programme “Surface functionalisation for 18/20 Accepted in the journal Tribology – Materials, Surfaces & Interfaces. food, packaging, and healthcare applications

Novel Styrylquinolinium Dye Thin Films Deposited by Pulsed Laser Deposition for Nonlinear Optical Applications

The nonlinear optical (NLO) properties of novel styrylquinolinium dye thin films for photonic applications have been studied by the Z-scan, second harmonic generation (SHG), and third harmonic generation (THG) techniques, providing both the second- and third-order nonlinear optical parameters. The styrylquinolinium dye (E)-1-ethyl-4-(2-(4-hydroxynaphthalen-1-yl)vinyl)quinolinium bromide was synthesized by the Knoevenagel condensation, and its structure and physicochemical properties were determined by H-1 NMR, C-13 NMR, FTIR, UV-vis spectroscopy, and elemental analysis. Functional thin films were deposited by pulsed laser deposition (PLD) using UV TEA N-2 laser onto glass substrates and KCl, NaCl monocrystals at room temperature and vacuum at 10(-3) mbar/0.1 Pa. Further characterization of the films and target from native material by FTIR spectroscopy revealed that there was no difference between the deposited films and the initial material. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) measurements have been also performed in order to provide information about the morphology and topology of the thin films

Mutation increasing β-carotene concentrations does not adversely affect concentrations of essential mineral elements in pepper fruit

<div><p>Vitamin and mineral deficiencies are prevalent in human populations throughout the world. Vitamin A deficiency affects hundreds of millions of pre-school age children in low income countries. Fruits of pepper (<i>Capsicum annuum</i> L.) can be a major dietary source of precursors to Vitamin A biosynthesis, such as β-carotene. Recently, pepper breeding programs have introduced the orange-fruited (<i>of</i>) trait of the mutant variety Oranzheva kapiya, which is associated with high fruit β-carotene concentrations, to the mutant variety Albena. In this manuscript, concentrations of β-carotene and mineral elements (magnesium, phosphorus, sulphur, potassium, zinc, calcium, manganese, iron and copper) were compared in fruit from P31, a red-fruited genotype derived from the variety Albena, and M38, a genotype developed by transferring the orange-fruited mutation (<i>of</i>) into Albena. It was observed that fruit from M38 plants had greater β-carotene concentration at both commercial and botanical maturity (4.9 and 52.7 mg / kg fresh weight, respectively) than fruit from P31 plants (2.3 and 30.1 mg / kg fresh weight, respectively). The mutation producing high β-carotene concentrations in pepper fruits had no detrimental effect on the concentrations of mineral elements required for human nutrition.</p></div