## 3 Results and Discussion
### Materials Characterization
29-1360 or RRUFF ID R130225.9), was not detected in the obtained diffraction patterns (20 = 25.35, 25.69, 30.81, 32.81, 36.24, 37.28, 37.96, 38.36, 38.6, 39.25, 39.94, 40.16, 42.33, 46.07, 46.39, 48.03, 49.16, 49.68, 52.06, 54.22, 54.4, and 55.24). Figure 4: SEM image of particle dispersion for (**a**) System I (\(d_{\mathrm{av}}\) = 46 nm, 1 wt. % TiO\({}_{2}\)); and (**b**) System II (\(d_{\mathrm{av}}\) = 100 nm, 1 wt. % TiO\({}_{2}\)). For the cured ED-20, the appearance of the additional lane in the amorphous halo region was observed at 20 = 22 deg., which corresponds to the ordered epoxy polymer structure, probably formed as result of the free volume relaxation by the diffusion mechanism [60, 61]. The XRD patterns of the studied composite Systems showed the diffraction reflexes of the cured ED-20 (20 = 16.3, 21.9 deg.) and TiO\({}_{2}\). This observation suggested that the presence of TiO\({}_{2}\) did not affect the epoxy's supramolecular structure formed during curing. The calculated average crystallite sizes from the Scherrer equation are 36 nm and 95 nm for the nanoparticles in Systems I and II, respectively. It should be noted that these values are close to the results obtained by SEM; therefore, the distortions of the crystal lattices due to the microstrains around the defects do not play a significant role in the broadening of the reflexes in the powder XRD patterns. The TiO\({}_{2}\) nanopowders and synthesized TiO\({}_{2}\)/EP nanocomposites were further characterized by Fourier transform infrared (FTIR) spectroscopy (Figure 6). In the FTIR spectra of the TiO\({}_{2}\) nanopowders, a broad peak of Ti-O stretching vibrations is observed in the range of 900-400 cm\({}^{-1}\) with absorption maxima at 605 and 670 cm\({}^{-1}\), which is typical for TiO\({}_{2}\) polymorphs [62]. Actually, this peak is a superposition of the bands related to the antisymmetric stretching vibrations of the O-Ti-O (above 600 cm\({}^{-1}\)) and Ti-O-Ti (below 500 cm\({}^{-1}\)) fragments [63]. The bands at 1633 cm\({}^{-1}\) and in the range of 3100-3650 cm\({}^{-1}\) correspond to the bending and stretching vibrations of adsorbed water molecules [64, 65]. In the range of 900-3100 cm\({}^{-1}\) corresponding to the vibrations of organic groups, the spectra of the cured ED-20 and composites are very similar and show a complex pattern. The FTIR spectra of the synthesized TiO\({}_{2}\)/EP nanocomposites differ from that of the cured ED-20 by an additional absorption in the range of 900-400 cm\({}^{-1}\) corresponding to the Ti-O bonds in TiO\({}_{2}\). According to [53, 66], the wavenumber of the band of C-O stretching vibrations of the Ti-O-C fragment in the composites, with the O atom belonging to the organic matter, is about 1040 cm\({}^{-1}\). Figure 6: ATR-FTIR spectra: 1—TiO\({}_{2}\) (\(d_{\text{av}}\) = 46 nm); 2—TiO\({}_{2}\) (\(d_{\text{av}}\) = 100 nm); 3—cured epoxy; 4—TiO\({}_{2}\)/EP of System I (4 wt. % TiO\({}_{2}\)); and 5—TiO\({}_{2}\)/EP of System II (4 wt. % TiO\({}_{2}\)). AR denotes aromatic groups, and =C–N denotes conjugated C–N bonds. To study the fine changes caused by the introduction of TiO\({}_{2}\) into the matrix structure, the difference spectra obtained by subtracting the spectrum of the composite with 4 wt. % nanoparticles from the spectrum of the cured resin were constructed (Figure 7). The intensity of the difference spectrum is increased for clarity. The most prominent was a shift in the peak position of the ordinary C-N bonds and conjugated C-N from 1031 to 1011 cm\({}^{-1}\) and from 1294 to 1274 cm\({}^{-1}\), respectively. Moreover, the band of =C-O-C- at 1231 cm\({}^{-1}\) shifts to 1211 cm\({}^{-1}\). All of these groups are polar and the shift of a small portion of these peaks by \(\sim\)20 cm\({}^{-1}\) could be caused by the dipole-dipole interactions at the surface of the TiO\({}_{2}\) nanoparticles as well as a change in the conformation organic groups.