金刚石材料石墨化相变诱导机制研究进展

Research Progress on Induction Mechanism of Graphitization Phase Transition of Diamond Materials

金刚石材料的石墨化行为降低了其加工难度,因此,研究诱导金刚石石墨化的因素有望为金刚石加工技术的革新与开发提供新的线索。总结了激光参数和应力对金刚石石墨化的诱导机制。激光诱导金刚石石墨化主要是指短脉冲激光在金刚石加工过程中的升温诱导,即高能激光引起温度的急剧升高,使金刚石的碳碳键断键重连而形成石墨结构的过程;此外,激光能量密度、脉冲宽度、脉冲数量、激光功率和扫描速率在激光加工过程中相互关联,共同影响金刚石石墨化的过程。应力诱导主要是指抛光或压痕加工过程中,通过增加压力来改变金刚石立方晶体结构的键长和键角而使金刚石结构变得不稳定,随后的再减压过程使碳原子从被压缩的不稳定金刚石相转变为稳定石墨相;此外,过渡金属如铁、铬、钴、镍、铂、钛等对金刚石石墨化相变的催化作用主要表现在金属价层结构中存在的未配对电子和金刚石表层原子的电子配对形成化学键使碳原子移动重构为石墨结构。基于金刚石石墨化诱导机制提出如何改进金刚石材料加工过程中的效率,并根据石墨化特点改善金刚石材料的表面性能。

Surface graphitization behavior of diamond reduces the machining difficulty of diamond materials,thus,research on the factors that induce graphitization of diamond is expected to provide new clues for the technological innovation and development of diamond processing methods.The induction mechanism of laser parameters and stress on diamond graphitization is summarized.Laser induced graphitization mainly refers to the heating induction of short pulse laser during diamond processing,that is,the short pulse laser leads to a sharp raise of temperature,breaks the carbon-carbon bonds of diamond and reconnects them to form graphite structure.In addition,laser energy density,pulse width,number of pulses,laser power and laser pulse repetition frequency are related to each other during laser processing,which together affect the process of diamond graphitization.Stress induction mainly refers to polishing or indentation process,by increasing the pressure to change the bond length and bond angle of the diamond structure to make the diamond structure unstable,and the subsequent decompression process makes its compressed unstable diamond phase change to a stable graphite phase.Moreover,transitional metals such as iron,chromium,cobalt,nickel,platinum,and titanium have catalytic effects on the graphitization phase transition of diamond,which are mainly manifested as:the unpaired electrons in the metal valence layer structure pair with the electrons on the diamond surface to form a chemical bond to further reconstruct the graphite structure.Based on the diamond graphitization induction mechanism,it is proposed how to improve the processing efficiency in the processing of diamond materials and improve the surface properties of diamond materials according to the characteristics of graphitization.