Computational Mapping of the Thermal–Electrical Decoupling Zone in Graphene/Hexagonal Boron Nitride Polymer Nanocomposites

Thermal interface materials for advanced electronics must combine high through‐plane thermal conductivity (κ ≥ 2 W m −1 K −1 ) with strict electrical insulation (σ ≤ 10 −10 S m −1 ). Hybrid graphene/hexagonal boron nitride (h‐BN) fillers can decouple these properties, but the composition–morphology design space has not been mapped systematically. Here, Lewis–Nielsen and McLachlan effective‐medium models are calibrated against a curated literature dataset and used to compute 3D response surfaces and a dimensionless decoupling figure‐of‐merit (DFoM). Within the sampled ranges, the admissible safe zone is narrow: h‐BN loading above ∼30 vol% and graphene below the calibrated electrical percolation threshold (0.30 vol% intrinsically; 0.41 vol% with h‐BN dilution at representative aspect ratio 714). Since the threshold scales inversely with graphene aspect ratio, high‐aspect‐ratio graphene narrows the window, whereas blockier platelets widen it. A compact closed‐form rule, DFoM ≈ √[φh‐BN/(2φgraphene + 0.008)], captures the percolation‐controlled region. The calibrated models are screening‐level rather than quantitative predictors but provide an efficient route for prioritizing hybrid‐filler TIM formulations.