Portugaliae
Electrochimica Acta

Electrochemical oxidation reaction of glucose in an alkaline medium was studied on carbon paste and titanium dioxide (TO2)-modified carbon paste electrodes. The effect of titanium dioxide composition on the support was studied. Electrochemical methods used in this work were Cyclic Voltammetry, Electrochemical Impedance Spectroscopy and Tafel lines. It was confirmed that the addition of a TiO2 composite catalyst significantly modified electro-oxidation of glucose. Keywords: carbon paste electrode; Cyclic Voltammetry; titanium dioxide; Electrochemical Spectroscopy Impedance; glucose oxidation.

Abstract Charge-transfer (CT) complex exhibits unique redox properties that make it a promising candidate for advanced energy storage and conversion systems. This study presents a comprehensive electrochemical investigation of CT complex, focusing on its charge-storage behavior and kinetic characteristics. Quantitative analysis revealed high specific capacitance (Csp) values derived from cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) measurements, ranging from 494 to 114 F/g (CV) and 490 to 117 F/g (GCD) over scan rate range from 0.025 to 0.40 V/s. This demonstrates good rate capability and strong agreement between both electrochemical methods. Tafel analysis further provided insights into onset potential and exchange current density, confirming efficient electron transfer. This novel approach converts CV data into galvanostatic charge-discharge profiles, enabling accurate Csp evaluation of CT complex from a single electrochemical dataset. Integration of CV-derived GCD and Tafel plots provides a good methodological framework for correlating pseudocapacitive behavior with CT kinetics. These findings highlight the potential of CT complex as an efficient, low-cost and tunable material for supercapacitors and electrocatalytic energy storage devices. Keywords: Charge-transfer complex; Pseudocapacitance; Tafel plot.

Graphite-epoxy cylindrical shell panels find widespread application in engineering structures. Various functional requirements necessitate use of cutouts and stiffeners in shell panels. To evade resonating damage, natural frequency of such structures should be optimized. The present study obtained natural frequency of cylindrical shell panels with cutout using finite element analysis, and optimized it based on Taguchi analysis for different edge constraints. Numerical study was performed following L27 Taguchi orthogonal design, where fiber direction, thickness ratio, degree of orthotropy and location of cutout were considered as design variables. Shallowness of the shell panel expressed in terms of width/thickness ratio influenced the fundamental frequency most followed by degree of orthotropy. Keywords: cutout; cylindrical shell panel; free vibration; laminated composite; stiffener; Taguchi optimization.

Abstract The preservation of insulating oil’s system integrity is a key strategy for maintenance planners to curtail the incidence and progression of internal faults. This imperative highlights the essential role of accurate diagnostic methodologies in transformer oil (electrical insulating oil) condition monitoring and analysis. This study aims to evaluate long-term operational aging effects on molecular and dielectric properties of insulating oils used in power transformers within Syrian electricity grid, employing visible spectroscopy and Fourier Transform Infrared (FT-IR) spectroscopy. A comparative analytical approach was adopted, focusing on spectroscopic changes in conjunction with electrical property measurements. Four oil samples of the same origin were analyzed: fresh unused oil, oil used for three years, oil used for ten years - taken from the bottom- and oil used for ten years -taken from the top. Additionally, relative permittivity (dielectric constant) of all samples was measured at multiple frequencies (1, 2, 3, 10, 100 and 200 kHz). Results identified a two-stage aging process: an initial decrease in IR transmittance (first 3 years), followed by a significant increase after 10 years, particularly in the bottom sample, indicating accumulated polar oxidation products. Dielectric properties varied accordingly. The study confirms FT-IR as an effective tool for monitoring oil degradation. Keywords: Transformer oil; aging; FT-IR spectroscopy; dielectric constant.

Magnesium and its composites have emerged as promising lightweight materials with applications in structural, biomedical and energy storage sectors. Despite poor corrosion resistance and limited strength, operational and functional performance has been enhanced by alloying, various reinforcements and corresponding surface modifications. This study encompasses a bibliographic analysis of global research trends, also highlighting the rapid rise of magnesium-based composite research in the last ten years. Magnesium has been researched in a strongly interdisciplinary way across materials science, chemistry, physics, biomedical and energy studies with international collaboration and funding. Furthermore, the ever-growing trend for the adoption of machine learning (ML) and other modern tools reflects this material’s transformative potential in property prediction, composite design and tribological modelling. Overall, magnesium composites have reached a rapid evolving frontier, where data-driven techniques are expected to accelerate innovation for next-generation sustainable materials. In this work, the impact of different ML approaches for distinct property predictions has also been discussed. Additionally, corresponding research gaps are herein highlighted. Keywords: bibliographic analysis; machine learning; magnesium composite.