Critical Thickness and Its Role in the Spheroidization of Natural Flake Graphite

ABSTRACT For decades, the industry has believed that spherical graphite (SG) yield correlates strongly with graphite flake size. To clarify natural graphite (NG) spheroidization mechanisms, a comprehensive evaluation was conducted by extracting intermediate products from an industrial production line and utilizing separated jet mills to simulate continuous processing in the study. Focused ion beam‐scanning electron microscope (FIB‐SEM) cross‐sectional analysis and nanocomputed tomography (Nano‐CT) imaging revealed that flakes of different thicknesses underwent distinct morphological changes (folding, bending, or fragmentation) under mechanical force, with only flakes above a critical thickness (∼2 μm) forming SG cores. Statistical correlation between thickness (measured via statistical method under SEM) and yield demonstrated that thickness—not only size—is the dominant factor, redefining “effective SG flakes” to include small but thick flakes. Therefore, prioritizing thickness protection over size preservation in grinding‐flotation and spheroidization processes increased SG yield by 7% in industrial validation. The work provides new insights for high‐efficiency SG production.