Laser Heating Research Articles

Application of laser heating to coat ceramic surfaces: An alternative for traditional Raku firing

This study presents a novel approach for coating ceramic surfaces with an organic material using laser heating. To achieve this, white clay ceramics were prepared and subjected to a 150W continuous wave fiber laser irradiation at 1090 nm for various durations. Following the laser treatment, a physical contact was established between an ostrich feather and the non-illuminated surface of the ceramic. As a result, the ostrich feathers underwent distinct stages of chemical changes known as pyrolysis, depending on the duration of laser illumination. Subsequently, the ceramics obtained were analyzed using SEM, EDX, XRD, and optical microscopy. Our experimental results indicate a specific temperature range between low temperatures (below 500 °C) where the pyrolyzed feathers do not adhere properly to the surface and higher temperatures (around and above 800 °C) where excessive pyrolysis occurs, resulting in an aesthetically pleasing pattern on the ceramic surface reminiscent of ostrich feather Raku. EDX and XRD analyses confirmed the penetration of feather residue into the structure of the non-illuminated surface, creating an artistic pattern, while the illuminated side displays a glazed and glassy like surface. Thus, these findings present a promising and innovative method that significantly reduces energy consumption and process time when compared to traditional Raku pottery approaches.

A Study on the Characteristics of 304 Stainless Steel According to the Water Temperature Changes in Underwater Laser Beam Machining

In underwater laser beam machining (ULBM), water provides a cooling effect by reducing the influence of the laser heat source, which makes ULBM more suitable for marking, cutting, and postprocessing than laser beam machining (LBM). Because the laser heat source not only affects the substrate temperature, but also heats the water, this study analyzes how the cooling effect occurs when water is heated. In this study, the heat-transformed zones in ULBM and heated underwater laser beam machining (HULBM) were improved by approximately 33% and 24%, respectively, compared to LBM at 400 W. In addition, the heat-affected zones in ULBM and HULBM improved by approximately 15% and 9%, respectively, compared to LBM. The hardness of ULBM and HULBM was higher than that of LBM. Based on these results, it was confirmed that water can reduce the effect of the laser heat source and improve the mechanical properties. Experiments will be conducted on the underwater laser beam machining of various substrates, such as Inconel718 and Ti-6Al-4V, in a future study. In addition, experiments will be conducted on the underwater laser beam machining of various substrates using a cooling system that can lower the temperature of water.

Superconductivity discovered in niobium polyhydride at high pressures

Niobium polyhydride was synthesized at high pressure and high temperature conditions by using diamond anvil cell combined with in situ high pressure laser heating techniques. High pressure electric transport experiments demonstrate that superconducting transition occurs with critical temperature(Tc) 42 K at 187 GPa. The shift of Tc as function of external applied magnetic field is in consistent to the nature of superconductivity while the upper critical field at zero temperature μ0Hc2(0) is estimated to ∼16.8 T while the GL coherent length ∼57 Å is estimated. The structure investigation using synchrotron radiation implies that the observed superconductivity may come from Fm-3m phase of NbH3.

An in-situ experimental HP/HT study on bromine release from a natural basalt

We present the first in-situ partitioning data for bromine between a natural basaltic melt and a coexisting fluid. For this study hydrothermal diamond anvil cell experiments at pressures up to 1.7 GPa were conducted. We combined laser heating to melt the basalt glass with external heating to lower the temperature gradient in the cell and to initiate circulation for the aqueous fluid. Bromine concentrations were measured in-situ with X-ray fluorescence in the basaltic melts, glasses, and in the fluid. From the results we calculated partition coefficients of DBrfluid/melt = 1.19 to 3.92 in the range of 0.4 to 1 GPa for aqueous fluids. Experiments with neon as the surrounding fluid (DBrfluid/melt = 0.38 ± 0.01 at 1.1 GPa) suggest that Br-release from a basalt into volatiles that have no bonding affinity with Br is weak. This should be the case for dry intra-plate volcanic eruptions. From the experimentally gained partition coefficients and from global Br concentration values in melt inclusions of arc magmas, we calculated an annual global Br flux of 23.5–72.9 × 109 g/y.

Effect of laser power, speed and offset on the welding performance of 304 SS/Al2O3 ceramics

In this study, 304 SS/Al2O3 ceramic structural parts were successfully prepared by laser heat source biasing using AgCuTi as filler. The method removes residual thermal stresses by retaining unfused 304 SS (stainless steels), provides protection to the Al2O3 ceramics, and connects the two sides of the substrate using the wettability of the AgCuTi filler. Based on the 304 SS/Al2O3 connectivity, the Gibbs free energy changes of Ti–Fe and Ti–Cu compounds at the weld were calculated from the thermodynamics perspective to determine the possible phases. The temperature field of the joint was also investigated using finite element simulation to analyze the temperature changes in the fusion zone, the interface I (304 SS/AgCuTi), and the interface II (AgCuTi/Al2O3) under different welding parameters, and predict the welding parameters that can achieve an effective connection without destroying the Al2O3 ceramics, which were experimentally verified. The maximum tensile strength of the joints was 94.9 MPa when the laser power was increased from 372 W to 432 W. The maximum tensile strength of the joints was 90.5 MPa when the laser speed was increased from 440 mm/min to 630 mm/min. The maximum tensile strength of the joints was 89 MPa when the laser offset was increased from 1.4 mm to 1.9 mm. By analyzing the microstructure, it was found that brittle intermetallic compounds (IMCs) such as FeTi and Cu2Ti were generated at interface I, which was the main factor affecting the strength of the joint. Many Ag(s,s) and Cu(s,s) solid solutions were found at AgCuTi and interface II. By analyzing the microstructure, the interface organization of the joint is composed of 304 SS + α-Fe/γ-Fe + FeTi/Cu2Ti + Ag(s,s)/Cu(s,s) + Ti2Cu + Al2O3. Finally, the Arrhenius function calculates the diffusion coefficients and diffusion concentrations of Ti and Fe elements.

Sensitive Detection of Biomolecular Adsorption by a Low-Density Surfactant Layer Using Sum-Frequency Vibrational Spectroscopy.

Small molecules or proteins interact with a biomembrane in various ways for molecular recognition, structure stabilization, and transmembrane signaling. In this study, 1,2-dipalmitoyl-3-trimethylammonium-propane (DPTAP), having a choline group, was used to investigate this interaction by using sum-frequency vibrational spectroscopy. The sum-frequency spectrum characteristic of a neat monolayer changed to that of a bare air/water interface at a larger molecular area of the DPTAP molecules due to local laser heating. Upon introduction of the aromatic molecules in the subphase at around 120 Å2 per molecule, the sum-frequency signal suddenly reappeared due to molecular adhesion, and this was utilized to probe the adsorption of the aromatic ring molecules in the water subphase to the choline headgroup of the DPTAP by cation-π interaction. The onset concentrations of this sum-frequency signal change allowed a comparison of the relative interaction strengths between different aromatic molecules. A zwitterionic surfactant molecule (DPPC) was found to interact weakly compared to the cationic DPTAP molecule.

Numerical study on multiphase evolution and molten pool dynamics of underwater wet laser welding in shallow water environment

Underwater wet laser welding (UWLW) is a promising and labor-saving in-situ repair technique in aquatic environments, which simplifies the arduous dismantling and transportation processes of repairing underwater equipment on land. However, the thermo-physical mechanism during UWLW is still unclear. This study presents, for the first time, a thermal multi-phase flow model to study the heat transfer, fluid dynamics, and phase transitions involved in the UWLW process at shallow water column depths (water depth ≤ 4 mm). A dual-cone volumetric heat source model considering the laser energy distribution in both the water and metal is proposed. The driving forces, including gravity, surface tension, and the water/metal vapor recoil pressure are taken into account. The simulated weld profiles are in good agreement with the experimental results. The results indicate that in the UWLW process, laser heating creates a water keyhole, forming a localized dry region (LDR) above the molten pool. The LDR isolates the water from the molten pool and protects the laser-metal interactions, thereby making the welding environment similar to that of in air laser welding (IALW). Due to the water evaporation, the upper rear and sides of the molten pool during the UWLW pocessess a higher cooling rate compared to the IALW case, resulting in a higher temperature gradient and smaller molten pool dimensions. The results contribute to a better understanding of the complex interactions in UWLW process.

Numerical simulation of laser heating effect in optical temperature measurement based on Kubelka-Munk theory

The fluorescence intensity ratio (FIR) technique is widely used in many fields as one of the sensing methods of phosphor thermometry. In the gas turbine field, the rare earth ions are often doped to thermal barrier coating (TBC). When excited by laser pulses TBC glows phosphorescent, and it can be utilized for thermometry. The laser energy absorbed by the TBC is not only used to generate the luminescence but also introduces heat into the TBC and causes a temperature rise further increasing optical temperature measurement error. Therefore, it’s essential to predict the temperature rise and the temperature measurement error, and take measures to reduce the error due to the laser heating effect. However, there are few researches concerning this problem, and most of them focus on the relationship between the laser energy and the point temperature measured by the FIR technique. Here we show a method for evaluating the effect of laser heating on temperature fields and optical temperature measurement errors by establishing thermal equivalent model and discrete model of body luminescence, considering laser and phosphorescence scattering in coatings made of YSZ based on Kubelka-Munk theory. We found that continuous pulsed laser heating caused severe temperature rise and significant temperature measurement error. Furthermore, the temperature rise can be decreased to the level of a single pulsed laser heating by decreasing the frequency of laser. In addition, the main influencing factors of the temperature measurement error are the density of laser energy and coating thickness.

Feasibility study and thermal process of producing deep-small holes by laser/ultra-high frequency induction hybrid deposition

In this study, a laser/ UHF induction hybrid deposition process with embedding tube for forming deep-small hole method is proposed. The laser and induction powers, as main and auxiliary heat source, are used to melt the metal wire and preheat the objects (the substrate, metal wire and embedded tube), respectively. The critical role of the preheating is to provide a high-temperature zone on the objects which guarantee the effective bonding among the deposited track, substrate and embedded tube. The embedded tube is pre-placed on the substrate outside induction coil and is not irradiated by laser beam, but is wrapped in the deposited track by dripped molten droplet. A numerical model coupled with temperature and electromagnetic fields is developed to investigate the thermal process during hybrid deposition. The thermal process with different combination states of laser and induction heating is numerically investigated to reveal the influence mechanism of the two heat sources on the penetration deposition of the deposited track and the size of molten metal in front of the deposition track. Results show that the laser heat mainly dominates the penetration depth of the deposited track and the size of the molten metal by increasing the temperature of the deposited metal. Criteria for characteristic temperature Tpeak2 is proposed based on the thermal process to avoid excessive temperature and possessing a large penetration depth of deposited track. The experiments demonstrate the process feasibility of the proposed deposited method and verify the reliability of the numerical model.

Laser resolidification of Al-5Mg-0.1Sc alloy: Growth of cells and banded structures

The versatility of Al-Mg alloys makes them well-suited for applications ranging from everyday items to cutting-edge fields like automotive, microelectronics, and aerospace. Moreover, although Al-Mg alloys hold promise for improved surface features in components, research on their laser surface remelting (LSR) remains scarce, presenting an open opportunity to create novel components with these materials. Understanding the growth modes and morphologies of laser surface remelted products is critical in this context. Using a laser instrument, optical microscopy, SEM, XRD, Vickers hardness and image analysis techniques, a correlative analysis of microstructure features and laser heat input is proposed in this research. Furthermore, the Al-5Mg-0.1Sc (wt%) alloy was remelted using two distinct original substrates, each exhibiting varying degrees of microstructure coarsening. Additionally, four distinct laser heat input conditions were applied to each case. All molten pools regions were formed either by cells or bands, with higher growth rates producing a higher fraction of bands. While the variation in the original microstructure of the substrate did not significantly impact both cellular spacings and band/cellular fractions, the microhardness varied remarkably with the reduction in energy input from 10.0 J/mm to 1.7 J/mm. Kurz and Fisher model provided an accurate prediction of the cell spacings formed at the laser molten pool.

Crystal plasticity simulations with representative volume element of as-build laser powder bed fusion materials

Additive manufacturing of as-build metal materials with laser powder bed fusion typically leads to the formations of various chemical phases and their corresponding microstructure types. Such microstructures have very complex shape and size anisotropic distributions due to the history of the laser heat gradients and scanning patterns. With higher complexity compared to the post-heat-treated materials, the synthetic volume reconstruction of as-build materials for accurate modelling of their mechanical properties is a serious challenge. Here, we present an example of complete workflow pipeline for such nontrivial task. It takes into account the statistical distributions of microstructures: object sizes for each phase, several shape parameters for each microstructure type, and their morphological and crystallographic orientations. In principle, each step in the pipeline, including the parameters in the crystal plasticity model, can be fine-tuned to achieve suitable correspondence between experimental and synthetic microstructures as well as between experimental stress–strain curves and simulated results. To our best knowledge, this work represents an example of the most challenging synthetic volume reconstruction for as-build additive manufacturing materials to date.

An iterative path compensation method for double-sided robotic roller forming of compact thin-walled profiles

High-precision robotic forming of ultrahigh strength materials is challenging due to the significant stiffness deformation of industrial robots. In this work, a double-sided robotic roller forming process was developed to form ultrahigh strength steels to thin-walled profiles. Synchronized laser heating prior to plastic deformation was initially introduced as a means of reducing the required forming forces. Considering the varying forming forces during the compensation of stiffness-deformation-induced path deviation, an iterative path compensation method was proposed and implemented to enable continuous adjustments of path compensation values, utilizing a robot stiffness model and the correlation between compensation values and forming forces. Results show that laser heating has a significant positive effect on reducing springback angle due to the decrease of forming forces, while the path compensation facilitates the forming of compact thin-walled profiles with sharp bending radii. It is validated that the proposed method for iterative path compensation is conducive to the determination of the optimized path compensation values with limited iterations.

Environmental conical nozzle levitator equipped with dual wavelength lasers

AbstractThe environmental conical nozzle levitator (E‐CNL) with dual‐wavelength lasers is an extreme environment materials characterization system that was designed to investigate ultra‐high‐temperature materials: refractory metals, oxides, carbides, and borides above 3000 K in a controlled atmosphere. This article details the characterizations using this system to establish its high‐temperature capabilities and to outline ongoing work on materials under extreme conditions. The system has been used to measure the melting point of several oxide materials (TiO2, Tm = 2091 ± 3 K; Al2O3, Tm = 2310 3 K; ZrO2, Tm = 2984 31 K; and HfO2, Tm = 3199 ± 45 K) and several air‐sensitive refractory metals (Ni, Tm = 1740 K; Ti, Tm = 1983 K; Nb, Tm = 2701 K; and Ta, Tm = 3368 K—note: mean ± standard deviation) during levitation which matched literature values within 0.17–2.43 % demonstrating high accuracy and precision. This containerless measurement approach is critical for probing properties without container‐derived contamination, and dual‐wavelength laser heating is essential to heat both relatively poor electrical conductors (some refractory metals and carbides) and insulators (oxides). The highest temperature achieved utilizing both lasers in these experiments was ∼4250 ± 34 K on a 76.6 mg, molten HfO2 sample using a normal spectral emissivity of 0.91. Stable levitation was demonstrated on spherical samples (yttria‐stabilized zirconia) while adjusting levitation gas composition from pure oxygen to pure argon, verifying atmospheric control up to 3173 K on solid or molten samples. These successes demonstrate the viability of in situ high‐temperature environmentally controlled studies potentially up to 4000 K on all classes of ultra‐high‐temperature materials in one system. These measurements highlight the E‐CNL system will be essential for the development of next‐generation ultra‐high‐temperature materials for hypersonic platforms, nuclear fission and fusion, and space exploration.

Laser heating of ferroelectric cubes for tunable electromagnetic properties in metamaterials

In this experimental study, we demonstrate the feasibility of a thermally tunable, resonant dielectric microwave metasurface based on sub-wavelength Mie resonances of ferroelectric dielectric cubes (Calcium titanate, CaTiO3) in which the temperature of the meta-atoms can be locally and dynamically controlled by heating with an optical laser beam over a large range of temperatures and, consequently, values of the dielectric constant of the cube and corresponding resonance frequency of the meta-atoms. This avoids any interference of otherwise necessary heating elements or power supply wires with the propagation of the microwave signal and can be made spatially addressable. The concept scales at least to the THz domain. This contactless approach opens up an alternative avenue to tunability and active control of metamaterials.

Viscosity measurement of molten alumina and zirconia using aerodynamic levitation, laser heating and droplet oscillation techniques

Reliable thermophysical properties of core melt (corium) are essential for the accurate prediction of the severe accident progression in light water reactors. Zirconia is one of the most important materials in corium. Despite the high interest in the viscosity of molten zirconia, few experimental data have been reported due to its high melting temperature and high vapor pressure. In the present study, the viscosity of molten zirconia was measured using aerodynamic levitation, laser heating and droplet oscillation techniques. A material sample was levitated by argon gas flow in a conical nozzle and then melted into a droplet by laser beams. The initial quiescent droplet was forced to oscillate by the excitation of a loudspeaker, and the viscosity was deduced based on the characteristics of the droplet damped oscillation after the loudspeaker was turned off. The viscosity of molten alumina was first measured for verification of the measurement system. Afterwards the viscosity of molten zirconia was measured. The results showed that the viscosity of molten zirconia at melting temperature (2988K) was 12.87 ± 1.03 mPa s and decreased with increasing temperature. The measurement uncertainties are within 21 %.

Formation of hot spots at end-on pre-compressed isochoric fuels for fast ignition

It is crucial to form a hot spot that can drive a self-heating nuclear burn propagation into the surrounding cold fuel in ignition process of laser fusion. In this paper, we discuss the formation of a hemispherical hot spot located at the edge of an end-on precompressed isochoric fuel instead of a central spherical hot spot surrounded by cold fuel in a corona plasma shell. This configuration leads to a new energy loss mechanism named hot spot collapse, which originates from mass loss of the hot spot through the interface with the vacuum. A semi-analytical model is proposed including α particle induced burning, hot spot collapse and other energy loss processes. Then a modified ignition criterion is derived. The results show that the competition between the hot spot collapse and the burn propagation is crucial in the formation of the hot spot. The formation of such a hot spot at end-on precompressed isochoric fuels would require a somewhat higher initial temperature of Th=9 keV for a hot spot with an initial areal density ρd=0.6gcm−2 . Simulations are performed with a 3D hybrid particle-in-cell/fluid code for the heating process by fast electrons and a 3D radiation hydrodynamics code for the burning process. Simulation results agree with the model. Our optimized result shows a 10 ps heating laser pulse with an energy as low as 39 kJ can lead to a fast ignition in the ideal case. This study provides an effective reference for design and evaluation of experiments planned for fast ignition schemes.

Widefield Diamond Quantum Sensing with Neuromorphic Vision Sensors.

Despite increasing interest in developing ultrasensitive widefield diamond magnetometry for various applications, achieving high temporal resolution and sensitivity simultaneously remains a key challenge. This is largely due to the transfer and processing of massive amounts of data from the frame-based sensor to capture the widefield fluorescence intensity of spin defects in diamonds. In this study, a neuromorphic vision sensor to encode the changes of fluorescence intensity into spikes in the optically detected magnetic resonance (ODMR) measurements is adopted, closely resembling the operation of the human vision system, which leads to highly compressed data volume and reduced latency. It also results in a vast dynamic range, high temporal resolution, and exceptional signal-to-background ratio. After a thorough theoretical evaluation, the experiment with an off-the-shelf event camera demonstrated a 13× improvement in temporal resolution with comparable precision of detecting ODMR resonance frequencies compared with the state-of-the-art highly specialized frame-based approach. It is successfully deploy this technology in monitoring dynamically modulated laser heating of gold nanoparticles coated on a diamond surface, a recognizably difficult task using existing approaches. The current development provides new insights for high-precision and low-latency widefield quantum sensing, with possibilities for integration with emerging memory devices to realize more intelligent quantum sensors.

Fatigue life prediction of AA2524 thin plate strengthened using compound laser heating and laser shot peening method

AA2524 is a aluminum alloy based on damage tolerance design, and it is mainly used for the manufacturing of aircraft skins. Aircraft skins often occur fatigue failure due to harsh working conditions. To improve the fatigue resistance of aircraft skins and to accurately predict the fatigue life of AA2524 compact tension (CT) samples. The compound strengthening method of lsear heating (LH) and lsear shot peening (LSP) is proposed to improve the fatigue life of AA2524 in this paper. Considering the effect of stress ratio (R), residual stress (RS), stress intensity factor range (ΔK), and maximum stress intensity factor (Kmax) on the fatigue crack growth rate (FCGR), the fatigue life of CT samples was predicted applying artificial neural networks, support vector regression models. The results show that laser heating and laser shot peening can obviously improve the fatigue life by 30.703% at R = 0.1 and 4.701% at R = 0.5, compared with base materials. The neural networks have better fatigue life prediction ability, and the fit coefficients for the neural networks predicting fatigue life reach 0.97, which is better than that of Walker model (0.91). The prediction value for ANN model is 75,462 cycles, the magnitude for SVR model is 78,234 cycles, and the experimental value is 74,204 cycles. The deviation are 1.7% and 5.43%, respectively. Meanwhile, the effect of R on the FCGR of AA2524 is closely associated with the crack closure effect.

Side-effects of laser weeding: quantifying off-target risks to earthworms (Enchytraeids) and insects (Tenebrio molitor and Adalia bipunctata)

With challenges posed by chemical and mechanical weed control, there are now several research and commercial projects underway to develop autonomous vehicles equipped with lasers to control weeds in field crops. Recognition systems based on artificial intelligence have been developed to locate and identify small weed seedlings, and mirrors can direct a laser beam towards the target to kill the weed with heat. Unlike chemical and mechanical weed control, laser weeding only exposes a small area of the field for the treatment. Laser weeding leaves no chemicals in the field after the treatment or does not move the soil which may harm crop roots and non-target organisms. Yet, it is well-known that laser beams can harm living organisms; the effect on the environment and fauna should be studied before laser weeding becomes a common practice. This project aimed to study the effect of laser on some living non-target organisms. We investigated the effect of laser treatment on the mortality of two species of earthworms (Enchytraeus albidus and Enchytraeus crypticus), larvae, pupas, and beetles of yellow mealworm beetles (Tenebrio molitor) and the two-spotted lady beetle (Adalia bipunctata) for increasing dosages of laser energy. In all earthworms experiments except one, the mortality rates of the worms living in the uppermost soil layer of clay, sandy, and organic soil exposed to laser heating were not significantly different from the controls even with laser dosages up to 23.8 J mm-2. Laser doses sufficient to kill plants were lethal to the insects, and lower doses that did not kill plants, killed or harmed the insects across all life stages tested. The larger beetles survived higher doses than smaller. Laser weeding is a relatively new technology and not yet widely practiced or commercialized. Therefore, we do not discuss and compare the costs of the different weeding methods at this early stage of the development of the technology.

Extensively Microtwinned Diamond with Nanolaminates of Lonsdaleite Formed by Flash Laser Heating of Glassy Carbon.

Diamond's unique properties on the nanoscale make it one of the most important materials for use in biosensors and quantum computing and for components that can withstand the harsh environments of space. We synthesize oriented, faceted diamond particles by flash laser heating of glassy carbon at 16 GPa and 2300 K. Detailed transmission electron microscopy shows them to consist of a mosaic of diamond nanocrystals frequently joined at twin boundaries forming microtwins. Striking 3-fold translational periodicity was observed in both imaging and diffraction. This periodicity was shown to originate from nanodimensional wedge-shaped overlapping regions of twinned diamond and not from a possible 9R polytype, which has also been reported in other group IVa elements and water ice. Extended bilayers of hexagonal layer stacking were observed, forming lonsdaleite nanolaminates. The particles exhibited optical fluorescence with a rapid quench time (<1 ns) attributed to their unique twinned microstructure.