Results from the analysis of the variation of structural defects, such as oxygen vacancies indicate that by adjusting the thickness of the WO₃ films, fabricated by DC reactive sputtering, it is possible to modulate the oxygen vacancies concentration. This has a tremendous influence on the applications of these semiconductor materials. The thicknesses analyzed here are 42, 66, and 131 nm. After the annealing process at 500 °C, films were directly transformed to a stable γ-monoclinic crystal structure with P2₁/n space group, with a preferential orientation in the (200) plane. Atomic force microscopy exhibits nanometer range particle size with the highest roughness and higher surface area for the thinner film. FTIR analysis shows the presence of characteristic bands of the double bond stretching vibrational modes (W=O) and stretching vibrations of the γ(W-O-W) bonds corresponding to the monoclinic WO₃. Raman bands located at 345, and 435 cm⁻¹ are ascribed to the presence of W⁵⁺ species that induces the formation of oxygen vacancies VO. The thinner film shows a decrease in the optical indirect band gap attributed to the formation of oxygen vacancies in combination with W⁵⁺ species that induce the formation of energy states within the forbidden band gap range.

The current paper addresses the lack of explicit analytical solutions for stress evaluations in variable-thickness flywheels by proposing an approximate formulation for conical profiles, where thickness varies linearly along the radius. The main objective was to develop a compact and practical expression to estimate radial and tangential stresses without relying on finite element analysis. Starting from a stress function, the model was simplified under the assumption of a small-thickness gradient, allowing the derivation of a closed-form solution. The resulting expression explicitly relates stresses to geometric and material parameters. To validate the approximation, stress distributions were computed for various outer-to-inner thickness ratios and compared with results obtained through FEA. The comparison, evaluated using the coefficient of determination, mean absolute percentage error, root mean squared error, normalized root mean squared error, and stress ratios, demonstrated strong agreement, especially for moderate-thickness ratios ($1\leqq t_o/t_i\leqq 4.5$). The method was more accurate for radial stress than tangential stress, particularly at higher gradients. The results confirmed that the proposed analytical approach provides a reliable and efficient alternative to numerical methods in the design and optimization of conical flywheels, offering practical value for early-stage engineering analysis and reducing reliance on time-intensive simulations.

This study explores the crystal structure, microstructure and magnetic phase evolution of the AlCoCrFeNi high-entropy alloy (HEA), highlighting its potential for applications requiring tailored magnetic properties across diverse temperatures. Electron microscopy and X-ray diffraction revealed that the as-cast alloy’s microstructure comprises equiaxed grains with branching dendrites, showing compositional variations between interdendritic regions enriched in Al and Ni. Temperature-induced phase transformations were observed above room temperature, transitioning from body centered cubic (BCC) phases (A2 and B2) to a predominant FCC phase at higher temperatures, followed by recrystallization of the A2 phase upon cooling. Magnetization measurements showed a drop near 380 K, suggesting the Curie temperature of BCC phases, a peak at 830 K attributed to optimal magnetic alignment in the FCC phase, and a sharp decline at 950 K marking the transition to a paramagnetic state. Magnetic moment calculations provided insights into magnetic alignment dynamics, while low-temperature analysis highlighted the alloy’s magnetically soft nature, dominated by ferromagnetic contributions from the A2 phase. These findings underscore the strong interdependence of microstructural features and magnetic behavior, offering a foundation for optimizing HEAs for temperature-sensitive scientific and industrial applications.

In the current work, the microstructural evolution and CO₂ sensing performance of tungsten trioxide (WO₃) thin films synthesized by reactive DC magnetron sputtering are investigated. Three specific thicknesses of 42, 66, and 131 nm were obtained and annealed at 500 °C, resulting in a stable monoclinic P2₁/n phase with a strong (200) preferred orientation. Gas sensing tests toward 10,000 ppm of CO₂ revealed that the 42 nm film achieves the highest sensitivity (92%) at an optimal operating temperature of 300 °C. Rietveld refinement and texture analysis (texture index, J) demonstrate that the superior performance of the thinnest film is driven by a synergy between its high surface porosity, a grain size comparable to the Debye length, and a high density of active sites on the (200) plane. While all films exhibit n-type semiconductor behavior, increasing thickness leads to microstructural densification and reduced texture, which hinders gas diffusion and operational stability. These findings establish thickness control as a critical parameter for engineering high-performance WO₃-based CO₂ sensors.