The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Yanfeng Gao - One of the best experts on this subject based on the ideXlab platform.
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Hydrothermal Synthesis of vo2 polymorphs advantages challenges and prospects for the application of energy efficient smart windows
Small, 2017Co-Authors: Shlomo Magdassi, Yanfeng Gao, Yi LongAbstract:Vanadium dioxide (VO2 ) is a widely studied inorganic phase change material, which has a reversible phase transition from semiconducting monoclinic to metallic rutile phase at a critical temperature of τc ≈ 68 °C. The abrupt decrease of infrared transmittance in the metallic phase makes VO2 a potential candidate for thermochromic energy efficient windows to cut down building energy consumption. However, there are three long-standing issues that hindered its application in energy efficient windows: high τc , low luminous transmittance (Tlum ), and undesirable solar modulation ability (ΔTsol ). Many approaches, including nano-thermochromism, porous films, biomimetic surface reconstruction, gridded structures, antireflective overcoatings, etc, have been proposed to tackle these issues. The first approach-nano-thermochromism-which is to integrate VO2 nanoparticles in a transparent matrix, outperforms the rest; while the thermochromic performance is determined by particle size, stoichiometry, and crystallinity. A Hydrothermal method is the most common method to fabricate high-quality VO2 nanoparticles, and has its own advantages of large-scale Synthesis and precise phase control of VO2 . This Review focuses on Hydrothermal Synthesis, physical properties of VO2 polymorphs, and their transformation to thermochromic VO2 (M), and discusses the advantages, challenges, and prospects of VO2 (M) in energy-efficient smart windows application.
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mg doped vo2 nanoparticles Hydrothermal Synthesis enhanced visible transmittance and decreased metal insulator transition temperature
Physical Chemistry Chemical Physics, 2013Co-Authors: Jiadong Zhou, Yanfeng Gao, X Liu, Zhang Chen, Lei Dai, Chuanxiang Cao, Hongjie Luo, Minoru KanahiraAbstract:This paper reports the successful preparation of Mg-doped VO2 nanoparticles via Hydrothermal Synthesis. The metal–insulator transition temperature (Tc) decreased by approximately 2 K per at% Mg. The Tc decreased to 54 °C with 7.0 at% dopant. The composite foils made from Mg-doped VO2 particles displayed excellent visible transmittance (up to 54.2%) and solar modulation ability (up to 10.6%). In addition, the absorption edge blue-shifted from 490 nm to 440 nm at a Mg content of 3.8 at%, representing a widened optical band gap from 2.0 eV for pure VO2 to 2.4 eV at 3.8 at% doping. As a result, the colour of the Mg-doped films was modified to increase their brightness and lighten the yellow colour over that of the undoped-VO2 film. A first principle calculation was conducted to understand how dopants affect the optical, Mott phase transition and structural properties of VO2.
Yukiya Hakuta - One of the best experts on this subject based on the ideXlab platform.
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Hydrothermal Synthesis of metal oxide nanoparticles in supercritical water
Materials, 2010Co-Authors: Hiromichi Hayashi, Yukiya HakutaAbstract:This paper summarizes specific features of supercritical Hydrothermal Synthesis of metal oxide particles. Supercritical water allows control of the crystal phase, morphology, and particle size since the solvent's properties, such as density of water, can be varied with temperature and pressure, both of which can affect the supersaturation and nucleation. In this review, we describe the advantages of fine particle formation using supercritical water and describe which future tasks need to be solved.
Hiromichi Hayashi - One of the best experts on this subject based on the ideXlab platform.
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continuous supercritical Hydrothermal Synthesis of dispersible zero valent copper nanoparticles for ink applications in printed electronics
Journal of Supercritical Fluids, 2014Co-Authors: Shigeki Kubota, Hiromichi Hayashi, Takuya Morioka, Masafumi Takesue, Masaru Watanabe, Richard L SmithAbstract:Abstract Surface-modified zero-valent copper nanoparticles (CuNPs) are of interest as conductive inks for applications in printed electronics. In this work, we report on the Synthesis, stability and characterization of CuNPs formed with a continuous supercritical Hydrothermal Synthesis method. The precursor, copper formate, was fed as an aqueous solution with polyvinylpyrrolidone (PVP) surface modifier and mixed with an aqueous water and formic acid stream to have reaction conditions of 400 °C, 30 MPa and 1.1 s mean residence time. The reaction pathway seemed to proceed step-wise as the hydrolysis of copper formate, followed by dehydration to oxide products and subsequent reduction by hydrogen derived from precursor and formic acid decomposition. The formed surface-modified zero-valent CuNPs had particle sizes of ca. 18 nm, were spherical in shape and contained no oxide contaminants. The formed CuNPs were found to exhibit long-term (>1 year) stability in ethanol as evaluated by shifts in the surface plasmon resonance band of product solutions. Conductive films (0.33 μm thickness) prepared with the CuNPs had a resistivity of 16 μΩ cm. The methods reported in this work show promise for producing conductive inks for use in practical printed electronics.
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Hydrothermal Synthesis of metal oxide nanoparticles in supercritical water
Materials, 2010Co-Authors: Hiromichi Hayashi, Yukiya HakutaAbstract:This paper summarizes specific features of supercritical Hydrothermal Synthesis of metal oxide particles. Supercritical water allows control of the crystal phase, morphology, and particle size since the solvent's properties, such as density of water, can be varied with temperature and pressure, both of which can affect the supersaturation and nucleation. In this review, we describe the advantages of fine particle formation using supercritical water and describe which future tasks need to be solved.
Tomasz Walek - One of the best experts on this subject based on the ideXlab platform.
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the effect of low solid liquid ratio on Hydrothermal Synthesis of zeolites from fly ash
Fuel, 2008Co-Authors: Tomasz Walek, Fumio Saito, Qiwu ZhangAbstract:Abstract Hydrothermal Synthesis of zeolites from class F fly ash was carried out at solid/liquid (S/L) ratio of 4 g/dm3 to investigate the initial dissolution stage of the process. The low S/L ratio caused a significant increase in fly ash dissolution (up to 85 wt%) during first 4 h of reaction. It was shown that for S/L ratios typically used (50–150 g/dm3) fly ash dissolution is largely limited. In these conditions zeolite crystals are formed on the surface of partially dissolved fly ash particles. This precludes further dissolution and results in formation of a low-crystallinity zeolite-like material. At low S/L ratio, a degree of crystallization of 80 wt% was observed, and NaP1, analcime and/or hydroxy-sodalite phases were obtained depending on the applied NaOH concentration and temperature. Single phase NaP1 zeolite was obtained in 2 M NaOH solution at temperature maintained at 104 °C during the stage of dissolution and reduced to 80 °C in the stage of crystallization. Application of low S/L ratio allows a clearer description of the relationships between the Synthesis conditions and the products obtained.
Takao Masuda - One of the best experts on this subject based on the ideXlab platform.
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preparation of nano crystalline mfi zeolite via Hydrothermal Synthesis in water surfactant organic solvent using fumed silica as the si source
Microporous and Mesoporous Materials, 2011Co-Authors: Kazuyuki Iwakai, Teruoki Tago, Hiroki Konno, Yuta Nakasaka, Takao MasudaAbstract:Abstract The preparation of nano-crystalline MFI zeolites (Silicalite-1 and ZSM-5) was carried out by Hydrothermal Synthesis in a water/surfactant/organic solvent using fumed silica and aluminum sulfate as the Si and Al source, respectively. It was confirmed that the surfactant in the solution affected the nucleation rate of the MFI zeolite. Moreover, the crystal size of the MFI zeolite decreased with increasing surfactant concentration, and nanometer-sized MFI zeolites was obtained at a surfactant concentration of 0.25–0.5 mol/L. The successful preparation of MFI zeolite nanocrystals was ascribed to the stabilization of the MFI zeolite precursors and/or crystals by the adsorbed surfactant on their surface. This method was applied to the preparation of nano-crystalline ZSM-5 zeolite. ZSM-5 zeolite with a crystal size of approximately 50 nm was obtained. The nano-crystalline ZSM-5 zeolite was well-crystallized without octahedral Al atoms in the external framework, and exhibited almost the same acidity as a reference ZSM-5 zeolite.
