Rough Structure Research Articles

Bio-inspired superhydrophobic fiber membrane for oil-water separation and non-destructive transport of liquids in corrosive environments

Conventional polymer separation membranes or coatings suffer from poor separation performance and serious failure in highly corrosive environments, due to their low chemical and mechanical stability. Herein, a simple electrospraying and electrospinning strategy was used to prepare flexible superhydrophobic carbon fiber membranes (FSCFM). The wettability of FSCFM was improved by forming a lotus leaf-like hierarchical rough structure on its surface. The FSCFM exhibited an excellent permeation flux of immiscible oil-water mixtures (up to 15,800 L m−2 h−1) and water-in-oil emulsions (over 5500 L m−2 h−1), while the separation efficiencies were always kept at more than 99 % after 25 consecutive separations. Even in corrosive environments, its separation performance did not show any degradation. Notably, except for recovering floating oil under external driving forces with excellent cyclic stabilities, FSCFM was also able to transport various corrosive solutions with high efficiencies (99.9 %). After multiple mechanical damages and bending cycles, the FSCFM remained superhydrophobic. It could also maintain its repellency in strong acids/bases, high salt solutions and even under high-temperature environments (94.5 °C). These superior properties make it a strong candidate for oil-water mixture/emulsion separation and non-destructive transport of highly corrosive fluids.

Highly transparent and highly hydrophobic coating for outdoor camera window glass: Fabrication, transparency, and hydrophobicity

Highly transparent, superhydrophobic coatings are highly desirable for maintaining long-lasting clarity for outdoor camera windows. In this study, the authors present a simple approach to create a wide–range anti-reflective and highly hydrophobic layer on a glass surface. This is accomplished through a hydrothermal alkali etching process combined with a dip-coating process using 1 H, 1 H, 2 H, 2 H-Perfluorooctyltrimethoxysilane (POTS). The sample, etched for 20 h and modified by POTS, exhibiting an average transmittance of 96.5 %, a water contact angle (WCA) of 140° and a sliding angle (SA) of 40°. The results of the water spray experiment indicate this surface exhibits excellent water repellent performance, preventing water droplets larger than 0.01 mm in size. The relationship between optical transmittance and etching depth was thoroughly studied, revealing that an etched depth ranging from 200 nm to 600 nm yields optimal wide-spectrum anti-reflective properties. Furthermore, the influence of surface roughness on apparent WCA and SA was investigated. It was found that root mean square (RMS) roughness can be an effective factor to predict the apparent WCA of a surface, while both the RMS roughness and morphological structure affect the SA.

Construction of durable, multifunctional superhydrophobic wood surface via ɛ-polylysine/PDMS/wax treatment

In addressing the limitations of wood's susceptibility to water and moisture, this study explored the development of a durable, superhydrophobic surface through a novel ɛ-polylysine/polydimethylsiloxane (PDMS)/wax composite system. Leveraging the layer-by-layer (LBL) assembly, the incorporation of cationic ɛ-polylysine not only improved the adherence of PDMS and wax to the wood surface through electrostatic attraction but also facilitated a more uniform distribution, achieving optimal hydrophobicity at a ɛ-polylysine concentration of 2 g/L. The synergistic effect of the wood's natural rough structure and the deposition of these hydrophobic substances endowed the treated wood with superhydrophobic properties, showcasing exceptional self-cleaning capabilities by efficiently repelling a variety of liquid contaminants. Durability assessments through sandpaper abrasion, chemical exposure, and accelerated weathering tests confirmed the enhanced long-term stability of the treated wood surfaces. Furthermore, the incorporation of ε-polylysine provided nice antimicrobial properties, showing a substantial reduction in bacterial adhesion. The ε-polylysine/PDMS/wax composite system represents a significant advancement in the development of multifunctional wood surfaces, promising broader applications in sustainable building materials, furniture, and packaging solutions.

A transparent superhydrophobic coating on wood-based panel surfaces

ABSTRACT A transparent, environmentally friendly and durable superhydrophobic coating preparation process was developed to effectively isolate water molecules in the air, aiming to reduce the use limitations of the wood-based panel substrate and to realize its improved performance in terms of water resistance, stain resistance and durability. This study employs a coating method to apply a silica sol-modified nanocellulose (CNF) and polyvinyl alcohol (PVA) solution onto a wood-based panel substrate, creating a micro-nano rough structure. Subsequently, the vapor deposition method was employed to functionalize the silanol groups on the coating surface, resulting in the formation of fluorinated alkyl groups and achieving transparent superhydrophobic wood-based panels. The water contact angle measures 152.6°, the rolling angle was 4.5°, and the coating exhibits a light transmittance of 92%. Notably, the superhydrophobicity of the coating persists even after repeated polishing paper abrasion, demonstrating excellent anti-pollution self-cleaning properties. This study is of great significance for the long-term use of wood-based panels indoors and outdoors, as well as their application in complex and high humidity environments.

Highly Efficient, Recyclable Microplastic Adsorption Enabled by Chitin Hydrogen Bond Network Rearrangement

AbstractA sustainable strategy based on chitin from waste seafood is proposed to remove nano‐size microplastics in water. A chitin nanofibrous foam is constructed by a new hydrogen bond rearrangement scheme without any crosslinking, which delivers an impressive high adsorption capacity of 411.14 ± 1.50 mg g−1 for small‐sized (< 1 µm) microplastics. This excellent adsorption capacity stems from the rough fibrous surface structure of the highly porous foam, the positively charged nature of the partially deacetylated chitin and other molecular interactions introduced by the activation and increased exposure of ‐OH, ‐NH2 and ‐NHCO‐ groups. Molecular dynamics simulation further demonstrates that C‐H‐π, O‐H‐π, and C = O‐π interactions between the microplastics and chitin foam facilitates the efficient removal of microplastics. A high removal efficiency is maintained even in salty water, a property that exemplifies good adaptability to various water bodies. Finally, two proof‐of‐principle scenarios are presented for converting the recovered microplastics into value‐added products. Thus, the entire cycling strategy represents a powerful remedy for the urgent yet challenging ocean microplastic pollution problem.

Physicochemical properties and fractal characterizations of the functionalized porous clinoptilolites for controlling alginate delivery in growing cauliflower and leaf mustard

Using natural clinoptilolite (NCP) as a carrier and alginate (Alg)-calcium as an active species, the porous silicon calcium alginate nanocomposite (Alg-Ca-NCP) was successfully fabricated via adsorption-covalence-hydrogen bond. Its structural features and physicochemical properties were detailed investigated by various characterizations. The results indicated that Alg-Ca-NCP presented the disordered lamellar structures with approximately uniform particles in size of 300–500 nm. Specially, their surface fractal evolutions between the irregular roughness and dense structures were demonstrated via the SAXS patterns. The results elucidated that the abundant micropores of NCP were beneficial for unrestricted diffusing of Alg-Ca, which was conducive to facilitate a higher loading and sustainable releasing. The Ca content of leaf mustard treated with Alg-Ca-NCP-0.5 was 484.5 mg/100g on the 21st day, higher than that by water (CK) and CaCl2 solution treatments, respectively. Meanwhile, the prepared Alg-Ca-NCPs presented the obvious anti-aging effects on peroxidase drought stress of mustard leaves. These demonstrations provided a simple and effective method to synthesize Alg-Ca-NCPs as delivery nanocomposites, which is useful to improve the weak absorption and low utilization of calcium alginate by plants.

The effect of cutting depth, feed rate, and cutting angle on surface roughness in the lathe process of aluminum 6061.

In the turning process, the machining parameters have a significant impact on the product quality. Consumers frequently request that certain industries adhere to product quality standards, especially regarding surface texture. Numerous product failures have resulted in dissatisfaction among the company's clientele because many lathe operators are fixated solely on product size drawings and are unaware of factors that can impact the surface roughness value. This investigation was conducted to ascertain how machining parameters affect surface irregularity. Variations in feed rates of 47.5 mm/min and 345.6 mm/min, cutting angles of 60° and 80°, and depths of cut of 1 mm and 3 mm were utilized to conduct the investigation on aluminum alloy 6061 specimens. The results of turning were evaluated for surface roughness using a surface roughness analyzer and a macro test to determine the structure of the surface roughness. Using the Minitab 2019 application, the obtained data was then analyzed to determine the influence of each trimming parameter working individually or simultaneously. Using the method of geometric factorial analysis, integrate the research parameters. The results indicated that the surface roughness increased as the feed rate increased; the lowest surface roughness was achieved with a depth of cut of 1 mm, a feeding rate of 47.5 mm/min, and a cut angle of 80°. In this study, the surface roughness value decreased as the cutting angle increased at lower levels of feeding rate, while the surface roughness value increased at higher levels of feeding rate.

Preparation of Superhydrophobic Coating on X80 Steel and Its Corrosion Resistance in Oilfield Produced Water.

Corrosion is an unavoidable issue that steel encounters during service; however, the generic methods employed for corrosion prevention often need high cost or preparation conditions. In this study, a facile chemical replacement deposition method was proposed to realize an anticorrosion superhydrophobic coating on a X80 steel surface. The growth mechanism of the rough structure and its impact on the wettability of the superhydrophobic coating were analyzed. The superhydrophobic coating, deposited for 50 s and modified for 30 min, achieved optimal electrochemical properties and a maximum water contact angle. The immersion test, in the saturated CO2 oilfield produced water, demonstrated the better corrosion resistance of superhydrophobic coating than X80 steel. Correspondingly, a kinetic corrosion model was established to analyze the anticorrosion mechanism. In summary, this method significantly improves the corrosion resistance of X80 steel and is attractive for other industrial fields.

A synergistic polyelectrolytes-Zr-MOF hydrated construction graphene oxide nanofiltration with enhanced dye wastewater remediation

In recent years, developing an efficient nanofiltration membrane had been a thorny challenge for dye/salt wastewater purification. In this study, a novel graphene oxide-based nanofiltration membrane (GO/UiO@S-GO-8) was constructed by intercalating the synergistic polyelectrolytes-Zr-MOF hydrated construction (UiO@S-GO) into GO nanosheets. Here, combining the hydrophilic high-density anionic sulfonic groups (SO3-) with cationic amino groups (-NH2), GO-based nanofiltration membrane demonstrated outstanding separation ability, anti-pollution performance and structure stability. Compared to pure GO membrane, benefiting by effective expansion of graphene layer spacing from intercalation effect of UiO@S-GO, the water permeance of GO/UiO@S-GO-8 membrane increased to 8 times (about 66.3 ± 1.5 L m−2 h−1 bar−1). Importantly, the permeances of various dyes wastewater also reached up to 65.1 ± 1.8 L m−2 h−1 bar−1 at the high removal rate (exceeding 99.4%). Furthermore, strong hydratability of polyelectrolytes and hard porous crystal constructed the robust anti-fouling micro/nano rough structures onto the membrane surface, which made flux recovery rate (FRR) of GO/UiO@S-GO-8 enhanced to 96.7 ± 1.3%. Remarkably, the salt-resistant behavior of the polyelectrolytes and porous MOF could maintain the stability of the membrane filtration channels, the GO/UiO@S-GO-8 membrane could realize efficient removal rate of dyes (over 98%) faced the complex dye wastewater with different salt concentrations. Meanwhile, the GO/UiO@S-GO-8 membrane also could maintain the high permeance (46.7 ± 1.5 L m−2 h−1 bar−1) as well as excellent removal rate (97.2 ± 1.4%) after 10 cycle experiments. Hence, the GO/UiO@S-GO-8 nanofiltration membrane with Polyelectrolytes-Zr-MOF hydrated construction possessed a broad application inspiration in the purification of high-salt/dye wastewater.

Superhydrophobic finishing of cotton fabric via nonsolvent-induced phase separation of polystyrene–perfluoropolyether block copolymer

This paper reports synthesis of polystyrene–perfluoropolyether block copolymer@cotton fabric (PS–PFPE@CF) with a rough structure through nonsolvent-induced phase separation. The factors affecting the hydrophobicity of the coating, such as solvent quality, the molecular weight of the PS segments, and the volume ratio of tetrahydrofuran/1,3-di(trifluoromethyl)benzene (THF/DTFMB) and THF–MeOH, were all investigated, and the relation between the coating structure and hydrophobicity was also analyzed. In the THF–DTFMB system, PS–PFPE@CF (4 h, 80 mg/mL) appeared as a secondary structure with the superposition of small spheres on large spheres. For this structure, the water-contact angle reached 156.2° ± 0.5° and the sliding angle was 9.5° ± 1.5°. Furthermore, scanning electron microscopy, energy-dispersive X-ray spectroscopy, atomic force microscopy, and thermogravimetric analysis confirmed that PS–PFPE coated the cotton fabric. Finally, application tests were performed to assess the application prospects of PS–PFPE@CF. Oil-water separation, self-cleaning, and antifouling applications were studied, and the experimental results showed that the separation efficiency of the superhydrophobic fabric was nearly constant, from 99.4 % to 98.3 % after 10 oil-water separation tests. PS–PFPE@CF exhibited excellent self-cleaning properties and performed well in the sandpaper abrasion and tape peeling tests. This research thus used a degradable PFPE block copolymer to produce cotton fabrics with excellent hydrophobicity, self-cleaning, and wear resistance.

Statistical simplex centroid experimental design for evaluation of pectin, modified chitosan and modified starch as encapsulating agents on the development of vitamin E-loaded microparticles by spray-drying

Vitamin E encapsulation into biopolymer-based microparticles, obtained by spray-drying technology, was proposed to improve the encapsulation efficiency and the controlled release of fat-soluble vitamin. Binary and ternary blends of pectin, modified chitosan and modified starch, modified starch + modified chitosan, modified starch + pectin, modified chitosan + pectin and modified starch + modified chitosan + pectin ((0.33, 0.33, 0.33), (0.70, 0.15, 0.15), (0.15, 0.70, 0.15) and (0.15, 0.15, 0.70)) were proposed to produce and evaluate different carrier-based delivery systems. Vitamin E-loaded microparticles and empty microparticles were created with a product yield between 9 and 49 %. The mean diameter among all microparticles varied between 3.74 ± 0.02 and 421 ± 21 μm (differential volume distribution). Oval, spherical or irregular microparticles, with a variable morphology from a smooth to a high rough surface structure, with concavities, were produced. All vitamin E-loaded microparticles exhibited an encapsulation efficiency higher than 70 %. The slower vitamin E controlled release was observed from microparticles composed by modified chitosan (>36 h), while the faster release was achieved from microparticles individually composed by pectin (39 min). In general, the Fickian diffusion is the main release mechanism involved in the microparticles produced with modified chitosan, other formulations combine also other mechanisms such as swelling.

Degradation induced superlubricity on the rough surface of black phosphorus composite

A rough surface composed of asperities was considered as the obstacle for achieving superlubricity in traditional friction theory. Here, microscale superlubricity with the friction coefficient of 0.0086 was observed on a relatively rougher soft surface of black phosphorus (BP) composite due to the degradation of BP with oxygen and moisture via the atomic force microscopy (AFM) experiment equipped with diamond-like carbon (DLC) microsphere probe. Comparative analyses corroborated that the produced phosphorus oxides (oBP) with abundant P=O and P−OH bonds and the local graphitized amorphous carbon film at the sliding interface decreased the possibility of direct contact between original rough peaks and provided an ultra-low shear strength for achieving superlubricity. Furthermore, a certain nanoscale roughness structure on the composite surface facilitated a more reliable superlubricity state, which supplied the larger contact area and locking capillary force to hold and retain the lubricating liquid film formed by the water absorption of oBP. These findings provided fundamental insights into the nature of tribological mechanisms and suggested a new method to achieve ultra-low friction of polymer composite materials in engineering.

The Multiscale Structural Properties and In‐Vitro Digestibility of High Amylose Corn Starch During Autoclaving‐Cooling Treatment

AbstractThis work investigates the relationship between multiscale structural properties in high amylose corn starch (HACS) and its in‐vitro digestibility by analyzing the effects of autoclaving‐cooling treatment (ACT). Differential scanning calorimetry (DSC) shows that HACS displays a higher gelatinization temperature, wider endothermic gelatinization range, and higher enthalpy. Autoclaved corn starch exhibits enhanced thermal stability than the raw corn starch. X‐ray diffraction (XRD) shows that ACT does not change the crystalline type but increases the relative crystallinity (RC). Fourier transform infrared spectroscopy (FTIR) indicates that HACS exhibits a higher degree of order (DO) and double helixes (DHs) than normal corn starch (NCS), which are reduced by ACT. Scanning electron microscopy (SEM) reveals that HACS displays denser structures and smaller particle morphologies than NCS. After ACT, the granular of autoclaved corn starch shows a rough fiber network structure. Digestibility analysis reveals a positive correlation between the amylose content and resistant starch (RS) level in raw starch, while ACT promotes significant RS formation. This suggests that amylose promotes ordered structure formation, while autoclaving increased digestive resistance.

Surfaces of coastal biogenic structures: exploiting advanced digital design and fabrication strategies for the manufacturing of oyster reef and mussel bed surrogates

Coastal biogenic structures, formed by ecosystem engineering species, often feature rough surfaces characterized by intricate topographies and highly three-dimensional reliefs. Their surfaces are shaped by waves and tidal currents and reciprocally influence the ambient hydrodynamics, reflecting an equilibrium. Despite their significance, the impact of these surfaces on the ambient hydrodynamics remains underexplored due to limited knowledge of accurately replicating their complex topographies in experimental setups. The recent advent of advanced digital manufacturing presents an efficient means to manufacture highly complex, three-dimensional surrogate models for experimental modeling. This work explores the accurate replication of rough coastal biogenic structures for experimental modeling on the examples of an oyster reef and a mussel bed, utilizing a flexible design methodology and, for the first time, particle bed 3D printing with Selective Cement Activation (SCA) as a fabrication and manufacturing method. A workflow is proposed, which includes an iterative surrogate model development based on in-situ topographical features, requirements of the experimental setup, and parameters of the particle bed 3D printer with SCA. The results demonstrate the effectiveness of the methodology in achieving highly accurate surrogate surfaces of complex coastal biogenic structures by validation against a set of topographical features relevant to hydraulic roughness. Particle bed 3D printing with SCA proved to be a suitable method to manufacture complex surrogate surfaces for experimental modeling, offering advantages such as independence of production time from surface complexity. However, challenges persist in achieving exact comparability between the manufactured surrogate surface and the real coastal biogenic structures, particularly for surfaces with very high complexity. Nonetheless, the manufactured generic surrogate surfaces enable detailed investigations into the influence of complex coastal biogenic structures on the ambient hydrodynamics, thereby enhancing the understanding of the processes governing wave energy dissipation attenuation, turbulence production, and vertical mixing – critical for efficient application as a nature-based solution on coastal protection or restoration efforts.

A novel P/Fe/Si-doped porphyrin with excellent flame retardancy and ultrastrong toughening effect on epoxy resin

Epoxy resin (EP) is one of the most versatile polymers. Nonetheless, its inherent flammability and brittleness severely limit its broad development. Moreover, existing additives make it difficult to meet the dual requirements of flame retardancy and toughening. Herein, a novel P/Fe/Si-doped porphyrin derivative (MTPD-Fe@SiO2) with nano-cauliflower structure was synthesized to develop advanced EP composites. MTPD-Fe@SiO2 exhibited good dispersion in EP matrix, which is attributed to the π-π interactions between the porphyrin and EP chains, as well as the mechanical interlocking of nano-cauliflower rough structure. Moreover, when 5 % of MTPD-Fe@SiO2 was incorporated, the tensile and flexural strengths of EP composites were increased by 48.1 % and 63.5 %, respectively, showing excellent toughening properties. Additionally, the maximum thermal degradation rate of EP/5 % MTPD-Fe@SiO2 was significantly reduced, indicating its superior thermal stability. Notably, compared with pure EP, the peak heat release rate and the peak smoke production rate of EP/5 % MTPD-Fe@SiO2 were decreased by 36.4 % and 43.6 %, while the residual char and limiting oxygen index increased to 30.9 % and 32.1 %, respectively. This was ascribed to the catalytic charring of transition metals and phosphates, the barrier effect of the solid carbon layer (Fe4(PO4)2O, SiO2), the trapping effect of phosphorus radicals and the dilution effect of incombustibles. This work provides a viable approach to solving the trade-off between refractoriness and mechanical performance.

Preparation of Durable Superhydrophobic Coatings Based on Discrete Adhesives

Due to the low adhesion observed at the interface between solid and liquid, superhydrophobic coatings hold significant promise for various applications, such as self-cleaning, anti-corrosion, anti-icing, and drag reduction. However, a notable challenge hindering their widespread adoption in these domains lies in their delicate durability. In this study, we propose a straightforward method for preparation. The fluorosilicone resin is initially discretized through a gradual introduction of nonsolvent into its solution, followed by thorough mixing and stirring with silica nanoparticles. The resulting mixture is then sprayed onto the substrate surface after drying, forming a self-similar, porous, and rough structure extending from top to bottom. This process yields a coating exhibiting excellent chemical and mechanical durability simultaneously. Using this approach, we achieved a superhydrophobic coating with a contact angle of 156° and a roll angle of 2.2°, with water droplet adhesion of only 10.8 ± 0.4 µN. Remarkably, the coating maintained excellent superhydrophobicity even after undergoing sandpaper abrasion (10 m), tape peeling (30 times), and prolonged water impact (60 min), showing its robust mechanical stability. Furthermore, following exposure to acid, alkali, and aqueous solutions (7 days), UV irradiation (10 days), and extreme temperature variations (–20 °C to 80 °C), the coatings retained their superhydrophobic properties and exhibited good chemical durability. This method offers a novel approach to enhance the durability and practicality of superhydrophobic coatings.

Occurrence and Distribution of Plastispheres in Coastal Sediments and Waters along the Maharashtra Coast, India

Microplastics can promote microbial colonisation and biofilm growth, thus being referred to as “plastispheres”. The global plastic pollution surge is likely to adversely impact ecology and human health by providing a novel habitat for microbial communities. Even though microplastics in marine environments have been the subject of in-depth research, plastispheres have recently received attention. Thus, the current study investigates the prevalence and distribution of plastispheres along the Maharashtra coast of India, considering their plausible implications for ecology and human health. Microplastics were isolated from sediment and water samples obtained from 10 sampling sites. Subsequently, these microplastic particles were subjected to ATR-FTIR and scanning electron microscopy (SEM) analyses to ascertain their chemical composition, surface topography, and presence of attached biofilms. The predominant polymers composing the microplastic particles were polypropylene (42.8%), polyethylene (28.6%), polystyrene (14.3%), and polyvinyl chloride (14.3%). SEM analysis revealed the presence of topographical structures and degradation effects, facilitating microbial attachment on the microplastic surface. About 50% of the microplastic particles tested positive for biofilms, with over 66% of those collected from Girgaon and Malvan beaches exhibiting biofilm presence. These positively screened particles also displayed comparatively rough surface structures, likely enhancing microbial colonisation. Microplastic ageing and polymer type could positively affect microbial colonisation. Diatoms and fungal hyphae exhibit varied interactions with microplastic polymers. Notably, microplastics host various reproductive stages of fungi, as evidenced by filamentous networks, mycelia, and conidiophores.

Secondary roughness effect of surface microstructures on secondary electron emission and multipactor threshold for PTFE-filled and PI-filled single ridge waveguides

Secondary electron yield (SEY) is a dominant factor in determining the multipactor threshold. In this study, we analyzed the secondary roughness effect of surface microstructures for plastic dielectric on SEY reduction and multipactor mitigation. A single ridge waveguide (SRW) operating in Ku-band, filled with polytetrafluoroethylene (PTFE) or polyimide (PI), was designed with a dielectric–metal multipactor gap. By employing a femtosecond laser, periodic microstructures were fabricated on PTFE and PI surfaces to suppress SEY. The SEY peak values of PTFE and PI decreased from 2.05 to 1.40 and 1.37 to 1.07 by the porous surface. The surface morphologies and cross-sectional images of the porous PTFE and PI demonstrated the existence of secondary roughness structures. Via simulation, we obtained multipactor thresholds of 8496 W, 12 374 W, and 9397 W for the SRWs filled with untreated PTFE surface, ideal porous surface (without secondary roughness), and real porous surface (with secondary roughness). Similar works were implemented for the PI-filled SRWs, resulting in simulated multipactor thresholds of 7640 W, 11 327 W, and 9433 W. The results indicate that the multipactor effect may not be effectively suppressed under the influence of secondary roughness structures such as plastic velvet and foam. Besides, simulation works indicated that the radio frequency electric field could extract secondary electrons from the microstructures, weakening the mitigation effect of microstructures on multipactor. The impact of surface charging on electron motion was also analyzed by considering energy distribution. It was suggested that the surface microstructures of plastic dielectrics lead to a decrease in the surface charge density and the electrostatic field strength, weakening the self-extinguishing effect and lowering the multipactor threshold. This study provides an in-depth analysis of the effect of secondary roughness on SEY and multipactor for organic dielectrics, which makes significant sense for the further investigation of dielectric multipactor.

Origin of surface oxidation induced the nucleation and propagation of microcracks in TNM alloy

This study investigated the impact of surface degradation caused by oxygen (O) and nitrogen (N) elements in the environmental atmosphere on the service failure of nearly lamellar TNM alloy. The results show that oxidation-induced phase transformations at the surface and subsurface regions strongly affect the alloy's tensile properties at high temperatures. The precipitation of Al2O3, which disrupts the integrity of the Ti2AlN layer, has a weaker deformation resistance capacity compared to the Z-phase. Under stress conditions, numerous dislocations concentrate at the Al2O3 phase, causing Al2O3 particles to easily detach and initiating crack nucleation at the Z-phase/Al2O3 interface. This is the origin of oxidation failure. Cracks nucleate at the Al2O3 detachment region, propagate, and connect with surface microcracks induced by the rough and loose outer oxide layer structure. This leads to the rapid propagation of cracks into the subsurface. The consumption of β-stabilizing elements at the surface, along with the internal diffusion of O and N elements into the subsurface region, results in the formation of the hard brittle Z-phase at the subsurface lamellar structure and a transition from β0 to α2 at the lamellar colony boundaries. The precipitation of α2 and Z-phase also accelerates crack propagation. In summary, the failure mode shifts from toughness fracture to brittle fracture.

Hydrophobic modification of walnut shell biomass-derived porous carbon for the adsorption of VOCs at high humidity

Volatile organic compounds (VOCs) often contain water vapor in their exhaust emissions, resulting in the deterioration of the adsorption capacity of activated carbon (AC). A hydrophobic walnut shell biomass-derived AC using polytetrafluoroethylene (PTFE) and polydimethylsiloxane-coated SiO2 (PDMS/SiO2) was developed to improve the selectivity of VOCs under high humidity conditions. These modified ACs were systematically characterized, and dynamic adsorption behaviors of VOCs such as toluene, acetone and their mixtures at the relative humidity (RH) between 0 and 90 % were conducted. The results showed that walnut shell biomass-derived AC has large specific surface area (1853 m2/g) and total pore volume (1.27 cm3/g), strong hydrophilicity (water contact angle of 6.3°), abundant oxygen-containing groups (OH, CO, CO) and aromatic rings. The coating of PDMS/SiO2-PTFE reduces the surface area and total pore volume of AC, but it creates a double-layer rough structure on the AC surface and introduces CF and SiOSi hydrophobic groups, which achieves a water contact angle of 152.8° for 25PSP/AC. The Yoon-Nelson model is suitable to describe the dynamic adsorption process of single- toluene or acetone under dry/humid condition but not suitable for their mixtures. At RH 90 %, PDMS/SiO2-PTFE modified AC significantly increases the adsorption capacity of toluene but is not obviously improved for acetone, which is due to the different polarity of toluene and acetone. PDMS/SiO2-PTFE films on AC have good thermal stability before 500 °C and the hydrophobicity does not change after multi-regeneration at 200 °C. Therefore, PDMS/SiO2-PTFE modified AC has shown great potential as adsorbent to remove the toluene from the humid condition.