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oe1(光电查) - 科学论文

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出版时间
  • 2018
研究主题
  • interdigital resonator
  • microwave gas sensor
  • PSE-coated
应用领域
  • Optoelectronic Information Science and Engineering
机构单位
  • King Mongkut’s University of Technology North Bangkok
  • Rajamangala University of Technology Suvarnabhumi
571 条数据
?? 中文（中国） ▾

  • Gas Breakdown and Discharge Formation in High-Power Impulse Magnetron Sputtering

    摘要： Discharge behaviors of high-power impulse magnetron sputtering with different targets have been investigated. Distinct current–voltage curves and target current waveforms are observed. Breakdown voltage and the maximum target current show a periodic drop with the increase of atomic number in subgroups and periods. The target current density is found to be mainly affected by the secondary electron emission yield. Thus, its magnitude is unable to directly evaluate the ionization degree of sputtered atoms in high-power impulse magnetron sputtering (HiPIMS) process. In this paper, the interactive influence of secondary electron emission, sputter yield, and ionization energy on the ionization degree of sputtered atoms is discussed based on the analysis of the voltage and current characteristics. As a result, targets can be categorized into three sorts according to the ionization degree: 1) low ionization degree targets, such as Ag and C less than 10%; 2) intermediate ionization degree targets like Cr and Cu with 55% and 35%; 3) Ti, Zr, and Mo targets with the second ionization processes. These results provide institutive operation ranges for the state-of-the-art HiPIMS applications.

    关键词： optical emission spectroscopy (OES),ionization degree,Current waveform,gas breakdown,high-power impulse magnetron sputtering (HiPIMS)

    更新于2025-09-23 15:22:29

  • Morphology Controllable Synthesis of Hierarchical WO3 Nanostructures and C2H2 Sensing Properties

    摘要： In this paper, we reported the morphology controllable synthesis of hierarchical WO3 nanostructures, i.e. nanorods, nanospheres and nanoflowers, via a facile hydrothermal route. All the obtained WO3 nanostructures were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET), respectively. A possible growth mechanism for the three various nanomaterials was proposed in detail. WO3 based gas sensors were fabricated with the synthesized nanomaterials and the gas sensing performances to acetylene (C2H2), one of the fault characteristic gases dissolved in power transformer oil, were systematically measured. It was found that the sensor based on nanosheet-assembled nanoflowers with largest surface (56.74 m2g-1) exhibits the highest sensing performance including gas response (32.31) and response-recovery time (12 s, 17 s) to 200 ppm C2H2. The results indicate that WO3 sensing materials could be a promising choice for synthesizing high-performance C2H2 sensors for the judgement of the early latent faults of the oil immersed transformer.

    关键词： Hierarchical WO3,Gas sensors,Growth mechanism,C2H2 sensing performances

    更新于2025-09-23 15:22:29

  • Selective Gas Sensor Using Porous Silicon

    摘要： The effect of polar and non-polar vapors, like ethanol, methanol, acetonitrile, chloroform and toluene vapors on porous silicon gas sensor was studied. We demonstrated that the selectivity of a single sensor can be achieved by the impedance measurements within the frequency range 103–105 Hz. It is shown that the capacitance of the structure and its frequency dispersion are different under influence of different gases providing an unique signature of an agent. A set of parameters is proposed in order to numerically characterize the response to different gases. The characteristic time of response to different vapors gives an additional parameter to sense gases selectively.

    关键词： Organic Vapors,Gas Sensor,Porous Silicon,Selectivity

    更新于2025-09-23 15:22:29

  • Properties of Porous Silicon Precipitated with Nickel for Gas Sensors

    摘要： The preparation and properties of modified porous silicon is discussed and a proposal of a sensitive layer for a gas detector is presented. The modification is done by precipitation and electrochemical deposition of nickel. The morphology of sample surfaces is examined by atomic force microscopy and scanning electron microscopy (SEM). SEM-coupled energy dispersive spectroscopy is used to analyse the chemical composition of the samples. Magnetic response is measured with a SQUID magnetometer. Electrochemical impedance spectroscopy is used to study the sensitivity of the samples to isopropanol vapour in the presence of alternating electric current. A series of samples prepared with a higher anodic current density show higher sensitivity to isopropanol vapours in comparison to a lower anodic current.

    关键词： Electrochemical Impedance Spectroscopy,Porous Silicon,Gas Sensors,SQUID,Electroless Nickel Deposition,Atomic Force Microscopy

    更新于2025-09-23 15:22:29

  • Application to Artificial Skin of Double Cone Tube Made of Acrylic Resin Formed by Micro Stereolithography

    摘要： A functional double cone tube (DCT) array with gas trapping and high durability is developed in the application of artificial skin. A stereo-lithography system is employed to fabricate DCT made of acrylic resin. In an aqueous solution, a certain amount of gas can be trapped in the tube due to capillary force balance. Under applying an external load, internal stress is effectively released at the interface between top and base cones. In the tactile sensing investigation, softness and tackiness senses as an artificial skin are felt.

    关键词： Acrylic resin,Gas storage,Double cone tube (DCT),Stress distribution,Artificial skin,Micro stereo-lithography

    更新于2025-09-23 15:22:29

  • Optical, thermal and gas separation properties of acetate-containing copoly(ether-imide)s based on 6FDA and fluorenyl diamines

    摘要： The diamine, 9,9-bis[4-(4-amino-3-hydroxylphenoxy)phenyl]fluorene (BAHPPF) was synthesized by the modified two-step method. Then, a series of acetate-containing copoly(ether-imide)s were prepared by the copolymerization of BAHPPF, 9,9-bis(4-aminophenyl)fluorene (BAF) and 2,20-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) followed by chemical imidization. The structures and properties of the BAHPPF and copoly(ether-imide)s were characterized by nuclear magnetic resonance spectrometer (NMR), Fourier transform infrared spectrometer (FTIR), X-ray diffractometer (XRD), differential scanning calorimeter (DSC), thermogravimetric analyzer (TGA), ultraviolet-visible spectrophotometer (UV-VIS), and tensile testing. Single gas permeation performances of these copoly(ether-imide)s were also studied for five representative gases of interest including H2, O2, N2, CO2, and CH4. The experimental results showed that the copoly(ether-imide)s showed excellent optical properties with high light transmittance above 80.2% at 450 nm. The glass transition temperature of these copolymers were higher than 333°C. Their tensile strength and Young’s module also increased, and the elongation decreased with the decrease of BAHPPF. High gas permeabilities of copoly(ether-imide)s were obtained, and the ideal selectivity of CO2/CH4 was improved due to the introduction of acetate group and flexible ether linkage. These copoly(ether-imide)s could be applied to the field of optics and gas separation.

    关键词： gas separation,acetate-containing,Copoly(ether-imide)s,thermal properties,light-colored and transparent

    更新于2025-09-23 15:22:29

  • Fabrication and characterization of VOC sensor array based on SnO2 and ZnO nanoparticles functionalized by metalloporphyrins

    摘要： A volatile organic compound (VOC) sensor array based on metal oxide nanoparticles (MOX NPs) functionalized by metalloporphyrins (MPPs) was demonstrated. The VOC sensor array was composed of four single sensors based on SnO2 NPs/cobalt-porphyrin, SnO2 NPs/zinc-porphyrin, SnO2 NPs/nickel-porphyrin and ZnO NPs/cobalt-porphyrin. The MOX NP/MPP-based sensors were fabricated by drop-casting the MOX NPs dispersion and MPPs solution onto a MEMS platform. The fabricated sensor successfully detected toluene at a concentration as low as 20 ppb, which is below the limit detection concentration of previously reported porphyrin-based VOC sensor arrays. We also confirmed the selectivity between benzene, toluene, ethylbenzene, and xylene (BTEX) by using principal component analysis in contrast to previous studies on MOX/MPP-based sensor. BTEX was classified from 1 to 9 ppm at a resolution of 2 ppm, and the sensor array showed stable performance even after considerable impact.

    关键词： Gas sensor array,Porphyrin,Principle component analysis,Metal oxide,Volatile organic compound

    更新于2025-09-23 15:22:29

  • Quantifying Double-Layer Potentials at Liquid–Gas Interfaces from Vibrational Sum-Frequency Generation

    摘要： Vibrational sum-frequency generation (SFG) spectroscopy is demonstrated as a fast method to quantify variations of the electric double-layer potential ?0 at liquid?gas interfaces. For this, mixed solutions of nonionic tetraethyleneglycol-monodecylether (C10E4) and cationic hexadecyltrimethylammonium bromide (C16TAB) surfactants were investigated using SFG spectroscopy and a thin-film pressure balance (TFPB). Derjaguin?Landau?Verwey?Overbeek analysis of disjoining pressure isotherms obtained with the TFPB technique provides complementary information on ?0, which we apply to validate the results from SFG spectroscopy. By using a single ?0 value, we can disentangle χ(2) and χ(3) contributions to the O?H stretching modes of interfacial water molecules in the SFG spectra. Having established the latter, we show that unknown double-layer potentials at the liquid?gas interface from solutions with different C16TAB/C10E4 mixing ratios can be obtained from an analysis of SFG spectra and are in excellent agreement with the complementary results from the TFPB technique.

    关键词： disjoining pressure,Vibrational sum-frequency generation,electric double-layer potential,thin-film pressure balance,liquid?gas interfaces,surfactants

    更新于2025-09-23 15:22:29

  • Unusual Electric and Optical Tuning of KTaO <sub/>3</sub> -Based Two-Dimensional Electron Gases with 5d Orbitals

    摘要： Controlling electronic processes in low dimension electron system is centrally important for both fundamental and applied researches. While most of the previous works focused on SrTiO3-based two-dimensional electron gases (2DEGs), here we report on a comprehensive investigation in this regard for amorphous-LaAlO3/KTaO3 2DEGs with the Fermi energy ranging from ~13 meV to ~488 meV. The most important observation is the dramatic variation of the Rashba spin-orbit coupling (SOC) as Fermi energy sweeps through 313 meV: The SOC effective field first jumps and then drops, leading to a cusp of ~2.6 T. Above 313 meV, an additional species of mobile electrons emerges, with a 50-fold enhanced Hall mobility. A relationship between spin relaxation distance and the degree of band filling has been established in a wide range. It indicates that the maximal spin precession length is ~70.1 nm and the maximal Rashba spin splitting energy is ~30 meV. Both values are much larger than the previously reported ones. As evidenced by density functional theory calculation, these unusual phenomena are closely related to the distinct band structure of the 2DEGs composed of 5d electrons. The present work further deepens our understanding of perovskite conducting interfaces, particularly those composed of 5d transition metal oxides.

    关键词： oxide interfaces,spin-orbital coupling,two-dimensional electron gas,optical gating,gating effect

    更新于2025-09-23 15:22:29

  • Liquid crystal nose, chiral case: towards increased selectivity and low detection limits

    摘要： In this paper, we describe a simple prototype of an olfaction system based on chiral liquid crystals (LCs) and suitable for sensing volatile organic compounds (VOCs). The detection of small concentrations of VOCs is based on measuring weak colour fluctuations on the surface of the LC droplet. Detection of larger concentrations is based on measuring colour changes (or shift of the selective reflection band) and isotropisation transition of the whole droplet. Thus, a broad range of VOC concentrations can be detected by this LC nose.

    关键词： gas detection,LC nose,volatile organic compound,olfaction,electronic nose,VOC,liquid crystals,cholesteric

    更新于2025-09-23 15:22:29