| As one of the candidate materials for key thermal structural components in aerospace and other fields,Cf/SiC-ZrC composites have excellent anti-oxidation and ablation properties.However,due to the long preparation cycle,complex process,and difficult to control the overall uniformity,its application in these fields is greatly limited.In this paper,slurry injection predensification was used to uniformly introduce SiC-ZrC ceramics before the densification of precursor impregnation cracking（PIP）or reactive melt infiltration（RMI）.Without destroying the original structure of carbon fiber preform,the preparation cycle was shortened and the density of thick-walled components was not uniform.The main research contents and results of this paper are as follows:（1）By analyzing the viscosity change of the slurry and the properties of the green body after pre-densification,the effects of dispersant content and solid content on the properties of the slurry,and the effect of the pre-densification process on the properties of the green body and the densification period were explored.The results show that when 0.5%sodium polyacrylate（PAAS）is added to 30 vol%slurry,the viscosity of the slurry is 108.4 mPa·s,and the dispersion effect of the slurry is the best at this time.The slurry injection method can produce green body with higher density and better uniformity.When the solid content of the injection slurry is 30 vol%,the density of the green body is the highest and the uniformity is better,and the density is 1.86 g/cm3.The density of the injected green body after 1 PIP cycle is 2.16 g/cm3,while the density of the impregnated green body after 6 PIP cycles is only 2.15 g/cm3,and the PIP densification of the injected green body can be shortened by about 83.3%to the same density preparation time.（2）Cf/SiC-ZrC composites were prepared by densification and ceramization of injected and impregnated green bodies by PIP and RMI processes,and the effects of pre-densification and densification processes on the mechanical properties of Cf/SiC-ZrC composites were studied.Influence.The results show that the flexural strength of the center and surface of the Cf/SiC-ZrC composites obtained by injecting china PIP densification has a small difference,which are 169.11 MPa and 168.39MPa,respectively.The fracture behaviors are all pseudoplastic fractures,and the overall The properties are more consistent;while the impregnated green body shows brittle fracture after PIP densification.The flexural strengths of the central and surface parts of the RMI densified injection samples are 41.12 MPa and 43.90 MPa,respectively,which are an order of magnitude lower than the flexural strengths of the composites densified by the PIP process.（3）Through plasma ablation experiments at 2300℃,the ablation resistance of the samples densified by different pre-densification processes was studied.The results show that the linear ablation rate and mass ablation rate of the center and surface of the injected pre-densified sample have little difference,and the line ablation rate and mass ablation rate of the center are 1.15×10-2 mm/s and 8.47×10-3 g/s;surface layers are 1.48×10-2 mm/s and 8.77×10-3 g/s,respectively.The line ablation rate and mass ablation rate in the center of the dipped pre-densified samples were higher,1.82×10-2 mm/s and 10.84×10-3 g/s,respectively.（4）The effects of SiC coating and densification process on the ablation properties of the samples were studied.The results show that the SiC coating can fill the defects such as pores and cracks on the surface of the sample,and the mass ablation rate is significantly lower than that of the sample without SiC coating.Compared with the injection sample densified by RMI,the internal and external mass ablation rates were reduced by 37.2%and 46.8%,respectively.41 Figures,8 Tables,82 References... |
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