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AbstractSimulations on the interaction between laser pulses with materials during pulsed laser ablation require information on the characteristics of both laser and material. While details on material properties are extensively studied, the temporal profile of the laser source term is rarely studied and is generally assumed to be Gaussian. This article explores the effects of non-Gaussian temporal laser source terms (TLSTs) in simulating the heat diffusion within a metal upon irradiation of femtosecond pulsed lasers. We employed the Two-Temperature Model (TTM) to simulate the temperature evolution on the surface of copper upon irradiation of a 100-fs laser pulse with different TLSTs at different laser repetition modes (single-shot, burst, and biburst). We used a constant total fluence of 3J/cm 2 in all cases and subsequently calculated the ablation depths based on the resulting temperature values. Our results show that non-Gaussian TLSTs generate lower electron and lattice temperatures, resulting in shallower crater depths compared to a Gaussian TLST. However, under burst and biburst modes, particularly with higher subpulse number repetition time, the results of non-Gaussian TLSTs approximate those of Gaussian TLSTs. To initiate laser ablation in such cases, higher laser fluence might be required. Our work on non-Gaussian temporal profiles in TTM simulations can be applied to other computational methods in describing laser-matter interaction. [ABSTRACT FROM AUTHOR]

Specific features of thermal transformations of ferrocene Fe(C5H5)2 at a pressure of 10 GPa upon laser heating to 2200 K have been investigated in diamond anvil cells. Maps of the temperature distribution on the sample during the heating have been obtained. The structure and properties of the transformation products have been studied by X-ray diffraction analysis, transmission electron microscopy, and Mössbauer spectroscopy. It is established that a characteristic feature of ferrocene transformations upon laser heating is the simultaneous formation of nanoparticles of iron (α-Fe) and iron carbide (Fe7C3) crystalline phases. The presence of α-Fe in the products of thermal transformations of ferrocene at high pressures has been observed for the first time. Possible mechanisms of the simultaneous formation of these nanoparticles during ferrocene transformations are discussed. [ABSTRACT FROM AUTHOR]

In this work, a novel approach involving coating fine PEEK powder on prepreg is introduced to improve wedge peel strength and reduce interlaminar voids. CF/PEEK laminates with resin interleaving are in situ consolidated by laser-assisted fiber placement. The morphology of the powdered surface is obtained using an optical profilometer, and the surface roughness and volume of added resin are calculated accordingly. Interface and surface temperature are measured during the layup process. Thermal history indicates that very short bonding time is the dominating factor for voids and limited interlayer strength. Laminate porosity and microscopic features are characterized with an optical microscope. The porosity of resin-interleaved laminates decreases to 3.7%, while the resin content only increases by 4.5% in the meantime. This is because interlayer resin particles rapidly melt under laser heating and quickly fill the voids between layers. The wedge peel strength of resin-interleaved laminates can increase by 30.1% without a repass treatment. This could be attributed to the increase in resin intimate contact and reduction in interlayer voids. [ABSTRACT FROM AUTHOR]

In this study, we report the synthesis of a new cubic neodymium-rhenium metallic alloy NdRe2 through the utilization of high pressure and laser heating in a diamond anvil cell. NdRe2 crystallizes in the … space group with a lattice parameter equal to 7.486 (2) Å and Z = 8 at 24 (1) GPa and 2,200 (100) K. It was studied using high-pressure single-crystal X-ray diffraction. The compound crystallizes in the cubic MgCu2 structure type. Its successful synthesis further proves that high-pressure high-temperature conditions can be used to obtain alloys holding a Laves phase structure. Ab initio calculations were done to predict the mechanical properties of the material. We also discuss the usage of extreme conditions to synthesize and study materials present in the nuclear waste. [ABSTRACT FROM AUTHOR]

In this study, we report the synthesis of a new cubic neodymium-rhenium metallic alloy NdRe2 through the utilization of high pressure and laser heating in a diamond anvil cell. NdRe2 crystallizes in the … space group with a lattice parameter equal to 7.486 (2) Å and Z = 8 at 24 (1) GPa and 2,200 (100) K. It was studied using high-pressure single-crystal X-ray diffraction. The compound crystallizes in the cubic MgCu2 structure type. Its successful synthesis further proves that high-pressure high-temperature conditions can be used to obtain alloys holding a Laves phase structure. Ab initio calculations were done to predict the mechanical properties of the material. We also discuss the usage of extreme conditions to synthesize and study materials present in the nuclear waste. [ABSTRACT FROM AUTHOR]

The macrosegregation evolution kinetics of undercooled Cu60Fe40 immiscible alloy during slow cooling and rapid cooling processes were investigated by laser heating and glass fluxing techniques. The critical undercooling for the occurrence of metastable phase separation (MPS) was determined as 41 K. As the undercooling rised, MPS always occurred even if the undercooling rised to the largest value of 482 K (0.28 TL) and the nucleation temperature of primary phase was below the peritectic temperature for the first time. Meanwhile, both the phase separation time and the volume fraction of Fe-rich zone gradually increased under the two conditions. However, the phase separation time and the volume fraction of Fe-rich zone under the laser heating condition were much smaller than that under the glass fluxing state. At slight undercoolings, MPS preferentially happened at the bottom region of laser-heated sample and glass-fluxed sample, and the microstructure in other regions appeared as well-defined αFe dendrites in the (Cu) matrix phase. In highly undercooled state, macrosegregation morphologies composed of floating Fe-rich zones and sinking Cu-rich zones were preserved. The critical undercooling for the macrosegregation formation of glass-fluxed sample was relatively larger. Moreover, the Fe-rich zone completely floated to the top of glass-fluxed sample while that located in the middle region of laser-heated sample. The higher the bulk undercooling, the lower the lattice constant of (Cu) phase and the greater the lattice constant of αFe phase. The calculations and analyses of temperature field and fluid dynamics demonstrated that the difference of heat transfer mechanisms between laser-heated sample and glass-fluxed sample was responsible for the distinctions of macrosegregation evolution kinetics in the two experiments. [ABSTRACT FROM AUTHOR]

Stimuli-responsive polymers are an important class of materials with many applications in nanotechnology and drug delivery. The most prominent one is poly-N-isopropylacrylamide (PNIPAm). The characterization of the kinetics of its change after a temperature jump is still a lively research topic, especially at nanometer-length scales where it is not possible to rely on conventional microscopic techniques. Here, we measured in real time the collapse of a PNIPAm shell on silica nanoparticles with megahertz x-ray photon correlation spectroscopy at the European XFEL. We characterize the changes of the particles diffusion constant as a function of time and consequently local temperature on sub-microsecond timescales. We developed a phenomenological model to describe the observed data and extract the characteristic times associated to the swelling and collapse processes. Different from previous studies tracking the turbidity of PNIPAm dispersions and using laser heating, we find collapse times below microsecond timescales and two to three orders of magnitude slower swelling times. [ABSTRACT FROM AUTHOR]

Recently, there has been a high demand for elucidating kinetics and visualizing reaction processes under extreme dynamic conditions, such as chemical reactions under meteorite impact conditions, structural changes under non-equilibrium conditions, and in situ observations of dynamic changes. To accelerate material science studies and Earth science fields under dynamic conditions, a submillisecond in situ X-ray diffraction measurement system has been developed using a diamond anvil cell to observe reaction processes under rapidly changing pressure and temperature conditions replicating extreme dynamic conditions. The development and measurements were performed at the high-pressure beamline BL10XU/SPring-8 by synchronizing a high-speed hybrid pixel array detector, laser heating and temperature measurement system, and gas-pressure control system that enables remote and rapid pressure changes using the diamond anvil cell. The synchronized system enabled momentary heating and rapid cooling experiments up to 5000 K via laser heating as well as the visualization of structural changes in high-pressure samples under extreme dynamic conditions during high-speed pressure changes. [ABSTRACT FROM AUTHOR]

In order to determine the influence of process parameters such as the optimal heating method, heating temperature, and time on the corrosion resistance of zinc iron alloy coatings, and to maximize their corrosion resistance while ensuring coating quality, a study was conducted on the influence of heating process on the corrosion resistance of zinc iron alloy coatings. Prepare coatings on steel-based materials using hot dip method, adjust the auxiliary plating and immersion temperatures, and test the corrosion resistance of coatings at different temperatures. After completing the coating preparation, test the corrosion resistance of the coating under two heating processes, namely, heating furnace and laser, as well as the corrosion morphology and corrosion rate of the coating under different heating temperatures. Calculate the corrosion loss of the coating under different heating durations. The experimental results show that the corrosion resistance of the coating is better when the auxiliary plating and immersion temperatures are 70 and 450°C, respectively. When the laser heating process is selected and the heating temperature does not exceed 450°C, the corrosion resistance of the coating is higher. Once the temperature is exceeded, the corrosion resistance of the coating decreases, and with the increase of heating time, the corrosion resistance of the coating will decrease. When the heating time is 14 min, the mass loss of the coating reaches 0.011 g. And in the electrochemical corrosion test, after soaking for 18 days, the polarization resistance value of the zinc iron alloy coating decreased to 987.8 Ω·cm2, achieving complete failure.

The optical properties of a photoluminescent material based on CsPbBr3 perovskite nanocrystals were studied in this work. The laser heating of the obtained samples was studied under three different regimes of laser excitation: the photoluminescence band appears in the Stokes region, in the anti-Stokes region, and coincides with the excitation line. It was found that under laser excitation of a certain wavelength, this material is able to demonstrate predominantly anti-Stokes (upconversion) photoluminescence. A method is proposed for estimating the PL quantum yield from data on absorption, photoheating, and the position of the photoluminescence band of a sample at two different wavelengths. The external photoluminescence quantum yield of CsPbBr3 nanocrystals was experimentally determined to be 91 ± 4%. The results of this work can be useful for the development of optical cooling technology and can be used in the development of laser devices based on perovskite materials. [ABSTRACT FROM AUTHOR]

Selective laser sintering (SLS) and multi jet fusion (MJF) are the most widespread powder bed fusion additive manufacturing techniques for fabricating polymeric parts since they offer great design flexibility, productivity, and geometrical accuracy. However, these technologies differ in the thermal energy source used to melt the powders as well as the innovative use of printing agents featured in the latter one to promote material consolidation and to avoid thermal bleeding at the part contours. The use of a single powder made of glass beads‐reinforced polyamide 12 (PA12/GB) for the fabrication of MJF and SLS samples makes possible a systematic comparison of the printed parts properties. A thoughtful analysis of the microstructure and mechanical properties of the samples reveals differences and peculiarities between the two technologies. SLS exhibits lower porosity and higher mechanical performances when the parts are printed along the build plane thanks to the powerful heating ensured by the laser. In contrast, MJF samples show higher mechanical isotropy with great flexural and tensile behavior for vertically oriented parts. The role of glass beads in the material behavior is defined by their mechanical properties, meaning higher rigidity and lower strength compared to neat PA12, and fracture mechanism. [ABSTRACT FROM AUTHOR]

Introduction: The purpose of this study is to achieve a significant increase in the proliferative activity of mesenchymal stem cells (MSCs) of the bone marrow (BM) at early passages after laser exposure to a suspension of these cells and to estimate the effect of light and heat components of laser radiation on the proliferation of BM MSCs. Methods: The studies were performed on rats BM MSCs. MSC suspension was placed into the wells and heated by using laser radiation (980 nm wavelength) or a water bath at 70 °C providing similar temperature dynamics. The studies were carried out in 3 comparison groups: (1) control suspension of MSCs, which was not subjected to heating in a water bath or laser exposure; (2) MSC suspension, which was heated for in a water bath; and (3) suspension of MSCs, which was subjected to laser exposure. The exposure times for the 2nd and 3rd experimental groups were 10-50 seconds. Results: Under optimal parameters of laser action on the suspension of BM MSCs, a six-fold increase in the number of BM MSCs colonies was registered compared to the control. The role of the light and heat components of laser exposure to MSCs was determined by comparable heating of a suspension of BM MSCs in a water bath, at which only a twofold increase in the number of colonies was maximally obtained. Conclusion: The increase in the MSC proliferation activity occurs due to their Thermo-Photobiomodulation. The result obtained is important for practical use in cell transplantation in the treatment of traumatic injuries of bone, cartilage, and tendon tissues when a rapid and multiple increase in the initial number of autologous BM MSCs is required. [ABSTRACT FROM AUTHOR]

In this article, we address the application of phase field crystal (PFC) theory, a hybrid atomistic-continuum approach, for modeling nanostructure kinetics encountered in laser deposition. We first provide an overview of the PFC methodology, highlighting recent advances to incorporate phononic and heat transport mechanisms. To simulate laser heating, energy is deposited onto a number of polycrystalline, two-dimensional samples through the application of initial stochastic fluctuations. We first demonstrate the ability of the model to simulate plasticity and recrystallization events that follow laser heating in the isothermal limit. Importantly, we also show that sufficient kinetic energy can cause voiding, which serves to suppress shock propagation. We subsequently employ a newly developed thermo-density PFC theory, coined thermal field crystal (TFC), to investigate laser heating of polycrystalline samples under non-isothermal conditions. We observe that the latent heat of transition associated with ordering can lead to long lasting metastable structures and defects, with a healing rate linked to the thermal diffusion. Finally, we illustrate that the lattice temperature simulated by the TFC model is in qualitative agreement with predictions of conventional electron–phonon two-temperature models. We expect that our new TFC formalism can be useful for predicting transient structures that result from rapid laser heating and re-solidification processes. [ABSTRACT FROM AUTHOR]

The effects of subsonic plasma flows of carbon dioxide and pure nitrogen combined with additional laser irradiation on silicon carbide material were investigated. Silicon carbide samples were exposed to temperatures from 1480 to 1620°C (in the carbon dioxide plasma flow) and from 1600 to 1960°C (in the pure nitrogen plasma flow) at a constant pressure in the test chamber of 1 × 104 Pa and gas mass flow rate of 2.4 g/s. Significant differences in the heat transfer and behavior of the samples were observed depending on the plasma composition. The microstructure and surface profiles of the samples before and after different exposures were compared. Surface peculiarities were detected in the areas where the maximum laser irradiation intensity was applied. [ABSTRACT FROM AUTHOR]

The effects of heat treatment with continuous laser radiation on samples of the Fe–18Cr–10Ni alloy of the austenitic-martensitic class that have undergone preliminary megaplastic torsional deformation in the Bridgman chamber are investigated. It is established that the combined application of deformation (deformation in the Bridgman chamber) and thermal (laser heating) effects to the alloy forms the structure of metastable austenite (γ phase), which differs from stable austenite in higher strength characteristics. The nature of this phenomenon is discussed. [ABSTRACT FROM AUTHOR]

Two-dimensional nanomaterials have obvious advantages in thermoelectric device development. It is rare to use the same experimental system to accurately measure multiple thermoelectrical parameters of the same sample. Therefore, scholars have developed suspended microdevices, T-type and H-type methods to fulfill the abovementioned requirements. These methods usually require a direct-current voltage signal to detect in Seebeck coefficient measurement. However, the thermoelectric potential generated by the finite temperature difference is very weak and can be easily overwritten by the direct-current voltage, thereby affecting the measurement accuracy. In addition, these methods generally require specific electrodes to measure the thermoelectric potential. We propose a measurement method that combines laser heating with an H-type device. By introducing a temperature difference in two-dimensional materials through laser heating, the thermoelectric potential can be accurately measured. This method does not require specific electrodes to simplify the device structure. The thermoelectrical parameters of supported graphene are successfully measured with this method; the results are in good agreement with the literature. The proposed method is unaffected by material size and characteristics. It has potential application value in the characterization of thermoelectric physical properties. [ABSTRACT FROM AUTHOR]

The field of nanowire (NW) technology represents an exciting and steadily growing research area with applications in ultra-sensitive mass and force sensing. Existing detection methods for NW deflection and oscillation include optical and field emission approaches. However, they are challenging for detecting small diameter NWs because of the heating produced by the laser beam and the impact of the high electric field. Alternatively, the deflection of a NW can be detected indirectly by co-resonantly coupling the NW to a cantilever and measuring it using a scanning probe microscope. Here, we prove experimentally that co-resonantly coupled devices are sensitive to small force derivatives similar to standalone NWs. We detect force derivatives as small as 10−9 N/m with a bandwidth of 1 Hz at room temperature. Furthermore, the measured hybrid vibration modes show clear signatures of avoided crossing. The detection technique presented in this work verifies a major step in boosting NW-based force and mass sensing. Flexural oscillations of singly-clamped nanowires can be detected by interferometry for diameters above 50 nm, while below such diameter the detection becomes challenging. The authors detect force derivatives as small as 10-9 N/m at room temperature by measuring hybrid vibration modes originated by coupling a nanowire and a cantilever. [ABSTRACT FROM AUTHOR]

Boron particles in solid-fuel ramjet combustion chambers typically exist in agglomerated form, and the gas composition within the chamber includes not only air but also propellant combustion products such as water vapor and CO2. This study investigates the thermal behavior, laser heating characteristics, and condensed-phase heating products of boron agglomerates in six distinct atmospheres: N2, O2, air, water vapor, CO2, and Ar. Thermal oxidation tests revealed that the reaction between boron and O2 dominates in an air atmosphere, while boron can still react with N2 in air to form granular boron nitride. Laser-induced heating resulted in ejection phenomena occurring in boron agglomerates when subjected to N2, air, water vapor, Ar, or O2 atmospheres, with the O2 atmosphere being the most conducive, exhibiting an average of 47 occurrences for individual agglomerates. The ejection process and frequency were found to be comparable in the air, Ar, and water vapor atmospheres, with an average ejection frequency ranging from 7 to 11 times. Although the ejection phenomenon occurred in the N2 atmosphere, its frequency was low, with an average of only two occurrences. Agglomerates underwent significant expansion before ejection, while single-particle boron did not exhibit ejection or expansion in any of these atmospheres. The highest surface temperatures of boron agglomerates upon laser heating in air, water vapor, N2, and Ar atmospheres were 2697.7 K, 2416.2 K, 2408.9 K, and 2392.1 K, respectively. Analysis of condensed-phase heating products revealed that boron agglomerates reacted with N2 or CO2 to form boron nitride or boron carbide, respectively. [ABSTRACT FROM AUTHOR]

This work reports results on the simultaneous spectroscopy of the specific heat and thermal expansivity of glycerol by making use of a wideband time-resolved thermal lens (TL) technique. An analytical model is presented which describes TL transients in a relaxing system subjected to impulsive laser heating. Experimentally, a set of TL waveforms, from 1 ns to 20 ms, has been recorded for a glycerol sample upon supercooling, from 300 to 200 K. The satisfactory fitting of the TL signals to the model allows the assessment of relaxation strength and relaxation frequency of the two quantities up to sub-100 MHz, extending the specific heat and thermal expansion spectroscopy by nearly three and eight decades, respectively. Fragility values, extracted from the relaxation behavior of the specific heat and the thermal expansion coefficient, are found to be similar, despite a substantial difference in relaxation strength. [ABSTRACT FROM AUTHOR]

Through a series of high-pressure x-ray diffraction experiments combined with in situ laser heating, we explore the pressure–temperature phase diagram of germanium (Ge) at pressures up to 110 GPa and temperatures exceeding 3000 K. In the pressure range of 64–90 GPa, we observe orthorhombic Ge-IV transforming above 1500 K to a previously unobserved high-temperature phase, which we denote as Ge-VIII. This high-temperature phase is characterized by a tetragonal crystal structure, space group I4/mmm. Density functional theory simulations confirm that Ge-IV becomes unstable at high temperatures and that Ge-VIII is highly competitive and dynamically stable at these conditions. The existence of Ge-VIII has profound implications for the pressure–temperature phase diagram, with melting conditions increasing to much higher temperatures than previous extrapolations would imply. [ABSTRACT FROM AUTHOR]

Raman spectroscopy has become the tool of choice for analyzing fluid inclusions and melt inclusion (MI) vapor bubbles as it allows the density of CO2-rich fluids to be quantified. Measurements are often made at ambient temperature (Tamb ~18-25 °C), resulting in reported bulk densities between 0.2 and 0.7 g/mL despite that single-phase CO2 under these conditions is thermodynamically unstable and instead consists of a liquid (~0.7 g/mL), and a vapor phase (~0.2 g/mL). Here, we present results from experiments conducted at Tamb and 37 °C (above the CO2 critical temperature) on 14 natural CO2-rich MI bubbles from Mount Morning, Antarctica. Here, we show that at Tamb, laser power strongly affects the CO2 Raman spectrum of MI bubbles with bulk densities within the miscibility gap. High-power laser heating and low spectral resolution explain why published measurements have reported such bulk densities at Tamb even when using an instrument-specific calibration.

As device length scales trend downward, small feature sizes and steep temperature gradients require thermometers with increasingly fine spatial resolution in order to capture the true peak temperature. Here, we develop analytical expressions for the true and measured temperature rises as a function of thermometer size for Gaussian, disk-shaped, and rectangular surface heat sources. We find that even a thermometer the same size as the hotspot can underestimate the true peak temperature rise by more than 15%, and this error frequently exceeds 75% and can approach 90% for certain geometries when the thermometer is ten times larger than the measured hotspot. We show that a thermometer with resolution approximately two times smaller than the hotspot size is required to measure the peak temperature rise with less than 5% error for several common hotspot geometries. We also experimentally demonstrate that a 50 × 50 × 50 nm3 individual upconverting NaYF4:Yb3+,Er3+ nanoparticle thermometer captures the peak temperature rise due to laser heating more accurately than conventional diffraction limited optical techniques that our modeling results show would underestimate this value. In contrast to apparent self-heating effects that spuriously increase the nanoparticle thermometry signal at high excitation intensities, we measure true laser heating, as confirmed by comparing measurements on glass and diamond substrates. [ABSTRACT FROM AUTHOR]

A simple kHz-rate spectral phosphor thermometry technique with sub-millisecond temporal resolution for contactless point measurements of short duration transient surface temperature changes was developed by employing a compact high-speed fiber-optic spectrometer, a high repetition rate pulsed green laser, and a fast decaying thermographic phosphor. Temperature changes were determined from the temperature-dependent emission spectra of the YAG:Ce phosphor using a spectral slope method. The precision of single-shot temperature measurements was better than 4% for temperatures up to 700 K. An application of the technique for time-resolved measurements of local transient temperature changes at 5 kHz during repetitive long CO2 laser pulse heating is presented. The measured temperature transients are well-predicted using a two-dimensional axisymmetric heat transfer model. [ABSTRACT FROM AUTHOR]

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 %.

The expansion and collapse of a cavitation bubble during laser heating and subcooled boiling of water in the vicinity of the tip of an optical fiber (laser heating element) installed in a water-filled glass tube with two open ends is studied experimentally and numerically. Cavitation, initiated by continuous laser radiation, is accompanied by the pushing and pulling movement of the heated liquid in the tube and outside it. For the first time, it has been shown that in a tube with an installed laser heating element in a liquid flow moving behind the walls of the bubble, when it collapses at the pole of the bubble surface remote from the end, a liquid jet appears, directed through the bubble to the end of the optical fiber. The jet speeds up the process of sucking liquid into the tube. [ABSTRACT FROM AUTHOR]

We report the P-V-T equation of state measurements of B4C to 50 GPa and approximately 2500 K in laser-heated diamond anvil cells. We obtain an ambient temperature, third-order Birch–Murnaghan fit to the P-V data that yields a bulk modulus K0 of 221(2) GPa and derivative, (dK/dP)0 of 3.3(1). These were used in fits with both a Mie–Grüneisen–Debye model and a temperature-dependent, Birch–Murnaghan equation of state that includes thermal pressure estimated by thermal expansion (α) and a temperature-dependent bulk modulus (dK0/dT). The ambient pressure thermal expansion coefficient (α0 + α1T), Grüneisen γ(V) = γ0(V/V0)q and volume-dependent Debye temperature, were used as input parameters for these fits and found to be sufficient to describe the data in the whole P-T range of this study. This article is part of the theme issue 'Exploring the length scales, timescales and chemistry of challenging materials (Part 1)'. [ABSTRACT FROM AUTHOR]

The local modification of the material properties, especially in the case of Aluminium alloys, is considered a promising solution to overcome the poor formability at room temperature. According to this approach, the Aluminium blank is preliminary subjected to a short-term local heat treatment (usually by laser heating) and then, once cooled down to room temperature, subjected to the forming operations. The present work proposes a numerical methodology to predict the effect of a laser heating, locally bringing a AA5754-H32 blank to the fully annealed state. The Gleeble 3180 physical simulator was used to reproduce the annealing laser treatment by heating AA5754-H32 striped samples under different conditions of time and temperature: specimens, once cooled down to room temperature, were then subjected to hardness measurement and the resulting data used to calibrate a sigmoid function describing the level of annealing according to the time and the maximum temperature reached during the heat treatment. The logistic function was then implemented in a python script able to post-process the results from a thermal transient simulation and, by extracting the temperature history from each node, predict the final distribution of properties. The methodology is then validated by comparing the predicted distribution of properties and the measured one on AA5754-H32 samples subjected to different laser heating strategies. [Display omitted] • The proposed methodology is based on data efficiently obtained by physical simulation tests. • Degree of Annealing (DoA) is related to time and temperature by a sigmoid function. • FE simulations implementing the DoA sigmoid function accurately predicts the laser annealing. • FE predictions are validated by Vickers hardness measurements. • The proposed methodology is versatile and can be applied to different alloys. [ABSTRACT FROM AUTHOR]

High-Q optical microresonators are particularly efficient practical tools of modern applied optics and photonics. Using them, one inevitably faces the problem of thermal effects. Accurate determination of effective thermal parameters of high-Q microresonators (effective thermal relaxation rate and optical absorption rate) is of particular importance for developing microresonator-based devices. Our investigation looks into diverse methodologies to estimate these effective parameters for such systems, ultimately revealing a divergence between the commonly employed simplified model, the direct numerical approach, and classical analytical formulas. We introduce a novel approach to calculate effective parameters based on the decomposition of the thermal field into microresonator thermal modes, which inherently considers the intricate geometry and material anisotropy inherent in microresonators, as well as the influence of external conditions. The method for the accurate determination of the effective thermal parameters of the microresonator for corresponding thermal modes is developed. As a result of applying this method, we modified the classical approach for the simulation of thermal effects in optical microresonators for better agreement with the numerical simulations. By accounting for the complexities of microresonator shapes, material properties, and external factors, our proposed method contributes to a more accurate understanding of thermal dynamics and enhances the predictive capabilities of simulations for these systems. We demonstrated the application of this method on the example of integrated microring resonators, but it can be used to analyze thermal effects in other microresonator platforms. [ABSTRACT FROM AUTHOR]

The features of oxidation of ultra-high-temperature ceramic material HfB2-30 vol.%SiC modified with 1 vol.% graphene as a result of supersonic flow of dissociated CO2 (generated with the use of high-frequency induction plasmatron), as well as under the influence of combined heating by high-speed CO2 jets and ytterbium laser radiation, were studied for the first time. It was found that the addition of laser radiation leads to local heating of the central region from ~1750 to ~2000–2200 °C; the observed temperature difference between the central region and the periphery of ~300–550 °C did not lead to cracking and destruction of the sample. Oxidized surfaces and cross sections of HfB2-SiC-CG ceramics with and without laser heating were investigated using X-ray phase analysis, Raman spectroscopy and scanning electron microscopy with local elemental analysis. During oxidation by supersonic flow of dissociated CO2, a multilayer near-surface region similar to that formed under the influence of high-speed dissociated air flows was formed. An increase in surface temperature with the addition of laser heating from 1750–1790 to 2000–2200 °C (short term, within 2 min) led to a two to threefold increase in the thickness of the degraded near-surface area of ceramics from 165 to 380 microns. The experimental results indicate promising applications of ceramic materials based on HfB2-SiC as part of high-speed flying vehicles in planetary atmospheres predominantly composed of CO2 (e.g., Venus and Mars). [ABSTRACT FROM AUTHOR]

Optical tweezers have profound importance across fields ranging from manufacturing to biotechnology. However, the requirement of refractive index contrast and high laser power results in potential photon and thermal damage to the trapped objects, such as nanoparticles and biological cells. Optothermal tweezers have been developed to trap particles and biological cells via opto-thermophoresis with much lower laser powers. However, the intense laser heating and stringent requirement of the solution environment prevent their use for general biological applications. Here, we propose hypothermal opto-thermophoretic tweezers (HOTTs) to achieve low-power trapping of diverse colloids and biological cells in their native fluids. HOTTs exploit an environmental cooling strategy to simultaneously enhance the thermophoretic trapping force at sub-ambient temperatures and suppress the thermal damage to target objects. We further apply HOTTs to demonstrate the three-dimensional manipulation of functional plasmonic vesicles for controlled cargo delivery. With their noninvasiveness and versatile capabilities, HOTTs present a promising tool for fundamental studies and practical applications in materials science and biotechnology. Traditional optical tweezers require high laser powers risking photothermal damage of the trapped objects. Here, the authors present hypothermal opto-thermophoretic tweezers (HOTTs), which use environmental cooling to simultaneously enhance thermophoretic trapping force at low laser powers and suppress the thermal damage to trapped objects. [ABSTRACT FROM AUTHOR]

Combining experimental set up and ab initio molecular dynamics simulations, we were able to follow the time evolution of the X-ray absorption near edge spectrum (XANES) of a dense copper plasma. This provides a deep insight into femtosecond laser interaction with a metallic copper target. This paper presents a review of the experimental developments we made to reduce the X-ray probe duration, from approximately 10 ps to fs duration with table-top laser systems. Moreover, we present microscopic scale simulations, performed with Density Functional Theory, as well as macroscopic simulations considering the Two-Temperature Model. These tools allow us to get a complete picture of the evolution of the target at a microscopic level, from the heating process to the melting and expansion stages, with a clear view of the physics involved during these processes. This article is part of the theme issue 'Dynamic and transient processes in warm dense matter'. [ABSTRACT FROM AUTHOR]

Ochratoxin A (OTA) is a widespread mycotoxin that causes contamination in a variety of foodstuffs and environments, inducing great health risks to humans and animals. Rapid and sensitive detection of OTA is necessary for food safety, environmental health, and risk assessment. Herein, we report an aptamer microscale thermophoresis (MST) assay for OTA, with the unique merits of ratiometric analysis, rapid measurement, simple operation, high sensitivity, low sample consumption, and high throughput. A fluorescein (FAM)-labeled high-affinity DNA aptamer with a G-quadruplex and duplex structure was used as the recognition element for OTA, and MST, which measures the fluorescence responses of the sample solution inside capillaries to a mild temperature increase generated by infrared laser heating, was employed for signal generation. Upon OTA binding, the FAM-labeled aptamer probe underwent changes in conformation and stability, and the bound and unbound aptamer probes showed significant differences in their MST signals. To achieve sensitive detection of OTA with a large signal change, we systematically characterized aptamers with different stem lengths, which had large effects on the MST responses of the aptamer probes to OTA. We found that a 32-mer aptamer with FAM label at the 3′ end gave a sensitive MST response to OTA, allowing OTA detection within seconds with a detection limit of 0.98 nM under optimal experimental conditions. This aptamer MST assay shows potential in real sample analysis and broad applications. [ABSTRACT FROM AUTHOR]

We report on a facile and low-cost method for the site-specific fabrication of carbon microelectrodes on a NiFe thin film-coated substrate by laser-induced heating of the NiFe layer immersed in ethanol. Raman spectroscopy analysis of the carbon materials synthesized confirms that, after optimization of the laser heating conditions (in terms of laser power, irradiation time, and the number of radiation bursts), the G band peak in the Raman spectra is increased and sharpened and the D/G ratio improved. In addition, from the scanning electron microscopy and energy-dispersive X-ray spectroscopy measurements, we find that the laser-irradiated site is rich in particle-like graphitic nanomaterials with nano-sized grains that are densely distributed on the NiFe substrate. Furthermore, conductive atomic force microscopy measurements show that optimized irradiation conditions enable not only the localized formation of low-D/G-Raman-peak-ratio graphitic nanomaterials with good conductivity but also an increase of the current flow in the laser-irradiated area, reaching current values much higher than that of the bare NiFe thin film. From these results, we conjecture that nanocrystalline-like graphitic nanomaterials with fewer structural defects and good conductivity are synthesized in the laser-irradiated area. This laser-induced graphitic nanomaterials synthesis method can potentially be adapted to directly and locally form carbon microelectrodes on magnetic thin films, offering unique advantages for the development of micromagnetic devices. [ABSTRACT FROM AUTHOR]

The heat transfer to a cylindrical water-cooled copper model was experimentally investigated in an induction VGU-4 high-frequency (HF) plasmatron of the Institute for Problems in Mechanics of the Russian Academy of Sciences. The model, 30 mm in diameter, equipped with a calorimetric transducer with a heat-adsorbing graphite surface, 13.8 mm in diameter, was exposed to the surface heating in the combined regime by nitrogen plasma and laser radiation and in the cases of the heating with only laser radiation or a nitrogen plasma jet. The experiments in the HF-plasmatron jets were performed at the pressure in the setup low-pressure chamber p = 1 × 104 Pa, nitrogen mass flow rate G = 2.4 g/s, and the plasmatron HF-generator anode power Na.p. = 22 kW. It is established that in the chosen experimental regimes the dissociated-nitrogen jet and the high-frequency induction discharge do not produce a considerable effect on the laser beam passing through them. The values of the heat flux density are obtained as functions of the laser radiation power delivered. The subsonic nitrogen plasma flow in the quartz discharge channel and in the low-pressure chamber of the VGU-4 setup is numerically modeled under the experimental conditions basing on the solution of the complete Navier–Stokes equations using the Patankar–Spalding method. [ABSTRACT FROM AUTHOR]

This paper studies the effect of the laser melting process (LMP) on the microstructure and hardness of a new modified AlCuMgMn alloy with zirconium (Zr) and Yttrium (Y) elements. Homogenized (480 °C/8 h) alloys were laser-surface-treated at room temperature and a heating platform with in situ heating conditions was used in order to control the formed microstructure by decreasing the solidification rate in the laser-melted zone (LMZ). Modifying the AlCuMgMn alloy with 0.4 wt% Zr and 0.6 wt% Y led to a decrease in grain size by 25% with a uniform grain size distribution in the as-cast state due to the formation of Al3(Y, Zr). The homogenization dissolved the nonequilibrium intermetallic phases into the (Al) matrix and spheroidized and fragmentized the equilibrium phase's particles, which led to the solidification of the crack-free LM zone with a nonuniform grain structure. The microstructure in the LMZ was improved by using the in situ heating approach, which decreased the temperature gradient between the BM and the melt pool. Two different microstructures were observed: ultrafine grains at the boundaries of the melted pool due to the extremely high concentration of optimally sized Al3(Y, Zr) and fine equiaxed grains at the center of the LMZ. The combination of the presence of ZrY and applying a heating platform during the LMP increased the hardness of the LMZ by 1.14 times more than the hardness of the LMZ of the cast AlCuMgMn alloy. [ABSTRACT FROM AUTHOR]

In this paper, a thermal–mechanical–oxidation coupling experimental system based on laser heating is developed, containing two modes of Gaussian and flat-top lasers, which has a series of advantages such as high temperature range, rapid heating rate, and convenient observation. The system adopts active illumination and an optical filter to solve the problem where it is difficult for traditional digital-image correlation technology to image clearly under laser heating. A biaxial mechanical test machine is used to simulate the complex load by applying biaxial tension or compression loads on the material. Combined with the radiation temperature measurement and controllable flow field device, the thermal-mechanical-oxygen coupling experiment of high temperature resistant materials under aerobic environment can be carried out. The maximum uniform heat flux output density is 27.2 kW/cm2, and the maximum Gaussian heat flux output density is 105 kW/cm2. The thermal-mechanical-oxygen coupling experimental system and method are of great significance to the development of new high temperature resistant materials and thermal barrier coatings. [ABSTRACT FROM AUTHOR]

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The combination of laser irradiation heating and synchrotron X-ray sources has made it possible to observe the fiber-structure development that occurs at sub-millisecond timescales after necking during continuous drawing. Through wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) analysis of poly(ethylene terephthalate) fibers of three different molecular weights drawn under equivalent stresses, a good correlation was observed between the d-spacing of smectic (001ʹ) diffraction extrapolated to the necking point and the strength of the drawn fiber. This indicates that the molecular chains that bear the drawing stress also bear most of the applied stress during tensile testing of the resultant fiber. In addition, considering the drawing-stress dependence of the d-spacing and the molecular weight distribution of the fiber revealed that molecular chains with molecular weights over 23,000 g/mol bear the majority of tensile force applied to the fiber. [ABSTRACT FROM AUTHOR]

An experimental installation for laser heating (ULN-1) has been developed to implement a technique for identifying mathematical models of radiative-conductive heat transfer without using contact measurements. A substantiation of the choice of the system components and of the procedure for its application is given. Approbation of the installation and of the identification technique was carried out on the example of determining the thermophysical characteristics of a thin plate made of an opaque material. [ABSTRACT FROM AUTHOR]

Three different types of TiO2 nanoparticles in anatase and rutile phases were subject to nanosecond 532‐nm laser pulses in aqueous solution for enhanced reactivity in photocatalytic applications. Color changes observed during the laser processes resulted from laser pulse‐induced heating of TiO2 surfaces to form surface disorder with surface defects. Interestingly, TiO2 nanoparticles with different size and bulk phases undergo different changes in surface morphology, bulk phase, and defect density under the same laser pulses. The results are related with the differences in the absorption by initial defects on the TiO2 surface. Our results show that the type and density of initial defects within TiO2 matrix are important in determining subsequent thermal equilibrium‐driven changes. It is suggested that nanosecond laser pulses with energies lower than the bandgap of the semiconductor materials provide a chance for selective modification of oxide nanomaterials such as TiO2 for a new photoresponsive functionality in diverse applications. [ABSTRACT FROM AUTHOR]

Threshold properties and pulsed output of AlGaInP visible-emitting lasers with an asymmetric waveguide structure and a bulk active layer are analysed. The effects of the current leakage, increased by the heating of the laser due to the proximity of the electrical pulse source and the Joule heating in and around this source are analysed. When optimising the laser design, waveguiding properties of the bulk active layer are shown to be important, leading to threshold currents decreasing, and injection efficiency increasing, with active layer thickness in lasers with moderately thick (< 0.1 μm) active layers. [ABSTRACT FROM AUTHOR]

We present a sessile droplet manipulation platform that enables the formation and transport of a droplet on a light-absorbing surface via local laser-beam irradiation. The mechanism relies on solutocapillary Marangoni flow arising from a concentration gradient in a binary mixture liquid. Because the mixture is strongly confined in a two-dimensional slit with a spacing of a few micrometers, the wetting film is stably sustained, enabling the rapid formation, deformation, and transport of a sessile droplet. In addition, to sustain the droplet in the absence of laser irradiation, we developed a method to bridge the droplet between the top and bottom walls of the slit. The bridge is stably sustained because of the hydrophilicity of the slit wall. Splitting and merging of the droplet bridges are also demonstrated. [ABSTRACT FROM AUTHOR]

Determination of the iron oxide nanoparticles (IONPs) local temperature during laser heating is important in the aspect of laser phototherapy. We have carried out theoretical modeling of IONPs local electromagnetic (EM) field enhancement and heating under the laser action near individual IONPs and ensembles of IONPs with different sizes, shapes and chemical phases. For experimental determination of IONPs temperature, we used fluorescence thermometry with rhodamine B (RhB) based on its lifetime. Depending on the IONPs shape and their location in space, a significant change in the spatial distribution of the EM field near the IONPs surface is observed. The local heating of IONPs in an ensemble reaches sufficiently high values; the relative change is about 35 °C for Fe2O3 NPs. Nevertheless, all the studied IONPs water colloids showed heating by no more than 10 °C. The heating temperature of the ensemble depends on the thermal conductivity of the medium, on which the heat dissipation depends. During laser scanning of a cell culture incubated with different types of IONPs, the temperature increase, estimated from the shortening of the RhB fluorescence lifetime, reaches more than 100 °C. Such "hot spots" within lysosomes, where IONPs predominantly reside, lead to severe cellular stress and can be used for cell therapy. [ABSTRACT FROM AUTHOR]

Double layers of deuterated and hydrogenated amorphous silicon (a‐Si:H) on glass are heated in the ambient by scanning with a green (532 nm) continuous wave laser. The hydrogen diffusion length in the laser spot is obtained from the deuterium (D)–hydrogen (H) interdiffusion measured by secondary ion mass spectrometry (SIMS), the temperature in the laser spot is obtained by calculation. Under certain conditions, detachment of the deuterated layer from the hydrogenated layer is observed in the SIMS depth profiles, visible by rising oxygen and carbon signals at the D/H interface attributed to in‐diffusion of atmospheric gas species like water vapor, oxygen, and carbon oxide. Stacks involving both undoped and boron‐doped a‐Si:H films show disintegration. The results suggest that the parameters leading to the disintegration effects are the presence of a plane of reduced material cohesion at the D/H interface, a sizeable H diffusion length and a rather high heating rate. Herein, it is likely considered that the observed layer disintegration process is involved in the peeling of a‐Si:H films upon fast heating. Furthermore, the results show that rapid laser heating can be used to detect planes of reduced material cohesion which may compromise the electronic properties of a‐Si:H‐based stacks. [ABSTRACT FROM AUTHOR]

3D printing of continuous fiber reinforce plastics (CCFRP) with fused deposition modeling is a burgeoning manufacturing method because of its exceptional mechanical properties. Nevertheless, it cannot manufacture parts at high speeds. Using laser heating instead of the traditional resistive heating in 3D printing of CCFRP has the potential to improve printing speed owing to its high heating efficiency. In this article, a process of laser‐assisted rapid 3D printing of CCFRP is proposed. The heating process of CCFRP by laser is analyzed and verified. The linear relation between printing speed and laser power is established. The experiments demonstrate that the printing speed is increased to 30 mm/s with the laser. The mechanical properties of printed parts, though enhanced as the printing speed and laser power increase, are better than those obtained by traditional methods. Scanning electron microscope images and experiments reveal that proper laser power is conducive to the melting of plastics, strengthening interlayer bonding, and reducing voids under roller pressure. Nonetheless, excessive laser power ablates the plastic, resulting in increased voids. [ABSTRACT FROM AUTHOR]

New generations of fusion devices need alternative plasma-facing materials. The currently approved material composition for the first wall and divertor of the ITER tokamak has a number of disadvantages: insufficient resistance to thermal shock, sputtering of microparticles into plasma and high atomic number Z of the armor material. A promising but largely untested idea is the proposal to use high-temperature ceramics as armor materials for the most heat-loaded plasma-facing components of new-generation fusion devices. Among the advantages of ceramics are the low Z and high enough resistance to intense heating. More research is needed that would help to understand how the material withstands high heat fluxes during transient plasma events. This work is devoted to the description of an experimental method that makes it possible to estimate the critical temperature at which the damage of ceramics begins as a result of a thermal shock of submillisecond duration. As a demonstration of the efficiency of the method, the critical temperature for hot pressed B4C under thermal shock was determined: its value was about 1200–1400 K.

We have developed nano/microscale thermal impulse (TI) (i.e., temperature and duration) sensors for use in extreme environments such as explosions, furnaces, and combustion experiments. These sensors consist of chemically bonded precursor Eu : ZrO 2 and precursor Dy : Y 2 O 3 , which are prepared via mixed coprecipitation. In this study, we demonstrate their functionality for subsecond pulsed laser heating (isothermal duration of ≈ 10 ms) up to 1773 K, with evidence suggesting functionality to even higher temperatures. This large range is due to the formation of a new mixed-material phase (similar to yttria-stabilized zirconia) that results in spectral features that are not seen in the component materials on their own. To the best of our knowledge, this material has the largest functional temperature range of any ex situ TI sensor reported in the literature. [ABSTRACT FROM AUTHOR]

Laser heating in a diamond anvil cell (DAC) is a common method for studying material behavior at high-pressure and high-temperature conditions. It has been previously proven that during continuous wave (CW) laser heating of a sample, carbon of the diamond anvils is mobilized, and its diffusion into the sample can lead to undesirable chemical reactions, which, if not detected, may cause misinterpretations of the results of the experiment. Minimizing the heating time with the use of a pulsed laser (PL) is thought to reduce the risk of possible carbon contamination of the sample; however, this has not been proven experimentally. Here, we report the results of our comparative study of the effect of pulsed and continuous wave (CW) laser heating on the mobilization of carbon and its chemical interaction with iron in a diamond anvil cell. Using X-ray absorption near edge structure spectroscopy, Synchrotron Mössbauer Source spectroscopy, and Synchrotron X-ray diffraction, we examined iron samples that were laser heated in DACs in various pressure transmitting media (neon, argon, and potassium chloride). According to our results, the use of the PL heating does not prevent the sample from carbon contamination. A reaction between carbon and iron happens within a few seconds even at moderate temperatures. We found that one analytical technique was generally insufficient to fully characterize the phase composition of the laser-heated samples. [ABSTRACT FROM AUTHOR]