Zhishen Wu

Henan University, K’ai-feng-shih, Henan Sheng, China

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Publications (59)95.79 Total impact

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    ABSTRACT: TiO2−δ–La composite nanotubes are prepared by heating the ethanol solution of La(NO3)3⋅6H2O which is introduced into nanotube titanium acid at pre-set temperature. The effect of La dosage on the microstructure and electrochemical properties of as-fabricated TiO2−δ–La composite nanotubes is investigated. Results indicate that La3+ can be trapped in the internal/external surfaces and the interlayer space of nanotubes. All of these help to retain the nanotubular morphology and layered structure during the dehydration process. Ti3+ defects generated by the dehydration of nanotube titanium acid can be stabilized by the formed Ti–O–La bond. So, as-fabricated TiO2−δ–La composite nanotubes samples exhibit markedly improved electrochemical properties than pristine TiO2. Particularly, the electrode made of TiO2−δ–La composite nanotubes containing 5% La element (mass fraction) has a high capacity of 142 mA h g−1 at a charge/discharge rate of 20 C rate and a capacity retention of 87% after 1000 cycles at 10 C, showing superior electrochemical performance and great potential as an anode material for high-rate lithium-ion batteries.
    Journal of Alloys and Compounds. 01/2014; 609:178–184.
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    ABSTRACT: Cu nanoparticle surface-capped by methoxylpolyethyleneglycol xanthate was synthesized using in situ surface-modification technique. The size, morphology and phase structure of as-prepared Cu nanoparticle were analyzed by means of X-ray diffraction and transmission electron microscopy. The tribological properties of as-synthesized Cu nanoparticle as an additive in distilled water were investigated with a four-ball machine, and the morphology and elemental composition of worn steel surfaces were examined using X-ray photoelectron spectroscopy and scanning electron microscope equipped with an energy-dispersive spectrometer attachment. Results show that as-synthesized Cu nanoparticle as a water-based lubricant additive is able to significantly improve the tribological properties and load-carrying capacity of distilled water, which is ascribed to the deposition of Cu nanoparticles on steel sliding surfaces giving rise to a protective and lubricious Cu layer thereon. In the meantime, they may also tribochemically react with rubbing steel surfaces to generate a boundary lubricating film consisting of Cu, FeS and FeSO4 on the rubbed steel surface, which helps to result in greatly improved tribological properties of distilled water, thereby reducing friction and wear of the steel–steel pair.
    Tribology Letters 01/2014; 54(1). · 1.74 Impact Factor
  • Electrochimica Acta. 01/2014; 132:230–238.
  • Thin Solid Films 09/2013; · 1.87 Impact Factor
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    ABSTRACT: Cu/SiO2 nanocomposite was synthesized by sol-gel method. The size, morphology and phase structure of as-prepared Cu/SiO2 nanocomposite were analyzed by means of X-ray diffraction and transmission electron microscopy, and its ultraviolet-visible light spectrum was measured in relation to surface plasmon excitation of Cu particles. The tribological properties of as-synthesized Cu/SiO2 nanocomposite as an additive in distilled water were investigated with a four-ball machine, and the morphology and elemental composition of worn steel surfaces were examined with a scanning electron microscope and an X-ray photoelectron spectroscope. Results show that as-synthesized Cu/SiO2 nanocomposite as a lubricant additive is able to significantly improve the tribological properties of distilled water. A protective and lubricious film composed of Cu and a small amount of FeS, FeSO4 and SiO2 is formed on steel sliding surfaces lubricated by distilled water containing Cu/SiO2 nanocomposite. During friction process Cu nanoparticles can be released from Cu/SiO2 nanocomposite to fill up micro-pits and grooves of steel sliding surfaces, resulting in greatly reduced friction and wear of steel frictional pair via self-repairing. The state and thickness of the film formed on the worn surface is closely related to applied load; and Cu/SiO2 nanocomposite might be a promising water-based lubricant additive for steel-steel contact subjected to moderate load.
    Applied Surface Science 10/2012; · 2.54 Impact Factor
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    ABSTRACT: Compact and uniform layered double hydroxides thin films were fabricated on aluminum substrates using a simple solution-immersion process; upon chemical modification with perfluorosilane, the wettability of the aluminum surface changed from hydrophilic to superhydrophobic. The products were characterized by scanning electron microscopy, X-ray powder diffraction, and X-ray photoelectron spectroscopy. It is confirmed that the synergic effect of the surface morphology and the surface free energy contribute to this unique surface water repellence. In addition, the superhydrophobic films possess long-term storage stability and good adhesion strength to aluminum substrates, which enhance their potential practical applications.
    Journal of Materials Science 03/2012; 47(6):2757-2762. · 2.31 Impact Factor
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    ABSTRACT: The present work describes a one-step facile spray deposition process for the fabrication of superhydrophobic and superoleophilic nanoparticle film. The film shows fast response wettability transition between superhydrophobicity and hydrophilicity. The reversible superhydrophobicity to hydrophilicity switching can be easily carried out by adjusting the temperature. The film also demonstrates oil uptake ability and can selectively adsorb oil floating on water surface. Furthermore, the film surface shows the antifouling performance for organic solvents, which can self-remove the organic solvents layer and recover its superhydrophobic behavior. The advantage of the present approach is that the damaged film can be easily repaired by spraying again.
    ACS Applied Materials & Interfaces 02/2012; 4(3):1742-6. · 5.01 Impact Factor
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    ABSTRACT: LiFePO4/C composites were synthesized by two methods using home-made amorphous nano-FePO4 as the iron precursor and soluble starch, sucrose, citric acid, and resorcinol–formaldehyde (RF) polymer as four carbon precursors, respectively. The crystalline structures, morphologies, compositions, electrochemical performances of the prepared powders were investigated with XRD, TEM, Raman, and cyclic voltammogram method. The results showed that employing soluble starch and sucrose as the carbon precursors resulted in a deficient carbon coating on the surface of LiFePO4 particle, but employing citric acid and RF polymer as the carbon precursors realized a uniform carbon coating on the surface of LiFePO4 particle, and the corresponding thicknesses of the uniform carbon films are 2.5nm and 4.5nm, respectively. When RF polymer was used as the carbon precursor, the material showed the highest initial discharge capacity (138.4mAhg−1 at 0.2C at room temperature) and the best rate performance among the four materials.
    Powder Technology - POWDER TECHNOL. 01/2011; 212(2):327-331.
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    ABSTRACT: Titanium dioxide (TiO2) nanotube with a large amount of single-electron-trapped-oxygen-vacancies (coded as T2) was obtained by annealing nanotube H2Ti2O4(OH)2 (coded as T1) at 400°C in air. Silver nanoparticles with a diameter of about 30–50nm were loaded onto the surface of T2 via deposition associated with photochemical reduction under ultraviolet irradiation. The resulting Ag/TiO2 nanotube (coded as T3) was characterized by means of transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and ultraviolet–visible light diffusion reflectance spectrometry. It was found that C3H6 experienced unusual photo-induced adsorption–desorption on T3 under visible light irradiation. Namely, C3H6 was initially desorbed from T3 and then adsorbed on T3 under visible light irradiation. On the contrary, C3H6 was initially adsorbed on T3 in the dark, followed by desorption. The reason might lie in that two kinds of active sites exist on the surface of T3, corresponding to quite different rates of adsorption and desorption. It was found that oxygen vacancies in association with deposited silver particles, were responsible for the alternative adsorption–desorption of C3H6 on T3.
    Applied Surface Science 01/2011; 257(6):1864-1870. · 2.54 Impact Factor
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    ABSTRACT: CeF3 nanocrystals with plate-like and perforated morphologies were successfully synthesized via a facile hydrothermal route. The nanocrystals of CeF3@silica can dispersed in aqueous solution were also prepared. The effects of fluoride sources on the morphology and microstructure of the nanocrystals were investigated by means of transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and powder X-ray diffraction (XRD). Results indicate that the morphology of the rare earth compound nanocrystals can be well tuned by selecting proper fluoride sources. The ultraviolet (UV) absorption peak of the CeF3 nanocrystals is slightly blue shifted along with the decrease of size. And the photoluminescence (PL) intensity of the CeF3 nanocrystals is closely related to size and microstructure as well.
    Journal of Nanoparticle Research 01/2011; 13(5):2041-2047. · 2.18 Impact Factor
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    ABSTRACT: We found in our previous work that the high photoactivity of N-doped TiO(2) for the oxidation of propylene under visible light was attributed to the photoactive center V(o)(•)-NO-Ti and the formation of sub-band originated from a large amount of single-electron-trapped oxygen vacancies (denoted as V(o)(•); C. X. Feng, Y. Wang, Z. S. Jin, J. W. Zhang, S. L. Zhang, Z. S. Wu, Z. J. Zhang [2008], New J. Chem. 32, 1038). In the present study, the structure of the sub-band within E(g) of a representative sample N-NTA-400 was investigated by means of photoluminescence (PL) spectrometry and ultraviolet-visible light-near infrared diffuse reflectance spectra. The coaction of the sub-band and doped nitrogen on visible light photocatalytic activity of N-doped TiO(2) was also investigated. The electron spin resonance spectra measured under laser irradiation (λ = 532 nm) indicate that the doped nitrogen may contribute to stabilize the trapping electron center, i.e. surface oxygen vacancy (V(o)(••)), and hence suppress the PL, enhancing the photocatalytic activity.
    Photochemistry and Photobiology 09/2010; 86(6):1222-9. · 2.29 Impact Factor
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    ABSTRACT: A simple and practical approach for synthesizing ultrafine Ni fibers under normal pressure via the reduction of Ni2+ ions by hydrazine hydrate in the absence of any templates or external magnetic field is reported. The mechanisms and a simplified model of formation for the Ni fibers are proposed, and the correlated magnetic properties and electromagnetic characteristics of the Ni products are studied systematically. The results of a series of comparative studies indicate that the feeding sequence of the reactants and the concentration of NaOH solution are critical to controlling the shape of the target products from fiber to sphere. The Ni fibers have an enhanced magnetic coercivity compared with that of the Ni spheres. The composites filled with Ni fibers have an electromagnetic wave absorbance within the frequency range 2.0−18.0 GHz stronger than that for the Ni sphere-filled composites. Specifically, by properly adjusting the matching thicknesses, a minimum reflection loss (RL) of −39.5 dB at 4.8 GHz and an absorbance band of less than −20 dB within 3−16 GHz are obtained for the Ni fiber-filled composites, showing that the Ni fibers may have promising application for electromagnetic wave absorbance.
    Journal of Physical Chemistry C - J PHYS CHEM C. 05/2010; 114(22).
  • ChemInform 01/2010; 41(1).
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    ABSTRACT: The present work reports a simple method to produce hierarchical CuO architectures on copper substrate through self-generation. Subsequently, CuO@Cu2S composites have been successfully synthesized from the hierarchical CuO precursors via a facile solution-immersion process. These products were characterized by field-emission scanning electron microscopy, x-ray powder diffraction and x-ray photoelectron spectrum. The wettability of the products was also investigated. It was found that the wettability of the CuO@Cu2S composite film could be easily changed from hydrophilic to superhydrophobic with simple fluorination modification. Compared with other methods, the method herein is mild, economical and easy to create large area superhydrophobic materials on copper substrate.
    Materials Letters - MATER LETT. 01/2010; 64(10):1200-1203.
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    ABSTRACT: An ultrasonically assisted two-step polyol process was established to prepare a novel ethylene glycol-based zinc alkoxide with octahedral morphology. The octahedral-shaped zinc alkoxide particles could be converted to ZnO by heating to 350 °C or above, without altering the octahedral shape. Interestingly, when exposed to atmospheric moisture at room temperature for more than 48 h, the octahedral zinc alkoxide was in situ transformed to single-crystal ZnO nanoparticles via hydrolysis in the octahedral configuration, accompanied by release of ethylene glycol. The morphology, composition, and phase structure of the glycol-based zinc alkoxide and the resulting products, i.e., octahedral ZnO polycrystalline particles and single-crystal ZnO nanoparticles, were characterized by means of scanning electron microscopy (SEM), Fourier transformation infrared spectrometry (FTIR), X-ray diffraction (XRD), thermal analysis (TA), elemental analysis (EA), and transmission electron microscopy (TEM). The present approach for octahedral polycrystalline ZnO or spherical single-crystal ZnO nanoparticles would provide a potential facile route to fabricating other metal oxides with controllable morphology. The hydrolysis of the octahedral zinc alkoxide might be used to facilitate slow release of ethylene glycol, a common compound for lowering freezing point.
    Growth Des. 05/2009; 9.
  • Guangxiu Cao, Yanbao Zhao, Zhishen Wu
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    ABSTRACT: In this paper, we report a novel solution route to prepare In2S3 nanoparticles through directly dispersing melted indium in a sulfur-dissolved solvent. X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and electron diffraction (ED) show the formation of In2S3 nanoparticles possessing tetragonal structure with an average particle diameter of 30 nm. The as-prepared In2S3 nanoparticles display strong blue–UV emission, promising for applications in optical devices.
    Journal of Alloys and Compounds. 03/2009; 472(s 1–2):325–327.
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    ABSTRACT: Polyelectrolyte multilayers (PEMs) fabricated by spin-assisted layer-by-layer assembly technique were used as nanoreactors for in-situ synthesis Cu nanoparticles. Chemical reaction within the PEMs was initiated by a reaction cycle in which Cu2+ was absorbed into the polymer-coated substrate and then reduced in NaBH4 solutions. Repeating the above process resulted in an increase in density of the nanoparticles and further growth in the dimension of the particles initially formed. So, different Cu-nanoparticle polyelectrolyte multilayers were formed in the process. The friction and wear properties of Cu-nanoparticle PEMs formed by different reaction cycles were investigated on a microtribometer against a stainless steel ball. The PEMs reinforced with Cu nanoparticles, prepared under the best preparation conditions, possess good tribological behavior, because of the weakened adhesion between the PEMs and the substrate and decreased mobility of the polymeric chains in the presence of excessive Cu nanoparticles generated at larger reaction cycles.
    Thin Solid Films 01/2009; · 1.87 Impact Factor
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    ABSTRACT: Disk-like CeF3 nanocrystals were successfully synthesized via ultrasonically assisted route. The effects of ultrasonic irradiation time and temperature on the morphology and microstructure of CeF3 nanocrystals were investigated based on characterization of the nanocrystals by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and photoluminescence spectrophotometry (PL). Results indicate that the size of the CeF3 disks can be tuned by simply changing the ultrasonic irradiation time, and low temperature favors the formation of uniform CeF3 nanocrystal. The PL spectra showed that PL intensity of the CeF3 nanocrystals was related to the surface defect, crystalline extent, and size.
    Journal of Alloys and Compounds 01/2009; 485(1). · 2.73 Impact Factor
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    ABSTRACT: An oil soluble fluorine-containing octadecylamine salt of decapentylfluorooctanoic acid was synthesized and characterized by Fourier transform infrared spectroscopy (FTIR), 1H-nuclear magnetic resonance (1H NMR) and 19F NMR. The thermal stability of octadecylamine salt of decapentylfluorooctanoic acid was measured by a thermogravimetric (TG) analysis. The anti-wear and friction-reducing properties of the amine salt as a silicone-based lubricating oil additive were evaluated using a four-ball tribotester. The results indicated that both the wear resistance and the load-carrying capacity of a silicone-based lubricating oil 4609 shock absorption liquid were improved and the friction coefficient was decreased by the additive. The wear scar, after being cleaned using an ultrasonic bath in petroleum ether, was characterized with scanning electron microscopy (SEM) and X-ray photoelectron spectrometry (XPS). It was found that the boundary film on the worn surface was composed of fluorine-containing organic film and iron fluoride such as FeF2, which provided the oil with improved anti-wear and friction-reducing properties.
    Tribology International 01/2009; 42(3):397-402. · 1.54 Impact Factor
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    ABSTRACT: The influence of NH3-treating temperature on the visible light photocatalytic activity of N-doped P25-TiO2 as well as the relationship between the surface composition structure of TiO2 and its visible light photocatalytic activity were investigated. The results showed that N-doped P25-TiO2 treated at 600°C had the highest activity. The structure of P25-TiO2 was converted from anatase to rutile at 700°C. Moreover, no N-doping was detected at the surface of P25-TiO2. There was no simply linear relationship between the visible light photocatalytic activity and the concentration of doped nitrogen, and visible light absorption. The visible light photocatalytic activity of N-doped P25-TiO2 was mainly influenced by the synergistic action of the following factors: (i) the formation of the single-electron-trapped oxygen vacancies (denoted as Vo·); (ii) the doped nitrogen on the surface of TiO2; (iii) the anatase TiO2 structure.
    Science in China Series B Chemistry 01/2009; 52(8):1164-1170. · 1.20 Impact Factor