Guangyi Yang

Fabrication and photoluminescence of bicrystalline SiC nanobelts

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.

Growth of SiC nanowires/nanorods using a Fe?Si solution method

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.

Elegant SiOx heliotropes composed of assembled flexural SiOx nanowires

Silicon oxide nanowires assembled with elegant heliotrope-shape have been synthesized by the modified evaporation of Fe and Si mixture sources. Structures and morphologies of the obtained microheliotropes were thoroughly studied by field emission scanning electron microscopy and high resolution transmission electron microscopy. It is suggested that the multinucleation sites around the perimeter of Fe droplet are responsible for the growth of SiOX nanowires and then via self-assembly process, which results in the formation of microheliotropes. These interesting results and discussion may be beneficial to the understanding of complex nanostructures formation and hopefully enrich the conventional knowledge of vapor-liquid-solid growth phenomena.

The Growth of SiC Crystals from CoSi Molten Alloy Fluxes

The growth of SiC single crystals from SiC saturated Co-Si molten alloy fluxes is reported. Experiments were performed by two routes: liquid phase sintering of CoSi/SiC and Si/Co/SiC powder compacts and melt infiltration of CoSi alloy into porous SiC powder preforms. Results showed that euhedral SiC crystals, many of which appeared as polygonal or plate shaped single crystals, grew from the SiC saturated CoSi molten alloy. The largest SiC crystals exceed half millimetre in size, after 25h of isothermal dwelling at 1700°C in the melt infiltration process. The nature of the growth mechanism, the crystal defects and the effects of constituent materials, temperature and time on the abnormal grain growth of SiC single crystals are further discussed.