Preparation of self-healing hydrogel toward improving electromagnetic interference shielding and energy efficiency

Abstract

In this study, a self-healing hydrogel was prepared that is transparent to visible (Vis) light while absorbing ultraviolet (UV), infrared (IR), and microwave. The optothermal features of the hydrogel were explored by monitoring temperature using an IR thermometer under an IR source. The hydrogel was synthesized using sodium tetraborate decahydrate (borax) and polyvinyl alcohol (PVA) as raw materials based on a facile thermal route. More significantly, graphene oxide (GO) and graphite-like carbon nitride (g-C3N4) nanostructures as well as carbon microsphere (CMS) were applied as guests to more dissect their influence on the microwave and optical characteristics. The morphology of the fillers was evaluated using field emission scanning electron microscopy (FE-SEM). Fourier transform infrared (FTIR) attested that the chemical functional groups of the hydrogel have been formed and the result of diffuse reflection spectroscopy (DRS) confirmed that the hydrogel absorbs UV while is transparent in Vis light. The achieved result implied that the hydrogel acts as an essential IR absorber due to its functional groups desirable for energy efficiency and harvesting. Interestingly, the achieved results have testified that the self-healing hydrogels had the proper self-healing efficiency and self-healing time. Eventually, microwave absorbing properties and shielding efficiency of the hydrogel, hydrogel/GO, g-C3N4, or CMS were investigated, demonstrating the salient microwave characteristics, originated from the established ionic conductive networks and dipole polarizations. The efficient bandwidth of the hydrogel was as wide as 3.5 GHz with a thickness of 0.65 mm meanwhile its maximum reflection loss was 75.10 dB at 14.50 GHz with 4.55 mm in thickness. Particularly, the hydrogel illustrated total shielding efficiency (SET) > 10 dB from 1.19 to 18 and > 20 dB from 4.37 to 18 GHz with 10.00 mm in thickness. The results open new windows toward improving the shielding and energy efficiency using practical ways.

Dual X-ray- and Neutron-Shielding Properties of Gd2O3/NR Composites with Autonomous Self-Healing Capabilities

“…Nonetheless, despite having Gd 2 O 3 contents of up to 100 phr, the recoverable strengths of the Gd 2 O 3 /NR composites were in the range of 0.30–0.40 MPa, which were in the same order of magnitude as that of pristine NR reported by Xu et al (being in the range of 0.5–0.7 MPa, depending on self-healing times [ 23 ]), implying the useability and potential of the current self-healing materials for applications in radiation protection. Furthermore, the success of the current work could promote further attempts to develop ‘smart’ and more effective materials for use in radiation shielding, along with the previously reported composites of Bi 2 O 3 /PVA, Sm 2 O 3 /PVA, Gd 2 O 3 /PVA, graphene/PVA, and PbO 2 /acrylamide [ 18 , 28 , 49 , 50 ]. It should be noted that the %Recovery values of the NR samples with the addition of Gd 2 O 3 were higher than that of the pristine NR because the original Gd 2 O 3 /NR composite had 2–3 times lower tensile strength than pristine NR, while having similar recoverable strength after self-healing, which resulted in considerably higher %Recovery values for the Gd 2 O 3 /NR composites.…”

Flexible Polypyrrole Nanotube–Polyethylene Glycol–Polyvinyl Alcohol Hydrogels for Enhanced Electromagnetic Shielding

“…PPPg-200 delivers the maximized electromagnetic shielding performance up to 28 dB at the thickness of 2 mm. In Figure 3d, we compare the shielding properties of our prepared hydrogels with other typically reported hydrogels, such as PVA/GO, 28 PLA/Gr, 29 NCF-CB/PVA, 30 PEDOT-PSS/ PVA, 31 PVA/CS/GO/NiO, 32 PVA/WPPy/GQDs, 33 PVA/ PSSA/TiO 2 , 34 PPy/PVA-CNP, 35 and PVA/RGO/AC. 36 Accordingly, our PPPg composite is comparative and even superior to previous works.…”

Hydro/Organo/Ionogels: “Controllable” Electromagnetic Wave Absorbers

“…Both electron transport and ion migration can form currents and cause EMW losses under alternating EM fields. [36][37][38] In the case of gels, the dielectric inert polymer networks contribute neither polarization nor conduction losses, and there is an extreme lack of free electrons in the internal liquid. Electronic conduction losses are ignored as a matter of course.…”