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961.
Long Fan Yi Tian Liping Peng Yingjuan Zhang Xueming Wang Jia Li Hong Wang Zhiqiang Zhan Guangai Sun Yuechuan Luo Tao Jiang Zhenhua Liu Weidong Wu 《Ceramics International》2021,47(8):11080-11088
Internal stress and stress-related defects are considered as the major obstacles that significantly hinder the growth of high-quality ZnO-based crystals. In this work, high-crystalline-quality ZnO:Zn bulk crystals were successfully grown by carbon-assisted chemical vapor transport (CVT). Internal stress in the crystal was directly measured by a neutron beam from a reactor, and stress distributions along the radial direction at different depths were obtained. The stress, temperature, and flow fields in the growth system were simulated by the finite element (FE) method, and the results agreed with the neutron stress analysis. The etch pit density (EPD), Hall properties, and optical transmittances of different crystal regions were studied in detail, and the distribution trend of the crystal properties was consistent with that of internal stress and stress-related defects in the crystal. It is found that the unique temperature filed in the growth system causes the crystal to bend to a slightly convex toward the growth direction and gives rise to a driving force for structural defect formation. The + c and –c faces of the crystal are subjected to tensile and compressive stress, respectively. The maximum stress values are about 280 MPa and -291 MPa near the central regions of ±c faces, while the crystal periphery is basically free of internal stress. The region near the center of +c face has an EPD of 7.5 × 103 cm-2 and a transmittance of 79.2% at 800 nm wavelength, while the corresponding carrier concentration and mobility are 2.27 × 1017 cm?3 and 159 cm2/V·s, respectively. By comparison, the crystal periphery has an EPD of 102 cm-2 with an 80.5% transmittance at 800 nm, while the carrier concentration and mobility are 1.85 × 1017 cm?3 and 184 cm2/V·s, respectively. 相似文献
962.
International Journal of Computer Vision - With the rapid development of neural architecture search (NAS), researchers found powerful network architectures for a wide range of vision tasks. Like... 相似文献
964.
Yilin Zhang Ji Qi Yuhan Wang Yu Tian Junkai Zhang Tingjing Hu Maobin Wei Yanqing Liu Jinghai Yang 《Ceramics International》2018,44(6):6054-6061
Mn-doped BiFeO3 (BiFe1–xMnxO3, x = 0, 0.03, 0.05, 0.10, 0.15 and 0.20) polycrystalline multiferroic thin films were successfully synthesized using the facile sol-gel spin-coating method. The crystal structures, surface features, elements valences, and magnetic properties of as-prepared samples were systematically explored. X-ray diffraction and Raman spectroscopy studies revealed the substitutions of Mn into the Fe site and a rhombohedral-to-orthorhombic phase transition. The Field Emission Scanning Electron Microscopy showed a decrease in the average particle sizes and an improvement of surface morphology with increasing the concentration of the substitutes. Energy-dispersive X-ray spectroscopy confirmed the doping concentration of Mn2+ in the samples. X-ray photoelectron spectroscopy indicated the co-existence of Mn2+/Mn3+ ions in the doped films. The remnant magnetization value of BiFe0.90Mn0.10O3 thin film was found to be approximately six times than that of pure BiFeO3 thin film under a magnetic field of 10 kOe. The enhanced magnetic property of BiFe0.90Mn0.10O3 thin film was mainly ascribed to the structural distortion of spin cycloid and the enhancement of super-exchange interaction between the Fe3+ (Mn2+) and O2- ions. 相似文献
965.
Synthesis of blue-emitting AlN:Eu2+ spherical phosphors by carbothermal reduction nitridation method
Sen Li Jie Zhang Zhaobo Tian Xuanyi Yuan Songmo Du Qi Wang Wenbin Cao 《Journal of the American Ceramic Society》2020,103(6):3716-3725
In this study, blue-emitting AlN:Eu2+ spherical phosphors were successfully synthesized for the first time by the carbothermal reduction nitridation (CRN) method, assisted with high nitrogen pressure, appropriate synthesis temperature, and the addition of CaF2. The influence of typical experimental parameters, such as N2 pressure, heating temperature, CaF2 content and Eu2+ concentration on the morphologies and luminescence properties of AlN phosphors were comprehensively investigated. The formation mechanism of spherical morphology were significantly proffered, indicating that sufficient liquid Ca-aluminates during the AlN growth stage were essential for the spheroidization process under the action of surface tension. The synthesized AlN:Eu2+ spherical phosphors presented an intense blue emission band centered in the range of 427- 476 nm relative to the reaction temperature. The lifetime of AlN:Eu2+ phosphor was calculated to be around 1.89 μs. The temperature-dependent PL spectra suggested that the emission band did not shift until 225°C. In addition, the spectral analysis strongly suggested that the luminescence property of AlN:Eu2+ phosphors was significantly enhanced by the large particle size, spherical morphology, reduced impurity content, and appropriate Eu2+ concentration. 相似文献
966.
967.
Meena Nemiwal Vijayalakshmi Gosu Tian C. Zhang Dinesh Kumar 《International Journal of Hydrogen Energy》2021,46(17):10216-10238
The development of clean energy technologies to protect the environment is an important demand of the times. Electrocatalysis is emerging as a promising method for evolution of hydrogen and overall water splitting. Nowadays, metal organic frameworks (MOFs) have emerged as electrocatalysts having uniformly distributed active sites and high electrical conductivity. This review summarizes the latest advances in heterogeneous catalysis by MOFs and their composite/derivatives for efficient hydrogen evolution reaction (HER) and water splitting. Pristine MOFs with their recent development are summarized first followed by composites of MOFs with their enhanced electrocatalytic performances. Overall water splitting by using bifunctional electrocatalysts derived from MOFs with different synthetic approaches is provided and this review gives the metal-based categorisation of precursor MOFs. Different strategies to improve chemical stability, conductivity, and overall electrocatalytic properties have been discussed. In the last, perspectives on the synthesis of efficient MOF-based electrocatalyst materials are provided. 相似文献
968.
969.
Xiaobiao Zhu Jinping Tian Lujun Chen 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2012,87(1):123-129
BACKGROUND: In biological treatment of coking wastewater, phenol may decrease the treatment efficiency because of its high concentration and toxicity to microorganisms. Bioaugmentation has been regarded as a good improvement of the traditional biological treatment using isolated degrading strains. In this study, two phenol degrading strains, Pseudomonas sp. PCT01 and PTS02, were isolated and investigated for degradation ability and application to real coking wastewater treatment. RESULTS: Complete phenol degradation was achieved after 18 h inoculation in medium containing 229‐461 mg L?1 of phenol for both strains. The presence of phenol, pyridine and other compounds in mixed substrate or in coking wastewater prolonged the degradation to 20‐32 h with an initial phenol concentration of 160‐280 mg L?1. The study of degradation kinetics yielded a two‐stage model to describe the effect of the initial phenol concentration and inhibitory compounds on phenol degradation. The highest degradation rate constant of the second stage, 1.25 h?1 for PCT01 and 0.75 h?1 for PTS02, was obtained at low phenol concentration in a single substrate. CONCLUSION: It was found that both strains could degrade phenol effectively and maintain their phenol degradation ability in coking wastewater, and therefore could be used for bioaugmentation treatment of coking wastewater. Copyright © 2011 Society of Chemical Industry 相似文献
970.
Shaohai Fu Changsen Du Mingjun Zhang Anli Tian Xia Zhang 《Progress in Organic Coatings》2012,73(2-3):149-154
Polymer-encapsulated phthalocyanine blue pigment dispersion was prepared with a polymerizable dispersant by emulsion polymerization method, and the effect of preparation conditions on the particle size of dispersion was investigated. Dynamic light scattering measurement demonstrated that allyloxy nonyl-phenoxypropanolpolyoxyethyleneetherammonium sulfonate (ANPS) was suitable for phthalocyanine blue pigment modification. The polymer-encapsulated phthalocyanine blue pigment dispersion with the small particles was obtained when the mass ratio of ANPS to phthalocyanine blue pigment, styrene (St) to phthalocyanine blue pigment, and ammonium persulfate (APS) to St was about 0.2, 0.2, and 0.01, respectively. Transmission electron microscopy (TEM), Fourier transforms infrared spectra (FTIR) and thermogravimetric analyses (TGA) provided supporting evidences for the encapsulation of phthalocyanine blue pigment with the formed copolymer. The polymer-encapsulated phthalocyanine blue pigment dispersion showed excellent stabilities to freeze–thaw treatment and centrifugal force. 相似文献