Varying Laser Energy Research Articles

The ablation behavior of diamond/Cu composites by infrared nanosecond pulsed laser

This paper investigates the material removal behavior of diamond/Cu composites by multi-passes infrared nanosecond pulsed laser ablation, focusing on the formed surface cracks, periodic ripples, profile evolution and deposition. Combining nanosecond laser ablation experiments with simulations based on thermophysical properties is then undertaken to effectively reduce the maximum thermal stress and inhibit crack initiation and propagation. Three types of cracks were identified in nanosecond laser ablation, which were influenced by the diverse thermophysical properties of the material and the temperature gradient. The periodic ripples of 300–1800 nm on the sidewalls of the machined groove on diamond grains were induced when the laser fluence approached the ablation threshold, which did not even appear on the copper matrix as the thermal effects dominate. The groove profile showed a limited change as the ablation passes further increase to be over 40 due to the plasma shielding effect inside the groove, the laser defocusing phenomenon and the increased difficulty of sputtering the molten material. In addition, the different ablation mechanisms of diamond and copper resulted in the formation of overlapping deposition layers with changed surface characteristics at varying laser energy densities. The uneven island-like recast layer affected the uniformity of the ablated grooves, which was dependent on the material microstructure and accumulated laser energy.

Compaction characteristics and mechanism of the ADC12 alloy powder by laser impact compaction

This paper focuses on the dynamic compaction experimental investigation of ADC12 alloy powder using laser impact, leveraging the high strain rate and controllable precision of pulsed lasers. The effects of varying laser energy (Em) and impactor thickness on the relative density, microstructure, and microhardness of the ADC12 alloy powder billets were examined. Utilizing 2D multi-particle finite element simulation (2D MPFEM), the densification mechanism of these billets was analysed with the help of coordination numbers. The simulation also provided insights into the particle velocity, equivalent plastic strain, and adiabatic temperature increase during compaction. Key findings include that a relative densification of up to 97.27% in the billets is achievable when the laser energy reaches 6J. Notably, a decrease in impactor thickness at constant laser energy leads to a more uniform microstructure and microhardness in the billet. Simulations with the 2D MPFEM demonstrate that thinner impactors allow billets to absorb more energy, thereby increasing particle velocity and plastic strain. This enhances both the relative density and mechanical properties of the billets. The simulation explores the stress distribution during compaction and captures the adiabatic temperature rise on the surface of the pressed billet that occurs in the transient, which is consistent with experimental revelations that heat softens or even locally melts the particles to produce sintering. This study offers new insights into the formation process of these billets from a microstructural standpoint, elucidating the relationship between processing conditions and the resulting material properties.

Effect of nanosecond laser pulse width and energy on damage characteristics in carbon fibre reinforced plastic (CFRP) laminates

AbstractThis study explores the effects of laser pulse width and energy on CFRP laminates damage in laser bond inspection technology. Three testing programs were used, including varying laser energy while keeping pulse width constant, altering pulse width while maintaining constant power density, and modifying pulse width while keeping energy constant. The results show that when the pulse width remains constant, increased laser energy has a minimal effect on the initial damage location but leads to gradual interlayer delamination and fiber fracture propagation toward the impact surface. With constant laser energy, a specific threshold for pulse width is observed. When the laser pulse width is below this threshold, it exhibits a positive correlation with the damage characteristics of CFRP laminates, whereas when it exceeds this threshold, it shows a negative correlation. Power density correlates with damage when pulse width is constant, but there is no direct correlation when pulse width varies.Highlights CFRP laminates underwent laser shock tests with varying pulse widths. Power density is positively correlated with damage under specific conditions. There exists a specific threshold for laser pulse width. In single‐sided laser shock, initial damage spreads within a specified range.

Effect of pulsed femtosecond laser shock peening surface modification on anti-wear failure properties of AISI 9310 gear steel

The wear resistance of gear components significantly influences operational reliability and lifespan of mechanical equipment. Compared with nanosecond time scale laser surface treatment, femtosecond laser shock peening (FLSP) has the advantage of no absorption layer and constraint layer in processing complex geometric structure parts. However, attempts at FLSP for gear materials are quite limited up to now. This paper introduces a methodology employing Pulsed FLSP to enhance the wear resistance of AISI 9310 gear steel. The research delves into the effects of FLSP on the surface morphology, mechanical characteristics, and wear performance of AISI 9310 steel under varying laser energy levels (50 μJ, 100 μJ, 150 μJ, 200 μJ) and pulse spacings (10 μm, 15 μm, 30 μm). The findings reveal that femtosecond laser surface treatment significantly augmented surface microhardness by 9.4 % to 17.4 % and induced a surge in surface residual compressive stress (RCS) by 30.5 % to 103.1 %. Moreover, it introduced a work hardening layer of 150–300 μm in depth direction, resulting in a wear rate reduction ranging from 10.1 % to 61.7 %. The sample treated with 15 μm pulse spacing and 150 μJ laser energy exhibited simultaneously the lowest wear rate and a minimum average coefficient of friction (COF) on 0.47. The advancement in wear resistance is attributed to the synergistic effects of markedly increased surface hardness, gradient hardness in depth direction, and reduced grain size induced by FLSP. A multiple linear regression (MLR) model indicates that deeper work hardening layers are most significant for improving wear resistance, which reduces risk of wear failure.

Magnetic field confined laser-induced plasma: Improvement in sensitivity and repeatability

In this work, the transverse magnetic field confined laser-induced breakdown spectroscopy (MC-LIBS) technique was applied to investigate the signal sensitivity and repeatability of Al alloy plasma in the specially designed assembly. The emission signals from laser-induced plasma were recorded with varying laser energy (80 to 160 mJ) and magnetic field strength (1 to 3.5 kG). An emission signal enhancement up to 7 times was observed at 140 mJ laser energy and at 3 kG magnetic field strength. Compared to conventional LIBS, the magnetic field confined-LIBS improved the signal-to-noise ratio (SNR) by up to 5 times and the detection limit (LOD) from 86 to 26 ppm for zinc emission lines. Repeatability was evaluated using the relative standard deviation (RSD) of the Mg and Si emission lines, which was improved from 23 to 12% and 25 to 14%, respectively. Similarly, the measurement-to-measurement RSDs in electron temperature (Te) and electron number density (Ne) were improved from 12 to 7% and 1 3 to 5% when compared with conventional LIBS.

Controllable tensile performance of additively manufactured Al–Fe alloy

Achieving both high strength and ductility is challenging in additive manufacturing of Al alloys using the laser powder bed fusion (L-PBF) process by altering the laser conditions to control the microstructural characteristics. The current work focuses on the influence of varying laser energy density (ED), which is adjusted by different sets of laser power (P) and scan speed (v), on the microstructure-tensile property relationships of the L-PBF-fabricated Al–2.5%Fe alloy under varying laser conditions (P = 204–230 W, v = 450–600 mm/s) with a fixed powder layer thickness (t = 30 μm) and hatch distance (h = 30 μm). With increasing ED (= P/v·t·h), a slight increase in the average size of the columnar α-Al grains was found in the experimental samples concurrently with a higher fraction of <001>-oriented grains. Nanosized particles of the Al6Fe phase with an increased tendency to interconnect were observed in the matrix inside the melt pool, and the θ phase formed within the submicron-sized cellular structure along the melt pool boundaries (MPBs). A low tensile ductility, induced by the local microstructural inhomogeneities across MPBs, was found in all specimens tensile-deformed along the building direction, which was characterized by a preference fracture along the MPBs. At higher applied ED, the tensile ductility of the experimental Al–2.5Fe alloy was significantly improved with only a slight decrease in tensile strength. The difference in concentration of Fe across the MPBs in the matrix was also moderately diminished, which is consistent with the reduced local difference in microhardness across the MPBs under higher ED conditions. Therefore, the present results demonstrate that local microstructural inhomogeneities across MPBs can be controlled by the laser conditions, thereby producing both high strength and good ductility in the L-PBF processed Al–Fe alloys.

Study on the response and wear property of die steels with varying compositions to laser remelting bionic treatment

In order to research the wear property of die steel, based on the bionic theory, bionic units were manufactured by laser remelting treatment on the surface of five kinds of die steels with varying chemical compositions alloying element contents (1.77%, 5.73%, 8.66%, 9.38% and 14.39%). The differences and regularities in the characteristics (depth, width, area and depth to width ratio), microstructure and hardness of samples with varying laser energy density and compositions of the matrix were analyzed. Then, the wear property of die steel was experimentally evaluated. The results displayed that the cross-sectional area of the bionic unit increased with the increase of laser energy density for the same material. Meanwhile, when the energy density was constant, the cross-sectional area of the bionic unit increased with an increase in alloying element content, but the average hardness of the bionic unit first increased and then decreased. Compared with the untreated sample, the bionic sample is beneficial to enhance the wear property. Moreover, the wear property of die steels with chemical compositions alloying element content of 8.66% reinforced with bionic unit was more effective than other samples. The wear enhancement mechanism of the bionic sample was discussed.

Influence of liquid media and laser energy on the production of MgO nanoparticles by laser ablation

Nano and micro-sized metal particles are interesting solutions for several applications, from electronics to biomedical fields. In recent years, MgO has been gaining attention due to its nontoxicity and antibacterial activity, making this an interesting material for implants coating for instance.This study aims the fabrication/preparation of nanoparticles by laser ablation in liquid from the Mg bulk. The influence of liquid media and laser energy on the morphology, size and properties of the obtained nanoparticles was assessed. A Nd:YAG nanosecond laser of 1064 nm of wavelength at different laser energies was employed to irradiate Mg target in three environments (distilled water+SDS, ethanol and propanol). Ultraviolet–visible (UV–vis) absorption spectrophotometry, scanning electron microscopy with a transmission electron detector (STEM) and transmission electron microscopy (TEM) were used for characterizing the obtained particles, viz. particles’ mean size and size distribution. The composition of the obtained nanoparticles was analyzed by SAED patterns. The results showed that the characteristics of the obtained nanoparticles were prominently influenced by varying laser energy and liquid medium. The smaller particles are obtained when using ethanol and propanol (having 16.7 nm and 15.3 nm respectively), as compared to distilled water+surfactant.

Identification heavy metal pollution in biological samples around cement plant in Aceh, Indonesia using Laser Induced Breakdown Spectroscopy ( LIBS)

A study was conducted for identification of heavy metal pollution from biological sample as a potential proxy of environmental pollution due to industrial waste. The identification was conducted using the emerging analytical tool, namely laser induced breakdown spectroscopy (LIBS). The sample was collected from seawater near a cement plant in Aceh. Samples is a conch shell. The sample was dried in the open air and then prepared in the form of a pellet. The analysis was made by generating a plasma on the pellet sample using an Nd-YAG laser with a wavelength of 1,064 nm which is focused with a lens that has a focal length (f = 15 cm) by varying laser energy under low pressure of 3 Torr of air surrounding gas. Emission from the generated plasma was transmitted to the Maya2000 spectrometer optical detector using an optical fiber and then the emission spectrum of each element is displayed on the monitor. The results showed that the snail shell contained the salts and heavy metal elements K, Pb, Gd, Se, Mg, Rb, Fe, and Xe. Thus, it can be concluded that the heavy metal elements Pb and Fe can be detected LIBS technique from the biological sample.

Laser powder bed fusion of in-situ composites using dry-mixed Ti6Al4V and Si3N4 powder

Abstract Herein, we report laser powder bed fusion (L-PBF) of dry-mixed Ti6Al4V + Si3N4 powder to create in-situ titanium matrix composites. The dry-mixed Ti6Al4V powder with 5 wt.% Si3N4 was processed using l -PBF at varying laser energy densities, between 44 and 133 J/mm3, by changing the laser scan speed (400–1200 mm/s) at constant laser power of 96 W, layer thickness of 20 μm and scan spacing of 90 μm. The selected samples were examined for microstructural evolution, in-situ reaction products and hardness. The results showed that the in-situ reaction between liquid titanium and Si3N4 forms fine TiN and Ti5Si3 reinforcements in these l -PBF processed samples. However, the irregular shape and fine size of Si3N4 reduced the feedstock flowability, and the composites could not be processed with laser energy density (E) l -PBF but further improvement is required through adjusting Si3N4 powder attributes (size, shape) and concentration.

Laser-Ablative Synthesis of Isotope-Enriched Samarium Oxide Nanoparticles for Nuclear Nanomedicine.

Nuclear nanomedicine is an emerging field, which utilizes nanoformulations of nuclear agents to increase their local concentration at targeted sites for a more effective nuclear therapy at a considerably reduced radiation dosage. This field needs the development of methods for controlled fabrication of nuclear agents carrying nanoparticles with low polydispersity and with high colloidal stability in aqueous dispersions. In this paper, we apply methods of femtosecond (fs) laser ablation in deionized water to fabricate stable aqueous dispersion of 152Sm-enriched samarium oxide nanoparticles (NPs), which can capture neutrons to become 153Sm beta-emitters for nuclear therapy. We show that direct ablation of a 152Sm-enriched samarium oxide target leads to widely size- and shape-dispersed populations of NPs with low colloidal stability. However, by applying a second fs laser fragmentation step to the dispersion of initially formed colloids, we achieve full homogenization of NPs size characteristics, while keeping the same composition. We also demonstrate the possibility for wide-range tuning of the mean size of Sm-based NPs by varying laser energy during the ablation or fragmentation step. The final product presents dispersed solutions of samarium oxide NPs with relatively narrow size distribution, having spherical shape, a controlled mean size between 7 and 70 nm and high colloidal stability. The formed NPs can also be of importance for catalytic and biomedical applications.

Laser energy effect on the properties of ZnS thin films prepared by PLD technique

Zinc sulfide (ZnS) thin films were deposited on glass substrates using pulsed laser deposition technique. The laser used is the Q-switched Nd: YAG laser with 1064nm wavelength and 1Hz pulse repetition rate and varying laser energy 700mJ-1000mJ with 25 pulse. The substrate temperature was kept constant at 100°C. The structural, morphological and optical properties of ZnS thin films were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscope (AFM) and UV-VIS spectrophotometer.

Ultrashort PW laser pulse interaction with target and ion acceleration

We present the experimental results on ion acceleration by petawatt femtosecond laser solid interaction and explore strategies to enhance ion energy. The irradiation of micrometer thick (0.2–6.0 μm) Al foils with a virtually unexplored intensity regime (8 × 1019 W/cm2 – 1× 1021 W/cm2) resulting in ion acceleration along the rear and the front surface target normal direction is investigated. The maximum energy of protons and carbon ions, obtained at optimized laser intensity condition (by varying laser energy or focal spot size), exhibit a rapid intensity scaling as I0.8 along the rear surface target normal direction and I0.6 along the front surface target normal direction. It was found that proton energy scales much faster with laser energy rather than the laser focal spot size. Additionally, the ratio of maximum ion energy along the both directions is found to be constant for the broad range of target thickness and laser intensities.A proton flux is strongly dominated in the forward direction at relatively low laser intensities. Increasing the laser intensity results in the gradual increase in the backward proton flux and leads to almost equalization of ion flux in both directions in the entire energy range. These experimental findings may open new perspectives for applications.

Parametric scalings of laser driven protons using a high repetition rate tape drive target system

A series of experiments were carried out using the 200 TW laser facility at LLP, SJTU aiming to explore parametric scalings of laser driven protons employing a low cost and stable high repetition rate tape drive target system. For numerous laser shots at a repetition rate of ∼0.2 Hz with maximum laser intensity up to ∼5 × 1019 W/cm2 maximum energy of protons were measured by varying laser energy, focal spot size and laser pulse duration. The data suggests that the maximum energy of protons scales as I∼0.6 while changing the incident laser energy. Scaling trends are in good agreement with the previously reported experimental results and theoretical models. This study may provide a platform to investigate the characteristics of proton beams, such as source size and angular dispersion at a repetition rate required for many potential applications.

Spectroscopic analysis of high protein nigella seeds (Kalonji) using laser-induced breakdown spectroscopy and inductively coupled plasma/optical emission spectroscopy

The spectroscopic analysis of high protein nigella seeds (also called Kalonji) was performed using pulsed nanosecond laser-induced breakdown spectroscopy (LIBS) at 532 nm. The emission spectrum of Kalonji recorded with an LIBS spectrometer exposed the presence of various elements like Al, B, Ba, Ca, Cr, K, P, Mg, Mn, Na, Ni, S, Si, Cu, Fe, Ti, Sn, Sr, and Zn. The plasma parameters (electron temperature and electron density) were estimated using Ca–I spectral lines and their behavior were studied against laser irradiance. The electron temperature and electron density was observed to show an increasing trend in the range of 5802–7849 K, and (1.2–3.9) × 1017 cm− 3, respectively, in the studied irradiance range of (1.2–12.6) × 109 W/cm2. Furthermore, the effect of varying laser energy on the integrated signal intensities was also studied. The quantitative analysis of the detected elements was performed via the calibration curves drawn for all the observed elements through typical samples made in the known concentration in the Kalonji matrix, and by setting the concentration of P as the calibration. The validity of our LIBS findings was verified via comparison of the results with the concentration of every element find in Kalonji using the standard analytical tool like ICP/OES. The results acquired using LIBS and ICP/OES were found in fine harmony. Moreover, limit of detection was measured for toxic metals only.

Properties of Al- and Ga-doped thin zinc oxide films treated with UV laser radiation

This paper reports the Nd:YAG laser irradiation treated modified properties of aluminum (Al) and gallium (Ga) co-doped zinc oxide (ZnO) (AGZO) films prepared on Si-substrate via combined sol–gel and spin-coating method. The impact of varying laser energy (150–200 mJ) on the structure, morphology, electrical and optical properties of such AGZO films were determined. Laser-treated samples were characterized using various analytical tools. Present techniques could achieve a high-quality polycrystalline films compared with those produced via conventional high temperature processing. AGZO films irradiated with third harmonics UV radiation (355 nm) from Nd:YAG laser source revealed very low resistivity of 4.02 × 10− 3 Ω cm. The structural properties grain size was calculated firm the X-ray diffraction spectra using the Scherrer equation that increased from 12.7 to 22.5 nm as the annealing laser energy increased from (150–200) mJ. The differences in crystallinity and orientation are explained in terms of the thermal effect caused by laser irradiation. (FESEM) images have been demonstrated that Nd:YAG laser annealing can significantly improve the crystallinity level, densification, and surface flatness of sol–gel derived AGZO thin films that occurred as a result of laser processing. Synthesized AGZO films displayed favorable growth orientation along (101) lattice direction. AGZO films with energy band gap of 3.37–3.41 eV were obtained. Results on the crystallinity, surface morphology, roughness, bonding vibration, absorption, photoluminescence, and resistivity of the laser-irradiated films were analyzed and discussed.

Synthesis of truncated tetrahedral cinnamon nanoparticles in citric acid media via PLAL technique

Cinnamon nanoparticles (CNPs) containing rich active agents of cinnamaldehyde and polyphenols are prospective for nanobiomedicine. They are preferred over metallic nanoparticles due to excellent bioactivity and non-toxicity. This paper reports the structural and emission properties of CNPs grown in citric acid medium (under varying laser energy) using pulse laser ablation in liquid (PLAL) technique. TEM analysis revealed the nucleation of crystalline truncated tetrahedral CNPs with average diameter ≈12.85 nm. EDX spectra detected the exact elemental constituents in protein capped CNPs. Raman spectra displayed the symmetric bonding vibration of CNPs in the presence of secondary metabolites enclosing terpenoids, flavonoids, phenols and tannins. Photoluminescence emission spectra disclosed two prominent peaks centered at 420 nm and 480 nm assigned to the occurrence of phenolic acids in CNPs.

Influence of laser irradiation on deposition characteristics of cold sprayed Stellite-6 coatings

Depositing hard materials such as Stellite-6 solely by cold spray (CS) is challengeable due to limited ability of plastic deformation. In this study, the deposition of Stellite-6 powder was achieved by supersonic laser deposition (SLD) which combines CS with synchronous laser irradiation. The surface morphology, deposition efficiency, track shape of Stellite-6 coatings produced over a range of laser irradiation temperatures were examined so as to reveal the effects of varying laser energy inputting on the deposition process of high strength material. The microstructure, phase composition and wear/corrosion resistant properties of the as-deposited Stellite-6 coatings were also investigated. The experimental results demonstrate that the surface flatness and deposition efficiency increase with laser irradiation temperature due to the softening effect induced by laser heating. The as-deposited Stellite-6 tracks show asymmetric shapes which are influenced by the relative configuration of powder stream and laser beam. The SLD coatings can preserve the original microstructure and phase of the feedstock material due to relatively low laser energy inputting, which result in the superior wear/corrosion resistant properties as compared to the counterpart prepared by laser cladding.

Efficacy of Photon-induced Photoacoustic Streaming in the Reduction of Enterococcus faecalis within the Root Canal: Different Settings and Different Sodium Hypochlorite Concentrations

IntroductionThe purpose of this study was to determine the effectiveness of laser-activated irrigation by photon-induced photoacoustic streaming (PIPS) in the reduction of Enterococcus faecalis in root canal disinfection, varying laser energy output, and sodium hypochlorite (NaOCl) concentration. For effective removal of the smear layer, the sequence and resting time of the final irrigation steps were modified compared with the standard PIPS protocol. MethodsEighty-six extracted single-rooted teeth were mechanically prepared, sterilized, and inoculated with E. faecalis for 4 weeks. Teeth were divided into 9 groups and treated with an Er:YAG laser using a PIPS 600/9 tip at the following parameters: 10 mJ or 20 mJ, 15 Hz, and a 50-microsecond pulse duration at 0.15 W or 0.3 W average power, respectively. Root canals were irrigated with different concentrations of NaOCl (ie, 1%, 3%, and 5% and activated using the adjusted PIPS protocol). The bacterial count was performed immediately after and 48 hours after decontamination and new incubation on an agar plate. ResultsA statistically significant difference in bacterial counts (P < .05) was detected in all groups before and directly after the treatment and in groups treated with 5% NaOCl 48 hours after treatment. Scanning electron microscopic imaging showed an absence of bacteria and biofilm in the scanned areas after treatment with 5% NaOCl. ConclusionsLaser-activated irrigation using 5% NaOCl and a modified PIPS protocol resulted in effective eradication of the bacterial biofilm and removal of the smear layer.

Tailoring residual stress profile of Selective Laser Melted parts by Laser Shock Peening

The paper describes a new approach in controlling and tailoring residual stress profile of parts made by Selective Laser Melting (SLM). SLM parts are well known for the high tensile stresses in the as – built state in the surface or subsurface region. These stresses have a detrimental effect on the mechanical properties and especially on the fatigue life. Laser Shock Peening (LSP) as a surface treatment method was applied on SLM parts and residual stress measurements with the hole – drilling method were performed. Two different grades of stainless steel were used: a martensitic 15-5 precipitation hardenable PH1 and an austenitic 316L. Different LSP parameters were used, varying laser energy, shot overlap, laser spot size and treatments with and without an ablative medium. For both materials the as-built (AB) residual stress state was changed to a more beneficial compressive state. The value and the depth of the compressive stress was analyzed and showed a clear dependence on the LSP processing parameters. Application of LSP on SLM parts showed promising results, and a novel method that would combine these two processes is proposed. The use of LSP during the building phase of SLM as a “3D LSP” method would possibly give the advantage of further increasing the depth and volume of compressive residual stresses, and selectively treating key areas of the part, thereby further increasing fatigue life.