A novel method to obtain Al₂O₃–ZrO₂ nanocomposites is presented. It consists of the co-precipitation step of boehmite (AlO(OH)) and ZrO₂, followed by microwave hydrothermal treatment at 270 °C and 60 MPa, and by calcination at 600 °C. Using this method, we obtained two nanocomposites: Al₂O₃–20 wt % ZrO₂ and Al₂O₃–40 wt % ZrO₂. Nanocomposites were characterized by Fourier transformed infrared spectroscopy, Raman spectroscopy, X-ray diffraction, and transmission electron microscopy. Sintering behavior and thermal expansion coefficients were investigated during dilatometric tests. The sintering temperatures of the nanocomposites were 1209 °C and 1231 °C, respectively—approximately 100 °C lower than reported for such composites. We attribute the decrease of the sintering temperature to the specific nanostructure obtained using microwave hydrothermal treatment instead of conventional calcination. Microwave hydrothermal treatment resulted in a fine distribution of intermixed highly crystalline nanoparticles of boehmite and zirconia. Such intermixing prevented particle growth, which is a factor reducing sintering temperature. Further, due to reduced grain growth, stability of the θ-Al₂O₃ phase was extended up to 1200 °C, which enhances the sintering process as well. For the Al₂O₃–20 wt % ZrO₂ composition, we observed stability of the zirconia tetragonal phase up to 1400 °C. We associate this stability with the mutual separation of zirconia nanoparticles in the alumina matrix.

The influence of the V₂O₅nanostructure size on the aggregation process and their electrochemical properties.

This work presents the result of structure investigations of V₂O₅ nanorods grown from thin films and powders prepared by sol‐gel method. To examine the best temperature of nanorods crystallization, thin films deposited by spin‐coating method on quartz glass or silicon substrates and bulk xerogel powders were annealed at various temperatures ranging from 100°C to 600°C. The structure of the samples was characterized by X‐ray diffraction method (XRD), scanning electron microscope (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and mass spectroscopy (MS). The rod‐like structure of V₂O₅ was obtained at 600°C on both quartz glass and silicon substrates and also from the bulk xerogel. The growth process and the effect of annealing treatment on the nanostructure are briefly discussed.

Photocatalysis is regarded as a promising tool for wastewater remediation. In recent years, many studies have focused on investigating novel photocatalysts driven by visible light. In this study, K₂V₆O₁₆·nH₂O nanobelts and KV₃O₈ microplatelets were synthesized and investigated as photocatalysts. Samples were obtained via the facile method based on liquid-phase exfoliation with ion exchange. By changing the synthesis temperature (20-80 °C), different compositions, morphologies, and V⁴⁺/V⁵⁺ ratios were obtained and investigated as photocatalysts for organic dye degradation. Potassium vanadates' structural, morphological, and optical properties were characterized using X-ray diffraction(XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Physical Property Measurement System (PPMS), thermogravimetric analysis (TGA) with mass spectrometry (MS), N₂ adsorption, scanning electron microscopy (SEM), photoluminescence (PL), and UV-vis diffuse reflectance spectroscopy (DRS). Synthesized K₂V₆O₁₆·nH₂O and KV₃O₈ showed an efficient absorption in the visible wavelength region with a narrow band gap energy of 1.80 and 1.91 eV, respectively. Their photocatalytic activity was evaluated by the degradation of methylene blue (MB) under simulated solar light illumination. The KV₃O₈ microplatelets exhibited the greatest photocatalytic activity, resulting in more than 90% degradation of the dye within the first 30 min. It is suggested that the observed excellent photocatalytic performance is attributed to the high content of V⁴⁺ species. Furthermore, the influence of active species was investigated, and the mechanism responsible for the photodegradation of the MB dye was discussed for the first time for potassium vanadates.