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    Sphere-like and flake-like ZnO immobilized on pineapple leaf fibers as easy-to-recover photocatalyst for the degradation of congo red
    (2021-04-01)
    Deebansok, Siraprapha
    ;
    Amornsakchai, Taweechai
    ;
    Sae-Ear, Pannagorn
    ;
    Siriphannon, Punnama
    ;
    Smith, Siwaporn Meejoo
    This work reports immobilization of ZnO photocatalyst on very fine pineapple leaf fiber (PALFs) by a by polyelectrolyte coating method, for the removal of colored pollutants from water stream, allowing for simple recovery after use. It also emphasizes on the effect of defect structure containing in ZnO of hierarchical sphere-like and flake-like morphologies on the color removal performance. The photocatalytic activity of ZnO/PALFs for degradation of congo red (CR) dye was examined under static (dark) and UV/visible irradiation conditions, and effective color removal (>95 %) was achieved, as the results of adsorption and photo-oxidation processes. Results from photoluminescence and X-ray photoelectron spectroscopy suggested that the sphere-like ZnO, bearing zinc vacancies (VZn), zinc interstitials (Zni), singly ionized oxygen vacancies (Vo+), and oxygen vacancies (Vo), has superior photocatalytic activity up to 3.6 times compared to that of flake-like ZnO. With the recyclability up to 3 cycles (>84 % color removal efficiencies), the ZnO immobilized on PALFs have shown a great promise as an easy-to-recover photocatalyst for the removal of colored pollutants in wastewater treatment processes.
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    Defects study by activation energy profile for lowering leakage current in p-n junction
    (2011-01-01)
    Srithanachai, Itsara
    ;
    Ueamanapong, Surada
    ;
    Rujanapich, Poopol
    ;
    Atiwongsangthong, Narin
    ;
    Niemcharoen, Surasak
    Diode leakage current consists of diffusion (I<inf>d</inf>) and generation current (I<inf>g</inf>), which is strongly sensitive to the residual defect density. These defects can be studied by activation energy (E<inf>a</inf>). Therefore, this paper presents a method for calculating activation energy of silicon p-n junctions from volume generation current. It combines temperature-dependent current-voltage (I -V) and capacitance- voltage (C-V) measurements of diodes. The I<inf>g</inf> can be found from the volume leakage current by subtraction of the volume diffusion current, which is calculated while the depletion width is zero. The activation energy (E<inf>a</inf>) is derived from slope of an Arrhenius plot of I<inf>g</inf>. To derive the correct slope the temperature dependence of the depletion width, which is obtained from the corrected volume capacitance has been applied. The E<inf>a</inf> profile below junction has been shown. The lower E<inf>a</inf> value has been found near the junction, which may relate to the junction implantation. © (2011) Trans Tech Publications.
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    Implantation-induced defects analysis base on activation energy diagnostics
    (2009-12-01)
    Pengchan, Weera
    ;
    Phetchakul, Toempong
    ;
    Poyai, Amporn
    Low power consumption device can be realized by low junction leakage current. This leakage current relates to the defects in the depletion region of p-n junction. Among variety process steps, implantation step may generate defects. Therefore, the implantation-induced defects have been studied from the activation energy which has been obtained from the leakage current of p-n junction. The different geometry p-n junctions have been fabricated by a standard CMOS technology. The current-voltage (I-V) and high frequency capacitance-voltage (C-V) characteristics of p-n junctions with temperature dependence have been measured. The electrically active defects from implantation process can be extracted from the junction generation current density versus temperature. Base on this analysis, it will be demonstrated that the implantation-induced defects have been found in p+-n-well more than in n+-psubstrate. Finally, the possible nature of the defect will be discussed.
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    Study on non-destructive evaluation methods for defect pods for green soybean processing by near-infrared spectroscopy
    (2009-08-01)
    Sirisomboon, Panmanas
    ;
    Hashimoto, Yuki
    ;
    Tanaka, Munehiro
    Reflectance spectroscopy ranging from visible light to the near infrared region (600-1100 nm) was investigated for the detection of outer and inner defects of fresh green soybean pods. The outer defect parameters, defined by the processing factory which exports frozen green soybean, were hangnail, thinness, brown spot, insect-eaten, rotten, and worm-eaten, and the inner parameters were those caused by disease, i.e. downy mildew and anthracnose, or by worm inside the pod. Using 802 samples, classification models for each group were identified, based on principle component analysis (PCA). Models were developed using primary spectra and second derivative spectra. The PCA score plots could classify clearly the group affected by downy mildew, those with worm inside, and the worm-eaten, rotten, and thin groups from the good pod group. The primary spectra with or without some kind of pretreatment showed a higher classification performance than the second derivative spectra. The good pod model created by primary spectra correctly classified 77.2% of samples as good pods or defective pods. SIMCA showed obviously better performance than PLS-DA in classification of green soybean pods. The good pod model by SIMCA could 100% self-prediction, though it showed low performance in predicting the other groups. This study provided the information by using NIR spectroscopy in the green soybean grading process in order for the appropriate sorting instruments to be developed. © 2009 Elsevier Ltd. All rights reserved.
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    Extraction of defect in doping silicon wafer by analyzing the lifetime profile method
    (2008-01-01)
    Pengchan, W.
    ;
    Phetchakul, T.
    ;
    Poyai, A.
    The total leakage current in silicon p-n junction diodes compatible with 0.8 μm CMOS technology is investigated. The generation lifetime is a key parameter for the leakage current, which can be obtained from the current-voltage (I-V) and the capacitance-voltage (C-V) characteristics. As will be shown, the electrically active defect from ion implantation process generated in p-n junction can be extracted from the generation current density. © 2008 Trans Tech Publications, Switzerland.