2.5. Characterization of MAX/MXene Phases

The surface morphology and the shape of particles of the Ti₃AlC₂ MAX phase and Ti₃C₂ MXene 2D sheets were investigated with the use of an SEM, LEO 1530 (Zeiss, Maple Grove, MN, USA) scanning electron microscope. The phase composition of the obtained MAX phase was investigated with the use of X-ray diffraction (XRD, D8 ADVANCE, Bruker, Billerica, MA, USA), using CuKα radiation at a wavelength λ = 0.154056 nm. The parameters of this test were as follows: voltage: 40 kV, current: 40 mA, angular range: 10–90°, 0.05° step. The optical absorption spectra of the 2D sheets of Ti₃C₂T_x unmodified and modified with 3% wt. Y₂O₃ were analyzed using a UV-Vis spectrometer (Evolution 220, Thermo Scientific, Waltham, MA, USA) in distilled water and in isopropanol. Spectra were recorded in the range of 220–1100 nm. The measurement parameters were: scanning speed of 200 nm min⁻¹, integration time of 0.30 s, resolution of 1.00 nm. Fourier transform infrared spectroscopy (FTIR) measurements were performed using FT-IR Nicolet iS5 from Thermo Electron, Waltham, MA, USA), equipped with a diffuse reflectance infrared Fourier transform (DRIFT) accessory. For the DRIFT measurements, the samples were mixed with dried KBr (Fluka, assay ≥ 99.5%) at a concentration of 2.5% wt. The resolution of the FTIR analyzer on which the measurements were performed was 2 cm⁻¹. The spectra were recorded in the range of 4000–400 cm⁻¹. Each spectrum was reported in an average of 30 scans. The zeta potential and measurements were performed using a NANO ZS ZEN3500 analyzer (Malvern Instruments, Malvern, UK) equipped with a back-scattered light detector operating at a 173° angle. The studies were carried out at 25 °C in distilled water and in isopropanol. The concentration of the studied samples was 5 × 10⁻⁴ g/cm³, and each sample was homogenized for 30 sec using mild sonication (Emmi H60, Emag, Salah, Germany). The zeta potential measurements were repeated 20 times. The results were expressed as the mean value of zeta potential ± SD.