Comparative Study on Composition, Structure and Mechanical Properties of Three Typical Alumina Insulator for UHVDC

Abstract

Abstract: Composition and structure are the two most essential factors for insulator materials performance. In this paper, the differences in composition, structure and mechanical properties of three typical alumina insulator for ultra high voltage direct current (UHVDC) were systematically studied, and the reasons were analyzed. The results show that compared with NGK, two domestic manufacturers have added more calcined industrial alumina, less potash feldspar and quartz into the formula, and have not properly raised the sintering temperature according to the formula, the porcelains of two domestic manufacturers show the following characteristic: 1) the content of Al₂O₃ are 47.22% and 45.24%, respectively, 7.31% and 5.33% higher than that of NGK, the content of SiO₂ are 46.32% and 48.44%, respectively, 7.09% and 4.97% lower than that of NGK, and the total content of K₂O+Na₂O are 3.21% and 3.14%, respectively, 0.41% and 0.48% lower than that of NGK; 2) the true porosity are 5.24% and 4.18%, respectively, 3.46% and 4.52% lower than that of NGK. The internal pores are basically less than 5 μm, and the pore size is generally smaller. There are many flat, slender, crack like pores, as well as annular pores and cracks surrounding the particles; 3) the content of internal crystalline phase is 48.10% and 49.04%, respectively, which is nearly 10% higher than NGK, with corundum phase being 10% higher, quartz phase being 4% higher, mullite phase being 4% less. The mullite phase is thinner and shorter, and the degree of crosslinking is lower; 4) the average value of the three-point bending strength of the porcelain head test strip are 155 and 158 MPa, respectively, which are higher than NGK, but the dispersion strength of the two domestic manufacturers is higher than NGK.

Key words: alumina, insulator, UHVDC, composition, microstructure, mechanical property

CLC Number:

TQ174

--, 修订日期:--. Comparative Study on Composition, Structure and Mechanical Properties of Three Typical Alumina Insulator for UHVDC[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2023, 42(6): 2206-2214.

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