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961.
EunGyoung Choi KyoungHo Song SoRa An KwanYoung Lee MinHyeh Youn KiTae Park SoonKwan Jeong HakJoo Kim 《Korean Journal of Chemical Engineering》2018,35(1):73-81
Catalytic conversion of CO2 to methanol is gaining attention as a promising route to using carbon dioxide as a new carbon feedstock. AlOOH supported copper-based methanol synthesis catalyst was investigated for direct hydrogenation of CO2 to methanol. The bare AlOOH catalyst support was found to have increased adsorption capacity of CO2 compared to conventional Al2O3 support by CO2 temperature-programmed desorption (TPD) and FT-IR analysis. The catalytic activity measurement was carried out in a fixed bed reactor at 523 K, 30 atm and GHSV 6,000 hr?1 with the feed gas of CO2/H2 ratio of 1/3. The surface basicity of the AlOOH supported Cu-based catalysts increased linearly according to the amount of AlOOH. The optimum catalyst composition was found to be Cu : Zn : Al=40 : 30 : 30 at%. A decrease of methanol productivity was observed by further increasing the amount of AlOOH due to the limitation of hydrogenation rate on Cu sites. The AlOOH supported catalyst with optimum catalyst compositions was slightly more active than the conventional Al2O3 supported Cu-based catalyst. 相似文献
962.
Junyeong Kim Jeong Yeon Do No-Kuk Park Seung Jong Lee Jin-Pyo Hong Misook Kang 《Korean Journal of Chemical Engineering》2018,35(5):1089-1098
Nano-sized bismuth sulfide (Bi2S3) and titanium dioxide (TiO2) with the orthorhombic and anatase tetragonal structures, respectively, were synthesized for application as catalysts for the reduction of carbon dioxide (CO2) to methane (CH4). Four double-layered dense films were fabricated with different coating sequences—TiO2 (bottom layer)/Bi2S3 (top layer), Bi2S3/TiO2, TiO2/Bi2S3: TiO2 (1 : 1) mix, and Bi2S3: TiO2 (1 : 1) mix/Bi2S3: TiO2 (1 : 1) mix—and applied to the photoreduction of CO2 to CH4; the catalytic activity of the fabricated films was compared to that of the pure TiO2/TiO2 and Bi2S3/Bi2S3 doubled-layered films. The TiO2/Bi2S3 double-layered film exhibited superior photocatalytic behavior, and higher CH4 production was obtained with the TiO2/Bi2S3 double-layered film than with the other films. A model of the mechanism underlying the enhanced photoactivity of the TiO2/Bi2S3 double-layered film was proposed, and it was attributed in effective charge separation. 相似文献
963.
So Ra An Kyoung Ho Song Kwan Young Lee Ki Tae Park Soon Kwan Jeong Hak Joo Kim 《Korean Journal of Chemical Engineering》2018,35(9):1807-1814
New post-treatment process for marine diesel engine exhaust emissions was proposed by combining NO oxidation and wet scrubbing technology for the simultaneous removal of SOX, NOX and PM. NO, insoluble in aqueous scrubbing absorbent, is preferentially oxidized to NO2, which then turns fully soluble in it. Fe substituted LaCo1-xFexO3 perovskite catalysts were developed for NO oxidation to NO2. The catalysts were prepared by co-precipitation method and analyzed with XRD, XRF, BET, FT-IR, NO-TPD and XPS techniques. Crystal structure change from rhombohedral to orthorhombic was observed with the increased amount of Fe substituted in the B site of the perovskite by XRD analysis. From FT-IR and NO-TPD analysis, nitrate on perovskite species was found to be the active species for NO oxidation. Quantitative analysis was performed within the prepared catalysts. Catalytic activity was measured using a packed bed reactor operated at 150–400 °C, atmospheric pressure and with gas hourly space velocity (GHSV) of 20,000 h-1 using a simulated exhaust gas composed of NO 400 ppm, O2 10% balanced with N2. Formation of Fe4+ cation enhanced the redox property as well as the mobility of the lattice oxygen present in the perovskite catalysts, confirmed by XPS analysis. Reaction mechanism of NO oxidation on Fe substituted LaCo1-xFexO3 was discussed based on Mars-van Krevelen mechanism. 相似文献
964.
High‐Performance Triboelectric Nanogenerators Based on Electrospun Polyvinylidene Fluoride–Silver Nanowire Composite Nanofibers 下载免费PDF全文
Siuk Cheon Hyungseok Kang Han Kim Youngin Son Jun Young Lee Hyeon‐Jin Shin Sang‐Woo Kim Jeong Ho Cho 《Advanced functional materials》2018,28(2)
The preparation of ferroelectric polymer–metallic nanowire composite nanofiber triboelectric layers is described for use in high‐performance triboelectric nanogenerators (TENGs). The electrospun polyvinylidene fluoride (PVDF)–silver nanowire (AgNW) composite and nylon nanofibers are utilized in the TENGs as the top and bottom triboelectric layers, respectively. The electrospinning process facilitates uniaxial stretching of the polymer chains, which enhances the formation of the highly oriented crystalline β‐phase that forms the most polar crystalline phase of PVDF. The addition of AgNWs further promotes the β‐phase crystal formation by introducing electrostatic interactions between the surface charges of the nanowires and the dipoles of the PVDF chains. The extent of β‐phase formation and the resulting variations in the surface charge potential upon the addition of nanowires are systematically analyzed using X‐ray diffraction (XRD) and Kelvin probe force microscopy techniques. The ability of trapping the induced tribocharges increases upon the addition of nanowires to the PVDF matrix. The enhanced surface charge potential and the charge trapping capabilities of the PVDF–AgNW composite nanofibers significantly enhance the TENG output performances. Finally, the mechanical stability of the electrospun nanofibers is dramatically enhanced while maintaining the TENG performances by applying thermal welding near the melting temperature of PVDF. 相似文献
965.
Jong‐Hoon Lee Song Yi Jeong Geunjin Kim Byoungwook Park Seyoung Kee Bongseong Kim Kwanghee Lee 《Advanced functional materials》2018,28(10)
The collection efficiency of photogenerated charges in polymer solar cells (PSCs) is strongly influenced by the built‐in field (Ein) that develops across the photoactive materials. Here, by investigating the Ein‐development regimes in PSCs by introducing two types of interlayers, electric dipole layers (EDLs) and charge transport layers (CTLs), the device architecture is optimized to result in a larger Ein. By incorporating a pair of EDLs on both sides of the photoactive layer, the Ein is modulated by shifting the vacuum energy at each metal–semiconductor interface, providing a larger Ein than that in conventional PSCs using typical CTLs, such as metal oxides and/or conducting polymers. These devices using paired EDLs exhibit an average PCE of 9.8%, which far surpasses the average PCE of ≈8.5% for paired CTLs. 相似文献
966.
Biomimetic Chitin–Silk Hybrids: An Optically Transparent Structural Platform for Wearable Devices and Advanced Electronics 下载免费PDF全文
Moo‐Seok Hong Gwang‐Mun Choi Joohee Kim Jiuk Jang Byeongwook Choi Joong‐Kwon Kim Seunghwan Jeong Seongmin Leem Hee‐Young Kwon Hyun‐Bin Hwang Hyeon‐Gyun Im Jang‐Ung Park Byeong‐Soo Bae Jungho Jin 《Advanced functional materials》2018,28(24)
The cuticles of insects and marine crustaceans are fascinating models for man‐made advanced functional composites. The excellent mechanical properties of these biological structures rest on the exquisite self‐assembly of natural ingredients, such as biominerals, polysaccharides, and proteins. Among them, the two commonly found building blocks in the model biocomposites are chitin nanofibers and silk‐like proteins with β‐sheet structure. Despite being wholly organic, the chitinous protein complex plays a key role for the biocomposites by contributing to the overall mechanical robustness and structural integrity. Moreover, the chitinous protein complex alone without biominerals is optically transparent (e.g., dragonfly wings), thereby making it a brilliant model material system for engineering applications where optical transparency is essentially required. Here, inspired by the chitinous protein complex of arthropods cuticles, an optically transparent biomimetic composite that hybridizes chitin nanofibers and silk fibroin (β‐sheet) is introduced, and its potential as a biocompatible structural platform for emerging wearable devices (e.g., smart contact lenses) and advanced displays (e.g., transparent plastic cover window) is demonstrated. 相似文献
967.
Microstructure Controlled Porous Silicon Particles as a High Capacity Lithium Storage Material via Dual Step Pore Engineering 下载免费PDF全文
Myungbeom Sohn Dong Geun Lee Hyeong‐Il Park Cheolho Park Jeong‐Hee Choi Hansu Kim 《Advanced functional materials》2018,28(23)
To overcome the lithium storage barriers of current lithium‐ion batteries, it is imperative that conventional low capacity graphite anodes be replaced with other higher capacity anode materials. Silicon is a promising alternative anode material due to its huge energy densities; however, its lithium‐concentration‐dependent volumetric changes can induce severely adverse effects that lead to drastic degradations in capacity during cycling. The dealloying of Si–metal alloys is recently suggested as a scalable approach to fabricate high‐performance porous Si anode materials. Herein, a microstructure controlled porous Si is developed by the dealloying in conjunction with wet alkaline chemical etching. The resulting 3D networked structure enables enhancement in lithium storage properties when the Si‐based material is applied not only as a single active material but also in a graphite‐blended electrode. 相似文献
968.
Role of Nd3+ ions on the nucleation and growth of PbS quantum dots (QDs) in silicate glasses 下载免费PDF全文
Won Ji Park Min Gyu Kim Ju Eun Kim Jing Wang Ho Jeong Lee Chan Gyung Park Jong Heo 《Journal of the American Ceramic Society》2017,100(7):2879-2884
The influence of Nd2O3 addition on the precipitation kinetics of lead chalcogenide (PbS) quantum dots (QDs) in silicate glasses was investigated. Energy dispersive X‐ray spectroscopy (EDS) indicated that the Nd3+ ions are preferentially located inside the PbS QDs rather than in the glass matrix. Changes in diameter (D) of PbS QDs exhibited smaller time dependencies (i.e., D≈t0.270‐0.286) than that predicted by the classical Lifshitz–Slyozov–Wagner (LSW) theory. This is due to the limited concentrations of Pb2+ and S2? ions and the large diffusion distance inside the glass matrix. In addition, extended X‐ray absorption fine structure (EXAFS) results indicated that the formation of PbS QDs was retarded due to the presence of Nd2O3 in the glasses, as the large NdOx polyhedra interrupt the diffusion of Pb2+ and S2? ions. We believe that these Nd3+ ions are primarily located in PbS QDs in the form of Nd–O clusters, and that the PbS QDs are built on top of these clusters. 相似文献
969.
A novel Eu3+‐ and self‐activated vanadate phosphor of Ca4La(VO4)3O with oxyvanadate apatite structure 下载免费PDF全文
Ruijin Yu Jung Hyun Jeong Yin‐Feng Wang 《Journal of the American Ceramic Society》2017,100(12):5649-5658
Pure and Eu3+‐activated Ca4La(VO4)3O phosphors were prepared via three‐step solid‐phase synthesis. The phase formation and structure were investigated by X‐ray diffraction (XRD) with Rietveld refinements. All the samples crystallized in an apatite‐type structure. The morphological properties were measured via by SEM and EDS measurements. Ca4La(VO4)3O is a new vanadate optical material with a direct band feature and a band energy of 3.1 eV. The undoped Ca4La(VO4)3O phosphor presents self‐activated yellow luminescence from 400 nm to 750 nm with a maximum wavelength of 525 nm originating from VO4 groups. Luminescence characteristics of Ca4La(VO4)3O indicate that the phosphor is not sufficient for practical applications. In Eu3+‐activated Ca4La(VO4)3O, there is an efficient energy transfer from VO4 to Eu3+ ions. The luminescence spectra, concentration quenching, decay curves, color chromaticity, and quantum efficiencies (QE) of Ca4La(VO4)3O:Eu3+ were investigated. The phosphor presents optimal Eu3+ doping concentration of about 20 mol%. The dominant red emission in Ca4La(VO4)3O:Eu3+ is 615 nm from electronic 5D0→7F2 dipole transitions. The quantum efficiency and the luminescence stability of the pure and Eu‐activated Ca4La(VO4)3O were reported. The luminescence was discussed on the structural characteristics. 相似文献
970.
Sehwan Song Jiwoong Kim Dooyong Lee Jisung Lee Taewon Min Jong‐Ah Chae Jong‐Seong Bae Jaekwang Lee Jeong‐Soo Lee Sungkyun Park 《Journal of the American Ceramic Society》2017,100(9):3928-3934
The structural, electrical, and chemical properties of Sn‐doped Fe2O3 powders were investigated. Various quantities of Sn‐doped Fe2O3 powders were synthesized using solid‐state reactions. Rietveld analysis for the powders that were doped below 2% revealed a phase‐pure Sn‐doped Fe2O3 structure (i.e., identical to Fe2O3 structure). Alternatively, the analysis for the powders that were doped more than 3% exhibited secondary phase. The unit cell volume and electrical conductivity of the phase‐pure samples increased with an increase in the doping concentration. X‐ray photoelectron spectroscopy measurements showed an increased Fe2+ state with the increase in Sn doping concentration. Therefore, the improved electrical conductivity and unit cell volume with the increase in doping concentration of the phase‐pure powders might be related to the increased Fe2+ state. 相似文献