International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

Spectroscopic ellipsometry was applied to study the optical properties of Ti–6Al–4V alloy before and after anodization in acetic acid electrolyte. The main findings can be summarized as follows: The ellipsometric spectra of the uncoated alloy were successfully modeled using a multi-Lorentz oscillator approach with MSE values of 20–26, and surface roughness ranging from 17 to 52 nm. Anodized surfaces exhibited distinct interference features, confirming the formation of a transparent oxide layer. The optical modeling revealed increased surface roughness and modified optical constants due to the formation of a TiO₂ -based film with amorphous–anatase character. The applied ellipsometric methodology proved reliable for evaluating the thickness and optical properties of anodic oxide films on titanium alloys. These results form the basis for future quantitative analysis of anodic oxide thickness and refractive index as functions of anodizing parameters, which is important for optimizing the surface properties of titanium alloys in biomedical, protective, and optical applications.

This work presents an overview of sol–gel-derived oxide materials and their relevance to optical, photonic and photovoltaic applications, followed by an experimental study of ZrO₂–Al₂O₃–Sm₂O₃ thin films deposited on glass substrates. Historical developments of the sol–gel process, beginning with early investigations on silica gels in the 19th century, are outlined together with advancements in optical glasses, anti-reflective coatings, and rare-earth-doped systems. Recent progress in functional materials—including boron-, tellurium- and rare-earth-containing glasses, luminescent oxide systems, and sol–gel-derived zirconia-based coatings—is discussed to highlight their structural, optical and radiation-shielding capabilities.
In the present study, multilayer ZrO₂–Al₂O₃–Sm₂O₃ coatings were prepared via the sol–gel method combined with dip-coating, and subsequently thermally treated at 420 °C. Optical characterization (UV–VIS–NIR) revealed changes in transmittance and reflectance linked to film composition and thickness, while X-ray diffraction confirmed their predominantly amorphous structure at the applied heat-treatment temperature. SEM and EDS analyses provided insight into surface morphology and elemental distribution within the films. The results demonstrate that increasing Al₂O₃ content influences coating porosity and thickness, while Sm₂O₃ contributes luminescent functionality and potential reduction of optical reflection in key solar spectral regions. These findings indicate that ZrO₂–Al₂O₃–Sm₂O₃ thin films are promising candidates for protective and functional coatings in photovoltaic applications, where enhanced light harvesting and improved surface properties are essential.

Corrosion remains a major limitation for the long-term use of aluminum alloys such as A356, particularly in chloride-rich environments. Although traditional chromate coatings provide effective protection, their toxicity necessitates environmentally friendly alternatives. In this study, a composite ZrO2–Al2O3–Sm2O3 coating was synthesized via a sol-gel method and deposited on A356 alloy using dip-coating. The precursor system was formulated from zirconyl chloride, samarium oxide, and aluminum oxide, stabilized with acetylacetone and acetic acid at pH 0.5 to ensure homogeneous film formation. The coated samples were thermally treated at 400 °C to obtain dense oxide layers. Corrosion resistance was assessed under neutral salt spray conditions (5% NaCl, 35 °C, 648 h) according to BDS EN ISO 9227:2023. Comparison between uncoated A356, binary Al–Zr (ADZ), and ternary Sm–Al–Zr (SADZ) coatings demonstrated a clear performance improvement with increasing film complexity. While ADZ coatings reduced surface damage relative to the bare alloy, the SADZ films exhibited the lowest amount of corrosion products, minimal surface darkening, and significantly reduced pitting. The enhanced performance is attributed to the synergistic effect of the three oxides: ZrO₂ provides chemical stability, Al2O3 increases layer density, and Sm₂O₃ contributes active corrosion inhibition.
Overall, the ZrO2–Al2O3–Sm2O3 composite film offers a promising non-chromate protective system for improving the long-term corrosion resistance of A356 aluminum alloy.

Obtained experimental self-cleaning coatings (based on compositions with the participation of Sm2O3), applied by the sol-gel method on glass slides. This study attempts to improve the overall efficiency of a photovoltaic solar panel by using a Sm2O3 doped ZrO2 (SDZ)-based coating. The optical characterization and phase composition of the obtained experimental samples were investigated using UVVIS- NIR, XRD and XRF methods. The coatings are nanocrystalline according to XRD and XRF analyzes and show transmittance close to that of pure glass when tested with a UV–VIS–NIR spectrophotometer The experimental results represent a prerequisite for the development of a series of additional compositions and a detailed technological regime for obtaining various modifications of resistant, long-lasting selfcleaning coatings, potentially applicable to photovoltaic panels.

Thin coatings of aluminum oxide (Al2O3), zirconium oxide (ZrO2) and samarium oxide (Sm2O3) on aluminum alloy Al7SiMg (A356) were prepared by sol-gel method and immersion technique. The materials were characterized in detail by X-ray diffraction. The luminescent properties at room temperature were also investigated. Luminescence analysis showed that the Al2O3 coating containing ZrO2 exhibits broad excitation and emission bands, peaking at 328 nm and 392 nm, respectively. Photoluminescence data for the Al2O3 coating containing ZrO2 and Sm2O3 indicated effective excitation at 404 nm and strong broadband emission, which is due to the co-emission of ZrO2 and Sm2O3. Chromaticity coordinate analysis revealed that Al2O3 coating containing ZrO2 and Al2O3 coating containing ZrO2 and Sm₂ O₃ emit in the blue-purple and pale pink regions, respectively.The chromaticity coordinates, color purity and CIE (Commission Internationale de L’Eclairage) color-correlated temperature were determined.

Chromium coatings were obtained from spent (waste) chromium electrolyte with the addition of nanosized aluminum oxide. The recovery of the waste chromium electrolyte is carried out by the activation of the chromium ions using the addition of Al2O3 nanoparticles. Electrochemically thin chromium films were deposited directly on S235 steel. The recovered chromium electrolyte has a concentration of nanoparticles of Al2O3 up to 10 g/l, which particles act as intensifiers of the electrochemical process. Analysis was performed with a “Polyvar Met” metallographic microscope and a Bruker D8 Advance powder X-ray diffractometer (XRD). The microstructure of the layer and the matrix were examined and the main phases were determined. SEM-EDS analysis of the chromium layer and the steel matrix was performed. The thickness of the obtained chrome coating with aluminum oxide nanoparticles was determined, which varies between 5 – 10μm.