Deakin Research

Institute for Frontier Materials

Nanorods

Air-assisted Growth of Tin Dioxide Nanoribbons

Tao Tao, Alexey M. Glushenkov, Qi Y. Chen, Ying Chen

Journal of Nanoscience and Nanotechnology, 10 (2010) 5015-5019

Abstract: SnO2 nanoribbons have been synthesized by annealing of a milled SnO2 powder that has a metastable structure created by ball milling treatment. When the milled powder was annealed in an assembly of two combustion boats, SnO2 nanoribbons formed. The nanoribbons tend to grow along the [101] crystallographic direction and their side surfaces are represented by ± (010) and ± (101 ) facets. The oxygen plays an important role in enhancing their formation.

SEM image of a cluster of SnO2 nanoribbons (left) and a single ribbon (right)




A novel approach for real mass transformation from V2O5 particles to nanorods

Alexey M. Glushenkov, Vladimir I. Stukachev, Mohd Faiz Hassan, Gennady G. Kuvshinov, Hua Kun Liu, and Ying Chen

Crystal Growth & Design, 8(10) (2008) 3661-5

Abstract: A solid-state, mass-quantity transformation from V2O5 powders to nanorods has been realized via a two-step approach. The nanorods were formed through a controlled nanoscale growth from the nanocrystalline V2O5 phase created by a ball milling treatment. The nanorods grow along the [010] direction and are dominated by {001} surfaces. Surface energy minimization and surface diffusion play important roles in their growth mechanism. Real large quantity production can be achieved when the annealing process is conducted in a fluidized bed which can treat large quantities of the milled materials at once. The crystal orientation of nanorods provides an improved cycling stability for lithium intercalation.

The transformation of ball milled V2O5 powders into nanorods. SEM images of as-milled powders (a) and the material after subsequent annealing in air at 630 C for 5, 10 and 30 min (b, c, and d, respectively).  TEM characterization of a typical nanorod. (a) Bright-field image and the corresponding SAED pattern of a typical nanorod, (b)HRTEM image of the nanorod lattice, (c) 3D model revealing the typical shape of V2O5 nanorods




Growth and structure of prismatic boron nitride nanorods

H.Z. Zhang, J. D. Fitz Gerald, L. T. Chadderton, J. Yu, Y. Chen

Physical Review B 74(1)(2006) 045407

Abstract: Growth takes place by rapid surface diffusion of BN molecules, and follows heterogeneous nucleation at catalytic particles of an Fe/Si alloy. Lattice imaging transmission electron microscopy studies reveal a central axial row of rather small truncated pyramidal nanovoids on eachnanorod, surrounded by three basal planar BN domains which, with successive deposition of epitaxial layers adapt to the void geometry by crystallographic faceting. The bulk strain in the nanorods is taken up by the presence of what appear to be simple nanostacking faults in the external, near-surface domains which, like the nanovoids are regularly repetitive along the nanorod length. Growth terminates with a clear cuneiform tip for each nanorod. Lateral nanorod dimensions are essentially determined by the size of the catalytic particle, which remains as a foundation essentially responsible for base growth. Growth, structure, and dominating facets are shown to be consistent with a system which seek slowest bulk and surface energies according to the well-known thermodynamics of the capillarity of solids.

(a) Lattice image of a typical nanorod shows three structural features: (1) lattice fringes organized into three domains A, B, and C, (2) voids in the domain B, and (3) dark stripes in domains A and C; (b) SADP of the nanorods; (c) histogram of the apex angle shows a continuous distribution; (d) XEDS signals from domains A and B demonstrate that the nanorod consist of boron and nitrogen only (and an extraneous signal for the copper of the specimen support grid).  The structural model of the nanorod: (a) a cuneiform, the structural unit, and (b) a nanorod consisting of stacking cuneiform

(a) Lattice images of the nanorods (b) Corresponding electron diffraction pattern (c) the distribution of the apex angles (d) the composition of the nanorods: B and N only




PatternedGrowth and cathodoluminescence of conical boron nitride nanorods

H.Z. Zhang, M. Phillips, J. Fitz Gerald, J. Yu, Y. Chen

Appl. Phys. Lett. 88 (2006) 093117

SEM images of the as-grown patterned conical nanorods. The inset shows a welldefined boundary between the growth and nongrowth regionsCathodoluminescence spectra taken at (a) 300 and 80 K, (b) different excitation powers: 100 and 200 nA
Panchromatic CL images (a) showing the square pattern structure inclined  ~40 to the image edges, (b) strong emission from the catalyst region

Cathodoluminescence (CL) spectra of the nanorods show two broad emission bands centered at 3.75 and 1.85 eV. Panchromatic CL images reveal clear patterned structure. 2006 American Institute of Physics




Conical boron nitride nanorods synthesized via the ball-milling and annealing method

H.Z. Zhang, J. Fitz Gerald, J. Yu, Y. Chen

Journal of the American Ceramic Society 89 (2006) 675-679

Abstract: Nanorods: A boron nitride (BN) nanostructure, conical BN nanorod, has been synthesized in a large quantity on Si substrates for the first time via the ball-milling and annealing method. Nitridation of milled boron carbide (B4C) powders was performed in nitrogen gas at 1300°C on the surface of the substrates to form the BN nanorods. The highly crystallized nanorods consist of conical BN basal layers stacked along the nanorod axis. Ball milling of the B4C powders can significantly enhance the nitridation of the powders and thus facilitate the formation of nanorods during the annealing process.(2) Patterned growth: A catalyst layer of Fe(NO3)3 was patterned on a silicon substrate by using a copper grid as a mask. The nanorods were grown via annealing milled boron carbide powders at 1300°C in a flow of nitrogen gas. The as-grown nanorods exhibit uniform morphology and the catalyst pattern precisely defines the position of nanorod deposition.

1.Milling-effect:

 X-ray diffraction spectra of original and milled B4C powders     Thermogravimetric analysis of original and milled B4C powders

(a) XRD pattern shows the milled B4C powder having smallcrystallite sizes; (b) Enhanced nitridation of the milled B4C powder

2.Morphology:

(a) The BN nanorods are grown on the silicon substrate on alarge sacle. The nanorods have (b) conical tips and (c) bulbousattachment(catalyst particles)

(a) The BN nanorods are grown on the silicon substrate on a large scale. The nanorods have (b) conical tips and (c) bulbous attachment (catalyst particles)

Field emission characteristics of conical boron nitride nanorods

H.Z.Zhang, Q. Zhao, J. Yu, D. P. Yu, and Y. Chen

J. Phys. D: Appl. Phys.(2006), Accepted

Abstract: The emission current of the BN nanorods can be up to ˜60 µA at an applied voltage of ˜3 kV. Two distinct slopes are evident in the Fowler-Nordheim (FN) plot. The field-emission characteristics can be explained using a site-related tunneling-controlled mechanism. The occurrence of two FN slopes is attributed to the switchover from tip emission to side emission, which results from the differences in interface barrier, geometry, as well as total emission area of the two emission interfaces.

(a) Bright-field TEM image reveals the typical morphology of the nanorods: conical tips and attached catalyst
Particles, (b) A lattice image of a nanorod tip displays nanosized voids at the centre of the nanorods and a tacking cone structure is evident. (c) A lattice image of the side morphology of a nanorod shows the cones interweave with each other on the nanorod side surface    The FN plot of the FE characteristics shows two distinct slopes corresponding to low and high voltages    An illustrative sketch of the energy-band diagram of a BN nanorod showing the shallow and deep levels

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20th February 2012