Polymer nanocomposites containing β‐Bi 2 O 3 and silica nanoparticles: Thermal stability, surface topography and X‐ray attenuation properties

Green route synthesis and characterization of β-Bi2O3/SiO2 and β-Bi2O3/Bi2O2.75/SiO2 using Juglans regia L. shell aqueous extract and photocatalytic properties for the degradation of RB-5

Background

Photocatalyst oxides added with silicon improve their photocatalytic properties. In this research, nanostructured β-Bi2O3/SiO2 and β-Bi2O3/Bi2O2.75/SiO2 were obtained by means of a green method mediated by the using the aqueous extract of J. regia shell as the source of reducing biomolecules and as a natural source of plant silicon.

Method

The β-Bi2O3/SiO2 and β-Bi2O3/Bi2O2.75/SiO2 nanostructures were characterized by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction, high-resolution transmission electron microscopy (HR-TEM), field emission scanning electron microscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), and photoluminescence spectroscopy. The photocatalytic activity was measured by the degradation of Reactive Black 5 dye (RB-5).

Results

FT-IR and XPS demonstrated the presence of plant silicon in the bismuth oxide photocatalysts. HR-TEM showed that the crystal size of the as-synthesized materials is ~ 25 nm and revealed that the β-Bi2O3 synthesized with ground shell extract and heat-treated at 300 °C contains the Bi2O2.75 phase. Good photocatalytic activity was found in all the studied materials; particularly, the heat-treated nanostructures showed excellent properties resulting in 92% degradation of RB-5 under UV–Vis light after 15 min of exposure, and 98% after 180 min.

Conclusions

The findings of this research suggest that the metabolites coating the Bi2O3, which generate a large amount of hydroxyl radicals, the plant silicon content, and the crystalline defects conferred by the synthesis medium, all contribute to the improved degradation of the azo dye, providing the nanostructures with better photocatalytic activity.

Evaluation of Micro- and Nano-Bismuth(III) Oxide Coated Fabric for Environmentally Friendly X-Ray Shielding Materials

This research focuses on the development of environmentally friendly textile-based shielding composites, from micro-sized and nanosized Bi₂O₃ particles, against ionizing radiation. Polyester fabric dyne-coated with either micro- or nano-Bi₂O₃ particles shields some X-rays but the effectiveness is poor. With only ∼58% uptake of micro-sized Bi₂O₃ particles dyeing on polyester fabric, the insufficient amount of Bi₂O₃ leaded to the low density of particles, resulting in only 30% of X-ray shielding at 80 kVp. Cotton fabric coated with either micro- or nano-Bi₂O₃/poly(vinyl alcohol) (PVA) composites, on the other hand, demonstrated the capacity to attenuate X-ray generated by high diagnostic X-ray tube voltages of 70-100 kVp, in compliance with medical protection requirements. The X-ray attenuation performance of cotton fabric coated with either micro-Bi₂O₃/PVA or nano-Bi₂O₃/PVA nanocomposite decreased progressively with increasing tube acceleration voltages, however their ionizing radiation-shielding performance enhanced with the number of fabric layers. Interestingly, for all X-ray tube voltages evaluated, the micro-Bi₂O₃/PVA composite outperformed the nano- Bi₂O₃/PVA composite in terms of X-ray shielding. At a weight ratio of 66.7% Bi₂O₃, 10 layers of cotton fabric coated with micro- Bi₂O₃/PVA composite can attenuate 90, 85, and 80% of X-ray photons at 70, 80, and 100 kVp, respectively. As a result, these less harmful X-ray shielding materials have the potential to replace lead-based composites, which are highly toxic to human health and have negative environmental consequences.

X-ray Shielding, Mechanical, Physical, and Water Absorption Properties of Wood/PVC Composites Containing Bismuth Oxide

The potential utilization of wood/polyvinyl chloride (WPVC) composites containing an X-ray protective filler, namely bismuth oxide (Bi₂O₃) particles, was investigated as novel, safe, and environmentally friendly X-ray shielding materials. The wood and Bi₂O₃ contents used in this work varied from 20 to 40 parts per hundred parts of PVC by weight (pph) and from 0 to 25, 50, 75, and 100 pph, respectively. The study considered X-ray shielding, mechanical, density, water absorption, and morphological properties. The results showed that the overall X-ray shielding parameters, namely the linear attenuation coefficient (µ), mass attenuation coefficient (µ_m), and lead equivalent thickness (Pb_eq), of the WPVC composites increased with increasing Bi₂O₃ contents but slightly decreased at higher wood contents (40 pph). Furthermore, comparative Pb_eq values between the wood/PVC composites and similar commercial X-ray shielding boards indicated that the recommended Bi₂O₃ contents for the 20 pph (40 ph) wood/PVC composites were 35, 85, and 40 pph (40, 100, and 45 pph) for the attenuation of 60, 100, and 150-kV X-rays, respectively. In addition, the increased Bi₂O₃ contents in the WPVC composites enhanced the Izod impact strength, hardness (Shore D), and density, but reduced water absorption. On the other hand, the increased wood contents increased the impact strength, hardness (Shore D), and water absorption but lowered the density of the composites. The overall results suggested that the developed WPVC composites had great potential to be used as effective X-ray shielding materials with Bi₂O₃ acting as a suitable X-ray protective filler.

Micro and nano Bi2O3 filled epoxy composites: Thermal, mechanical and γ-ray attenuation properties

Polymer composites have attracted considerable attention as potential light-weight and cost-effective materials for radiation shielding and protection. In view of this, the present work focusses on development of lead-free composites of diglycidyl ether of bisphenol A (DGEBA) epoxy resin with micro (~ 10 μm) and nano (~ 20 nm) bismuth (III) oxide (Bi₂O₃) fillers, using solution casting technique. Thermal, mechanical and γ-ray attenuation properties of the composites were studied by varying the filler loading. Inclusion of the fillers into epoxy matrix was confirmed both structurally and morphologically by XRD and SEM, respectively. Thermogravimetric analysis (TGA) showed the thermal stability of composites to be as high as 400 °C. The nanocomposites exhibited relatively higher thermal stability than their micro counterparts. Among the composites, 14 wt% nano-Bi₂O₃/epoxy composites showed highest tensile strength of 326 MPa, which is about 38% higher than 30 wt% micro Bi₂O₃/epoxy composites. Mass attenuation coefficients (μ/ρ) of the composites were evaluated at γ-ray energies ranging from 0.356 to 1.332 MeV. Nanocomposites showed better γ-ray shielding at all energies (0.356, 0.511, 0.662, 1.173, 1.280 and 1.332 MeV) than micro composites with same filler loading. These studies revealed the significance of nano-sized fillers in enhancing overall performance of the composites.