Ultralight and Superelastic Gd 2 O 3 /Bi 2 O 3 Nanofibrous Aerogels with Nacre-Mimetic Brick-Mortar Structure for Superior X-ray Shielding.

The widespread use of X-rays has prompted a surge in demand for effective and wearable shielding materials. However, the Pb-containing materials currently used to shield X-rays are commonly bulky, hard, and biotoxic, severely limiting their applications in wearable scenarios. Inspired by the nacre, we report on ultralight, superelastic, and nontoxic X-ray shielding nanofibrous aerogels with microarch-engineered brick/mortar structure by combining polyurethane/Bi 2 O 3 nanofibers (brick) and Gd 2 O 3 nanosheets (mortar). The synergistic attenuation effect toward X-rays from the reflection of microarches and absorption of Bi/Gd elements significantly enhances the shielding efficiency of aerogels, and microarches/robust nanofibrous networks endow the materials with superelasticity. The resultant materials exhibit integrated properties of superior X-ray shielding efficiency (91-100%), ultralow density (52 mg cm -3 ), large stretchability of 800% reversible elongation, and high water vapor permeability (8.8 kg m -2 day -1 ). The fabrication of such novel aerogels paves the way for developing next-generation effective and wearable X-ray shielding materials.