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Laser cooling arc plasma effect in laser-arc hybrid welding of 316L stainless steel
摘要： Current laser-plasma interaction theory supports that the plasma energy e.g. electron temperature would increase by the effect of inverse bremsstrahlung (IB) absorption, when a laser beam passed through the plasma. However, in this paper, we found an interesting laser cooling arc plasma effect (LCAPE) during kilo-Watt fiber laser-TIG hybrid welding. Based on theoretical modelling and experiments, we observed that a temperature decrease of more than 5000 K at the tail of the argon plasma occurred under different process parameters during hybrid welding of 316L stainless steel. We proposed the LCAPE is caused by the laser-induced metal vapor. The mechanism mainly includes the convection cooling and enhanced radiation of the arc plasma by the metal vapor. Our findings could broaden the theory of laser-plasma interaction and provide a theoretical reference to the modulation and control of plasma in industries.
关键词： Cooling effect,Stainless steel,Laser-arc hybrid welding,Arc plasma,Fiber laser
更新于2025-11-28 14:24:20
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Inconel625/316L functionally graded material using spectral diagnostics during laser additive manufacturing process
摘要： In this paper, the composition of Inconel625/316L functionally graded material during the additive manufacturing process was monitored on-line by laser-induced plasma optical emission spectroscopy. Several spectral lines are used to establish the quantitative relationship between relative intensity, relative intensity ratio, plasma temperature, and functional gradient material composition variation. It is shown that the change between relative strength and compositional content is similar to actual expectations. But, the relationship between the relative intensity with Inconel625 content is nonlinear. Cr-I/Ni-I relative intensity ratios almost linearly decrease with increasing Inconel625 content. The linear correlation coe?cient of the best ?tted curve was 0.943, and the maximum percentage error was 7.5%. The plasma temperature was obtained by the Boltzmann plot using ?ve neutral chrome lines between 330 and 380 nm. Plasma temperature almost linearly increases with increasing Inconel625 content in a range. The linear correlation coe?cient of the plasma temperature ?tted straight line was 0.93, and the maximum percentage error was 2.7%. The feasibility of composition monitoring of gradient materials by spectral information during the additive manufacturing process was veri?ed.
关键词： plasma temperature,spectral diagnosis,laser additive manufacturing,composition monitoring
更新于2025-11-28 14:24:20
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Repulsive magnetic field–assisted laser-induced plasma micromachining for high-quality microfabrication
摘要： Surface micro-/nanostructures are widely used in the fabrication of various functional microsystems. Laser-induced plasma micromachining can greatly improve surface quality in terms of recast layers and thermal defects compared with laser direct writing. Magnetic field has the ability to constrain plasma diffusion and can ensure the stability of laser-induced plasma processing. This paper compares the effects of laser direct–writing processing and laser-induced plasma processing of single-crystal silicon at the micro-/nanoscale, and emphatically analyzes the material removal mechanism of repulsive magnetic field–assisted laser-induced plasma micromachining. It is shown that the volume of the laser-induced plasma was constrained under the influence of Lorentz force, a high-quality smooth microgroove without thermal defects was obtained, and its line width was reduced by 30%.
关键词： Laser-induced plasma micromachining,Magnetic confinement,Thermal defects,Micro-/nanofabrication
更新于2025-11-21 11:24:58
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Grain growth mechanism and thermoelectric properties of hot press and spark plasma sintered Na-doped PbTe
摘要： We investigated he thermoelectric (TE) properties and microstructures of Na-doped PbTe compounds, synthesized by various milling and sintering processes. It has been generally accepted that spark plasma sintering (SPS) inhibits grain growth due to the short sintering time, which is bene?cial to the nano bulk composite. In contrast, we observed abnormal grain growth for SPS, unlike hot press (HP) sintering. Considering the Gibbs free energy change during sintering, the HP sintering increases internal energy while the SPS increases entropy energy, which causes the abnormal grain growth. Lattice strain and Fourier transform analyses of the transmission electron microscope images showed that the SPS sintered samples had more signi?cant lattice strains and defects than the HP sintered samples. The low thermal conductivity of the SPS sintered samples was not from grain boundary phonon scattering but from phonon scattering by lattice strains and defects. The lattice strains and defects decreased electrical conductivity as well, resulting in deterioration of the power factor and thermoelectric performance. This suggests that the lattice strains and defects are more critical factors for enhancing thermoelectric per- formance than particle and grain size control.
关键词： Grain growth,Thermoelectric,Hot press,Spark plasma sintering,ZT
更新于2025-11-21 10:59:37
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Facile preparation of boron and nitrogen co-doped green emission carbon quantum dots for detection of permanganate and captopril
摘要： A hydrothermal strategy for preparing boron and nitrogen co-doped carbon quantum dots was studied using the precursors of p-amino salicylic acid, boric acid and ethylene glycol dimethacrylate. The boron and nitrogen co-doped carbon quantum dots have high fluorescence intensity, good monodispersity, high stability, superior water solubility, and a fluorescence quantum yield of 19.6%. Their average size is 5 nm. Their maximum excitation and emission wavelengths are 380 nm and 520 nm, respectively. Permanganate (MnO4-) quenched boron and nitrogen co-doped carbon quantum dots fluorescence through inner filter effect and static quenching effects. The linear relation between quenching efficiency and MnO4- concentration ranged from 0.05 to 60 μmol/L with a detection limit of 13 nmol/L. In the presence of captopril, MnO4- was reduced to Mn2+ and the fluorescence of boron and nitrogen co-doped carbon quantum dots was recovered. The linear range between recovery and captopril concentration was from 0.1 to 60 μmol/L. The limit of detection was 0.03 μmol/L. The developed method can be employed as a sensitive fluorescence sensing platform for MnO4-. It has been successfully used for captopril detection in mouse plasma.
关键词： Captopril,Plasma,Fluorescence,Potassium permanganate,Carbon quantum dots
更新于2025-11-19 16:56:42
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Atmospheric Pressure Plasma Synthesized Gold Nanoparticle/Carbon Nanotube Hybrids for Photo-thermal Conversion
摘要： In this work, a room temperature atmospheric pressure direct-current plasma has been deployed for the one-step synthesis of gold nanoparticle/carboxyl group functionalized carbon nanotube (AuNP/CNT-COOH) nanohybrids in aqueous solution for the first time. Uniformly distributed AuNPs are formed on the surface of CNT-COOH, without the use of reducing agents or surfactants. The size of the AuNP can be tuned by changing the gold salt precursor concertation. UV-Vis, ζ-potential and X-ray photoelectron spectroscopy suggest that carboxyl surface functional groups on CNTs served as nucleation and growth sites for AuNPs and the multiple potential reaction pathways induced by the plasma-chemistry have been elucidated in detail. The nanohybrids exhibit significantly enhanced Raman scattering and photothermal conversion efficiency, properties that are essential for potential multi-modal cancer treatment applications.
关键词： Surface Enhanced Raman Scattering,Gold Nanoparticles,Photothermal Conversion,Carbon Nanotubes,Plasma Synthesis
更新于2025-11-19 16:56:35
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Dielectric tunable properties of Ba0.5Sr0.5TiO3?Mg2TiO4?MgO composite ceramics prepared by spark plasma sintering
摘要： Ba0.5Sr0.5TiO3?Mg2TiO4?MgO composite ceramics were prepared by spark plasma sintering (SPS) technique and their phase composition, microstructures and dielectric tunable properties were studied. With increasing Mg2TiO4?MgO content, the dielectric peaks of Ba0.5Sr0.5TiO3?Mg2TiO4?MgO composite ceramics were broadened and suppressed. The tunability of Ba0.5Sr0.5TiO3?Mg2TiO4?MgO composite ceramics first increased and then decreased with the increase of Mg2TiO4?MgO content. For Mg2TiO4?MgO content ≤ 50 wt%, Ba0.5Sr0.5TiO3?Mg2TiO4?MgO composite ceramics showed higher tunability and lower permittivity than pure Ba0.5Sr0.5TiO3, which can be attributed to the suppression of the doping effect by SPS. The contradiction between reduced permittivity and enhanced tunability in ferroelectric-dielectric composites was resolved.
关键词： Dielectrics,Ferroelectric ceramics,Spark plasma sintering,Composites
更新于2025-11-14 17:28:48
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Ellipsometric study on optical properties of hydrogen plasma-treated aluminum-doped ZnO thin film
摘要： Aluminum-doped zinc oxide (AZO) thin films were prepared by radio frequency (RF) sputtering at room temperature, and then post-treated by hydrogen (H2) plasma at different durations. After H2 plasma treatment under the condition of 10 W, 200 °C and 3.0 Hours, the resistivity showed a dramatically decrease from 1.6 Ω cm to 3.4 × 10?3 Ω cm, while the transmittance at the wavelength of 550 nm was improved from 90.5% to 96.0%. The optical constants of H2 plasma-treated AZO thin films were detailed characterized by a varied angle spectroscopic ellipsometer. The results show that the refractive index n decreases in the entire measured wavelength range of 350–1100 nm, while the extinction coefficient k decreases in the short wavelength range and changes negligibly at the long wavelength range. These results can provide guidelines for the design and optimization of AZO thin film-based optoelectronic applications.
关键词： Resistivity,Spectroscopic ellipsometer,Transmittance,Optical constants,Hydrogen plasma treatment,Aluminum-doped zinc oxide
更新于2025-11-14 17:03:37
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The atomic layer etching of molybdenum disulfides using low-power oxygen plasma
摘要： The layered removal mechanisms of molybdenum disul?des (MoS2) using low-power oxygen plasma are investigated in this paper. After the low-power oxygen plasma treatment, the topmost MoS2 layer is completely oxidized. The weaker adhesion of Mo oxides with MoS2 surfaces would lead to the detachment of the topmost oxidized MoS2 layer from the underlying MoS2 ?lms. Since MoS2 is insoluble and Mo oxides are soluble in water, an additional dipping procedure of the sample in de-ionized water will help with the complete detachment of the topmost oxidized MoS2 layer. With a re-sulfurization procedure after the removal process, the partially oxidized MoS2 ?lm remaining on the substrate can be recovered back to a complete MoS2 ?lm. Both optical and electrical characteristics of the MoS2 ?lms can be maintained after the removal procedure. By repeating the same procedure, a layer-by-layer removal of MoS2 is demonstrated, which provides an easy and fast approach to determine the number of layers of the 2D material.
关键词： layered removal,oxygen plasma,layer number controllability
更新于2025-11-14 17:03:37
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Preparation of Ag-doped Bi5O7I composites with enhanced visible-light-induced photocatalytic performance
摘要： A novel heterostructure photocatalysts, Ag-doped Bi5O7I composites (Ag/Bi5O7I), were synthesized by a simple hydrothermal method. Compared with Bi5O7I, Ag/Bi5O7I composites had a stronger light absorption in the visible and near-infrared region and the light absorption edge of Ag/Bi5O7I composites had a slight red shift. Moreover, Ag/Bi5O7I composites possessed a higher photocatalytic activity than Bi5O7I on the degradation of rhodamine B (RhB) and methyl orange (MO) under visible-light irradiation (λ ≥ 420 nm). When the content of Ag was 1%, the degradation efficiency of the Ag/Bi5O7I composites toward RhB and MO reached the maximum value, which was about 20.2 and 7.6 times higher than that of Bi5O7I, respectively. The trapping experiments shown that superoxide radicals and holes were the main active species in the photodegradation process. The excellent photocatalytic performance could be attributed to Ag/Bi5O7I heterojunction and surface plasma resonance effect of Ag, which could increase absorption of visible light and cause the efficient separation and migration of carriers.
关键词： Ag-doped Bi5O7I,Visible-light,Surface plasma resonance,Heterostructure photocatalysts
更新于2025-11-14 17:03:37