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Spiky Nickel Electrodes for Electrochemical Oxygen Evolution Catalysis by Femtosecond Laser Structuring
摘要： Micro- and nanostructured Ni/NiO surfaces were generated by femtosecond laser structuring for oxygen evolution reaction in alkaline water electrolysis cells. For two different angles between the laser beam and the nickel surface, two different types of laser-structured electrodes were prepared, characterized, and compared with a plane tempered nickel electrode. Their electrochemical activities for the oxygen evolution reaction were tested by using cyclic and linear sweep voltammetry. The chemical surface composition was investigated by X-ray photoelectron spectroscopy. Laser structuring increased the overall electrochemical performance by more than one order of magnitude. The overpotential of the laser-structured electrodes for the oxygen evolution reaction was decreased by more than 100 mV due to high defect densities of the structures created by the laser ablation process.
关键词： nickel electrodes,femtosecond laser structuring,alkaline water electrolysis,electrochemical catalysis,oxygen evolution reaction
更新于2025-09-23 15:21:01
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All-carbon THz components based on laser-treated diamond
摘要： We report on fs laser structuring and graphitization of diamond and experimental characterization of its THz response. A full characterization of graphitized, conductive layer generated by laser irradiation is carried out by performing scanning-electron microscopy, Raman spectroscopy and electrical measurements. The transmittance of the laser textured diamond samples, both with the graphitic overlayer and after selective oxidizing etching, is analyzed in the (0.25 ÷ 6.0) THz spectral range. A significant selective absorption of the graphitized overlayer towards polarized THz radiation is demonstrated, which is associated to the formation of graphitic laser induced periodic surface structures. This anisotropy allows conceiving compact passive metasurfaces based on conductive/dielectric patterns on the diamond plate surface for the development of robust, lightweight and broadband THz optical components.
关键词： graphitic laser induced periodic surface structures,graphitization,electrical measurements,fs laser structuring,THz response,transmittance,THz optical components,polarized THz radiation,conductive layer,diamond,Raman spectroscopy,metasurfaces
更新于2025-09-23 15:19:57
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Laser Direct Structuring of Bioinspired Spine with Backward Microbarbs and Hierarchical Microchannels for Ultrafast Water Transport and Efficient Fog Harvesting
摘要： Achieving effective dropwise capture and ultrafast water transport is essential for fog harvesting. In nature, Cactus uses the conical spine with micro-barbs to effectively capture fog while Sarracenia utilizes the trichome with hierarchical microchannels to quickly transport water. Herein, we combined their advantages to present a novel configuration, spine with barbs and hierarchical channels (SBHC), for simultaneous ultrafast water transport and high-efficient fog harvesting. This bio-inspired SBHC exhibited the fastest water transport ability and the highest fog harvesting efficiency in comparison with spine with hierarchical channels (SHC), spine with barbs and grooves (SBG) and spine with barbs (SB). Based on the fundamental SBHC unit, we further designed and fabricated a 2D spider-web alike fog collector and a 3D cactus alike fog collector using direct laser structuring and Origami techniques. The 2D spider-web and 3D cactus alike fog collectors showed high-efficient fog collection capacity. We envision that this fundamental understanding and rational design strategy can be applied in fog harvesting, heat transfer, liquid manipulation, and microfluidics.
关键词： Direct laser structuring,Water transport,Spine and micro-barbs,Fog harvesting,Hierarchical microchannels
更新于2025-09-23 15:19:57
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Wetting angle stability of steel surface structures after laser treatment
摘要： In this work, we have used a nanosecond pulsed fiber laser to modify the wettability characteristics of AISI 430 steel. For this, various surface morphologies were created on the samples by laser irradiation with different overlapping and intensity parameters. Immediately upon laser treatment, all the structured samples acquired either hydrophilic or superhydrophilic wetting angles. All the samples were also analyzed with XRD. Then, laser-treated samples were kept in ambient air and/or low-temperature annealing was applied to reach hydrophobic surface properties. Interestingly, these surfaces returned back practically to their initial wetting state by cleaning in an ultrasonic bath. The obtained results are analyzed based on the existing wettability models.
关键词： Nanosecond laser structuring,Hydrophobic and hydrophilic surfaces,Wettability transition,Wetting angle stability
更新于2025-09-19 17:13:59
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The Effect of Laser Structuring of Carbon Nanotubes on the Proliferation of Chondroblasts and Mesenchymal Stem Cells
摘要： The density of cartilage cells (chondroblasts) proliferating on a silicon substrate coated with vertically oriented arrays of multi-walled carbon nanotubes (MWCNTs) was shown to be higher than on a pure silicon substrate. Electron microscopy showed that the cells in a nutrient medium affected the vertical position of the nanotubes in the array. A method for structuring the MWCNT arrays by 100-ns laser pulse scanning and abrasive water processing on planar substrates was developed. As a result of the structuring of the MWCNTs, the arrays become resistant to bending under the influence of the nutrient medium with mesenchymal stem cells. Structured MWCNT arrays were shown to have no toxic or pathological effect on the viability and morphology of stem cells. Thus, such materials can be suggested for use in cell-adhesive components of biomedical devices.
关键词： carbon nanotubes,laser structuring,mesenchymal stem cells,chondroblasts,cell proliferation
更新于2025-09-19 17:13:59
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Laser Dissimilar Joining of Al7075T6 with Glass-Fiber-Reinforced Polyamide Composite
摘要： Dissimilar joining between metal and composite sheets is usually carried out by mechanical or adhesive joining. Laser dissimilar joining between metal and composite sheets could be an alternative to these methods, as it is a cost-effective and versatile joining technique. Previously, textured metallic and composite parts have been held together and heated with a laser beam while pressure is applied to allow the melted polymer to flow into the cavities of the metal part. The main issue of this process relates to reaching the same joint strength repetitively with appropriate process parameters. In this work, both initial texturing and laser joining parameters are studied for Al 7075-T6 and glass-fiber-reinforced PA6 composite. A groove-based geometry was studied in terms of depth-to-width aspect ratio to find an optimal surface using a nanosecond fiber laser for texturing. Laser joining parameters were also studied with different combinations of surface temperature, heating strategy, pressure, and laser feed rate. The results are relatively good for grooves with aspect ratios from 0.94 to 4.15, with the widths of the grooves being the most critical factor. In terms of joining parameters, surface reference temperature was found to be the most influential parameter. Underheating does not allow correct material flow in textured cavities, while overheating also causes high dispersion in the resulting shear strength. When optimal parameters are applied using correct textures, shear strength values over 26 kN are reached, with a contact area of 35 × 45 mm2.
关键词： metal polymer joint,groove aspect ratio,laser structuring,laser direct joining,shear strength
更新于2025-09-16 10:30:52
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Laser-assisted micro-milling of austenitic stainless steel X5CrNi18-10
摘要： This paper presents a novel Laser-Assisted Micro-Milling (LAMM) process of austenitic stainless steel X5CrNi18-10. The LAMM process is compared with the conventional micro-milling process. Ultra-short pulsed laser radiation is utilized for the structuring of the workpiece surface prior to the micro-milling process. Different laser structures are produced on the workpiece surface at a constant laser scanning speed with various laser powers and laser line spans. The high performance of the developed process is shown by experimental investigations. The effect of laser structuring on the micro-milling forces and temperature indicated the superior performance of the new LAMM process. Cutting forces and temperature could be reduced by up to 70% and 50%, respectively. The results of conventional micro-milling showed that increasing the cutting speed, at a constant undeformed chip thickness, reduced the micro-milling forces. Increasing the cutting speed from 50 to 250 m/min halved both the trust and normal forces, while it slightly improved the surface roughness. On the other hand, increasing the feed per tooth degraded the surface roughness and increased the cutting forces. Furthermore, in conventional milling the workpiece was subjected to high plastic deformation during the cutting process, while side flow, smeared material, metal debris, and cavities were observed on the workpiece surface.
关键词： Laser-assisted micro-milling,Austenitic stainless steel,Ultra-short pulsed laser,Laser structuring,Micro-milling
更新于2025-09-12 10:27:22