In a recent breakthrough, Dr. HUO Zhipeng and his student CHEN Zuoyang from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences have developed a new class of PbWO₄ filler-reinforced B₄C/HDPE composites with tunable microstructures.

By precisely regulate the microstructure of PbWO₄ fillers, they achieved enhanced synergistic radiation shielding performance against both neutron and gamma radiation, while elucidating the correlation mechanisms between the microstructure and thermal, mechanical, radiation shielding properties, and service durability of the shielding composites.

The results were published in Composites Part A: Applied Science and Manufacturing.

The demand for advanced radiation shielding materials has surged with the growing applications in nuclear energy, medical radiotherapy, and aerospace exploration. Neutron and gamma radiation—two prevalent and hazardous forms of ionizing radiation—pose significant risks to human health and sensitive equipment. Conventional shielding materials often fall short, offering limited protection against only one type of radiation or exhibiting poor mechanical integrity and aging resistance.

In this study, by synthesizing PbWO₄ fillers with varied microstructures through controlled reaction conditions, the researchers achieved distinct microscopic morphologies such as micron spindle-shaped PbWO₄-I, micron spherical PbWO₄-II and rough micron spherical PbWO₄-III. Among them, the micron-scale rough spherical PbWO₄-III filler exhibited superior characteristics such as increased specific surface area, more uniform particle distribution, and better dispersion within the polymer matrix.

This microstructural refinement improved interfacial bonding, leading to enhanced thermal stability, mechanical properties, and ultra violet aging resistance. Pb and W atoms in PbWO₄ fillers effectively absorb gamma photons and fast neutrons, while B atoms in B₄C fillers provides high thermal neutron absorption. The resulting composite thus offers enhanced synergistic shielding across a broad neutron energy spectrum and gamma ray.

The optimized PbWO₄-III/B₄C/HDPE composite achieved a 97.32% shielding rate against ²⁵²Cf neutrons and 76.43% against ¹³⁷Cs gamma photons at a thickness of 15 cm. These results represent a significant improvement over conventional materials, which typically lack this combination of synergistic shielding and robust mechanical performance.

This work not only demonstrates the importance of microstructure control in composite design but also provides a promising strategy for next-generation, high-performance radiation protection materials, according to the team. 

Figure 1. SEM images of micron spindle-shaped PbWO₄-I (a), micron spherical PbWO₄-II (b), rough micron spherical PbWO₄-III (c), commercial PbWO₄ (d). (Image by HUO Zhipeng)

Figure 2. Schematic diagram of synergistic shielding mechanism of neutrons and gamma photons interacting with the PbWO₄ filler-reinforced composites. (Image by HUO Zhipeng)