MODIFICATION OF SI_3N_4-SIC HEAT ABSORPTION CERAMIC MATERIAL USING FOR TOWER TYPE SOLAR THERMAL POWER PLANT

摘要

Using Si_3N_4, SiC, andalusite as substrate materials, Cr_2O_3, Y_2O_3 and ZrO_2 as modifying additives, Si_3N_4-SiC heat absorption ceramic was prepared by burying pressless sintering process. The bending strength, thermal shock resistance, thermal expansion coefficient, oxidation resistance, phase composition and microstructure of the ceramic were investigated. The results indicated that the optimized formula is H3, the best sintering temperature is 1480℃, bending strength is 100.26MPa, the bending strength have increased after thermal shock for 30 cycles, the increase rate is 10.34%, the thermal expansion coefficient is 4.561×10~(-6)℃~(-1), the oxidation rate constant is 1.7389 mg~2·cm~(-4)·h~(-1) with a fitted coefficient of 0.9976.XRD analysis indicates that the main phase compositions are a-SiC, Si_3N_4, mullite and O'-Sialon.SEM studies show that the microstructure exhibit like reticular structure. The composite additives of Cr_2O_3 and ZrO_2 have no effect on formation flowers and reticular structure phase, while the composite additives of Y_2O_3 and ZrO_2 is beneficial to form the flowers and reticular structure phase, what's more, the composite additives of Cr_2O_3, Y_2O_3 and ZrO_2 have obvious effect on formation reticular structure phases which is good for the increase of oxidation resistance and thermal shock resistance.