Zhishen Wu

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

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Publications (64)173.22 Total impact

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    ABSTRACT: TiO2 nanoparticles containing oxygen vacancies mostly existed in the bulk phase, and the counterpart with oxygen vacancies both on the surface and in the bulk phase, were successfully prepared via calcination of nanotube titanic acid under air and H2 atmosphere respectively. The effect of surface and/or bulk oxygen vacancies on the structure and electrochemical properties of electrode materials were studied. The materials characterization results demonstrate that under air atmosphere, the obtained TiO2 nanoparticles containing oxygen vacancies mainly in the bulk phase, while its surface still remains the stoichiometric structure. While hydrogenation process leads to a crystalline-disordered core–shell structure, oxygen vacancies existed both on the surface and in the bulk of TiO2 nanoparticles. As-fabricated TiO2 samples containing oxygen vacancies exhibit markedly improved electrochemical properties comparison with TiO2 nanoparticles without defects. Oxygen vacancies can act as physical space for Li-ion storage thus improve the specific capacity of electrode, the enhanced rate performance mainly origin from the bulk oxygen vacancies.
    Journal of Alloys and Compounds 09/2015; 642. DOI:10.1016/j.jallcom.2015.04.096 · 2.73 Impact Factor
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    ABSTRACT: A simple aqueous solution-immersion process was established to fabricate highly dense ordered Cu2O nanorods on commercial phosphor-copper mesh, with which the preparation was accomplished in distilled water. The present method, with the advantages of simple operation, low cost, short reaction time and environmental friendliness, can be well adopted to fabricate desired Cu2O nanostructures on the phosphor-copper mesh under mild conditions. After surface modification with 1-dodecanethiol, the Cu2O nanostructure obtained on the phosphor-copper mesh exhibits excellent superhydrophobicity and superoleophilicity. Besides, a "mini boat" made from the as-prepared superhydrophobic phosphor-copper mesh can float freely on water surface and in situ collect oil from water surface. This demonstrates that the present approach, being facile, inexpensive and environmentally friendly, could find promising application in oil-water separation and off shore oil spill cleanup.
    ACS Applied Materials & Interfaces 01/2015; 7(4). DOI:10.1021/am507620s · 6.72 Impact Factor
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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 10/2014; 609:178–184. DOI:10.1016/j.jallcom.2014.04.115 · 2.73 Impact Factor
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    ABSTRACT: N-doped carbon and TiN composite conductive structure with homogeneous distribution on the surface and in the bulk of spinel lithium titanate (Li4Ti5O12) nanoparticles is prepared via a simple one-step chemical vapor deposition assisted solid-state route in the presence of layered structure sodium titanate nanotubes as the titanium source and ethylenediamine as the carbon and nitrogen source. Results indicate that as-fabricated Li4Ti5O12 samples containing N-doped carbon and TiN composite conductive structure exhibit markedly improved electrochemical properties as compared with pristine Li4Ti5O12. Particularly, the electrode made from Li4Ti5O12 containing N-doped carbon and TIN composite conductive structure obtained after 60 min of treatment in the presence of ethylenediamine has a high capacity of 162 mAh center dot g(-1) at a charge/discharge rate of 20C as well as a substantial capacity of 92% and a capacity retention of 75% after 2500 cycles at 10C, showing superior electrochemical performance and great potential as an anode material for high-rate lithium-ion batteries. The enhanced electrochemical performance of the composite electrodes can be attributed to the small size of Li4Ti5O12 nanoparticles as well as the uniform distribution of N-doped carbon and TiN composite conductive structure on the surface and in the bulk of Li4Ti5O12 nanoparticles.
    Electrochimica Acta 06/2014; 132:230–238. DOI:10.1016/j.electacta.2014.03.007 · 4.50 Impact Factor
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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 04/2014; 54(1). DOI:10.1007/s11249-014-0304-5 · 2.15 Impact Factor
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    ABSTRACT: Hydrogenated-carbon nitride (CNx:H) films are prepared on ZrO2/Al2O3 ceramic substrate via the pyrolysis of ethylenediamine at 800-1000 degrees C. The microstructure of as-prepared CNx:H films has been analyzed, and their friction and wear behavior have been evaluated. Results show that nitrogen in as-prepared CNx:H films is incorporated into graphitic structure by substituting carbon positions. Increasing calcination temperature gives rise to a decrease of N/C ratio and an increase of relative intensity of C=C bonds in as-prepared CNx:H films. Besides, a small amount of N atoms in the crystal lattice of graphite is chemically bonded with C atoms to generate CNx compound, and the friction and wear behavior of CNx:H films on the composite ceramic substrate is closely related to their microstructure and chemical structure. Namely, CNx:H film sample obtained at 800 degrees C has the maximum N/C ratio of 0.13 but the poorest adhesion to composite ceramic substrate, while the one prepared at 950 degrees C has a lower N/C ratio and the highest adhesion to substrate. Moreover, CNx:H films formed on composite ceramic substrates with different surface roughness have similar friction coefficient (about 0.20) but different antiwear life. Particularly, N in as-prepared CNx:H films and Al in ZrO2/Al2O3 composite ceramic substrate chemically react to form N-Al bond, which contributes to increase the bonding strength between the films and the ceramic substrate thereby significantly improving wear resistance of the films. (c) 2013 Elsevier B.V. All rights reserved.
    Thin Solid Films 09/2013; 542:60-70. DOI:10.1016/j.tsf.2013.06.049 · 2.13 Impact Factor
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    ABSTRACT: A novel TiO2 (anatase) containing a large amount of single electron trapped oxygen vacancies (SETOV) was prepared by dehydration of titanic acid nanotubes. This novel TiO2 contains high concentration intrinsic defects in bulk structure, while its surface still remains the stoichiometric structure to protect them. And this novel TiO2 itself has the visible light absorption without any doping, so we call it as the third generation of TiO2. However, it is regretted that this novel TiO2 (A) only has photocatalytic activity under UV light irradiation, and was inactive for the visible light. The true reasons for this phenomenon were investigated by the transient IR absorption and photoluminescence spectra. Through constructing the foreign electron traps (PdO, PtO2), the photocatalytic oxidation of propylene under visible light irradiation was successfully achieved. The removal yield of propylene (C3H6) reached 7.6% and 28% on 2 wt.% PtO2/novel TiO2 and 2 wt.% PdO/novel TiO2, respectively. By comparison with the noble metal electron traps (Pt, Pd), we found that the effective foreign electron traps need to satisfy two conditions: (1) its work function should situate in the range of Eg(TiO2); (2) O2 adsorbes on it undissociatively. This work opens up a new route for the investigation of solar-energy-available TiO2.
    Chinese Science Bulletin 05/2013; 58(14). DOI:10.1007/s11434-013-5682-9 · 1.37 Impact Factor
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    ABSTRACT: The NiO loaded anatase TiO2 nanotubes have been successfully synthesized. It was found that NiO nanoparticles could prevent the nanotubular morphology from destruction during the dehydration of interlayered –OH groups of NTA and improve the electronic conductivity of TiO2 nanotubes. Galvanostatic battery testing showed that the NiO loaded anatase TiO2 nanotubes electrode exhibit excellent rate capability and good cycle performance. The enhanced performances can be attributed to its favorable tubular morphology and the better electrical contact between NiO and TiO2 nanotubes.
    Ionics 11/2012; 18(9). DOI:10.1007/s11581-012-0691-2 · 1.84 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; 259:824-830. DOI:10.1016/j.apsusc.2012.07.132 · 2.54 Impact Factor
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    ABSTRACT: Monodispersed and size-controlled Ag2S nanoparticles were synthesized successfully via a green and simple surfactant-free solventless thermolysis of silver xanthates as single-source precursors. As-prepared Ag2S nanoparticles were characterized by transmission electron microscopy, X-ray diffraction and Fourier transform infrared spectrometry. Moreover, a possible growth mechanism of Ag2S nanoparticles was proposed. It has been found that the size of Ag2S nanoparticles can be effectively controlled by changing the alkyl chain length of the precursors. Ag2S nanoparticles prepared from silver carnaubyl xanthate have the smallest mean diameter of 8.9±1.2 nm, while the same products obtained from silver hexadecyl xanthate and silver octyl xanthate have a larger mean diameter of 19.5±0.9 nm and 48.3±3.6 nm, respectively.
    Materials Letters 10/2012; 85:77–80. DOI:10.1016/j.matlet.2012.06.112 · 2.27 Impact Factor
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    ABSTRACT: Li4Ti5O12/TiN nanocomposites are fabricated through high-energy ball-milling of the mixture of spinel lithium titanate and TiN powder with different mass ratios of 100:1, 100:2, 100:4, and 100:8 (resultant nanocomposites are denoted as LTO–TiN-1B, LTO–TiN-2B, LTO–TiN-4B, and LTO–TiN-8B). All ball-milled samples exhibit markedly improved electrochemical properties than pristine Li4Ti5O12. Particularly, LTO–TiN-2B electrode has a high capacity of 130 mA h g−1 at a charge/discharge rate of 20C and the capacity retention was 85% after 1000 cycles at 10C, showing the best electrochemical performance and great potential as an anode material for high-rate lithium-ion batteries. The transmission electron microscopy and X-ray diffraction results indicate that amorphous TiN is generated on the surface of LTO. The improved electrochemical performance may be attributed to TiN which can significantly enhance the electronic conductivity of the nanocomposites.
    Journal of Power Sources 08/2012; 211:133–139. DOI:10.1016/j.jpowsour.2012.03.088 · 6.22 Impact Factor
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    ABSTRACT: Ionic liquid crystal (ILC), 1-methyl-3-hexadecylimidazolium tetrafluroborate, was synthesized. The tribological behavior of ILC was evaluated using a four-ball machine at 80 °C. X-ray photoelectron spectroscopic analysis shows that ILC takes part in tribochemical reactions to generate tribochemical products such as B2O3, FeF2, and/or FeF3, and amine which form a protective film on sliding steel surface, resulting in reduced friction and wear. Besides, ILC 1-methyl-3-hexadecylimidazolium tetrafluoroborate is completely transformed from solid state to liquid crystalline phase at 80 °C, which facilitates the ordered arrangement of its long alkyl chain on sliding steel surface and helps to improve the tribological properties. When the ILC is used as an additive of liquid paraffin (LP), it contributes to reduce friction and wear and increase the load-carrying capacity of the base stock both at room temperature and 80 °C. The reason might lie in that a small amount of F from ILC takes part in tribochemical reactions to generate tribochemical products that form a protective film on sliding steel surface, and friction-induced heat accelerates the transition of as-synthesized ILC to a mesophase and the ordered arrangement of its long alkyl chain on sliding steel surface, both resulting in improved load-carrying capacity and anti-wear ability of the ILC.
    Tribology Letters 04/2012; 46(1). DOI:10.1007/s11249-012-9917-8 · 2.15 Impact Factor
  • Xia Zhang · Pingyu Zhang · Zhishen Wu · Zhijun Zhang
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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. DOI:10.1007/s10853-011-6103-6 · 2.37 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. DOI:10.1021/am201856j · 6.72 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 10/2011; 212(2):327-331. DOI:10.1016/j.powtec.2011.06.005 · 2.27 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 05/2011; 13(5):2041-2047. DOI:10.1007/s11051-010-9958-6 · 2.28 Impact Factor
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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. DOI:10.1016/j.apsusc.2010.09.004 · 2.54 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. DOI:10.1111/j.1751-1097.2010.00808.x · 2.68 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.
    The Journal of Physical Chemistry C 05/2010; 114(22). DOI:10.1021/jp100697x · 4.77 Impact Factor
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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 05/2010; 64(10):1200-1203. DOI:10.1016/j.matlet.2010.02.050 · 2.27 Impact Factor