With the extensive application of nuclear technology in medical field, the demand for radiation protection materials has been increasing. Traditional lead-based protective materials suffer from disadvantages such as heavy weight and biological toxicity, making the development of lightweight, lead-free and flexible X-ray protective materials a research priority.

This study aims to investigate the X-ray shielding mechanism and develop high-performance flexible protective materials suitable for medical diagnostic X-ray tubes operating within voltages below 150 kV.

Firstly, the mass attenuation coefficients of different elements were calculated using XCOM program, revealing complementary K-edge absorption effects among tungsten (W), bismuth (Bi), and gadolinium (Gd) elements across different energy ranges. Secondly, Monte Carlo simulations were employed to predict the shielding performance of W, Bi, and Gd element combinations for X-ray tubes operating under 120 kV tube voltage with 2.7 mm Al filtration. Finally, flexible protective materials comprising W+Bi-based composite layered with Gd-based materials were prepared and experimentally tested.

Experimental test results show that the optimized composite material achieves excellent shielding performance with shielding efficiency of 82.98%, mass attenuation coefficient of 5.86 cm²·g^-1, linear attenuation coefficient of 9.16 cm^-1 and half value layer of 0.08 cm. The effective atomic number (Z_eff) analysis confirms enhanced absorption in the 50~90 keV range, which corresponds to the typical energy range of medical diagnostic X-rays.

Results of this study demonstrate that the material design strategy based on complementary K-edge absorption effects can effectively improve the performance of flexible X-ray protective materials to shield both bremsstrahlung and characteristic radiation in the X-ray spectrum, providing valuable insights for developing next-generation lightweight, lead-free, and flexible X-ray protective materials for medical applications.