Research On Microstructures And Properties Of High Voltage Stanchion Insulator Ceramics

Stanchion porcelain insulator is one of the main components of the electriacl transmission lines unit. In recent years, the power accident happened frequently due to the fracture of stanchion porcelain insulator. Hence it is necessary to grasp the factors that influence the inner quality of stanchion porcelain insulator from the aspects of composition, organization structure and property, which could provide a technology support for the electric power department to develop the assessment work of the stanchion porcelain insulator. This dissertation takes the silicium and aluminum stanchion porcelain insulator as the object of study, by researching the microstructure and properties of mechanics and fracture mechanism based on the fracture toughness and thermal shock to estimate the reliability of stanchion porcelain insulator.By means of the flux created in the crystal phase during the sintering process lead to acceleration of sintering, which result in densification of the stanchion porcelain insulator. Siliceous insulators have more mullite in phase composition and lower density. The amount of the pores is larger and the roundness of them is lower. Moreover, the remained silica particles are embedded into ceramic matrix. On the contrary, the alumina insulator ceramics are richer in Al2O3, having less pores and higher density. The pores in them are more spherical, and the remained Al2O3 particles contact tightly with the matrix.The mechanical property of alumina insulator is higher than silica insulator, their thermal conductivity and coefficient of thermal expansion are comparable. There was cleavage fracture happened in the ceramic materials. The siliceous insulator cracked mainly along the pores and the boundaries between the mullite and matrix, while the aluminum insulator cracked not only along the pores and boundaries, but also along the Al2O3 grains.The K1c of the aluminum insulator is obviously higher than the siliceous insulator. The Al2O3 grains and quartz played an important role in toughening the ceramics. However, the strength, toughness of quartz and the binding force is low compared with the Al2O3, which lead to the obdurability effect of siliceous insulator was not obvious.The parameter of R characterizes the thermal shock resistance of stanchion porcelain insulator, which has a relationship with strength, elastic modulus and CTE. In essence, the value of R correlates with the composition and microstructure (especially by the porosity) of stanchion porcelain insulator. Although the strength of siliceous insulator was not large, its thermal shock properties were excellent, which can be due to its relatively loose structure.