Study On The Technology And Properties Of C/C Composites Prepared By Liquid Deposition

C/C composites are widely used in aerospace,military and other fields due to its excellent properties,such as low density,high specific strength,high temperature resistance and wear-resisting,etc.However,its traditional densification processes have the disadvantages of long preparation cycle,crusting and high cost,etc,which severely limit its wider application.Chemical liquid deposition(CLVD)is a new process to rapidly densify the porous prefabrication and prepare high-performance C/C composites,which realizes the sequential deposition of prefabrication from inside to outside,and can effectively solve the crusting problem etc,of traditional densification process.In this paper,using carbon felt as prefabrication,C/C composites were prepared by CLVD by using the self-made deposition device.850?,950?,1050? and 1150? were set as the deposition temperature,the deposition time was 3h,the effect of deposition temperature on densification behavior,microstructure and property were discussed.Under 950? and 1050?,the effect of deposition time on densification behavior and the effect of rough layer composites density on property were discussed.By comparing and analyzing the densification results and property of composites under different processes,the optimal process was established of C/C composites prepared by CLVD.The main results are as follows:(1)Self-made deposition device can meet the requirements of C/C composites prepared by CLVD,the effect of densification was fine.As deposition temperature increasing,the density and densification rate of composites first increased and then decreased,and the porosity,pore size range and aperture pore first decreased and then increased.Under 950? and 1050?,the density of composites increased linearly and the porosity decreased gradually with deposition time extending.Under 950?,after 3h deposition,the density of composite was the highest,porosity was the least,pore size range and aperture pore was minimal.(2)The micro morphology of composites are divided into three levels,the fiber,the interface layer and the pyrolytic carbon.The pyrolytic carbon grew in a layered growth pattern with coating carbon fiber.As deposition temperature increasing,the crystallization degree of pyrolytic carbon increased.The pyrolytic carbon produced under 850? was SL/RL banded structure;the pyrolytic carbon produced under 950? and 1050? was RL;the pyrolytic carbon produced under 1150? was ISO.(3)As deposition temperature increasing,the bending strength of composites first increased significantly and then decreased slightly,reached the maximum under 950?.The higher the density was,the higher the bending strength was.Between 850?~1050?,composites presented pseudoplastic fracture and the fracture was uneven;composite under 1150? was brittle fracture and the fracture was flush.(4)As deposition temperature increasing,the average friction coefficient and mass wear of composites presented the variation trend of first increased and then decreased;the stability of friction coefficient gradually changed from wavy to stable to more stable to bigger wavy,the interface morphology of friction gradually changed from more rough to smooth to more smooth to rough.Under 950? and 1050?,the higher the density of rough layer composite was,the better the friction and wear property was.Under 950?,the property of friction and wear was optimal after 3h deposition.