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A statistical learning method for image-based monitoring of the plume signature in laser powder bed fusion
摘要： The industrial breakthrough of metal additive manufacturing processes mainly involves highly regulated sectors, e.g., aerospace and healthcare, where both part and process qualification are of paramount importance. Because of this, there is an increasing interest for in-situ monitoring tools able to detect process defects and unstable states since their onset stage during the process itself. In-situ measured quantities can be regarded as “signatures” of the process behaviour and proxies of the final part quality. This study relies on the idea that the by-products of laser powder bed fusion (LPBF) can be used as process signatures to design and implement statistical monitoring methods. In particular, this paper proposes a methodology to monitor the LPBF process via in-situ infrared (IR) video imaging of the plume formed by material evaporation and heating of the surrounding gas. The aspect of the plume naturally changes from one frame to another following the natural dynamics of the process: this yields a multimodal pattern of the plume descriptors that limits the effectiveness of traditional statistical monitoring techniques. To cope with this, a nonparametric control charting scheme is proposed, called K-chart, which allows adapting the alarm threshold to the dynamically varying patterns of the monitored data. A real case study in LPBF of zinc powder is presented to demonstrate the capability of detecting the onset of unstable conditions in the presence of a material that, despite being particularly interesting for biomedical applications, imposes quality challenges in LPBF because of its low melting and boiling points. A comparison analysis is presented to highlight the benefits provided by the proposed approach against competitor methods.
关键词： Process plume,Metal additive manufacturing,Laser powder bed fusion,Infrared imaging,In-situ monitoring,Zinc
更新于2025-11-28 14:24:20
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In-situ Measurements and Thermo-mechanical Simulation of Ti-6Al-4V Laser Solid Forming Processes
摘要： Residual stresses and distortions are two technical obstacles for popularizing the Additive Manufacturing (AM) technology. The evolution of the stresses in AM components during the thermal cycles of the metal depositing process is not yet clear, and more accurate in-situ measurements are necessary to calibrate and validate the numerical tools developed for its simulation. In this work a fully coupled thermo-mechanical analysis to simulate the Laser Solid Forming (LSF) process is carried out. At the same time, an exhaustive experimental campaign is launched to measure the temperature evolution at different locations, as well as the distortions and both the stress and strain fields. The thermal and mechanical responses of single-wall coupons under different process parameters are recorded and compared with the numerical models. Good agreement between the numerical results and the experimental measurements is obtained. Sensitivity analysis demonstrates that the AM process is significantly affected by the laser power and the feeding rate, while poorly influenced by the scanning speed.
关键词： Numerical simulation,Laser Solid Forming (LSF),Thermo-mechanical analysis,Additive manufacturing (AM),In-situ measurements of residual stresses
更新于2025-11-28 14:24:20
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High Temperature Oxidation and Wear Resistance of In Situ Synthesized (Ti3Al?+?TiB)/Ti Composites by Laser Cladding
摘要： (Ti3Al + TiB)/Ti composites were prepared on Ti6Al4V by laser cladding. The microstructures of the coatings were analyzed; the high temperature wear and oxidation properties of the coatings were investigated and compared with Ti6Al4V. Ti3Al and TiB particles were in situ formed through the reaction between Ti and AlB2. The reinforcements exhibited some crystallographic orientation relationships with a-Ti matrix, and a semi-coherent interface (Ti3Al) or a coherent interface (TiB) was obtained. The weight gain of the coating under each combination of temperature and time condition was 20 to 30 pct of the value of Ti6Al4V under the same experimental parameters. A denser and well-bonded TiO2 + Al2O3 layer was formed, effectively hindering the oxygen diffusion compared with the TiO2 layer on Ti6Al4V. EBSD result showed that the Al2O3 mainly assembled into clusters and located close to the interface while the outer area of the oxidation layer was mainly TiO2. The friction coefficients and wear losses of the coatings were lower than those of the substrates at 300 °C to 750 °C. The oxidation was a crucial factor affecting the wear performance at high temperatures. The protective effect of the TiO2 + Al2O3 layer and the formation of transfer films on the worn surface contributed to the improved wear resistance of the coating.
关键词： TiB,Laser Cladding,Wear Resistance,Ti Composites,In Situ Synthesized,High Temperature Oxidation,Ti3Al
更新于2025-11-28 14:24:20
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A Comparative Study of Deformation Behaviors Between Laser-Welded Joints and Base Metal of Ti-22Al-24.5Nb-0.5Mo Alloy
摘要： The tensile deformation behaviors of laser-welded Ti-22Al-24.5Nb-0.5Mo alloy joints have been investigated at room temperature and 650 °C using in situ tensile analysis methods. The a2 phase had a significant influence on deformation behaviors of base metal at room temperature and 650 °C. The microcracks mainly nucleated in B2/a2 phase boundaries or within a2 phase and then propagated along B2/a2 phase boundaries subsequently. Compared with the plastic fracture of base metal, the fracture modes of the fully B2-phase fusion zone at room temperature and 650 °C were quasi-cleavage and intergranular fracture, respectively. While dislocation slips became foremost deformation mode in the fusion zone at room temperature, there were a great amount of slip bands on the surface of grains caused by the slip systems. The microcracks of fusion zone at 650 °C nucleated and propagated along the grain boundaries of B2 phase. Owing to the lack of grain deformation, the cross-slip bands were in small quantities on the surface of B2 phase grains.
关键词： in situ analysis,laser welding,deformation behaviors,Ti2AlNb alloy
更新于2025-11-28 14:24:20
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Mapping Neurotransmitter Identity in the Whole-Mount <i>Drosophila</i> Brain Using Multiplex High-Throughput Fluorescence <i>in Situ</i> Hybridization
摘要： Identifying the neurotransmitters used by specific neurons is a critical step in understanding the function of neural circuits. However, methods for the consistent and efficient detection of neurotransmitter markers remain limited. Fluorescence in situ hybridization (FISH) enables direct labeling of type-specific mRNA in neurons. Recent advances in FISH allow this technique to be carried out in intact tissue samples such as whole-mount Drosophila melanogaster brains. Here, we present a FISH platform for high-throughput detection of eight common neurotransmitter phenotypes in Drosophila brains. We greatly increase FISH throughput by processing samples mounted on coverslips and optimizing fluorophore choice for each probe to facilitate multiplexing. As application examples, we demonstrate cases of neurotransmitter co-expression, reveal neurotransmitter phenotypes of specific cell types and explore the onset of neurotransmitter expression in the developing optic lobe. Beyond neurotransmitter markers, our protocols can in principle be used for large scale FISH detection of any mRNA in whole-mount fly brains.
关键词： Neurotransmitter,mRNA,Fluorescence in situ hybridization,Gene expression,Drosophila
更新于2025-11-21 11:08:12
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Thiourea-assisted coating of dispersed copper electrocatalysts on Si photocathodes for solar hydrogen production
摘要： Photoelectrochemical water splitting can convert solar energy into clean hydrogen energy for storage. It is desirable to explore non-precious electrocatalysts for practical applications of a photoelectrode in a large scale. Here, we developed a facile spin-coating and in-situ photoelectrochemical reduction method to prepare a dispersed Cu electrocatalyst on a Si photocathode, which improves the performance remarkably. We find that thiourea in the precursor solution for spin-coating plays an important role in obtaining dispersed Cu particles on the surface of a Si photoelectrode. With thiourea in the precursor, the Cu/Si photocathode shows higher performance than the one without thiourea. Moreover, the Cu/Si photocathode also indicates good stability after 16 h illumination.
关键词： In-situ photoelectrochemical reduction,Cu electrocatalyst,Thiourea,Hydrogen evolution reaction
更新于2025-11-19 16:51:07
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A Wide Temperature Insensitive Piezoceramics for High-Temperature Energy Harvesting
摘要： One of the key challenges in the development of high-temperature energy harvesting (HTEH) technology is to clarify the relationship between temperature-dependent material parameters and device power generation capabilities. However, at present, the research on temperature stability of piezoceramics mainly relies on thermal annealing technology, which cannot follow the actual temperature dependence of the piezoelectricity, and it is even more difficult to predict the temperature stability of HTEH. To shed light on this field, here, (1-x)BiScO3-xPbTiO3 system was chosen for building HTEH material, and the temperature dependent electrical parameters, such as d33, εr, and g33, have been measured by multiple in-situ techniques. It was found that the synergistic effect of d33 and εr with temperature helps to obtain a stable g33 value in a wide temperature range. Moreover, in the mode of the cantilever-type energy harvester, a stable output voltage was obtained at x=0.64 harvester with less than 20% change over a broad temperature range of 100-250 oC, and it was verified that the temperature stability of g33 is crucial to the operation stability of HTEH devices.
关键词： in-situ techniques,piezoelectric materials/properties,energy harvesting,thermal properties
更新于2025-11-14 17:28:48
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In Situ Microwave-Assisted Fabrication of Hierarchically Arranged Metal Sulfide Counter Electrodes to Boost Stability and Efficiency of Quantum Dot-Sensitized Solar Cells
摘要： This study describes preparation of metal sulfide counter electrodes (CEs) through one-pot microwave-assisted route to improve power conversion efficiency (PCE) of quantum dot-sensitized solar cells at a lower cost. The CuS nanorods, Ni0.96S nanoparticles, and PbS nanocubes are synthesized and deposited in situ on fluorine-doped tin oxide substrate to serve as CEs without further post-treatment. Effects of several reaction parameters including sulfur precursor (Na2S, C2H5NS, CH4N2S), Cu concentration, reaction time, and choice of cation (Cu, Ni, Pb) on the CEs morphology, electrochemical characteristics, and PCE are studied. Furthermore, nanostructure formation and thin film growth are studied and correlated with PCE, from which morphology- and composition-performance relationships can be inferred. Hierarchically assembled nanorod CuS CEs exhibit higher electrochemical stability in the S2–/Sn2– redox reaction. Together with the efficient charge transfer and higher diffusion coefficient of polysulfide redox at the electrode/electrolyte interface, deduced from electrochemical impedance spectroscopy and Tafel analyses, a PCE of 8.32% is achieved for the CuS CE. The enhanced photovoltaic performance is ascribed to the 1D CuS nanorods forming a diffusive structure which decreases charge transfer impedance and facilitates regeneration of polysulfide redox leading to a higher short-circuit current density and fill factor.
关键词： In situ deposition,quantum dot-sensitized solar cells,counter electrode,CuS,microwave-assisted synthesis
更新于2025-11-14 17:04:02
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Direct Observation of Structural Evolution of Metal Chalcogenide in Electrocatalytic Water Oxidation
摘要： As one of the most remarkable oxygen evolution reaction (OER) electrocatalysts, metal chalcogenides have been intensively reported due to their high OER activities during the past few decades. It has been reported that electron-chemical conversion of metal chalcogenides into oxides/hydroxides would take place after OER. However, the transition mechanism of such unstable structures, as well as the real active sites and catalytic activity during OER for these electrocatalysts, has not been understood yet, which urgently needs a direct observation for the electrocatalytic water oxidation process, especially at nano or even angstrom scale. In this research, by employing advanced Cs-corrected transmission electron microscopy (TEM), a step by step oxidational evolution of amorphous electrocatalyst CoSx into crystallized CoOOH in OER has been in situ captured: irreversible conversion of CoSx to crystallized CoOOH is initiated on the surface of electrocatalysts with a morphology change via Co(OH)2 intermediate during OER measurement, where CoOOH is confirmed as the real active species. Besides, this transition process has also been confirmed by multiple applications of X-ray photoelectron spectroscopy (XPS), in situ Fourier-transform infrared spectroscopy (FTIR) and other ex situ technologies. Moreover, based on this discovery, a high-efficiency electrocatalyst of a nitrogen-doped graphene foam (NGF) coated by CoSx has been explored through a thorough structure transformation of CoOOH. We believe this in situ and in-depth observation of structural evolution in OER measurement can provide insights into the fundamental understanding of the mechanism for OER catalysts, thus enabling the more rational design of low-cost and high-efficient electrocatalysts for water splitting.
关键词： structural evolution,XPS,in situ TEM,water oxidation,cobalt chalcogenide
更新于2025-11-14 15:27:09
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Anomalous shape evolution of Ag2O2 nanocrystals modulated by surface adsorbates during electron beam etching
摘要： An understanding of nanocrystal shape evolution is significant for the design, synthesis and applications of nanocrystals with surface-enhanced properties such as catalysis or plasmonics. Surface adsorbates that are selectively attached to certain facets may strongly affect the atomic pathways of nanocrystal shape development. However, it is a great challenge to directly observe such dynamic processes in situ with high spatial resolution. Here, we report the anomalous shape evolution of Ag2O2 nanocrystals modulated by the surface adsorbates of Ag clusters during electron beam etching, which is revealed through in situ transmission electron microscopy (TEM). In contrast to the Ag2O2 nanocrystals without adsorbates, which display the near-equilibrium shape throughout the etching process, Ag2O2 nanocrystals with Ag surface adsorbates show distinct facet development during etching by electron beam irradiation. Three stages of shape changes are observed: a sphere-to-a cube transformation, side etching of a cuboid, and bottom etching underneath the surface adsorbates. We find that the Ag adsorbates modify the Ag2O2 nanocrystal surface configuration by selectively capping the junction between two neighboring facets. They prevent the edge atoms from being etched away and block the diffusion path of surface atoms. Our findings provide critical insights into the modulatory function of surface adsorbates on shape control of nanocrystals.
关键词： surface adsorbates,Ag2O2 nanocrystal,shape evolution,In situ TEM,electron beam etching
更新于2025-09-23 15:23:52