Correlation Between Composition And Structural Evolution Of Fused Silica Brick And Fracture Behavior Under Service Condition

The service behavior of fused silica bricks after installation is still unclear.In this paper,commercial fused silica bricks are heated to 1400? and then dwelled for 0h,0.5h,2h,5h,10 h,25h,respectively.Combined with the crystallization mechanism of fused silica,the correlation between the composition and structural evolution of fused silica bricks and their failure behavior during the service period was systematically studied.The results show that:(1)The most important change of fused silica brick after heat treatment is crystallization and phase transformation of fused silica.Due to the lack of mineralizer in the fused silica brick,the crystallization and phase transformation products are mainly cristobalite,and the content of cristobalite increases with the increase of dwelling time.The content of cristobalite in the sample 25 h reached 80%.(2)The formation of cristobalite in the fused silica brick is from the matrix to the particles,and the cristobalization of the fused silica particles develops from the particle surface to the particle center.The crystallization of fused silica has a considerable influence on the microstructure of fused silica bricks.The crystallization of cristobalite caused a large number of fine cracks in the fused silica bricks,and a considerable part was located at the interface between the surface of the particles and the matrix.The crack on the surface of the particle promoted more intergranular fracture when the sample was subjected to the breaking behavior of the force,and the strength and brittleness of the material were reduced.(3)In the heat treatment process of fused silica bricks,in addition to crystallization and phase transformation of fused silica,the further sintering of fused silica bricks had a great influence on the change of physical and chemical properties.The tighter bonding of the particles to the matrix reduced the porosity of the fused silica bricks while increasing their mechanical strength to some extent.(4)The change of mechanical strength of fused silica bricks is accompanied by the change of brittleness,and the change of brittleness is positively correlated with the trend of strength.And for the same sample in different tests,the brittleness of the fused silica bricks has a different tendency,because the size difference of the samples during the test is large,which causes the composition and structure of the fused silica bricks to be different influence to the test result.(5)When the heat treatment temperature of the fused silica brick is higher than 1200 ° C,crystallization of the fused silica brick occurs,resulting in a decrease in strength.