Preparation And Properties Of Silicon Carbide And Silicon Nitride Nanofibers

Combining with its high strength,excellent corrosion resistance,high temperature resistance and oxidation resistance,SiC and Si3N4 nanofibers possess the unique geometry and special properties of 1D nanomaterials.Therefore,they have important application prospects in the basic research as well as nano-devices,nano-composite materials,raw materials,biomedicine and many other fields.In this paper,SiO2 and PAN were used as raw materials to prepare SiC and Si3N4 nanofibers.And the composition,structure and growth mechanism of the samples were characterized in details.Meanwhile,a continuous 3D SiO2/PAN hybrid nanofiber mats are prepared by air spinning technology,and pre-oxidation under air is carried out.The obtained pre-oxidized SiO2/PAN hybrid nanofibers have the characteristics of large aspect ratio,high specific surface area,good dispersion and stable fiber structure,providing enough space for growth of Si based nanofibers under high temperature.SiC/SiO2-C hybrid nanofiber mats,of which carbon nanofibers provided a strong supporting role,were obtained through pre-oxidized SiO2/PAN hybrid nanofibers after 700 ?,1400? high temperature carbonization and carbothermal self-assembly in Ar.Pre-oxidized SiO2/PAN hybrid nanofibers were treated in N2 at 1400 ? high temperature,and a large amount of wool-like Si3N4/SiO2 core-shell nanofibers were obtained by N2 nitriding between SiO2 and carbonized PAN.The results show that the diameters of SiC/SiO2 nanofibers obtained under Ar are around 80-200 nm,and its length reaches thousands of micrometers.At 1400 ?,with the increase of reaction time,the SiC nanofibers tended to be oriented,the crystallinity is higher and the yield is also increased.SiC/SiO2 nanofibers exhibit high photocatalytic degradation ability.The removal rate of methyl orange solution catalyzed by UV-light reaches 92.7%,and the degradation capacity after several recycling is still about 90%.Carbon nanofibers provide a high-strength support for,which solves the problem that SiC nanofibers are easily aggregated and difficult to be recovered in solution.The diameters of long Si3N4/SiO2 core-shell nanofibers obtained under N2 are around 50-300 nm and their lengths up to several centimeters,showing a strong blue-green luminescence properties.As the reinforcements of epoxy resin,the composite show better mechanical properties.Through studying its growth process,the solid-liquid(VS)mechanism is proposed to explain the growth of SiC/SiO2,Si3N4/SiO2 core-shell nanofibers.