Direct conversion of carbon nanofibers and nanotubes into diamond nanofibers and the subsequent growth of large-sized diamonds
Direct conversion of carbon nanofibers and nanotubes into diamond nanofibers and the subsequent growth of large-sized diamonds
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DOI：
10.1039/c8nr08823c
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发表时间：
2019-02-07
期刊：
影响因子：
6.7
通讯作者：
Pant, P.
中科院分区：
文献类型：
--
作者：
Narayan, J.;Bhaumik, A.;Pant, P.
我们报道了一种脉冲激光退火方法，可在常温常压的空气中将碳纤维和碳纳米管转化为金刚石纤维。碳纳米纤维和碳纳米管转化为金刚石纳米纤维的过程包括利用纳秒激光脉冲在过冷状态下熔化，然后快速淬火转化为纯相金刚石。该转化过程在常温常压下发生，且可在空气中进行。金刚石纤维的结构已通过透射电子显微镜中的选区电子衍射、高分辨率扫描电子显微镜中的电子背散射衍射得到证实，这些都显示出金刚石结构的特征衍射线。其键合特性通过拉曼光谱确定，在1332 cm⁻¹附近有一个强峰，并且通过透射电子显微镜中的高分辨率电子能量损失光谱确定，对于sp³键合，在292 eV处有一个对应于σ*的特征峰，且不存在对应于sp²键合的π*峰。由于纳米金刚石中的声子限域，1332 cm⁻¹处的拉曼峰对于金刚石纳米纤维下移至1321 cm⁻¹。这些带有金刚石晶种的经激光处理的碳纤维可通过标准热丝化学气相沉积（HFCVD）进一步用于生长更大的金刚石微晶。我们将这些结果与未对碳纤维进行激光处理所得到的结果进行了比较。本文详细介绍了金刚石转化和HFCVD生长的过程。
We report a pulsed laser annealing method to convert carbon fibers and nanotubes into diamond fibers at ambient temperature and pressure in air. The conversion of carbon nanofibers and nanotubes into diamond nanofibers involves melting in a super undercooled state using nanosecond laser pulses, and quenching rapidly to convert into phase-pure diamond. The conversion process occurs at ambient temperature and pressure, and can be carried out in air. The structure of diamond fibers has been confirmed by selected-area electron diffraction in transmission electron microscopy, electron-back-scatter-diffraction in high-resolution scanning electron microscopy, all showing characteristic diffraction lines for the diamond structure. The bonding characteristics were determined by Raman spectroscopy with a strong peak near 1332 cm(-1), and high-resolution electron-energy-loss spectroscopy in transmission electron microscopy with a characteristic peak at 292 eV for sigma* for sp(3) bonding and the absence of * for sp(2) bonding. The Raman peak at 1332 cm(-1) downshifts to 1321 cm(-1) for diamond nanofibers due to the phonon confinement in nanodiamonds. These laser-treated carbon fibers with diamond seeds are used to grow larger diamond crystallites further by using standard hot-filament chemical vapor deposition (HFCVD). We compare these results with those obtained without laser treating the carbon fibers. The details of diamond conversion and HFCVD growth are presented in this paper.