Electromagnetic Interference Shielding Effectiveness Performances of Screen Printing Ink and Expanded Graphite Based Composite at X and Ku Bands

In this study, electromagnetic shielding effectiveness and microwave properties (permittivity and permeability) of the expanded graphite (eGR) embedded in screen printing ink (SPI) were investigated. The experimentally measured scattering parameters were utilized within the Nicolson-Ross-Weir (NRW) algorithm to obtain the intrinsic properties at microwave frequencies. Then these parameters were fed into CST Microwave Studio to check the homogeneity behavior of the proposed sample. Initially, a composite containing 7.9 wt% eGR was chosen and all the measurements in experimental setup (solely in waveguide environment) and CST simulations (waveguide and free-space) were performed for the proposed material. About 10 dB/mm shielding efficiency values were satisfied at X and Ku bands (8-18.4 GHz) and homogenous distribution was observed. Afterwards, a superior composite containing higher eGR concentration was searched with a trade-off the thickness and the concentration/cost. At least 57 dB and at most 77 dB shielding effectiveness values were measured for a 2 mm thickness sample having 16 wt% eGR, which results in more than 25 dB/mm shielding effectiveness at X and Ku bands.