Full
Liu Jian (1990-), male, Doctorial, candidate. E-mail: liujian16@mails.tsinghua.edu.cn
Outline
β-phase high thermal conductivity silicon nitride ceramics were prepared by sintering at 1 900 ℃ for 2 h using silicon nitride (α-phase≥95%, particle size 0.5 μm) as a raw material, and MgO-Y2O3 as a composite sintering aid. The effects of sintering aid content and ratio on the densification process, thermal conductivity, mechanical properties and microstructure of silicon nitride ceramics were discussed. The results show that when the addition amount of sintering aid is 5% MgO+4% Y2O3, the thermal conductivity, bending strength, fracture toughness of the sample sintered in air at 1 890 ℃ for 2 h can reach 85.96 W·m-1·K-1, 873 MPa and 8.39 MPa·m1/2, respectively. In the sintering process, Y2O3 reacts with Si3N4 to form a compound fixed at the grain boundary, which plays a role in purifying the silicon nitride lattice and improves the thermal conductivity of the sintered sample. Excessive MgO and Y2O3 will form compounds during the sintering process and remain at the grain boundary, which will reduce the mechanical properties and thermal conductivity of the material.
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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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