Diamond synthesis by hydrogen reducing tantalum oxide in graphite at atmospheric pressure

Traditional methods of transforming graphite into diamond, such as high-pressure, high-temperature techniques, require expensive equipment and conditions. Here, we present a novel method for synthesizing diamond from graphite at atmospheric pressure by employing magnetron sputtering to deposit tantalum (Ta) atoms onto graphite flakes, followed by hydrogen plasma treatment and annealing. Secondary ion mass spectrometry measurements confirm that the hydrogen plasma treatment incorporates hydrogen atoms into the graphite matrix and the content of tantalum oxide formed during the transfer from the sputter equipment to plasma treatment dramatically decreases after annealing. The x-ray photoelectron spectroscopy analysis reveals that the annealing process effectively reduces tantalum oxide in graphite to monodisperse tantalum atoms. As the annealing time increases, both the content of monodisperse Ta and the proportion of sp3 carbon structures rise. Transmission electron microscopy results show the formation of diamond grains with sizes ranging from 10 to 30 nm. This indicates that the increase in monodisperse Ta atoms facilitates the graphite-to-diamond transformation, suggesting that hydrogen-reduced Ta atoms play a key role in enhancing the efficiency of this phase transition. Our method offers a promising and cost-effective route for synthesizing diamond from graphite under atmospheric pressure.