碳原料结构对激光法合成纳米金刚石的影响

为了确定在较低激光能量密度下（10^6W／cm^2）激光法合成纳米金刚石最适宜的碳原料，研究了三种结构不同的碳原料（炭黑、片状石墨、土状石墨）对合成纳米金刚石的影响，采用拉曼光谱对碳原料的结构进行了分析，结果显示炭黑、土状石墨和片状石墨这三种碳原料的结晶程度依次增强，用Nd：YAG脉冲激光分别轰击不同碳原料的悬浮液，实验产物的透射电镜分析显示在激光照射炭黑和片状石墨的产物中没有金刚石生成，而在激光照射石墨的产物中发现了立方结构的金刚石，其颗粒尺寸约为5Bin．因此，在10^6W／cm^2的脉冲激光作用下，无序炭黑和结晶较完整的片状石墨均不利于合成金刚石，只有有序化程度适中的土状石墨有利于合成金刚石．

Effects of Carbon Material Structures on the Nanodiamond Synthesis by Laser Irradiation

Diamond crystals in nanometric range have been synthesized in graphite suspension by pulsed laser irradiation,and the effects of three kinds of carbon material( carbon black,crystalline flake graphite and mi- crocrystalline graphite)on the formation of diamond are analyzed.The structures of the carbon materials are characterized by Raman spectra which show that the crystallization degree increases from carbon black,micro- crystalline graphite to crystalline flake graphite in turn.The structures of the products after Nd:YAG laser irra- diation are characterized by transmission electron microscopy(TEM).The experiment results show that only mi- crocrystalline graphite by laser transformed into diamond( cubic diamond about 5 nm)in the three carbon mate- rials.It also demonstrates that microcrystalline graphite is more advantageous in the synthesis of nanodiamond than carbon black and crystalline flake graphite when the laser power density is 10~6 W/cm~2.