This paper evaluates the effect of two kinds of recycled coarse aggregate with different sized particles on the performance of concrete. The test program is introduced, which investigated the compressive strength, axial compressive strength, the mass loss rate of concrete specimens after a freeze-thaw cycle and dynamic elasticity modulus change. The results show that the mechanical properties of the concrete decreased when it was prepared with recycled aggregate having the same size as that of the natural aggregates. The strength of the concrete with large-size recycled aggregate increased, and then decreased as the blend proportion rose above 50%. The strength of concrete incorporating oversized recycled aggregates exhibited a trend of rising and then falling with increasing mixing ratio. The 28-day compressive strength reached 45Mpa when the mixing amount was 50%. The durability of the large-size recycled aggregate was also found to improve compared with the freezing and thawing cycle experiments. These results provide a reference for research on the performance of recycled aggregate concrete.
Aluminum nitride (AlN) provides excellent thermal conductivity and electrical insulation, making it suitable for semiconductor heater applications. However, its low surface emissivity can lead to thermal energy loss, reducing heater efficiency. To address this issue, black AlN - obtained by doping with carbon and other impurities to enhance the surface emissivity - has recently been applied in various fields. In this study, black AlN was fabricated by adding TiO2 to AlN, and its densification behavior and electrical properties were evaluated to assess the feasibility of its use as a heater material for semiconductor photolithography. The sinterability of black AlN was improved by optimizing the granulation and forming conditions, with a particular focus on the heat treatment parameters that affect material properties such as color. Consequently, a black AlN heater material with a sintered density of 3.33 g/cm3, thermal conductivity of 162.7 W/m・K, and thermal diffusivity of 64.22 mm2/s was fabricated by optimizing the processing variables.
The catalyst materials 0N-Cu-MOF, 1N-Cu-MOF, and 2N-Cu-MOF were successfully synthesized usinga solvothermal method, and using different concentrations of nitrogen-modified Cu organic frameworks (xN-Cu-MOF). Characterizations using X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) surface area analysis showed that 1N-Cu-MOF had the largest SSA and pore size among the three materials synthesized. 1N-Cu-MOF exhibited the largest pore size and specific surface area among the three materials, which had a decisive effect on CO2 reduction. In addition, stability and CO2 reduction reaction (CO2RR) activity were evaluated by linear sweep voltmeter, cyclic voltmeter, electrochemical impedance spectroscopy, and time flow tests. Faradaic efficiency (FE) was determined by product analysis. Among the three catalyst materials, 1N-Cu-MOF showed the best catalytic performance at 50 mA・cm-2 (maximum current density). The charge transfer resistance was 8.23 Ω, the average current density was 19.9 mA・cm-2, and the FE of methane (CH4) production showed a high efficiency of 70.45 % when tested for 12 h at an overpotential of -0.35 V (to-RHE).
Hydrogen has a wide flammability range and rapidly diffuses in air, making precision detection technology essential to prevent explosion risks and ensure system safety as the adoption of hydrogen infrastructure expands. Polymer materials are employed in such infrastructure to seal high-pressure hydrogen, and reliable measurement techniques capable of quantifying trace amounts of hydrogen permeating or leaking through these materials is necessary. In this study, a hydrogen quantification system combining volumetric analysis with image analysis was utilized to evaluate the hydrogen uptake and diffusivity of HDPE (high-density polyethylene), NBR (nitrile butadiene rubber), and EPDM (ethylene propylene diene monomer) under high-pressure conditions. The results indicated that HDPE and NBR samples containing silica filler exhibited hydrogen uptake behavior consistent with Henry’s law, while EPDM samples with carbon black filler demonstrated additional hydrogen adsorption on the carbon black surface. These research results provide a foundation for more precisely evaluating the permeation and leakage behavior of polymers in high-pressure hydrogen environments, and are expected to contribute to the safe and efficient development of hydrogen infrastructure.
In this study, anatase TiO2 nano sol (TNS, TiO2 Nano-Sol) was synthesized via a simple sol-gel method under low-temperature and ambient pressure conditions using TiOCl2 as a precursor. The structural and photocatalytic properties of the TNS were systematically investigated as a function of reaction time. X-ray diffraction (XRD) confirmed the formation of the anatase crystal structure as the reaction time increased, while field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) analyses verified the uniform formation of fine anatase nanoparticles, averaging less than 10 nm in size. The synthesized TNS sol enabled the fabrication of transparent TiO2 coatings that retained over 76 % transmittance in the visible light range, as verified by UV-Vis spectroscopy. Photocatalytic activity was evaluated through methylene blue (MB) degradation experiments, which showed that degradation efficiency was enhanced with longer reaction times. Notably, the TNS-48 exhibited superior photocatalytic degradation performance, being approximately three times higher than that of TNS-1 and about twice that of the commercial P25. This study demonstrates that the TNS sol synthesized through a simple sol-gel process can achieve high transparency and excellent photocatalytic properties without requiring hightemperature and high-pressure synthesis. It is expected to be applicable in various photocatalytic fields, such as functional coatings and electrode materials.
Researchers have made significant strides in developing high-performance anode-supported tubular solid oxide fuel cells (SOFCs). These cells feature a thin, dense electrolyte made of Ba(Zr0.1Ce0.7Y0.2)O3-δ (BZCY). The fabrication process involved several key steps. First, fine BZCY powder was prepared using a co-precipitation method. Next, Ni-BZCY anode tubes were created via an extrusion process, boasting a 34 % porosity and an average pore size of 0.381 μm. To optimize cell performance, a Ni-BZCY/BZCY nanocomposite slurry was applied as an anode functional layer (AFL) using a dip-coating method. The BZCY electrolyte itself was then coated with a vacuum slurry coating, and finally, an LSCF-BZCY cathode was added, prepared with dip-coating methods. Impedance analysis, conducted under open-circuit conditions at 700 °C, revealed impressive electrical characteristics. The BZCY electrolyte showed an ohmic resistance of approximately 0.79 Ωcm-2 and a very low polarization resistance of about 0.036 Ωcm-2. When tested in a humidified hydrogen atmosphere (3 % H2O) at temperatures ranging from 600 °C to 700 °C, these tubular BZCY cells delivered outstanding power output. Specifically, they achieved a remarkable maximum power density of roughly 0.51 Wcm-2 at 700 °C. This research highlights the potential of these advanced tubular solid oxide fuel cells based on the BZCY as a proton conductor for efficient energy conversion.
This study prepared a (TiO2-CeO2)/Sr4Al14O25: Eu2+,Dy3+ heterojunction photocatalyst by coating (TiO2-CeO2) nanoparticles on a Sr4Al14O25:Eu,Dy phosphor substrate using a hydrothermal reaction method. The fabricated (TiO2- CeO2)/Sr4Al14O25: Eu2+,Dy3+ composites were characterized with X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photo electron spectroscopy (XPS), UV-visible diffuse reflectance spectroscopy (UV/Vis DRS), Brunauer-Emmett-Teller (BET), and Raman spectroscopy. The photocatalytic performance of the (TiO2-CeO2)/Sr4Al14O25: Eu2+,Dy3+ composites was investigated through the decomposition of toluene gas for various ratios of TiO2 to CeO2 (3:7, 5:5, and 7:3) and heat treatment ranging from 300 to 700 °C. The coupling between (TiO2-CeO2) and the highly persistent Sr4Al14O25:Eu2+,Dy3+ phosphor reduced the energy band gap and enhanced visible light absorption. In particular, the 5:5 ratio of TiO2 to CeO2 on Sr4Al14O25:Eu2+,Dy3+ showed excellent photocatalytic performance, decomposing over 85 % of the toluene gas within 150 min even under visible-light irradiation. The results suggest that the CeO2 particles might increase the specific surface area, and effectively suppress the recombination of electrons and holes generated from TiO2, thereby enhancing the photocatalytic reactivity.