Study On Preparation And Properties Of ZrB₂-SiC/C Composite Ceramics

Because of the excellent thermal shock resistance, thermal stability and thermal erosion resistance at high temperature surrounding, ZrB2-SiC/C layer ceramic can been used in aerospace vehicles, high temperature shielding and so on. However, the inherent brittle of the material has limited its development and application. With self lubrication, chemical stability, high thermal conductivity, low expansion, corrosion resistance, high temperature resistant, the graphite material has been used in sealing material and aviation aerospace engine high temperature materials. With the two materials combined, ZrB2-SiC/C layer compound ceramic material has the important meaning in the Ultra high temperature ceramic composite material field.Laminated ZrB2-SiC/C ceramic with graphite interface layers was successfully prepared by doctorblade casting process, laminating and hot pressing. The results of mechanical properties of the samples with different SiC content, SiC particle size, holding time and sintering pressure were analyzed and compared after testing. The result shows that the condition of the optimum mechanical properties is:sintering temperature is1850℃; SiC content is20vol%; holding time is30mins; sintering pressure is30MPa.In the preparation of ZrB2-SiC/C matrix laminar delay substrate, the effects of SiC content, different temperature, binder, plastic, agent, solid content were investigated. The results showed that the solid content of the slurry was45vol%and the viscosity was1600mPa.s when the SiC content was20wt%, the SiC particle size was0.5um, the tape casting temperature was about30℃, the binder content was less than10%and the ratio R of the plasticizing agent and binder was between0.8-1.The phase composing and microstructure of ZrB2-SiC/C composites were investigated by XRD, SEM and EDS. The results showed that ZrB2-SiC layer and C layer were arranged alternately, the interface had clear boundaries, and the composition achieved precise controlled.After oxidation, the SEM and TEM images showed that ZrB2-SiC/C layer compound ceramic had more superior oxidation resistance, and the C layer can effectively reduce the material oxidation rate.