【摘要】 针对激光烧蚀碳悬浮液以及液体介质中的石墨靶形成不同尺寸大小的纳米金刚石,对金刚石颗粒的形成进行了分析。基于激光器参数以及合成条件比较分析了两种烧蚀产生的物理化学差异,并根据热力学条件计算了金刚石颗粒的平衡尺寸和激光烧蚀后形成的碳团簇的冷却速度以及Wilson-Frenkel生长定律进一步计算了纳米金刚石的生长速度、生长时间、生长尺寸。计算结果表明,不同参数的激光烧蚀条件下产生的高温高压碳团簇的大小和密度决定了冷却速度以及生长时间,并最终决定了纳米金刚石尺寸。另外根据金刚石晶体最低能量计算结果也验证了超细纳米金刚石形成的理论基础。动力学与热力学理论计算结果和实验结果相一致,合理解释了不同尺寸纳米金刚石的形成。更多还原

【Abstract】 We performe dynamics and thermodynamics analysis on the formation of nanodiamonds (NDs) produced by pulsed-laser ablation (PLA).The analysis on physical and chemical difference arise from two PLA processes based on laser parameters and synthesize methods are carried out,and the equilibrium size is also discussed upon thermodynamics factor as well as the growth velocity,growth time,and the final size of NDs are calculated using the Wilson-Frenkel growth law.The result shows that the radius and density of plasma plume determine the cooling velocity,and the growth time correlates with the cooling velocity when the temperature and pressure are high enough to meet the conditions of the stable growth of NDs.The calculation on the lowest free energy also indicates the formation of NDs is reasonable.Theoretical calculations are in good agreement with experiment results and give a well explanation on the formation of ultrafine NDs.更多还原