Metal Ablation Research Articles

Modification of nanoparticles synthesized during ablation of metals in water using nanosecond, picosecond, and femtosecond pulses

We show that the pulse duration of laser radiation used for metal ablation in water affects the nanoparticle morphology over a two-month aging period. Aluminum, copper, indium, and zinc spherical nanoparticles evolved into the elliptical, triangular, seed-like, rod-like, and rectangular forms. The most effective transformation of spherical nanoparticles into nonspherical shapes occurred with picosecond pulse ablation. Spectral analysis of the aged nanoparticle suspensions revealed changes in both the visible and UV ranges. Our study showed the correlation between the suppression of the surface plasmon resonances of the suspensions of aged nanoparticles and modification of spherical structures toward the nonspherical nano- and microparticles.

Metal Material Processing Using Femtosecond Lasers: Theories, Principles, and Applications.

Metal material processing using femtosecond lasers is a useful technique, and it has been widely employed in many applications including laser microfabrication, laser surgery, and micromachining. The basic mechanisms of metal processing using femtosecond lasers are reviewed in this paper and the characteristics and theory of laser processing are considered. In addition to well-known processes, the recent progress relating to metals processing with femtosecond lasers, including metal material drilling, metal ablation thresholds, micro/nano-surface modification, printed circuit board (PCB) micromachining, and liquid metal (LM) processing using femtosecond lasers, is described in detail. Meanwhile, the application of femtosecond laser technology in different fields is also briefly discussed. This review concludes by highlighting the current challenges and presenting a forward-looking perspective on the future of the metal laser processing field.

Influence of surface ablation on plasma and its interaction with electromagnetic field

Surface ablation significantly affects the distribution of plasma in high-speed flow and the characteristics of its interaction with electromagnetic fields. Considering the mechanism of ablation and ejection on the surface of hypersonic vehicle, the participation of ablation products in the plasma generating process in the flow field, the conduction mechanism of mixed ionized gas containing alkali metal and the electromagnetic dynamics mechanism, the coupled calculation method of high-speed flow/plasma/electromagnetic field with alkali metal ablation is established by solving the three-dimensional thermochemical non-equilibrium flow governing equation with electromagnetic source term, the electric field Poisson equation and the magnetic vector Poisson equation. Combined with the common ablation and pyrolysis process of carbon-carbon materials and silicon-based phenolic resin materials, the mechanism and law of the interaction between surface ablation and electromagnetic field on the hypersonic plasma sheath under various conditions are systematically studied. The results show that the ablation effect affects the plasma distribution in the flow field, which is affected by the ablation mass ejection rate and the mass proportion of alkali metal. When the alkali metal content is high, the alkali metal ionization reaction is dominant, and the electron number density can increase by 1–2 orders of magnitude. The influences of different materials on plasma are different. The mass ejector ratio of silicon-based phenolic resin is larger, and the molar concentration of CO<sup>+</sup> and C<sup>+</sup> produced by ionization is close to that of NO<sup>+</sup> and <inline-formula><tex-math id="Z-20240520210947">\begin{document}${\mathrm{O}}_2^+ $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20231733_Z-20240520210947.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20231733_Z-20240520210947.png"/></alternatives></inline-formula>, which cannot be ignored. Alkali metal in ablative material can significantly improve the control effect of magnetohydrodynamics. With the increase of the proportion of alkali metal, the coupling effect of electromagnetic field increases, and the relationship between them is nonlinear. When the speed is low, the ionization degree of air itself is low and the coupling effect of electromagnetic field is weak. But the efficiency of “improving the electromagnetic effect by ablation of alkali metal” is higher.

Picosecond Pulsed Laser Deposition of Metals and Metal Oxides.

In this work, we present the fabrication of thin films/nanostructures of metals and metal oxides using picosecond laser ablation. Two sets of experiments were performed: the depositions were carried out in vacuum and in air at atmospheric pressure. The subjects of investigation were the noble metals Au and Pt and the metal oxides ZnO and TiO2. We studied and compared the phase composition, microstructure, morphology, and physicochemical state of the as-deposited samples' surfaces in vacuum and in air. It was found that picosecond laser ablation performed in vacuum led to the fabrication of thin films with embedded and differently sized nanoparticles. The implementation of the same process in air at atmospheric pressure resulted in the fabrication of porous nanostructures composed of nanoparticles. The ablation of pure Pt metal in air led to the production of nanoparticles with an oxide shell. In addition, more defects were formed on the metal oxide surface when the samples were deposited in vacuum. Furthermore, the laser ablation process of pure Au metal in a picosecond regime in vacuum and in air was theoretically investigated using molecular dynamics simulation.

A comparative study of cerium oxides formed by pulsed laser ablation and continuous wave laser heating

AbstractThe formation of Ce2O3 from cerium metal requires complex reducing conditions. Alternatively, we show that different stoichiometries and structures of cerium oxides can be generated in high‐temperature laser experiments by varying the availability of oxygen and the use of either pulsed laser ablation (PLA) or continuous wave (CW) laser heating of cerium metal. X‐ray diffraction and Raman spectroscopy suggest that a low structural order Ce2O3/CeO2 mixed structure is formed in a 1% O2 atmosphere with PLA. For CW heating in a 1% O2 environment, Raman measurements show the formation of crystalline A‐type Ce2O3 in proximity to the point of laser impingement. These experiments were repeated in 18O2 and allowed us to report for the first time the corresponding Raman spectrum of Ce218O3.

Microscopic mechanism of ultrashort-pulse laser ablation of metals: a molecular dynamics study incorporating electronic entropy effects

The microscopic mechanism of metal ablation induced by ultrashort laser pulse irradiation is investigated. A two-temperature model scheme combined with molecular dynamics (TTM-MD) is developed to incorporate electronic entropy effects into the simulation of metal ablation while satisfying the energy conservation law. Simulation with the TTM-MD scheme reveals that ultrashort laser pulse irradiation near the ablation threshold causes high-energy atom/ion emission and sub-nanometer depth ablation, as observed experimentally, due to the electronic entropy effect. It is also shown that the electronic entropy effect is also significant in spallation.

Two-temperature molecular dynamics simulation study of copper thin film irradiation with femtosecond and picosecond laser pulses

Metal targets irradiated with laser pulses have a wide range of applications in thin film preparation, nanomaterial synthesis, bio-medical imaging, and metal ablation. Here, using two-temperature model based molecular dynamics simulation, we investigate laser mediated ablation in copper. Ablation of the film starts with the formation of voids within it. This void forming mechanism at low laser fluences (≤100 mJ/cm2) is studied using both picosecond and femtosecond pulses. At the same fluence, shorter laser pulse transfers more energy to the atoms generating temperatures greater than the melting temperature of the crystal. This increases the kinetic energy of the atoms and they start vibrating with different velocities. If these vibrations cross a threshold of 5 Å per picosecond (500 m/s), voids and faults start appearing in the system. At the same fluence, higher concentration of voids are also created at a faster rate with the femtosecond pulse.

A Peridynamic Approach for the Evaluation of Metal Ablation under High燭emperature

In this paper, the evaluations of metal ablation processes under high temperature, i.e., the Al plate ablated by a laser and a heat carrier and the reactor pressure vessel ablated by a core melt, are studied by a novel peridynamic method. Above all, the peridynamic formulation for the heat conduction problem is obtained by Taylor’s expansion technique. Then, a simple and efficient moving boundary model in the peridynamic framework is proposed to handle the variable geometries, in which the ablated states of material points are described by an additional scalar field. Next, due to the automatic non-interpenetration properties of peridynamic method, a contact algorithm is established to determine the contact relationship between the ablated system and the additional heat carrier. In addition, the corresponding computational procedure is listed in detail. Finally, several numerical examples are carried out and the results verify the validity and accuracy of the present method.

UV-laser-machined stretchable multi-modal sensor network for soft robot interaction

Soft robotic hands can facilitate human–robot interaction by allowing robots to grasp a wide range of objects safely and gently. However, their performance has been hampered by a lack of suitable sensing systems. We present a flexible and stretchable multi-modal sensor network integrated with a soft robotic hand. The design of wired sensors on a flexible metalized film was embodied through a manufacturing approach that uses both UV laser metal ablation and plastic cutting simultaneously to create sensor electrode and stretchable conductive wires in a Kirigami pattern into a single network. We evaluated the interconnects and sensors by measuring an impedance change to each external stimulus and showed that are not substantially affected by stretching the network. With the sensor sheet wrapped around a soft robotic gripper, we demonstrated several interaction scenarios, including a warm burrito for food handling, and a warm baby doll for medical applications.

Laser shock wave propagation in a 3D woven composite material

We investigate the propagation of a laser shock wave within a composite material used in aeronautics. This one is made of carbon fibers woven according to a 3D pattern within an epoxy matrix. The shock wave is generated by an impulsive (of order 10 ns) laser beam of power a few GW/cm², focused on the surface of a metallic layer attached to the composite. The metallic surface ablation results in an expanding plasma inducing a shock wave in the material with a peak stress of a few GPa. Its propagation can be measured by the velocity of the opposite surface of the sample detected by laser interferometry. The high frequency content of the signal and the heterogeneous and anisotropic behavior of the material induce a complex propagation. A measurement campaign has been performed for different samples. A 2D numerical model has been developed based on a finite difference discretisation of equations of linear elastodynamics for the propagation part, combined with a nonlinear model of the source. Sample geometry and fiber orientations are obtained from analysis of the images of transversal cuts of the samples. Experimental data are statistically compared to the model and discussed.

Sustainable removal of nitrite waste to value-added ammonia on Cu@Cu2O core–shell nanostructures by pulsed laser technique

The biochemical reduction of nitrite (NO2−) ions to ammonia (NH3) requires six electrons and is catalyzed by the cytochrome c NO2− reductase enzyme. This biological reaction inspired scientists to explore the reduction of nitrogen oxyanions, such as nitrate (NO3−) and NO2− in wastewater, to produce the more valuable NH3 product. It is widely known that copper (Cu)-based nanoparticles (NPs) are selective for the NO3− reduction reaction (NO3−RR), but the NO2−RR has not been well explored. Therefore, we attempted to address the electrocatalytic conversion of NO2− to NH3 using Cu@Cu2O core–shell NPs to simultaneously treat wastewater by removing NO2− and producing valuable NH3. The Cu@Cu2O core–shell NPs were constructed using the pulsed laser ablation of Cu sheet metal in water. The core–shell nanostructure of these particles was confirmed by various characterization techniques. Subsequently, the removal of NO2− and the ammonium (NH4+)−N yield rate were estimated using the Griess and indophenol blue methods, respectively. Impressively, the Cu@Cu2O core–shell NPs exhibited outstanding NO2−RR activity, demonstrating a maximum NO2− removal efficiency of approximately 94% and a high NH4+-N yield rate of approximately 0.03 mmol h−1.cm−2 at −1.6 V vs. a silver/silver chloride reference electrode under optimal conditions. The proposed NO2−RR mechanism revealed that the (111) facet of Cu favors the selective conversion of NO2− to NH3 via a six-electron transfer. This investigation may offer a new insight for the rational design and detailed mechanistic understanding of electrocatalyst architecture for the effective conversion of NO2− to NH4+.

Juxtametallic Bipolar Bone Radiofrequency Ablation: Thermal Monitoring in an Ex-Vivo Model with Specimen MRI and Histopathologic Correlation

PurposeTo measure the ablation zone temperature and nontarget tissue temperature during radiofrequency (RF) ablation in bone containing metal instrumentation versus no metal instrumentation (control group). Materials and MethodsEx vivo experiments were performed on 15 swine vertebrae (control, n = 5; titanium screw, n = 5; stainless steel screw, n = 5). Screws and RF ablation probe were inserted identically under fluoroscopy. During RF ablation (3 W, 5 minutes), temperature was measured 10 mm from RF ablation centerpoint and in muscle contacting the screw. Magnetic resonance (MR) imaging, gross pathologic, and histopathologic analyses were performed on 1 specimen from each group. ResultsAblation zone temperatures at 2.5 and 5 minutes increased by 12.2 °C ± 2.6 °C and 21.5 °C ± 2.1 °C (control); 11.0 °C ± 4.1 °C and 20.0 °C ± 2.9 °C (juxta-titanium screw), and 10.0 °C ± 3.4 °C and 17.2 °C ± 3.5 °C (juxta–stainless steel) screw; differences among groups did not reach significance by analysis of variance (P = .87). Mixed-effects linear regression revealed a statistically significant increase in temperature over time in all 3 groups (4.2 °C/min ± 0.4 °C/min, P < .001). Compared with the control, there was no significant difference in the temperature change over time for titanium (−0.3 °C/min ± 0.5 °C/min, P = .53) or steel groups (−0.4 °C/min ± 0.5 °C/min, P = .38). The mean screw temperature at the final time point did not show a statistically significant change compared with baseline in either the titanium group (−1.2 °C ± 2.3 °C, P = .50) or steel group (2.6 °C ± 2.9 °C, P = .11). MR imaging and pathologic analyses revealed homogeneous ablation without sparing of the peri-hardware zones. ConclusionsAdjacent metallic instrumentation did not affect the rate of or absolute increase in temperature in the ablation zone, did not create peri–metallic ablation inhomogeneities, and did not result in significant nontarget heating of muscle tissue in contact with the metal instrumentation.

Synthesis and optical characteristics of silver nanoparticles produced by laser ablation of metal in liquid

The process of silver ablation in water by high-power laser pulses (λ = 1064 nm, τ = 20 ns) in the power density range from 2.6 ⋅ 108 to 5.5 ⋅ 108 W/cm2 has been investigated. The dependences of the ablation efficiency and the size distribution of silver nanoparticles on the power density of laser radiation and on the duration of synthesis have been determined. It was found that the resulting nanoparticles have a multimodal size distribution, in which three fractions with average sizes of 5; 50 and more than 100 nm can be distinguished. Particles with a diameter of more than 100 nm are formed as a result of the removal of the liquid-droplet phase directly from the target surface due to the hydrodynamic mechanism, particles 5 and 50 nm in size are formed due to condensation at different stages of cooling of the vapor-plasma formation. The proportion of these fractions in the silver sol is determined by the effective density of the laser power on the target surface. It is shown that pulsed laser irradiation of a sol of silver nanoparticles after the completion of the synthesis process makes it possible to significantly narrow the particle size distribution and increase the stability of the resulting suspension. It was found that the synthesised silver nanoparticles deposited on a silicon substrate can effectively enhance the Raman signal of human serum albumin.

Efficient modeling of metal ablation irradiated by femtosecond laser via simplified two-temperature model coupling molecular dynamics

A simplified two-temperature model coupling molecular dynamics (TTM-MD) method is proposed to study the femtosecond laser ablation of metal, which can simulate a micron-sized laser spot irradiation under the premise of atomic-level calculation accuracy. The theoretical TTM-MD model is re-derived using the Langevin equation to reduce the calculation frequency of lattice temperature and improve the solution efficiency. Then, the TTM-MD simulation model is simplified to a one-dimensional model according to the rotational symmetry of laser spot and neglecting the lateral heat transfer. The temperature variation, pressure evolution, and void nucleation are analyzed to reveal the spallation and explosion ablation regimes. The variation of simulated ablation depth with laser fluence is consistent with the experimental results. The full-sized crater profiles predicted by this simplified model also match well with the ablation experiments irradiated by the Gaussian laser spot. Moreover, the step boundary caused by the threshold effect of laser ablation also can be captured on the crater edge. These results suggest that the proposed model provides essential insight into the femtosecond laser ablation by avoiding the limitation of current computing power.

Streamlined plug-in aerosol prototype for reconfigurable manufacture of nano-drug delivery systems

The significant advances in nano-drug delivery systems (NDDS) for anticancer agents have led to the development of computational techniques, such as machine learning and neural networks to identify the optimal architectural and compositional design in a wide variety of therapeutic nanoformulations. On the other hand, few studies have examined downsized plug-in reaction-ware embodied in an autonomous platform for the instant reconfigurable production of engineered nanomaterials to guide optimal NDDS designs and delivery strategies. This paper describes an on-demand system for an electrically operable, continuously processible material produced by sequential spray pyrolysis and vibrating spray for single-pass NDDS assembly. In particular, a mild chemotherapeutic NDDS consisting of amorphous boron nitride (a-BN; a stable base material for loading), doxorubicin (DOX; an anticancer drug), and folic acid-chitosan conjugate (FACHI; a targeting and antiopsonic agent), called a-BN-DOX@FACHI, was fabricated using the developed system. a-BN-DOX@FACHI was assessed for the pH-responsive release of DOX, targeting of the folate receptor, and its resistance to opsonization and macrophage phagocytosis. a-BN-DOX@FACHI was found to be a mild cancer chemotherapeutic with reasonable biosafety. Integrating a metal ablation device with the developed on-demand system enabled the reconfiguration of NDDS from a-BN-DOX@FACHI to a-BN-Au-DOX@FACHI or a-BN-Pt-cisplatin@bovine serum albumin to add a photothermal effect with a range of architectures and compositions.

Spatiotemporal evolution of the morphology of multi-pulse laser ablated metals considering plasma shielding

With the laser ablation of metals, ultrafast lasers have high peak power density and significant nonlinear absorption, but plasma shielding and large taper often exist during ablation, which seriously affects the quality and efficiency of ablation. In this paper, the heat conduction equation of the lattice system is rewritten into the dual-temperature model, the time and space terms in the femtosecond laser source equation are superimposed to calculate, and the plasma shielding effect is incorporated into the ablation model using multi-pulse laser ablation iterative calculations. The constructed 3D improved dual-temperature model uses the finite difference method to investigate the spatio-temporal evolution of the ablation morphology of the metal target under the influence of different laser parameters using the critical point phase separation mechanism. In the numerical simulation, the error of considering plasma shielding is controlled within 8.24% compared with that of not considering plasma shielding, the ablation process has obvious layering phenomenon, the actual ablation experimental results are basically consistent with the calculation results of the proposed model, and the prediction error of the ablation depth can be controlled within 13.28%, which indicates that the model proposed in this paper has the ability to more accurately describe the spatial and temporal evolution of metal ablation by femtosecond laser.

The effect of oxygen concentration on the speciation of laser ablated uranium

In order to model the fate and transport of particles following a nuclear explosion, there must first be an understanding of individual physical and chemical processes that affect particle formation. One interaction pertinent to fireball chemistry and resultant debris formation is that between uranium and oxygen. In this study, we use laser ablation of uranium metal in different concentrations of oxygen gas, either 16O2 or 18O2, to determine the influence of oxygen on rapidly cooling uranium. Analysis of recovered particulates using infrared absorption and Raman spectroscopies indicate that the micrometer-sized particulates are predominantly amorphous UOx (am-UOx, where 3 ≤ x ≤ 4) and UO2 after ablation in 1 atm of pure O2 and a 1% O2/Ar mixture, respectively. Energy dispersive X-ray spectroscopy (EDS) of particulates formed in pure O2 suggest an O/U ratio of ~ 3.7, consistent with the vibrational spectroscopy analysis. Both am-UOx and UO2 particulates convert to α-U3O8 when heated. Lastly, experiments performed in 18O2 environments show the formation of 18O-substituted uranium oxides; vibrational frequencies for am-U18Ox are reported for the first time. When compared to literature, this work shows that cooling timescales can affect the structural composition of uranium oxides (i.e., crystalline vs. amorphous). This indicator can be used in current models of nuclear explosions to improve our predicative capabilities of chemical speciation.

Magnesium Nanoparticle Synthesis from Powders via Pulsed Laser Ablation in Liquid for Nanocolloid Production

Magnesium nanoparticles of various mean diameters (53–239 nm) were synthesised in this study via pulsed laser ablation in liquid (PLAL) from millimetre sized magnesium powders within isopropyl alcohol. It was observed via a 3 × 3 full factorial design of experiments that the processing parameters can control the nanoparticle distribution to produce three size-distribution types (bimodal, skewed and normal). Ablation times of 2, 5, and 25 min where investigated. An ablation time of 2 min produced a bimodal distribution with the other types seen at higher periods of processing. Mg nanoparticle Ultraviolet–Visible spectroscopy (UV–Vis) absorbance at 204 nm increased linearly with increasing ablation time, indicating an increase in nanoparticle count. The colloidal density (mg/mL) generally increased with increasing nanoparticle mean diameter as noted via increasing UV–Vis absorbance. High laser scan speeds (within the studied range of 3000–3500 mm/s) tend to increase the nanoparticle count/yield. For the first time, the effect of scan speed on colloidal density, UV–Vis absorbance and nanoparticle diameter from metallic powder ablation was investigated and is reported herein. The nanoparticles formed dendritic structures after being drop cast on aluminium foil as observed via field emission scanning electron microscope analysis. Dynamic light scattering was used to measure the size of the nanoparticles. Magnesium nanoparticle inks show promise for use in the fabrication conductive tracks or thermal insulation in electronics.

Study on real-time z-scanning of multiple-pulse laser ablation of metal applied in roll-printed electronics

The interaction between a metal surface and multiple pulses was investigated to achieve optimal focusing conditions during ultrashort laser ablation. We report a simple theoretical expression of morphological changes in the ablated channel and demonstrate its advantage in positioning the interactive surface at the focus in real time during multiple-pulse laser ablation of a metallic material. Experimental results on the ablation depth for zinc, nickel, and copper show that the combination of a dynamic focusing system and a theoretical formula of ablation-cycle-dependent ablation depth enables one to control the shape of ablated channels. This model can be applied to a variety of high-efficiency ablation systems and may play an essential role in the development of a high-precision ablation system for the curved surfaces in highly scaled metal gravures used in printed electronics, which currently present challenges for engineers and technicians.

Linear and nonlinear optical studies of Ag/Zn/ZnO nanocomposite thin film prepared by pulsed laser deposition technique

Pulsed laser deposition technique was used to produce Zn/ZnO thin film and Ag/Zn/ZnO thin film by ablation of Zn metal with and without Ag metal in the evacuated chamber, respectively. The developing in the structure of Zn/ZnO thin film was carried by making an ablation of both metals at the same time, which helped to enhance the nonlinearity properties due to the local effect of Ag atoms and its nonlinearity property. The change of physicochemical properties after embedding the Zn/ZnO thin film with Ag layer was performance via X-ray diffraction, energy-dispersive X-ray spectroscopy, and UV–visible spectrophotometer, which illustrated the varying of their crystallinity, their elemental analysis, and their energy bandgap of the prepared samples. After that, an open and closed aperture Z-scan technique was used to determine the nonlinear absorption coefficient, nonlinear reflection coefficient, and the third-order nonlinearity susceptibility at 532 nm. Based on these calculations, the Ag/Zn/ZnO thin film could be considered as a promising material in the photonic applications.