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

This study presents a comparative spectroscopic investigation of natural Cr³⁺-bearing ruby and multiphase Al₂O₃-based ceramics derived from industrial waste. The natural corundum shows characteristic Cr³⁺ crystal-field absorption bands at ~405 and ~550 nm and sharp R-line emission near 693 nm, confirming a structurally ordered α-Al₂O₃ lattice. In contrast, the waste-derived ceramics exhibit charge-transfer-dominated absorption associated mainly with V⁵⁺ and Fe³⁺ under oxidizing firing conditions. Strong UV absorption (220–300 nm) and the absence of vanadium crystal-field transitions indicate predominant V⁵⁺ stabilization, consistent with chemical and phase analysis. The ceramics display high lightness (L* ≈ 93) and a yellow hue (b* = 10–23) governed by ligand-to-metal charge-transfer processes. The results demonstrate the effectiveness of combined UV–Vis and Raman spectroscopy for distinguishing crystal-field and charge-transfer mechanisms and for resolving dopant-related colour formation in alumina systems.

This study investigates the chemical, mineralogical, and functional characteristics of fermented grape pomace ash generated after brandy production and subsequent combustion. Semi-quantitative WDXRF analysis revealed a Ca–K–P-dominated composition with high alkalinity, significant phosphorus content, and notable copper concentration. The water-soluble fraction of the ash was determined to be 17.1 wt.%, indicating a moderate content of mobile inorganic salts that may influence leaching behaviour and environmental compatibility. XRD and vibrational spectroscopy confirmed the presence of lime, calcite, silicates, sulphates, and calcium phosphate phases, including hydroxyapatite, together with a significant amorphous fraction and residual carbon. UV–Vis analysis indicated partial reduction of copper species to metallic nanoparticles, suggesting heterogeneous redox conditions during thermal treatment. The combined composition confers potential functionality in soil amendment, mineral carbonation for CO₂ sequestration, and incorporation into cementitious or alkali-activated systems, although soluble salts and copper mobility represent critical constraints, requiring application-specific environmental and performance assessment.