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Publications (14)10.35 Total impact

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    ABSTRACT: The ageing effect on the field emission (FE) reproducibility of multiwalleded carbon nanotubes (MWCNTs) synthesised by plasma enhanced chemical vapour deposition was investigated by scanning electron microscopy. To investigate the ageing effect on the physical state of the MWCNTs, a scanning electron microscope (SEM), a Raman spectrometer, an X-ray photoelectron spectroscope and an X-ray diffractometer were used to characterise the MWCNTs comprehensively before and after the ageing. Through ageing, the FE reproducibility became better because the larger number and more evenly distributed shorter MWCNTs – (resulted from the local vacuum breakdown of higher MWCNTs due to Joule heating and oxidisation) – became the dominating emitters.
    Journal of Experimental Nanoscience 06/2011; 6(3):270-280. · 0.88 Impact Factor
  • Q. Zou, M.Z. Wang, Y.G. Li
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    ABSTRACT: The onion-like carbon (OLC) was synthesised by annealing the nanodiamond fabricated by detonation for 1 h at the temperature of 1150°C in the low vacuum of 2 Pa. The OLC particles were characterised using a high-resolution transmission electron microscope (HRTEM) for observing its microstructure, an X-ray diffractometer (XRD) for determining its crystal structure and component, and a Raman spectrometer for confirming its content. The results showed that the OLC particles exhibited similar shape to that of the original nanodiamond particles. The average size of the OLC was found to be approximately 5 nm. The transformation mechanism of the OLC from the nanodiamond by annealing at lower temperature and lower vacuum was also discussed.
    Journal of Experimental Nanoscience 10/2010; 5(5):375-382. · 0.88 Impact Factor
  • Q. Zou, M. Z. Wang, Y. G. Li
    Journal of Experimental Nanoscience 08/2010; 5(4):319-328. · 0.88 Impact Factor
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    ABSTRACT: The microstructure in the worn surfaces of a failed bainitic steel railway crossing was investigated using optical microscopy, SEM, TEM, nanoindentation and Mössbauer spectroscopy. The results indicated that a nanocrystalline layer had formed in the surface of a worn crossing during service. The formation of the nanocrystalline layer was due to the severe plastic deformation (SPD) caused by the repeated heavy loading in service by high speed train wheels. The mechanism of formation of the nanocrystalline layer was strain induced dynamic recrystallization, and the nanocrystalline grains were nucleated from the original crystals of the steel directly. The alloying elements in the worn surfaces of the steel segregated slightly by diffusion during the process of recrystallization. The nanocrystalline layer does not display the white etching layer commonly observed in ordinary railway rails, the reason may be the differences of its microstructure and carbon content with the ordinary rail steel.
    Wear 05/2010; · 1.26 Impact Factor
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    ABSTRACT: Onion-like carbon (OLC) was synthesized by annealing nanodiamond in low vacuum (1 Pa) at the temperatures from 500 to 11400°C. The high-resolution transmission electron microscope images, X-ray diffraction patterns and Raman spectra showed that, when the annealing temperatures were lower than 900°C, there was no OLC fabricated. The amorphous carbon and the nanodiamond coexisted. The graphitization started from the surfaces of the nanodiamond particles. When the annealing temperatures were higher than 900°C, the OLC was fabricated. At 900°C, OLC began appearing and the size of the OLC particles was smaller than 5 nm. At the annealing temperature of 1400°C all the nanodiamond particles were transformed into OLC. The OLC particles exhibited similarity to the original nanodiamond particles in shape. Based on these results, a mechanism for the OLC synthesis by the method of annealing in vacuum was provided.
    Inorganic Materials 01/2010; 46(2):127-131. · 0.38 Impact Factor
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    ABSTRACT: Onion-like carbon (OLC) was synthesised by annealing detonation nanodiamond for 1.5 h at temperatures from 500 to 1400°C and at a vacuum of 1 Pa. The results showed that the nanodiamond was transformed into the amorphous carbon (a-C) at first and then the a-C was transformed into the OLC gradually with the increase in annealing temperature. Moreover, at the annealing temperature of 600°C, the nanodiamond started transforming into a-C from the edge of the nanodiamond particle (1 1 1) crystal plane. At the annealing temperature of 750°C, the nanodiamond was transformed into the a-C completely. At the annealing temperature of 850°C, the a-C began transforming into the OLC at the edge area. At the annealing temperature of 1000°C, the OLC particle with a size smaller than 5 nm was synthesised. However, in the centre of the OLC particle, untransformed a-C coexisted. At the annealing temperature of 1100°C, the microstructure of the OLC particle with a size smaller than 5 nm became optimised. At the annealing temperature of 1200°C, the OLC particle with a size larger than 5 nm was fabricated. There was also untransformed a-C coexisting in the centre of the OLC particle. At the annealing temperature of 1350°C, all the a-C was transformed into the OLC. The average size of the OLC was approximately 5 nm, which was the same as that of the nanodiamond. The layers of the OLC were varied from several to 12.
    Journal of Experimental Nanoscience 01/2010; 5(6):473-487. · 0.88 Impact Factor
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    ABSTRACT: The onionlike carbon (OLC) was fabricated by annealing nanodiamond synthesized by detonation at the annealing temperatures from 500 to 1400 °C and at the pressure of approximate 2 Pa. A high-resolution transmission-electron microscope was used to characterize the microstructures of the OLC as-fabricated. The results showed that at the annealing temperature of 500 °C, nanodiamond began transforming into amorphous carbon. At the annealing temperature of 800 °C, nanodiamond was transformed into amorphous carbon completely. At the annealing temperature of 900 °C, OLC began appearing and the size of the OLC particles was smaller than 5 nm. At the annealing temperature of 1000–1200 °C, the OLC particle with larger size than 5 nm was fabricated. Moreover, the amorphous carbon untransformed and coexisted in the center of the OLC particle became fewer and fewer with the annealing temperature increase. At the annealing temperature of 1400 °C, all the amorphous carbon was transformed into the OLC. The OLC particles exhibited similarity to the original nanodiamond particles in shape. The formation process of the OLC included formation of amorphous carbon, formation of graphite fragment, connection of graphite fragment, connection and curvature of graphite sheets, and closure of graphite layers.
    Journal of Vacuum Science & Technology B Microelectronics and Nanometer Structures 01/2010; 28. · 1.36 Impact Factor
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    ABSTRACT: Various apparatus were used to analyse the structures and the surface states of the nanodiamond particles synthesised by detonation, including a high-resolution transmission electron microscope (HRTEM), an energy diffraction spectrometer (EDS), an X-ray diffractometer (XRD), a Raman spectrometer (Raman), a Fourier transform infrared spectrometer (FTIR) and a differential scanning calorimeter (DSC). The grain size of the nanodiamond particles was in the range of 2-12-nm. However, the average grain size was approximately 5-nm. Moreover, the shapes of the nanodiamond particles were spherical or elliptical. The nanodiamond as-synthesised was very pure, which almost contained carbon only. The contents of the impurity element including O, N and S were very small, which came from the synthesis and purification processes when fabricating the nanodiamond. The surfaces of the nanodiamond particles absorbed many functional groups, such as hydroxy, carbonyl, carboxyl and ether-based resin. The initial oxidation temperature of the nanodiamond powder in air was about 520degC, which was lower than that of the bulk diamond. However, the oxidation temperature of the nanographite existing in the nanodiamond powder was about 228degC. The graphitisation temperature of the nanodiamond in Ar gas was approximately 1305degC.
    Micro & Nano Letters 10/2009; · 0.85 Impact Factor
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    ABSTRACT: Synthesis of carbon nanomaterials by pulse microplasma in the chamber of a scanning electron microscope equipped with a special discharge cell is reported. The peak current density of the methane microplasma was higher than 5 kA cm, and the pulse width was almost 10 ns. After 5 s operation, there could be observed some carbon nanomaterials deposited on the cathode of the platinum film besides melted spots.
    Plasma Devices and Operations 09/2009; 17(3):175-180. · 0.38 Impact Factor
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    ABSTRACT: Microplasma was produced in argon gas in a scanning electron microscope at near-atmospheric pressure using a multi-wall carbon nanotube (CNT) film as a cathode. It is demonstrated that with the CNT film used as a cathode, the breakdown voltage was much lower than the breakdown voltage when the conventional cathode made of flat metal film was used and the discharge was highly reproducible. These features of the gas discharge are defined by the field emission from the CNT cathode.
    Plasma Devices and Operations 09/2009; 17(3):181-190. · 0.38 Impact Factor
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    ABSTRACT: Nanodiamond is a relatively new nanomaterial with broad prospects for application. In this paper, a variety of methods were used to analyze comprehensively the structures and the surface states of the nanodiamond synthesized by detonation, for example, X-ray diffraction (XRD) spectroscopy, energy diffraction spectroscopy (EDS), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy (Raman) and differential scanning calorimeter (DSC). The results show that, the nanodiamond particles are spherical or elliptical in shape. The average grain size is approximately 5 nm. The surfaces of the nanodiamond contain hydroxy, carbonyl, carboxyl, ether-based resin, and other functional groups. The initial oxidation temperature of the nanodiamond in the air is about 550 °C, which is lower than that of the bulk diamond.
    Materials Characterization 01/2009; 60(11):1257-1262. · 1.88 Impact Factor
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    ABSTRACT: The properties of the field emission (FE) from multi-walled carbon nanotubes (CNTs) in air used to generate the microplasma at near-atmospheric pressure were investigated in a removable gas cell built into a scanning electron microscope. The gaps between the electrodes were adjusted from 5 to 100 μm and the pressure was changed from 0 to 100 kPa. The obtained results have shown that the FE properties of the CNTs at 10 kPa and lower pressures were the same as those in vacuum. At a pressure more than 10 kPa, the FE threshold voltage in air was higher than those in vacuum, and increased with increasing atmospheric pressure. When the FE threshold voltage became higher than that of the gas breakdown, the microplasma was ignited before the FE initiation. Thus, the FE properties of the CNTs in air were stable when the FE potential was lower than the voltage of conventional gas discharge with CNT cathode.
    Plasma Devices and Operations 01/2009; 17(4):286-292. · 0.38 Impact Factor
  • Materials Research Innovations - MATER RES INNOV. 01/2009; 13(4):468-472.
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    ABSTRACT: In this paper failed Hadfield (high manganese austenite) steel crossing in railway system was acted as the research object, the microstructure changes in the worn surface layer of the crossing were investigated by using optical microscopy, X-ray diffraction (XRD) and transmission electron microscope (TEM). The micro-properties of the worn surface and subsurface layers of the crossing were tested by means of nanoindenter equipment. In the mean time, the worn failure mechanism of the crossing was discussed. The results indicated that the microstructure in the worn surface of the Hadfield steel crossing changed to nanocrystalline. The nanocrystalline layer improved the wear resistance of the Hadfield steel. The failure of the Hadfield steel crossing included three stages, that was plastic deformation and wear in the first served stage before the passing trough loads of 1∼2×107 tons, wear in the medial stage among the passing trough loads from 1×107 to 9×107 tons, and fatigue spalling in the final served stage after the passing trough loads of 8∼9×107 tons. Accordingly, some new methods were put forward, which leaded to increase the lifetime of the crossing and enhance the safety of the railway system.