| Due to good chemical stability,high thermal conductivity,low thermal expansion coefficient,small thermal neutron absorption cross-section,outstanding wear resistance and excellent mechanic properties,SiC ceramic materials have the potential to be applied in the Gen-IV nuclear plant.However,it is a big problem to process Si C ceramic materials after preparation because of the brittleness.Precursor infiltration pyrolysis?PIP?method has been used to solve the problem whose procedure combines the preparation and process as one step.Using the PIP method,liquid precursor for SiC ceramic materials is required.In this paper,the ?/? transformation of SiC and the development of precursor derived ceramic?PDC?method were reviewed.Based on the review,the phase composition of SiC ceramic materials prepared by PDC method was explored.In the experiments,a self-crosslinkable liquid highly branched polycarbosilane?LHBPCS?with 5.07% vinyl group and C/Si ratio of 1.33 was used as the precursor to prepare SiC ceramic material.The parameters such as cross-linking time,cross-linking temperature,pyrolysized in Hydrogen,pyrolysized in microwave furnace,the addition of silica,were changed to explore the formation of the SiC ceramic material,including the yield,the phase composition,the content of Oxygen and Carbon,etc.The preliminary conclusions were as follows:?1?Parameters during cross-linking & the usage of Hydrogen Through the change of parameters,it was found out that: it was good for the formation of cross-linked to raise the curing temperature and to extend the curing time.The application of Ar gas did good to enhance the crystallinity of SiC ceramic.The content of Oxygen could be reduced by pyrolysized in Hydrogen gas,and meanwhile,the relative content of ?-SiC phase could be raised.The pyrolysis temperature was chosen as 800?.?2?The application of microwave furnace Through the comparison to conventional heating method,it was found out that: much shorter time and lower temperature were required using the microwave furnace.Meanwhile,the crystal size was around 15 nm,and the relative content of ?-SiC phase was as high as 99.5 %.?3?The effect of SiO2 additive Through the comparison of different content of SiO2,it was found out that: the addition of SiO2 could contribute to the control of the content of excess carbon,but lower a little bit the relative content of ?-SiC phase.In addition,the product contained more ?-SiC phase and less impurities were found as the content of SiO2 was raised... |
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