• Title/Summary/Keyword: Photocatalytic

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Durability and mechanical performance in activated hwangtoh-based composite for NOx reduction

  • Kim, Hyeok-Jung;Park, Jang-Hyun;Yoon, Yong-Sik;Kwon, Seung-Jun
    • Advances in concrete construction
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    • v.11 no.4
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    • pp.307-314
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    • 2021
  • Activated hwangtoh (ACT) is a natural resource abundant in South Korea, approximately 15.0% of soil. It is an efficient mineral admixture that has activated pozzolanic properties through high-temperature heating and rapid cooling. The purpose of this study is to improve a curb mixture that can reduce NOx outside and investigate durability performance. To this end, mortar curb specimens were manufactured by replacing OPC with ACT. The ACT substitution ratios of 0.0, 10.0, and 25.0% were considered, and mechanical and durability tests on the curb specimens were conducted at 28 and 91 days of age. Steam curing was carried out for three days for the production of curbs, which was very effective to strength development at early ages. The reduction in strength at early ages could be compensated through this process, and no significant performance degradation was evaluated in the tests on chloride attack, carbonation, and freezing and thawing. The mortar curb with an ACT of 10.0~25.0% replacement ratio exhibited clear NOx reduction through photocatalytic (TiO2) treatment. This is due to the increase in physical absorption through surface absorption and the photocatalyst-containing TiO2 coating. In this study, the reasonable range of the ACT replacement ratio for NOx reduction was quantitatively evaluated through a comprehensive analysis of each test.

Tuning of Electro-optical Properties of Nano-structured SnO2:Ga Powders in a Micro Drop Fluidized Reactor

  • Lim, Dae Ho;Yang, Si Woo;Yoo, Dong June;Lee, Chan Gi;Kang, Yong
    • Korean Chemical Engineering Research
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    • v.57 no.2
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    • pp.259-266
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    • 2019
  • Tuning of electro-optical properties of nano-structured $SnO_2:Ga$ powders in a micro drop fluidized reactor (MDFR) was highly effective to enhance the activities of powders to be used as sensor materials. The tuning was conducted continuously in a facile one-step process during the formation of powders. The microscopic hydrodynamic forces affected the band gap structure and charge transfer of $SnO_2:Ga$ powders through the oxygen and interfacial tin vacancies by providing plausible pyro-hydraulic conditions, which resulted in the decrease in the electrical resistance of the materials. The analyses of room-temperature photoluminescence (PL) spectra and FT-IR exhibited that the tuning could improve the surface activities of $SnO_2:Ga$ powders by adjusting the excitation as well as separation of electrons and holes, thus maximizing the oxygen vacancies at the surface of the powders. The scheme of photocatalytic mechanism of $SnO_2:Ga$ powders was also discussed.

Indium doping induced defect structure evolution and photocatalytic activity of hydrothermally grown small SnO2 nanoparticles

  • Zeferino, Raul Sanchez;Pal, Umapada;Reues, Ma Eunice De Anda;Rosas, Efrain Rubio
    • Advances in nano research
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    • v.7 no.1
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    • pp.13-24
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    • 2019
  • Well-crystalline $SnO_2$ nanoparticles of 4-5 nm size with different In contents were synthesized by hydrothermal process at relatively low temperature and characterized by transmission electron microscopy (TEM), microRaman spectroscopy and photoluminescence (PL) spectroscopy. Indium incorporation in $SnO_2$ lattice is seen to cause a lattice expansion, increasing the average size of the nanoparticles. The fundamental phonon vibration modes of $SnO_2$ lattice suffer a broadening, and surface modes associated to particle size shift gradually with the increase of In content. Incorporation of In drastically enhances the PL emission of $SnO_2$ nanoparticles associated to deep electronic defect levels. Although In incorporation reduces the band gap energy of $SnO_2$ crystallites only marginally, it affects drastically their dye degradation behaviors under UV illumination. While the UV degradation of methylene blue (MB) by undoped $SnO_2$ nanoparticles occurs through the production of intermediate byproducts such as azure A, azure B, and azure C, direct mineralization of MB takes place for In-doped $SnO_2$ nanoparticles.

Development of air-sterilization purification system of fusion and composite structure using broadband-to-active photocatalyst (광대역대 활성광촉매를 활용한 융·복합 구조 공기살균정화장치 개발)

  • Yoon, Sueng-Bae;Hwang, Yun-Jung;Kim, Seung-Cheon
    • Journal of the Korea Convergence Society
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    • v.10 no.4
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    • pp.147-151
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    • 2019
  • Modern people spend most of their daily lives in their homes, schools, or workplaces, hospitals, shopping malls, subway stations, rooms, and parking lots. According to the survey, air quality management at the multi-use facility is less than 50% satisfied. In this study, a photocatalytic filtration system is developed by utilizing a broadband-to-active photocatalyst that utilizes a media photocatalyst filter that removes airborne germs from indoor air as well as indoor air quality and operates on visible light as well as ultraviolet light.

Analyzing corrosion rates of TiO2 nanotubes/titanium separation passive layer under surface and crystallization changes

  • Torres, I. Zamudio;Dominguez, A. Sosa;Bueno, J.J. Perez;Meas, Y.;Lopez, M.L. Mendoza;Dector, A.
    • Advances in nano research
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    • v.10 no.3
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    • pp.211-219
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    • 2021
  • The evaluation of the corrosion resistance of titanium with a TiO2 nanotubes top layer was carried out (TiO2 NT). These nanostructures were evolved into anatase nanoparticles without heat treatment in an aqueous medium, which is a novel phenomenon. This work analyzes the layer between the nanotube bottom and the substrate, which is thin and still susceptible to corrosion. The bottom of TiO2 nanotubes having Fluor resulting from the synthesis process changed between amorphous to crystalline anatase with a crystallite size of about 4 nm, which influenced the corrosion rates. Four kinds of samples were evaluated. A) NT by Ti anodizing; B) NTSB for Ti plates, either modifying its surface or anodizing the modified surface; C) NT-480 for anodized Ti and heat-treated (480℃) for reaching the anatase phase; D) NTSB-480 for Ti plates, first, modifying its surface using sandblast, after that, anodizing the modified surface, and finally, heat-treated to 480℃ to compare with samples having induced crystallization and passivation. Four electrochemical techniques were used to evaluate the corrosion rates. The surfaces having TiO2 nanotubes with a sandblast pre-treatment had the highest resistance to corrosion.

A Study on the Surface Properties of Polymer Insulators for Improving Electrical Insulation Performance (전기 절연성능 향상을 위한 폴리머 애자의 표면 특성 연구)

  • Park, Yong Seob;Bae, Jae Sung;Hong, Byungyou;Lee, Jae Hyeong
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.34 no.1
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    • pp.63-67
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    • 2021
  • In this paper, we investigated the surface properties of polymer insulators to improve electrical insulation performance. First, after washing the polymer insulator in various ways, its contact angle was increased, thereby improving the hydrophobic properties and electrical insulation properties. In addition, TiO2 thin films, which have been used as a photocatalytic material and have been applied to the polymer insulator surface of to enhance the surface and electrical insulating properties. For the sputtering method, the contact angle after coating the TiO2 thin film increased with increasing RF power, but it was lower compared to that before coating, indicating that the hydrophobic properties of the surface were slightly deteriorated. Consequently, the electrical properties of the polymer-insulating material were maintained or improved after the TiO2 thin-film coating.

CO2 Reduction and C2H4 Production Using Nanostructured Gallium Oxide Photocatalyst (산화갈륨 나노구조 광촉매 특성을 이용한 이산화탄소 저감 및 에틸렌 생성 작용)

  • Seo, Dahee;Ryou, Heejoong;Seo, Jong Hyun;Hwang, Wan Sik
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.35 no.3
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    • pp.308-310
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    • 2022
  • Ultrawide bandgap gallium oxide (Ga2O3) semiconductors are known to have excellent photocatalytic properties due to their high redox potential. In this study, CO2 reduction is demonstrated using nanostructured Ga2O3 photocatalyst under ultraviolet (254 nm) light source conditions. After the CO2 reduction, C2H4 remained as a by-product in this work. Nanostructured Ga2O3 photocatalyst also showed an excellent endurance characteristic. Photogenerated electron-hole pairs boosted the CO2 reduction to C2H4 via nanostructured Ga2O3 photocatalyst, which is attributed to the ultrawide and almost direct bandgap characteristics of the gallium oxide semiconductor. The findings in this work could expedite the realization of CO2 reduction and a simultaneous C2H4 production using a low cost and high performance photocatalyst.

Microwave Assisted Synthesis of Graphene-Bi2MoO6 Nanocomposite as Sono-Photocatalyst

  • Tang, Jia-Yao;Zhu, Lei;Fan, Jia-Yi;Sun, Chen;Oh, Won-Chun
    • Korean Journal of Materials Research
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    • v.32 no.1
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    • pp.1-8
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    • 2022
  • In this investigation, Bi2MoO6 deposited graphene nanocomposite (BMG) was synthesized using a simple microwave assisted hydrothermal synthesis method. The synthesized BMG nanocomposite was characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy with energy dispersive X-ray analysis, and photocurrent analysis. The study revealed that the catalysts prepared have high crystalline nature, enhanced light responsive property, high catalytic activity, and good stability. XRD results of BMG composite exhibit a koechlinite phase of Bi2MoO6. The surface property is shown by SEM and TEM, which confirmed a homogenous composition in the bulk particles of Bi2MoO6 and nanosheets of graphene. The catalytic behavior was investigated by the decomposition of Rhodamine B as a standard dye. The results exhibit excellent yields of product derivatives at mild conditions under ultrasonic/visible light-medium. Approximately 1.6-times-enhanced sono-photocatalytic activity was observed by introduction of Bi2MoO6 on graphene nanosheet compared with control sample P25 during 50 min test.

Comparative Study of Undoped and Nickel-Doped Molybdenum Oxide Photoanodes for PEC Water Splitting

  • Garcia-Garcia, Matias
    • Journal of Electrochemical Science and Technology
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    • v.13 no.3
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    • pp.377-389
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    • 2022
  • The current global energy supply depends heavily on fossil fuels. This makes technology such as direct water splitting from harvesting solar energy in photoelectrochemical (PEC) systems potentially attractive due to its a promising route for environmentally benign hydrogen production. In this study, undoped and nickel-doped molybdenum oxide photoanodes (called photoanodes S1 and S2 respectively) were synthesized through electrodeposition by applying -1.377 V vs Ag/AgCl (3 M KCl) for 3 hours on an FTO-coated glass substrate immersed in molibdatecitrate aqueous solutions at pH 9. Scanning electron microscopy (SEM), atomic force microscopy (AFM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) were used for microstructural and compositional characterizations of the photoanodes. In addition, the optical and photoelectrochemical characterizations of these photoanodes were performed by UV-Visible spectroscopy, and linear scanning voltammetry (LSV) respectively. The results showed that all the photoanodes produced exhibit conductivity and catalytic properties that make them attractive for water splitting application in a photoelectrochemical cell. In this context, the photoanode S2 exhibited better photocatalytic activity than the photoanode S1. In addition, photoanode S2 had the lowest optical band-gap energy value (2.58 eV), which would allow better utilization of the solar spectrum.

Physical Propertise of Non-Cement Matrix with Red Mud (레드머드를 혼입한 무시멘트 경화체의 물리적 특성)

  • Kwon, Hyeong-Soon;Lee, Sang-Soo
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2023.05a
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    • pp.93-94
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    • 2023
  • Through the industrial revolution that began in the 18th century, the amount of carbon dioxide in the atmosphere increased rapidly as humans used fossil energy such as coal and oil as fuel for steam engines and factory machines. The amount of carbon dioxide emitted while producing cement, the main material of concrete used in construction, is large enough to account for 5-8% of the world's carbon dioxide emissions. In this study, Non cement-based matrix were used to reduce carbon dioxide emissions from cement production. Red mud is an industrial by-product generated in the manufacturing process of aluminum hydroxide using bauxite, and more than 120 million tons are produced worldwide. In addition, red mud is a porous material that can be physically adsorbed, and causes a photocatalytic reaction of TiO2 to remove harmful substances such as nitrogen oxide formaldehyde in the air and chemically adsorbs ammonia and hydrogen sulfide. Therefore, this study aims to examine the physical properties of the matrix by mixing red mud, an industrial by-product with good adsorption performance, into the Non cement-based matrix.

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