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2. Hydrophilization of rice seeds by plasma treatments – super-hydrophilic surface finish and hydrophobic recoveryAlenka Vesel, Anca Macovei, Alma Balestrazzi, Dane Lojen, Gregor Primc, Rok Zaplotnik, Nives Ogrinc, Marián Lehocký, Miran Mozetič, 2025, original scientific article Abstract: The hydrophobic character of rice seeds protects them from quick water adsorption and, thus, premature germination. This property is, however, a drawback in modern agriculture, where rapid and uniform germination represents a high-quality trait. A method for rapid hydrophilization of the Lomello variety of rice is presented. The rice seeds were treated with low-pressure gaseous plasma to tailor the wettability. The treatment of seeds with hulls with oxygen plasma afterglow enabled the super-hydrophilic surface finish within 10 ms. Such extremely fast hydrophilization was attributed to irreversible surface oxidation by neutral oxygen atoms whose flux onto the seeds was approximately 3 × 1023 m−2s−1. Dehulled seeds were made super-hydrophilic by subsequent treatments with hydrogen and oxygen plasma, and the required dose of O atoms was between 2 × 1023 and 6 × 1024 m−2. Larger doses caused a loss of the super-hydrophilicity. Hydrophilization kinetics is proposed and supported by measuring surface wettability, morphology, and composition using various techniques. The hydrophobic recovery of seeds with hulls is marginal within the first few days after plasma treatments, but dehulled seeds lose the super-hydrophilic surface finish within a few minutes after the plasma treatment when stored at ambient conditions.
Keywords: rice seed, water adsorption, surface treatment, wettability, super-hydrophilicity
Published in DiRROS: 10.11.2025; Views: 216; Downloads: 129
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3. Simple and fast wettability control of aminosilanized surfaces with carboxylic acidsAndraž Černoga, Jelena Papan Djaniš, Darja Lisjak, Jernej Iskra, Griša Grigorij Prinčič, 2025, original scientific article Keywords: reverse wettability, aminosilane, ion pair, self-cleaning surface
Published in DiRROS: 27.10.2025; Views: 279; Downloads: 144
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4. Surface engineering of aerospace aluminium alloys : understanding alloying effects on chemical pre-treatment and sol-gel coating adhesionJ.B.P. Van Dam, Urša Tiringer, Shoshan Abrahami, Ingrid Milošev, H. Terryn, Janez Kovač, Johannes M. C. Mol, 2024, original scientific article Abstract: The sol–gel process is a chemical surface preparation method based on hydrolysis and polycondensation reactions for enhanced adhesion for metallic substrates in adhesive bonding and coating applications. This paper describes an investigation into the effect of the microstructural complexity of two commonly used aerospace aluminium alloys (AAs) 2024-T3 and 7075-T6, on the response to different surface pre-treatments before deposition of the sol-gel coating and subsequent adhesive bonding. Different surface pre-treatments, including two abrasive treatments and three chemical surface pre-treatments were used, and their effect on surface chemistry, wettability and roughness was assessed. Surfaces were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, profilometry and static contact angles. A hybrid silane sol-gel film was deposited on the differently pre-treated aluminium alloys, an epoxy adhesive was applied and the adhesion properties were evaluated using pull-off testing. The role of the altered physicochemical properties of the pre-treated surfaces was related to the adhesion strength of the sol–gel reinforced epoxy/aluminium interfaces. The microstructural complexity of the aerospace alloys caused non-uniform responses to the pre-treatments, proving the importance of compatibility between material and treatment conditions. Statistical analysis revealed that, despite that overall higher adhesion values were obtained on rougher surfaces, only a strong correlation exists between the surface hydroxyl fraction and adhesion strength. The relation of roughness and water contact angle to interfacial adhesion was found to be non-significant. The findings of this study underscore the critical role of surface pre-treatments and their impact on adhesion strength in aerospace aluminium alloys, providing valuable insights for the effective utilization of sol-gel coatings in adhesive bonding and coating processes.
Keywords: sol-gel, surface pre-treatment, surface morphology, wettability, adhesive
Published in DiRROS: 17.04.2025; Views: 701; Downloads: 311
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5. Sustainable biocarbon/tung oil coatings with hydrophobic and UV-shielding properties for outdoor wood substratesLaetitia Sarah Jennifer Marrot, Mariem Zouari, Matthew Schwarzkopf, David Brian DeVallance, 2023, original scientific article Abstract: With wood regaining substantial interest as a construction material due to sustainability concerns and aesthetics trends, efficient and safe protection methods are needed to prevent the discouloration and the loss of mechanical properties of this renewable and UV-sensitive material. In this study, sustainable coatings comprising 0 to 20 wt % biocarbon (BC) dispersed in tung oil were developed for wood protection. BC particles were added as ultraviolet (UV) absorbers and were produced by various carbonization routes. The BC powders were characterized in terms of particle size and surface functional groups by Fourier-Transform infrared, and the UV and visible absorbance of dispersed BC powders in water solutions were related to these characteristics.
Two wooden substrates (beech and oak) were coated with the developed coatings and the samples underwent six months of onsite weathering. While the total colour change of uncoated samples and tung oil-coated substrates without BC kept increasing over time and resulted in a clear alteration of the wood surface aesthetics, an increased BC content in the coatings led to enhanced colour stability, with alteration of the colour close to 2 for both wood species after six months of weathering for 10 and 20 wt% BC.
Coating with tung oil made the wooden substrates, initially hydrophilic, become hydrophobic, and the further introduction of biocarbon increased hydrophobicity. However, the increase in BC content was not correlated with an increase in water repellence, the highest water contact angle being observed for 5 % BC, and no further improvement in hydrophobicity was observed with higher BC content. The weathering negatively affected the water repellence of all the samples (i.e., reference samples and coated samples with various BC content). However, the introduction of 20 % BC best protected the decrease in water repellence induced by the onsite weathering.
Keywords: biocarbon, biochar, coating, wood protection, hydrophobic coating, wettability
Published in DiRROS: 30.05.2023; Views: 1677; Downloads: 1297
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6. Influence of drying temperature on properties of wood surfacesMilan Šernek, 2002, original scientific article Abstract: This article deals with modifications of wood surface properties induced by different drying temperatures. The aim of the study was chemical and physical characterization of a wood surface concerning low and high temperature exposure. Additionally, the correlation between the chemical composition of a wood surface and its wetting capacity were investigated. X-ray photoelectron spectroscopy and contact angle measurements were conducted. Two wood species, yellow poplar (Liriodendron tulipifera) and southern pine (Pinus taeda) were studied. The results showed that the percentage of carbon increased with drying temperature, and consequently, the percentage of oxygen decreased. The samples exposed to high drying temperatures indicated a higher content of extractives on the wood surface. These samples exhibited the highest contact angle and the lowest wettability
Keywords: površina lesa, sušenje, kontaktni kot, rentgenska fotoelektronska spektroskopija, omočitev, ekstraktivne snovi, wood surface, drying, contact angle, XPS, wettability, extractives
Published in DiRROS: 12.07.2017; Views: 5825; Downloads: 2388
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