Optical absorbance measurements have been performed on the epoxy resin and the composites prepared by its modification with two different oxime derivatives (benzaldoxime and 2-furaldoxime) in the wavelength interval of 190-680 nm by unpolarized light. Using the experimental absorbance data, dielectric constant and refractive index dispersion have been determined by means of standard oscillator fit procedure. Moreover, based on the dispersion analysis, direct and indirect band gap energies of the samples have been calculated. It is found that direct band energy for epoxy is nearly 3.49 eV, while its value for the oxime derivatives has been increased up to the 4.15 eV. Another important result to be pointed out is that the absorbance for the 2-furaldoxime doped resin has been greatly increased in a respectively, narrow interval ($ 30 nm wide) in the UV region, while in the case for the benzaldoxime doped sample, a decreasing has been observed in the absorbance at the same region.
The effects of the homogenization process on the structures and dielectric properties of pure and Nb-doped BaTiO ceramics have been investigated using an ultrasonic homogenization and conventional mechanical methods. The reagents were homogenized using an ultrasonic processor with high-intensity ultrasonic waves and using a compact mixer-shaker. The components and crystal types of the powders were determined by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses. The complex permittivity (ε, ε″) and AC conductivity (σ') of the samples were analyzed in a wide frequency range of 20Hz to 2MHz at room temperature. The structures and dielectric properties of pure and Nb-doped BaTiO ceramics strongly depend on the homogenization process in a solid-state reaction method. Using an ultrasonic processor with high-intensity ultrasonic waves based on acoustic cavitation phenomena can make a significant improvement in producing high-purity BaTiO ceramics without carbonate impurities with a small dielectric loss.
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