10 results on '"An, Zhiguo"'
Search Results
2. Bismuth layer‐structured ferroelectrics with non‐sheet‐like polyhedral microstructures.
- Author
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He, Xiang, Chen, Chen, Zeng, Huarong, Li, Yongxiang, Yang, Qunbao, and Yi, Zhiguo
- Subjects
FERROELECTRIC crystals ,MICROSTRUCTURE ,BISMUTH ,HYSTERESIS loop ,CURIE temperature ,FERROELECTRIC ceramics - Abstract
Bismuth layer‐structured ferroelectrics (BLSFs) are promising candidates for a variety of applications because of their high Curie temperature and environmentally benign nature as compared to their lead contained counterparts. Featured by the mica‐like grain growth habit and spontaneous polarization along crystallographic a‐b plane, it is difficult to obtain excellent ferroelectric properties for most of the BLSFs fabricated by the conventional ceramic route. Herein, a new approach is reported to obtain Bi2WO6 and Bi4Ti3O12 BLSF ceramics with non‐sheet‐like polyhedral microstructures. The intriguing ferroelectric hysteresis behavior, dielectric tunability, and domain structures are successfully observed. The Bi2WO6 ceramic with a unique single‐domain structure in each grain shows a typical ferroelectric polarization‐electric field hysteresis loop with a remnant polarization of ~17.8 μC cm−2 and a coercive field of ~43 kV cm−1. These values have never been obtained in Bi2WO6 ceramics with sheet‐like microstructure. The Bi4Ti3O12 ceramic with irregular‐shaped and curved tiny domains exhibits an antiferroelectric‐like behavior, which is significantly different from the reported Bi4Ti3O12 counterparts that have plate‐like anisotropic grains. The present study would stimulate microstructure design and property modulation for other layer‐structured materials. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
3. Structural Characterization and Optical Properties of Perovskite ZnZrO3 Nanoparticles
- Author
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Talaat Al-Kassab, Yangyang Li, Zhiguo Liu, Jianmin Zhu, Xinhua Zhu, and Jun Zhou
- Subjects
Tetragonal crystal system ,Crystallinity ,Materials science ,Band gap ,Materials Chemistry ,Ceramics and Composites ,Analytical chemistry ,Mineralogy ,Nanoparticle ,Selected area diffraction ,Microstructure ,High-resolution transmission electron microscopy ,Perovskite (structure) - Abstract
Perovskite ZnZrO3 nanoparticles were synthesized by hydrothermal method, and their microstructures and optical properties were characterized. The crystallinity, phase formation, morphology and composition of the as-synthesized nanoparticles were characterized by X-ray diffraction (XRD), selected area electron diffraction (SAED), high-resolutiontransmission electron microscopy (HRTEM), and energy-dispersive X-ray (EDX) spectroscopy analysis, respectively. TEM images demonstrated that the average particle size of the ZnZrO3 powders was increased with increasing the Zn/Zr molar ratios in the precursors, and more large ZnZrO3 particles with cubic morphology were observed at high Zn/Zr molar ratios. In addition, the phase structures of the ZnZrO3 particles were also evolved from a cubic to tetragonal perovskite phase, as revealed by XRD and SAED patterns. HRTEM images demonstrate that surface structures of the ZnZrO3 powders synthesized at high Zn/Zr molar ratios, are composed of corners bound by the {100} mini-facets, and the surface steps lying on the {100} planes are frequently observed, whereas the (101) facet isoccasionally observed. The formation of such a rough surface structure is understood from the periodic bond chain theory. Quantitative EDX analyses demonstrated that the atomic concentrations (at.%) of Zn:Zr:O in the particles were 20.70:21.07:58.23, as close to the composition of ZnZrO3. In the optical spectra, a significant red shift of the absorption edges (for the ZnZrO3 nanopowders) from UV to visible region (from 394 to 417 nm) was observed as increasing the Zn/Zr molar ratios in the precursors, which corresponds to that the band gap energies of the ZnZrO3 nanopowders can be continuously tuned from 3.15 to 2.97 eV. This opens an easy way to tune the band gap energies of the ZnZrO3 nanopowders.
- Published
- 2014
4. Microwave Sintering of Nanocrystalline Ni1−xZnxFe2O4Ferrite Powder and Their Magnetic Properties
- Author
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Jian-jun Li, Yin Liu, Mingxu Zhang, Tai Qiu, Zhiguo Yi, and Fanfei Min
- Subjects
Materials science ,Metallurgy ,Resonance ,chemistry.chemical_element ,Zinc ,Low frequency ,Microstructure ,Grain size ,Nanocrystalline material ,chemistry ,visual_art ,Materials Chemistry ,Ceramics and Composites ,visual_art.visual_art_medium ,Ferrite (magnet) ,Ceramic - Abstract
Nanocrystalline Ni1−xZnxFe2O4 (0 ≤ x ≤ 1.0) powder with grain size of 30 nm was prepared using the spraying-coprecipitation method. The obtained nanocrystalline Ni1−xZnxFe2O4 powder was sintered using conventional and microwave sintering techniques. The results show that the microstructure and magnetic properties of the sintered samples are obviously improved by microwave sintering of nanocrystalline Ni1−xZnxFe2O4 ferrite powder. The initial permeability of Ni1−xZnxFe2O4 ferrite increases with the increase in zinc concentration, although its resonance frequencies shift from high frequency to low frequency. The maximum initial permeability for microwave-sintered Ni0.4Zn0.6Fe2O4 ceramic obtained at the temperature of 1170°C for 30 min reaches up to 360.9, and its resonance frequency is ~10 MHz. It may be attributed to the nanocrystalline Ni1−xZnxFe2O4 raw powder as well as the microwave sintering process, which results in a synergistic effect on improvement of the microstructure and magnetic properties.
- Published
- 2012
5. Elongation of α-SiC Particles in Spark Plasma Sintered α-SiAlON/α-SiC Composites
- Author
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Yu Zhou, Zhiguo Zhang, Feng Ye, and Limeng Liu
- Subjects
Sialon ,Toughness ,Fracture toughness ,Materials science ,Flexural strength ,Materials Chemistry ,Ceramics and Composites ,Spark plasma sintering ,Plasma ,Composite material ,Elongation ,Microstructure - Abstract
α-SiAlON/α-SiC composites with 0–40 wt%α-SiC were synthesized by spark plasma sintering for 5 min at 1800°C under 20 MPa pressure. A self-reinforcing microstructure with both elongated α-SiAlON and α-SiC grains, was formed. Flexural strength and fracture toughness were significantly improved due to the in situ reinforcement. High fracture toughness up to 8.2 MPa·m1/2 was obtained in the 40 wt% SiC composition.
- Published
- 2011
6. Optical, electrical, and photoelectric properties of nitrogen‐doped perovskite ferroelectric BaTiO3 ceramics.
- Author
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Long, Peiqing, Chen, Chen, Pang, Dongfang, Liu, Xitao, and Yi, Zhiguo
- Subjects
PEROVSKITE ,FERROELECTRIC materials ,BARIUM titanate ,DIELECTRIC properties ,MICROSTRUCTURE - Abstract
Nitrogen‐doped BaTiO3 (BT) ceramics were produced by the solid‐state reaction method in conjunction with ammonia gas treatment. The optical absorption spectra results show that the bandgap of BT ceramic is narrowed after N‐doping, suggesting that the N‐doping is an effective route to increase light absorption. Polar properties measurements indicate that the ferroelectricity of BT ceramic is well maintained after the N‐doping. In addition, the electric‐field–induced strain is prominently improved to ~0.8% after N‐doping, a value superior to that of PZT. Furthermore, the influence of N‐doping on photoelectric properties of BT ceramics was also investigated. Large increase in photoconductivity and fast response to light illumination conditions were observed in N‐doped BT ceramics. This work provides a novel route to enhance the (photo)electric properties of ferroelectric materials. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
7. Microstructure and Mechanical Properties of Spark Plasma Sintered TaC0.7 Ceramics
- Author
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Zhang Zhiguo, Zhou Yu, Ye Feng, and Liu Limeng
- Subjects
Materials science ,Diffusion ,chemistry.chemical_element ,Plasma ,Microstructure ,Phase formation ,Fracture toughness ,chemistry ,visual_art ,Materials Chemistry ,Ceramics and Composites ,visual_art.visual_art_medium ,Lamellar structure ,Ceramic ,Composite material ,Carbon - Abstract
The TaC0.7 composition was spark plasma sintered (SPS) at 1600°–1900°C using TaC and Ta as the starting powders. Densification process, phase evolution, microstructure development, and the mechanical properties of the composites were investigated. The results indicated that the TaC0.7 composition could be SPS to >95% of theoretical density in 5 min at 1600°C or above. The phase formation was associated with carbon diffusion from the starting particles TaC to Ta to form Ta2C and Ta6C5 as intermediate phases, and subsequently the equilibrium phases of TaCy and ζ-Ta4C3−x. The presence of lamellar ζ-Ta4C3−x regions enhanced the flexure strength (up to 972 MPa) and fracture toughness (up to 13.8 MPa·m1/2).
- Published
- 2010
8. Microwave Sintering of Nanocrystalline Ni1− x Zn x Fe2 O4 Ferrite Powder and Their Magnetic Properties.
- Author
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Liu, Yin, Yi, Zhiguo, Li, Jian ‐ jun, Qiu, Tai, Min, Fan ‐ fei, Zhang, Ming ‐ xu, and Joy, P.
- Subjects
- *
NANOCRYSTALS , *SINTERING , *MICROSTRUCTURE , *CERAMICS , *RESONANCE - Abstract
Nanocrystalline Ni1− x Zn x Fe2 O4 (0 ≤ x ≤ 1.0) powder with grain size of 30 nm was prepared using the spraying-coprecipitation method. The obtained nanocrystalline Ni1− x Zn x Fe2 O4 powder was sintered using conventional and microwave sintering techniques. The results show that the microstructure and magnetic properties of the sintered samples are obviously improved by microwave sintering of nanocrystalline Ni1− x Zn x Fe2 O4 ferrite powder. The initial permeability of Ni1− x Zn x Fe2 O4 ferrite increases with the increase in zinc concentration, although its resonance frequencies shift from high frequency to low frequency. The maximum initial permeability for microwave-sintered Ni0.4 Zn0.6 Fe2 O4 ceramic obtained at the temperature of 1170°C for 30 min reaches up to 360.9, and its resonance frequency is ~10 MHz. It may be attributed to the nanocrystalline Ni1− x Zn x Fe2 O4 raw powder as well as the microwave sintering process, which results in a synergistic effect on improvement of the microstructure and magnetic properties. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
9. Elongation of α-SiC Particles in Spark Plasma Sintered α-SiAlON/α-SiC Composites.
- Author
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Limeng Liu, Feng Ye, Zhiguo Zhang, and Yu Zhou
- Subjects
SILICON carbide ,MECHANICAL behavior of materials ,METALLIC composites ,SINTERING ,MICROSTRUCTURE ,METAL fractures - Abstract
α-SiAlON/α-SiC composites with 0-40 wt% α-SiC were synthesized by spark plasma sintering for 5 min at 1800°C under 20 MPa pressure. A self-reinforcing microstructure with both elongated α-SiAlON and α-SiC grains, was formed. Flexural strength and fracture toughness were significantly improved due to the in situ reinforcement. High fracture toughness up to 8.2 MPa ∙m
1/2 was obtained in the 40 wt% SiC composition. [ABSTRACT FROM AUTHOR]- Published
- 2011
- Full Text
- View/download PDF
10. Microstructure and Mechanical Properties of Spark Plasma Sintered TaC0.7 Ceramics.
- Author
-
Liu Limeng, Ye Feng, Zhou Yu, and Zhang Zhiguo
- Subjects
CERAMIC materials ,TANTALUM isotopes ,FUSION reactors ,METAL fractures ,MICROSTRUCTURE ,SINTERING ,SPECTRUM analysis - Abstract
The TaC
0.7 composition was spark plasma sintered (SPS) at 1600°-1900°C using TaC and Ta as the starting powders. Densification process, phase evolution, microstructure development, and the mechanical properties of the composites were investigated. The results indicated that the TaC0.7 composition could be SPS to >95% of theoretical density in 5 min at 1600°C or above. The phase formation was associated with carbon diffusion from the starting particles TaC to Ta to form Ta2 C and Ta6 C5 as intermediate phases, and subsequently the equilibrium phases of TaCy and ζ-Ta4 C3− x . The presence of lamellar ζ-Ta4 C3− x regions enhanced the flexure strength (up to 972 MPa) and fracture toughness (up to 13.8 MPa·m1/2 ). [ABSTRACT FROM AUTHOR]- Published
- 2010
- Full Text
- View/download PDF
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