Time–Temperature Synergy Driven Kinetic Compensation: Source‐Active Regulation to Break Modulus‐Polarity Trade‐Off for High‐Modulus Carbon Fibers

High‐modulus carbon fibers (HMCFs) are essential for lightweight design in aerospace and advanced engineering applications. However, conventional high‐temperature graphitization delivers ultrahigh modulus but induces severe surface inertness, limiting interfacial bonding in composites performance. Herein, we address this challenge by investigating time–temperature synergistic regulation of HMCF microstructure, surface polarity, and interfacial behavior. HMCFs were fabricated at varied heat‐treatment times (72, 144, 360 s) and temperatures (1700–2500 K), then characterized by XRD, Raman spectroscopy, contact angle, and microdroplet debonding. Results reveal that a kinetic compensation effect driven by time–temperature synergy, where lower temperatures offset by longer times retain high modulus (e.g., 381 GPa at 2000 K/360 s vs. 2200 K/72 s), reducing energy consumption by an estimated 20%–25% compared with conventional high‐temperature processes. This synergy tunes graphite crystallite parameters (crystallinity, La, Lc, orientation) while preserving surface active carbon sites (Sac) and polarity, avoiding excessive inertness. Interfacial shear strength correlates positively with Sac, reaching 40.5 MPa (35% higher than 2200 K/72 s) at 2000 K/360 s, with modulus above 380 GPa. This source‐active regulation effectively mitigates the long‐standing modulus‐polarity trade‐off without passive post‐treatments, guiding scalable green fabrication of high‐performance HMCFs.