ABSTRACT Here we report a novel route for synthesizing nano-polycrystalline diamond (NPD) using stearic acid (C18H36O2) as a starting material under high pressure and high temperature. The obtained NPD shows a transparent dark-yellowish color similar to the standard NPD synthesized from graphite and consists of extremely fine diamond grains (∼10 nm). The temperature required for the present synthesis of pure transparent NPD is as low as 1000°C at 13 and 17 GPa, which is surprisingly lower than that for conventional NPD synthesis (1800–2000°C). The amorphous-like, extremely poorly crystalline graphite produced by the thermal decomposition of stearic acid likely provides preferential nucleation sites for diamond and significantly lower the activation energy. The removal of volatile components such as H2O generated through the decomposition from the system is a key to obtain pore-free transparent NPD. Magnesite, MgCO3 and periclase, MgO can be used as an efficient H2O remover through the hydration reaction.

中文翻译：

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硬脂酸分解合成纳米多晶金刚石

摘要 在这里，我们报告了一种使用硬脂酸 (C18H36O2) 作为原料在高压和高温下合成纳米多晶金刚石 (NPD) 的新途径。获得的 NPD 显示出类似于由石墨合成的标准 NPD 的透明暗黄色，并且由极细的金刚石颗粒（~10 nm）组成。目前合成纯透明 NPD 所需的温度在 13 和 17 GPa 下低至 1000°C，这令人惊讶地低于传统 NPD 合成所需的温度（1800-2000°C）。硬脂酸热分解产生的无定形、结晶性极差的石墨可能为金刚石提供了优先的成核位点并显着降低了活化能。从系统中去除通过分解产生的 H2O 等挥发性成分是获得无孔透明 NPD 的关键。菱镁矿、MgCO3 和方镁石、MgO 可通过水合反应用作高效的 H2O 去除剂。