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- 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
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Localized Surface Plasmon Resonance Sensor Based at Metallic Sphere Dimer Particle
摘要： By the cooling holes in aero-engine turbine blade as the research object, this study focuses on two kinds of electrochemical machining(ECM) methods, which are mix gas added to the nonlinear electrolyte (NaNO3) and non-mixed gas. Mixed and non-mixed gas ECM experiments of turbine blade cooling holes were carried out respectively. The corresponding two-dimensional CAD model of cooling hole was constructed combined with the experimental data and theoretical analysis. Numerical simulation analysis was carried out of the flow field base on the above models by using the fluid dynamics analysis software FLUENT. The influence flow velocity and flow velocity distribution on the machining accuracy and efficiency of ECM were investigated in detail. The vortex zone distribution of gas-NaNO3 mixed phase flow field and single NaNO3 solution flow field was analyzed qualitatively. The simulation results indicated that the flow velocity in the machining gap with mixed gas was significantly higher than the velocity during ECM process for cooling holes. The electrolytic products and heat were washed away completely, the electrolyte can be updated in time. Fluid vortex zone distribution was improved obviously, the flow field distribution became more uniform after mixed gas in ECM process. The machining accuracy and efficiency for cooling holes making may be improved greatly with gas mixed in electrolyte NaNO3.
关键词： electrolytic machining,mixed gas,cooling hole,gas-liquid two-phase flow,CFD
更新于2025-09-23 15:22:29
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Detection of NH<SUB>3</SUB> Using ZnO Thin Film Sensor Deposited on Si/SiO<SUB>2</SUB> Substrate Derived by RF Magnetron Sputtering
摘要： This paper reports the research results of Zinc Oxide (ZnO) thin film gas sensor which is able to detect low concentration of ammonia gas (NH3). Pure ZnO layer is deposited on Si/SiO2 substrate at room temperature by RF magnetron sputtering technique. Pt micro-heater, platinum resistance thermometer (PRT) and gold electrodes are also fabricated along with ZnO thin film to make a complete NH3 sensor device and the fabrication process is discussed in detail in this manuscript. The deposited ZnO thin film is annealed at different temperatures and the effect of annealing temperature on the properties of ZnO thin film is analyzed by using various characterization techniques such as surface profilometer, XRD, SEM, EDX, etc. A measurement set-up is established for the measurements of various sensor parameters. An operating temperature is optimized for the NH3 gas sensor to enhance the sensitivity of the device. The optimized operating temperature is achieved and measured by Pt heater and PRT, respectively. The measurements are also performed for Pt micro-heater and PRT to calibrate the temperature with respect to heater current. Finally, the gas sensing measurements are performed in the range of small NH3 concentration (below 10 ppm) and the results confirm very good sensitivity even in very small NH3 concentration.
关键词： NH3 Gas,Thin Film,Pt Microheater,NH3 Gas Sensor,RF Sputtering,ZnO
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE SENSORS - New Delhi, India (2018.10.28-2018.10.31)] 2018 IEEE SENSORS - A Flexible Room Temperature Ammonia Sensor Based on Large Area, Transparent Single Wall Carbon Nanotube Thin Film
摘要： A low-temperature, wet-chemical process for the synthesis of single wall carbon nanotubes (SWCNTs) films on large area, transparent, flexible substrates were developed and its application to ammonia detection at room temperature were demonstrated. The carboxyl groups were attached in the sidewalls of carbon nanotubes due to wet-chemical process which helps to improve the sensor performance. The transmittance measurement showed that the film is ninety percent transparent to visible spectrum with respect to air. Selectivity measurements were also performed. The sensor responses were same for both the fat and bend film. The present SWCNTs based sensors could potentially be used to develop low cost, flexible, foldable and disposable sensor system for the monitoring of toxic gases like ammonia in environment.
关键词： functionalized SWCNTs,ammonia sensor,Flexible gas sensor,room temperature,gas sensor
更新于2025-09-23 15:22:29
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Development of the readout system for a time projection chamber prototype
摘要： A new GEM-TPC prototype with a laser calibration system is being designed to study the key issues of high-precision track detection whose aimed spatial resolution is better than 100 μm. Meanwhile, a readout system with scalability for the TPC is also being developed. Design of the readout system is based on the architecture of front-end ASICs and commercial ADCs for its advantages at high count rates. Given the requirement of several hundred channels, the system is composed of multiple front-end cards and DAQ boards. The DAQ boards are daisy-chained via bidirectional optical fibers, which transmit clock, trigger, data and control signals simultaneously. To achieve timing synchronization, the GigaBit Transceiver (GBT) firmware is employed to ensure fixed latency between the boards. This paper is focused on the design and setup of the DAQ system, including clock structure, trigger alignment, high-speed data acquisition, etc. The DAQ system consisting of 512 channels has been built, and tests have proved that the entire system works correctly and meets the expected requirements.
关键词： Trigger concepts and systems (hardware and software),Electronic detector readout concepts (gas, liquid),Modular electronics,Data acquisition concepts
更新于2025-09-23 15:22:29
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QEPAS Sensor for Simultaneous Measurements of H <sub/>2</sub> O, CH <sub/>4</sub> , and C <sub/>2</sub> H <sub/>2</sub> Using Different QTFs
摘要： A multi-gas quartz enhanced photoacoustic spectroscopy (QEPAS) sensor based on three quartz tuning forks (QTFs) with different response frequencies for trace gas detection was proposed and experimentally demonstrated. Three near-infrared DFB lasers are used to monitor water vapor, methane, and acetylene in the parts per million range. The sensor system was first evaluated for individual H2O, CH4, and C2H2 detection, respectively. Subsequently, the sensor system was evaluated for simultaneous H2O, CH4, and C2H2 detection. Finally, trace gas measurements have been assessed and minimum detection limit (MDL) of 1.3 ppmv at 1368.597 nm for H2O, 79 ppmv at 1653.722 nm for CH4, and 5 ppmv at 1532.83 nm for C2H2 have been demonstrated. The continuous monitoring of H2O, CH4, and C2H2 concentration levels for >3 h indicated the stability of the reported multi-gas QEPAS sensor system.
关键词： Gas detection,QEPAS sensor,multi-component
更新于2025-09-23 15:22:29
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Nickel Doping on Cobalt Oxide Thin Film Using by Sputtering Process-a Route for Surface Modification for p-type Metal Oxide Gas Sensors
摘要： This study proposes a route for surface modification for p-type cobalt oxide-based gas sensors. We deposit a thin layer of Ni on the Co oxide film by sputtering process and annealed at 350 °C for 15 min in air, which changes a typical sputtered film surface into one interlaced with a high density of hemispherical nanoparticles. Our in-depth materials characterization using transmission electron microscopy discloses that the microstructure evolution is the result of an extensive inter-diffusion of Co and Ni, and that the nanoparticles are nickel oxide dissolving some Co. Sensor performance measurement unfolds that the surface modification results in a significant sensitivity enhancement, nearly 200% increase for toluene (at 250 °C) and CO (at 200 °C) gases in comparison with the undoped samples.
关键词： Toluene,Co oxide thin film,Ni-doped,Gas sensor,RF sputtering,CO
更新于2025-09-23 15:22:29
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Highly Stable and Ultrafast Hydrogen Gas Sensor Based on 15 nm Nanogaps Switching in a Palladium-Gold Nanoribbons Array
摘要： Palladium (Pd) nanogap hydrogen gas (H2) sensors based on the large volume expansion of β phase palladium hydride (β-PdH) are highly promising, owing to their fast and accurate sensing capability at room temperature in air. However, such sensors do not work well at H2 concentrations below 1%. At such low H2 concentrations, Pd exists as α-PdH, which has a slow and insufficient volume expansion and cannot completely close nanogaps. Furthermore, the lattice strains induced from the phase transition (α-PdH → β-PdH) behavior degrade the stable and repeatable long-term sensing capability. Here, these issues are resolved by fabricating an array of periodically aligned alloyed palladium–gold nanoribbons (PdAu NRB) with uniform 15 nm nanogaps. The PdAu NRB sensor enables highly stable and ultrafast H2 sensing at the full detection range of H2 concentrations from 0.005% to 10% along with the excellent limit of detection (≈0.0027%), which is sufficiently maintained even after seven months of storage in ambient atmosphere. These breakthrough results will pave the way for developing a practical high-performance H2 sensor chip in the future hydrogen era.
关键词： palladium nanogap,nanoribbon,hydrogen gas sensors,polystyrene thermal shrinkage
更新于2025-09-23 15:22:29
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Sub-ppm acetone gas sensing properties of free-standing ZnO nanorods
摘要： In this paper, ZnO nanorods were synthesized by low cost and simple wet chemical method and used as a highly sensitive acetone gas sensor with detection limit as low as 25 ppb which makes the sensor a promising choice for various applications. The fabricated sensor showed a response value of 1.75 towards 25 ppb acetone at optimum working temperature of 320 °C with a response time of 30s. However, the sensor showed response value of 60 towards 50 ppm acetone with a response time of 15 s. The grown ZnO nanorods were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD) for morphology and crystallinity characterization. According to the SEM images, freestanding nanorods with mean diameter of 80 nm and mean length greater than 1.5um were obtained with highly preferential c-axis orientation.
关键词： Sub-ppm sensing,Gas sensor,Acetone,ZnO Nanorods,Hydrothermal
更新于2025-09-23 15:22:29
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Effect of defects in TiO2 nanoplates with exposed {001} facets on the gas sensing properties
摘要： The exposed crystal facet of TiO2 is a crucial factor influencing the gas sensing properties. TiO2 with high-energy {001} crystal facets that have higher surface energy and reactivity is expected to exhibit excellent gas-sensing properties. In this paper, TiO2 nanoplates with defective {001} facets were synthesized by chemical etching via one-step hydrothermal method. We carefully explored the gas-sensing performance of TiO2 nanoplates with defective and complete {001} facets towards acetone. The results show that the sensing response of TiO2 nanoplates with complete {001} facets is 70% higher than that of defective TiO2 nanoplates, which proves that the {001} facets plays a vital role in improving the gas sensing performance of TiO2. It is speculated that the poor gas sensitivity of defective TiO2 can be contributed to fewer adsorption sites and blocked electron transfer. This work presents a more direct evidence for explaining the important role of the complete {001} crystal facets in high sensitivity of TiO2 and also provides a new insight for preparing high sensitivity sensing materials.
关键词： TiO2 nanoplates,Defective,Acetone,{001} facets,Gas sensing
更新于2025-09-23 15:22:29
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Evaluation of Low-Temperature Saturation Velocity in β -(Al?Ga???)?O?/Ga?O? Modulation-Doped Field-Effect Transistors
摘要： We report on the high-field transport characteristics and saturation velocity in a modulation-doped β-(AlxGa1?x)2O3/Ga2O3 heterostructure. The formation of a 2-D electron gas (2DEG) in the modulation-doped structure was confirmed from the Hall measurements, and the 2DEG channel mobility increased from 143 cm2/V·s at room temperature to 1520 cm2/V·s at 50 K. The high electron mobility at 50 K made it feasible to achieve velocity saturation inside the channel. The saturation velocity was estimated based on both pulsed current–voltage measurements and small-signal radio frequency (RF) measurements. The measured velocity–field profile suggested a saturation velocity above 1.1 × 107 cm/s at 50 K. The small-signal RF characteristics were measured for the fabricated modulation-doped field-effect transistors with a Pt-based Schottky contact. The current gain cutoff frequency (ft) and maximum oscillation frequency (fmax) showed significant increases from 4.0/11.8 GHz at room temperature to 17.4/40.8 GHz at 50 K for the device with gate length of LG = 0.61 μm. The analysis of the low temperature ft based on device simulations indicated a peak velocity of 1.2 × 107 cm/s. The three-terminal off-state breakdown measurement further suggested an average breakdown field of 3.22 MV/cm. The high saturation velocity and high breakdown field in β-Ga2O3 make it a promising candidate for high-power and high-frequency device applications.
关键词： mobility,β-Ga2O3,modulation-doped field-effect transistor (MODFET),2-D electron gas (2DEG),saturation velocity,high breakdown field
更新于2025-09-23 15:22:29