Study on the Fabrication Technics and Mechanical Properties of Glass-Ceramics in MgO-Al_2O_3-SiO_2 System

Abstract: The cordierite based MgO-Al_2O_3-SiO_2 system glass-ceramics is a kind of good materials with low dielectric loss factor, excellent thermal stability and high mechanical intension, used in the fields of micro-electronic, spaceflight, navigating. The research and application of glass-ceramics in MgO-Al_2O_3-SiO_2 system are very active all along.In this paper, the development, classification, fabrication technology and application of glass-ceramics were systematically reviewed. A kind of glass-ceramics in MgO-Al_2O_3-SiO_2 system was prepared by melting with TiO_2 and ZrO_2 as nucleating reagents. The major crystalline phases are cordierite,spinel and sapphirine. The phase compositions of the glass-ceramics were analyzed by XRD, and their microstructures were observed by SEM.Experiments showed that TiO_2 can effectively prompt crystallizing of the glass. Precipitation began from the surface. The surface precipitation would begin when the content of nucleating reagents was 6% or below it. A kind of glass-ceramics in MgO-Al_2O_3-SiO_2 system was prepared, TiO_2 and ZrO_2 as nucleating reagents. With the contents of nucleating reagents increase, crystallization temperature of the glass decreases and its crystallizing ability increases. After heat treatment, the main precipitation are sapphirine, spinel and ZrTiO_3.Heating conditions make obvious influence on the glass-ceramics. In this work, The magnesium aluminotianate(MAT) is precipitated in glass at 780 ℃, and sapphirine, spinel, cordierite and enstatine are precipitated in sequence. The cordierite is precipitated in glass at about 1150℃. Because of different kinds, contents and dimensions of the crystalline phases by different heat treatments, we can get glass-ceramics with different properties.We get the conclusion: the best contents of nucleating reagent are TiO_2-7%/ZrO_2-3 %, when the sample is treated at 800 ℃ for 1h and then at 1190℃ for 1h, the strength property is more than 320MPa…
Key words: galss-ceramics; MgO-Al_2O_3-SiO_2; composite nucleating reagents; heat treatment; strength property

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