Formation of pure polycrystalline diamond by direct conversion of graphite at high pressure and high temperature
Formation of pure polycrystalline diamond by direct conversion of graphite at high pressure and high temperature
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DOI：
10.1016/j.pepi.2003.06.004
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发表时间：
2004-06-15
影响因子：
2.3
通讯作者：
Funakoshi, K
中科院分区：
文献类型：
--
作者：
Irifune, T;Kurio, A;Funakoshi, K
在压力12-25 GPa、温度1800- 2500 ℃下，用多砧装置，通过石墨直接转化合成了多晶金刚石聚集体。合成的金刚石是光学透明的，无色的，并通过微焦点X射线衍射确定的立方对称。TEM分析表明，样品由典型的10-20 nm的微小晶体组成，拉曼光谱仅观察到一个非常弱的宽谱带，其波长约为1332 cm（-1）。压痕测试表明，本发明多晶金刚石的努普硬度高达140 GPa，相当于甚至高于天然和合成单晶金刚石的努普硬度（类似于60 -130 GPa），几乎是含粘结剂的合成多晶金刚石的两倍（类似于50 -70 GPa）。目前的结果意味着，天然多晶金刚石可能已经形成了从亚稳石墨存在于冷俯冲地壳中的快速转变，当遇到在温暖的地区，如地幔过渡区上升的羽流。(C)2004 Elsevier B. V.保留所有权利。
Polycrystalline diamond aggregates have been synthesized by direct conversion of graphite at pressures of 12-25 GPa and temperatures 1800-2500degreesC using a multianvil apparatus. The synthesized diamond was optically transparent and colorless, and was of cubic symmetry as determined by micro-focus X-ray diffraction. TEM analyses revealed that the sample consists of minute crystals of typically 10-20 nm, and only a very weak and broad band at similar to1332 cm(-1) was observed by Raman spectroscopy. An indentation test demonstrated that the present polycrystalline diamond possesses a Knoop hardness of up to 140 GPa, which is equivalent to or even higher than those of natural and synthetic single-crystal diamonds (similar to60-130 GPa) and nearly twice as high as those of synthetic polycrystalline diamonds containing binders (similar to50-70 GPa). The present results imply that natural polycrystalline diamonds may have been formed by a rapid transformation from metastable graphite present in cold subducted crust, when encountering in warmer regions, such as rising plumes in the mantle transition region. (C) 2004 Elsevier B.V. All rights reserved.