ABSTRACT Nano-polycrystalline diamond (NPD) with various grain sizes has been synthesized from glassy carbon at pressures 15–25 GPa and temperatures 1700–2300°C using multianvil apparatus. The minimum temperature for the synthesis of pure NPD, below which a small amount of compressed graphite was formed, significantly increased with pressure from ∼1700°C at 15 GPa to ∼1900°C at 25 GPa. The NPD having grain sizes less than ∼50 nm was synthesized at temperatures below ∼2000°C at 15 GPa and ∼2300°C at 25 GPa, above which significant grain growth was observed. The grain size of NPD decreases with increasing pressure and decreasing temperature, and the pure NPD with grain sizes less than 10 nm is obtained in a limited temperature range around 1800–2000°C, depending on pressure. The pure NPD from glassy carbon is highly transparent and exhibits a granular nano-texture, whose grain size is tunable by selecting adequate pressure and temperature conditions.

中文翻译：

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在高达 25 GPa 的压力下由玻璃碳合成纳米多晶金刚石

摘要 使用多砧装置在 15-25 GPa 压力和 1700-2300°C 温度下由玻璃碳合成了具有各种晶粒尺寸的纳米多晶金刚石 (NPD)。合成纯 NPD 的最低温度（低于此温度会形成少量压缩石墨）随着压力从 15 GPa 下的~1700°C 显着增加到 25 GPa 下的~1900°C。晶粒尺寸小于 ~50 nm 的 NPD 在低于 ~2000°C (15 GPa) 和 ~2300°C (25 GPa) 的温度下合成，高于此温度时观察到显着的晶粒生长。NPD的晶粒尺寸随着压力的增加和温度的降低而减小，并且在1800-2000°C左右的有限温度范围内获得晶粒尺寸小于10 nm的纯NPD，具体取决于压力。