The Mass Preparation Technologies Of SiC Nanowires Depended On Diverse Raw Materials Systems

As a wide band gap semiconductor, SiC one-dimensional (1D) nanomaterials possess excellent properties in mechanical, electrochemistry, optical, photocatalysis and other fields, which have aroused great interests due to their extensive application. Study on the SiC ID nanomaterial have become one of the hotspots. Recently, the preparation technique and growth mechanism of SiC ID becoming better and approaching perfection day by day. How to obtain the gram-scale production of the SiC 1D nanomaterial remains a most challenging research subject.In this paper, SiC nanowires have been successfully synthesized via chemical vapor deposition method (CVD) with nickel nitrate as catalyst, high-purity Si powers and three diverse carbon sourses(type A carbon, type B carbon and type C carbon) as main raw materials. The effect of technology parameters on the yields, morphologis and structures of SiC nanowires has been discussed. The optimal preparation process parameters have been selected out via conditional experiments. The growth mechanisms of the SiC nanowires using diverse carbon sourses were characterized by scanning electron microsopy (SEM), transmission electron microsopy (TEM), energy spectrum (EDS) and X-ray power diffraction (XRD). The main contents and results are as follows:Firstly, SiC nanowires have been synthesized by using high-purity Si powers as silicon source and type A carbon as carbon source. And Vapor-Liquid-Solid (VLS) mechanism has been proposed to explain the growth process of the products through the systematic research of raw ratio, heat rate, reaction temperature and holding time. SiC nanowires coated with SiO2 shell of 9nm-12nm thickness and diameters about 20nm-60nm and micron in lengths were obtained sucessfully under the technological parameters (the mole ratio of silicon power and type A carbon:1:1.2, the heating rate: 7℃/min, reaction temperature:1250℃, reaction time:2h). Moreover, the yield of production for the purified SiC nanowires was up to 11.4g and the conversion rate was 57% after calcination and purification treatment.Secondly, SiC nanowires with diameters of about 8nm-42nm and lengths to micron levals have been synthesized by using high-purity Si powers as silicon source and type B carbon as carbon source. Vapor-Liquid-Solid(VLS) mechanism was proposed to explain the growth process of the products through the systematic research of raw ratio, heat rate, reaction temperature and holding time. SiC nanowires coated without SiO2 shell were obtained successfully under the technological parameters (the heating rate: 7.5℃/min, the preheating temperature:900 ℃, the second heating rate:3℃/min, reaction temperature:1300 ℃, reaction time:4h). Moreover, the yield of production for the purified SiC nanowires was up to 10.4g and the conversion rate was 52% after calcination and purification treatment.Lastly, SiC nanowires with diameters of about 35nm-80nm and lengths to micron levals have been successfully synthesized by using high-purity Si powers and type C carbon as main raw materials. Solid-Liquid-Solid (SLS) mechanism was proposed to explain the growth process of the products through the systematic research of raw ratio, heat rate, reaction temperature and holding time. SiC nanowires coated with SiO2 shell with the thickness of 9nm-20nm were obtained successfully under the technological parameters (the mole ratio of type C carbon and silicon power:1:1.2, the heating rate: 15℃/min, reaction temperature:1150℃, reaction time:2h). Moreover, the yield of production for the purified SiC nanowires was up to 9.6g and the conversion rate was 48% after calcination and purification treatment.