Ablation Process Research Articles

High-Speed Laser Drilling for Dental Implantation: Ablation Process and Applicator Technology

Abstract Conventional mechanical drilling for implant placement is limited to specific geometry and orientation, resulting in incorrect positioning and inadequate anchoring in thin or porous bone. This study presents the development of a laser-based ablation process and an applicator technology for precise and fast laser drilling in the oral cavity. For the process development, a CO2 laser with a wavelength of 10.6 μm was used. Pulse durations between 10 μs and 400 μs were investigated for fast laser drilling with low thermal impact. For efficient ablation and cooling of the bone tissue, we applied a fine water spray. The laser applicator is designed with an integrated scanning module, focusing optics and a compact water spray system with three spray nozzles in the applicator tip. The geometry of the cavities was analyzed using digital microscopy and scanning electron microscopy, allowing to measure the ablated volume and depth as well as investigating the bone microstructure. This study demonstrates a laser ablation process capable to generate cavities with an ablation rate of 1.75mm3/s which is about 80% higher than previously reported. At this ablation rate the melted zones were smaller than 30 μm. This paper demonstrates a concept for a dental laser drilling system with a fast ablation process and a highlyintegrated applicator for treatment in the oral cavity.

Effect of nanosecond pulsed laser parameters on texturing formation of metallic surface: Experiment and modelling

The laser ablation process is an indispensable tool in precision micromachining for fabricating micro/nanostructures with specific geometries and regulating physicochemical properties on target surfaces. However, the absence of studies on the effect of laser parameters on texturing formation and surface microstructure makes process control and the optimization of surface texturing challenging. In this study, a nanosecond pulsed laser process was employed to create the micro-texturing on the Al alloy surface, emphasizing the effect of process parameters on surficial grain structures and texturing formation. A three-dimensional (3D) heat transfer model based on the finite element (FE) method was developed to numerically visualize the shape-dimensional evolution of micro-texturing during laser ablation. A simplified but effective moving laser heat source model was proposed to predict the dynamic spatial and temporal distributions of heat generation and transfer. Material removal, which was dominated by surface evaporation in the pulsed laser process, was achieved using the element deletion method. Under various laser parameters, the model-predicted cross-sectional groove profiles agreed well with experimental measurements. In addition, the effects of laser power and scanning speed on the groove morphologies were investigated. The experimental findings and numerical models established in this study will provide guidance for precisely controlling pulsed laser parameters to achieve desired texturing structures and dimensions.

Simulation analysis of cathodic ablation under the arcing action of vacuum rotary contacts

During the breaking process of the switchgear, a rotational movement of 1-10 degrees per millisecond is added to the contacts. Allowing for more even distribution of arc energy affects the cathodic ablation process. The cathode ablation process under the action of a vacuum rotary contact arc and the effect of rotary motion on the cathode surface are studied during arc ignition in a vacuum metal vapour arc in the paper. A three-dimensional (3D) cathodic ablation transient model with contact rotation characteristics is developed by considering the effects of arc pressure and the Marangoni effect, combined with the hydrodynamic equations and heat transfer equations. Based on a 3D transient model, the action of the arc on the cathode surface is compared and analyzed for different modes of contact movement. The results show that there is a lower cathode surface temperature, a smaller melt zone and a smaller ablation volume by the contact rotation method.

Effect of non-Planckian spectrum on shock velocities and subsonic to transonic transition in mid-Z witness plate elements

In this work, we obtain the shock velocities in mid-Z elements, namely, Al, Ti, and Cu by performing radiation hydrodynamic simulations using constant radiation drives consisting of equilibrium Planckian distribution along with high-energy Gaussian profiles. The drive temperatures have been varied from 80 to 270 eV, and the fraction of total energy density due to Gaussian distribution (α) changes from 0 to 0.4. Though the shock velocity in all the three elements rise with the strength of the drive temperature, its variation with α is quite complicated. Using simulations, we have shown that rear surface expansion is not responsible for the observed variation in shock velocity with the fraction of hard x rays at various temperatures and explained it in terms of distribution of total extinction coefficient over the spectral form of incident drive source leading to change in albedos. The percentage variations in shock velocities are found to be commensurate with those in albedos as expected for x-ray driven ablation process. Accurate scaling laws relating the drive temperatures with the shock velocities and α have also been obtained. In Al, subsonic to transonic transition temperature is found to increase with α, whereas in Ti it is found to decrease. We have explained the variation in transition temperature in terms of Mach number. As this transition temperature in Cu is anticipated to be high due to its higher atomic number and density, we did not observe any transition up to the temperature (500 eV) considered in this paper.

The emission intensity enhancement and improved limit of detection of Cu, Ag, and Au using electric field assisted LIBS

Conventional LIBS suffers from several challenges including high detection limit and low sensitivity. The current approaches include electric field-assisted laser-induced breakdown spectroscopy (EF-LIBS) to study the laser ablation process and characterize the effectiveness of this method on several parameters such as plasma temperature, electron number density, intensity enhancement, and limits of detection. The purpose of the present study is to analyze the improvement in the signal intensity and limits of detection of Copper (Cu), Silver (Ag), and Gold (Au) using EF-LIBS. The laser plasma is generated by focusing a high-power laser beam on gold alloy samples. The intensities of Cu and Ag lines were normalized using the Au line to reduce the statistical errors. Calibration curves were drawn for each element to determine the limit of detection (LOD). The detection sensitivity was enhanced using an external electric field to the axial direction of plasma. The effect of the electric field on plasma parameters, limits of detection, and signal intensities has been studied. It was observed that LODs of Cu and Ag were improved from 14.3 ppm to 4.6 ppm–1.7 ppm and 2.06 ppm respectively with significant enhancement in the emission intensity. The present study demonstrates that EF-LIBS can be utilized for the better detection of precious elements in geological mineralogical and alloy samples. In addition, results showed that the single-shot EF-LIBS is a better choice for precious samples because of a smaller mass ablation against standard LIBS and it is a low-cost setup as compared to other analytical techniques.

Paper-based facile capacitive touch arrays for wireless mouse cursor control pad

Wireless devices have become extremely inexpensive and popular in recent years. The two most significant advantages of wireless devices over wired ones are convenience and flexibility. Considering this, a wireless mouse pad prototype for access has been developed in this study. A capacitive sensors-based mouse pad with basic operations and conventional features has been developed using sensing arrays on paper. A facile, do-it-yourself fabrication process was utilized to develop a cost-effective, thin, wearable, and cleanroom-free wireless mouse cursor control (MCC) pad. The ablation process was used to cut the traces of conductive tape and paste them onto the paper to develop the MCC pad. The pad was connected with Espressif Systems (ESP)32 to wirelessly control the cursor of mobile and laptop. The capacitive touch sensor array-based pad is easy to reproduce and recycle. This pad can contribute to future advancements in thin human-machine interfaces, soft robotics, and medical and healthcare applications.

Photoacoustic real-time monitoring of UV laser ablation of aged varnish coatings on heritage objects

A novel, simple and non-invasive diagnostic methodology is presented herein, as an effective approach to monitor in real-time the UV laser-assisted thinning of aged varnished coatings from heritage objects, using the acoustic signals generated upon light interaction with matter. Detection of the photoacoustic (PA) signals is realized by means of a non-contact air-coupled ultrasonic transducer with a frequency response in the MHz regime. This proposed statistical approach utilizes the information the PA signals provide during the laser ablation process, embedded in their temporal delay and amplitude reduction during varnish removal. Based on the cross-correlation of the PA signals, this monitoring technique determines the critical laser pulse, responsible for complete varnish removal. The efficiency of our methodology has been examined on a series of aged varnish mock-ups on different substrates. The laser treated surfaces were further assessed using various techniques, in order to confirm the results of our PA monitoring strategy. Application of this technique is aimed at validating its potential and suitability in addressing different varnish cleaning challenges. Based on previous encouraging results on encrusted stonework, primary objective of this study is to establish the PA monitoring methodology as an essential, real-time monitoring tool for controlled laser ablation of aged varnish coatings from heritage surfaces (paintings, metallic objects, wall paintings etc.), ensuring their efficient removal while preserving the integrity of the objects. Implementation of the PA technique may pave the way for numerous applications as regards the reliable monitoring of removing unwanted layers from various surfaces of interest.

The Thermal Stability, Ablation Properties, Creamization Mechanism of Graphite/Zirconia (ZrO2)/Silicone Rubber Composites Containing Carbon Multicomponent Systems

It is urgent to improve the long-term ablation resistance of silicone rubber composites in order to meet the application requirements in the field of aerospace thermal protection. The graphite/ZrO2/silicone rubber (G/ZrO2/SR) composites prepared in this study were for that purpose. Firstly, the thermal stability and ablation properties of the G/ZrO2/SR composites were studied. The results showed that with the increase of graphite content, the initial decomposition temperature of the composites increased from 456.5 °C to 478.6 °C. The linear and mass ablation rates of the G/ZrO2/SR composite with 3 phr graphite were 0.048 mm/s and 0.0,220 g/s, respectively, which were decreased by 14.3% and 9.1%, compared with the ZrO2/SR composite without graphite. Moreover, the phase composition transformation and ceramization mechanism at high temperature of the G/ZrO2/SR composites containing carbon multicomponent system were studied. The results showed that the SR matrix completed the ceramic transformation during the ablation process and -Si-O-C pyrolysis products were formed and served as the skeleton of the ceramic layers. Finally, SiO2 and ZrO2 reacted with the graphite individually and the in-situ SiC and ZrC ceramic products formed enhanced the ceramic layers.

Laser ablation behavior of a 2-D C/SiC-Ti3SiC2 composite

When subjected to laser irradiation of different power densities, Ti3SiC2 MAX phase-modified 2-D C/SiC composite experiences various chemical and physical reactions and demonstrates various ablation resistance. An in-situ observation measurement is developed to obtain the instantaneous mesoscopic ablation process for revealing the ablation mechanism. Then scanning electron microscope (SEM) and X-ray energy dispersive spectroscopy (EDS) tests are performed to determine the reaction process. The results show that the Ti3SiC2 MAX phase can effectively prevent laser irradiation into the material at a laser power density below 636.5 W/cm2. The advantage of ablation resistance disappears at a high laser power density of 2546 W/cm2 due to the decomposition and sublimation of SiC and Ti3SiC2. A chart of ablation mechanisms versus laser power density is constructed based on the instantaneous mesoscopic ablation behavior, macro/meso/microscopic ablation morphology, and temperature history. It is also found that there are two forms of "Temperature Jump" phenomena. One is the accelerated temperature rise in the temperature history of the single-irradiation event. The other is the step point in the maximum temperature curve for multiple irradiation events. The mechanisms of the "Temperature Jump" phenomena are explained based on the interface energy balance.

The research on the high strength and anti-arc ablation coatings applied in steel conductive rail

In order to enhance the ablation-resistant performance of stainless-steel conductive rails, Mo coating, 410 stainless steel coating and 15 wt% Cr2AlC particles reinforced 410 stainless steel composite coating were prepared and evaluated. Different from the weak interfacial strength caused by the dissimilar metals between Mo and steel rails, 410 stainless steel coating has better interfacial contact with steel rails. The introduction of Cr2AlC into 410 stainless steels further strengthened the mechanical properties of coating by alloy strengthening effect and particle strengthening effect, as the decomposition of Cr2AlC into nano CrC particles is accompanied with the diffusion of Al atoms into 410 stainless steels. It was found that the composite coating can still resist arc erosion at 150 A current, as a dense oxide film formed during the ablation process and the decomposition of Cr2AlC contributed to the heat absorption.

Considerations on hydrogen isotopes release from thin films by laser induced ablation and laser induced desorption techniques

In this paper, we studied the release of deuterium atoms from 1 μm aluminum layers by Laser Induced Ablation and Laser Induced Desorption methods, using a 1053 nm laser source operating with 10 ns pulse duration and 1 kHz pulse repetition rate. The software control of the laser pulse energy successfully accomplished the transition from layer ablation to layer desorption. The layers have been produced by High Power Impulse Magnetron Sputtering technique on substrates with different surface properties.The amount of deuterium released from aluminum layers was evaluated by Quadrupole Mass Spectrometry after ablation respectively desorption of a small area of the sample exposed to the focused laser beam. The results were compared with the one obtained by Thermal Desorption Spectroscopy, which indicated a total amount of deuterium in the analyzed sample of about 2.6 × 1021 D at/m2. The mass spectra data revealed that 85% (2.2 × 1021 D at/m2) and 9% (0.2 × 1021 D at/m2) of total deuterium atoms released from the aluminum layer by Laser Induced Ablation and Laser Induced Desorption, respectively, were detected. The mathematical fitting of the experimental data indicated different laser fluences that boundary the desorption from ablation processes. Through analyses of the morphology of aluminum layer surfaces in connection with the substrate surface quality, the release of deuterium atoms by Laser Induced Ablation or Laser Induced Desorption processes can be identified.

Everest South Col Glacier did not thin during the period 1984–2017

Abstract. The South Col Glacier is a small body of ice and snow (approx. 0.2 km2) located at the very high elevation of 8000 m a.s.l. (above sea level) on the southern ridge of Mt. Everest. A recent study by Potocki et al. (2022) proposed that South Col Glacier is rapidly losing mass. This is in contradiction to our comparison of two digital elevation models derived from aerial photographs taken in December 1984 and a stereo Pléiades satellite acquisition from March 2017, from which we estimate a mean elevation change of 0.01 ± 0.05 m a−1. To reconcile these results, we investigate some aspects of the surface energy and mass balance of South Col Glacier. From satellite images and a simple model of snow compaction and erosion, we show that wind erosion has a major impact on the surface mass balance due to the strong seasonality in precipitation and wind and that it cannot be neglected. Additionally, we show that the melt amount predicted by a surface energy and mass balance model is very sensitive to the model structure and implementation. Contrary to previous findings, melt is likely not a dominant ablation process on this glacier, which remains mostly snow-covered during the monsoon.

In situ S isotopic analysis in apatite using laser ablation-multiple collector-inductively coupled plasma mass spectrometry

The S isotope composition (34S/32S) in apatite has been considered as a new powerful tool to trace S source reservoirs and to evaluate redox state and dynamic sulfur behavior in magmatic systems. This study presents the first in situ method to analyze S isotope compositions in apatite using laser ablation multiple collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). The sulfur isotope analysis of low-S apatite suffered the problem of high background interference, resulting in a low ratio of signal to noise (S/N). A detailed investigation found that ∼50% background of S isotopes originated from memory effect in the aerosol particles transformation system and can be removed through careful cleaning or replacement. A linear regression calculation method was proposed instead of the traditional data reduction method to improve the performance of correcting the S background signal. Femtosecond laser ablation system (fs-LA) was used to reduce the thermal effect and suppress the potential fractionation of S isotopes during the laser ablation process, significantly improving the stability of δ34SV-CDT values at different laser ablation parameters. Seven natural apatite samples with a large S concentration range were measured by the presented method. A good agreement of δ34SV-CDT values between fs-LA-MC-ICP-MS and IR-MS was obtained. The reproducibility of δ34SV-CDT obtained from fs-LA-MC-ICP-MS was similar to that in SIMS. These results confirm that the presented method can provide high-quality S isotopic compositions in natural apatites. Four apatite samples (Sly-1, Sly-2, MG, and OL-1) with various concentrations of SO3 (0.21% to 1.26%) show the homogeneous S isotope compositions based on the large amounts of repeated analyses using fs-LA-MC-ICP-MS. They are suggested as the high-quality external reference materials for in situ S isotope analysis for LA-MC-ICP-MS and SIMS.

Initial experience of the treatment of large glioma with microwave ablation-assisted surgical resection.

This study aimed to investigate the preliminary clinical outcomes of microwave ablation (MWA)-assisted surgical treatment for large glioma. In total, six cases of large glioma (diameter >4 cm) were described. All cases were treated with MWA-assisted surgical resection, which was performed using ultrasound to guide the accurate placement of the antenna in the central region of the tumor. The MWA power was 40-45 W, and 6 min was applied. Changes in the ablation area were observed using intraoperative Doppler ultrasound and contrast-enhanced ultrasound (CEUS). Ten patients treated with surgical resection alone were included in the control group. Data on surgical times (i.e., the time from the incision of the dura to the removal of the tumor), intraoperative blood loss, and complications were recorded. The median patient age was 45 years (range: 36.5-60.3 years). The median lesion diameter was 4.9 cm (range: 4.3-5.8). The microwave power was 40-45 W, and the median ablation time was 240 s (range: 208-297 s). The intra-tumoral vascular flow was significantly reduced after MWA. The median surgical time was shorter (38.5 min [range: 34.3-42.8 min]) and the median intraoperative blood loss was less (400 mL, [range: 400-450 mL]) in the combination treatment group than in the surgery-alone group. During the ablation process, no obvious additional neurological deficits were detected; however, a tube-shaped carbonide was found after the operation. MWA may be a useful complement to conventional techniques for the surgical resection of large glioma.

Laser liquid ablation for silver nanoparticles synthesis and conjugation with hydroxychloroquine for Covid-19 treatment

Synthesis, characterization, and anchorage studies of pristine silver nanoparticles were achieved. That would later be followed by the conjugation of the synthesized silver nanoparticles with hydroxychloroquine, a compound that is commonly identified as active against plasmodium, a malaria-causing agent. The synthesis of the pristine silver nanoparticles was achieved through laser ablation, a physical method. To achieve different concentrations and sizes of the nanoparticles, various parameters such as time and pulse repetition frequencies were varied. The base medium of the ablation was distilled water of 10 ml for every process of ablation. The laser ablation technique used proved effective in the production of silver nanoparticles spherical in shape and of the size range between 16 nm and 30 nm as deduced from Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) characterization techniques. EDS analysis confirmed the presence of AgNPs in the synthesized solution of silver nanoparticles, while the UV–Vis results showed that the absorption peak of AgNPs occurred at 403 nm. Through these findings, the use of laser ablation, a physical technique in the synthesis of AgNPs, is shown to be cost-effective and environmentally friendly with the properties of the nanoparticles proving to be effective for biomedical applications later in this work.

Influence of pressure and pulse energy on the expansion dynamics of nanoparticle-enhanced laser produced plasma

In the present work, we have studied the influence of pressure and pulse energy on the expansion dynamics of nanoparticle-enhanced laser produced plasma (NELPP) for two different metals, copper and aluminum. The targets were ablated using a Q-switched Nd:YAG laser operating at its primary wavelength of 1064 nm. The plasma imaging was recorded using the fast-gated ICCD camera. Although spectroscopic investigation of signal enhancement of emission line intensities in presence of nanoparticles (NPs), nanoparticle enhanced LIBS (NELIBS), has been performed extensively, expansion dynamics for NELIBS is not yet studied. We have carried out a detailed investigation of the plume propagation of NELPP for different pulse energies and ambient pressures. Temporal evolution of the distance of propagation of the plume front at different laser fluences and pressures shows a good agreement with the existing theoretical models. By comparing different plume propagation parameters, such as diameter, aspect ratio and expansion velocity, we have shown that the NELPP plume shows similar behavior as of LPP and its evolution can be explained with the existing models. Hence NPs, though influence the ablation process, do not alter the overall plume dynamics during the course of plasma evolution as observed for the two metals.

A plasma energy deposition based model for power cable bellows discharge

PurposeThis paper aims at building a discharge model for the power cable bellows based on plasma energy deposition and analyzing the discharge ablation problem.Design/methodology/approachAiming at the multiphysical mechanism of the discharge ablation process, a multiphysical field model based on plasma energy deposition is established to analyze the discharge characteristics of the power cable bellows. The electrostatic field, plasma characteristics, energy deposition and temperature field are analyzed. The discharge experiment is also carried out for result validation.FindingsThe physical mechanism of the bellows ablative effect caused by partial discharge is studied. The results show that the electric field intensity between the aluminum sheath and the buffer layer easily exceeds the pressure resistance value of air breakdown. On the plasma surface of the buffer layer, the electron density is about 4 × 1,019/m3, and the average temperature of electrons is about 3.5 eV. The energy deposition analysis using the Monte Carlo method shows that the electron range in the plasma is very short. The release will complete within 10 nm, and it only takes 0.1 s to increase the maximum temperature of the buffer layer to more than 1,000 K, thus causing various thermal effects.Originality/valueIts physical process involves the distortion of electric field, formation of plasma, energy deposition of electrons, and abrupt change of temperature field.

Ablation and surface structuring of nitride ceramics induced by picosecond laser pulses

In this work, the picosecond laser ablation process of aluminium nitride (AlN) and silicon nitride (Si3N4) ceramics is studied. The laser irradiation is performed by a Nd:YAG laser system that generates pulses with a duration of 10 ps and operates at the wavelengths of 266 nm, 355 nm, 532 nm, and 1064 nm. The ablation phenomena characterization is based on analyses of the ablation depth, the surface morphology and the chemical changes induced by the laser radiation. The dependences are studied of these characteristics on the processing parameters, namely, the laser wavelength, fluence and number of applied pulses, and the ambient pressure. The results presented concern the drilling geometry and the tracks formed when the sample is moving with respect to the laser beam. The ablation efficiencies in terms of ablation depth per incident fluence and per pulse are also discussed. It is found that the laser treatment results in a variety of micro- and nanostructures on the surface of the material. Ripple structure formation is observed in both ceramics, which are of different type with respect to the period and orientation. The ablation mechanisms are considered and evidence is provided that in picosecond regime decomposition of the ceramics could takes place with aluminium or silicon formation on the surface. The paper offers novel data on the fundamental picture of picosecond laser-matter interaction that can be useful in ceramic surface structuring and in designing methods for fabricating complex composite materials.

Identifying the influence of bubble size and position on crater formation during underwater nanosecond laser ablation of stainless steel

Underwater laser ablation can be employed both as a means to produce nanoparticles and to texturize surfaces of various materials. In this approach, a stationary or flowing water layer above the target surface confines laser induced plasma which cools to form short lived cavitation bubbles, positively influencing the amount of removed material per laser pulse. Plasma and cavitation bubble evolution additionally give rise to bubbles which may persist in the water throughout the ablation process. These bubbles are known to have a detrimental effect on material removal rates particularly in stationary water, but the quantitative influence of bubble dimensions and position on removed material volume is currently unknown. Here we show the laser intensity profile changes induced by bubbles located at 0–0.4 Rayleigh lengths above a stainless steel surface and couple these changes to removed crater volume. Our results show that water flowing at Reynolds numbers in the range of 1–100 positively contribute to crater volumes for pulse frequencies up to 1 kHz. At 1 kHz, it was found bubbles have insufficient time to flow from the vicinity of the laser spot, regardless of the Reynolds number within the range investigated. These conclusions assist in selecting an appropriate combination of laser and flow conditions to optimize laser ablation material removal rate.

Effect of charged dust grains on the electrojet instabilities

The Farley-Buneman and Gradient Drift instabilities have been investigated using a fluid model, in a partially ionized dusty electrojet region in which dust and neutral particles constitute a uniform static background. The effects of dissociative electron-ion recombination and dust charge fluctuation on the instabilities also have been taken into account. The electron-ion dynamics are considered to derive the perturbed densities which further lead to the generalized dispersion relation. The dispersion relation describes the propagation of electrojet instabilities having frequency within dust ion acoustic range in a magnetized partially ionized dusty plasma. The dispersion relation is separately solved numerically and analytically for the two values of anisotropy parameters which correspond to the two different altitudes in the electrojet region. It is found that Gradient drift instability is unstable at a much longer wavelength as compared to Farley-Buneman instability both with or without dust. At lower altitudes(90 km) the increase of negative charge on dust decreases the threshold electron drift velocity for Farley-Buneman instability while it shows the opposite behavior at higher altitudes(100 km). A much lower electron drift velocity is required to excite the Gradient drift instability than the Farley-Buneman instability at both altitudes. The dissociative electron-ion recombination damps both modes much more than the dust charge fluctuation. A significant changes in threshold drift velocity is observed for the Farley-Buneman mode as compared to the Gradient Drift mode due to the two main damping mechanisms. The present analysis is applicable in the lower ionospheric electrojet region where meteoric ablation processes are dominant.