No abstract

Carbon/carbon composite of various density were synthesized via chemical vapor infiltration process, and the sedimentary process of pyrolytic carbon were also researched. The density of the sample increased with the extension of growth time. Density change rate of the samples were various at different stages of the growth process, namely pyrolytic carbon of different densities formed at the different stages. It was found that pyrolytic carbon filled the pores of carbon fiber preform, which can help to relieve the interface stress between the fiber and the ceramic substrate. In order to improve the performance of the composite, SiC and ZrC ceramics were introduced into the carbon/carbon composite via polymer infiltration and pyrolysis (PIP) process. The ability of high temperature resistance and oxidation resistance of the composite were strengthened by the PIP process. The bending strength, tensile strength and compressive strength were also increased with the extension of PIP cycle. The C/C-SiC-ZrC composites were obtain through this process, which are useful in various areas.

In this paper, using PCS and ZrB2 precursor as raw materials, we prepared Cf/SiC-ZrB2 composites by precursor infiltration and pyrolysis (PIP) process. We studied the solution of different solid content on the influence of porosity and weight gain，and also studied the effect of pressure and other conditions in the process of infiltration. The viscosity of the solution is tested with NDJ-8S digital rotational viscometer. We observed the microstructure of materials through the scanning electron microscope (SEM). The optimum technological parameter was determined by the experiment. The results showed that: a reasonable solution group in relation to the viscosity of the mixed solution，that is the main factor affecting on the performance of the impregnation; The method of vacuum and pressure impregnation can reduce the preparation period and improve material density rapidly. Under the experimental conditions, the best viscosity of the mixed solution is 54.8 mpa•s, the time of vacuum impregnation is 1.5h, and the optimum value of pressure impregnation is 7 MPa.

Two kinds of Cf/Mullite composites are prepared using S-sol and T-sol through PIP method in the paper. Properties of mechanical and microstructure are studied. The results show that the density of Cf/Mullite composites prepared by S-sol is 1.78 g·cm-3, the porosity is 35.04%, the bending strength reached 109.00 Mpa and the fracture toughness was 8.20 Mpa·m1/2. Through the SEM analysis of the Cf/Mullite composites it can be seen that a weak binding interface was formed. The ductile fracture mechanism is presented in the process of stress, and the fiber extraction is obvious.

In this paper, we added inert filler SiC and ZrC powders in an organic precursor solution to prepare Cf/SiC-ZrC composites. The experiments of three different contents of slurry in the process of impregnation and pyrolysis for Cf/SiC-ZrC composites were studied. The microstructure and composition of Cf/SiC-ZrC composites were analyzed by scanning electron microscope (SEM) equipped with EDS. This study shows that the addition of inorganic powders in an organic precursor solution can shorten the period of preparation of the composite material and improve its strength. When the mass fraction of the inert filler is 15% in an organic precursor solution, the density of the composite material can be increased to 1.9 g·cm-3 rapidly in 8 periods of preparation. Meanwhile, the internal structure of the prepared composite material becomes more compact, and its mechanical properties are excellent.