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Spatial confinement effects of bubbles produced by laser ablation in liquids
摘要： The paper deals with the influence of the spatial confinement on the evolution of laser bubbles and shock waves by means of the shadowgraphy technique. Due to the constraint of walls, the bubble center shrinks faster than the bubble edge and collapses before the edge of the bubble, splitting into left and right small bubbles that continue to shrink down. The result validates that the Bjerknes force has little effect on bubble evolution at the expansion stage but a great influence on it at the collapse stage. We study the evolution of laser bubbles with different Al-plate intervals for displaying a gradual transition from constrained conditions to unconstrained conditions. In addition, we describe the dynamics of the first bubble at the expansion stage using the Rayleigh-Plesset equation. The pressure and temperature inside laser bubbles are calculated in the meanwhile.
关键词： spatial confinement,Rayleigh-Plesset equation,shock waves,laser ablation,bubbles
更新于2025-09-16 10:30:52
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Morphology-selective preparation and formation mechanism of few-layer graphene on Cu substrate by liquid-phase pulsed laser ablation
摘要： This paper presented a morphology-selective preparation and formation mechanism of few-layer graphene (FLG) on a Cu substrate by pulsed laser ablation in liquid. It is a simple and controllable route to grow FLG directly on the surface of a copper foil at ambient temperature and normal pressure, which does not need other precursor materials. FLG with 3–10 layers of thickness and continuous hundreds of micrometers in lateral size is obtained. The morphology and structure of FLG were investigated by using a Raman spectrometer, scanning electron microscope, high-resolution transmission electron microscope, and atomic force microscope. The formation mechanism of FLG and the role of the plasma-produced carbon species are put forward based on the interaction between the laser, material, and substrate. Our finding, the direct deposition of FLG on the Cu substrate by pulsed laser ablation in liquid, will open a door to apply this green route to the production of FLG with controlled morphology.
关键词： formation mechanism,Cu substrate,morphology-selective preparation,few-layer graphene,liquid-phase pulsed laser ablation
更新于2025-09-16 10:30:52
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Comparison thermochemical and thermophysical performances analysis in laser processing by dynamic heat-matter diffusion coupling simulation and corresponding experiment validation
摘要： The laser-matter interaction contains complex thermophysical and thermochemical responses. The variation of energy and composition happen in thermophysical and thermochemical process will totally change the interaction behaviors. In order to obtain an accurate mechanism and promote the understanding of laser-matter interaction, all thermophysical and thermochemical responses, especially the thermochemical part, should be considered and investigated. In this study, a coupled heat-matter diffusion model based on thermodynamic chemical equilibrium finite-element method and thermochemical ablation theory was established. The materials with complex reaction enthalpy change in high temperature environment were chosen to validate the model. The results show that this model is accurate, as the maximum error of back-surface temperature response is just 4.0% between experimental and calculation values. The detailed variations of composition, temperature and optical reflection were obtained and analyzed, which is in good agreement with the experiment. This coupled heat-matter diffusion model including all thermophysical and thermochemical response has the great potential in nearly all laser-matter interaction involved application.
关键词： Coupled heat-matter diffusion method,Laser ablation,Graphite/SiO2 composite,Carbothermic reaction,Finite-element
更新于2025-09-16 10:30:52
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AIP Conference Proceedings [AIP Publishing INTERNATIONAL CONFERENCE ON SCIENCE AND APPLIED SCIENCE (ICSAS) 2019 - Surakarta, Indonesia (20 July 2019)] INTERNATIONAL CONFERENCE ON SCIENCE AND APPLIED SCIENCE (ICSAS) 2019 - Effect of solvent in the synthesis of colloidal copper nanoparticles by pulse laser ablation method
摘要： Effect of solvent in the synthesis of colloidal copper nanoparticles by pulse laser ablation method
关键词： pulse laser ablation,solvent effect,colloidal copper nanoparticles
更新于2025-09-16 10:30:52
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Experimental Investigation on the Spatial-temporal Evolution of the hole formation during Laser Helical Drilling
摘要： In order to study the influence of process parameters of femtosecond laser helical machining on the formation of micro-holes, we selected main parameters of the femtosecond laser helical drilling process, used 304 stainless steel as the target material, designed a 5-factor and 5-level orthogonal experiment based on the orthogonal table, and analyzed the significance levels of the impacts of single pulse energy, repetition rate, rotation rate, rate of focus downward movement, and air-blowing pressure on the ablation depth. Based on back propagation (BP) neural network, we established the relationship model between five factors and the material ablation depth, and trained the network with orthogonal experiment data. We used the data of the additional drilling experiments to test the generalization ability of the established network, and the results show that the prediction error of the model is within 3%. We designed a single-factor experiment for the characteristic parameter of the helical drilling--the rate of focus downward movement--and obtained the effect of the rate of focus downward movement on the formation of the micro-holes during the process of femtosecond laser helical drilling.
关键词： femtosecond laser,ablation depth,helical drilling,micro-holes,BP neural network
更新于2025-09-16 10:30:52
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Effect of substrate temperature, laser energy and post-deposition annealing on the structural, morphological and optical properties of laser-ablated perovskite BaSnO3 films
摘要： Perovskite BaSnO3 thin films suitable for excitonic solar cell applications were deposited on quartz substrate by pulsed-laser ablation method. The effect of various deposition parameters on the structural, morphological and optical properties is systematically studied by various characterization techniques. Phase-pure films with cubic crystalline nature were evolved at a substrate temperature of 600 °C with a laser energy of 60 mJ and post-deposition annealing further improved the structural purity and optical quality of the films. An exponential growth in film thickness was observed with increasing laser energy in which Stranski–Krastnov growth mechanism dominated. Chemical states of BaSnO3 were confirmed from XPS analysis. The deposited films present luminescence in the visible region at 452 nm, 480 nm and 580 nm wavelength.
关键词： Optical properties,BaSnO3,Thin films,Pulsed-laser ablation,Perovskite
更新于2025-09-16 10:30:52
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Metallic Nanoparticles Generation by Repetitive Pulsed Laser for Applications in Bio-Medicine
摘要： An Nd:YAG pulsed laser operating at the 1064 nm wavelength, the 3 ns pulse duration, the 1010 W/cm2 intensity and the 10 Hz repetition rate is employed to irradiate biocompatible metallic targets based on Au, Bi and Ag placed in water. The laser-matter interaction produces nanometric spherical particles. The concentration of the solution with nanoparticles is controllable by the laser parameters, the ablative emission process, the irradiation time and the water’s volume. Generally, nanoparticles of about 10 nm in size and concentrations of the order (0.1 ÷ 10) mg/ml are prepared to be injected in cell cultures or in living systems (mice). The nanoparticles introduction in the extra and intracellular cellular liquids improves the bio-imaging of the tissue and organs by using ?uorescence techniques. Moreover, if these nanoparticles are concentrated in tumour cells, they make possible high e?ciency radio-therapy and thermal-therapy treatments, as it will be presented and discussed.
关键词： imaging,therapy,Laser ablation in water,nanoparticles
更新于2025-09-16 10:30:52
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Pressure effect on optical and structural properties of ZnMnO thin films grown by pulsed laser deposition
摘要： Zn0.95Mn0.05O thin films were deposited on Si substrate by pulsed laser ablation technique under different oxygen pressure. The structural and optical properties of the films were analyzed as a function of the oxygen gas pressure. The Mn concentration and the substrate temperature of the thin films were kept constant at 5 wt% and 200°C respectively. X-ray diffraction technique (XRD), atomic force spectroscopy (AFM), raman spectroscopy and UV-Vis were employed to characterize the optical properties and the crystalline structure of the films. The diffraction patterns revealed that the Mn0.05Zn0.95O thin films were polycrystalline with the wurtzite hexagonal structure of ZnO and highly oriented in c-axis direction, without any secondary phases. The average energy band gap of the films was evaluated around 3.23-3.56 eV. Raman spectrum showed E2 (low) mode of ZnO structure shifted to red and increased its FWHM.
关键词： Laser Ablation,X-ray Diffraction,UV-Vis Spectroscopy,Atomic Force Microscopy,Raman Spectroscopy
更新于2025-09-16 10:30:52
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Laser-induced anchoring of WO3 nanoparticles on reduced graphene oxide sheets for photocatalytic water decontamination and energy storage
摘要： In this work, the synthesis of tungsten oxide/reduced graphene oxide (WO3-rGO) nanocomposite, using a simple method of pulsed laser ablation in liquids (PLAL) is reported. The pulsed laser beam of 355 nm wavelength carries out two simultaneous processes: the reduction of graphene oxide and at the same time the anchoring of nanostructured WO3 on reduced graphene oxide. In the photo-catalytic application, WO3-rGO shows much better visible light absorption and less photo-generated charge recombination than pure WO3, as indicated by optical absorption and photoluminescence spectra. These improved features in WO3-rGO significantly enhanced the photo-catalytic decontamination of methylene blue (MB) dye in the water, compared to the use of pure WO3 as a photocatalyst. A Poly 2-acrylamido-2-methyl-1-propanesulfonic acid (PAMPS) based electrolyte together with the high electrical conductance and porosity of rGO which were produced after anchoring WO3 on the graphene oxide, were harnessed for the energy storage application using this material for a supercapacitor. The specific capacitance for WO3-rGO based device is achieved to be 577 F g?1 measured by the galvanostatic charge-discharge (GCD) method. Also, at a power density of 1000 W kg?1, the as-synthesized WO3-rGO demonstrated a large energy density value of 76.3 Wh Kg?1 that is much larger than obtained, using WO3 alone. Besides these photocatalytic and energy storage performance evaluation of WO3-rGO, the optical, morphological and elemental characteristics of synthesized WO3-rGO were also investigated to study the improved performance of the nanocomposite in these two applications.
关键词： PAMPS,Supercapacitor,Pulsed laser ablation in liquid,Energy storage,Photo-catalytic decontamination
更新于2025-09-16 10:30:52
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Controlled Nitrogen Doping of Graphene Quantum Dots Through Laser Ablation in Aqueous Solutions for Photoluminescence and Electrocatalytic Applications
摘要： Nitrogen-doped graphene quantum dots (N-GQDs) have promising applications in catalysis and photoluminescence, but many existing synthetic methods require uses of harsh chemicals, long reaction times, and complicated purification steps and have poor control over the surface functional groups. Laser ablation in liquid (LAL) is a promising alternative method to prepare nanomaterials because of its fast production, use of fewer chemicals, simple purification, and fewer byproducts and its control of the product by precise tuning of laser ablation parameters. We report the use of LAL to produce N-GQDs from carbon nano-onions in aqueous solutions of ammonia, ethylenediamine, and pyridine. The choice of these dopants allowed for tuning the overall nitrogen content and the distribution of functional groups that led to the control over the photoluminescence emission wavelengths and lifetimes. High concentrations of amine groups tended to red shift emission and exhibit shorter lifetimes, whereas pyridinic groups would blue shift the emission and exhibit longer lifetimes. The N-GQDs also showed a promising performance as electrocatalysts for reducing oxygen to hydrogen peroxide, an important chemical widely used in industrial applications. The N-GQDs exhibited both low overpotentials and high selectivity for a two-electron oxygen reduction pathway.
关键词： electrocatalysis,photoluminescence,lifetime,laser ablation in liquid,oxygen reduction reaction,Graphene quantum dots
更新于2025-09-16 10:30:52