Wangchang Geng

Northwestern Polytechnical University, Xi’an, Liaoning, China

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Publications (31)45.66 Total impact

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    ABSTRACT: Flower-like Co3O4/Fe3O4 magnetic microspheres were prepared by coprecipitation of Fe2+ and Fe3+ in presence of flower-like Co3O4 microspheres as template. The preparation process included three steps: preparation of flower-like Co3O4 microspheres by hydrothermal method; immersion of Fe2+ and Fe3+ ions; coprecipitation in the presence of OH-. Rhodamine B (RhB) was chosen as model pollutants to investigate the photodegradation capacities of Co3O4/Fe3O4 magnetic microspheres. The results showed that the microspheres exhibited excellent degradation property and can be recycled to use again. After four times use the degradation efficiency was still above 90%.
    Functional Materials Letters 12/2013; 6(6):50052-. · 1.27 Impact Factor
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    ABSTRACT: The volume fraction of functionalized graphene nanoplatelets (GNPs) influencing on the thermal conductivities of GNPs/polyphenylene sulfide (GNPs/PPS) composites are investigated. Results reveal that a great improvement of the thermal conductivities with the addition of functionalized GNPs, and the thermal conductivity of the GNPs/PPS composite is 4.414 W/mK with 29.3 vol% functionalized GNPs, 19 times higher than that of the pure PPS matrix. The significantly high improvement of the thermal conductivities is ascribed to good thermal transmission through GNPs networks in the PPS matrix, following a thermal percolation behavior. Meantime, the GNPs have strong ability to generate continuous thermally conductive chains, and the formation of thermally conductive networks becomes much easier. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers
    Polymer Composites 11/2013; · 1.48 Impact Factor
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    ABSTRACT: NaCl-added mesoporous silica SBA-15 was prepared by a simple grind method which needs low energy cost. Humidity sensing property was studied. Study results indicated that NaCl-added material possesses higher humidity sensitivity. Its impedance changed more than four orders of magnitude when the relative humidity changed from 11% RH to 95% RH. From the viewpoint of economy, NaCl-added SBA-15 material which possesses high sensitivity and needs low energy cost is more suitable to be a promising humidity sensing material. Complex impedance spectra, the corresponding equivalent circuit, and bode diagrams were carefully analyzed to explore sensing mechanism.
    International Journal of Applied Ceramic Technology 10/2013; · 1.15 Impact Factor
  • Journal of Materials Science 08/2013; 48(15):5302-5308. · 2.16 Impact Factor
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    ABSTRACT: In this article, we present poly (methyl methacrylate)-b-polystyrene (PMMA-b-PS) with different block ratios and high molecular weight, which was synthesized by environmentally friendly seeded emulsion polymerization with 1,1-diphenylethylene (DPE) as a chain transfer agent. Polymerization kinetics in the first and second stage was investigated. Stable latex and homogeneous latex particles were obtained with the characterization of laser light scattering (LLS) and transmission electron microscopy (TEM). SEC and (1)H NMR revealed the successful preparation of block copolymers with high molecular weight and two different block ratios. The morphology of microphase separation of block copolymer thin films was investigated by AFM, and long-range order lamellar morphology was observed after vapor-annealing. The block copolymer with block ratio of almost 1:1 and higher molecular weight than that of previous PMMA-b-PS was sulfonated with acetyl sulfate, and the sulfonation was confirmed by FTIR, (1)H NMR, and TGA. Then, the sulfonated PMMA-b-PS was casted as membranes. The electrochemical impedance spectroscopy displayed that membranes possessed favorable proton conductivity and fine dimensional stability, and they could be candidates as proton exchange membranes.
    Journal of Colloid and Interface Science 06/2013; · 3.17 Impact Factor
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    ABSTRACT: Pore size of mesoporous materials is crucial for their surface grafting. This article develops a novel multifunctional microsphere with a large pore size mesoporous silica shell (ca. 10.3nm) and a magnetic core (Fe3O4), which is fabricated using cetyltrimethylammonium bromide (CTAB) as pore-forming agents, tetraethyl orthosilicate (TEOS) as silicon source through a sol-gel process. Compared with small pore size mesoporous silica magnetic microspheres (ca. 2-4nm), the large pore size one can graft 447mg/g amino groups in order to adsorb more heavy metal ions (Pb(2+): 880.6mg/g, Cu(2+): 628.3mg/g, Cd(2+): 492.4mg/g). The metal-loaded multifunctional microspheres could be easily removed from aqueous solution by magnetic separation and regenerated easily by acid treatment. The results suggest that the large pore size multifunctional microspheres are potentially useful materials for high effectively adsorbing and removing different heavy metal ions in aqueous solution.
    Journal of hazardous materials 03/2013; 254-255C:157-165. · 4.14 Impact Factor
  • Qing Yuan, Nan Li, Wangchang Geng, Yue Chi, Xiaotian Li
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    ABSTRACT: A simple and efficient method has been developed to fabricate core–shell structured Fe3O4@SiO2@meso-TiO2 nanocomposites with enhanced photocatalytic activity in this paper. The as-made core–shell structure is composed of a central magnetite core with a strong response to external fields, an interlayer of SiO2, and an outer layer of TiO2 nanocrystals with mesoporous structure. Fe3O4@SiO2 was obtained through a sol–gel process. To avoid magnetic loss caused by magnetite core phase transition and particle reunion, we adopt a mild synthetic method to get anatase shell instead of traditional high-temperature calcination. The structure of resulting composites was characterized and their photocatalytic activities were also tested. Fe3O4@SiO2@meso-TiO2 composite exhibits higher photocatalytic activities than Fe3O4@SiO2@solid-TiO2 for the degradation of rhodamine B in aqueous suspension. The excellent photocatalytic activities are ascribed to the high surface area and pore volume created by mesoporous anatase shell.
    Materials Research Bulletin. 09/2012; 47(9):2396–2402.
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    ABSTRACT: Highly ordered mesoporous carbon functionalized with carboxylate groups and magnetic nanoparticles has been successfully synthesized. By oxidative treatment using (NH(4))(2)S(2)O(8) and H(2)SO(4) mixed solution, numerous hydrophilic groups were created in the mesopores without destroying the ordered mesostructure of CMK-3. Through the in situ reduction in Fe(3+), magnetic nanoparticles were successfully introduced into the mesopores, resulting in the multifunctional mesoporous carbon Fe-CMK-3. The obtained hybrid carbon material possesses ordered mesostructure, high Brunauer-Emmett-Teller (BET) surface area up to 1013 m(2)/g, large pore volume of about 1.16 cm(3)/g, carboxylic surface, and excellent magnetic property. When used as an adsorbent, Fe-CMK-3 exhibits excellent performances for removing toxic organic compounds from waster-water, with a high adsorption capacity, an extremely rapid adsorption rate, and an easy magnetically separable process. In the case of requiring emergency removal of large amount of organic pollutants in aqueous, the hybrid carbon adsorbent would be an ideal choice.
    Journal of Colloid and Interface Science 03/2012; 369(1):366-72. · 3.17 Impact Factor
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    ABSTRACT: One-dimensional (1D) magnetic Fe(3)O(4)/P(GMA-DVB) peapod-like nanochains have been successfully synthesized by magnetic-field-induced precipitation polymerization using Fe(3)O(4) as building blocks and P(GMA-DVB) as linker. The Fe(3)O(4) microspheres without surface modification can be arranged with the direction of the external magnetic field in a line via the dipolar interaction between Fe(3)O(4) microspheres and linked permanently via P(GMA-DVB) coating during precipitation polymerization. The length of peapod-like nanochains can be controlled by magnetic field intensity, and the thickness of polymer shell can be tuned by the amount of monomers. Magnetic measurement revealed that these 1D peapod-like nanochains showed highly magnetic sensitivity. In the presence of magnetic field, 1D magnetic Fe(3)O(4)/P(GMA-DVB) peapod-like nanochains can be oriented and aligned along the direction of external magnetic field.
    Journal of Colloid and Interface Science 02/2012; 374(1):339-44. · 3.17 Impact Factor
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    ABSTRACT: Mesoporous Fe2O3/SiO2 composites with various Fe/Si molar ratios were synthesized via hydrothermal route and then studied as humidity sensor materials. The best result is obtained for the sample with a Fe/Si molar ratio of 0.5, which exhibits high humidity sensitivity, rapid response and recovery, small hysteresis and excellent linearity. The impedance of the sensor varies more than four orders of magnitude during the whole relative humidity (RH) from 11 to 95%. The response time and recovery time of the sensor is about 20 and 40s, respectively. These results make our product a good candidate in fabricating high performance humidity sensors.
    Sensors and Actuators B-chemical - SENSOR ACTUATOR B-CHEM. 01/2011;
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    ABSTRACT: We present a systemic study on the structural, thermal and magnetic properties of Zn1−xMnxO nanoparticles synthesized by a combustion method with heavily Mn doping concentrations x=0.05, 0.15 and 0.25. The structural evolutions in relation to the possible variation of the Mn oxidation state and dopant induced tiny Zn2MnO4/Mn2O3 and ZnMnO3/MnO2 impurities, which have not been detected by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM), were investigated by means of X-ray photoelectron spectroscopy (XPS), Raman scattering spectra, thermo-gravimetric analysis (TGA) and magnetic measurements. It is evidenced that the optimal Mn concentration x in ZnO to grow single phase Zn1−xMnxO should be below the cation percolation threshold xp (about 0.125), which is the basis to form real diluted magnetic semiconductors (DMSs).
    Journal of Magnetism and Magnetic Materials 01/2011; 323(18):2374-2379. · 1.83 Impact Factor
  • WangChang Geng, Lei Zhang, Paul V. Bernhardt
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    ABSTRACT: Mediated electrochemistry of dimethyl sulfoxide reductase from Rhodobacter capsulatus (DMSOR) which is immobilized on a bare glassy carbon (GC) electrode and a carbon nanotube (CNT)-modified GC electrode was studied using the Co complex (trans-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane-6,13-diamine)cobalt(III) ([Co(trans-diammac)]3+) as a mediator. The cyclic voltammograms of different electrodes were carried out at different substrate (DMSO) concentrations. The results demonstrated that the catalytic current was increased by employing CNT as a promoter. KeywordsDMSO reductase-carbon nanotubes-electrochemistry-mediator
    Science China-Chemistry 01/2010; 53(12):2560-2563. · 1.33 Impact Factor
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    ABSTRACT: Nickel oxide (NiO) doped polypyrrole (PPy) was encapsulated in mesoporous SBA-15. All of the synthesized samples were characterized by infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. They were investigated as humidity-sensor materials at room temperature. The sensor showed excellent humidity sensitivity in the relative humidity range 11–95%. The humidity-sensing properties were very much improved by encapsulation of the NiO-doped PPy into mesoporous silica SBA-15. Finally, the sensitivity mechanism was investigated by direct-current (dc) and alternating-current (ac) analysis. The dc circuit with the instantaneous polarity reversion method was designed by us to study the dc response in different humidity environments. The conductive mechanism was established through the dc and ac investigation, and the conductive particles were identified as ions and electrons. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
    Journal of Applied Polymer Science 11/2009; 115(6):3474 - 3480. · 1.40 Impact Factor
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    ABSTRACT: K2CO3-SBA-15 with different K2CO3 content was prepared by thermal dispersion. The structures of resultant powders were characterized by XRD, N2 adsorption and IR. The humidity sensing properties of the powders were also investigated. Compared with pure SBA-15, K2CO3-SBA-15 shows improved humidity sensing properties and the introducing level of K2CO3 has a great influence on the humid sensitivity of K2CO3-SBA-15 composites. The optimal mixing ratio was K2CO3-SBA-15 (0.8 g/g), which exhibited excellent linearity in the whole range of 11–95%RH, a resistance variation of about five orders of magnitude, and a rapid response time and recovery time about 15 and 50 s, respectively. The mechanism of the humidity sensitive properties was also discussed.
    Applied Surface Science 10/2009; 256(1):280–283. · 2.11 Impact Factor
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    ABSTRACT: A simple chemical method was employed to form Fe2+ doped polypyrrole (PPY) by the introduction of hydrated ferric chloride (FeCl3·6H2O) during the polymerization of pyrrole, where FeCl3·6H2O played a role of oxidant for the polymerization and the in situ forming reduced product (FeCl2·2H2O) was well doped in PPY. The resultant Fe2+ doped PPY species were characterized by using various techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and field emission scanning electronic microscope (FE-SEM). Humidity-sensitive properties of the samples were also examined. The Fe2+ doped PPY exhibited a fast response to humidity change (about 20s), in which great changes of more than three orders (nearly four) of magnitude in impedance was observed when relative humidity was varied over the whole range. The improved properties may be related to the presence of the hydrophilic Fe2+, and a possible mechanism was also provided.
    Synthetic Metals - SYNTHET METAL. 01/2009; 159(23):2469-2473.
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    ABSTRACT: Li-doped 3D periodic mesoporous silica SBA-16 has been successfully prepared and investigated as humidity sensor material. After doping of 10% (wt) lithium chloride, mesoporous silica SBA-16 showed significant change in impedance of more than three orders of magnitude over almost the whole humidity range (11–95%RH), with fast response time (about 25 s), and relatively low hysteresis (about 4%). The comprehensive affections of the 3D mesoporous structure, highly dispersed uniform morphology, hydrophilic behavior of triblock copolymer surfactant F108, and the doped Li+ maybe make a great contribution to the improvement in the humidity sensitive property. A possible mechanism was also provided to explain the humidity sensitive properties.
    Sensors and Actuators B: Chemical. 01/2009;
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    ABSTRACT: (MgO)x(ZnO)1−x materials have been synthesized using mesoporous carbon as template. By increasing the MgO content in the materials greater than 25%, the (MgO)x(ZnO)1−x materials began to form the mesoporous structure. Pore size distribution curves indicated that the BJH pore diameter decreased with increasing MgO content. In photoluminescence spectra, all the samples except pure ZnO showed both the band-edge emission and the deep-level emission (green band). It was interesting to note that the UV emission peak energy (EUV) had a red-shift of about 48 meV at the low MgO content range of 0–25%, while when the MgO content varied from 25 to 75%, the EUV displayed a blue-shift of about 36 meV to the higher energy direction. The optical band gap (Eg) of the (MgO)x(ZnO)1−x calculated from the absorption spectra was far smaller than that in literature, and this may be related to the formation of mesoporous structure.
    Materials Research Bulletin. 01/2008; 43(3):601-610.
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    ABSTRACT: Polypyrrole (PPY) materials were prepared by using chemical polymerization at room temperature for 96h. A resistive-type humidity sensor was fabricated on a ceramic substrate with Ag–Pd interdigital electrodes. The humidity-sensing mechanism of the polypyrrole materials was discussed in terms of capacitance, direct current, complex impedance and dielectric loss properties. The discussion on the sensing mechanism indicated that not only electrons or ions but also dipoles contributed to the conduction in the whole relative humidity range.
    Sensors and Actuators B-chemical - SENSOR ACTUATOR B-CHEM. 01/2008; 131(2):687-691.
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    ABSTRACT: P-SBA-15 and A-SBA-15 and LiCl-A-SBA-15 (X) were prepared and characterized by IR and XRD. These different characteristic results suggest that these materials have the similar mesoporous structure. The dopant of LiCl improves the pure A-SBA-15 sorption ability to moisture. A resistive-type humidity sensor is fabricated on a ceramic substrate with Ag-Pd interdigital electrodes. The testing results on humidity sensing properties show that the material with 15 wt.% LiCl as a dopant has the best sensing properties to humidity. The discussion on the sensing principle suggests that the protons are the domination carrier in a low humidity range and ions in a high humidity range. The complex impedance plots support this discussion result.
    Sensors and Actuators B: Chemical. 01/2008;
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    ABSTRACT: In this paper, we prepared polypyrrole (PPY) films using a chemical method at different polymerization times. Their structure and morphology were characterized through X-Ray powder diffraction (XRD), IR, and scanning electron microscope (SEM). The humidity sensors were made by a coating membrane method. We studied the humidity sensing properties of the PPY-x films (the letter ‘x’ denotes the polymerization time and it was 4, 24, or 96h). It was found that the humidity sensing properties of PPY could be improved greatly by extending the polymerization time. According to our experiment results, we predict that the humidity sensing properties of conducting polymers could be improved by increasing their crystallinity degree.
    Sensors and Actuators B-chemical - SENSOR ACTUATOR B-CHEM. 01/2007; 125(1):114-119.

Publication Stats

94 Citations
45.66 Total Impact Points

Institutions

  • 2010–2013
    • Northwestern Polytechnical University
      • School of Science
      Xi’an, Liaoning, China
  • 2004–2012
    • Jilin University
      • • Department of Material Science and Engineering
      • • Alan G. MacDiarmid Institute
      Changchun, Jilin Sheng, China