ICMCTF 2026 Session TS2-ThP: Coatings and Surfaces for Renewable Energy Technology Poster Session

Transition-metal-oxide functional coatings have emerged as promising candidates for next-generation electrochemical energy storage systems due to their high theoretical capacitance, chemical stability, and tunable ion-transport pathways. In this work, a comparative evaluation of α-MnO₂ and δ-MnO₂ phases is reported, focusing on their performance as active electrode coatings. Four MnO₂ variants were synthesized via hydrothermal processing, yielding two α-type and two δ-type compositions with distinct structural and morphological characteristics. The coatings were deposited onto stainless-steel mesh substrates and characterized by XRD, FT-IR, and SEM, confirming phase purity and the formation of hierarchical nanostructures that directly influence electrolyte accessibility.

Electrochemical testing cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy, revealed that δ-MnO₂ exhibited superior behavior, achieving specific capacitances above 300 F g⁻¹ at 0.1 A g⁻¹ and enhanced cycling stability (>90% capacitance retention after 2000 cycles). Nyquist analysis confirmed reduced charge-transfer resistance for δ-MnO₂, attributed to improved interlayer ion diffusion and increased electroactive surface area.

These findings highlight δ-MnO₂ as a high-performance material for supercapacitor applications, and demonstrate its potential integration in scalable metal-mesh-based electrode architectures for energy storage systems.

Keywords: MnO₂ coatings, energy-storage electrodes, hydrothermal synthesis, supercapacitors.

The development of renewable lubrication strategies is increasingly relevant for advancing sustainable surface engineering practices. Friction and wear are major contributors to energy losses and premature material degradation in mechanical systems, particularly in carbon steel components widely used in industrial applications. Replacing petroleum-based lubricants with bio-based alternatives represents a promising pathway to reduce environmental impact while maintaining or improving tribological performance.

This study evaluates the friction and wear behavior of carbon steel (AISI 1020) lubricated with Moringa oleifera oil, a renewable vegetable oil characterized by high oleic acid content and good oxidative stability. Tribological tests were performed under controlled conditions to measure the coefficient of friction and assess wear mechanisms. Post-test surface analyses were conducted to examine wear tracks and identify evidence of boundary film formation.

The results indicate that Moringa oleifera oil provides stable friction behavior and contributes to wear mitigation in carbon steel under the tested conditions. The lubricant promotes the formation of a protective tribofilm, reducing direct metal-to-metal contact and limiting material removal. These findings demonstrate that renewable vegetable oils can offer effective lubrication performance while supporting environmentally responsible surface engineering solutions.

From a sustainability perspective, the adoption of plant-based lubricants contributes to reduced dependence on fossil-derived products, lower toxicity risks, and improved biodegradability. Additionally, by mitigating wear and extending component lifetime, renewable lubrication strategies support circular economy principles aimed at resource efficiency and durability enhancement.

Overall, this work highlights the potential of Moringa oleifera oil as a viable renewable lubricant for surface engineering applications, bridging tribological performance with sustainable materials innovation.