## 2 Materials and Methods
### Characterization  
Elemental analysis of C, H, and N was performed using a Vario EL cube elemental gas analyzer manufactured by Elementar GmbH (Langenselbold, Germany, 2016), using a combustion and reduction tube, and katharometer (thermal conductivity detector) as a detector. The gas separation takes place according to the classical \"purge and trap\" technology on three adsorption columns. To determine the Ti content in the original nanopowders, an atomic absorption spectrophotometer AAS-3 manufactured by VEB Feinmesszeugfabrik (Oberammergau, Germany, 1988) was used.  
The morphologic characteristics of the as-synthesized nanoparticles were studied using microphotographs obtained on a JEOL JEM-1400 PLUS universal transmission electron microscope manufactured by JEOL (Akishima, Japan) at an accelerating voltage of 120 kV. Histograms of particle size distribution were calculated based on the results of image analysis.  
The microstructure of the synthesized nanocomposites was studied using a Zeiss LEO SUPRA 25 by [PERSON] (Oberkochen, Germany, 2008) scanning autoemission microscope with application of carbon sputtering.  
X-ray diffraction (XRD) phase analysis was performed using an Aeris X-ray diffractometer manufactured by Malvern PANalytical B.V. (Worcestershire, UK) equipped with a ceramic X-ray tube with a copper anode manufactured by PANalytical and a fast linear detector PIXcel1D. The average crystallite size \(d_{\mathrm{av}}\) was calculated from the line broadening in the spectrum using the Scherrer equation (Equation (1)):  
\[d=\mathrm{k}\lambda/(\beta\mathrm{cos}\theta), \tag{1}\]  
where k is the dimensionless coefficient of particle shape (Scherrer constant), which is equal to 0.94; \(\beta\) is the reflex width at half the maximum intensity; \(\lambda\) is the wavelength of X-rays; and \(\theta\) is the diffraction angle.  
A Bruker ALPHA FT-IR spectrometer by Bruker (Ettlingen, Germany) was used to obtain infrared spectra of the obtained nanocomposites by the method of attenuated total reflection (ATR) in the range of 360 to 4000 cm\({}^{-1}\). Tablets of TiO\({}_{2}\)/KBr were created to obtain the spectra of TiO\({}_{2}\) powders. OPUS v6.5 and OriginPro 2018 v9.5.1 software were used to control the equipment and process the data, respectively. Changes in the spectra were evaluated by the difference between the spectra of the initial cured epoxy resin and the obtained TiO\({}_{2}\)/EP nanocomposites.  
Mechanical tensile tests were performed on a Zwick/Roel Z010 TC-FR010 TH (Ulm, Germany, 2002) universal testing machine for tensile, compression, bending, and fracture toughness of materials. Tests were carried out according to ASTM D882-10 [49] with loading speed of 1 mm/min.  
Charpy impact toughness was determined on the Charpy impact testing machine by Zwick according to ISO 179-1 [50] on samples in the form of sticks with size of 4 \(\times\) 6 \(\times\) 50 mm.  
Thermogravimetric analysis was performed using an analyzer for thermogravimetric and differential thermal analysis TGA/SDTA851e from Metller-Toledo GmbH (Nanikon, Switzerland) in a range of 20 to 450 \({}^{\circ}\)C at a temperature rise rate of 10 deg/min. A differential scanning calorimeter DSC822e/200 from Metller-Toledo GmbH (Nanikon, Switzerland) was used to determine the glass transition temperature. The STAR software package v15.00a was used to control the instruments and process the results.