Papers by Author: Hao Wang

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Authors: Zhou Fang, Zheng Yi Fu, Hao Wang, Wei Min Wang, Qing Jie Zhang
Abstract: A novel approach was developed to prepare Ni-coated TiB2 cermet. Fine Ni particles with mean particle size of about 80 nm were impacted onto coarse TiB2 particles having a mean size of about 5 μm to form Ni-coated TiB2 powder by Hybridization. The conventional blended TiB2-Ni powder, as well as Ni-coated TiB2 powder, was sintered by hot pressing (HP) method and Spark Plasma Sintering (SPS) method. Compared with the conventional blended TiB2-Ni cermet, particle features and mechanical properties of the Ni-coated TiB2 cermet were investigated. The microstructure analysis reveals that the thickness of Ni film is around 4 nm. It is concluded that the mechanical properties of Ni-coated TiB2 cermet are superior to the blended TiB2-Ni cermet.
Authors: Ding Peng, Hao Wang, Wei Min Wang, Yu Cheng Wang, Zheng Yi Fu
Abstract: In this paper, a carbothermal reduction and nitridation (CRN) synthesis for cubic aluminum oxynitride (γ-AlON) powders is reported. The CRN reaction was conducted via a two-step synthesis procedure at a heating rate of 100 °C/min. In the first step, the mixture of fine γ-Al2O3 and soluble starch was annealed at 1550~1580 °C for different duration. It is found that the mixture of α-Al2O3 and AlN with an appropriate ratio can be obtained by CRN reaction. The content of AlN in mixture is closely related with the reaction condition. In the second step, the as-received mixture of α-Al2O3 and AlN was heat-treated at 1700 °C for 10 min. The single phase γ-AlON powders with particle size less than 3 µm were obtained.
Authors: Kui Bao Zhang, Zheng Yi Fu, Jin Yong Zhang, Wei Min Wang, Hao Wang, Yu Cheng Wang, Qing Jie Zhang
Abstract: The equiatomic multicomponent CoCrFeNiCuAl high-entropy alloy powder was synthesized by mechanical alloying. The effects of milling time and heat treatment on the structure and morphology of the ball milled alloy were investigated. Single BCC solid solution structure appears when the alloy is ball milled more than 30h. The 60h ball milled alloy powder shows a mean particle size of 3 μm, which is actually hard agglomerations of nanosized crystals with crystalline size less than 10nm. The 60h ball milled alloy exhibits good chemical homogeneity. The single BCC solid solution structure transforms to a BCC and a FCC phases when annealled at 600°C for 1h, which can be attributed to the supersaturatable solid solution formation during the mechanical alloying process.
Authors: Tie Kun Jia, Wei Min Wang, Zheng Yi Fu, Fei Huang, Hao Wang
Abstract: SnO2 nanocrystals with various morphologies were synthesized via a hydrothermal method assisting by the surfactant CTAB. The morphologies of the products were significantly dependent on the synthesis conditions. The products were characterized by X-ray diffraction (XRD) and field scanning electron microscopy (FESEM).The results showed products SnO2 nanoparticles and spheres like structure assembled with nanocones were obtained by varying the dosage of CTAB and the concentration of NaOH. The forming process of SnO2 sphere like structure was discussed and the proposed mechanism was put forward in this work.
Authors: Yan Xiong, Zheng Yi Fu, Hao Wang
Abstract: Effect of adding up to 5wt% CaF2 on the densification and microstructural development of hot pressed aluminum nitride (AlN) was investigated. SEM investigation showed that the grain size of the sintered sample decreases with the increasing content of CaF2. Secondary-phase evolution paths converge from CA6 to CA phase above 1650°C. TEM micrographs showed that formed secondary phases could evaporate from sintered bodies at higher temperatures in the carbon-containing nitrogen atmosphere and the residuals were mainly distributed at triple grain junctions, keeping direct connections of AlN grains. Translucnet AlN ceramics were prepared using CaF2 additive sintered at 1850°C for 5 h.
Authors: Hua Jun Sun, Wen Chen, Xiao Fang Liu, Qing Xu, Jing Zhou, Hao Wang
Abstract: xPb(Ni1/3Nb2/3)O3-yPb(Mn1/3Nb1/3Sb1/3)O3-(1-x-y)Pb(Zr0.48Ti0.52)O3 ceramics have been prepared by a columbite two-step method. NiNb2O6, MnNb2O6 and MnSb2O6 were used as precursors to produce the pseudoquintnary system ceramics. X-ray diffraction (XRD) results indicate that the pseudoquintnary system ceramics have a single-phase perovskite structure. The piezoelectric and dielectric properties of the ceramics were investigated as functions of x or y. The addition of Pb(Ni1/3Nb2/3)O3 makes the piezoelectric properties to become ‘soft’, while the addition of Pb(Mn1/3Nb1/3Sb1/3)O3 makes the piezoelectric properties to be ‘hard’. The Curie temperature (Tc) of the pseudoquintnary system decreases with the increase of Pb(Ni1/3Nb2/3)O3 or Pb(Mn1/3Nb1/3Sb1/3)O3 contents. The preferred piezoelectric properties were obtained in the composition with x=0.06 and y=0.06.
Authors: Fei Huang, Zheng Yi Fu, Ai Hua Yan, Tie Kun Jia, Wei Min Wang, Hao Wang, Yu Cheng Wang, Jin Yong Zhang
Abstract: TiO2/TiB2 heterostructures were successfully synthesized by a facile hydrothermal approach in an aqueous solution of hydrogen peroxide (H2O2). The influence of H2O2 on TiB2-based materials was systematically investigated using X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that TiB2 is prone to oxidize in the presence of H2O2. TiO2/TiB2 heterostructure which high-density anatase-TiO2 stand on the surface can be gained in the presence of H2O2 solvent and the final composition can be controlled by the temperature and time. The investigation may provide a path to further understand the chemical property of TiB2-based materials and synthesis method of heterostructure.
Authors: Gui Min Zhang, Zheng Yi Fu, Yu Cheng Wang, Hao Wang, Wei Min Wang, Jin Yong Zhang
Abstract: Two different kinds of mullite precursors with composition 3Al2O3•2SiO2 (3:2) were prepared by conventional drying ethanol solution and spray-drying aqueous solution of aluminum nitrate nanohydrate and tetraethoxysilane, respectively. The results of scanning electron microscope (SEM) indicate that one powder consists of irregular particles with size of 1-10μm, the other powder is made of inhomogeneously sized hollow spherical particles with mean size of 0.5-5μm. The TG-DTA curves indicate the hollow spherical particles are unfavorable to eliminate the decomposed products. After the precursors were sintered by Spark Plasma Sintering at 1450°C for 10min, the microstructures of the former are made of fine equiaxed grains with sizes of around 0.5μm, the latter consist of elongated grains distributed in the matrix of fine grains with imhomogenous size of 0.5~10μm due to the liquid phase forming. The different microstructures lead to the former sintered body is transparent, while, the sample from spray-drying is opaque.
Authors: Li Wei Huang, Zheng Yi Fu, Jin Yong Zhang, Wei Min Wang, Hao Wang, Yu Cheng Wang, Koichi Niihara, Soo Wohn Lee
Abstract: Carbon nanotubes reinforced alumina was fabricated by spark plasma sintering method. When adding 0.2wt% nanotubes, the fracture toughness of the composites prepared increases 19% compared with the pure alumina ceramics. The effect of sintering schedule on microstructure and mechanical properties is investigated systematically. Microstructure studies reveal that at high sintering temperature, the nanotubes tend to gather in the gaps surrounded by three or more grains in a flocculent state, which leads to poor mechanical properties. Raman spectrum indicates that long sintering duration may cause serious nanotubes destruction and lower the mechanical properties.
Authors: Qing Xu, X.L. Chen, S.J. Wu, Wen Chen, Hao Wang, B.H. Kim, J.H. Lee
Abstract: Structures, ferroelectric and piezoelectric properties of (Na0.5Bi0.5)0.90Ba0.10TiO3 ceramic sintered at different temperatures were investigated. The results confirm an important role of sintering temperature on the structure and electrical properties of the ceramic. It was found that the increase of sintering temperature in the range of 1110-1160  promoted the development of crystal structure and microstructural densification, leading to an improvement in ferroelectric properties, poling process and piezoelectric properties. Further increase of the sintering temperature above 1160  resulted in a slight deformation of ceramic specimens. With respect to sintering behavior and piezoelectric properties, a relatively narrow sintering temperature range near 1150  was ascertained to be preferred for the ceramic.
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