Growth Thermodynamic Analysis And Preparation Of SiC Nanowires

Silicon carbide nanowires have potential wide applications in the field of high strength composite materials,nanoelectronics device,photonic device,and photosensitive sensor due to its high thermal conductivity,high chemical stability,super-plasticity,high temperature resistance,corrosion resistance and unique electrical and optical properties.Controllable macro production of silicon carbide nanowires is of great significance for the development of its practical application.In this paper,the growth thermodynamic of silicon carbide nanowires was analyzed and the growth mechanism of silicon carbide nanowires was discussed,moreover,silicon carbide nanowires were prepared by carbon thermal reduction process.The main conclusions were listed as follows:?1?The growth thermodynamic and growth mechanism of silicon carbide nanowires in the SiC-O reaction system were discussed.In this system,the SiO?g?is generated by the reaction of SiO₂?s?with C?s?and Si?s?.the CO?g?is generated by the reaction of CO₂?s?with C?s?or SiO?g?with C?s?.The SiC?s?nuclei is produced by the reaction of SiO?g?with C?s?or Si?s?with C?s?.The growth of silicon carbide nanowires is achieved by the reaction of SiO?g?with CO?g?.?2?The growth thermodynamic and growth mechanism of silicon carbide nanowires in the SiC-O-H reaction system were discussed.The difference between Si-C-O-H reaction system and the Si-C-O reaction system is that numerous C?s?and Si?s?are formed through organic raw material pyrolysis in the Si-C-O-H reaction system.SiC?s?nuclei is probably generated by the reaction of Si?s?with C?s?.In the reaction system of polydimethylsiloxane and silicon powder,the SiC?s?nuclei is probably synthesized by Si?s?with C?s?in the reaction system of ethanol and silicon powder.?3?Silicon carbide nanowires were prepared in closed system.In this Si-C-O-H reaction system,polydimethylsiloxane was used as liquid silicon source/ carbon source and silicon powder was used as solid silicon source.High crystallinity 3C-SiC nanowires with SiO₂ coating and having smooth surface,uniform diameter about 30 nm,and a few centimeters in length were prepared in this reaction system.?4?Silicon carbide nanowires were prepared in open system.In this Si-C-O-H reaction system,polydimethylsiloxane and anhydrous ethanol were respectively used as liquid silicon source/ carbon source and silicon powder was used as solid silicon source.6H-SiC nanowires having diameter from tens of nanometers to several hundred nanometers and several hundred microns long were synthesized in this reaction system.Introducing ferrocene catalyst?0.05 wt%?into the system can successfully prepare high crystallinity 3C-SiC nanowires at liquid raw material injection rate of 1 m L/min,carried gas rate of 200 mL/min,the product has a diameter about 40 nm and several millimeter in length.Meanwhile,there is carbon nanotube fibers appearing in the end of tube furnace about 30 cm.The growth thermodynamic analysis of silicon carbide nanowires in the Si-C-O and Si-C-O-H reaction system and the gas-solid reaction growth mechanism provide valuable information for the controllable synthesis of continuous SiC nanowire fibers in the future.