Jiangsu Province Key Laboratory of Fine Petrochemical Industry

Changzhou, China

Jiangsu Province Key Laboratory of Fine Petrochemical Industry

Changzhou, China

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Wang M.-H.,Changzhou University | Wang M.-H.,Jiangsu Province Key Laboratory of Fine Petrochemical Industry | Zhang B.,Changzhou University | Zhou F.,Changzhou University
Journal of Sol-Gel Science and Technology | Year: 2014

CaCu3Ti4O12 (CCTO) powders were prepared via a non-hydrolytic sol-gel (NHSG) method by using acetylacetone as chelating agent and ethylene glycol as solvent. The samples were characterized by TG-DSC, Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscope. The dielectric properties of ceramics were also measured. The pure perovskite-like CCTO powders were obtained by heat treatment at 800 °C for 2 h. The average particle sizes of CCTO powders calcined at 800 °C were approximately 350-450 nm. The samples sintered at 1,000 °C showed the mean grain size of 2.5-4 μm. Specially, the ceramics exhibited high dielectric constant (1.19 × 105-1.40 × 105) and low dielectric loss (0.051-0.1) in the temperature range of 30-110 °C. Moreover, with the NHSG method the period of synthesis process was greatly shortened. © 2014 Springer Science+Business Media New York.


Wang M.-H.,Changzhou University | Wang M.-H.,JiangSu Province Key Laboratory of Fine Petrochemical Industry | Ma X.-Y.,Changzhou University | Zhang B.,Changzhou University | Zhou F.,Changzhou University
Journal of Electronic Materials | Year: 2014

CaCu3Ti4O12 (CCTO) powders coated with carbon were synthesized by using a high-energy ball milling method. The obtained samples were characterized by x-ray diffraction, transmission electron microscopy and scanning electron microscopy. The carbon-coated CCTO particles had a rough surface, which resulted from the growth of the carbon coating on the CCTO particles. It was found that the CCTO phase was observed as the major phase and no reaction occurred between the carbon and CCTO during the sintering process. The grain size of the CCTO ceramics decreased with the increase in carbon content, which indicated that carbon inhibits grain growth of CCTO ceramics. Specially, the dielectric constant decreased with the increase in carbon content. And CCTO1 ceramic (mass ratio of CCTO: carbon = 10:1) showed a lower dielectric constant (3.74 × 104), with the dielectric loss value (0.04) much lower than that of CCTO at 20°C (10 k Hz). © 2014 The Minerals, Metals & Materials Society.


Wang M.,Changzhou University | Wang M.,Jiangsu Province Key Laboratory of Fine Petrochemical Industry | Zhang B.,Changzhou University | Li G.,Changzhou University | Yao C.,Changzhou University
Journal Wuhan University of Technology, Materials Science Edition | Year: 2014

The effect of Al2O3 doping on the microstructure and electrical properties of the ZnO-Pr6O11-Co 3O4-MnCO3-Y2O3 system was investigated in the range of 0.0-0.1mol%. The results reveal that Al 2O3 doping has slight influence on the densification process. The microstructure of the ceramics comprises of ZnO phase, ZnAl 2O4 spine phase and Pr-rich phases. The addition of Al2O3 greatly affects the electrical properties. The varistor voltage (E 1mA/cm 2) of ZPCMYAl samples decreases over a wide range from 5 530 V/cm to 1 844 V/cm with the increasing Al 2O3 content. The nonlinear exponent(α) increases with the increasing Al2O3 content to 0.01mol%, whereas it is decreased by the further doping. The ZPCMYAl-based varistor ceramics with 0.01mol% Al2O3 exhibit the best electrical properties, with the nonlinear exponent (α) attaining the highest value of 33.4 and the lowest leakage current of 2.7 μA. The capacitance-voltage (C-V) measurement shows that the donor density (N d) at the grain boundaries increase from 1.58×1018 to 3.15×10 18 cm-3, the barrier height (φ b) increases from 1.60 to 2.36 eV, and the depletion layer width (t) decreases from 24.9 to 21.6 nm. © 2014 Wuhan University of Technology and Springer-Verlag Berlin Heidelberg.


Chen T.,Changzhou University | Wang M.-H.,Changzhou University | Wang M.-H.,Jiangsu Province Key Laboratory of Fine Petrochemical Industry | Ma X.-Y.,Changzhou University
Journal of Electronic Materials | Year: 2016

α-Bi2Mo3O12 and γ-Bi2MoO6 powders have been successfully fabricated via a sol–gel method starting from bismuth nitrate and ammonium molybdate. The as-synthesized samples were characterized by x-ray powder diffraction analysis, thermogravimetry and differential thermogravimetry, scanning electron microscopy, and ultraviolet–visible (UV–Vis) absorption spectroscopy. The results indicated the formation of α-Bi2Mo3O12 and γ-Bi2MoO6 powders in acidic (pH 5) and alkaline (pH 9) conditions, respectively. α-Bi2Mo3O12 exhibited irregular shape, while γ-Bi2MoO6 showed approximately flake-like morphology. The bandgap of pure α-Bi2Mo3O12 and γ-Bi2MoO6 was estimated to be about 2.83 eV and 2.85 eV, respectively, according to UV–Vis studies. The slight shift of the absorption edge towards longer wavelength for α-Bi2Mo3O12 indicated a decrease of the optical bandgap. Photocatalytic experiments showed that γ-Bi2MoO6 exhibited higher photodegradation activity of methylene blue compared with α-Bi2Mo3O12. © 2016, The Minerals, Metals & Materials Society.


Wang M.-H.,Changzhou University | Wang M.-H.,JiangSu Province Key Laboratory of Fine Petrochemical Industry | Zhang B.,Changzhou University | Zhou F.,Changzhou University
Journal of Electronic Materials | Year: 2014

Silica was homogeneously coated on the surface of CaCu3Ti 4O12 (CCTO) particles via the sol-gel method. The obtained powders were characterized by x-ray diffraction analysis, Fourier-transform infrared spectroscopy, transmission electron microscopy (TEM), energy-dispersive spectroscopy, scanning electron microscopy, and zeta potential analysis. The results demonstrate that there were silica layers on the surface of the CCTO particles. Physical and dielectric properties of silica-coated CCTO were also studied. TEM imaging showed that the thickness of the silica layer on the CCTO particles was about 20 nm to 35 nm. The specimen coated with 1.0 wt.% silica showed the maximum relative density of 96.7% with high dielectric constant (12.78 × 104) and low dielectric loss (0.005) at 20°C after sintering at 1000°C for 6 h. © 2014 TMS.


Wang M.-H.,Changzhou University | Wang M.-H.,JiangSu Province Key Laboratory of Fine Petrochemical Industry | Ma X.-Y.,Changzhou University | Jiang W.,Changzhou University
Journal of Electronic Materials | Year: 2014

Doped ZnO nanopowders were successfully prepared by a novel wet-chemical method in the presence of sucrose and NH4NO3. Several analytic techniques such as x-ray diffraction, transmission electron microscopy and scanning electron microscope were used to make characterizations of the products. The results suggested that the doped ZnO powders were approximately spherical in shape with the diameter of the particles of about 25–45 nm. The as-synthesized powders were consolidated into dense varistors discs by compaction, sintering and evaluated for their electrical characteristics. Leakage current density was found to be about 0.93 μA/cm2, and non-linear coefficients as high as 46.5 and breakdown field of about 595.8 V/mm were measured. The experimental results showed the advantage of the addition of sucrose and NH4NO3 for controlling grain size and improving electrical performance of the varistors. © 2014, The Minerals, Metals & Materials Society.


Wang M.,Changzhou University | Wang M.,JiangSu Province Key Laboratory of Fine Petrochemical Industry | Zhang B.,Changzhou University | Zhou F.,Changzhou University
Journal of Materials Science: Materials in Electronics | Year: 2014

The CaCu3Ti4O12 (CCTO) powders were prepared via a sol-gel method using oleic acid (OA) as surfactant. The obtained samples were characterized by thermogravimetric/differential scanning calorimeter Fourier transform-infrared spectroscopy, X-ray diffraction (XRD) and scanning electron microscope, the relative density and the dielectric properties of the ceramics were also investigated. The XRD patterns confirm the formation of CCTO crystal phase and no new peaks appeared whether the dispersant was added or not. The dispersibility of the CCTO powders is improved by adding OA as surfactant. The CCTO prepared without surfactant contains particles of various sizes ranging from 200 to 250 nm whereas the CCTO prepared with OA shows uniform particle size about 120-150 nm. The CCTO ceramics prepared with OA has higher dielectric constant (199484) and lower dielectric loss (0.0977) at 25 °C (10 kHz). © 2014 Springer Science+Business Media New York.

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