Preparation And Properties Of C/SiOC Composites By Polymer Infiltration And Pyrolysis

In the tactical missiles and civilian areas,the urgent need to prepare a large margin to shorten the preparation cycle,reduce the cost of preparation of composite materials.In this paper,three kinds of C/SiOC composites were prepared by hot pressing molding-PIP method for its application requirements.The effects of mass concentration of precursor,hot compression molding process,fiber volume fraction and interfacial PyC coating on the properties of the composite were investigated.The mechanical properties and oxidation resistance of the composites were investigated.The pyrolysis characteristics of 1053 resin and 1040 resin were studied,the products of phase and structure composition were investigated under different temperature of pyrolysis,and the evolvement of the microstructure of two kinds of silicone resin cleavage products with the pyrolysis temperature were explored,and molding and cracking process parameter setting were made through pyrolysis characteristics.At 1200 ℃,the ceramic yield of 1053 resin and 1040 resin are 74.8% and 81.1%,respectively.the pyrolysis products is mainly amorphous SiO₂ and free carbon,which can still keep stable below 1400℃.When the temperature is further increased,the phase structure is changed to generate the SiC phase.The effect of mass concentration of precursor and hot compression molding on the properties of the composites prepared by 1053 reisn were studied.After hot pressing molding,the material properties were greatly improved.The bending strength was improved to 260 MPa,the tensile strength reached 212 MPa,the shear strength increased to 17.6MPa,the density of the material increased to 1.65 g/cm³ as well.When the mass concentration was 40%,the bending strength and shear strength was 265 MPa and 24 MPa,fracture toughness 9.7 MPa·m^1/2.The comprehensive properties of the composite prepared by 40wt% precursor solution is better than 50wt%.The influence of fiber volume fraction and different thickness of PyC coating on the properties of the composites prepared by 1053 resin were studied.With the increase of fiber volume fraction,the density of the composites have no remarkable change,the tensile strength increases and the bending strength increases firstly and then decreases,the comprehensive properties of the composite,which the fiber volume fraction is 51.48%,would be best in all fabricated specimen.The composites with different thickness of CVD PyC interface coating,which the bending strength and the shear strength are improved greatly,and the fracture toughness is increased.The bending performance was improved from 260 MPa to 296 MPa,the shear strength increased from 25.9 MPa to17.4MPa.The specific process of hot pressing molding,fiber volume fraction and PyC interface coating on the properties of the composites prepared by 202 silicone oil was studied.When hot pressing molding,the density of composites decreased from1.83 g/cm³ to 1.78g/cm³,the increase of the bending strength was small,and its value was 341 MPa.The increase of the fracture toughness is large,and its value was 16MPa·m^1/2.However,the shear strength and the tensile strength decreased;Owing to the expansion of the material in the hot pressing-PIP and the fiber volume fraction is not controllable,which result in the fiber volume fraction of composites are below 50%.With the increase of the fiber volume fraction,the bending strength,shear strength and tensile strength increased firstly and then decreased,the fracture toughness decreased.The fiber volume fraction is 36.5%.The tensile and bending properties of the composites were 191 MPa and 358 MPa respectively;After CVD 5,10 h,the tensile strength were 223 MPa and 254 MPa,respectively,and the tensile strength of the composite was 93.3 MPa and 89.0MPa,respectively.The effect of interface PyC coating on the properties of composites prepared by 1040 resin was Study.With 1040 resin as precursor,C/SiOC composites was prepared by hot pressing molding,the tensile strength is 216 MPa,flexural strength is 296 MPa,shear strength is 22.5MPa,the fracture toughness is 21.1 MPa·m^1/2,and then the performance of composite with PyC interface coating were disscussed,with the coating time increasing,the flexural strength,tensile strength and fracture toughness increased,shear strength declined,compared with the composite which had on PyC coating,the material of tensile strength,flexural strength and fracture toughness decreased,shear strength increased.The high temperature properties and anioxdation of composites which were fabircated by 1053 resin,202 silicone oil and 1040 resin were studied.The result show that high temperature flexural strength of the composites were 125 MPa,117 MPa,76.7MPa at 1200℃,respectively.The antioxidant properties of the composites were studied prepared by three precursors.After the static oxidation,the weight loss rate of C/SiOC composites with different fiber volume fractions prepared by 202 silicone oil and 1053 resin was small,and the average weight loss rate was 21.7% and 21.6%,respectively.The oxidation resistance of the C/SiOC composite with fiber interface PyC coating was better than that of the composites with no interfacial coating.The effect of dynamic oxidation on C/SiOC composite prepared by three kinds of precursors which were be heated with quartz light were studied.The result show that the antioxidation of composites prepared by 1053 resin is better than that of composites by 202 silicon oil and 1040.