The Experts below are selected from a list of 4881 Experts worldwide ranked by ideXlab platform
Jinshu Wang - One of the best experts on this subject based on the ideXlab platform.
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investigations of the nickel promotional effect on the reduction and sintering of Tungsten Compounds
International Journal of Refractory Metals & Hard Materials, 2019Co-Authors: Qiao Yin, Chen Lai, Shuqun Chen, Jian Peng, Wenyuan Zhou, Jinshu WangAbstract:Abstract In this article, Ni-coated W powders were firstly prepared by a liquid-solid doping method combined with air calcination and hydrogen reduction. X-ray diffraction analysis, scanning electron microscope, transmission electron microscope, X-ray photoelectron spectroscopy and temperature programmed reduction analysis were carried out to investigate the nickel doping process in WO3 and its influence on the reduction behaviors of Tungsten oxides. It reveals that after calcinations most Ni ions would occupy the lattice sites of host W ions and decrease the interplanar spacing of WO3. The latter is due to the promotion of oxygen vacancy generation within WO3 rather than the changes in ionic radius. After hydrogen reduction, the doped Ni atoms precipitate onto the surface of W particles as thin metallic coatings, whereby the size and morphology of reduced W particles are varied greatly with increasing Ni addition. The presence of Ni has also been found to lower the reduction barriers for WO3 by using first-principles calculation. Finally, W-Ni compacts were sintered at 1500 °C in hydrogen atmosphere and the accelerated densification phenomenon of W alloy upon Ni doping is discussed.
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reduction sintering and mechanical properties of rhenium Tungsten Compounds
Journal of Alloys and Compounds, 2018Co-Authors: Chen Lai, Jinshu Wang, Fan Zhou, Wei Liu, Naihua MiaoAbstract:Abstract Porous Tungsten-rhenium powders with various compositions were prepared by a spray drying method combined with two-stage hydrogen reduction. Using the W-Re powders, W-Re alloy substrates were successfully fabricated by high temperature sintering under the protection of hydrogen. X-ray diffraction analysis, thermogravimetric analysis and temperature programmed reduction were carried out to study the reduction behavior of the Tungsten and rhenium containing precursor powders prepared by spray drying. It reveals that the first stage reduction temperature has a significant impact on the microstructure of the W-Re powders. Rhenium in the mixed powder affects the reduction behavior of WO3. Properties of the W-Re alloy matrices, including relative density, open porosity, mechanical characteristics and electronic structures are also investigated. The first-principles calculation method proved that rhenium reduces the reduction barrier of WO3, and W-Re Compounds obtained in this study are suggested to be a ductile material.
Chen Lai - One of the best experts on this subject based on the ideXlab platform.
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investigations of the nickel promotional effect on the reduction and sintering of Tungsten Compounds
International Journal of Refractory Metals & Hard Materials, 2019Co-Authors: Qiao Yin, Chen Lai, Shuqun Chen, Jian Peng, Wenyuan Zhou, Jinshu WangAbstract:Abstract In this article, Ni-coated W powders were firstly prepared by a liquid-solid doping method combined with air calcination and hydrogen reduction. X-ray diffraction analysis, scanning electron microscope, transmission electron microscope, X-ray photoelectron spectroscopy and temperature programmed reduction analysis were carried out to investigate the nickel doping process in WO3 and its influence on the reduction behaviors of Tungsten oxides. It reveals that after calcinations most Ni ions would occupy the lattice sites of host W ions and decrease the interplanar spacing of WO3. The latter is due to the promotion of oxygen vacancy generation within WO3 rather than the changes in ionic radius. After hydrogen reduction, the doped Ni atoms precipitate onto the surface of W particles as thin metallic coatings, whereby the size and morphology of reduced W particles are varied greatly with increasing Ni addition. The presence of Ni has also been found to lower the reduction barriers for WO3 by using first-principles calculation. Finally, W-Ni compacts were sintered at 1500 °C in hydrogen atmosphere and the accelerated densification phenomenon of W alloy upon Ni doping is discussed.
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reduction sintering and mechanical properties of rhenium Tungsten Compounds
Journal of Alloys and Compounds, 2018Co-Authors: Chen Lai, Jinshu Wang, Fan Zhou, Wei Liu, Naihua MiaoAbstract:Abstract Porous Tungsten-rhenium powders with various compositions were prepared by a spray drying method combined with two-stage hydrogen reduction. Using the W-Re powders, W-Re alloy substrates were successfully fabricated by high temperature sintering under the protection of hydrogen. X-ray diffraction analysis, thermogravimetric analysis and temperature programmed reduction were carried out to study the reduction behavior of the Tungsten and rhenium containing precursor powders prepared by spray drying. It reveals that the first stage reduction temperature has a significant impact on the microstructure of the W-Re powders. Rhenium in the mixed powder affects the reduction behavior of WO3. Properties of the W-Re alloy matrices, including relative density, open porosity, mechanical characteristics and electronic structures are also investigated. The first-principles calculation method proved that rhenium reduces the reduction barrier of WO3, and W-Re Compounds obtained in this study are suggested to be a ductile material.
Naihua Miao - One of the best experts on this subject based on the ideXlab platform.
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reduction sintering and mechanical properties of rhenium Tungsten Compounds
Journal of Alloys and Compounds, 2018Co-Authors: Chen Lai, Jinshu Wang, Fan Zhou, Wei Liu, Naihua MiaoAbstract:Abstract Porous Tungsten-rhenium powders with various compositions were prepared by a spray drying method combined with two-stage hydrogen reduction. Using the W-Re powders, W-Re alloy substrates were successfully fabricated by high temperature sintering under the protection of hydrogen. X-ray diffraction analysis, thermogravimetric analysis and temperature programmed reduction were carried out to study the reduction behavior of the Tungsten and rhenium containing precursor powders prepared by spray drying. It reveals that the first stage reduction temperature has a significant impact on the microstructure of the W-Re powders. Rhenium in the mixed powder affects the reduction behavior of WO3. Properties of the W-Re alloy matrices, including relative density, open porosity, mechanical characteristics and electronic structures are also investigated. The first-principles calculation method proved that rhenium reduces the reduction barrier of WO3, and W-Re Compounds obtained in this study are suggested to be a ductile material.
Jurij V Brencic - One of the best experts on this subject based on the ideXlab platform.
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self assembly of w2o4 2 syntheses and structures of high valent Tungsten Compounds
ChemInform, 2014Co-Authors: Barbara Modec, Jurij V BrencicAbstract:Green needle-shaped crystals of compound (II) are obtained, which decompose on exposure to air.
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self assembly of w2o4 2 syntheses and structures of high valent Tungsten Compounds
Inorganic Chemistry Communications, 2014Co-Authors: Barbara Modec, Jurij V BrencicAbstract:Abstract Oxidation of K 3 [W III 2 Cl 9 ] in the mixture of concentrated hydrochloric acid and pyridine in the presence of hydrazinium dichloride afforded (PyH) 5 [W V OCl 4 (H 2 O)] 3 Cl 2 (PyH + = pyridinium cation, C 5 H 5 NH + ) ( 1 ), obtained as emerald green needle-shaped crystals. The compound contains mononuclear octahedrally shaped [WOCl 4 (H 2 O)] − ions. In contrast to its molybdenum analog, 1 shows a marked instability in the air. Solvothermal reaction of a tetrabutylammonium salt of the [WOCl 4 (H 2 O)] − ion with pyridine at 115 °C afforded a small amount of orange crystals of [W V 8 W VI 2 O 26 (Py) 8 ]·Py ( 2 ) (Py = pyridine, C 5 H 5 N). The W V centers can be clearly distinguished from the W VI sites, namely they are grouped into four metal–metal bonded {W V 2 O 4 } 2 + cores. The structure of the cluster is virtually identical with the analogous molybdenum complex, [Mo 10 O 26 (Py) 8 ]. The isolation of [W 10 O 26 (Py) 8 ]·Py ( 2 ) confirms that the {W 2 O 4 } 2 + core forms from the [WOCl 4 (H 2 O)] − ions upon the substitution of the labile ligands.
A I Muftah - One of the best experts on this subject based on the ideXlab platform.
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temperature programmed and x ray diffractometry studies of hydrogen reduction course and products of wo3 powder influence of reduction parameters
Thermochimica Acta, 2011Co-Authors: M I Zaki, Nasr E Fouad, S A A Mansour, A I MuftahAbstract:Abstract The hydrogen-reduction course and products of synthetic Tungsten(VI) oxide (WO 3 ) were examined by means of temperature-programmed reduction (TPR) and X-ray powder diffractometry (XRD) studies. A set of model Tungsten Compounds was procured and examined similarly for reference purposes. Results obtained could help resolving two subsequent reduction stages: (i) a low-temperature stage ( 3 is reduced to the tetravalent state (WO 2 ) via formation and subsequent reduction of intermediate WO 2.96 , WO 2.9 , WO 2.72 oxides; and (ii) a high-temperature stage (>1050 K) through which WO 2 thus produced is reduced to the metallic state (W o ) via two intermediate oxide species (tentatively, WO and W 2 O–W 3 O). Reduction events involved in the high-temperature stage were found to be relatively more sensitive to the reduction parameters; namely, the starting oxide mass, heating temperature and rate, and gas flow rate and composition. They were also found to require lower activation energies than those required by events occurring throughout the low-temperature stage, a fact that may suspect compliance of the high-temperature reduction events to autocatalytic effects.
