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In this study, the effects of the phase transition on the optical transmittance of the nematic liquid crystal C21H27NO2S, 4′-isothiocyanatophenyl-4-pentylbicyclo[2,2,2]octane-1-carboxylate are investigated in terms of temperature variation and rotational angle of the polarizer through electro-optical methods under AC / DC electric fields. It is observed that the domain structure of the material is affected considerably by the applied electric field as the temperature changes. Under applied electric fields, the crystal-nematic (CN) phase-transition point changes and the behaviour of the liquid crystal in the phase-transition region shows some differences. The intensity of the light passing through the system under a DC electric field increases as the electric field rises. Nevertheless, the intensity of the transmitted light under an AC electric field increases at the beginning and then decreases as the electric field rises to a temperature of more than 355 K. These results can be explained through the formation of a domain structure during the phase-transition process and the light scattering caused by these structures.

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In this study, composites of wollastonite-colemanite were produced by using mixed oxide technique. The wollastonite-colemanite compositions were formed with various proportions for the structural analysis. The results of wollastonite-colemanite structural analysis indicated that second phase did not form in wollastonite and colemanite. The single phases wollastanite-colemanite compounds were measured after sintering between 900-1100°C for X-ray diffraction (XRD). Addionality, the wollastonite/polyaniline/colemanite composites were produced by hot pressing using the compositions of wollastonite-colemanite in different proportions and aniline. The weight ratios of (wollastonite-colemanite) and aniline were 1:1 respectively and epoxy resin was used to produce microwave shielding effectiveness composites. The microwave shielding performances of wollastonite/polyaniline/colemanite composites were investigated by shielding effect in 0 -8 GHz, using two-port vector network analyzer (VNA). A minimum of -41.65 dB shielding effectiveness performance was obtained in 6.26 GHz at the thickness of 1.5 mm. According to the parameters determined in terms of properties, the wollastonite-colemanite compounds were produced as composite with a PANI base and their features were characterized for shielding effect. This microwave shielding performance can be modulated simply by controlling the content of polyaniline and content of wollastonite-colemanite in the samples for the wider and required frequency bands.