Full
YU Wei (1995-), male, Master candidate. E-mail: 1308616969@qq.com
Outline
Cordierite glass-ceramics exhibit low dielectric constant, dielectric loss and thermal expansion. The stoichiometric cordierite MgO-Al2O3-SiO2 (MAS) glass is due to the surface crystallization. In this paper, MAS glass-ceramics with various contents of TiO2 as a nucleation agent were prepared by a melting method and subsequent heat treatment. The effect of TiO2 content on the crystallization behavior and properties was investigated. The results show that the glass transition temperature and the first crystallization peak temperature decrease with the increase of TiO2 content, indicating that TiO2 can effectively promote the crystallization. TiO2 enters into the glass network structure, and facilitates the formation of μ-cordierite and magnesium aluminum titanate crystalline phases in the glass, and then form α-cordierite at a higher temperature. The crystallization mechanism of glass with more than 5% (in molar fraction) TiO2 becomes the bulk crystallization. As TiO2 content increases to 10%, the glass-ceramics heat-treated at 800 ℃ for 10 h and 1 000 ℃ for 5 h have a high density of 2.95 g/cm3, a hardness of 9.67 GPa, and a thermal conductivity of 2.13 W/(m·K). At 8.2-12.4 GHz, its dielectric constant is 6.3-6.5 and the dielectric loss fluctuates from 10-2 to 10-3. At 1 MHz, the dielectric constant is 10.8 and the dielectric loss is 0.024 4.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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