Synthesis of diamond from polycyclic aromatic hydrocarbons (anthracene) in the presence of an Fe,Ni-melt at 5.5 GPa and 1450 °C

Abstract

In the present experimental study, the system Fe,Ni–anthracene at 5.5 GPa and 1450 °C was investigated. The experiments were carried out using a multi-anvil split-sphere type high-pressure apparatus (BARS) at 5.5 GPa and 1450 °C. A two-step process was performed. After the first experiment, diamond synthesis took place only in the control sample (Fe,Ni + graphite), but was not identified in the Fe,Ni–anthracene sample: in the latter, anthracene transformed into highly ordered crystalline graphite. The presence of numerous bubbles in the metal evidenced that a large amount of fluid appeared during the run. In the second experiment, the obtained graphite was used as a carbon source that resulted in conversion of graphite to diamond. The morphology of the synthesized diamond is typical for crystals grown in an Fe,Ni–graphite system: it represents a combination of forms {111}, {100}, and {311}. The research confirmed that synthesis of diamond from polycyclic aromatic hydrocarbons (PAHs) is possible at the indicated P–T parameters only by adding a catalyst (Fe–Ni). At the same time, the results demonstrated that the hydrocarbon fluid released after the decomposition of anthracene negatively affects the synthesis of diamond. Therefore, diamond crystallization is possible in two stages: (a) formation of highly ordered graphite and (b) removal of the fluid phase from the reaction zone.