摘要
Abstract
This work prepared high fracture toughness Si3N4 ceramics by addition of composite sintering additives and elon-gatedβ-Si3N4 seeds,which was called self-reinforced of silicon nitride ceramics.Phase composition,microstructures, open-porosity,fracture toughness and flexural strength were tested by using XRD,SEM,Archinmedes,SENB and three-point bending test.At first,the effect of sintering additives (Y2O3 and Al2O3 )on the sintering properties and mechani-cal properties was investigated by pressureless sintering.The experimental results showed that silicon nitride ceramics can achieve good mechanical properties,the relative density of Si3N4 ceramics was more than 95%,flexural strength of 674 MPa and fracture toughness of 6.34 MPa·m1/2 .When the sintering additives of Y2O3 and Al2O3 were 8wt% and 4 wt%. Then the introducing of La2O3 to increase the aspect ratio of Si3N4 grains,make the flexural strength and fracture tough-ness of Si3N4 ceramics to 686 Mpa and 7.42 Mpa·m1/2 .The elongatedβ-Si3N4 seeds were prepared by pressureless sinte-ring at 1750℃,the average length,diameter and aspect ratio were 2.82μm,0.6μm and 4.7,respectively.The influence of seeds on Si3N4 ceramics sintering properties and mechanical properties were studied by this article.The results demonstra-ted that the fracture toughness of silicon nitride was improved significantly with the addition of the seeds,while the relative density and bending strength are decreased slightly.In addition,the fracture toughness initially increased and then de-creased with increasing seeds amount.When the content ofβ-Si3N4 seeds was 2wt%,the highest fracture toughness was 7.68 Mpa·m1/2 ,improved by more than 20%.关键词
Si3N4/陶瓷/烧结助剂/β-Si3N4/晶种/长径比/断裂韧性Key words
Si3N4 ceramics/Sintering additives/β-Si3N4 seeds/Aspect ratio/Fracture toughness分类
化学化工
