- 标题
- 摘要
- 关键词
- 实验方案
- 产品
过滤筛选
- 2018
- interdigital resonator
- microwave gas sensor
- PSE-coated
- Optoelectronic Information Science and Engineering
- King Mongkut’s University of Technology North Bangkok
- Rajamangala University of Technology Suvarnabhumi
-
Hybrid laser-metal inert gas keyhole welding of thick steel/Al butt joints
摘要： Dissimilar joining of steel/Al joints has become more and more signi?cant in industrial applications with particular weight saving interest. However, directly welding of steel/Al joints even in thin thickness is very di?cult. In the present study, the hybrid laser-metal inert gas (MIG) source focused on the steel side in keyhole mode was introduced to weld steel/Al butt joints of 6 mm in thickness. E?ects of the laser o?sets on the weld shape, interface microstructures, and ultimate tensile strength (UTS) of the steel/Al joints were investigated. Sound steel/Al butt joints were obtained by using this hybrid laser-MIG keyhole welding process. By increasing the laser o?sets from 0.6 and 0.8 mm, the welds exhibited a better shape with a smooth appearance attributable to the reduced heat input. The positions through the thickness of the steel/Al joints played an important role in the morphology and thickness of the intermetallic compound (IMC) layers at the Al/weld interface. The IMC layers had a thick irregular morphology at the upper part and the lower part, while the layers at the middle part exhibited a relatively thin and uniform morphology. With some certain welding conditions, the Al/weld interface at the lower part of the steel/Al joints transformed to a welding-brazing mode from a fusion one. The island-shape structures were formed at the Al/weld interface, and the IMC layers were composed of Fe2Al5 layer and needlelike Fe4Al13 phases. The maximum UTS of 87.0 MPa was obtained at a laser o?set of 0.6 mm. Although the failure occurred in the IMC layers revealed a brittle fracture, the fracture morphology and locations were a mixed failure, which had a certain resistance to the crack propagation of the IMC layers.
关键词： laser-metal inert gas welding,ultimate tensile strength,keyhole welding,intermetallic compound,steel/Al joints
更新于2025-11-28 14:24:20
-
Mid infrared gas spectroscopy using efficient fiber laser driven photonic chip-based supercontinuum
摘要： Directly accessing the middle infrared, the molecular functional group spectral region, via supercontinuum generation processes based on turn-key fiber lasers offers the undeniable advantage of simplicity and robustness. Recently, the assessment of the coherence of the mid-IR dispersive wave in silicon nitride (Si3N4) waveguides, pumped at telecom wavelength, established an important first step towards mid-IR frequency comb generation based on such compact systems. Yet, the spectral reach and efficiency still fall short for practical implementation. Here, we experimentally demonstrate that large cross-section Si3N4 waveguides pumped with 2 μm fs-fiber laser can reach the important spectroscopic spectral region in the 3–4 μm range, with up to 35% power conversion and milliwatt-level output powers. As a proof of principle, we use this source for detection of C2H2 by absorption spectroscopy. Such result makes these sources suitable candidate for compact, chip-integrated spectroscopic and sensing applications.
关键词： mid infrared,photonic chip,gas spectroscopy,supercontinuum generation,fiber laser
更新于2025-11-28 14:23:57
-
Diode-pumped single-pass tunable mid-infrared gas Raman source by methane-filled hollow-core fiber
摘要： We report here, to the best of our knowledge, the first diode-pumped single-pass tunable mid-infrared fiber gas Raman laser source using methane-filled hollow-core fibers. Pumped by a homemade tunable high peak-power amplified diode laser, whose wavelength covers the range of 1540 nm to 1560 nm, the mid-infrared laser emission over the range of 2796 nm to 2863 nm is generated by the stimulated Raman scattering of methane molecules. The highest average output power of ~34 mW at 2829 nm is achieved with 14.2 m fiber at 16 bar when pumped at 1550 nm. This paper opens new opportunities for compact tunable mid-infrared fiber lasers.
关键词： gas lasers,Raman lasers,fibre lasers,stimulated Raman scattering
更新于2025-11-28 14:23:57
-
Cascaded Mach-Zehnder interferometers with Vernier effect for gas pressure sensing
摘要： We propose a compact ultrasensitive gas pressure fiber sensor based on cascaded Mach-Zehnder interferometers (MZI) with Vernier effect. Each MZI is composed of a hollow core fiber (HCF) sandwiched in between two short multimode fibers (MMF). The lengths of the HCFs in the two MZIs are set a little different in order to generate an envelope in the transmission spectrum of the cascaded structure for Vernier effect sensing. The HCF in one MZI is opened to make the air hole connect to the external environment and act as sensing element. The HCF in the other MZI is kept closed serving as reference element. The two MZIs have quite different responses to changes in gas pressure, but have almost the same response to temperature variation. Therefore, the Vernier effect occurs when the gas pressure changes, but not when the temperature varies. As a result, the proposed structure has an ultra-high gas pressure sensitivity with a quite low temperature cross-sensitivity. Experimental results show that the gas pressure sensitivity referring to the envelope of the proposed sensor is -73.32 nm/MPa in the range of 0 - 0.8 MPa, with a temperature cross-sensitivity of only 0.72 kPa/°C.
关键词： Vernier effect,gas pressure,Hollow core fiber,Mach-Zehnder interferometer
更新于2025-11-28 14:23:57
-
Highly sensitive and selective room-temperature NO2 gas-sensing characteristics of SnOX-based p-type thin-film transistor
摘要： The high-performance p-type metal-oxide-semiconductor (MOS)-based gas sensor is an important subject of research in the field of gas-sensing technology. In this work, we demonstrated a p-type MOS-based thin-film transistor (TFT) nitrogen dioxide (NO2) gas sensor that used tin oxide (SnOX) for both the channel and sensing layers. The crystalline status, surface morphology, and atomic-bonding configuration of the thin-film were examined using X-ray diffraction, field emission-scanning electron microscopy, and X-ray photoelectron spectroscopy. The results indicated that the deposited thin-film was mainly composed of polycrystalline SnO with a tetragonal structure. The fabricated p-type SnOX TFT showed a maximum response value of 19.4-10 ppm NO2 at room temperature (RT, 25 °C) when operated in the subthreshold region, which was significantly higher than that of 2.8–10 ppm NO2 obtained from a p-type SnOX thin-film chemiresistor at RT. In addition, the SnOX TFT gas sensor showed significantly higher sensitivity to NO2 gas than to other target gases such as NH3, H2S, CO2, and CO at RT. To the best of our knowledge, this is the first study to a p-type MOS-based field-effect transistor-type gas sensor. Our experimental results demonstrate that the p-type SnOX TFT is a promising gas sensor that can operate at RT with high sensitivity and selectivity to NO2 gas.
关键词： SnO,Thin-film transistor,NO2 gas sensing,SnOX,P-type metal oxide semiconductor
更新于2025-11-21 11:01:37
-
A high-performance room temperature methanol gas sensor based on alpha-iron oxide/polyaniline/PbS quantum dots nanofilm
摘要： A high-performance room temperature methanol gas sensor based on alpha-iron oxide/polyaniline/lead sulfide quantum dots (α-Fe2O3/PANI/PbS QDs) nanofilm was demonstrated in this paper, among which the α-Fe2O3 was an urchin-shaped hollow microsphere. The sensing film was fabricated on an epoxy substrate with interdigital electrodes via successive ionic layer adsorption and reaction technique. The prepared α-Fe2O3/PANI/PbS QDs nanocomposite was examined by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, scanning election microscopy and Fourier transform infrared spectrum. The methanol sensing performances of the α-Fe2O3/PANI/PbS QDs film sensor were investigated against methanol from 10 to 100 ppm at room temperature. The experimental results indicated that the methanol sensor in this work had an excellent response, outstanding selectivity and good repeatability at room temperature. The underlying sensing mechanism of the α-Fe2O3/PANI/PbS QDs film toward methanol was ascribed to a series of interactions and changes on the surface of thin films, which make their resistance change greatly. Larger surface area and much more active adsorption sites also played an important role.
关键词： Methanol gas sensor,Room temperature,Successive ionic layer adsorption and reaction,Hydrothermal method,α-Fe2O3/PANI/PbS QDs
更新于2025-11-14 17:15:25
-
Ethanol sensing properties and reduced sensor resistance using porous Nb2O5-TiO2 n-n junction nanofibers
摘要： One-dimensional (1D) and porous Nb2O5-TiO2 n-n junction nanofibers with different Nb molar ratios have been synthesized by a simple electrospinning approach. A decrease in the average grain size and consequently an increase in the specific surface area were observed due to the introduction of Nb2O5 into TiO2 nanofibers. In comparison with pure TiO2 nanofibers, the Nb2O5-TiO2 nanofibers exhibited improved ethanol sensing response and a reduction in electrical resistance. The optimum operation temperature was reduced from 300 °C for pure TiO2 to 250 °C for Nb2O5-TiO2. The best sensing property was found for Nb2O5-TiO2 with 6 mol% Nb2O5, showing the highest response of 21.64–500 ppm ethanol at 250 °C, which was 2.79 times as high as that of pure TiO2 nanofibers at 300 °C. The reduction of Nb2O5-TiO2 based sensor resistance was attributed to the substitution of Ti4+ by Nb5+ ions and the formation of n-n junctions between Nb2O5 nanoparticles and TiO2 nanoparticles. The enhancement sensing mechanism of Nb2O5-TiO2 nanofibers was mainly ascribed to the enhanced resistance modulation owing to the substitution of Ti4+ by Nb5+ ions, formation of n-n junctions, and high surface area as well as small grain size of Nb2O5-TiO2 nanofibers.
关键词： Gas sensor,n-n junctions,Electrospinning,Nb2O5,TiO2
更新于2025-11-14 17:15:25
-
Rapid gas-liquid detonation synthesis of core-shell structural graphite coated TiO2 nanoparticles
摘要： Here we demonstrate a simple, rapid for the controlled synthesis of core-shell structural graphite coated TiO2 nanoparticle (TiO2@G), which are directly prepared by detonation chemical decomposition of the gas-liquid mixture of CH4, O2, C6H6 and TiCl4 in milliseconds. Various techniques, including XPS, TEM, XRD and Raman were employed to investigate the products. It is found that the sphere, good disperse mixed crystal TiO2 nanoparticles with crystal size of 10–30 nm were coated with thick graphite layers. Based on Zeldovich Neuman-Doring (ZND) model, the detonation synthesis mechanism of core-shell structure TiO2@G is discussed. This rapid synthesis method can be extended to the preparation of other core-shell materials.
关键词： Gas-liquid detonation,Graphite coated TiO2,Core-shell structure,Composite materials,Formation mechanism
更新于2025-11-14 17:04:02
-
Liquefied petroleum gas sensing properties of ZnO/PPy/PbS QDs nanocomposite prepared by self-assembly combining with SILAR method
摘要： In this paper, a high-performance liquefied petroleum gas (LPG) sensor based on zinc oxide/polypyrrole/lead sulfide quantum dots (ZnO/PPy/PbS QDs) nanocomposite film was demonstrated, which was fabricated by layer-by-layer (LbL) self-assembly and successive ionic layer adsorption and reaction (SILAR) technique. The nanostructure features of the as-prepared ZnO/PPy/PbS nanocomposite film were confirmed by various characterization techniques. The room temperature gas-sensing investigation of the ZnO/PPy/PbS QDs nanocomposite sensor was performed against LPG gas in a wide concentration range. The experimental results showed an outstanding response for LPG sensing at room temperature compared with previous reports, the response can reach 45.47% at 1000 ppm LPG. And it also demonstrated good selectivity and excellent repeatability. The sensing mechanism of the PPy/ZnO/PbS QDs nanocomposite film gas sensor is owing to the p-n heterojunction created at the ZnO/PPy interface, as well as much more active adsorption sites.
关键词： polypyrrole,liquefied petroleum gas,zinc oxide,lead sulfide quantum dots,SILAR method
更新于2025-11-14 17:04:02
-
Rational design of sensitivity enhanced and stability improved TEA gas sensor assembled with Pd nanoparticles-functionalized In2O3 composites
摘要： In this work, special triethylamine (TEA) gas sensors based on Pd nanoparticles (NPs)-decorated In2O3 microstructures with different Pd amount have been successfully fabricated. The optimal sensor based on 3 wt% Pd-loaded In2O3 shows higher gas response compared with other content of Pd wt% and exhibits the highest response of 47.56 when exposed to 50 ppm TEA gas. Furthermore, 3 wt% Pd NPs-In2O3 sensor not only possesses superior response and recovery properties of 4 s and 17 s under 50 ppm TEA gas, respectively, but also displays outstanding selectivity to TEA gas at the existence of other interfering gases. Based on the model of depletion layer, the possible gas sensing mechanism are studied and the results show that, the synergistic effect between the sensitization exerted by Pd nanoparticles and structural defects may be responsible for the remarkably enhanced TEA sensing performance. Considering the superiority including low cost, simple structure, and facile fabrication, 3 wt% Pd NPs-In2O3 microstructures are promising for high-performance TEA sensing applications.
关键词： Triethylamine,In2O3,Gas sensors
更新于2025-11-14 17:04:02