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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - In-situ Characterization of Structure Evolution of Graphene During Field Emission
摘要： The structure stability of graphene field emitter is important for the performance of field emission devices. In this work, high dose electron beam illumination and high current field emission was applied on the graphene field emitter and its structure evolution and field emission characteristics were investigated using an in-situ TEM measurement system. The relation between structure and performance of graphene emitter was demonstrated. The interaction of electron and graphene was also discussed.
关键词： in-situ TEM,structure,field emission,Graphene
更新于2025-09-23 15:21:21
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A Strategy for In-Situ Imaging of Cellular Alkaline Phosphatase Activity Using Gold Nanoflower Probe and Localized Surface Plasmon Resonance Technique
摘要： In this work, a simple and ultrasensitive localized surface plasmon resonance (LSPR) method that use Au nanoflowers (AuNFs) as probe was designed for in-situ monitoring of alkaline phosphatase (ALP) activity. The AuNFs was fabricated by hydrogen tetrechloroaurate-induced oxidative disruption of polydopamine-coated Au nanoparticles (AuNPs) and subsequently growth of Au nanopetals on AuNPs. The as-prepared AuNFs showed a much higher LSPR capability and stronger scattering color change than AuNPs. The strategy for in-situ cellular ALP activity detection relied on the deposition of Ag on AuNFs surface, which changed the morphology of AuNFs and led to a tremendous LSPR response and scattering color change. The deposition of Ag shell on AuNFs was related to ALP activity, where ALP catalyzed the hydrolysis of L-ascorbic acid 2-phosphate sesquimagnesium salt hydrate to form L-ascorbic acid (AA), then AA reduced Ag+ to Ag and deposited onto AuNFs. With this concept, the ALP activity could be monitored with a detection limit of 0.03 μU L-1. Meanwhile, the ALP activity of single HepG2 cells and HEK 293 cells was tracked with proposed approach, which indicated the trace expression level of ALP in HEK 293T cell and overexpressed level of ALP in HepG2 cells. After treated with drugs, the cellular ALP activity of HepG2 cells was decreased with the treating time and dose increasing. Therefore, the proposed strategy could be used for tracking the cellular ALP activity, which paved a new avenue for cell studies, and hold great potential for discovering novel ALP-based drugs applications.
关键词： cellular activity,alkaline phosphatase,localized surface plasmon resonance,in-situ imaging,gold nanoflowers
更新于2025-09-23 15:21:21
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High-Performance Biobased Unsaturated Polyester Nanocomposites with Very Low Loadings of Graphene
摘要： Graphene-reinforced tung oil (TO)-based unsaturated polyester nanocomposites were prepared via in situ melt polycondensation intergrated with Diels–Alder addition. Functionalized graphene sheets derived from graphene oxide (GO) were then extracted from the obtained nanocomposites and carefully characterized. Furthermore, dispersion state of the graphene nanosheets in the cured polymer composites and ultimate properties of the resultant biobased nanocomposites were investigated. Mechanical and thermal properties of the TO-based unsaturated polyester resin (UPR) were greatly improved by the incorporation of GO. For example, at the optimal GO content (only 0.10 wt %), the obtained biobased nanocomposite showed tensile strength and modulus of 43.2 MPa and 2.62 GPa, and Tg of 105.2 ?C, which were 159%, 191%, and 49.4% higher than those of the unreinforced UPR/TO resin, respectively. Compared to neat UPR, the biobased UPR nanocomposite with 0.1 wt % of GO even demonstrated superior comprehensive properties (comparable stiffness and Tg, while better toughness and thermal stability). Therefore, the developed biobased UPR nanocomposites are very promising to be applied in structural plastics.
关键词： unsaturated polyester resins,graphene,in situ melt polycondensation,tung oil,biobased polymer nanocomposites
更新于2025-09-23 15:21:21
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New Insights Into the Growth Mechanism of Ultrathin Au Nanowires from Combined In-Situ EXAFS and SAXS Studies
摘要： The synthesis at room temperature of Au nanowires (NWs) in hexane solution of HAuCl4.3H2O, oleylamine and triisopropylsilane, was “in-situ” monitored by means of X-ray Absorption Fine Structure Spectroscopies and Small Angle X-Ray Scattering to determine, under identical synthesis conditions, both the changes of the oxidation state of gold atoms and the evolution of the size and shape of the objects involved in the formation of Au NWs. We propose a multi-stage process for the formation of the NWs: first, Au(III) atoms form a planar-square geometry complex that is continuously reduced to give Au(I) disc-like structures with diameters bigger than that of the final NWs. In a second stage, characteristic length/thickness ratio of these disc-like objects increases to form cylinders, presumably by aurophilic interactions between Au(I) centers and stacking of the discs. When most of the Au atoms have been reduced to Au(I), the reduction to Au(0) begins (third stage) and the NWs grow forming an hexagonal arrangement, separated by a bilayer of oleylamine molecules (fourth stage). Finally, a slow reduction leads the reaction to the final product, formed by bundles of long, ultrathin Au NWs.
关键词： triisopropylsilane,in-situ EXAFS,growth mechanism,SAXS,Au nanowires,oleylamine
更新于2025-09-23 15:21:21
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Correlations between thermal history and keyhole porosity in laser powder bed fusion
摘要： Additive manufacturing has the potential to revolutionize the production of metallic components as it yields near net shape parts with complex geometries and minimizes waste. At the present day, additively manufactured components face qualification and certification challenges due to the difficulty in controlling defects. This has driven a significant research effort aimed at better understanding and improving processing controls – yielding a plethora of in-situ measurements aimed at correlating defects with material quality metrics of interest. In this work, we develop machine-learning methods to learn correlations between thermal history and subsurface porosity for a variety of print conditions in laser powder bed fusion. Un-normalized surface temperatures (in the form of black-body radiances) are obtained using high-speed infrared imaging and porosity formation is observed in the sample cross-section through synchrotron x-ray imaging. To demonstrate the predictive power of these features, we present four statistical machine-learning models that correlate temperature histories to subsurface porosity formation in laser fused Ti-6Al-4V powder.
关键词： in-situ measurement,keyhole porosity,machine learning,laser powder bed fusion,x-ray imaging
更新于2025-09-23 15:21:01
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In situ monitoring silver adsorption on assembled gold nanorods by surface-enhanced Raman scattering
摘要： Self-assembly of metal nanocrystals is capable to create a gap of sub-nanometer distance for concentrating the incoming light by the strong coupling of surface plasmon resonance, known as “hot spot”. Although the plasmonic property of silver is better than the other metals in the visible range, the superior Raman enhancement of silver comparing to gold is still under debate. To provide direct evidence, in this work, we studied the silver adsorption on assembled gold nanorods (AuNRs) by in situ surface-enhanced Raman scattering (SERS) measurement. The self-assembled AuNR multimers were used as the SERS substrate, where the 4-mercaptophenol (MPh) molecules in our experiment played dual roles as both probe molecules for the Raman scattering and linking molecules for the AuNR assembly in a basic environment. Silver atoms were adsorbed on the surface of gold nanorod assemblies by reduction of Ag+ anions. The stability of the adsorbed silver was guaranteed by the basic environment. We monitored the SERS signal during the silver adsorption with a home-built in situ Raman spectroscopy, which was synchronized by recording the UV-vis absorption spectra of the reaction solution to instantly quantify the plasmonic effect of the silver adsorption. Although a minor change was found in plasmonic resonance wavelength or intensity, the measured SERS signal at specific modes faced a sudden increase by 2.1 folds during the silver adsorption. The Finite element method (FEM) simulation confirmed that the silver adsorption corresponding to the plasmonic resonance variation gave little change to the electric field enhancement. We attributed the mode-specific enhancement mechanism of the adsorption of silver to the chemical enhancement from charge transfer (CT) for targeting molecules with a specific orientation. Our findings provided new insights to construct SERS substrates with higher enhancement factor (EF), which hopefully would encourage new applications in the field of surface-enhanced optical spectroscopies.
关键词： Surface-enhanced Raman scattering,In situ measurement,Enhancement mechanism
更新于2025-09-23 15:21:01
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In situ monitoring of the layer height in laser powder bed fusion
摘要： In situ process monitoring has frequently been cited as an critical requirement in certifying the performance of laser powder bed fusion (LPBF) components for use in high integrity applications. Despite much development in addressing this need, little attention has been been paid to monitoring the layer thickness during the process. In this paper, a laser displacement sensor has been integrated into the build chamber of an LPBF machine, and the height of the top surface layer of a component has been monitored during a build. This has permitted the deposited layer thickness to be measured throughout the build, and the effect on this of a change in processing conditions is characterised. The thermal contraction of the top layer in between successive laser scans has also been evaluated. This demonstrates the potential of utilising laser displacement sensory as a process monitoring tool in LPBF and provides insightful data for implementation in detailed process models.
关键词： 316L steel,in situ testing,selective laser melting
更新于2025-09-23 15:21:01
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New Developments for the Repair of Structural Engine Components with Laser Material Deposition
摘要： Driven by today’s typical “power by the hour” type aftermarket support contracts (e.g. Corporate Care and Total Care) the demands for continuous operation of aircraft engines have increased significantly. For this reason, any disruption caused by heavy maintenance needs to be avoided. Where needed, repair operations should be as time, cost and material efficient as possible. However, service disruptions will still occur and wherever possible, the resulting maintenance intervention activities should take place either “on-wing” or “near-wing”. Consequently, it is the intention of Rolls-Royce to introduce more and more in-situ and minimal invasive maintenance capabilities, such as endoscopic laser material deposition (LMD), for the repair of structural engine components. This article describes the challenges of the minimal invasive LMD process inside cavities and the continued development requirements over and above today’s state-of-the-art repair capability. It also provides further insight concerning the ongoing development of equipment that combines viewing and LMD capability and an outlook on the application of the developed technology.
关键词： Endoscopic Devices,Laser Material Deposition,Structural Engine Components,Rolls-Royce,In-situ Repair
更新于2025-09-23 15:21:01
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<i>In situ</i> study of the film formation mechanism of organica??inorganic hybrid perovskite solar cells: controlling the solvate phase using an additive system
摘要： As a coating method compatible with printing, one-step spin-coating is widely used for fabricating perovskite thin films. Controlling the crystal growth rate of two precursors is essential to obtain a homogeneous film morphology. However, the film formation mechanism and role of solvate systems during spin-coating have not yet been clearly revealed. In this work, we implemented the in situ grazing incidence wide-angle X-ray scattering of CH3NH3PbI3 perovskite material based on various additive systems to adjust the unbalanced crystal growth rate of CH3NH3I and PbI2. As we expected, the behavior of the solvate phase was strikingly mediated by various additives, and one of the additives greatly slowed the PbI2 solvate phase, thus overcoming the imbalance in the crystal growth rate. Consequently, the well-controlled perovskite films have both good film morphology and high photovoltaic performance with excellent reproducibility.
关键词： in situ study,solvate phase,perovskite solar cells,film formation mechanism,additive system
更新于2025-09-23 15:21:01
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Generalized local analogue model for nonlocal plasmonic nanostructures based on multiple-fluid hydrodynamic framework
摘要： The control and manipulation of light waves is a long-standing ambition with profound implications for the development of science and technology. Recent advances in nanofabrication allow for a rapid progress in engineering plasmonic nano-devices which collect and concentrate light or electromagnetic waves into a subwavelength region, enabling various applications in nanophotonics, such as bio-sensor with enhanced sensitivity, plasmonic laser, plasmonic colors and quantum plasmonics, to name a few. Spatial dispersion plays a critical role in nanophotonics when small plasmonic structures with feature sizes of few nanometers are handled. Such nonlocality is typically considered in a hydrodynamic framework and generally requires solving coupled partial differential equations, and therefore is involved. We develop a generalized local analogue model to reflect the nonlocal effects of plasmonic structures and avoid the complicated analysis within the multiple-fluid hydrodynamic framework, where more than one kind of charge carriers is considered. We show that spatial nonlocality can be represented by simply replacing the nonlocal surface region with an in-situ artificial local dispersive film. With such an elegant and simple-to-use alternative, the conventional analysis and simulations in the local regime acquire nonlocal capability, sufficient for a quantitative description of various plasmonic structures in nanoscale, rendering a much simpler process and great practical advantages in the numerical treatment.
关键词： multiple fluid,in-situ local model,nonlocal response,hydrodynamic Drude model
更新于2025-09-23 15:21:01