Interlocked Graphene-Graphite Architectures for High Thermal Conductivity Enabled by Extended Phonon Lifetimes.

Interfacial phonon transport critically influences the thermal performance of carbon-based materials for advanced thermal management. Here, the thermal transport properties of interlocked graphene/graphite structures are investigated using nonequilibrium molecular dynamics simulations and compared with pristine bilayer graphene. The interlocked structures are constructed based on experimentally motivated graphene-to-graphite length ratios (1.25:1) and interlayer spacings derived from XRD measurements. Thermal conductivity is evaluated over system lengths ranging from 50 to 1000 nm using optimized-Tersoff, ReaxFF, and hybrid neural network (hNN-Grx) interatomic potentials. Both optimized-Tersoff and hNN-Grx potentials predict a substantial thermal conductivity enhancement of approximately 20-27% in interlocked graphene/graphite architectures compared to pristine bilayer graphene. This improvement is attributed to phonon bridging across interfaces. In contrast, ReaxFF significantly underestimates absolute values. While the optimized-Tersoff potential captures interlayer phonon effects only at large system sizes (>600 nm), the hNN-Grx potential resolves these mechanisms even at short lengths. Phonon transport is further analyzed via spectral energy density maps and phonon linewidth calculations for transverse acoustic (TA) and flexural acoustic (ZA) modes. The interlocked graphene/graphite structures exhibit sharper phonon dispersion ridges and reduced phonon linewidth values, indicating longer phonon lifetimes and suppressed anharmonic scattering, particularly for low-q ZA modes. These lifetime enhancements provide a microscopic explanation for the superior thermal conductivity of interlocked graphene/graphite (GG) architectures.