Full
CHEN Zhiwei (1996-), male, Master candidate. E-mail: czwlkif@163.com
Outline
Low-temperature hot pressed Si3N4 ceramics show a greater Vickers hardness and a lower fracture toughness, while high-temperature hot pressed Si3N4 ceramics show a lower Vickers hardness and a higher fracture toughness. To prepare Si3N4 ceramics with a great Vickers hardness and a high fracture toughness, a low-temperature hot pressed Si3N4 ceramic was prepared via sintering at 1 500 ℃ with 20% SiC whisker (SiCw, in volume fraction) and 2.5% ZrB2. The phase composition, relative density, microstructure and mechanical properties of low-temperature hot pressed Si3N4 ceramic were investigated, compared with high-temperature hot pressed Si3N4 ceramics at 1 800 ℃. The results show that the addition of SiCw inhibits the densification of Si3N4 ceramics sintered at 1 500 ℃, and the relative density decreases from 97.9% to 92.9%, the Vickers hardness decreases from 20.5 GPa to 16.4 GPa, and the fracture toughness increases from 2.9 MPa·m1/2 to 3.4 MPa·m1/2. However, the addition of SiCw and ZrB2 promotes the phase transition from α-Si3N4 to β-Si3N4. The relative density of Si3N4-SiCw-ZrB2 reaches 97.5%, and the Vickers hardness and fracture toughness are 20.7 GPa and 5.1 MPa·m1/2, respectively. Compared with low-temperature hot pressed Si3N4 ceramic, the fracture toughness of Si3N4-SiCw-ZrB2 ceramic is improved without reducing the Vickers hardness. Compared with high-temperature hot pressed Si3N4 ceramic, the hardness is greatly improved. The Si3N4-based ceramic with high hardness and toughness prepared via a low-temperature hot pressing with SiCw and ZrB2 can have a promising application in ceramic structural parts.
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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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