Lightweight and Flexible Bi@Bi-La Natural Leather Composites with Superb X-ray Radiation Shielding Performance and Low Secondary Radiation

Integrating high-Z elements and multilayer structures into composite films with interlayer scattering effects for high-energy X-ray shielding

High-energy ionizing radiation brings serious challenges to medical professionals, and it demands efficient and lightweight shielding materials depending on high-Z elements and structural supporting matrices. Herein, we have integrated multiple high-Z elements and multilayer structures into composite films with interlayer scattering effects for constructing high-energy X-ray shielding clothes. A series of composite films containing different combinations of X-ray shielding particles (SnO2, BaSO4, and Bi2O3) were prepared in tightly connected two layers with each layer consisting of corresponding hybrid polyacrylonitrile (PAN) fibers-reinforced hybrid thermoplastic polyurethane (TPU) coating. The optimized composite film LBa3.7/LBi3.7 avoids lead toxicity and has a tensile strength of 17.92 MPa and high flexibility due to the reinforcing effect of PAN hybrid fibers. The LBa3.7/LBi3.7 with a density of ∼ 2.98 g cm-3 and a thickness of 2.24 mm exhibits 18 % lighter than the 0.5 mmPb lead apron. Owing to the combination of multiple particles and layer structures, the absorption and interlayer scattering effects of LBa3.7/LBi3.7 are leveraged to confer a high X-ray shielding efficiency of 96.3 % at 100 keV, surpassing single-element films and closing to 0.5 mmPb lead apron. This work offers a viable strategy for developing flexible, lightweight, and efficient wearable materials for high-energy X-ray shielding.

Progress in Flexible and Wearable Lead-Free Polymer Composites for Radiation Protection

The rapid development of nuclear technology has brought convenience to medical, industrial, and military fields. However, long-term exposure to a radiation environment with high energy will result in irreversible damage, especially to human health. Traditional lead-based radiation protection materials are heavy, inflexible, inconvenient for applications, and could lead to toxicity hazards and environmental problems. Therefore, it has become a mainstream topic to produce high-performance shielding materials that are lightweight, flexible, and wearable. Polymer composites are less dense and have excellent flexibility and processability, drawing great interest from researchers worldwide. Many attempts have been made to blend functional particles and polymeric matrix to produce flexible and wearable protection composites. This paper presents an extensive overview of the current status of studies on lead-free polymer composites as flexible and wearable protection materials. First, novel functional particles and polymer matrices are discussed, and recent results with potential applications are summarised. In addition, novel strategies for preparing polymeric shielding materials and their respective radiation shielding properties are analyzed. Finally, directions for developing lead-free polymeric shielding materials are indicated, and it is beneficial to provide additional references for obtaining flexible, lightweight, and high-performance wearable shielding materials.

Bi2O3/Gd2O3 Meta-Aerogel with Leaf-Inspired Nanotrap Array Enables Efficient X-Ray Absorption

The increasing utilization of X-rays has generated a growing need for efficient shielding materials. However, the existing Pb-based materials suffer from a narrow X-ray absorbing range, high weight, and rigidity. Inspired by the natural leaf, which can efficiently absorb light through chlorophyll and carotenoids in confined cells, we engineer ultralight and superelastic nanofibrous Bi2O3/Gd2O3 meta-aerogels (BGAs) with X-ray nanotrap arrays by manipulating the 3D confined assembly of 1D Bi2O3 and Gd2O3 nanofibers. The BGAs can synergistically absorb X-ray photons from complementary energy ranges into the nanotraps and induce cyclic collisions with Bi2O3 and Gd2O3 nanofibers, maximizing the effective X-ray attenuation. The meta-aerogel exhibits the integrated performance of efficient X-ray shielding efficiency (60-83%, 16-90 keV), ultralow density (10 mg cm-3), and superelasticity. The production of these meta-aerogels presents an avenue for the development of next-generation X-ray protective materials and the resolution of X-ray imaging systems.

Multicomponent X-ray Shielding Using Sulfated Cerium Oxide and Bismuth Halide Composites

Lead is the most widely used X-ray-shielding material, but it is heavy (density ≈ 11.34 g/cm3) and toxic. Therefore, the replacement of Pb with lightweight, ecofriendly materials would be beneficial, and such materials would have applications in medicine, electronics, and aerospace engineering. However, the shielding ability of Pb-free materials is significantly lower than that of Pb itself. To maximize the radiation attenuation of non-Pb-based shielding materials, a high-attenuation cross-section, normal to the incoming X-ray direction, must be achieved. In this study, we developed efficient X-ray-shielding materials composed of sulfated cerium oxide (S-CeO2) and bismuth halides. Crucially, the materials are lightweight and mechanically flexible because of the absence of heavy metals (for example, Pb and W). Further, by pre-forming the doped metal oxide as a porous sponge matrix, and then incorporating the bismuth halides into the porous matrix, uniform, compact, and intimate composites with a high-attenuation cross-section were achieved. Owing to the synergetic effect of the doped metal oxide and bismuth halides, the resultant thin (approximately 3 mm) and lightweight (0.85 g·cm-3) composite achieved an excellent X-ray-shielding rate of approximately 92% at 60 kV, one of the highest values reported for non-heavy-metal shielding materials.

Investigation on Physico Chemical and X-ray Shielding Performance of Zinc Doped Nano-WO3 Epoxy Composite for Light Weight Lead Free Aprons

This report addresses a way to reduce the usage of highly toxic lead in diagnostic X-ray shielding by developing a cost-effective, eco-friendly nano-tungsten trioxide (WO₃) epoxy composite for low-weight aprons. Zinc (Zn)-doped WO₃ nanoparticles of 20 to 400 nm were synthesized by an inexpensive and scalable chemical acid-precipitation method. The prepared nanoparticles were subjected to X-ray diffraction, Raman spectroscopy, UV-visible spectroscopy, photoluminescence, high-resolution-transmission electron microscope, scanning electron microscope, and the results showed that doping plays a critical role in influencing the physico-chemical properties. The prepared nanoparticles were used as shielding material in this study, which were dispersed in a non-water soluble durable epoxy resin polymer matrix and the dispersed materials were coated over a rexine cloth using the drop-casting method. The X-ray shielding performance was evaluated by estimating the linear attenuation coefficient (μ), mass attenuation coefficient (μ_m), half value layer (HVL), and X-ray percentage of attenuation. Overall, an improvement in X-ray attenuation in the range of 40-100 kVp was observed for the undoped WO₃ nanoparticles and Zn-doped WO₃ nanoparticles, which was nearly equal to lead oxide-based aprons (reference material). At 40 kVp, the percentage of attenuation of 2% Zn doped WO₃ was 97% which was better than that of other prepared aprons. This study proves that 2% Zn doped WO₃ epoxy composite yields a better particle size distribution, μ_m, and lower HVL value and hence it can be a convenient lead free X-ray shielding apron.

Ultralight and Superelastic Gd2O3/Bi2O3 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/Bi₂O₃ nanofibers (brick) and Gd₂O₃ 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.

Preparation and Performance Evaluation of X-ray-Shielding Barium Sulfate Film for Medical Diagnosis Using PET Recycling and Multi-Carrier Principles

The use of disposable containers and packaging materials has increased due to the recent COVID-19 pandemic. Thus, the generation of plastic waste is also increasing, and research on recycling such waste is being actively conducted. In this study, an X-ray-shielding film for medical diagnosis was manufactured by mixing a radiation-shielding material and a plastic waste-based polymer material and its effectiveness was evaluated. The film, which is intended as a fabric for a shielding garment, consists of barium sulfate (BaSO4) shielding nanoparticles embedded in a matrix of polyethylene terephthalate (PET), a commonly available waste plastic material. A particle-dispersing technology, which can improve the ratio between the shielding and matrix materials while maintaining the tensile strength of the film, was studied. Therefore, to increase the content of the barium sulfate (BaSO4) nanoparticles used as the shielding material, this multi-carrier method—under which the particles are dispersed in units of time—was developed to improve the shielding performance. Compared with the effectiveness of lead (Pb) shielding film, the 3 mm barium sulfate film developed in this study satisfies the lead equivalent of 0.150 mmPb when stacked in two layers. Therefore, a shielding film was successfully manufactured by using plastic waste as a polymer resin and barium sulfate, an eco-friendly radiation-shielding material, instead of lead.

Leather for flexible multifunctional bio-based materials: a review

Nowadays, diverse leather usage conditions and increasing demands from consumers challenge the leather industry. Traditional leather manufacturing is facing long-term challenges, including low-value threshold, confined application fields, and environmental issues. Leather inherits all the biomimetic properties of natural skin such as flexibility, sanitation, cold resistance, biocompatibility, biodegradability, and other cross-domain functions, achieving unremitting attention in multi-functional bio-based materials. Series of researches have been devoted to creating and developing leather-based flexible multi-functional bio-materials, including antibacterial leather, conductive leather, flame-retardant leather, self-cleaning leather, aromatic leather, and electromagnetic shielding leather. In this review, we provide a comprehensive overview of the commonly used leather-based functional materials. Furthermore, the possible challenges for the development of functional leathers are proposed, and expected development directions of leather-based functional materials are discussed. This review may promote and inspire the emerging preparation and applications of leather for flexible functional bio-based materials.

Graphical Abstract

Polyurethane-based retanning agents with antimicrobial properties

Polyurethane-based retanning agents with antimicrobial properties were synthesized by the chemical incorporation of ciprofloxacin (CPFX) units into polyurethane chains. The chemical structures were characterized by Fourier transform infrared (FTIR) and gel permeation chromatography (GPC). Then, the retanning agents were applied in the leather retanning process. Owing to the conjugation of CPFX into polyurethane chains, the molecular weight increases, further leading to the decrease in hydroxyl value and increase in particle size. The shrinkage temperature was improved after retanning. Owing to the filling of retanning agents in the gap of collagen fibers, the average thickness of leather increased by 65.8%. The mechanical properties of leather were visibly improved because of the large number of –COOH coordinate with Cr3+ and more hydrogen crosslinking with carboxyl group, amino group, and hydroxyl group of leather collagen. Furthermore, leather retanned by these polyurethane-based retanning agents presented good antimicrobial properties. The antibacterial activity could be conserved above 89% even after rinsing for ten times.

Manufacturing and performance evaluation of medical radiation shielding fiber with plasma thermal spray coating technology

Lead, which has been used for radiation shielding in medicine, is currently sought to be replaced by an eco-friendly shielding material. Therefore, it should be replaced with shielding materials possessing excellent processability and radiation shielding performance similar to that of lead. In this study, a new process technology was developed focusing on the processability of tungsten, a representative eco-friendly shielding material. It is difficult to reproduce the shielding performance when using the method of coating nonwoven fabrics with a liquid using tungsten powder on a polymer material, which is adopted to ensure the flexibility of the shielding fabric. To address this, tungsten powder was sprayed on the fabric using a plasma thermal spray coating process and coated to a thickness of 0.2 mm to evaluate the shielding performance. Compared to standard lead with a thickness of 0.2 mm, the shielding efficiency differed by approximately 15%. Since the developed process can maintain the amount of injection in an area, it is possible to ensure the reproducibility of the shielding performance and automated process for mass production. This approach is economically feasible as it does not entail the mixing of polymer materials; hence, it can be used for preparing radiation shielding clothing for medical institutions.

Shielding of Cosmic Radiation by Fibrous Materials

Cosmic radiation belongs to the challenges engineers have to deal with when further developing space travel. Besides the severe risks for humans due to high-energy particles or waves, the impact of cosmic radiation on electronics and diverse materials cannot be neglected, even in microsatellites or other unmanned spacecraft. Here, we explain the different particles or waves found in cosmic radiation and their potential impact on biological and inanimate matter. We give an overview of fiber-based shielding materials, mostly applied in the form of composites, and explain why these materials can help shielding spaceships or satellites from cosmic radiation.