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Study on the electromagnetic shielding efficiency of functional layer with reducing iron powder mortar
Published in Domenico Lombardo, Ke Wang, Advances in Materials Science and Engineering, 2021
The shielding effect at the low frequency point is poor, which mainly has two reasons: on the one hand, the low frequency electromagnetic wave has a long wavelength, which is easy to diffraction, and the shielding defect is easy to occur at the joint of angle steel door frame and the overlap of side wall fabric; On the other hand, when the shielding efficiency of low-frequency electromagnetic wave is tested, it is easy to be affected by external power supply and filter, which causes certain test errors. The two measuring points have big shielding defects at 100MHz frequency point, which is mainly because 100MHz is close to the receiving frequency of radio stations around the test site, which is easy to be affected, which causes the test results to be relatively small. With the increase of frequency, the shielding efficiency tends to increase, which is mainly because of the short wavelength, poor diffraction ability and strong directivity of high frequency electromagnetic wave, which is easy to reflect and absorb losses at the measuring point, so as to obtain more effective shielding.
Electromagnetic interference shielding effectiveness of sol-gel coating on Cu-plated fabrics
Published in The Journal of The Textile Institute, 2021
P. V. Kandasaamy, M. Rameshkumar
One of the major factors in influencing the fabrics EMI SE is the electrical conductivity of the material. Higher electrical and magnetic conductivities help to acquire the optimum shielding effect in an extensive variety of frequencies. Generally, the three categories of electrical conductivity of the materials are the insulators, semi-conductors and conductors. ATSM D257-14 standards are referred to measure and calculate the electrical conductivity of Cu-plated and sol-gel coated fabric according to Equation 6. The electrical resistivity of Cu-plated fabric is depending on the copper sulfate concentration purely as it is assured from Figure 7. Copper sulfate concentration is directly proportional to the electrical resistivity. Since the nonstop connectivity between the small-sized copper particles creates the formation of percolated network which produces lower concentration (5–20 g/L) of copper sulfate with more conductive fabrics. Henceforth, the nucleation of copper particles is disrupted by the action of agitation or ultrasonication which leads to a good topic for further research in order to acquire more percolated network at higher copper sulfate concentration. Additionally, due to the diverge denser film formation over the coating with sol-gel with respect to the type of precursors utilized in this work, the electrical resistivity varies with respect to the sol-gel coating. Amid the precursors, highest electrical resistivity is shown by the TPS, as it contains the benzene ring which forms the rigid surface because of the formation of thicker film on the fabric surface plated with copper. Lowest electrical resistivity (e.g. VTMS, TMOS, and TEOS) gives the precursors to have the flexible network structure as confirmed from the results.