Peymanfar Reza, Selseleh-Zakerin Elnaz, Ahmadi Ali, Saeidi Ardeshir, Tavassoli Seyed Hassan
Laser and Plasma Research Institute, Shahid Beheshti University, G. C., Evin, 19839, Tehran, Iran.
Department of Chemical Engineering, Energy Institute of Higher Education, Saveh, Iran.
Sci Rep. 2021 Aug 9;11(1):16161. doi: 10.1038/s41598-021-95683-3.
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-CN) 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-CN, 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 (SE) > 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.
在本研究中，制备了一种自愈合水凝胶，它对可见光（Vis）透明，同时吸收紫外线（UV）、红外线（IR）和微波。通过在红外源下使用红外温度计监测温度来探索水凝胶的光热特性。该水凝胶以十水硼酸钠（硼砂）和聚乙烯醇（PVA）为原料，基于简便的热路线合成。更重要的是，氧化石墨烯（GO）、类石墨氮化碳（g-CN）纳米结构以及碳微球（CMS）作为客体被应用，以进一步剖析它们对微波和光学特性的影响。使用场发射扫描电子显微镜（FE-SEM）评估填料的形态。傅里叶变换红外光谱（FTIR）证明水凝胶的化学官能团已形成，漫反射光谱（DRS）结果证实该水凝胶吸收紫外线，同时在可见光下透明。所获得的结果表明，由于其具有有利于能量效率和收集的官能团，该水凝胶可作为一种重要的红外吸收剂。有趣的是，所获得的结果证明自愈合水凝胶具有适当的自愈合效率和自愈合时间。最终，研究了水凝胶、水凝胶/GO、g-CN或CMS的微波吸收特性和屏蔽效率，证明了其显著的微波特性，这源于所建立的离子导电网络和偶极极化。该水凝胶厚度为0.65毫米时有效带宽高达3.5吉赫兹，厚度为4.55毫米时在14.50吉赫兹处最大反射损耗为75.10分贝。特别地，该水凝胶厚度为10.00毫米时，在1.19至18吉赫兹范围内总屏蔽效率（SE）>10分贝，在4.37至18吉赫兹范围内>20分贝。这些结果为通过实际方法提高屏蔽和能量效率开辟了新途径。
