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Outline
The graphitization process of nano-crystalline diamond (NCD) under high pressure significantly influences the performance of sintered polycrystalline diamond bulks. Here, we investigated the graphitization temperature of both pure nano-diamond, with an average grain size of 50 nm, and a mixture of NaCl and nano-diamond powder in a pressure and temperature range of 5−9 GPa and 600−1500 ℃, respectively. With a quantitative analysis method employing powder X-ray diffraction, we analyzed the graphitization degree of NCD under different pressures and temperatures, examining both non-hydrostatic pressure conditions (pure NCD powder) and quasi-hydrostatic pressure conditions (NaCl-NCD mixed powder). Our findings indicate that the initial graphitization temperature of pure NCD powder exceeds 800 ℃ at 5 GPa, and ranges between 1000 and 1300 ℃ at 9 GPa. Notably, under quasi-hydrostatic pressure conditions at about 7 GPa, the graphitization temperature of NCD increases from 1000 ℃ in non-hydrostatic pressure conditions to 1500 ℃ or higher within a short holding time.
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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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