Water Repellency Research Articles

Oleogel Microsphere‐Based Composite Protective Coatings with Room‐Temperature Self‐Healing Enabled by a “Soft + Hard” Hybrid Architecture

AbstractIntrinsically self‐healing coatings are compelling candidates for highly reliable anti‐corrosion technologies because of their easy implementation, low cost, and repeatable self‐healing. However, most of these coatings require intervention to initiate healing due to the locking of their chain segments under ambient conditions (to provide sufficient mechanical strength). Herein, a “soft + hard” hybrid architecture strategy of preparing oleogel‐based protective coatings with room‐temperature and repeatable self‐healing is proposed by embedding “soft” self‐healing and viscoelastic oleogel microspheres (OMs) in “hard” waterborne epoxy matrix. Such a decoupled design affords both instantaneous healing without external stimuli (crack narrowing within 10 min and protection recovered within 5 h) and good mechanical properties (improved wear resistance with an 80% reduction in friction coefficient, a 63% reduction in wear volume, as well as a maintained adhesion strength of 96%). The slippery and hydrophobic OMs also bring anti‐biofouling, interfacial water repellency, and inhibitor loading‐release features, leading to coatings with superior corrosion protection (>1010 Ω cm2 impedance modulus throughout 110 d) rather than just their self‐healing. This work demonstrates a feasible approach to integrating room‐temperature repeatable self‐healing and sufficient mechanical strength in future coating design.

Rational design of a novel siloxane-branched waterborne polyurethane coating with waterproof and antifouling performance

Inferior water resistance remains a bottleneck in the development of the waterborne polyurethane (WPU) coatings industry. Herein, a novel strategy for the facile preparation of hydrophobic antifouling WPU coatings is presented in this work. Specifically, a series of siloxane-branched modified polyurethanes (BSi-WPU) was prepared by synergistically introducing diol-hydroxyl single-ended silicone oil (DSSiO) as the branched modified monomer and hydroxylated fluorinated siloxane (HTFSi) as the functional soft-chain segment into the WPU system via a simple polycondensation process. The effects of the introduction of DSSiO on the water resistance and mechanical properties of the BSi-WPU were investigated, and the antifouling and chemical resistance of the modified coatings were also examined. The results demonstrated that the branched DSSiO possessed excellent surface migration efficiency, which effectively improved the water repellence (contact angle up to 109.3°), waterproofness (absorption reduced to 7.5 %), and hydrolysis resistance (minimum 1.6 % loss of strength after water immersion) of the coatings. In addition, owing to thermodynamic immiscibility, the incorporation of HTFSi and appropriate DSSiO amounts enlarged the microphase separation of the polyurethane, whereby the material exhibited improved mechanical properties over ordinary polyurethanes. More importantly, based on the surface enrichment of low-surface-energy silicon and fluorine units, the coatings exhibit excellent repellency to contaminated liquids and corrosive chemical solutions. This approach provided a more applicable alternative idea to the industrial fabrication of hydrophobic and antifouling WPU coatings.

Construction of superhydrophobic tungsten carbide via laser processing and its thermal, chemical and mechanical properties

Designing microscale microstructures on superhard materials and achieving superhydrophobic surfaces through wettability adjustment have promising application prospects. However, current popular methods for preparing superhydrophobic surfaces have not designed and optimized the microstructures, and achieving superhydrophobicity on superhard materials using conventional industrial methods remains a tremendously challenge. Here, we propose a novel multiscale microstructure design on superhard tungsten carbide (WC) alloy material, achieved through laser processing, which exhibits superhydrophobicity after low surface energy modification. To ensure the designed microstructures possesses excellent mechanical strength and wettability, the influence of size parameters on mechanical strength and their relationship with wettability through finite element analysis (Abaqus) and characterization techniques were conducted. Based on the optimized robust multiscale structure, we also investigated the comprehensive properties of the superhydrophobic surface. The thermal, chemical, and mechanical stability of the WC superhydrophobic surface were explored through experiments involving temperature exposure, immersion in acid-base solutions, friction and wear tests. Our findings demonstrate that the superhydrophobic WC surface exhibits excellent temperature resistance over a wide range, maintaining superior water repellency even after prolonged exposure to chemical solutions and mechanical abrasion tests. In addition, the substrate's microstructure and SiO2 nanoparticles successfully replicated on the optical glass surface through molding technology, creating a consistently superhydrophobic glass microstructure. This work provides a new perspective for designing superhard alloy materials with robust microstructures and offers potential for a series of applications, such as mold, semiconductor and solar cell.

Emulsified oil-water separation properties of superhydrophobic/superoleophilic surface by emulsion droplets impacting dynamic behavior

Superhydrophobic/superoleophilic materials with excellent separation property are urgently needed for the clarification of water from oil-water emulsions, however, the lack of interfacial contact dynamics in the separation process is not beneficial to extensive application for them. Herein, a superhydrophobic/superoleophilic mesh was successfully prepared by spraying fluorinated polyurethane (FPU), silicon dioxide (SiO2) and carbon nanotubes (CNTs). The prepared mesh exhibited excellent superhydrophobic/superoleophilic performance, accomplishing a 1636.9 L m−2h−1 flux and a high separation efficiency above 99.8 % for water-in-oil (W/O) emulsions. The dynamic behavior of emulsion droplets impacting on the prepared mesh was innovatively investigated by experiment and simulation. As the oil content of emulsion droplets increased from 0 wt% to 2 wt%, the maximum spreading diameter (Ddmax) of emulsion droplets decreased from 5.57 mm to 5.28 mm, which can be attributed to the oil capture ability of the superhydrophobic/superoleophilic surface. Simultaneously, the maximum jet height (Hdamx) and the retraction velocity of the droplets firstly decreased and then increased. The results revealed that the oil film captured on the surface possessed good lubricity and water repellency, which could accelerate the dislodging of water from the surface and enhance separation performance. The separation mechanism of superhydrophobic/superoleophilic surface revealed by the contact dynamics study provided a novel path for the fabrication of emulsified oil-water separation materials.

Treatment of Bamboo for Sustainable Construction Practise: A Comprehensive Review

Abstract Bamboo is a versatile and sustainable natural resource that has been used for centuries by numerous cultures. Untreated bamboo, on the other hand, has limitations in terms of durability, strength, and decay resistance, which limit its usage in specific conditions. To overcome these restrictions and realise its full potential, researchers have investigated various bamboo treatment methods. This research presents an overview of bamboo treatment methods, effects on their performance, and emphasises possible uses in a variety of construction practises. The study looks into the usage of synthetic resin and synthetic rubber as bamboo protective coatings. These coatings improve durability, water repellence, dimensional stability, mechanical strength, and fungal growth resistance. They are also simple to use and contribute to environmentally friendly practises. To protect bamboo from fungal deterioration and insect infestation, chemical substances such as boron-based additions, zinc chloride, sodium pentachloro-phenate, and copper-chrome-arsenic (CCA) are employed as preservatives. These chemicals increase the longevity of bamboo while also ensuring its structural integrity. The use of epoxy resins to improve the tensile strength of bamboo composites is also being observed. It increases flexural and compressive strength by improving adhesion between bamboo fibres and the matrix. The use of epoxy glue also retains the natural strength and durability of bamboo. Heat treatment of bamboo entails treating it to high temperatures in order to enhance its qualities such as dimensional stability, hardness, and resistance to decay and insect assault. Heat-treated bamboo is used in building, furniture, flooring, and composite materials. Understanding and implementing these treatment procedures can help to encourage the wider use of bamboo as a sustainable and environmentally friendly construction material. The findings of this study have the potential to drive decision-making, encourage innovation, and have a positive impact on the environment, society, and economy. Bamboo may be used as a viable alternative to traditional materials in a variety of sectors by exploiting its unique qualities and improving its durability and strength.

Winter cover crop performance in the Southern Piedmont region of South Carolina

AbstractCover crops (CCs) offer in‐field and environmental benefits when integrated into cropping systems. Low CC adoption in the Southern Piedmont region of South Carolina is partially due to the lack of information on CC performance and benefits within the region. To address this, eight winter CCs and a fallow/pigweed (Amaranthus spp.) treatment were investigated for their influence on soil temperature, volumetric water content (VWC), percent cover, biomass, and the occurrence of soil water repellency (SWR). A randomized complete block design experiment was conducted in the fall and winter of 2021–2022 (EXP A) and repeated in 2022–2023 (EXP B). Experiments were treated separately as methods were revised for EXP B. CCs minimally influenced soil VWC over both experiments with no consistent trend. CC did not influence soil temperatures during EXP A. In EXP B, the fallow/pigweed had the highest soil temperatures on two (out of 10) measuring events (p < 0.05). No SWR was found in either experiment. Establishment and fresh and dry CC biomass were most likely influenced by air temperatures and daylight hours driving germination during days with minimal rainfall. In both experiments, annual rye (Lolium multiflorum) produced cover quickly and yielded high biomass. Crimson clover (Trifolium incarnatum) took longer to establish but also yielded one of the highest biomasses. This study demonstrated that winter CCs had little influence on soil physical properties and that while cereal rye (Secale cereale) is a common CC utilized for erosion control, the greater biomass and surface roots of annual rye make it a superior CC for use in Southern Piedmont agroecosystems.

Impact of tightening environmental regulations against long-chain perfluoroalkyl acids on composition of durable water repellents containing side-chain fluorinated polymers

Tightening of environmental regulations against long-chain perfluoroalkyl acids (PFAAs) since the 2000s may have led to significant increases in the occurrence of short-chain PFAAs in the environment. Understanding the impact of the regulations on composition of durable water repellents (DWRs) is imperative to guide implementation of pragmatic actions during their use and end-of-life treatment. Substantial decreases in the frequencies of detection and concentrations of long-chain PFAAs and long-chain PFAA-precursors, and substantial increases in those of short-chain PFAAs and short-chain PFAA-precursors, have been observed in the impurities and hydrolysis products of side-chain fluorinated polymers (SCFPs). Comparison of profiles among the DWRs containing fluorinated ingredients in 2011 indicated that DWRs containing C8F17- and C10F21-SCFPs were the dominant products and accounted for 90 % of the samples, whereas DWRs containing C4F9- and C6F13-SCFPs were the dominant products and accounted for 70 % of the samples collected in 2021. Tightening of the regulations have caused decreasing applications of long-chain SCFPs and increasing use of short-chain SCFPs in DWRs containing fluorinated ingredients. The ingredients of one DWR were changed from PFAS-free alternatives to short-chain SCFPs, whereas those of another DWR were changed from short-chain SCFPs to PFAS-free alternatives. The presence of unexplained extractable organic fluorine has been observed in DWRs containing fluorinated ingredients, which may be difficult to be hydrolyzed and form known compounds. A historical series of DWRs available from before and after the tightening of regulations and a multifaceted analytical technique consisting of combustion ion chromatographic and mass spectrometric approaches combined with two extraction techniques involving ultrasonic treatment and alkaline hydrolysis revealed the impact of tightening regulations on composition of DWRs.

Hydrophobic Coating on Metal Matrix Composites

Abstract: The combination of traditional aluminum metal matrix composites (MMCs) with innovative reinforcement materials offers promising avenues for enhancing material properties and expanding application domains. In this study, aluminum matrix composites reinforced with ZrB2 (zirconium diboride) particles were fabricated using a stir casting technique. The addition of ZrB2 to the aluminum matrix aimed to improve mechanical strength, wear resistance, and thermal stability. Following fabrication, the resulting composite specimens were subjected to a surface modification process involving the application of a superhydrophobic coating. The superhydrophobic coating, characterized by its extreme water repellency and self-cleaning properties, was applied to the surface of the aluminum-ZrB2 composites using a spray-coating method. The coating material consisted of a hydrophobic compound integrated with nanostructured particles, engineered to achieve a hierarchical surface morphology that mimics natural superhydrophobic surfaces. The coated specimens were evaluated for their water repellency, contact angle measurements, and durability under various environmental conditions. The results of this study demonstrated that the combination of aluminum metal matrix composites with ZrB2 reinforcement, coupled with the application of a superhydrophobic coating, yielded surfaces with exceptional water-repellent properties. The coated composites exhibited high contact angles and low water adhesion, indicative of their superhydrophobic nature. Furthermore, the durability tests revealed the robustness of the coating against mechanical abrasion and environmental exposure. Overall, the integration of aluminum-ZrB2 composites with a superhydrophobic coating holds significant promise for applications requiring water-resistant surfaces, suchas aerospace components, marine structures, and outdoor equipment. This researchcontributes to advancing the development of multifunctional materials with tailoredsurface properties, paving the way for improved performance and longevity in diverse engineering applications

Optimizing aluminum alloy performance for marine superstructures: Advanced nanocomposite coating for enhanced corrosion resistance, flame retardancy, and mechanical strength

Aluminium alloys find applications in the marine industry for boat hulls, ship superstructures, and offshore structures due to their corrosion resistance in marine environments. Nanocomposites incorporating impermeable two-dimensional materials hold a particular interest in safeguarding metals against corrosion. The introduction of 3-(m-aminophenoxy)propyltrimethoxysilane (APPMS) functionalized hafnium nitride (HfN) into a coating matrix can enhance the barrier effect owing to its exceptional chemical and thermal stability. Integrating functionalized HfN into graphitic carbon nitride (GCN) within polyurethane (PU) leads to improved corrosion protection and fire-retardant properties. Through electrochemical techniques in chloride environments, the protective efficacy of aluminum coated with polyurethane containing varying concentrations of functionalized HfN/GCN was investigated. The resulting PU with functionalized HfN/GCN composite demonstrates superior flame-retardant capabilities, with significant reductions in peak heat release rate (PHRR), total heat release (THR), and total smoke production (TSP) compared to pure PU. According to electrochemical impedance spectroscopy (EIS) measurements, PU/functionalized HfN/GCN exhibits enhanced coating resistance of 2.26×1010 Ω.cm2, even after 20 days of exposure to seawater. Featuring a water contact angle (WCA) of 161°, the newly developed PU/functionalized HfN/GCN coating displays exceptional water repellency. Moreover, PU/functionalized HfN/GCN demonstrates good mechanical properties in terms of adhesion strength and hardness within the PU substrate, enabling the coating to maintain its integrity even after prolonged immersion. The investigation presents a promising approach for developing advanced coatings tailored for marine applications, offering improved corrosion protection, fire resistance, water repellency, and mechanical durability. Thus, the PU/functionalized HfN/GCN nanocomposite shows promise as a viable coating component in marine applications.

The water repellency of earthworm (Lumbricus terrestris) casts depends on their particle size composition, organic carbon content and calcium carbonate content

The water repellency of earthworm (Lumbricus terrestris) casts depends on their particle size composition, organic carbon content and calcium carbonate content

Bio-inspired surface structures promote optical transmittance and hydrophobicity in cellulose-based films for self-cleaning perovskite solar cells

Developing suitable light management layers can improve the lifetime and efficiency of solar cells and other optoelectronics. Here, a bioinspired approach to produce all-biobased films with high anisotropic light scattering and superhydrophobicity is presented as a route toward sustainable light management layers for photovoltaics. The multifunctional films are achieved by replicating leek leaves onto cellulose acetate, producing hierarchical surface structures. The free-standing films show a transmittance of ≈94% and a haze of ≈54% at the wavelength of 550 nm. Moreover, anisotropic advancing contact angles of up to 160° and 156° in cross directions are achieved through tailoring a carnauba wax coating. Using the replica as the light management layer on perovskite solar cells improved the power conversion efficiency by 6 ± 0.3%. Meanwhile, the surface water repellency facilitates self-cleaning, ensuring maximum incident light over time by tackling dirt accumulation. Furthermore, the method can be potentially employed to fabricate substrates from virtually any leaf or patterned surface as the initial replication template.

Investigation on PFAS Sources and Removal in a Municipal Wastewater Treatment Plant

PFAS (per- and poly-fluoroalkyl substances) is a complex family of manmade highly fluorinated aliphatic organic chemicals including thousands of chemical structures identified. PFASs were first synthesized in the 1940s and their physical and chemical properties such as oil and water repellency, temperature resistance, and friction reduction were then used in a wide range of products and industrial applications. Awareness about the possible health and environmental risks related to exposure to these substances has only risen in recent years and is resulting in the inclusion of such compounds in the Proposal for the recast of the Directive of the European Parliament and of the Council concerning urban wastewater treatment.A research was carried out at a municipal wastewater treatment plant (MWWTP) in Northern Italy to define the inflowing load of PFAS, the main load sources and the removal efficiency of the treatment processes.First, the contribution of the water supplied to the local population was excluded by means of specific chemical analyses. Then, the 100 industrial settlements served by the MWWTP were examined for the raw materials used, the final products and the productive cycle and 8 of them were selected as potential sources. A sampling campaign was carried out and the specific PFAS load was calculated. The total PFAS load entering the MWWTP was calculated from the analytical results and the flow. The percent contribution of each of the selected settlements to the total PFAS load was then calculated. 40% derives from a textile dyeing industry and 32% from a waste platform receiving also landfill leachates. 89% of the total PFAS load comes from the sum of such contributions and two other activities: the processing of slaughterhouse wastes and the production of chemicals for agriculture.Specific investigations lead to attribute an important role also to fire drills and fire extinguishing, using Aqueous Film Forming Foams (AFFF) containing PFAS. So, domestic contribution can be held as negligible.The removal in the WWTP was null and, in some cases, negative. As also reported in the literature some precursors can be transformed in PFAS during the biological process and some sludge accumulated compounds can be released.

Monitoring changes in hydric properties of treated stone material with conservation products by time-sequential IR thermography

A methodological approach for a semi-quantitative non-destructive testing (NDT) of the effects on hydric properties after the application of different conservation treatments (commercial ethylsilicate and siloxane compounds with consolidant, water repellent or consolidant + water repellent properties) is presented in this study. The NDT used for this purpose is a simplified method of time-sequential infrared thermography (IRT) on stone (granite and marble, treated and untreated) from the Roman theatre of Merida (Spain), which was listed by UNESCO as World Heritage Site in 1993.As water evaporation modifies temperature intensely, IRT enables monitoring the response of the stone samples during water absorption-evaporation processes. The comparative analysis between treated and non-treated specimens was performed by calculating the rate of surface apparent temperature change (ΔoC/h) value. The capillary rising test, monitored by IRT, clearly showed a different response of the samples treated with water-repellent treatments, proving their efficiency. Samples treated with organosilicic compounds showed a large and rapid drop in apparent surface temperature, indicating that water accesses rapidly.Results from the evaporation test also show this difference. The surface apparent temperature increased immediately in samples with water-repellent treatments, in which water does not enter inside stone, but remains on the surface. Samples with ethyl silicate, again, show a greater difference with respect to untreated samples, taking longer to recover surface apparent temperature, because the water is retained inside the stone for longer.This study proved simplified time-sequential IRT as a reliable technique for assessing the efficacy of conservation treatments applied to stone materials in laboratory.

A robust and multifunctional superhydrophobic coating based on natural palygorskite for corrosion protection of aluminum alloys

Biomimetic superhydrophobic surfaces have become an increasingly hot topic in the area of aluminum alloy protection. However, it remains a significant challenge to construct superhydrophobic coatings with reliable durability and multifunction through simple and economical strategies. In this study, we designed a novel superhydrophobic coating with a water contact angle of ∼165.0° and a sliding angle of ∼2.4° on Al alloys by spraying hydrophobically modified natural palygorskite (SH-PAL) on the pre-cured epoxy resin (EP). The resulting superhydrophobic coating (EP@SH-PAL) exhibits good mechanical resistance, UV resistance, hot water repellency, chemical stability, thermal stability, and self-healing capabilities against plasma etching. Corrosion tests reveal that the protection efficiency of the EP@SH-PAL sample is up to 99.98 %, which remains at a high value of 90.30 % even after 20 days of immersion in 3.5 wt% NaCl. This improved corrosion resistance is attributed to the synergistic physical shielding from the SH-PAL topcoat and the EP primer. Meanwhile, molecular dynamics simulations of the mechanical durability and corrosion resistance of the EP@SH-PAL coating were performed to support the experimental results at the microscopic level. In addition, the above-prepared superhydrophobic coating also demonstrates excellent self-cleaning and antifouling characteristics. This research will provide a new method for fabricating low-cost, multifunctional, superhydrophobic anticorrosion coatings on aluminum alloys and other metal substrates.

SUPERHYDROPHOBIC ALL-CELLULOSE COMPOSITE VIA HEXADECYLTRIMETHOXYSILANE AND HDTMS/SILICA

All-cellulose composite (ACC) is a novel single polymer composite (SPC) that consists of cellulose for both reinforcing fiber and matrix phases. ACC has good mechanical, thermal, and optical properties due to compatibility of reinforcing fiber and matrix phases. However, abundant hydroxyl (OH) groups in the cellulose structures resulted in higher hydrophilicity of ACC, thus limiting the potential use in outdoor applications. In this study, ACC was fabricated using solvent infusion processing (SIP) from rayon textile with sodium hydroxide (NaOH)/urea solution to partially dissolve the cellulose fibers, followed by regeneration and drying processes. Subsequently, ACC was treated using two different coating solutions: (i) hexadecyltrimethoxysilane (HDTMS) and (ii) HDTMS/SiO2 (silica). As a result, an efficient water repellency for HDTMS/SiO2-treated ACC was observed, showing a water contact angle of 159.3∘, as compared to HDTMS-treated ACC with a water contact angle of 144.1∘. However, a slightly higher water absorption of 52% was observed for HDTMS/SiO2-treated ACC, as compared to only 44% for HDTMS-treated ACC. Both treated ACCs showed smooth and homogeneous structures upon completion of the treatment.

Anti‐/Deicing Membranes with Damage Detection and Fast Healing

AbstractFlexible membrane with good anti‐wettability under giant deformation and fast healing will largely extend its adaptability and life span in anti‐/deicing application. A flexible membrane with significant dynamic water repellency and photo‐/electro‐responsive healing capability is reported, fabricated by combining the covalent grafting of fluorosilane to carbon black (F‐CB) with the optimized ablation difference between thermoplastic polyurethane (TPU) matrix and F‐CB. A rolling angle of below 5° is remained after either being stretching to 1000% strain or 2000 cycles of tensile tests at 400% strain. More importantly, multi‐scale cracks on the membrane can be diagnosed and repaired in real‐time; the healing efficiency reaches above 99% within 90 s even if completely fractured under the effect of both solar irradiation of 0.1 W cm−2 and applied voltage of 20 V; and all‐weather anti‐/deicing has the performance of an icing delay time of 323 s and an ice adhesion strength of <40 kPa, a sharp contrast to the 18 s and 1090 kPa, respectively, for bare metal surface. This work endows anti‐icing membrane with the ability of damage detection and cyclic healing, highly demanded in outdoor anti‐/deicing application that involve inevitable mechanical damages.

Synergistic effect of Al2O3 and MoS2 on the corrosion behaviour of plasma sprayed aluminium matrix composite coating

In this study, the incorporation of alumina (Al2O3) and molybdenum disulfide (MoS2) in Aluminium (Al) was successfully fabricated through shroud plasma spray. This strategic incorporation of MoS2 and Al2O3 effectively fills voids, leading to a remarkable reduction in inherent porosity within the aluminium coating, achieving an impressive ∼76.54 % reduction. These composite coatings exhibited outstanding hydrophobicity (contact angle ∼119°), signifying remarkable water repellency and anti-corrosion properties compared to bare aluminium (contact angle ∼81.7°). During the electrochemical corrosion test, the corrosion rates (CR) of Al coating (CR = 9.14 mpy) was notably around 23 times higher compared to MoS2 and Al2O3 reinforced aluminium composite coating (CR = 0.372 mpy) in a 3.5 wt % NaCl electrolyte. The subsequent post-corrosion analysis further confirmed the composite coating's efficiency in mitigating the impact of corrosive salts, underlining the effectiveness of the hybrid coating in combating corrosion attacks. A corrosion behaviour prediction model was established based on computational and experimental data.

Effects of different tillage and cropping systems on water repellency and hydraulic properties in a tropical Alfisol of southwestern Nigeria

This study examined the effects of growing intercrops (Sorghum, SOR (Sorghum bicolor L. Moench) in between rows of cowpea, COW (Vigna unguiculata) and soybean, SOY (Glyxine max L.Merr)) under different tillage systems on soil physico-chemical properties, soil water sorptivity (Sw), hydraulic conductivity (K), and soil hydrophobicity (R) in tropical Alfisol of Southwestern Nigeria. Results demonstrated cropping systems significantly impacted soil pH under each conventional tillage (CT), no tillage (NT), and compacted no till systems (NTC) tillage system in 2019, but not in the 2020 cropping season. Sorghum-cowpea SC) and sorghum-soybean (SS) intercropping systems under the three tillage systems had higher soil organic matter (SOM) contents than the corresponding sole sorghum (SOR) at the end of the study. Soil water sorptivity differed significantly (p < 0.001) among the cropping systems in 2019 and follows the order: SC > SS > SOY > SOR > COW while in 2020, averaged over three tillage systems, mean Sw values showed an increasing trend in the order: SOR (77.67 cm h-1/2) < COW (82.42 cm h-1/2) < SOY (88.00 cm h-1/2) < SS (88.73 cm h-1/2) < SC (98.29 cm h-1/2). In general, intercropping had a lower R than sole cropping. NTC soil was 46.48% and 56.39%; 32.47% and 41.67% more hydrophobic than soils under NT and CT in 2019 and 2020. Intercropping with legumes might have contributed to the higher K levels. Organic matter in soil improves conductivity by improving soil structure. The intercrop may have improved soil water conservation because of their shading and better soil protection. The study demonstrated that conservation tillage with intercropping could effectively enhance soil hydraulic properties.

Corrosion resistance of a superhydrophobic polypropylene coating on magnesium alloy AZ31

PurposeTo improve the corrosion resistance of magnesium alloys, the construction of protective coatings is necessary to extend the service life of Mg-based materials.Design/methodology/approachSiO2 nanoparticles modified by dodecyltrimethoxysilane (DTMS) were added to the PP and a superhydrophobic Mg(OH)2/PP-60mSiO2 composite coating was fabricated on the surface of AZ31 magnesium alloy via the hydrothermal method and subsequently the immersion treatment.FindingsHydrophilic SiO2 nanoparticles become hydrophobic after modified by DTMS, showing a higher dispersibility in xylene. By incorporating modified SiO2 nanoparticles into the composite PP coating, the hydrophobicity of the layer was enhanced, resulting in a contact angle of 166.3° and a sliding angle of 3.4°. It also improved the water repellency and durability of the coating. Furthermore, the intermediate layer of Mg(OH)2 significantly strengthened the bond between the PP layer and the substrate. The Mg(OH)2/PP-60mSiO2 composite coating significantly enhances the corrosion resistance of the magnesium alloy by effectively blocking the infiltration of the corrosion anions during corrosion. The corrosion current density of the Mg(OH)2/PP-60mSiO2 composite coating is approximately 8.23 × 10–9 A·cm-2, which can achieve a magnitude three times lower than its substrate, making it a promising surface modification for the Mg alloy.Originality/valueThe composite coating effectively and durably enhances the corrosion resistance of magnesium alloys.

Surface-Hydrophobic Al@COFs Core-Shell structured Composites: A class of efficient high-energy fuels

Aluminum powder is a metal fuel with numerous advantages, but it is susceptible to oxidation, which poses challenges for both ignition and combustion efficiency. Addressing these issues in the application of Al powder is crucial for enhancing the specific impulse of rockets and other related applications. By employing the concept of preparing composite materials and combining multiple materials, it is possible to enhance the stability of long-term storage of Al powder and improve ignition and combustion efficiency. This paper delves into the innovative synthesis and application of Al@COFs-based core–shell structured composites filled with AP to enhance stability, reduce ignition delay time, and improve the combustion efficiency of Al powder. To further enhance the water repellency of the composites, fluoroalkylsilanes were used to coat the Al@COFs@AP composites. The fluoroalkylsilane coating not only improves the oxidation resistance of Al but also introduces F, which disrupts the alumina shell of Al during combustion, generating AlF3 and increasing the heat of combustion. The findings presented in this paper will pave the way for the development of advanced aluminum-based materials with enhanced combustion characteristics and broadens the application areas of COFs.