Abstract: In order to get the graphitization mechanism of diamond under the action of iron-based catalyst, a three-dimensional molecular dynamics (MD) simulation is performed on a particular model containing iron and diamond atoms. And the friction chemical polishing experiments for the chemical vapor deposition (CVD) diamond is conducted to validate the catalytic action of the iron-based metal on diamond graphitization. The results of molecular dynamics simulation show that the presence of iron atoms will reduce the transformation temperature of diamond graphitization. By analyzing the microstructure, the graphitization mechanism with catalyst can be concluded that the chemical bonds are formed by the interaction between the unpaired electrons in the valence shell of iron atoms and the electrons of diamond atoms, which will attract the diamond atoms and make them become graphite structure gradually. For the mechanism of the catalysis of iron for diamond graphitization, there are two critical reasons. On one hand, there are unpaired electrons in the valence shell of the catalytic metal atoms. On the other hand, the structures of the catalytic metal and the diamond conform to the principle of alignment. The experimental results further validate the correctness of the simulation conclusion. Therefore it is concluded that the presence of iron will accelerate the process of diamond graphitization, which is good for the ultra-precision machining of diamond tools.

Key words: catalysis, diamond, graphitization, molecular dynamics