• Jun Wang

      Articles written in Bulletin of Materials Science

    • Influence of Ce0.68Zr0.32O2 solid solution on depositing 𝛾-alumina washcoat on FeCrAl foils

      Mei-Qing Shen Li-Wei Jia Wen-Long Zhou Jun Wang Ying Huang

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      The influence of Ce0.68Zr0.32O2 solid solution on properties of 𝛾-alumina based washcoat on FeCrAl foils was investigated. FeCrAl foils were pretreated at 950°C in air for 10 h before coating washcoat. Different amounts of Ce0.68Zr0.32O2 solid solution were added into ã-alumina-based slurries. The properties of washcoats were measured by ultrasonic vibration and thermal shock test, SEM, BET and XRD. The results show that the addition of Ce0.68Zr0.32O2 solid solution into slurries can improve 𝛾-Al2O3-based washcoat adhesion on FeCrAl foils. The more the Ce0.68Zr0.32O2 solid solution added into slurries, the higher was the specific surface area of aged samples. XRD characterization proved that ceria–zirconia solid solution can inhibit the transformation of 𝛾-Al2O3 crystal into others at 1050°C for 20 h.

    • Mesoscale organization of CuO nanoslices: Formation of sphere

      Jun Wang Shunxiao Zhang Zhanshuang Li Jia You Piaoping Yang Xiaoyan Jing Milin Zhang

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      The nanocrystalline CuO powders were prepared by precipitation method using Cu(NO$_{3})_{2}$ as copper raw material, water and ethanol as dispersants, and NaOH and ammonia solution as precipitates. The structure, particle size and morphology of resulting CuO powders were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The mechanism of CuO formation was discussed.

    • ZnO nanostructured microspheres and grown structures by thermal treatment

      Jun Wang Shunxiao Zhang Jia You Huijun Yan Zhanshuang Li Xiaoyan Jing Milin Zhang

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      Synthesis of flower-shaped ZnO nanostructures composed of ZnO nanosticks was achieved by the solution process using zinc acetate dihydrate, sodium hydroxide and polyethylene glycol-20000 (PEG-20000) at 180°C for 4 h. The diameter of individual nanosticks was about 100 nm. Detailed structure characterizations demonstrate that the synthesized products are wurtzite hexagonal phase, grown along the [001] direction. The infrared (IR) spectrum shows the standard peak of zinc oxide at 571 cm-1. Raman scattering exhibits a sharp and strong 𝐸2 mode at 441 cm-1 which further confirms the good crystal and wurtzite hexagonal phase of the grown nanostructures.

    • Study of structural transformations and phases formation upon calcination of Zn–Ni–Al hydrotalcite nanosheets

      Zhanshuang Li Yanchao Song Jun Wang Qi Liu Piaoping Yang Milin Zhang

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      In this paper, we describe a general process for the synthesis of highly crystalline Zn–Ni–Al hydrotalcitelike materials. The structure and thermal decomposition of the prepared samples are studied by XRD, FT–IR, TG–DSC, SEM, TEM and N2 adsorption/desorption. The morphology of large-sized, porous and hexagonal platelike Zn–Ni–Al hydrotalcite is affected by calcination temperature. BET specific surface area and pore volume are observed to increase with increase of the calcination temperature up to 700°C followed by a further decrease with increasing temperature.

    • Investigation of thermoelectric SiC ceramics for energy harvesting applications on supersonic vehicles leading–edges

      Xiao-Yi Han Jun Wang Hai-Feng Cheng

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      Utilizing thermoelectric technology to aerodynamic heat harvesting on the leading-edge is worth noticing in the thermal protection systems. In this paper, a nose-tip model in a supersonic flow field is developed to predict the thermoelectric performance of SiC ceramics structures. The generation performance is numerically investigated in terms of the computational fluid dynamics and the thermal conduction theory. The output power and energy efficiency of the nose-tip model are obtained with Mach number varying from 2.5–4.5. The generated power reaches 1.708 W/m2 at a temperature difference of 757 K at 𝑀 = 4.5. With respect to the Thomson effect, the output power decreases rapidly. However, larger output power and energy efficiency would be obtained with the increase of Mach number, with or without considering the Thomson heat. Moreover, under the higher Mach numbers, larger range of output current value is available.

    • High-performance aqueous rechargeable batteries based on zinc anode and NiCo2O4 cathode

      Jun Wang Zhijun Jia Songbo Li Yi Wang Wei Guo Tao Qi

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      A new aqueous Zn–NiCo2O4 rechargeable battery system with a high voltage, consisting of NiCo2O4 as cathode and metal Zn as anode, is proposed for the first time. It is cheap and environmental friendly, and its energy density is about 202.8 Wh kg–1. The system still maintains excellent capacity retention of about 85% after 100 full cycles at a current rate of 2 A g–1 between 1.5 and 1.95 V. This work not only provides a new battery system but also shows promise for application in large-scale energy storage for its low cost, good cycling and environmental friendliness.

    • Ex situ synthesis of G/$\alpha$-Fe$_2$O$_3$ nanocomposite and its catalytic effect on the thermal decomposition of ammonium perchlorate

      MERIEM AMINA FERTASSI QI LIU RUNZE LI PINGAN LIU JINGYUAN LIU RONG-RONG CHEN LIANHE LIU JUN WANG

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      $\alpha$-Fe$_2$O$_3$ nanoparticles were prepared by a facile hydrothermal method using ferric chloride hexahydrate(FeCl$_3$·6H$_2$O) as a precursor. Graphene oxide (GO) was synthesized using a modified Hummers method and graphenenanosheets (G) were successfully obtained by thermal reduction of GO. G/$\alpha$-Fe$_2$O$_3$ nanocomposite was prepared using ex situ synthesis in the presence of $\alpha$-Fe$_2$O$_3$ nanoparticles and GO solution. The characterization of the as-prepared materialswas performed using X-ray diffraction analyses and Fourier transform infrared spectroscopy; their morphology wasinvestigated by scanning electron microscopy and transmission electron microscopy; the specific surface area (SBET) wasdetermined by nitrogen adsorption; their catalytic activity on the thermal decomposition of ammonium perchlorate (AP) wasinvestigated by differential thermal analysis (DTA). The results of DTA indicated that the obtained nanomaterials contributein ameliorating the thermal decomposition of AP; specifically, the high decomposition temperature of AP decreases from432 to 380$^{\circ}$C. A significant decrease in the activation energy was also achieved in the presence of these nanomaterials, and the mixture of ammonium perchlorate with G/$\alpha$-Fe$_2$O$_3$ showed the lowest value (from 129 to 80.33 kJ mol$^{−1}$).

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