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Effects of tilt angle between laser nozzle and substrate on bead morphology in multi-axis laser cladding
摘要： Laser cladding has been increasingly used for repairing and remanufacturing critical and high-value components due to its unique benefits such as high solidification rates and a small heat-affected zone. In laser cladding, tilt angle between a laser nozzle and a substrate has a significant impact on deposited bead morphology. To ensure the quality of laser cladding, the effects of tilt angle on bead morphology are investigated in this study. An analytical model is introduced to predict bead shapes for three tilting postures. In the first case, a substrate remains horizontal while the nozzle is tilted. All three parameters, including width, height, and peak point offset, will be influenced by the laser beam power distribution. In the second case, a substrate is tilted while the laser nozzle is kept axial to the substrate’s normal, the peak point offset will ascend along with the increasing of the tilt angle (gravity effect). In the third case, the laser nozzle remains vertical while the substrate is tilted, which leads to variations of cladding width, cladding height, and especially peak point shifting value. These parameters will be dependent on the integrated effect of gravity and the laser beam power distribution. A set of experiments is conducted to demonstrate the effectiveness of the proposed model. This study illustrates that the variation of cladding width and height with the tilt angle can be accurately calculated by the predictive model, and that the peak point shifting value is roughly smaller than 5% of cladding width when the tilt angle is less than 30°. These findings show that trajectory planning of multi-axis laser cladding can be optimized using an acceptable range of tilt angle between the laser nozzle and substrate.
关键词： Bead morphology,Laser beam power distribution,Laser cladding,Tilting posture,Gravity effect
更新于2025-11-28 14:24:20
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A comparison of microstructure and mechanical properties of laser cladding and laser-induction hybrid cladding coatings on full-scale rail
摘要： With the rapid development of high-speed and heavy-haul trains, the surface damages of rails are becoming more and more severe, and how to promote the surface strength of the rail and prolong its service life with high efficiency are becoming extremely important. Laser cladding (LC), with small heat affected zone (HAZ) and low dilution, is a promising novel way to hardface and repair the rail. However, there are two great barriers for the traditional LC to apply on full-scale rails: one is how to prevent the coating from cracking under the rapid heating and cooling cycle; the other is how to eliminate the martensite structure in HAZ, which may threaten the safety of railway transportation due to its high hardness and low fracture toughness and usually be forbidden in almost all the Railway Standards over the world. In this paper, laser-induction hybrid cladding (LIHC) was innovatively proposed to deposit Ni-based coatings on a full-scale rail. The cracking behaviors, microstructures and mechanical properties of the coatings and HAZs by LC, LIHC with induction pre-heating (pre-LIHC) and LIHC with induction post-heating (post-LIHC) were studied systemically. The results indicate that the cracking and martensite transformation occurred in the HAZ can only be prevented by post-LIHC, where fine pearlite with smaller pearlite block size and lower interlamellar spacing formed instead. Therefore, the abrupt change of microstructure and mechanical properties in the HAZ could be avoided by post-LIHC, and the hardness, strength and toughness of the rails can be improved significantly. The post-LIHC technology shows the potentiality to hardface and repair the full-scale rail.
关键词： Martensite,Microhardness distribution,Toughness,Laser-induction hybrid cladding (LIHC),Full-scale rail,Strength
更新于2025-11-28 14:24:20
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FFT analysis of surface structures fabricated by laser interference lithography
摘要： This paper presents an FFT (fast Fourier transform) analytical method for the study of surface structures fabricated by laser interference lithography (LIL). In the work, the FFT analytical method combined with Gaussian fitting is used to determine the periods and pattern distributions of surface structures from frequency spectra. For LIL, the processing parameters of incident and azimuth angles can be obtained corresponding to the period and pattern distribution. This work facilitates the detection of micro- and nano-structures, the analysis of pattern distribution in engineering, and the processing error analysis of LIL.
关键词： surface structures,micro- and nano-structures,pattern distribution,laser interference lithography,FFT analysis
更新于2025-11-25 10:30:42
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Evaluation of various tissue-clearing techniques for the three-dimensional visualization of liposome distribution in mouse lungs at the alveolar scale
摘要： Purpose: To develop a three-dimensional visualization method for evaluating the distribution of pulmonary drug delivery systems and compare four tissue-clearing techniques (ClearT2, CUBIC, ScaleS, and SeeDB2) using intrapulmonary liposomes as drug carriers. Methods: Rhodamine B-labeled liposomes were administered intrapulmonarily to mice using a MicroSprayer, and then fluorescent-labeled tomato lectin was administered intravenously to visualize the general lung structure. Tissue-clearing treatment of the mouse lungs was performed using the standard protocols of the ClearT2, CUBIC, ScaleS, and SeeDB2 techniques. Lung clearing was clarified using laser-scanning confocal microscopy, and three-dimensional images were reconstructed. Results: Fluorescent-labeled tomato lectin was preserved using ClearT2 and SeeDB2 but not using CUBIC and ScaleS. In addition, the liposomes were stable in ClearT2 reagent, but they were mostly degraded in other reagents by surface-active agents. ClearT2 treatment enabled the three-dimensional visualization of intrapulmonary rhodamine B-labeled liposomes at the alveolar scale. Conclusions: These results suggest that the ClearT2 tissue-clearing technique was appropriate for the three-dimensional visualization of intrapulmonary liposomes at the alveolar scale. This study provides important information for selecting and optimizing suitable optical tissue-clearing techniques in lungs for evaluating the distribution of pulmonary drug delivery systems.
关键词： fluorescence preservation,Intrapulmonary distribution,inhalation,liposomes,drug delivery systems,laser-scanning confocal microscopy
更新于2025-11-21 11:08:12
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[IEEE 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - Waikoloa Village, HI (2018.6.10-2018.6.15)] 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - Correlative Microscopy Characterization of Cesium-Lead-Bromide Thin-films
摘要： Inorganic cesium lead halide compounds have gained an increasing interest in the perovskite photovoltaics research community. These compounds are mixed into state of the art organic lead halide perovskite solar cells to provide for more thermal stability, and CsPbX3 (x=I, Br, Cl) nanocubes are investigated as standalone emitter material in light emitting diodes. Eventually, reproducible, single-phase CsPbBr3 thin films could also provide us with a more stable inorganic material for perovskite solar cells. In the present work, we report on microscopic structural and optoelectronic properties of Cs-Pb-Br thin films prepared by different synthesis methods and studied using various electron-microscopy techniques.
关键词： cesium lead bromide,secondary phases,phase distribution,correlative microscopy,electron microscopy,halide Perovskites
更新于2025-11-21 10:59:37
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Three-dimensional Nanoscale Mapping of Porosity in Solution-Processed ITO Multilayer Thin Films for Patternable Transparent Electrodes
摘要： Indium tin oxide (ITO) films constitute components of many layered heterostructures used for emergent technologies beyond conventional optoelectronics. Compositional and morphological changes have a direct impact on the device’s performance. Hence control over the morphology with advanced multimodal characterization approaches are required to evaluate the devices. Herein multilayer ITO films deposited by spin coating were quantified in nanoscale detail in three dimensions by combining results from depth-sensitive neutron reflectometry (NR), non-contact topographic AFM images and cross-sectional SEM images. Films with different number of deposited layers were visually transparent even though the topmost layer was as high as 60% porous, with porosity gradually decreasing as the number of the underneath sublayers increased. Surface and interfacial roughness through the total film and individual layer thickness were obtained. NR data also furnished quantitative depth information on the films chemical composition and layer-by-layer bulk density, which has never been obtained before, providing a way to monitor and ultimately control the sheet resistivity via the pore network. When the same formulation is used for inkjet printing patterns, the larger pores disappear and the optical properties are improved to >90% transmittance at all visible wavelengths. All 5L films achieved sheet resistivities as low as 10-2 ?-cm and can therefore be used as patternable transparent electrodes for many devices including liquid crystal displays.
关键词： thin multilayer film,neutron reflectometry,depth density distribution,neutron absorption reflectometry,Indium tin oxide,porosity,structure chemical depth profile,off-specular neutron scattering,layer by layer deposition
更新于2025-11-19 16:56:35
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Triplet-State Photochemistry of Dissolved Organic Matter: Triplet-State Energy Distribution and Surface Electric Charge Conditions
摘要： Excited triplet states of chromophoric dissolved organic matter (3CDOM*) are highly reactive species in sunlit surface waters and play a critical role in reactive oxygen species (ROS) formation and pollutant attenuation. In the present study, a series of chemical probes, including sorbic acid, sorbic alcohol, sorbic amine, trimethylphenol, and furfuryl alcohol, were employed to quantitatively determine 3CDOM* and 1O2 in various organic matters. Using a high concentration of sorbic alcohol as high-energy triplet states quencher, 3CDOM* can be first distinguished as high-energy triplet states (>250 kJ mol?1) and low-energy triplet states (<250 kJ mol?1). The terrestrial-origin natural organic matter (NOM) was found to mainly consist of low-energy triplet states, while high-energy triplet states were predominant in autochthonous-origin NOM and effluent/wastewater organic matter (EfOM/WWOM). The 1O2 quantum yields and electron transfer quantum yield coefficients (f TMP) generated from low-energy triplet states remained constant in all tested organic matters. External phenolic compound showed quenching effects on triplet-state formation and tended to have a higher quenching efficiency for aromatic ketone triplet states, which are the main high-energy triplet states. In comparison with terrestrial-origin NOM, autochthonous-origin NOM and EfOM/WWOM presented lower reaction rate constants for sorbic amines and higher reaction rate constants for sorbic acid, and these differences are likely due to dissimilar surface electric charge conditions. Understanding the triplet-state photochemistry of CDOM is essential for providing useful insights into their photochemical effects in aquatic systems.
关键词： surface charge,triplet-state photochemistry,energy distribution,dissolved organic matter,reactive oxygen species,chemical probes
更新于2025-11-19 16:56:35
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Manipulating the Phase Distributions and Carrier Transfers in Hybrid Quasi-Two-Dimensional Perovskite Films
摘要： Quasi two-dimensional perovskites are promising alternatives to conventional three-dimensional perovskites because of their high stability and easy tunability. However, controlling the phase distribution according to device architecture remains a major challenge. Here, the manipulation of phase purity and vertical distribution proven by ultrafast transient absorption spectroscopy, and their effect on device characteristics are reported. By adding ethyl acetate as antisolvent, the growth direction of the perovskite film is flipped. CH3NH3Cl and dimethyl sulfoxide are used to slow the growth rate of the crystal, which gives better phase purity. The direction of carrier transfer is tuned accordingly. It is found that solar cell performance is more sensitive to phase purity relative to vertical distribution. These findings are of importance for the applications of quasi-2D perovskites in different types of devices that require to change phase purity and vertical distribution.
关键词： solar cells,carrier transfer,vertical distribution,phase purity,quasi-2D perovskite
更新于2025-11-19 16:56:35
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Improvement of Ga distribution with Sb incorporation for two-step low-temperature processing of CIGSe thin film solar cells
摘要： In this study, the application of Sb incorporation for low-temperature (≤ 450 °C) processing of Cu(In,Ga)Se2 (CIGSe) solar cells is explored. At low reaction temperature, most Ga remains at the back of the ?lm adjacent to the Mo back contact. We observed that the incorporated Sb enhanced grain size and improved device performance compared with similarly processed CIGSe ?lms made without Sb. From the energy-dispersive spectroscopy analysis and secondary ion mass spectrometry results, it was determined that elemental Ga accumulation at the back of the reacted ?lm after the two-step selenization process was signi?cantly alleviated owing to Sb incorporation. Signi?cant Sb-induced grain size enhancement was con?rmed using cross-sectional scanning electron microscopy. The electronic and optical properties of the Sb incorporated CIGSe ?lms were examined with admittance spectroscopy and ?uorescence lifetime imaging techniques.
关键词： Ga distribution,Thin ?lm solar cell,Sb incorporation,Low temperature process
更新于2025-11-14 17:28:48
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Analytical solution for the Doppler broadening function using the Kaniadakis distribution
摘要： Several works have been done for the development of models that generalize the Maxwell-Boltzmann distribution, aimed at encompassing physical phenomena that lie outside the thermal equilibrium. Amongst these, there are distributions that result from the non-extensive statistics of Tsallis and Kaniadakis. Starting from these generalized distributions, a Doppler broadening function was proposed in recent papers, using the deformed Kaniadakis distribution, which was numerical, evaluated with the use of a Gauss-Legendre quadrature. From this perspective, this paper presents an analytical solution for the generalized Doppler broadening function through obtaining a partial differential equation, considering the Kaniadakis distribution. This equation is solved analytically using the methods of Frobenius and variation of parameters, in order to obtain a generalized solution for the Doppler broadening function, containing a deformation parameter j; that measures the deviation in relation to the Maxwell-Boltzmann distribution. Finally, the results were produced considering several values for j; with the intent of making a comparison with the reference values. For the validation of the deformed Doppler broadening function’s analytical solution, a numerical solution of the partial differential equation was generated. It was possible to use this numerical solution as a benchmark for the analytical solution that was derived. It was demonstrated that the analytical solution obtained is consistent, because when j tends to zero, the solution falls in the conventional form, when the Maxwell-Boltzmann distribution is considered. Apart from this, the results were shown to be good, especially when we consider the temperature and power ranges for practical applications, as the maximum error obtained was smaller than 1%.
关键词： Frobenius method,Quasi-Maxwellian distribution,Generalized Doppler broadening function,Kaniadakis distribution
更新于2025-09-23 15:23:52