Liquid-phase-induced Synthesis Of SiC Rods By Microwave Heating

Microwave heating technology has become a new and environmental friendly heating method.It has attracted tremendous attention in the field of material preparation in recent years.Also,many scientists have paid attention to it all over the world.The preparation of SiC crystal by microwave heating technology has became one of the research hotspots at home and abroad.However,the traditional methods for preparing SiC crystal still have the disadvantages of complicated preparation process,long preparation time and high heating temperature.In this paper,tetraethoxysilane(TEOS)was used as silicon source,activated carbon was used as carbon source,and boric acid was used as regulator and inducer to prepare precursor.Techniques of XRD?SEM?TG-DSC were carried out to characterize samples.The influence of liquid phase introduction of boric acid on the preparation of SiC crystal by microwave heating process was studied.The microwave heating thermal effects was studied which combined with different malar ratio of carbon silicon source.The growth kinetics of liquid phase induced SiC crystals prepared by microwave heating technology was revealed.The results showed that the microwave input power gradient affected the morphology of the SiC crystal.When the microwave input power gradient was 10mA/min and 30 mA/min,SiC rods in agglomerated state were obtained;when the microwave input power gradient was 20 mA/min,SiC rods with good dispersibility were obtained;the microwave input power gradient may affect the heat of the materials in the system,which caused the dispersion of the SiC crystals to be different.The microwave heating temperature also affected the morphology of the SiC crystal:when the microwave heating temperature was 1100 ~oC,the short SiC rods crystal with uniform growth direction were obtained;when the microwave heating temperature was 1200 ~oC,SiC crystals grew while nucleuing,so that the morphology of SiC crystal was not uniform;when the microwave heating temperature was 1300 ~oC,a large number of SiC particles were formed;the microwave heating temperature affected the distribution of hot spots in the system,thus affecting the reaction rate.Microwave holding time had an effect on the growth state of SiC crystals:when the holding time was 10 min,the number of SiC rods was the largest,and the morphology and size were uniform;the effective lengthening of the holding time helped the SiC crystals to grow sufficiently and prolong the heat preservation,while time increasing continuously will cause oxidation of the SiC crystal.The molar ratio of different carbon and silicon affected the product phase,size and number of SiC crystals:as the molar ratio of carbon and silicon increasing,the crystallinity of the obtained product increased,the size of SiC crystal increased gradually,and the number increased;the increase of molar ratio of carbon and silicon caused an increase in the reaction product,resulting in an increase in the reaction in the system.The results of SiC crystal synthesis at low temperature showed that the temperature at which SiC rods formed and began to grow was 950°C.