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In non-destructive testing for metallic materials, 'Flying-spot' thermography allows the detection of cracks thanks to the scanning of samples by a local laser heat source observed in the infrared spectrum. However, distinguishing a crack from other surface structures such as air ducts or non-planar shapes on the material surface can be challenging in an automation perspective. To address this, we propose to use deep learning techniques, which can exploit contextual information but require a significant amount of labelled data. This study presents a training method based on curriculum learning and recent denoising diffusion models to generate synthetic images. The protocol progressively increases the complexity of training images, using successively simulated data from a multi-physics finite-element software, synthetically generated data with diffusion process, and finally real data. Several detection scores are measured for various machine learning and deep learning architectures, demonstrating the benefits of the proposed approach for regular application cases and degraded experimental conditions, consisting of limited thermal enlightenment recordings. [ABSTRACT FROM AUTHOR]

AbstractThis paper aims to investigate the transient thermo-viscoelastic memory-dependent responses of the temperature-dependent laminated polymethyl methacrylate (PMAA) composites with imperfect interfaces, of which the bounding surface subjected to non-Gauss laser heating loads, are investigated based on integral-type non-Fourier thermo-viscoelasticity model with memory-dependent derivative (MDD). The Laplace transformation is used to solve the multi-physics differential governing equations. The influences of the viscoelastic material constants ratios, temperature-dependent parameters, laser parameters, memory-dependent parameters and kernel functions on the responses are elucidated to offer guidelines to thermal control and mechanical strength evaluation for the laminated PMMA composites. [ABSTRACT FROM AUTHOR]

The thermo-mechanical coupled behavior of biological tissues excited by a transient heating has been studied in this paper, in which the temperature-dependent physical properties are considered. A non-linear bio-thermo-mechanical coupled model with variable physical parameters has been proposed firstly in the context of the generalized theory with the dual-phase relaxation mechanism. An effective procedure constructed on an explicit finite difference scheme is then implemented to solve this non-linear model numerically. On this basis the thermo-mechanical coupled response and relative thermal damage within a skin tissue irradiated by a pulse laser has been explored. The temporal and spatial distributions of each physical field resulting from various cases have been obtained and illustrated. The results stated that the thermo-mechanical interaction induced by a laser heating would be inhibited by temperature-dependent physical parameters and this inhibition is more significant on the tissue displacement and normal stresses than tissue temperature. The thermal damage is also inhibited when the temperature dependence is considered and the time that healthy tissues can be tolerated would be a larger extension for its accumulative effect with tissue temperature. [ABSTRACT FROM AUTHOR]

The article presents the estimation of temperature and emissivities of niobium and 100c6 steel around their melting points using techniques based on the minimization of the least squares norm or on Bayesian inference. Two models were considered for the spectral emissivity, including a linear variation with respect to the wavelength and independent spectral values. The measured data used for the solution of the parameter estimation problem were radiative fluxes collected from a five-wavelength pyrometer. The experimental apparatus used in this work was designed for the characterization of metal samples with sizes of few millimeters at high temperatures, combining aerodynamic levitation and laser heating. The use of the linear spectral emissivity model provided quite consistent results with the ordinary least squares estimator and with stochastic simulations using the Metropolis-Hastings algorithm. Similarly, the model of independent spectral emissivities resulted in accurate emissivities, but it required an informative prior for temperature, such as the known melting point of the metal sample. Therefore, whatever the inverse method used, a priori supplementary information in terms of emissivities or temperatures are needed due to the temperature-emissivity correlation and the unknow emissivity behavior. [ABSTRACT FROM AUTHOR]

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]

In this work, laser heating is used to experimentally investigate the high-temperature behavior of the U-Fe-Zr-O system using arc-melted samples with various nominal compositions. Three-phase transitions are observed in the vicinity of ~1100, ~1700, and ~2200 K. Principal component analysis of the phase transition temperatures in the course of laser-heating thermal cycling indicates that the phase transition around ~1100 K is driven by the interaction of stainless steel (SS) with metallic U, the phase transition around ~1700 K by the melting of stainless steel, and the phase transition above ~2000 K by the eutectic melting of UO2. The results also reveal two hitherto overlooked interactions in the U-Fe-Zr-O system, which could have severe consequences for the containment of corium inside the reactor pressure vessel (RPV). First, the phase transition temperatures of the samples varied extensively as a result of the laser-driven rapid thermal cycling. Variations of up to 390 K were observed in the phase transition temperatures, suggesting that depending on the initial conditions of corium formation, the corium-driven ablation of the RPV wall could commence significantly earlier than the current state-of-the-art severe accident codes would predict. Additionally, evidence of a large exothermic reaction between zirconium and molten steel was observed upon SS melting. Such phenomenon may also be driven by material segregation during fast heating and cooling. If such a mechanism is activated during a severe nuclear accident, it can have an important impact on the overall thermal balance of the RPV. [ABSTRACT FROM AUTHOR]

The current research focuses on laser melting and successive analysis of laboratory-scale uranium dioxide nuclear fuel samples in direct contact with Zircaloy-4 cladding. The goal was to characterize the melted and refrozen interfaces, in particular, observing local changes of the melting point and interdiffusion of fuel and cladding materials under inert gas (Ar), in the presence of hydrogen (Ar + 6% H2) or in air. Results obtained by laser heating UO2 pellets clad in a Zircaloy ring were interpreted in light of reference tests performed on pellets in which UO2 and zirconium were blended in a series of given compositions. The sample composition was analyzed by scanning electron microscopy to verify the occurrence of diffusion and segregation phenomena during the laser-heating cycles. Laser-melting experiments were performed on pellets of uranium dioxide clad in Zircaloy-4 rings to simulate the configuration of a light water reactor fuel rod. Under inert gas, the material interdiffusion resulted in consistent melting point depression (of up to 200 K below the melting point of pure UO2) at the interface between the fuel and the cladding. Experiments carried out in the presence of H2 displayed a more limited effect on the melting temperature, but they resulted in a remarkable embrittlement of the whole structure, with large fragmentation of the Zircaloy cladding. This was probably due to the formation of brittle and highly volatile Zr hydrides. The observed melting point decrease was even more pronounced (up to over 400 K) under air in uranium-rich samples, due to the change in the stoichiometry of UO2 in UO2+x. [ABSTRACT FROM AUTHOR]

The influence of laser short-pulse heating is utilized to investigate an elastic-mechanical-thermodiffusion (EMTD) model. The model is studied when the holes/electrons interaction of semiconductor medium is occurred with a fractional derivative of the heat equation. The governing equations describing this model are very complex, so they are studied in one dimension (1D) when the considered physical quantities are in a non-dimensional. In this case, the thermoelastic deformation (TD) due to the electronic deformation (ED) with some initial conditions is considered. Laplace transforms are used to analyze the governing equations mathematically when the thermal conductivity is variable. To obtain the complete solutions, the inverse Laplace transforms are used numerically based on the Fourier series with the application of some boundary conditions. Several comparisons of the wave propagation distribution of the fundamental fields are presented graphically according to different values of the fractional parameter, memories parameters, and thermal conductivity with discussion. [ABSTRACT FROM AUTHOR]

VIPA-based Brillouin spectroscopy is implemented for in-situ measurements at high pressure and temperature in laser-heated diamond anvil cells. Its performances are compared to those of the widely used Tandem Fabry–Perot instrument. A significant reduction of the collection time is in particular enabled. The usefulness of VIPA-Brillouin spectroscopy for High Pressure studies is here illustrated by revisiting the nitrogen melting curve up to 45 GPa. VIPA-Brillouin spectroscopy has the potential to become an important platform to investigate the equation of state properties of warm dense molecular systems. [ABSTRACT FROM AUTHOR]

For accurate laser-induced incandescence (LII) measurements of soot properties it is of great importance to understand the nature of the physical processes involved during rapid laser heating. In this work, we investigate how well-characterized differently matured fresh soot from a soot generator responds to rapid laser heating. For this purpose, a double-pulse LII setup is used with 10 μs time separation between the pulses using various combinations of two common LII wavelengths (532 and 1064 nm). Detection is performed at two wavelength bands for fluorescence analysis, and additionally elastic light scattering is used for mass loss analysis during heating. We investigate how the LII signal changes with pre-heating laser energy, specifically by fluence curve analysis to estimate the influence of thermal annealing, sublimation and laser-induced fluorescence interference. It is shown that extensive absorption enhancement occurs for all types of soot as the soot is thermally annealed, which is manifested through decreasing dispersion coefficient ξ and an increasing absorption coefficient E(m,λ). When comparing young and mature soot, a much larger impact of sublimation can be observed in the fluence curves of the mature soot. Also, we observe an enhanced contribution of laser-induced fluorescence for the young soot when performing LII measurements using 532 nm, which is suggested to originate from vaporized carbon fragments with an aromatic structure. This work further shows the potential of utilizing double-pulse arrangements for increasing the detectability of poorly absorbing soot, but also it highlights the impact of laser heating on soot, which may be important to avoid interferences when performing soot diagnostics. [ABSTRACT FROM AUTHOR]

In the present work, a fully coupled thermo-mechanical analysis is presented to obtain the desired bend angle in the sheet made of AM30 magnesium alloy. The finite element method (FEM) based software ABAQUS 6.10 is employed to estimate the temperature, stress and strain distribution with time for different laser bending process parameters. An FEM proposed model is validated with the experimental results. Some parametric study has been performed to see the influence of laser process parameters on AM30 alloy. Single and multi-passes laser line heating is employed, and observed that the bend angle achieved in multi-passes is approximately 430% higher than the single pass. Hence, the results presented in this paper can be used to assess the applicability of AM30 magnesium alloy in laser-based forming industries. [ABSTRACT FROM AUTHOR]

Transparent polymer sheets (PET, PEN, PI) were treated in a vacuum condition by a laser-diode (wavelength: 408 nm). The polymers were decomposed thermally with an endothermic reaction by the laser heating, and carbonization, due to the evolution of gaseous products including CO and CO2, occurred on the surface. The heating mechanism of the polymers was summarized as the formation of carbonized layer on polymer sheets and the thermal conduction due to the heating of carbonized layer by the laser-diode. Thus, it is concluded that the choice of an appropriate wavelength for the laser-diode can facilitate modification processes for various transparent polymers. [ABSTRACT FROM AUTHOR]

We describe the use of a silver-coated 90 ∘ parabolic mirror of 33 mm focal length as objective for imaging, on-axis laser heating and radiospectrometric temperature measurements of a sample compressed in a diamond anvil cell in a laser heating system. There, spatial resolution and imaging quality of the parabolic mirror are similar to the one of a 10× objective. The temperature measurements between 500 and 900 nm are essentially free from chromatic aberration. The parabolic mirror was also perforated with a 220-μm hole, allowing for on-axis imaging, laser heating and incidence of X-rays simultaneously at synchrotron facilities. The parabolic mirror is thus a well-suited alternative to existing refractive and reflective objectives in laboratory and synchrotron laser heating systems. [ABSTRACT FROM AUTHOR]

The emission line intensities enhancement in laser-induced breakdown spectroscopy is a subject of significant interest for the last several years and different techniques have been opted to achieve this objective. In this contribution, we present a systematic study on the signal enhancement in the laser-produced Cu-Zn alloy plasma using two experimental settings: by increasing the laser energy from 22 mJ to 137 mJ and keeping the target at room temperature and secondly by keeping the laser energy fixed at 22 mJ and heating the target from 298 K to 673 K. The line intensities of Cu I and Zn I showed an increasing trend in both the approaches. The plasma temperatures remain nearly constant whereas the electron number densities show an increasing trend by increasing the sample temperature at fixed laser energy and by increasing the laser energy at a constant temperature. A matching signal enhancement has been observed at a constant surface temperature of 298 K and 50 mJ laser energy and a constant laser energy 22 mJ and 600 K. The scanning electron microscopy images showed elliptical crater formation by heating the target at a fixed laser energy of 22 mJ with almost the same horizontal and vertical diameters of 825 ± 25 μm and 1000 ± 25 μm, respectively. An improvement in the signal to noise ratio has been observed by increasing the sample temperature. The results affirmed that the increase in temperature at the sample surface induces emission line intensity enhancement. [ABSTRACT FROM AUTHOR]

The behavior of self-organization of convective flows in a thin layer of liquid under point (local) heating is investigated experimentally. The interaction of thermocapillary and thermogravitational-free convection can lead both to self-organization of a cluster of micro-vortices in the form of hexagonal structures and to its partial disintegration. Correlation analysis of the velocity field shows that the characteristic convection scales change continuously over time. The largest size of the vortex flow corresponds to the layer diameter (20 mm); the integral convection scale (2.5 mm) characterizes the established interaction of vortex structures in a wide range of sizes; and the dimensions of hexagonal convective cells (80–100 µm) show the lower limit of the characteristic scale of vortex structures. The observed flow macrostructure is determined by the complex nonlinear interaction of vortices of the specified scales. The resulting value of the average integral convection scale can be effectively used to predict the convection velocity. [ABSTRACT FROM AUTHOR]

Selective laser Melting (SLM), a powder bed-based additive manufacturing technology, has been developed and applied in multiple industrial fields in the last decade. However, the distortion and swelling in the SLM process resulting from thermal stress cannot be predicted subject to measurement. In this work, an in situ distortion measurement system applied to the SLM process is presented. The distortion behaviour of component under laser scanning can be precisely recorded in real-time by this system. The detailed evolution and driving force of specimen distortion in the SLM process are discussed based on the experimental results. The distortion in single laser scanning presents a strong instantaneous upward motion of the central section during laser heating and a relatively slow downward recovery motion of the central section during cooling. The distortion behaviour of the sample with and without a layer of metal powder are compared, and laser scanning on the bare sample surface leads to a significantly higher residual distortion. The influence of SLM parameter variables (such as scanning speed, laser power, scanning width, layer thickness and scanning times) on SLM distortion is also analysed. At last, the stress distribution of laser melting is verified by the high-resolution EBSD analysis. [ABSTRACT FROM AUTHOR]

The influence of the thermophysical parameters nonlinearities and phase transitions of melting and evaporation on thermal processes at laser heating of metals by the example of iron is investigated in the article. [ABSTRACT FROM AUTHOR]

In this article, we determine the impact of laser parameters on the development of a flexible conductive transparent film in multi wall carbon nanotubes (MWCNTs) regular structures fabricated on the PET substrate. Both MWCNT and PET are the attractive material for flexible electronics and technological interest in Micro/Nano-manufacturing. Now day, femtosecond laser irradiation nanojoining with selected surface treatments is introduced as an interface enhancer between MWCNT and the PET. We investigated the femtosecond laser of fused PET. After laser irradiation heating, thermal effects modify the structures, and the properties of MWCNTs at the junction point. The network created by Laser irradiation requires extreme parameters: Laser energy irradiation, the effective laser radius, and preheating temperature. Theoretical calculations show us that 90 mW under laser spot radius of 1.5 mm and preheating temperature of 300 K can generate 433.0845 K as surface temperature enough to connect 1 µm in thick of MWCNTs without damage the PET substrate. [ABSTRACT FROM AUTHOR]

Laser derivatization is proposed as a diagnostic technique toward identifying the sources contributing to combustion produced soot. Fuel chemistry and the resultant oxygen content in nascent soot have been shown to influence the evolution of soot nanostructure upon laser derivatization. This is illustrated using the spectroscopic and microscopic characterization of biodiesel soot, with a systematic variation in fuel chemistry used to generate the soot. Functionalized carbon black is used as the control to independently verify the influence of material chemistry on nanostructure upon laser heat treatment. Results track with those observed for biodiesel soot. Reciprocally, the similarity in soot nanostructure observed after laser heating is tied to the likeness in fuel chemistry of biomass-fueled sources. Understanding the origin of differences or similarities in soot nanostructure upon laser heat treatment can help differentiate sources based on their contribution, thereby aiding in effective air quality control. Copyright © 2019 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

Laser heating with different power densities was applied to hard coatings to improve their adhesion to cemented carbides substrate (cutting edges). The adhesion force was determined by critical load Lc in the scratch test using an automatic scratch tester constructed at Poznan University of Technology. The determination of adhesion force (the value of critical load, measured during the scratch test) was carried out based on the analysis of the vibration spectrum. Scanning electron microscopy, 3D surface profiling and X-ray mapping were used to verify the coating state after laser heating. The results indicate that significant increase of Lc can be achieved for the laser beam power density of up to 4100 W/cm2, for monolayer (single – Ti(C,N) and double – Ti(C,N)+TiN) coatings only. Higher beam power leads to coating cracking and decohesion of the substrate. Rapid laser heating is not recommended for the alumina layer in tri-layer coating (TiC+Al2O3+ Ti(C,N)) because alumina layer has low heat impact resistance. Also new in this article is the fact that as a result of laser heating, the chemical composition of the coating changes, which affects its adhesion to the substrate. Considerable increase in adhesion after laser heating of single and double coatings to substrate made of cemented carbides should contribute to better wear resistance of coated edges during machining. [ABSTRACT FROM AUTHOR]

Raman and optical spectroscopy are versatile tools for nondestructive characterization of a wide range of properties of novel materials and minerals in situ at extreme and ambient conditions. These techniques are genuinely complementary to X-ray tools (diffraction and spectroscopy) in the probe energy, momentum transfer, and time scale, making concomitant X-ray and optical probes available for advanced sample analysis. We have built a state-of-the-art, user-friendly integrated Raman and optical spectroscopy system at Sector 13 (GeoSoilEnviroCARS, University of Chicago, IL) of the Advanced Photon Source (APS), Argonne National Laboratory (ANL), where optical probes are available now in combination with high resolution in-situ synchrotron X-ray diffraction and spectroscopy tools (XRD, IXS, XES, NFS, and others) for extensive sample investigation. The integrated optical system enables a variety of techniques including multi-colored (five laser lines: 266, 473, 532, 660, and 946 nm) confocal Raman, fluorescence, and optical spectroscopy from ultraviolet (UV) to near infrared (IR) spectral ranges (266–1600 nm), and Coherent Anti-Stokes Raman spectroscopy (CARS) in combination with near IR double sided laser heating. [ABSTRACT FROM AUTHOR]

The present work deals with vibration phenomenon of a homogeneous, isotropic thermoelastic double porous microbeam induced by laser pulse heating, in context of Lord–Shulman theory of thermoelasticity with one relaxation time. Laplace transform technique has been used to obtain the expressions for lateral deflection, axial stress, axial displacement, volume fraction field and temperature distribution. The resulting quantities are obtained in the physical domain by applying a numerical inversion technique. Variations of axial displacement, axial stress, lateral deflection, volume fraction field and temperature distribution with axial distance are depicted graphically to show the effects of porosity and laser intensity parameter. Some particular cases are also deduced. [ABSTRACT FROM AUTHOR]

We demonstrate that combining the laser heating (LH) system in a diamond anvil cell (DAC) with a tandem acousto-optical tunable filter (TAOTF) allows measurement of the temperature distribution (TD) under infrared (IR, 1064 nm) LH of a specimen under high pressure in a DAC. The main component of the system is a TAOTF synchronized with a video camera. The system allows TD mapping within a temperature range of approximately 1000-2000 K on the surface of a laser-heated object (Fe plates) at high pressure in a DAC with a spatial resolution 2 µm by fitting the actual signal to Planck's equation at each point. [ABSTRACT FROM AUTHOR]

In the selective laser sintering (SLS) method, layers of powder are scanned by a laser beam and sintered. The thermal gradients created by laser heating and the subsequent cooling of the sintered sections results in thermal stresses and part warping in the final part. Thermal gradients are dependent on the scanning algorithm, in particular, the scan vector length. In this work, an efficient scanning algorithm for the SLS process is presented with the aim to minimise the part warping in the final part due to thermally induced residual stresses, while maintaining the production time at a minimum. The proposed algorithm is implemented in a finite element simulation and scanning parameters including the number of offsets and scanning length are optimised at constant laser parameters and chamber conditions. The FE model is verified by testing a few samples on SLS machine and comparing the parts made by the proposed algorithm with those made using conventional scan algorithm is the same as parallel-line scan algorithm. It is shown that part warping in the parts made by the proposed algorithm is reduced by up to 35% while the production time, part accuracy and surface properties are improved. [ABSTRACT FROM AUTHOR]

In this article we present a direct comparison between reflective (Schwarzschild mirrors) and refractive (achromatic doublets) optics commonly used in spectroradiometric temperature measurements in laser heated diamond anvil cells. Emission spectra are fitted with the Planck's law and are further analysed with the two-colour technique; theoretical simulations are used to compare the temperature measurement accuracy of the two optical systems. The first result obtained is that achromatic doublets with large numerical aperture () produce extensive accuracy errors in the full T range (1500-3000 K). When reduced apertures () are used a good agreement is found with measurements from reflective optics up to 2600 K while systematic differences (around 200 K) appear at higher temperatures. However, these temperature differences cannot explain the discrepancies between the iron melting curves obtained in the past years using laser heated diamond anvil cells. [ABSTRACT FROM AUTHOR]

We have developed an internal-resistive heated diamond-anvil cell (IHDAC) with a new resistance heater - boron-doped diamond (BDD) - along with an optimized design of the cell assembly, including a composite gasket. Our proposed technique is capable of heating a silicate/oxide material with (1) long-term stability (>1 h at 2500 K) and (2) uniform radial temperature distribution (±35 K at 2500 K across a 40-µm area), which are clear advantages over the conventional laser-heated and internal-heated DACs. In addition, the achieved temperature in this study was greater than 3500 K, which mostly covers the possible geotherm of the entire lower mantle. In situ X-ray diffraction (XRD) measurement and ex situ chemical analyses confirmed that weak XRD intensity from the BDD heater and chemical inertness (no boron diffusion into silicate samples). This newly developed IHDAC with a BDD heater can be used to determine the phase diagrams of mantle materials with high precision and be used in lower-mantle petrology. [ABSTRACT FROM AUTHOR]

This study analyzed the dynamic characteristics of temperature and stress fields during induction and laser heating of a semi-infinite body. The semi-infinite body was subjected to a distribution heat flux (induction heating) at a particular depth range and then to a surface heat flux (laser heating). Using the Green function method and the Laplace transform, the temperature and stress fields solutions were acquired for both heating methods. The analytical results of the temperature and stress fields are shown graphically in the time domain for a selected position. It was found that under the same input power conditions, the temperature field acquired is identical in both induction and laser heating in the range of more than one skin depth. The peak dynamic thermal stress from both heating methods increases rapidly along the depth, and converges to a fixed value. Meanwhile, the peak thermal shock stress is relatively small, and quickly decays at a certain position in a very short duration. Therefore, the thermal shock dynamic characteristics are negligible in the two highly variant transient heating methods--induction and laser. [ABSTRACT FROM AUTHOR]

A three-dimensional numerical simulation is conducted for complex flow and heat transfer that incorporate solid–liquid–vapor phase change and surface chemical reaction induced by localized laser heating on a urethane-coated stainless-steel substrate. The surface chemical reaction due to laser irradiation on the urethane-coated stainless-steel substrate, and heat and mass transfer due to melting/vaporization of the stainless steel are considered. The entire problem is solved within one computational domain that includes two solid regions and one gaseous region through a penalty method. One of the solid region is the paint that will decompose via chemical reaction to generate gaseous products and then mix with the air, and the other one is the stainless steel that melting and vaporization can occur due to extremely high temperature in the process. Moreover, the gas phase is considered as a multicomponent system that consists of O2, N2, CO2, H2O, NO2, binder vapor, and stainless-steel vapor. In the present multiphysics simulation, the process of melting, vaporization and chemical reaction and the splash of the melted paint and stainless steel into the gas is observed. [ABSTRACT FROM PUBLISHER]

In laser bending process, metal sheets are deformed by using thermal stresses induced due to controlled laser heating. Straight line heating is used to manu-facture simple shapes while curvilinear irradiation is used to generate 3D complex shapes. Scanning path curvature is an important parameter that controls the deformation profile of a worksheet. This article presents systematic investigations into influence of scanning path curvature on the thermal stresses based deformation behavior, temperature distribution and warping of the magnesium M1A sheets. Initially, a three-dimensional nonlinear ther-momechanical finite element model of curvilinear laser bending process has been developed. Mathematical correlations have been derived to model the curvilinear irradiations. The developed model has been validated by using experimental studies. Then, numerical investigations have been performed on temperature distribution, stress-strain distribution and distortions occur in the laser bent magnesium alloy sheets. Results indicated that sheet bends away from the scanning path. One of the key findings is that low to medium levels of arc height reduce the edge effect during laser bending, while higher values of arc height produce warping at the free edge. It is envisaged that presented results will be useful to manufacture 3D complex shapes and to align complex geometry sheets. [ABSTRACT FROM AUTHOR]

The effect of heating rate on the combustion pathways of fully dense, micron-sized, nanocomposite thermite particles is examined. Stoichiometric nanocomposite thermites utilizing aluminum or zirconium as fuels were prepared by arrested reactive milling with several oxidizers (WoO3, MoO3, CuO, Fe2O3, and Bi2O3). The powders were ignited using both electrostatic discharge (ESD) and CO2 laser beam. The particles ignited directly by ESD were heated at ca. 109 K/s while the particles ignited by laser were heated at ca. 106 K/s. Additional reference laser ignition experiments were performed with particles of pure Al and Zr. Optical emission of burning particles was recorded. For both Al- and Zr-based thermites, burn times of particles ignited by the laser were slightly longer than for similarly sized particles of pure Al and Zr, respectively. This suggests that both Al- and Zr-based thermite particles heated by laser lose their nanostructure immediately upon their ignition. Burn times and temperatures were compared for the particles of the same materials ignited using different heating rates. For Zr-based thermites, ESD generated burning particle clouds, with many particles ignited with a substantial delay and heated much slower than those ignited by ESD directly. Thus, direct comparisons were possible only for the Al-based thermites, for which both laser and ESD ignition yielded individual burning particles. It is observed that the ESD-ignited Al-based thermite particles burn much faster than the same particles ignited by the laser. The difference in the burning regime of particles heated at different rates is interpreted observing that the rate of reaction in a particle heated up to the Al melting point is substantially higher in the ESD-heated particle compared to the same particle heated by the laser. After Al melts, the nanostructure of the composite particles may be lost; when this occurs the extent of thermite reaction in the ESD-heated particle is much greater than that in the particle heated by the laser. [ABSTRACT FROM AUTHOR]

Here, we present new Diamond Anvils with a Round Table (DART-anvils) designed for applications in the diamond anvil cell (DAC) technique. The main features of the new DART-anvil design are a spherical shape of both the crown and the table of a diamond and the position of the centre of the culet exactly in the centre of the sphere. The performance of DART-anvils was tested in a number of high pressure high-temperature experiments at different synchrotron beamlines. These experiments demonstrated a number of advantages, which are unavailable with any of the hitherto known anvil designs. Use of DART-anvils enables to realisein situsingle-crystal X-ray diffraction experiments with laser heating using stationary laser-heating setups; eliminating flat-plate design of conventional anvils, DART-anvils make the cell alignment easier; working as solid immersion lenses, they provide additional magnification of the sample in a DAC and improve the image resolution. [ABSTRACT FROM PUBLISHER]

A review of some important technical challenges related toin situdiamond anvil cell laser heating experimentation at synchrotron X-ray sources is presented. The problem of potential chemical reactions between the sample and the pressure medium or the carbon from the diamond anvils is illustrated in the case of elemental tantalum. Preliminary results of a comparison between reflective and refractive optics for high temperature measurements in the laser-heated diamond anvil cell are briefly discussed. Finally, the importance of the size and relative alignment of X-ray and laser beams for quantitative X-ray measurements is presented. [ABSTRACT FROM PUBLISHER]

Two binary phases in the system Hf–O have been synthesized at pressures between 12 and 34 GPa and at temperatures up to 3000 K by reacting Hf with HfOusing a laser-heated diamond anvil cell.In situX-ray diffraction in conjunction with density functional theory calculations has been employed to characterize a previously unreported tetragonal HfOphase. This phase has a structure which is based on an fcc Hf packing with oxygen atoms occupying octahedral interstitial positions. Its predicted bulk modulus is 223(1) GPa. The second phase has a composition close to HfO, where oxygen atoms occupy octahedral interstitial sites in an hcp Hf packing. Its experimentally determined bulk modulus is 128(30) GPa. The phase diagram of Hf metal was further constrained at high pressures and temperatures, where we show that α-Hf transforms to β-Hf around 2160(150) K and 18.2 GPa and β-Hf remains stable up to at least 2800 K at this pressure. [ABSTRACT FROM PUBLISHER]

In this paper, laser-induced hyperthermia therapy of cancer is treated as a state estimation problem and solved with a particle filter method, namely the Auxiliary Sampling Importance Resampling algorithm. In state estimation problems, the available measured data are used together with prior knowledge about the physical phenomena, in order to sequentially produce estimates of the desired dynamic variables. Although the hyperthermia treatment of cancer has been addressed in the literature by different computational methods, these usually involved deterministic analyses. On the other hand, state space representation of the problem in a Bayesian framework allows for the analyses of uncertainties present in the mathematical formulation of the problem, as well as in the measured data of observable variables that might be eventually available. Two physical problems are considered in this paper, involving the irradiation with a laser in the near infrared range of a non-homogeneous cylindrical medium representing either a soft-tissue phantom or a skin model, both containing a tumour. The region representing the tumour is assumed to be loaded with nanoparticles in order to enhance the hyperthermia effects and to limit such effects to the tumour. The light propagation problem is coupled with the bioheat transfer equation in the present study. Simulated transient temperature measurements are used in the inverse analysis. [ABSTRACT FROM AUTHOR]

Absorptivity measurements with a laser-heating approach, referred to as the laser-driven thermal reactor (LDTR), were carried out in the infrared and applied at ambient (laboratory) nonreacting conditions to particle-laden filters from a three-wavelength (visible) particle/soot absorption photometer (PSAP). The particles were obtained during the Biomass Burning Observation Project (BBOP) field campaign. The focus of this study was to determine the particle absorption coefficient from field-campaign filter samples using the LDTR approach, and compare results with other commercially available instrumentation (in this case with the PSAP, which has been compared with numerous other optical techniques). Advantages of the LDTR approach include (1) direct estimation of material absorption from temperature measurements (as opposed to resolving the difference between the measured reflection/scattering and transmission), (2) information on the filter optical properties, and (3) identification of the filter material effects on particle absorption (e.g., leading to particle absorption enhancement or shadowing). For measurements carried out under ambient conditions, the particle absorptivity is obtained with a thermocouple placed flush with the filter back surface and the laser probe beam impinging normal to the filter particle-laden surface. Thus, in principle one can employ a simple experimental arrangement to measure simultaneously both the transmissivity and absorptivity (at different discrete wavelengths) and ascertain the particle absorption coefficient. For this investigation, LDTR measurements were carried out with PSAP filters (pairs with both blank and exposed filters) from eight different days during the campaign, having relatively light but different particle loadings. The observed particles coating the filters were found to be carbonaceous (having broadband absorption characteristics). The LDTR absorption coefficient compared well with results from the PSAP. The analysis was also expanded to account for the filter fiber scattering on particle absorption in assessing particle absorption enhancement and shadowing effects. The results indicated that absorption enhancement effects were significant, and diminished with increased filter particle loading. [ABSTRACT FROM PUBLISHER]

Methods of increasing the service properties of steel components by producing hardened modified layers on the surface using laser heating are described. It is proposed to use a combined technology based on laser alloying the steel surface with nitride-forming elements and nitriding. It is shown that laser alloying in the continuous mode results in the formation of a layer with a uniform fine-grained structure with a thickness of 600 μm in the surface layer. Subsequent nitriding eliminates the unfavourable residual stresses and increases the microhardness of low-carbon steels to 20,000 MPa, cracking resistance 1.5–1.8 times and wear resistance 1.5–3 times. [ABSTRACT FROM PUBLISHER]

Selective laser melting gained substantial momentum in the recent past and quite a few alloy systems have been researched and made available for commercial use; titanium, aluminum, stainless and tool steels, cobalt chrome, and Inconel being the most popular examples. Despite the application potential, and the successful processing of powder forms by traditional powder metallurgy methods, selective laser melting of duplex stainless steels was not attempted so far. The response of a duplex stainless steel alloy to processing by selective laser melting with varying process conditions is evaluated in the current research. Experimental results ascertained that the complete cycle starting from duplex powders, consolidating into 3D forms by selective laser melting and then post-process heat treatment to bring the microstructures back to duplex forms is feasible. Within the current experimental domain, the multi-layer samples are close to 90% density and showed a maximum dimensional variation of 2–3%, while the austenite to ferrite ratio is 45:55 after the post-process heat treatment. [ABSTRACT FROM PUBLISHER]

In this paper we present recent achievements in the field of investigation of the local, electronic and magnetic structure of the matter under extreme conditions of pressure and temperature. These results were obtained thanks to the coupling of a compact laser heating system to the energy-dispersive XAS technique available on the ID24 beamline at the ESRF synchrotron. The examples chosen concern the melting and the liquid structure of 3d metals and alloys under high pressures (HPs) and the observation of temperature-induced spin crossover in FeCO3at HP. [ABSTRACT FROM PUBLISHER]

X-ray Raman scattering spectroscopy is an emerging method in the study of low and intermediateZelements' core-electron excitations at extreme conditions in order to reveal information on local structure and electronic state of matterin situ. We discuss the capabilities of this method to address questions in Earth materials' science and demonstrate its sensitivity to detect changes in the oxidation state, electronic structure, coordination, and spin state. Examples are presented for the study of the oxygen K-, silicon L- and iron M-edges. We assess the application of both temperature and pressure in such investigations exploiting diamond anvil cells in combination with resistive or laser heating which is required to achieve realistic conditions of the Earth's crust, mantle, and core. [ABSTRACT FROM PUBLISHER]

The article discusses the study which explores the glass-forming oxide's structure using aerodynamic levitation with laser heating and to investigate density-driven network collapse's mechanisms for glassy materials in the gigapascal (GPa) pressure regime by a Paris-Edinburgh press. It measures the diffraction patterns of silica glass which were subracted to reduce overlapping pair-correlation functions. The study highlights information on materials' structure that undergo extreme conditions.

We determine two-dimensional temperature and thermal stresses distributions in a semiconductor coating-substrate assembly caused by the heat source at the contact surface. The analysis is based on the Laplace and Hankel integral transforms of equations of thermal elasticity, and the obtained analytical solutions can be used without any limitations on the duration of heating, the thickness of a coating, mechanical and thermal characteristics of materials. We consider the effect of the thickness of a coating, thermal mismatch between the substrate and the coating on the magnitude of thermal stresses. Using the obtained thermal stress distribution we analyze the delamination failure at the substrate-coating interface. [ABSTRACT FROM AUTHOR]

The present study concerns the effect of the thickness of the overcoating layer on the local temperature increase in the multilayered structure subject to laser heating. The numerical simulation indicates that the presence of the diamond-like carbon (DLC) layer on the top of multilayered structure enhances local temperature increase, compared with the same structure without the DLC layer. This enhancement gradually becomes significant with an increase in the thickness of DLC layer. The DLC layer only absorbs small amount of laser energy. However, the energy accumulates in the DLC layer due to its low thermal conductivity, resulting in significant temperature increase. [ABSTRACT FROM AUTHOR]

Ge–Sn compound is predicted to be a direct band gap semiconductor with a tunable band gap. However, the bulk synthesis of this material by conventional methods at ambient pressure is unsuccessful due to the poor solubility of Sn in Ge. We report the successful synthesis of Ge–Sn in a laser-heated diamond anvil cell (LHDAC) at ~7.6 GPa & ~2000 K.In situRaman spectroscopy of the sample showed, apart from the characteristic Raman modes of Ge TO (Г) and β-Sn TO (Г), two additional Raman modes at ~225 cm−1(named Ge–Sn1) and ~133 cm−1(named Ge–Sn2). When the sample was quenched, the Ge–Sn1mode remained stable at ~215 cm−1, whereas the Ge–Sn2mode had diminished in intensity. Comparing the Ge–Sn Raman mode at ~225 cm−1with the one observed in thin film studies, we interpret that the observed phonon mode may be formed due to Sn-rich Ge–Sn system. The additional Raman mode seen at ~133 cm−1suggested the formation of low symmetry phase under high P–T conditions. The results are compared with Ge–Si binary system. [ABSTRACT FROM AUTHOR]

Solventless melt electrospinning which allows mass production is substantially safe. It can produce fibres of hundreds of nanometres, one order of magnitude lower than that of conventional melt-blown spinning. In this paper, a comparison between different technologies producing ultra-fine fibre reveals the advancement of melt electrospinning method using umbellate spinneret for ultra-fine fibre mass production. Some typical industrial polymer materials was also spun using melt electrospinng method, including biodegradable materials like polylactic acid and polycaprolactone (PCL), which may contribute to some interesting applications. In addition, a machine for mass production is also proposed. Finally, proposition of the industrialisation of ultra-fine fibre by melt electrospinning is discussed. [ABSTRACT FROM AUTHOR]

Focused laser irradiation can easily drive materials to extreme temperatures with very high precision and control. In combination with infrared imaging and material characterization techniques, the resulting thermal load can be assessed to derive meaningful thermophysical properties avoiding interferences that would normally occur with direct contact measurements of temperature. In this focused article we first address technical challenges with the experimen-tal implementation involved in obtaining laser-induced temperature field data from infrared imaging. We then discuss suitable heat transport models for analysis of thermal data and, fi-nally, describe specific examples of thermophysical material parameters derived from combined infrared imaging and laser heating. The aim is to illustrate general principles of this combined laser-based heating and IR thermal imaging approach that are useful for experimentation under extreme conditions, which often remain out of reach of conventional methods [ABSTRACT FROM AUTHOR]

Chemical vapor deposition of TiN on a spherical particle surface subjected to nanosecond laser heating is simulated numerically here. A thermal model is developed to describe the heat transfer within the particle, chemical reaction on the particle surface, and mass transfer in the gases. The heat conduction and mass diffusion equations are discretized using the finite volume method with fully implicit schemes, and solved with tridiagonal matrix method. Temporal distributions of particle surface temperature and deposited film thickness resulting from multiple-pulse irradiation are analyzed for a wide range of parameters including laser fluence, pulse repetition frequency, pulse width, initial particle temperature, particle radius, and total pressure in the reaction chamber. [ABSTRACT FROM PUBLISHER]

In our previous study, we proposed a new surface modification technique by combination of ceramic coating and laser heat treatment. By applying laser heat treatment after coating, it was possible to improve the adhesive strength and substrate hardness of ceramic coated steels without compromising the film hardness. In the present research, in order to quench a larger area of ceramic coated steel uniformly and efficiently, a high power diode laser equipped with a galvano-scanner was used in the laser heat treatment process. The scanning laser irradiation conditions to achieve uniformly quenched substrates without any surface damage were investigated for three kinds of ceramic coated steels: CrAlN, TiAlN and CrN. The film hardness and adhesive strength of the laser irradiated regions were evaluated. It is shown that scanning laser quenching after coating effectively improved the mechanical properties for larger area of ceramic coated steels. [ABSTRACT FROM AUTHOR]

Laser repetitive pulse heating of tungsten carbide coating formed at a steel sheet surface is examined. Temperature field and melt pool formed in the coating and steel sheet are simulated for different coating thicknesses. The influence of laser power intensity distribution on the melt pool formation is incorporated in the analysis through introducing the laser pulse parameter. The control volume method is used to predict temperature field while the enthalpy–porosity method is incorporated to account for the phase change during the heating process. It is found that temperature predictions at the coating surface agree with the thermocouple data. The melt pool width formed in the coating is smaller than that corresponding to the steel sheet. Increasing coating thickness reduces the peak temperature at the surface. The Marangoni flow results in a toroid shape of rotating cells in the melt pool of the coating. [ABSTRACT FROM AUTHOR]

The latest developments in single-crystal X-ray diffraction at high pressure and high temperature are described. Advances in diamond anvil cell designs and X-ray sources allow collecting single-crystal diffraction data at pressures up and above 100 GPa and at temperatures above 1000°C. The technical details of single-crystal X-ray diffraction at high pressure such as the choice of pressure-transmitting media or the different methods for measuring pressures and temperatures have been reviewed. Examples of structural solution of complex structures and new materials, structural refinements of high pressure polymorphs as well as accurate compressibility data are described in order to outline the several advantages of using single crystals instead of powdered samples in high pressure diffraction experiments. [ABSTRACT FROM PUBLISHER]

A novel high pressure polymorph of iron sesquioxide,m-Fe2O3, has been identified by means of single-crystal synchrotron X-ray diffraction (XRD). Upon compression of a single crystal of hematite, α-Fe2O3, in a diamond anvil cell, the transition occurs at pressure of about 54 GPa and results in ∼10% volume reduction. The crystal structure of the new phase was solved by the direct method (monoclinic space groupP21/n, a=4.588(3),b=4.945(2),c=6.679(7) Å and β=91.31(9)°) and refined toR1∼11%. It belongs to the cryolite double-perovskite structure type and consists of corner-linked FeO6octahedra and FeO6trigonal prisms filling the free space between the octahedra. Upon compression up to ∼71 GPa at ambient temperature no further phase transitions were observed. Laser heating to ∼ 2100±100 K promotes a transition to theCmcmCaIrO3-type (post-perovskite (PPv)) phase. The PPv-Fe2O3crystal structure was refined by means of single-crystal XRD at ∼65 GPa. On decompression the PPv-Fe2O3phase fully transforms back to hematite at pressures between ∼25 and 15 GPa. [ABSTRACT FROM PUBLISHER]