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711 results on '"Zhang, Bo-ping"'

254. High Thermoelectric Figure of Merit Achieved in Cu2S1–xTexAlloys Synthesized by Mechanical Alloying and Spark Plasma Sintering

Author

Yao, Yao, Zhang, Bo-Ping, Pei, Jun, Sun, Qiang, Nie, Ge, Zhang, Wen-Zhen, Zhuo, Zhen-Tao, and Zhou, Wei

Abstract

Chalcogenides have been considered as promising thermoelectric materials because of their low cost, nontoxicity, and environmental benignity. In this work, we synthesized a series of Cu2S1–xTex(0 ≤ x≤ 1) alloys by a facile, rapid method of mechanical alloying combined with spark plasma sintering process. The Cu2S1–xTexsystem provides an excellent vision of the competition between pure phase and phase transformation, entropy-driven solid solution, and enthalpy-driven phase separation. When the Te concentration increases, the Cu2S1–xTexsystem changed from the pure monoclinic Cu2S at x= 0 to monoclinic Cu2S1–xTexsolid solution at 0.02 ≤ x≤ 0.06 and then transforms to hexagonal Cu2S1–xTexsolid solution at 0.08 ≤ x≤ 0.1. The phase separation of hexagonal Cu2Te in the hexagonal Cu2S matrix occurs at 0.3 ≤ x≤ 0.7 and finally forms the hexagonal Cu2Te at x= 1. Owing to the changed band structure and the coexisted Cu2S and Cu2Te phases, greatly enhanced power factor was achieved in all Cu2S1–xTex(0 < x< 1) alloys. Meanwhile, the point defect introduced by the substitution of Te/S atoms strengthened the phonon scattering, resulting in a lowered lattice thermal conductivity in most of these solid solutions. As a consequence, Cu2S0.94Te0.06exhibits a maximum ZTvalue of 1.18 at 723 K, which is about 3.7 and 14.8 times as compared to the values of pristine Cu2S (0.32) and Cu2Te (0.08), respectively.

Published
2018
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263. Electrical transport properties of La2CuO4 ceramics processed by the spark plasma sintering

Author

Lin, Yuan-Hua, Liu, Yong, Zhang, Bo-Ping, Nan, Ce-Wen, Li, Jing-Feng, Shen, Zhijian, Lin, Yuan-Hua, Liu, Yong, Zhang, Bo-Ping, Nan, Ce-Wen, Li, Jing-Feng, and Shen, Zhijian

Abstract

Highly dense La2CuO4 ceramics have been prepared by the spark plasma sintering technique. Temperature dependence of electrical conductivity indicates that La2CuO4 ceramics sintered at over 875 degrees C exhibit a metal-like behavior, which should be ascribed to the special La2CuO4 crystal structure and its correlation splitting of the half-filled d(x2-y2) band. Our experimental data indicate that all of the La2CuO4 samples exhibit positive thermoelectric power in the whole measuring temperature range, indicating that the majority of charge carriers are holes. It is desirable to obtain good thermoelectric performance for this system by optimizing the electrical properties and reducing the thermal conductivity., authorCount :6

Published
2007
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281. Manipulation of charge transfer in vertically aligned epitaxial ferroelectric KNbO3nanowire array photoelectrodes

Author

Li, Shun, Zhang, Jianming, Zhang, Bo-Ping, Huang, Wei, Harnagea, Catalin, Nechache, Riad, Zhu, Lifeng, Zhang, Suwei, Lin, Yuan-Hua, Ni, Liang, Sang, Yuan-Hua, Liu, Hong, and Rosei, Federico

Abstract

We demonstrate the growth and characterization of an array of ferroelectric nanowires for photoelectrochemical (PEC) hydrogen production. The photoelectrodes are made of vertically aligned one-dimensional nanowires of the “classic” ferroelectric perovskite KNbO3grown epitaxially on a Nb-doped SrTiO3substrate. The charge transfer properties of the photoelectrodes can be effectively tuned by controlling the polarization state, thereby optimizing PEC performance. By manipulating the poling bias from +15V to −15V, we were able to tune the photocurrent density in the range from ca. 0.7–11.5 μA·cm−2(at 0V vs. Ag/AgCl) under irradiation of air mass 1.5 global (AM 1.5G) full sunlight at 100mW/cm2, while the onset potential switches from −0.32 to −0.46V. Our work provides the basis for understanding PEC reactions conducted with ferroelectric nanowire photoelectrodes as well as insights on strategies for constructing high performance nanowire array-based PEC systems.

Published
2017
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282. Enhanced photocatalytic activity in Ag-nanoparticle-dispersed BaTiO3composite thin films: Role of charge transfer

Author

Zhang, Suwei, Zhang, Bo-ping, Li, Shun, Huang, Zhicheng, Yang, Chushu, and Wang, Huiying

Abstract

Optical absorption and photocatalytic activity can be enhanced by surface plasmon resonance (SPR) effect, but the charge transfer (CT) mechanism between the dispersed noble metal nanoparticles (NPs) and the semiconductor matrix has been ignored. Herein, we adduce a direct and strong evidence in Ag-nanoparticle-dispersed BaTiO3(Ag/BTO) composite films through X-ray photoelectron and photoluminescence spectra which reveals the CT from BTO trapped by Ag NPs under UV light and from Ag NPs to BTO under visible light. Owing to the broadened optical absorption and efficient CT from Ag NPs to BTO, the Ag25/BTO film manifests the optimal photocatalytic activity under the irradiation of visible light rather than UV–Vis light. Our work provides a helpful insight to design highly efficient plasmonic photocatalyst through considering the synergetic effect of the CT between metal and semiconductor on the enhanced photocatalytic activity.

Published
2017
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297. Effects of mechanical alloying process on thermoelectric properties of Bi2S3 Bulk

Author

Zhang Bo-Ping, Liu Yong, Ge Zhen-Hua, Li Jing-Feng, and Yu Zhao-Xin

Subjects
chemistry.chemical_compound, Materials science, chemistry, Electrical resistivity and conductivity, Phase (matter), Thermoelectric effect, Acetone, General Physics and Astronomy, Spark plasma sintering, Power factor, Crystallite, Composite material, Microstructure
Abstract

Bismuth sulfide (Bi2S3) polycrystalline bulks are fabricated by spark plasma sintering (SPS) combined with a mechanical alloying (MA) process. The electrical transport properties are investigated with a special emphasis on dry-milling speed, wet-milling time and mediums in MA process. The phase structure, the microstructure, and the electrical/thermal transport properties for the bulk samples are measured. The results suggest that the second Bi2O3 phase is formed because of the micro-oxidation when the wet medium is fixed to absolute ethyl alcohol, which refines the grain sizes and affects electrical transport properties of the bulk samples. Prolonging the wet-milling time in absolute ethyl alcohol causes the increase of resistivity and the decrease of the power factor. The electrical transport properties degrade due to the porous microstructure in bulk samples even without oxidization as the acetone is used as a milling medium. The largest ZT value 0.25 is obtained at 573 K for the samples dry-milled under 425 r/min for 15 h without wet-milling, which is the highest value in the reported values so far.

Published
2012
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