Collision-based synthesis of diamond-graphite nanocomposites: computational investigation

Diamond-graphite nanocomposites have attracted significant attention due to their unusual structure, combining graphitic and diamond domains within a single material, as well as their promising electronic and mechanical properties. However, existing synthesis routes typically rely on poorly controlled high-pressure, high-temperature phase transitions, limiting the ability to "tune" the relative proportions of graphite and diamond. Here, we explored an alternative strategy that avoids bulk phase transformations and instead targets the formation of interfaces between pre-existing graphite and diamond domains under shock conditions, such as those generated by high-speed collisions. Using molecular dynamics simulations of simplified particle-particle impacts, we assessed the feasibility of collision-driven interfacial bonding under idealised conditions across multiple diamond facets and graphite orientations. In principle, collisions should generate localised interfacial heating that promotes bond formation without necessarily disrupting the internal structure of either domain. For hydrogen-terminated surfaces, the average relative collision velocity that should result in formation of a coherent interface was estimated to be approximately 2500 m s^-1, with lower values expected upon appropriate surface functionalisation. At higher velocities, graphitic layers undergo significant deformation and transition toward a diamond-like amorphous phase, with thresholds of approximately 3246 m s^-1 for [0001]_G and 3810 m s^-1 for [101̄0]_G, in good agreement with prior studies. Overall, this work provides a theoretical argument for an alternative diaphite synthesis route based on controlled interfacial reactions rather than bulk phase changes. Such an approach may enable improved control over domain sizes and phase composition. Synthesis techniques such as thermal spraying, spark plasma sintering, and explosive powder compaction may prove useful in its implementation.