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ABSTRACT: Tube-brush-shaped nanostructure of SiC nanowires was synthesized on polyacrylonitrile-based carbon fibers. The morphology and microstructure of the nanowires were characterized by X-ray powder diffraction, field emission scanning electron microscopy and high-resolution transmission electron microscopy. A quasi-periodically twin structure with (111) plane as the boundary along the SiC nanowires was observed. The vapor-solid growth mechanism of the SiC nanowire brush is also discussed. Moreover, some separated blue-shifted photoluminescence peaks around 469 nm were measured. The separated blue-shifted emission peaks are attributed to the quantum confinement of nanoscaled twin segments along each nanowire rather than the apparent diameters of the nanowires. The SiC nanowire brushes hopefully can find potential applications in nanotechnology.
Journal of Nanoscience and Nanotechnology 10/2010; 10(10):6550-5. · 1.56 Impact Factor
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ABSTRACT: We present a simple melt solution strategy for the growth of high-yield SiC nanowires out of NiSi solution. The growth temperature and base vacuum before filling argon during the reaction are found to have a significant effect on the morphology of the product growth. Taking into consideration the action of Ni in the NiSi melt and the possible participation of a tiny amount of oxygen, the formation of SiC nanowires is discussed by a combination of the solid−liquid−solid reaction for nucleation and the vapor−liquid−solid process for nanowire growth. The nanowires were also investigated with Raman spectroscopy. Such a simple and economical method may be extended to synthesize other one-dimensional nanostructures.
12/2008;
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ABSTRACT: Single crystalline SiC nanowires were synthesized by a catalyst free vapor deposition method using elemental silicon and graphite carbon as the starting materials. The phase, morphology, crystal structure, and defects of the products were characterized by x-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. Within a 6 h reaction time, the morphology of the SiC nanowires can be tuned to cylinder, hexagonal prism, or bamboo shape by simply altering the reaction temperature from 1470 °C, 1550 °C to 1630 °C, respectively. The photoluminescence of these differently shaped SiC nanowires was measured and is discussed. Based on the characterization results, the vapor-solid growth mechanisms for the multi-shaped SiC nanowires are proposed by taking into account the possible reactions between intermediate gas phases, the reaction steps, and the surface energy minimization.
Nanotechnology 08/2008; 19(33):335602. · 3.98 Impact Factor
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ABSTRACT: Abundant hexagonal prism-shaped SiC nanowires were synthesized on graphite substrate via heating silicon in a graphite crucible. The products were characterized using X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The characterization first showed that the product was nanowires of beta-SiC with almost a perfect hexagonal cross section. The growth was determined along [111] direction. The six side surfaces look smooth under low magnification microscopy, but faceted at high magnification. Based on the characterization results, a formation mechanism combining vapor-solid (VS) growth mechanism and the lowest surface energy principle is proposed.
Journal of Nanoscience and Nanotechnology 05/2008; 8(4):2151-6. · 1.56 Impact Factor
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ABSTRACT: SiC nanobelts have been synthesized by a reaction of Si and CNTS without catalysts using the simple evaporation method. The nanobelts display a unique bicrystalline structure that has growth directions, i.e. and , splitting along the twin boundary that exists at the centreline. The width of the nanobelts is in the range of 100–200 nm, the thickness ranging from 10 to 20 nm and their lengths are up to several tens of micrometres. The growth of bicrystalline SiC nanobelts follows the vapour–solid process. The photoluminescence spectrum of bicrystalline SiC nanobelts at room temperature shows a strong emission peak centred at 418 nm with a weak broad emission, based on which a possible emission mechanism is also discussed.
Journal of Physics D Applied Physics 06/2007; 40(12):3697. · 2.54 Impact Factor
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ABSTRACT: Twinned zigzag SiC nanoneedles have been synthesized by silicon evaporation onto multiwall carbon nanotubes (MWCNTS) at 1500 °C for 8 h. The product was characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), and high-resolution electron transmission microscope (HRTEM). The results show that the SiC nanoneedles have a zigzag surface, which is composed of (111) [112̄] periodic twined segments. The growth of twinned zigzag SiC nanoneedles was realized by the vapor−solid (VS) reaction, in which (111) plane stacks in a (111) [112̄] twinning manner, creating (111̄) faceting over the nanoneedle surface. The photoluminescence (PL) spectrum of the SiC nanoneedle shows considerable blue shifts of multi-PL peaks relative to the bulk 3C-SiC, due to the collective influence of size effects and defects.
04/2007;
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ABSTRACT: SiC crystal growth in transition metal silicide melts was investigated by using spontaneous infiltration and solution methods. In the infiltration experiments, SiC powder preforms were infiltrated with FexSiy (Fe3Si, Fe5Si3 and FeSi) and CoSi melts. The dissolution and precipitation of SiC led to SiC crystals growth in the infiltrated Fe5Si3 and CoSi melts, SiC particles coalescing in FeSi and free carbon precipitation in Fe3Si. In the solution experiments, carbon from the graphite crucible dissolved in and reacted with FeSi2 and Ti2.3Si7.7 to form SiC crystals. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman scattering spectrometer were employed to investigate SiC crystals growth. Based on the investigation, the effect of solution content on the SiC crystal growth, the growth mechanisms in both methods and prototypes of the SiC crystals are also discussed. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Crystal Research and Technology 04/2007; 42(5):445 - 450. · 0.95 Impact Factor
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ABSTRACT: A new solution technique to grow SiC nanowires/nanorods was developed by simply heating Fe–Si melt on a graphite plate in argon atmosphere to 1600 °C for 3 and 6 h. SiC nanowires/nanorods with diameters of 100 nm and lengths of several tens of micrometres were grown on the surface of the melt. The prototype of the nanowires/nanorods is 3C-SiC (β-SiC), and the growth direction is [111] for 3C-SiC. Taking into consideration the action of Fe in Fe–Si melt and the possible participation of oxygen, the growth mechanism of the SiC nanowires is proposed. It is believed that the formation of SiC nanowires is a combination of the solid–liquid–solid (SLS) reaction for nucleation and the vapour–liquid–solid (VLS) process for nanowire growth. In the SLS reaction, graphite carbon (solid) dissolved in the Fe–Si melt (liquid), and then reacted with the silicon in the melt to form SiC nuclei (solid). In the VLS reaction, SiO and CO (vapours) dissolved in the melt droplets (liquid) attached to the tip of the growing SiC nanowires (solid), and reacted to make them grow further.
Nanotechnology 03/2007; 18(15):155601. · 3.98 Impact Factor
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ABSTRACT: A novel nanostructured, prism-shaped β-SiC nanowhiskers have been synthesized by a reaction of carbon black and Si at 1500 °C for 12 h. Various durations of heating gave different growth stages that led to varied product morphologies. X-ray powder diffraction (XRD), field emission scanning electron microscope (FESEM) and high resolution transmission electron microscope (HRTEM) were used to characterize the products. These characterizations indicated that prism-shaped SiC nanowhiskers with a diameter of about 80–200 nm and the length up to several micrometers are straight, single crystalline β-SiC and the growth direction is along [1 1 1]. The results also show that the nucleation and growth process of the nanowhiskers seem to be a vapor–solid mechanism, and that the total heating time during the reaction process is a critical factor for the formation of prism-shaped SiC nanowhiskers. Some unique optical properties are found in the Raman spectroscopy that has red shift about 8 cm−1 relative to the bulk β-SiC.
Journal of Alloys and Compounds.
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ABSTRACT: SiC nanowires, SiC/SiO2 core–shell nanocables, and SiC nanotubes have been synthesized simultaneously by direct heating Si powders and multiwall carbon nanotubes (MWCNTs). The as-obtained SiC nanowires are generally 100 nm in diameter and several tens of micrometers in length, the nanocables consist of a 20–30 nm diameters single-crystalline SiC core covered by a uniform layer of about 20 nm thick amorphous SiO2, and the nanotubes with very narrow hollow channel have outer diameters of about 20 nm. The characteristics of the products are analyzed by various methods, results of which indicating that temperature and ambience are two key factors for the formation of the three different products; their possible growth mechanisms are also discussed.
Journal of Alloys and Compounds.
