In this study, the AA1100 aluminum alloy underwent the plasma electrolytic oxidation (PEO) process to enhance its adhesion to a thermoplastic composite of polyetherimide (PEI) reinforced with glass fiber, following ASTM D1002:10 standards. A 2³ factorial design was employed, varying three parameters in the oxidation process: immersion time, applied electric potential, and electrolyte concentration (Na₂B₄O₇). The joining of aluminum and thermoplastic composite samples was achieved through oxy-fuel welding (OFW), using oxygen and acetylene gases. For the characterization of the joined samples, a universal tensile testing machine was utilized with a displacement speed of 1.5 mm/min. The analysis of the oxide coating involved scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Fourier transform infrared spectroscopy (FT-IR). Through variance analysis, it was determined that the statistical model encompasses approximately 80% of the variability in the adhesion process between materials. An improvement of up to 104% in adhesion between the materials was observed with the process, indicating an effective bond due to the presence of the thermoplastic matrix in the treated aluminum sample. This improvement is attributed to the morphology of the oxide coating, resembling corals, with micro-pores and recesses that facilitated mechanical anchoring.

The Plasma Electrolytic Oxidation (PEO) process was investigated to enhance the adhesion of AA2024-O aluminum alloy with a polyetherimide (PEI) matrix composite, using oxy-fuel welding (OFW). A Central Composite Design (CCD) statistical model was used to optimize three independent parameters in PEO: immersion time (s), duty cycle (%), and electrolyte concentration (Na₂B₄O₇·10H₂O), aiming to achieve a maximum value of shear strength of the hybrid joint (in MPa). The hybrid joint without PEO treatment presented a resistance of 2.2 MPa while the best condition presented a resistance of 9.5 MPa, resulting in a value 4× higher than the untreated material, due to the characteristics of the coating, which presented a more hydrophilic surface, allowing better mechanical interlocking with the polymer matrix and resulting in mixed-mode failure (adhesive, cohesive, and light fiber). In addition to improving adhesion, the PEO treatment provided better corrosion resistance to the alloy, forming an inert aluminum oxide (Al₂O₃) coating, with an improvement of approximately 99.84% compared to the untreated alloy. The statistical design covers about 77.15% of the total variability of the PEO + welding process, with independent factors influencing around 48.4% of the variability.

This paper reports the optimization of a two-step atmospheric pressure plasma process to modify the surface properties of a polyurethane (PU) foam and, specifically, to prepare a superhydrophobic/superoleophilic absorbent for the removal of oils and nonpolar organic solvents from water. In particular, in the first step, an oxygen-containing dielectric barrier discharge (DBD) is used to induce the etching/nanotexturing of the foam surfaces; in the second step, an ethylene-containing DBD enables uniform overcoating with a low-surface-energy hydrocarbon polymer film. The combination of surface nanostructuring and low surface energy ultimately leads to simultaneous superhydrophobic and superoleophilic wetting properties. X-ray photoelectron spectroscopy, scanning electron microscopy and water contact angle measurements are used for the characterization of the samples. The plasma-treated PU foam selectively absorbs various kinds of hydrocarbon-based liquids (i.e., hydrocarbon solvents, mineral oils, motor oil, diesel and gasoline) up to 23 times its own weight, while it completely repels water. These absorption performances are maintained even after 50 absorption/desorption cycles and after immersion in hot water as well as acidic, basic and salt aqueous solutions. The plasma-treated foam can remove mineral oil while floating on the surface of mineral oil/water mixtures with a separation efficiency greater than 99%, which remains unaltered after 20 separation cycles.

Bacterial nanocellulose derived from kombucha exhibits remarkable physicochemical properties, but its high hydrophilicity limits its application in water-resistant materials. This study investigated the surface modification of nanocellulose using amorphous carbon and silicon-based thin films via low-pressure plasma treatment to induce hydrophobicity. Samples were exposed to plasma for 30, 60, and 90 minutes and analyzed using FTIR spectroscopy, macroscopic observations, and wettability tests. The results showed progressive surface darkening, the appearance of iridescent regions and attenuation of the O–H (∼3300 cm−1) and C–H (∼2900 cm−1) bands, indicating removal of polar groups, dehydration and partial degradation of the cellulose matrix. The emergence of a (∼1720 cm−1) C=O band and changes in the (1050–1000 cm-1) range suggest surface oxidation and silicon deposition from degraded sealing silicone. Statistical analysis revealed a correlation between plasma exposure time and chemical modifications, albeit without formal statistical significance. It is concluded that plasma treatment is an effective, accessible, and sustainable strategy to functionalize nanocellulose surfaces, imparting hydrophobic properties and enhancing its potential for use in advanced technological applications.

Plasma Electrolytic Oxidation (PEO) is an advanced electrochemical treatment for lightweight alloys such as Al, Ti, and Mg. It is an environmentally friendly process that utilizes silicate, aluminate, and phosphate-based electrolytes to produce oxide/ceramic coatings with superior physical and chemical properties compared to conventional techniques. Despite extensive studies on coating morphology and performance, systematic investigations into PEO parameter optimization for reducing energy consumption, a major limitation of the process, remain scarce. To address this gap, a full factorial design (23) was employed to evaluate the influence and determine optimized values of three parameters (treatment time, duty cycle, and electrolyte concentration) that minimize average power consumption. The novelty of this work lies in the quantitative demonstration that statistical modeling can disentangle the relative contributions of process variables to energy demand, offering new insights into PEO mechanisms and paving the way for more cost-efficient and sustainable applications. Average power consumption ranged from 3.68 W to 13.67 W, with lower values linked to shorter treatment times and reduced duty cycles. Analysis of variance (ANOVA) confirmed the model’s statistical robustness, explaining 89.86% of the response variability with a low noise level (0.93%). Treatment time and duty cycle were the only statistically significant factors (p < 0.05), contributing 8.85% and 66.98%, respectively. Beyond technological relevance, these findings provide a scientific framework for understanding parameter interactions in PEO and open promising avenues for future industrial and research applications.