Exploring Carbon New phases by Laser-Induced Shock Waves

采用基于冲击枪技术的SCARQ（冲击压缩和快速淬火）方法制备金刚石亚稳相--非晶和纳米晶金刚石，并将该方法应用于本研究开发的激光冲击技术。研究了两种激光冲击方法，一种是直接利用激光诱导烧蚀压力，另一种是利用激光驱动飞片撞击，后者是利用高功率Nd：YAG脉冲激光加速薄铝箔，撞击一定距离放置的PMMA窗口。飞行器的到达时间由一台扫描相机检测。到达时间的空间变化揭示了弯曲的飞片形状取决于激光能量分布，从而导致速度分布。此外，这些分布强烈依赖于距激光焦点的距离。因此，难以将焦点尺寸减小到小于0.1mm，其值是实现50 GPa的金刚石转变压力所需的。采用一维流体动力学程序对实验数据进行了计算机模拟，并利用拉曼散射研究了激光冲击压缩富勒烯薄膜后的结构变化。为了研究材料在冲击波作用下的动态反应过程，研制了一种精确测量冲击波温度的红外辐射计。为了确定红外辐射计，四氯化碳的冲击温度测量进行低于10 GPa，结果证实，该系统可用于测量相对温和的冲击温度低于1000 K。然而，该系统可能是在较高的温度下，在激光冲击的情况下，因为小的冲击压缩面积。

Metastable phases of diamond, amorphous and nanocrystalline diamond, were produced by SCARQ (shock compression and rapid quenching) method based on the shock-gun technology, This method was also applied to a laser-shock technology, which was developed in this study. Two-types of laser-shock method were investigated ; one was the direct use of laser-induced ablation pressures, and the other was the use of the laser-driven flyer impact, For the latter, thin aluminum foils were accelerated by a high power Nd : YAG pulse laser and impacted PMMA window placed at a certain distance. Arrival time of the flyers was detected by a streak camera. Spatial changes in the arrival time revealed the curved flyer shape depending on the laser energy distribution which resulted in velocity distribution. Moreover, these profiles were strongly dependent on the distance from focal point of laser. Therefore, it was difficult to reduce the focal spot size less than 0.1 mm whose value was required for achieving the diamond transition pressure of 50 GPa. These experimental data were described by computer simulation based on one-dimensional hydro-code.The structural change of fullerene films subjected to laser-shock compression using the laser was investigated by Raman scattering. Some samples transformed into fullerene polymer, and the photo-induced structural change of fullerene was also investigated.An infrared radiometer for the accurate measurement of shock temperature was developed in order to investigate shock-induced, dynamic reaction processes of materials. To determine the IR-radiometer, the shock temperature measurements of carbon tetrachloride were conducted below 10 GPa, and the results confirmed that the system was available to measure relatively moderate shock temperatures lower than 1000 K.However, the system might be available at higher temperature in the case of laser-shock because of the small shock-compressed area.