Production Process And Growth Mechanism Of SiC One-Dimensional Nanomaterials

In this thesis, we present an effective regulation and optimization approach toscale up the production of SiC one-dimensional nanomaterials on the graphitesubstrate using milled Si-SiO2mixed powders and high-quality CH4as reactants bychemical vapor reaction (CVR) based on single-chamber vacuum furnace (SC-VF) andthree-chamber continuous production vacuum furnace (TC-VF), respectively. Wesequentially design the experiments according to the VLS growth mechanism andidentify the optimal reaction process parameters based on the characterization ofproduction, morphology, crystal structure, and growth mechanism of SiCone-dimensional nanomaterials. Provide a basis for the further study of excellentperformance and industrial application of SiC one-dimensional materials.Firstly, we carried out a series of experiments with the SC-VF to investigate theoptimization process of the growth temprature, pressure and time. We obtainedoptimal carbonation reaction of the different amount reactants: temperature is1300oC,pressure (2g,20Pa;4g,30Pa and6g,30Pa) and time (2g,20min,4g,30min and6g,45min). The characterization indicates that: SiC nanowires is β-SiC single crystalgrown along [111] direction, diameter of about80~120nm. The maximum depositionthickness of the SiC one-dimensional materials is up to about100μm.Secondly, we studied the influence of multi-step CVD process on the productionof SiC one-dimensional nanomaterials. Innovative design of the multi-step CVDprocess of the SiC one-dimensional nanomaterials production was studied. SiCnanowires with uniform diameter and high density for the first deposition, when usingthe re-deposition as the substrate, the density of SiC nanowires is decreasing, attachedto the surface of the first time product with suspended state. In addition, we collected a large scale of SiC nanowires on the upper surface of the reactant, and the diameter ismore uniform and high density, which provides the basis ideas for the design of thereaction chamber structure.Thirdly, we monitored the temperature and pressure of the furnae in real-time toinveatigate the different growth period of SiC nanomaterials according to the VLSgrowth mechanism. The nucleation temperature started at1000oC, and the optimumreaction temperature of growth stage is1200~1300oC. At the period of termination, thechanging of the reaction chamber lead to the end of growth of SiC nanowires bent,twisted, and flocculent forms, which promote the research of morphology controlablepreparation of SiC one-dimensional nanomaterialsFinally, we carried out a series of experiments based on the TC-VF to prepare SiCnanowires, and determine the feasibility of the TC-VF production process. UsingANSYS workbench engineering application analysis software to simulated the reactionof indoor airfield and optimal designed the gas sub-chamber devices and materialsbearing device. The final continuous production process as follows: reactants quality is20g, optimal growth temperature is1300oC, the best ventilation flow rate of methaneis0.2slm and optimal ventilation for30min, the optimal reaction time is90min. SiCone-dimensional nanomaterials production process is more efficient and effective.Characterization: SiC nanowires of β-SiC single crystals, grown along the [111]direction, the diameter is about80~100nm with high dendity. In addition, newequipment and optimization process applied in the field of naomaterial production willgreatly promote the development of industrial application of SiC one dimensionalnanomaterial.