Effects Of Carbon Matrix Precursors And Graphitization Treatment On The Structure And Tribological Properties Of C/C-SiC Composites

With higher preparation cost and longer preparation cycle,the development and application of C/C-SiC composites are limited.Compared with propylene,natural gas has the advantages of high diffusivity,better thermal stability,wide source and low production cost,and was considered to be a more ideal carbon matrix precursor.In this work,C/C-SiC composites derived from natural gas and propylene,respectively.And the effects of carbon matrix precursors and the temperature of graphitization treatment on the microstructure,mechanical and tribological properties of C/C-SiC composites were investigated.The main conclusions are as follows:(1)When without graphitization treatment,the microstructure of pyroarbon of C/C-SiC composites that derived from natural gas and propylene were a ribbon structure(Rough Laminar+smooth Laminar)and a single smooth laminar structure,respectively.And the outer surface of the pyrocarbon with a ribbon structure is scale,but the outer surface of the pyrocarbon matrix with a single smooth laminar structure is smooth and flat.With the increase of temperature of the graphitization treatment,the scale characteristic of the outer surface of the pyrocarbon matrix with a ribbon structure is gradually obvious.The scale feature on the outer surface of the pyrocarbon could improve the wettability of liquid silicon on its surface,resulting in the formation of a nano-SiC layer with with smaller particle size and spherical particle stacking during the silicon infiltration process.(2)When without graphitization treatment,the mechanical properties of C/C-SiC that derived from natural gas are 208.5 MPa(flexural strength),and 47.1 kJ/m2(impact toughness),which are 11%,and 16%higher than the C/C-SiC that derived from propylene,respectively.And its compressive strength and shear strength are 299.4 MPa and 16.7 MPa,respectively.Which are 15%and 5%lower than the C/C-SiC that derived from propylene,respectively.With the increase of temperature of the graphitization treatment,the mechanical properties of C/C-SiC that derived from natural gas decreased less than that of propylene.(3)When without graphitization treatment,compared to propylene,the coefficient of friction(0.41)and coefficient of stability(0.77)of C/C-SiC that derived from natural gas were increased by 8%and 4%,respectively,which were mainly due to its small particle size nano-SiC layer could improve the stability of the braking process.With the increase of temperature of the graphitization treatment,the stability of the braking process of C/C-SiC gradually improved,and the coefficient of stability reached 0.81(natural gas)and 0.78(propylene),respectively,which were 5.19%and 5.4%higher than the original samples,respectively.