• Research Paper

    Facile Synthesis of WCu-C/N for Effective Catalyst toward Electrochemical Reduction of CO2 to CO
    Kai Chen, Zeda Meng, Yao Liu, Yilei Sun, Yuan Liang, Won-Chun Oh
    Among the products of the electrocatalytic reduction of carbon dioxide (CO2RR), CO is currently the most valuable product for industrial … + READ MORE
    Among the products of the electrocatalytic reduction of carbon dioxide (CO2RR), CO is currently the most valuable product for industrial applications. However, poor stability is a significant obstacle to CO2RR. Therefore, we synthesized a series of bimetallic organic framework materials containing different ratios of tungsten to copper using a hydrothermal method and used them as precursors. The precursors were then subjected to pyrolysis at 800 °C under argon gas, and the M-N bimetallic sites were formed after 2 h. Loose porous structures favorable for electrocatalytic reactions were finally obtained. The material could operate at lower reduction potentials than existing catalysts and obtained higher Faraday efficiencies than comparable catalysts. Of these, the current density of WCu-C/N (W:Cu = 3:1) could be stabilized at 7.9 mA ‧ cm-2 and the FE of CO reached 94 % at a hydrogen electrode potential of -0.6 V (V vs. RHE). The novel materials made with a two-step process helped to improve the stability and selectivity of the electrocatalytic reduction of CO2 to CO, which will help to promote the commercial application of this technology. - COLLAPSE
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    27 September 2024

  • Research Paper

    Enhanced Piezoelectric Degradation of Tetracycline Using Single-Atom Cu Anchored on t-BaTiO3
    Shu Ye, Jing Cheng, Zeda Meng, Won-Chun Oh
    Hydrothermal and ultrasonic processes were used in this study to synthesize a single-atom Cu anchored on t-BaTiO3. The resulting material … + READ MORE
    Hydrothermal and ultrasonic processes were used in this study to synthesize a single-atom Cu anchored on t-BaTiO3. The resulting material effectively employs vibration energy for the piezoelectric (PE) catalytic degradation of pollutants. The phase and microstructure of the sample were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM), and it was found that the sample had a tetragonal perovskite structure with uniform grain size. The nanomaterial achieved a considerable increase in tetracycline degradation rate (approximately 95 % within 7 h) when subjected to mechanical vibration. In contrast, pure BaTiO3 demonstrated a degradation rate of 56.7 %. A significant number of piezo-induced negative charge carriers, electrons, can leak out to the Cu-doped BaTiO3 interface due to Cu’s exceptional conductivity. As a result, a single-atom Cu catalyst can facilitate the separation of these electrons, resulting in synergistic catalysis. By demonstrating a viable approach for improving ultrasonic and PE materials this research highlights the benefits of combining ultrasonic technology and the PE effect. - COLLAPSE
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    27 September 2024

  • Research Paper

    Copper-Titanium Composite Thin Films Grown by Combinatorial Radio Frequency Sputtering for High-Performance Surface Acoustic Wave - Interdigital Transducer Electrodes
    Jae-Cheol Park
    Cu-Ti thin films were fabricated using a combinatorial sputtering system to realize highly sensitive surface acoustic wave (SAW) devices. The Cu-Ti sample … + READ MORE
    Cu-Ti thin films were fabricated using a combinatorial sputtering system to realize highly sensitive surface acoustic wave (SAW) devices. The Cu-Ti sample library was grown with various chemical compositions and electrical resistivity, providing important information for selecting the most suitable materials for SAW devices. Considering that acoustic waves generated from piezoelectric materials are significantly affected by the resistivity and density of interdigital transducer (IDT) electrodes, three types of Cu-Ti thin films with different Cu contents were fabricated. The thickness of the Cu-Ti thin films used in the SAW-IDT electrode was fixed at 150 nm. As the Cu content of the Cu-Ti films was increased from 31.2 to 71.3 at%, the resistivity decreased from 10.5 to 5.8 × 10-5 ohm-cm, and the density increased from 5.5 to 7.3 g/cm3, respectively. A SAW device composed of Cu-Ti IDT electrodes resonated at exactly 143 MHz without frequency shifts, but the full width at half maximum (FWHM) values of the resonant frequency gradually increased as the Cu content increased. This means that although the increase in Cu content in the Cu-Ti thin film helps to improve the electrical properties of the IDT electrode, the increased density of the IDT electrode deteriorates the acoustic performance of SAW devices. - COLLAPSE
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    27 September 2024

  • Research Paper

    Manufacturing and Characterization of Organic-Inorganic Hybrid Coating Film Using Sol-Gel Method

    Sol-Gel법을 이용한 유무기 하이브리드 코팅막 제조 및 특성평가

    Seungwon Cho, Dabin Kim, Ji-Sun Lee, Dongwook Shin, Jinho Kim

    조승원, 김다빈, 이지선, 신동욱, 김진호

    Organic-inorganic hybrid coating films have been used to increase the transmittance and enhance the physical properties of plastic substrates. Sol-gel organic-inorganic thin … + READ MORE
    Organic-inorganic hybrid coating films have been used to increase the transmittance and enhance the physical properties of plastic substrates. Sol-gel organic-inorganic thin films were fabricated on polymethylmethacrylate (PMMA) substrates using a dip coater. Metal alkoxide precursor tetraethylsilicate (TEOS) and alkoxy silanes including decyltrimethoxysilane (DTMS), 3-glycidoxypropyltrimethoxysilane (GPTMS), phenyltrimethoxysilane (PTMS), 3-(trimethoxysilyl)propyl methacrylate (TMSPM) and vinyltrimethoxysilane (VTMS) were used to synthesize sol-gel hybrid coating solutions. Sol-gel synthesis was confirmed by the results of FT-IR. Cross-linking of the Si-O-Si network during synthesis of the sol-gel reaction was confirmed. The effects of each alkoxy silane on the coating film properties were investigated. All of the organic-inorganic hybrid coatings showed improved transmittance of over 90 %. The surface hardness of all coating films on the PMMA substrate was measured to be 4H or higher and the average thickness of the coating films was measured to be about 500 nm. Notably, the TEOS/DTMS coating film showed excellent hydrophobic properties, of about 97°. - COLLAPSE
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    27 September 2024

  • Research Paper

    Thermoelectric Properties of In and Cr Co-Doped BiSbTe3

    In, Cr 동시 도핑에 따른 BiSbTe3 소재의 열전성능지수 증대

    Changwoo Lee, Junsu Kim, Minsu Heo, Sang-il Kim, Hyun-Sik Kim

    이창우, 김준수, 허민수, 김상일, 김현식

    We conducted a study on excessive doping of the Cr and In elements in Bi-Sb-Te materials satisfying the Hume-Rothery rule, and investigated … + READ MORE
    We conducted a study on excessive doping of the Cr and In elements in Bi-Sb-Te materials satisfying the Hume-Rothery rule, and investigated the resulting electrical and thermal properties. From X-ray diffraction (XRD) results, we confirmed the formation of a single phase even with excessive doping. Through analysis of electrical properties, we observed the highest enhancement in electrical characteristics at y = 0.2, suggesting that the appropriate ratio of Bi-Sb significantly influences this enhancement. Using the Callaway-von Baeyer (CvB) model to assess scattering due to point defects, we calculated the experimental point defect scattering factor (ΓCvB.exp), which was notably high due to the substantial differences in volume and atomic weight between the substituted (Cr, In) and original (Bi, Sb) elements. Additionally, we conducted a single parabolic band (SPB) modeling analysis of materials with compositions y = 0.1 and 0.2, where, despite a decrease in density-of-states effective mass (md*) during the enhancement process from y = 0.1 to 0.2, a sharp increase in non-degenerate mobility (μ0) led to an 88 % increase in weighted mobility (μw). Furthermore, analyzing zT with respect to nH revealed a 51 % increase in zT at a composition of y = 0.2. This study confirmed a significant reduction in lattice thermal conductivity with the co-doping strategy, and with further compositional studies to improve electrical properties, we anticipate achieving high zT. - COLLAPSE
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    27 September 2024
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Journal Informaiton Korean Journal of Materials Research Korean Journal of Materials Research
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