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Acoustic emission-based characterization of focal position during ultra-short pulse laser ablation
摘要： Microstructures were ablated using an ultra-short pulse laser system in order to investigate the influence of focal position on the surface topography. In addition, acoustic emissions measured by a piezoelectric sensor adapted to the AISI 4140 workpiece were analyzed and correlated with the focal position and the resulting surface topography. Frequency ranges sensitive to variations of the z-axis position were determined by STFT analysis. Subsequently, significant signal components were processed to enable an inference about the focal position. The hypothesis of assessing the focal position in-process based on acoustic emissions to ensure high precision during laser ablation could be confirmed.
关键词： modulation,time-frequency analysis,acoustic emission,laser ablation,focal position
更新于2025-09-12 10:27:22
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Study of various material particles by third harmonic generation method based on laser pulse induced plasma
摘要： Third harmonic generation (THG) from plasma can be used as probe radiation to characterize the plasma components. In this work, we present the study of the spatiotemporal profile of generated particles in various plasmas produced from bulk targets (C, Cr, In, Ni, Ag, CdS and ZnS) using pulsed laser ablation and THG using 800 nm, 40 fs probe pulses. The dependence of THG on the probe pulse intensity and the distance of the probe beam from the target position are analyzed. The influence of the ejected particle mass on THG with respect to the distance between the target and the probe pulses position was observed. The temporal evolution of THG depended on the delay between heating 6 ns pulses and driving 40 fs pulses. The variation of third harmonic intensity in the plasma components with atomic weight M on the delay (td) was consistent with the kinetic model described by relation td ∞ M0.5. THG from metal targets was mostly originated from the atomic and ionic components in plasma, whereas the clusters and heavier particles were responsible for this process in the case of ablated semiconductor materials.
关键词： Plasma,Laser ablation,Particle characterization,Third harmonic generation
更新于2025-09-12 10:27:22
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Laser‐Ablation Produced Cobalt‐Nickel Phosphate with High‐ValenceNickel Ions as Active Catalyst for Oxygen Evolution Reaction
摘要： Cost-effective, highly efficient and stable non-noble metal-based catalysts for oxygen evolution reaction (OER) are very crucial on energy storage and conversion. Here, we report an amorphous cobalt-nickel phosphate (CoNiPO4) containing considerable amount of high-valence Ni3+ specie as an efficient electrocatalyst for OER in alkaline solution. The catalyst was converted from Co-doped Ni2P through pulsed laser ablation in liquid (PLAL) and exhibits a large specific surface area of 162.5 m2/g and a low overpotential of 238 mV at 10 mA/cm2 with a Tafel slope of 46 mV/dec, being much lower than those of commercial RuO2 and IrO2. Our work demonstrates that PLAL is a powerful technology for generating amorphous CoNiPO4 with high-valence Ni3+, thus paving a new way towards highly effective OER catalysts.
关键词： OER,high valence state,cobalt-nickel phosphate,Pulsed laser ablation in liquid
更新于2025-09-12 10:27:22
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Effective size separation of laser-generated, surfactant-free nanoparticles by continuous centrifugation
摘要： High-power, nanosecond, pulsed-laser ablation in liquids enables the continuous synthesis of highly-pure colloidal nanoparticles (NPs) at an application-relevant scale. The gained mass-weighted particle size distribution is however often reported to be broad, requiring post treatment like centrifugation to remove undesired particle size fractions. To date, available centrifugation techniques are generally discontinuous, limiting the throughput and hindering economic upscaling. Hence, throughout this paper, a scalable, continuously operating centrifugation of laser-generated platinum nanoparticles in a tubular bowl centrifuge is reported for the first time. To that end, using a 121 W ns-laser, a continuous production of a colloidal suspension of NPs, yet with broad particle size distribution has been employed, yielding productivities of 1 - 2 g/h for gold, silver, and platinum. Subsequent downstream systematic study of relevant centrifugation parameters involved, effective size optimization and respective size sharpness parameters for a maximum Pt nanoparticle diameter of 10 nm are reported. The results of the experimental centrifugation of laser-generated Pt-NPs were in excellent agreement with the theoretically-calculated cut-off diameter. After centrifugation with optimized parameters, the polydispersity indices of the Pt-NPs size distributions were reduced by a factor of six and higher monodispersities were observed.
关键词： continuous process chain,tubular bowl centrifugation,contamination-free nanoparticle processing,Pt-NPs,pulsed laser ablation in liquids
更新于2025-09-12 10:27:22
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Laser Ablation of Polymers: A Review
摘要： Laser Ablation (LA), which employs a pulsed laser to remove materials from a substrate for generating micro/nano structures, has tremendous applications in the fabrication of metals, ceramics, glasses, and polymers. It has become a noteworthy approach to achieve different functional structures in engineering, chemistry, biological, medical and other fields. There are several parameters present during ablation, which affect the quality of the fabricated structures. Such parameters include laser sources, laser power, medium, and substrate materials. The objective of LA is to obtain high-quality, low-cost, repeatable, and reliable parts. This objective leads to plenty of attempts to control laser parameters on various types of materials. Polymers are one such class of materials, they can be melted and vaporized at high temperature during the ablation process. As a result, a number of polymers have been researched as candidate substrates in LA, and many different structures and patterns have been realized by this method. Based on previous works regarding LA, the current states of research and progress were reviewed from basic concept to optimal parameters, polymer types and applications. The significance of this paper is to provide a basis for follow-up research that leads to the development of superior materials and high-quality production through LA. In this review, we first introduced the basic concept of LA, including mechanism, laser types (millisecond, microsecond, nanosecond, picosecond, and femtosecond) and influential parameters (wavelength, repetition rate, fluence, and pulse duration). Then, we focused on several commonly used polymer materials (PTFE, PI, PDMS, PET, and PMMA) and compared them in detail, including the effects of polymer properties, laser parameters, and feature designs. Finally, we summarized the applications of various structures fabricated by LA in different areas along with a proposition of the challenges in this research area. Overall, a thorough review of laser ablation on several polymers has been presented, which could pave the way for characterization of future novel materials.
关键词： review,laser ablation,polymer
更新于2025-09-12 10:27:22
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Particle distribution in transient plasmas generated by ns-laser ablation on ternary metallic alloys
摘要： Understanding the fundamental mechanisms behind industrial laser-based technologies represents one the cornerstones of the development and tailoring of new materials. With the thin-film deposition using laser ablation being one of the most important techniques for obtaining complex materials with controllable stoichiometry, there is a high request for both experimental and theoretical studies towards understanding the behavior of multi-component alloys under high-power laser irradiation. Here we investigate the laser ablation process on two ternary metallic alloys (Cu–Mn–Al and Fe–Mn–Si) by means of space-and time-resolved optical emission spectroscopy and fast camera imaging with the focus being on the spatial distribution of each composing element. Information regarding the kinetic and thermal energy of the ejected particles is extracted and discussed in the framework of an inner structuring of the laser-produced plasmas based on a mass and energy distribution. The hypothesis is then verified by implementing a fractal analysis to the multi-component plasmas. The theoretical fractal approach offers results in good agreement with the experimental data gives important insight in the inner dynamics of complex laser-produced plasmas.
关键词： Ternary metallic alloys,Optical emission spectroscopy,Fractal analysis,Fast camera imaging,Laser ablation
更新于2025-09-12 10:27:22
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Copper nanoparticles obtained by laser ablation in liquids as bactericidal agent for dental applications
摘要： The dramatic increase of antibiotic-resistant bacteria is considered one of the greatest threats to human health at global scale. The antibacterial activity of noble metal nanoparticles, could be the solution against bacterial infectious diseases which currently do not respond to conventional treatments. In this work, copper nanoparticles were produced by laser ablation using two different lasers. A nanosecond laser operating at 532nm and a picosecond laser at 1064nm were used to ablate a copper target submerged in water and methyl alcohol. The obtained colloidal solutions consisted of copper oxide nanoparticles in suspension with diameters ranging from few nanometers to 45 nm. The nanoparticles formation process is highly influenced by laser parameters, but the solvent plays a crucial role on their characteristics. Cu oxide nanoparticles obtained in water present chain-like nanostructure, while those obtained in methyl alcohol are spherical with lower presence of oxide. All the obtained nanoparticles are crystalline and noticeably stable. Microbiology confirm their strong activity against Aggregatibacter actinomycetemcomitans. Cytocompatibility with human periodontal ligament stem cells is also confirmed. The biological assays evidence that ions release is not the main parameter responsible for the bactericidal activity of copper nanoparticles. Other factors such as oxidation state, size and crystallographic structure, have a greater influence on the process.
关键词： noble metal nanoparticles,laser ablation,copper nanoparticles,antibacterial effect
更新于2025-09-12 10:27:22
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Dual growth mode of boron nitride nanotubes in high temperature pressure laser ablation
摘要： The morphological analysis of the end of boron nitride nanotubes (BNNTs) using high-resolution transmission electron microscopy (HR-TEM) can provide valuable insight into the growth mechanism in high temperature pressure (HTP) laser ablation where the best quality of BNNT materials can be obtained so far. Two growth modes of BNNT coexisting during the synthesis process have been proposed based on HR-TEM observation and length analysis. One is the root growth mode, in which boron nitride (BN) species formed via the surface interaction between surrounding N2 molecules and boron nanodroplets incorporate into the tubular structure. Another mode called open-end growth mode means the prolongation of tube growth from the exposed BN edge surrounding the surface of boron nanodroplets which is constructed by the heterogeneous nucleation of absorbed BN radicals from the gas plume. The statistical data, the proportions of end structures and the length of BNNTs, could be fitted to two growth modes, and the open-end growth mode is found to be especially effective in producing longer nanotubes with a higher growth rate. The scientific understanding of the growth mechanism is believed to provide the control for optimized production of BNNTs.
关键词： growth mechanism,high temperature pressure laser ablation,open-end growth mode,root growth mode,boron nitride nanotubes,HR-TEM
更新于2025-09-12 10:27:22
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Growth of multi-morphology amorphous silicon oxycarbide nanowires during the laser ablation of polymer-derived silicon carbonitride
摘要： Multi-morphology amorphous SiOC nanowires were successfully prepared within the interfacial interstices between the una?ected SiCN ceramic and the bracket during the laser ablation of polymer-derived SiCN ceramic in a low-pressure argon atmosphere. Laser irradiation experiments were performed using a continuous-wave CO2 laser, and the gas source for the growth of amorphous SiOC nanowires was provided by the laser ablation of the SiCN ceramic. X-ray photoelectron spectroscopy shows that the amorphous SiOC nanowires possess a SiO2 dominated nanostructure, and the formation of amorphous SiOC nanowires is attributed to the good di?usivity of CO in SiO2. The morphologies of the amorphous SiOC nanowires include straight nanowires, beaded nanowires, helical nanowires, and branched nanowires, and these are determined by the ?owing state of the reactant gases, the laser power, and the surface morphology of the SiCN ceramics. Each amorphous SiOC nanowire with speci?c morphology can be uniformly distributed in separate regions, which makes it possible to control the growth of amorphous SiOC nanowires in di?erent morphologies.
关键词： Laser ablation,SiOC,Polymer-derived ceramics,Amorphous nanowires,Multi-morphology
更新于2025-09-12 10:27:22
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PVP-assisted laser ablation growth of Ag nanocubes anchored on reduced graphene oxide (rGO) for efficient photocatalytic CO2 reduction
摘要： Metallic nanoparticles loaded graphene nanocomposites have been widely studied for various scienti?c and technological applications. In this study, a facile method was reported to realize a straightforward growth of shape and size-controllable of metallic nanoparticles, and the subsequent hybridization with graphene in solution by strategically coupling wet-chemical route and laser ablation. By mixing graphene oxide (GO) with a tunable concentration level of polyvinylpyrrolidone (PVP) in aqueous solution, Ag nanocubes with a face-centered cubic crystal structure were generated by pulsed laser ablation and then mounted on GO nanosheets with the assistance of PVP. The preferential adsorption of PVP to Ag (100) crystal face led to the production of Ag nanocubes with exposed (100) facet. The result showed that the morphological yield of spherical particles decreased with the increase in PVP concentration. X-ray di?raction (XRD) and UV–visible spectroscopy analyses con?rmed that GO was partially reduced. In the reduction of CO2 gas, the photocatalytic conversion rate could achieve 133.1 μmol g?1 in 6 hrs for cubic Ag-loaded reduced GO composites.
关键词： Ag nanocubes,PVP,Laser ablation,CO2 reduction,Photocatalysis,Graphene oxide
更新于2025-09-12 10:27:22