One‐Pot Mechanochemical Dual‐Functionalization of Bi Powder: Constructing High‐Loading Flake Bi@PDMS Composites for Sustainable Lead‐Free X‐Ray Shielding Applications

To address the limitations of traditional lead shielding (toxicity, weight) and unmodified bismuth fillers (poor dispersion), this study develops an improved “one‐pot” ball milling method. This one‐pot strategy effectively achieves in‐situ silane (vinyltrimethoxysilane, A171) modification and transforms bismuth powder into a flake‐like morphology. Here, A171 bonds covalently to the bismuth surface via Si─O─Bi linkages, thereby converting bismuth from hydrophilic to hydrophobic. This dual functionalization enables uniform dispersion of Bi in polydimethylsiloxane (PDMS) at a high filler loading of 70 wt% while retaining excellent mechanical flexibility (tensile strength 0.42 MPa, elongation 166%), thermal stability (30 °C higher than that of pure PDMS), and fatigue resistance. The flake‐like modified Bi (M‐Bi) forms a 3D shielding network that extends X‐ray propagation paths. The resulting 0.2 cm‐thick 70M‐Bi@PDMS composite exhibits 92% X‐ray shielding efficiency for 60 keV X‐rays, with corresponding linear (μ) and mass (µm) attenuation coefficients of 13.30 cm −1 and 3.50 cm 2 g −1 , respectively, and 75% shielding efficiency at 80 keV. In terms of radiation shielding performance, it outperforms commercial lead shielding materials. This work provides a potentially scalable method for developing lead‐free, lightweight, and flexible X‐ray shielding materials for wearable applications.