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Dai J.,State Key Laboratory of Gansu Advanced Non Ferrous Metal Materials | Dai J.,Lanzhou University of Technology | Dai Y.,Lanzhou University of Technology | Wang Z.,Lanzhou University of Technology | Gao H.,Lanzhou University of Technology
Journal of Experimental Nanoscience | Year: 2015

(Formula presented.) (x = 0.12) nanofibres have been successfully prepared by sol-gel method, electrospinning and subsequent heat treatment. The prepared nanofibres were characterised via X-ray diffraction (XRD), transmission electron micrograph (TEM) and superconducting quantum interference device (SQUID). The XRD revealed that the crystal structure of samples was hexagonal magnetoplumbite structure at calcination temperature from 900 °C to 1100 °C. The TEM showed that the ferrite nanofibres had a smooth morphology and a bamboo joint structure, and the diameter of nanofibres increased with the increase of sintering temperature. The SQUID revealed that there were some intriguing changes in magnetic properties with the variation of sintering temperature or altering calcination time, and the optimised magnetic property of samples was Ms70.76 emu/g, Mr36.35 emu/g and Hc6.26 kOe at 950 °C for 2 h, the corresponding grain size was 39.30 nm. Meanwhile, the nanofibres display more significant improvements in the magnetic properties than the nanoparticles obtained by the sol-gel process, which was probably due to the anisotropic morphology and the cylindrical magnetic domain of ferrite nanofibres. © 2013, Taylor & Francis. Source


Dai J.,State Key Laboratory of Gansu Advanced Non Ferrous Metal Materials | Dai J.,Lanzhou University of Technology | Mu X.,Lanzhou University of Technology | Chen X.,Lanzhou University of Technology | And 2 more authors.
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2011

The field emission performances of normal-gate cold cathode, which is composed of different multi-wall carbon nanotubes (MWCNTs) bundles array are calculated. The device parameters such as the arrangement of bundles, array density, gate location, gate voltage, anode voltages and anodecathode distance affect the field emission properties, which is discussed in detail. The results reveal that the hexagon bundles array needs a lower threshold voltage than square array to reach high field enhancement factor and large emission current density. The emission current density is two orders larger than that of the oxide emitter. The optimal bundles array densities of hexagon and square array to get field enhancement factor are 0.0063 and 0.00375 μm-2, respectively. Meanwhile, the field emission performances are impacted critically by gate location and gate voltage. Field emission properties changed little while the anodecathode distance varies within tens of micrometers, which increases the process-friendliness of CNTs field emission devices.© 2011 Elsevier B.V. All rights reserved. Source


Dai J.,State Key Laboratory of Gansu Advanced Non Ferrous Metal Materials | Dai J.,Lanzhou University of Technology | Chen D.,Lanzhou University of Technology | Li Q.,Yibin University
Physica B: Condensed Matter | Year: 2014

The structural and electronic properties of N, P, As and Sb doped (9.0) single-walled SiC nanotubes (SWSiCNTs) are investigated by the first-principle theory. The calculated results indicated that one P, As or Sb atom substituted for one C atom, which could be considered as n-type semiconductors. When one N, P, As or Sb replace one Si atom, the model shows the character of semi-metallic, n-type semiconductor, p-type semiconductor respectively. These results indicated that with the addition of atomic radius and reduction of electronegativity, dopant of VA elements will bring bizarre change of electronic properties. These results are expected to give valuable information in building nanoscale electronic devices. © 2014 Elsevier B.V. Source


Dai J.,State Key Laboratory of Gansu Advanced Non Ferrous Metal Materials | Dai J.,Lanzhou University of Technology | Meng C.,Lanzhou University of Technology | Li Q.,Yibin University
Physica B: Condensed Matter | Year: 2013

The ferromagnetic properties of Zn0.875Co0.125O and Zn0.875(Co0.5Mn0.5)0.125O are investigated using total energy of plane wave and ultrasoft pseudopotentials method based on the density functional theory (DFT). The results show that Zn0.875Co0.125O and cobalt (Co) and manganese (Mn) codoped ZnO-based dilute magnetic semiconductors (DMSs) are of the ferromagnetic order, and the ferromagnetism mostly comes from interaction of spin-polarized oxygen atoms, zinc atoms and transition metals. Meanwhile, it is also found that the magnetic moments are mostly contributed by the spin-polarized oxygen atoms and transition metals. In addition, the electron sharing for the 3d states of transition metals (Co, Mn) and 2p states of O atoms is exacerbated as compared to pure ZnO and Co doped ZnO, helping to obtain p-type ZnO. These results indicate that Co and Mn codoped ZnO are promising magneto-electronic materials and they can be used for nanoscale spintronics device material. © 2012 Elsevier B.V. Source


Wang Q.,State Key Laboratory of Gansu Advanced Non Ferrous Metal Materials | Li X.,Lanzhou University of Technology | Nie W.,Lanzhou University of Technology | Xia Y.,Lanzhou University of Technology | Dai J.,State Key Laboratory of Gansu Advanced Non Ferrous Metal Materials
Advanced Materials Research | Year: 2010

The ZnO/TiO2 composite films were deposited over glass using spin coating technique by sol-gel process. Single-walled carbon nanotubes (SWNTs) were used to modify the ZnO/TiO2 films successfully in this paper. The structure and composition of the ZnO/TiO2 composite and SWNTs doped ZnO/TiO2 composite were characterized by X-ray diffraction (XRD). The morphology of samples was characterized by scanning electron microscopy (SEM). The photocatalytic activity was investigated by photocatalytic degradation of aqueous methyl orange under ultraviolet (UV) radiation. The UV-vis absorption spectra of the ZnO/TiO2 films and SWNTs doped ZnO/TiO2 films in the wavelength region 200∼800 nm were obtained. The results indicate that the SWNTs addition can decrease the grain size of ZnO/TiO2, which can enhance the photocatalytic activity. UV-vis absorption spectra of SWNTs-ZnO/TiO2 showed obvious blue shifts compared with ZnO/TiO2. The optimal amount of doping SWNTs is 1% according to this research. The enhanced mechanism of the SWNTs for the photocatalytic activity in ZnO/TiO2 films was analyzed in this article. © (2010) Trans Tech Publications. Source

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