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Synthesis of silicon nanoparticles by laser ablation at low fluences in water and ethanol
摘要： Colloidal silicon nanoparticles (Si-nc) where synthesized by laser ablation of a solid Si target in water and ethanol. The target was immersed in a vessel containing the solvent and irradiated during 5 and 10 min at different ?uences: 0.530, 0.608, 0.687 J cm?2. Ablation was carried out using a laser wavelength of 1064 nm. The obtained colloidal nanoparticles were irradiated after the synthesis to evaluate if laser fragmentation could be produced. In addition, a series of nanoparticles using ethanol as liquid medium was synthesized ablating with 532 nm. Colloidal nanoparticles were structurally characterized by Raman spectroscopy and Transmission Electron Microscopy. Size of the Si-nc were calculated by the theorical models: Bond Polarizability Model (BPM) and One-Phonon Con?nement Model (PCM), where nanocrystals ranging from 2 to 11 nm were found.
关键词： Si nanoparticles,laser fragmentation,laser ablation in liquids
更新于2025-09-19 17:13:59
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Development of a novel system for in-situ repair of aeroengine airfoil via pulsed laser ablation
摘要： A novel system for performing in-situ micro-machining of aero-engines for repair applications is proposed in this paper. Using Pulsed Laser Ablation (PLA) as material removal technique, surface cracks caused by foreign objects colliding with airfoils are removed by performing a layer-by-layer micro-machining in the area surrounding the damaged zone. Compared to conventional repair performed by micro-grinding, our invasive PLA system demonstrates a similar level of performance, evaluated from the point of view of fatigue strength in the high cycle (> 107) regime. The follow-up fractographic and metallurgical analysis, indicated that although some micro-structural characteristics are different between the repair methods, the incurred surface damage is limited in magnitude to a thin surface layer (< 30 μm) and the influence on fatigue life is comparable. In the last section, a novel prototype system is presented which allows performing the PLA repair in-situ by use of a miniaturized laser scanning head coupled with a flexible mechanical deployment arm. The system has been successfully tested inside a Roll-Royce Trent jet engine; effectively this proves the possibility of performing in-situ laser micro-machining inside complex mechanical systems such as aero-engines, without the need for complex/expensive disassembly.
关键词： Miniaturized laser system,In-situ micro-machining,Pulsed laser ablation,Aeroengines
更新于2025-09-19 17:13:59
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Lasers Improve Display Glass Cutting
摘要： Non-contact glass cutting by laser offers an attractive alternative to mechanical methods in display fabrication. There are several laser technologies and processing techniques in actual use, each with its own characteristics and advantages.
关键词： CO2 lasers,laser glass cutting,non-contact cutting,filamentation cutting,display fabrication,laser ablation,CO lasers
更新于2025-09-19 17:13:59
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Ultrasensitive MWCNT/PDMS composite strain sensor fabricated by laser ablation process
摘要： Flexible ultrasensitive piezoresistive strain sensors were fabricated by CO2 Laser ablating of the surface of the multiwall carbon nanotube/ polydimethylsiloxane (MWCNT/PDMS) composite film prepared by a coating process. The effects of the MWCNT content and the applied laser power on the electrical and sensing performances of the MWCNT/PDMS composite strain sensor were systematically investigated. It is found that, after laser ablating, the electrical conductivity and the sensing gauge factor of the MWCNT/PDMS film were greatly improved only by the addition of 1.0 wt.% of MWCNT, which is below the percolation threshold of the MWCNT in the PDMS matrix. A novel boscage-like structure at the surface of the film formed by the ablation of the PDMS and the rearrangement of the MWCNT during the laser ablating process was found responsible for the ultrahigh gauge factor of the composite strain sensor, which is about 513 at the strain of 5.0%. The facile and cost-effective fabrication process of the flexible ultrasensitive strain sensor could be simply extended to other polymer composites for the development of new multifunctional and wearable electronic devices.
关键词： Laser ablation,Strain sensor,PDMS,MWCNT
更新于2025-09-19 17:13:59
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ZnO colloids and ZnO nanoparticles synthesized by pulsed laser ablation of zinc powders in water
摘要： ZnO nanoparticles (NPs) were synthesized by pulsed laser ablation of zinc powders suspending in deionized water. The synthesized ZnO NPs were characterized for morphology, structure and optical properties. The ZnO NPs have irregular shapes sized in 10–50 nm and possess a wurtzite structure with polycrystallinity in nature, and grew without a preferential orientation. The supernatant solutions obtained by laser ablation of zinc powders in water exhibit the typical optical absorption edge of wurtzite ZnO near 380 nm and emit a photoluminescence composed of a narrow ultraviolet peak and a broad visible band, characteristics of the near-band-edge emission and the deep-level defects related emission of ZnO, respectively. The formation of ZnO NPs was further confirmed by structural and optical characterization performed for the aggregated ZnO NPs obtained by drop-casting the ZnO colloidal solutions onto Si wafers. And the effects of annealing in N2 on the structure and photoluminescence of the ZnO NPs transferred on Si were also examined.
关键词： ZnO,Laser ablation in liquids,Nanoparticles,Colloids,Deep-level defects
更新于2025-09-19 17:13:59
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The effect of pulse duration on nanoparticle generation in pulsed laser ablation in liquids: Insights from large-scale atomistic simulations
摘要： The generation of colloidal solutions of chemically clean nanoparticles through pulsed laser ablation in liquids (PLAL) has evolved into a thriving research field that impacts industrial applications. The complexity and multiscale nature of PLAL make it difficult to untangle the various processes involved in the generation of nanoparticles and establish the dependence of nanoparticle yield and size distribution on the irradiation parameters. Large-scale atomistic simulations have yielded important insights into the fundamental mechanisms of ultrashort (femtoseconds to tens of picoseconds) PLAL and provided a plausible explanation of the origin of the experimentally observed bimodal nanoparticle size distributions. In this paper, we extend the atomistic simulations to short (hundreds of picoseconds to nanoseconds) laser pulses and focus our attention on the effect of the pulse duration on the mechanisms responsible for the generation of nanoparticles at the initial dynamic stage of laser ablation. Three distinct nanoparticle generation mechanisms operating at different stages of the ablation process and in different parts of the emerging cavitation bubble are identified in the simulations. These mechanisms are (1) the formation of a thin transient metal layer at the interface between the ablation plume and water environment followed by its decomposition into large molten nanoparticles, (2) nucleation, growth, and rapid cooling/solidification of small nanoparticles at the very front of the emerging cavitation bubble, above the transient interfacial metal layer, and (3) spinodal decomposition of a part of the ablation plume located below the transient interfacial layer, leading to the formation of a large population of nanoparticles growing in a high-temperature environment through inter-particle collisions and coalescence. The coexistence of the three distinct mechanisms of the nanoparticle formation at the initial stage of the ablation process can be related to the broad nanoparticle size distributions commonly observed in nanosecond PLAL experiments. The strong dependence of the nanoparticle cooling and solidification rates on the location within the low-density metal-water mixing region has important implications for the long-term evolution of the nanoparticle size distribution, as well as for the ability to quench the nanoparticle growth or dope them by adding surface-active agents or doping elements to the liquid environment.
关键词： phase explosion,pulsed laser ablation in liquids,molecular dynamics simulations,hydrodynamic instability,atomistic simulations,nanoparticles,nucleation and growth
更新于2025-09-19 17:13:59
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Control of the size and luminescence of carbon nanodots by adjusting ambient pressure in laser ablation process
摘要： A femtosecond pulse laser was used to fabricate carbon nanodots (CDs), of which the particle size and photoluminescence (PL) properties could be effectively controlled by adjusting ambient pressure. By increasing the reaction pressure, the particle size of CDs gradually decreased and finally reached less than 1 nm at 4 MPa. Simultaneously, the fluorescence intensity of the CDs first increased and then decreased by further increasing the pressure. By examining the PL dynamics and the chemical structure of the CDs, we found that the PL change of products was attributed to the quantity change of functional groups attached to the CDs due to the surface area change of the carbonic core.
关键词： laser ablation,ambient pressure,photoluminescence,particle size,carbon nanodots
更新于2025-09-19 17:13:59
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Adsorption of Trans-Zeatin on Laser-Ablated Gold Nanoparticles for Transport into Plant Cells and Growth Stimulation
摘要： Gold nanoparticles can serve as nanovectors for trans-zeatin, a natural cytokinin used in plant culture to stimulate growth and bud formation. Here, we have used Raman scattering, X-ray Photoelectron Spectroscopy, UV-vis absorption, Transmission Electron Microscopy and Density Functional Theory calculations to explain the role of citrate anions in both the formation and the reactivity of the gold colloidal nanoparticles obtained by laser ablation and to go deeper inside into the interaction between metal and zeatin. In particular, the SERS (surface-enhanced Raman scattering) spectroscopy has been employed to study the adsorption of zeatin on different gold colloidal substrates. It is established that the molecule links to gold as tautomer N7(H), predominant in the aqueous suspension, in close similarity with adenine adsorbed on gold. Moreover, the laser ablation of a gold target in citrate solution allows obtaining small, stable and reactive Au nanoparticles, able to transport zeatin inside plant cells, where it can act as a growth hormone.
关键词： gold colloid,DFT,zeatin,laser ablation,SERS
更新于2025-09-19 17:13:59
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Lithography and Etchinga??Free Microfabrication of Silicon Carbide on Insulator using Direct UV Laser Ablationa??
摘要： This work presents a lithography and etching-free micro fabrication of SiC on insulator-based MEMS devices, employing a direct laser ablation. SiC micro-scale structures can be formed in one-step patterning with a remarkably fast speed, enabling rapid prototyping of a multifunctional SiC platform of temperature sensors, strain sensors, and micro heaters.
关键词： silicon carbide,force sensor,micro-heater,temperature sensor,laser ablation
更新于2025-09-19 17:13:59
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Femtosecond Laser Processing of Thick Film Cathodes and Its Impact on Lithium-Ion Diffusion Kinetics
摘要： Quantitative experiments of lithiation/delithiation rates were considered for a better understanding of electrochemical intercalation/deintercalation processes in laser structured thick film cathodes. Besides galvanostatic cycling for evaluation of specific discharge capacities, a suitable quantitative approach for determining the rate of Li-ion insertion in the active material and the rate of Li-ion transport in the electrolyte is expressed by chemical diffusion coefficient values. For this purpose, the galvanostatic intermittent titration technique has been involved. It could be shown that laser structured electrodes provide an enhanced chemical diffusion coefficient and an improved capacity retention at high charging and discharging rates.
关键词： diffusion coefficient,LiCoO2,lithium-ion batteries,3D battery,laser ablation
更新于2025-09-19 17:13:59