激光诱导合成金刚石的机理

THE MECHANISM TO SYNTHESIZE DIAMOND BY LASER INTRODUCING

文章对激光诱导合成金刚石的机理进行了多方面的较深入的探索。首次估算了石墨直接转化金刚石所必须越过的势垒值为8.565×104J.m o-l 1。说明了宏观高压并非是这一转化的必要条件。对于激光诱导合成金刚石,其激光源的功率密度不应低于2.534×105W.cm-2。提出并计算了有利于激光诱导合成金刚石的若干因素:靶前激光维持爆轰波的压力可达几个GPa数量级;粒径为4nm的石墨微粒,其晶体本身表面高压可达3.32GPa;石墨被加热后,其晶体自身的热压力可达几百M Pa;晶体表面原子振幅远大于体内,其动能可达1.6×1-0 19J;被激光照射时,石墨原子的平均振幅大到常温时的8倍以上。用细微石墨颗粒作原料更易于合成金刚石。将宏观的热力学理论与微观的物质结构及相变的微观机理结合起来,能较好地阐明该相变机理。

In this paper, the mechanism to synthesize diamond by laser introducing has been explored more deeply and in many ways. It has been evaluated for the first time that the minimum potential energy for transforming graphite into diamond is 8. 565 × 10^4J · mol^-1. Macroscopic high pressure is not necessary condition for the transforming. The laser beam power density should not be lower than 2. 534 × 105W ·cm^-2 by using it for introducing graphite to diamond. Some beneficial factors that laser introduce to synthesize diamond have been pointed and calculate： The peak pressure on the surface of target can be up to several GPa grade; For a size of 4nm graphite micrograin, its surface high pressure can be reached 3.32GPa; Its heat pressure can be up to hundreds of MPa while graphite is heating; Atom amplitude on the crystal surface is much larger than inside body, its kinetic energy can be up to 1.6×10^-19J; The mean amplitude of graphite atom is added 8 times than in normal temperature while irradiating by laser; It is more easily for synthesizing diamond by using finer micrograin of graphite. The mechanics on the phase transfer has been explained clearer and deeper by combining material micro structure, micro mechanics of phase transform and macro thermodynamic theory.