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Nano Energy. 01/2013; 2(1):4-11.
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ABSTRACT: The influence of deposition conditions on the microstructure of Ca3Co4O9 (CCO) thin films fabricated by the pulsed laser deposition technique was investigated. X-ray diffraction revealed that a
fast deposition rate resulted in not only low crystallinity but also the existence of the Ca
x
CoO2 secondary phase. The Ca
x
CoO2 structure was further confirmed by high-resolution transmission electron microscopy. The CCO thin-film growth was deduced
to be a kinetically controlled process, and the quality of the thin films strongly depended on the coalescence process. The
formation of Ca
x
CoO2 was inevitable during the thin-film growth. However, given enough time and supply of oxygen at a lower deposition rate, it
was possible to transform the Ca
x
CoO2 phase into the desired CCO phase during the coalescence process, while with faster deposition, more Ca
x
CoO2 structure was formed, and the secondary phase could hardly transform into the CCO phase.
KeywordsThermoelectric-thin films-Ca3Co4O9
-PLD
Journal of Electronic Materials 04/2012; 39(9):1611-1615. · 1.47 Impact Factor
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Journal of Power Sources 03/2012; 201:288-293. · 4.95 Impact Factor
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ABSTRACT: Ni(OH)(2)/MnO(2) core-shell nanowires with a nanoflake surface have been designed and synthesized, and can be applied not only in neutral electrolytes (355 F g(-1), 70.4 wt% MnO(2)) but are also appropriate for alkaline electrolytes (487.4 F g(-1), 35.5 wt% MnO(2)), with high cycling stability due to the synergistic effect between the core and shell.
Chemical Communications 02/2012; 48(20):2606-8. · 6.17 Impact Factor
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ABSTRACT: A green asymmetric supercapacitor with high energy density has been developed using birnessite-type ultrathin porous MnO(2) nanoflowers (UBMNFs) as positive electrode and functional mesoporous carbon nanotubes (FMCNTs) as negative electrode in 1 M Na(2)SO(4) electrolyte. Both of the electrode materials possess excellent electrochemical performances, with high surface areas and narrow pore size distributions. More significantly, the assembled asymmetric supercapacitor with optimal mass ratio can be cycled reversibly in the high-potential range of 0-2.0 V and exhibits an excellent energy density as high as 47.4 W h kg(-1), which is much higher than those of symmetric supercapacitors based on UBMNFs//UBMNFs and FMCNTs//FMCNTs supercapacitors. Furthermore, our asymmetric supercapacitor (ASC) device also exhibits a superior cycling stability with 90% retention of the initial specific capacitance after 1000 cycles and stable Coulombic efficiency of ~98%. These intriguing results exhibit great potential in developing high energy density "green supercapacitors" for practical applications.
Nanoscale 12/2011; 4(3):807-12. · 5.91 Impact Factor
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ABSTRACT: In this report, we focus on the synthetic challenges for nanoscale 3D fractal architectures, namely the multi-generation growth with control in both size uniformity and colloidal stability; by directing the simultaneous growth of Au and polyaniline on Au seeds, fractal nanoparticles can be achieved with a topology distinctively different from those of spheres, cubes or rods.
Chemical Communications 10/2010; 46(38):7112-4. · 6.17 Impact Factor
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ABSTRACT: We report the synthesis of a series of monodispersed Bi-doped PbTe nanocrystals with tunable morphologies by using a doping precursor of bismuth(III) 2-ethylhexanoate. The as-synthesized Pb(1-x)Bi(x)Te (x = 0.005, 0.010, 0.015, 0.020) nanocrystals are characterized by X-ray diffraction, X-ray photoelectron spectroscopy and Hall measurements. The nanocrystals with controlled spherical, cuboctahedral, and cubic shapes were readily prepared by varying the Bi doping concentration. Thermoelectric investigation of these nanocrystals shows that the Bi(3+) doping increases electrical conductivity from 350 to 650 K and changes the Seebeck coefficient sign from positive to negative.
Nanoscale 07/2010; 2(7):1256-9. · 5.91 Impact Factor
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ABSTRACT: A simple biomolecule-assisted hydrothermal approach has been developed for the fabrication of Bi(2)Te(3) thermoelectric nanomaterials. The product has a nanostring-cluster hierarchical structure which is composed of ordered and aligned platelet-like crystals. The platelets are approximately 100 nm in diameter and only approximately 10 nm thick even though a high reaction temperature of 220 degrees C and a long reaction time of 24 h were applied to prepare the sample. The growth of the Bi(2)Te(3) hierarchical structure appears to be a self-assembly process. Initially, Te nanorods are formed using alginic acid as both reductant and template. Subsequently, Bi(2)Te(3) grows in a certain direction on the surface of the Te rods, resulting in the nanostring structure. The nanostrings further recombine side-by-side with each other to achieve the ordered nanostring clusters. The particle size and morphology can be controlled by adjusting the concentration of NaOH, which plays a crucial role on the formation mechanism of Bi(2)Te(3). An even smaller polycrystalline Bi(2)Te(3) superstructure composed of polycrystalline nanorods with some nanoplatelets attached to the nanorods is achieved at lower NaOH concentration. The room temperature thermoelectric properties have been evaluated with an average Seebeck coefficient of -172 microV K(-1), an electrical resistivity of 1.97 x 10(-3) Omegam, and a thermal conductivity of 0.29 W m(-1) K(-1).
ACS Nano 05/2010; 4(5):2523-30. · 10.77 Impact Factor
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ABSTRACT: Selenium @ carbon core−shell spheres have been synthesized via a simple one-step hydrothermal carbonization process using sucrose and sodium selenite as precursors. Metal selenide or noble metal, e.g. Ag2Se or Au, can be easily encapsulated into the carbon shell by using the as-prepared Se@C core−shell samples as site templates. The transformation from core/shell to yolk/shell structure, e.g. Se@C, Au/Se@C and Ag2Se@C, can be achieved through thermal evaporation under electron beam irradiation or vacuum annealing to evaporate Se. The optical absorption of the samples can be tuned by varying the structure/compositions of the samples.
08/2009;
