Highly efficient shielding materials, transparent in the visible and IR ranges are becoming important in practice. This stimulates the development of cheap methods for creating transparent conductors with low sheet resistance and high optical transparency. This work presents a complex approach based on preliminary modeling of the shielding characteristics of two-layer sandwich structures based on irregular aluminum mesh (IAM) formed by the cracked template method. Experimentally measured spectral dependences of the transmission coefficient of single-layer IAM are used as a reference point for modeling. According to the simulation results, two types of sandwich structures were designed using IAM, with varying filling factors and a fixed PMMA layer thickness of 4 mm. The experimentally measured shielding characteristics of the sandwich structures in the range of 0.01–7 GHz are in good agreement with the calculated data. The obtained structures demonstrate a shielding efficiency of 55.96 dB and 65.55 dB at a frequency of 3.5 GHz (the average range of 5G communications). At the same time, their optical transparency at a wavelength of 550 nm are 84.07% and 75.78%, respectively. Our sandwich structures show electromagnetic shielding performance and uniform diffraction pattern. It gives them an advantage over structures based on regular meshes. The obtained results highlight the prospect of the proposed comprehensive approach for obtaining highly efficient, low-cost optically transparent shielding structures. Such materials are needed for modern wireless communication systems and metrology applications.

Subject of study. This study investigated the spectral properties of silver irregular microgrids (AgIMGs) and sandwich structures in the visible and radio frequency (RF) ranges. AgIMGs were fabricated using a self-assembled template formed by cracking a thin film of egg white. Aim of study. The aim of this study was to develop a method for producing AgIMGs with a thickness exceeding 500 nm, low surface resistance, and high optical transmittance in the visible range. Additionally, sandwich structures based on such microgrids that demonstrate a shielding effectiveness (SE) of at least 60 dB in the RF range were fabricated. Main results. A method for locally peeling off the perimeter (CPP) of self-organized template cells has been developed. It allows for an increase in the thickness of the deposited silver to more than 500 nm. Increasing the thickness of the deposited metal is a critical factor for improving the optoelectric characteristics of AgIMG. Two-layer sandwich structures were obtained based on our AgIMG. Sandwich structures consisting of irregular silver microgrids based on a template with a partially peeled off perimeter of the cells show an SE of 71.01 dB in the range of 1–7 GHz with a transmission value of 80.02% in the visible range. Practical significance. Sandwich structures based on AgIMGs formed on a template with a partially detached cell perimeter are a promising solution for shielding optically transparent objects and information display devices. The sandwich structures developed in this study outperform existing optically transparent RF-shielding screens in terms of the combined parameters of SE, optical transmittance, and production cost.

In this study, we demonstrated chloroprene rubber (CR)-based composites with the addition of synthesized alumina nanofibers (AONF) with a high aspect ratio (>1000). AONF were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). AONF were introduced by pre-dispersion. The resulting chloroprene rubber/aluminum oxide nanofiber (CR/AONF) composites were subjected to tensile and shear adhesive bonding tests. The tensile test results for the CR/AONF composites are 81% greater than those of the original CR composite (0.85 MPa and 1.54 MPa, respectively). Shear adhesive bonding tests were conducted for glass and steel. CR/AONF demonstrates a 213% (for steel) and 262% (for glass) increase in shear strength. The main strengthening mechanisms are reinforcement, CR adsorption on the AONF surface, and crack arrest. These results may expand our understanding of the potential of sealant strengthening using AONF.

For the first time, an environmentally friendly waste-free closed cycle for the formation of EMI shielding materials that are promising for 5G communications is considered. Based on the proposed closed technological cycle, two types of EMI shielding materials have been obtained; both materials have significant prospects for signal shielding in all ranges that are allocated in different countries for 5G communication. The first type of materials are transparent conductive meshes with a transparency of more than 80% and with a shielding efficiency of more than 40 dB in the S and L bands and about 30 dB in the K and Ka bands. The study of signal reflection characteristics in the S, L, C, K and Ka bands showed the promise of using these materials as transparent 5G signal reflectors. The reflection coefficient in all considered ranges is above 90% (-0.5 dB). The second type of shielding material are continuous silver micro caps films characterized by a shielding efficiency of 90.1 dB at a thickness of 6.2±1.2 µm. We have also shown that silver micro caps can separate into silver flakes and ribbons when sonicated. These materials can also be used to produce EMI shielding coatings and composites. A detailed analysis of the shielding properties showed that each type of materials obtained in a closed technological cycle is comparable with the best literature results and significantly wins in terms of cost.