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In this paper, hydrophobic treatment by hexadecetyltrimethoxysilane (HDTMS) on the surface of Sn–Ti submicrospheres with regular morphology and uniform size prepared via a simple PVP-assisted sol-gel method was firstly reported. Their physical and chemical properties were characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), N2 adsorption-desorption isotherms, Fourier transform infrared spectroscopy (FI-IR), Uvioletvisible diffuse reflection spectroscopy (UV-vis DRS), Water contact angle (WCA), Thermogravimetric analysis (TG), Inductively coupled plasma-Atomic emission spectrometry (ICP-AES), C elemental analysis and Transmission electron microscope (TEM) techniques, and the catalytic performance in the Baeyer-Villiger (B-V) oxidation of cyclohexanone in the oxygen-benzaldehyde system was also investigated. The regular submicrospheres with anatase crystal phase can be kept well by the successful grafted hydrophobic layer. When the weight ratio of HDTMS to 12%-ST submicrospheres was 1, the maximum hydrophobic angle of 126.0º for 12%-1-C16-ST catalyst can be obtained. The cyclohexanone conversion and caprolactone yield over the 12%-1-C16-ST catalyst was highest, whose value was 2.32 and 3.44 times, respectively, than that of 12%-ST without hydrophobic treatment. The 12%-1-C16-ST catalyst also showed good stability with only a 3.74% drop of caprolactone yield after repeated use for 5 times. This method can provide a valuable reference and potential catalyst for the industrial application in the production of caprolactone. [ABSTRACT FROM AUTHOR]

Polyphenylene sulfide (PPS), a thermoplastic polymer with excellent chemical and thermal stability, has properties similar to those of polytetrafluoroethylene (PTFE) but is less expensive. In this study, the feasibility of using PPS to replace conventional PTFE as a hydrophobic agent for microporous layers (MPLs) in proton exchange membrane fuel cells (PEMFCs) is explored. First, PTFE-MPL and PPS-MPL with 30 wt% hydrophobic agent were prepared. The pore size, porosity, contact angle, and microstructure of the two MPL samples were measured and analyzed. Subsequently, PEMFCs with the two MPL samples were tested for their operational performance at a conventional temperature of 70 °C and cold-start capability at −10 °C. The performances of PTFE-MPL and PPS-MPL at conventional temperatures were similar, but PPS-MPL showed obvious advantages in cold-start performance. In addition, the operating performance of PEMFC at the conventional temperature and cold-start capability at −10 °C were investigated for PPS mass fractions of 10%, 20%, and 30% in MPL, and for PPS particle sizes of 10 and 30 μm. The results indicate that the optimal performance can be attained when the PPS particle size is 10 μm and the mass fraction is 20%. • The properties of PPS are similar to PTFE, but the price is only 1/2–1/3. • Using PPS instead of conventional PTFE as hydrophobic agent for MPL. • The PPS-MPL is not inferior to conventional PTFE-MPL at conventional temperatures. • The PPS-MPL shows better cold start performance than PTFE-MPL. • The effect of hydrophobic agent content and particle size in PPS-MPL was investigated. [ABSTRACT FROM AUTHOR]

Cellulose nanofibers (CNFs) are environmentally friendly materials with a high specific strength. To enhance the impact properties of the carbon fiber reinforced plastics (CFRPs), a method for inserting a CNF dispersion layer between prepregs was developed. By using an aqueous solution of epoxy resin, the hydrophobic treatment of CNF became unnecessary. In this study, CFRP with CNF dispersion layers was fabricated with different CNF content. The impact energy absorbed by the CFRP specimen was increased with the increasing CNF content, and the Charpy impact value increased up to a maximum of 21% by the CNF dispersion layers. Carbon fiber reinforced plastics (CFRPs) specimens with the cellulose nanofiber (CNF) dispersion layer were fabricated. The specimens were fabricated by varying the content of CNF. Impact energy absorbed by the CFRP specimen was increased with increased CNF content. Charpy impact value increased up to 21%; optimum ductility index value was clarified. [ABSTRACT FROM AUTHOR]

An efficient method to increase specific strength of carbon fiber reinforced plastics (CFRP) by using cellulose nanofibers (CNFs) was developed. Eliminating a complex hydrophobic treatment of CNF by using aqueous electrodeposition solution (EDS) containing a polymer with epoxy group, the CFRP with CNF/resin layer was fabricated. The effects of the CNF/resin layer on the bending properties of CFRP were clarified by varying the weight fractions of CNF. The specific flexural rigidity and strength of the CFRP with CNF/resin layer were increased to approximately 3.5 times and 1.8 times those of the CFRP without CNF/resin layer, respectively. [ABSTRACT FROM AUTHOR]

Fiber reinforcement in SHCCs causes the formation of many fine cracks under imposed strain. In this way, ductility is increased, but water and chloride may still quickly penetrate deep into microcracks by capillary action. As a consequence, corrosion of steel rebars can be initiated at early stage. In this contribution, multiple cracked steel reinforced SHCC specimens with and without hydrophobic surface impregnation were prepared. The corrosion of the rebars in multi-cracked SHCCs was monitored and it can be concluded that multiple cracked SHCCs with fine small cracks exhibit a higher corrosion resistance to steer reinforcement than fractured ordinary mortar. The corrosion of steel reinforcement initiates from the bottom interface between the rebar and matrix. Steel reinforcement corrosion can be reduced remarkably through hydrophobic surface impregnation, even in the cracked state. In this way, the working life of steel strengthened SHCC elements exposed to erosive environments could be substantially prolonged. [ABSTRACT FROM AUTHOR]

As naturally derived material, cellulose aerogels have excellent thermal insulation properties due to their unique high porosity and three-dimensional mesoporous structure. However, its hydrophilic properties limit its application in the field of building insulation. Here, we propose a method to prepare high hydrophobicity by adopting the sol-gel method and chemical vapor reaction strategy using cellulose acetate type II as raw material and 2,4-toluene diisocyanate as the cross-linking agent. Thermal properties of cellulose acetate aerogels (CAAs) were measured, where pyridine was the catalyst, acetone was the solvent, and perfluorodecyltriethoxysilane (PFDS), hexamethyldisilazane (HMDS), and methyltriethoxysilane (MTES) were used as hydrophobic agents (by process hydrophobic test). Compared with MTES-modified cellulose acetate aerogels (M-CAAs) and HMDS (H-CAAs)-modified cellulose acetate aerogels, PFDS-modified (P-CAAs) cellulose acetate aerogels are the most hydrophobic. By implementing hydrophobic modification of PFDS both inside and outside the structure of cellulose acetate aerogels, the water contact angle can reach up to 136°, strongly demonstrating the potential of PFDS as a hydrophobic agent. The results show that the thermal conductivity and compressive strength of cellulose acetate aerogel with the best hydrophobic properties are 0.035 W m−1 K−1 at normal pressure and 0.39 MPa at 3% strain, respectively. This work shows that the highly hydrophobic cellulose acetate aerogel has potential as a waterproof material in the field of building thermal-insulation materials. [ABSTRACT FROM AUTHOR]

The present study mainly studies the effect of polydimethylsiloxane (PDMS) content on the waterproofing and mechanical properties of geopolymer composites. Firstly, hydrophobic modified geopolymer composites (HM-GC) were prepared by adding PDMS during the mixing process. Secondly, the surface wettability characteristics, water absorption, uniaxial compressive and tensile properties of HM-GC were investigated. The effect of PDMS content on the waterproofing and mechanical properties was further discussed. Finally, considering the waterproofing and mechanical properties, the optimal PDMS content was proposed. The results showed that with increasing PDMS content, the contact angle of geopolymer composites rapidly increase at first and then stabilizes. The geopolymer composites with 4% and 5% PDMS content exhibit overhydrophobic surface wettability. In addition, the water absorption gradually decreases with increasing PDMS content, indicating an improvement in the waterproofing ability. The incorporation of PDMS can enhance the compressive properties of geopolymer composites while reducing the tensile properties. Comprehensively considering the waterproofing and mechanical properties, it is reasonable to select 4% as the optimal PDMS content used in practical marine engineering. • Hydrophobic modified geopolymer composites were prepared by adding a modifier. • The variations in the waterproofing and mechanical properties were discussed. • An overhydrophobic surface wettability was achieved in geopolymer composites. • The compressive property was enhanced while the tensile property was decreased. [ABSTRACT FROM AUTHOR]

Use of hydrophobic treatments according to the TR Instandhaltung of the DIBt – Procedure from the planner's perspective and practical example According to the Technische Regel Instandhaltung (TR IH) (engl.:Technical Rule on Maintenance) of the Deutsches Institut für Bautechnik (DIBt) [1] in contrast to Part 1 of the Instandsetzungsrichtlinie (Rili SIB) of the DAfStB [2], the use of hydrophobic treatments or OS 1 systems is also possible to protect against the penetration of substances, to regulate the water balance of concrete and to increase the electrolytic resistance of concrete (in the case of carbonation‐induced reinforcement corrosion). This article gives an overview of the product groups of silane‐ or siloxane‐based water repellents available on the market. Since the planner must specify application quantities and penetration depths according to TR IH, the procedure for determining minimum application quantities and minimum penetration depths is outlined. Corresponding laboratory tests for determining the minimum values are presented. Furthermore, advice is given on planning and quality assurance during construction. Since, according to TR IH, the effect of a hydrophobic treatment that may diminish during use must be taken into account in the maintenance plan by means of control measurements. Various possibilities are then explained with which such a proof of effect is possible. Finally, a practical example is presented. [ABSTRACT FROM AUTHOR]

Water repellent treatment is one of the effective means to improve the durability of concrete. This paper aims to investigate the water repellency of cement-based materials treated with silane-based water repellent agent under different exposure environments. Five different exposure conditions were applied in this experiment, namely, standard moist curing room, in-door laboratory atmosphere, pre-oven-dried condition, and out-door natural environment with or without shelter. Three different types of mortars with water-to-cement ratios of 0.4, 0.5 and 0.6 were prepared. And three different dosages (200, 400, 600 g/m2) of silane gel were utilized on the surface of specimens. The impregnation depth and water absorption after hydrophobic treatment have been measured. Results indicate that the initial moisture condition of mortar has a significant influence on the efficiency of surface silane impregnation. The depth of silane impregnation gradually decreases with the increase of initial moisture condition. The water repellency of surface impregnation of cement-based materials was well exhibited under the condition of about 50% relative humidity. It illustrated that the moisture within the cement-based materials affects the hydrolysis reaction process and the formation of hydrophobic membrane. Thus, the water repellency of cement-based materials greatly depends on the initial moisture content and the thickness of hydrophobic layer.

Additive manufacturing (AM) is a free-form technology that shows great potential in the integrated creation of three-dimensional (3D) electronics. However, the fabrication of 3D conformal circuits that fulfill the requirements of high service temperature, high conductivity and high resolution remains a challenge. In this paper, a hybrid AM method combining the fused deposition modeling (FDM) and hydrophobic treatment assisted laser activation metallization (LAM) was proposed for manufacturing the polyetheretherketone (PEEK)-based 3D electronics, by which the conformal copper patterns were deposited on the 3D-printed PEEK parts, and the adhesion between them reached the 5B high level. Moreover, the 3D components could support the thermal cycling test from −55 °C to 125 °C for more than 100 cycles. Particularly, the application of a hydrophobic coating on the FDM-printed PEEK before LAM can promote an ideal catalytic selectivity on its surface, not affected by the inevitable printing borders and pores in the FDM-printed parts, then making the resolution of the electroless plated copper lines improved significantly. In consequence, Cu lines with width and spacing of only 60 µ m and 100 µ m were obtained on both as-printed and after-polished PEEK substrates. Finally, the potential of this technique to fabricate 3D conformal electronics was demonstrated.

As naturally derived material, cellulose aerogels have excellent thermal insulation properties due to their unique high porosity and three-dimensional mesoporous structure. However, its hydrophilic properties limit its application in the field of building insulation. Here, we propose a method to prepare high hydrophobicity by adopting the sol-gel method and chemical vapor reaction strategy using cellulose acetate type II as raw material and 2,4-toluene diisocyanate as the cross-linking agent. Thermal properties of cellulose acetate aerogels (CAAs) were measured, where pyridine was the catalyst, acetone was the solvent, and perfluorodecyltriethoxysilane (PFDS), hexamethyldisilazane (HMDS), and methyltriethoxysilane (MTES) were used as hydrophobic agents (by process hydrophobic test). Compared with MTES-modified cellulose acetate aerogels (M-CAAs) and HMDS (H-CAAs)-modified cellulose acetate aerogels, PFDS-modified (P-CAAs) cellulose acetate aerogels are the most hydrophobic. By implementing hydrophobic modification of PFDS both inside and outside the structure of cellulose acetate aerogels, the water contact angle can reach up to 136°, strongly demonstrating the potential of PFDS as a hydrophobic agent. The results show that the thermal conductivity and compressive strength of cellulose acetate aerogel with the best hydrophobic properties are 0.035 W m−1 K−1 at normal pressure and 0.39 MPa at 3% strain, respectively. This work shows that the highly hydrophobic cellulose acetate aerogel has potential as a waterproof material in the field of building thermal-insulation materials.

The authors have studied water-repellency technology using a roughness structure fabricated by electroplating. This paper examined the relationship between surface morphology and water-repellency of two-layered nickel structures obtained by changing the electroplating parameters using a simple nickel chloride-based electroplating bath. As a result, it was confirmed that the surface morphology of the deposit could be transformed by electroplating the second layer at a bath temperature different from that of the first layer. The contact angle in two-layered roughness plating also tended to be higher under conditions of greater Sdq value (root mean square slope). In particular, both the Sdq value and contact angle were high for the second-layer deposited at a bath temperature of 80°C and applied electrical-quantity of 1500 C dm−2 or more. In this study, a relatively high relationship between Sdq value and contact angle was observed, and it was found that changing each layer's electroplating conditions can control the water-repellency. [ABSTRACT FROM AUTHOR]

Water management of proton exchange membrane fuel cells remains a prominent issue in research concerning fuel cells. In this study, the gas diffusion layer (GDL) of a fuel cell is partially treated with a hydrophobic agent, and the effect of GDL hydrophobicity on the water distribution in the fuel cell is examined. First, the effect of the position of the cathode GDL hydrophobic area relative to the channel on the fuel cell performance is investigated. Then, the water distribution in the fuel cell cathode GDL is observed using X-ray imaging. The experimental results indicate that when the hybrid GDL's hydrophobic area lies on the channel, water tends to accumulate under the rib, and the water content in the channel is low; this improves the fuel cell performance. When the hydrophobic area is under the rib, the water distribution is more uniform, but the performance deteriorates. • Performance enhancement of proton exchange membrane fuel cells was examined. • Gas diffusion layer was partially treated with a hydrophobic agent. • Effect of gas diffusion layer hydrophobicity on water distribution was studied. • Water distribution in fuel cell cathode gas diffusion layer studied by X-ray imaging. [ABSTRACT FROM AUTHOR]

In order to study the salt-frost resistance of hydrophobic treatment on hydraulic concrete, specimens were fabricated and treated with two repellent agents of organosilicon and silane. Then, concrete contact angles and water absorption rates were measured. In addition, mass loss ratios and relative dynamic modulus of elasticity (RDME) of concrete during saline freeze-thaw cycle were tested periodically. The results show that the hydrophobic treatment can substantially improve the hydrophobicity of hydraulic concrete, greatly reduce its water absorption with an average improvement ratio of 70%, and simultaneously improve the resistance of hydraulic concrete against salt scaling and RDME losses to a certain degree, which can delay and alleviate the salt-frost on hydraulic concrete. Corresponding 200 cycles of freezing and thawing in salt solution, the hydrophobic treatments averagely reduce the mass loss and RDME loss of concrete by 64.4% and 51.2%, respectively. However, it should be noted that the hydrophobic layer formed by repellent agents on the superficial concrete will be destroyed gradually with saline freezing-thawing cycle. As a result it will cause the improvement effects of hydrophobic treatment on hydraulic concrete salt-frost resistance gradually lost. [ABSTRACT FROM AUTHOR]

This article is aimed at investigating the long‐term performance of three original hydrophobic materials, namely, sodium acetate, fluoropolymer, and silicone resin. Their performance was compared with traditional silane when applied to fully dry concrete, fully saturated concrete, and concrete with 2 and 4% moisture content. A recently developed freeze–thaw process, which is based on temperature and humidity variations, was employed in this study to assess the durability of applied materials. The outcomes of the adopted freeze–thaw system were compared with the results obtained from running a conventional freeze–thaw test. Mass change, water absorption, and microcracks development of treated concrete were investigated and compared with untreated concrete after completing 6 months of freeze–thaw cycles. Results confirmed the high affinity of the proposed materials to moisture at application time compared with silane. Additionally, it was demonstrated that moisture content has a critical impact on the bonding between applied materials and concrete, hence their efficacy in enhancing the durability of concrete. [ABSTRACT FROM AUTHOR]

Despite excellent service history, concrete pavement faces accelerated deterioration due to water and chemical ingress through micro cracks and surface voids. Surface protection could be an inexpensive way of enhancing the durability of concrete pavement. This research focuses on evaluating the performance of three surface applied hydrophobic materials with different chemistries; fluoropolymer, silicate resin and sodium acetate crystallising material. Tests consisted of a microscopic study to assess the mechanism of treatment, contact angle and pendulum tests to evaluate the hydrophobicity and frictional properties of treatment respectively. Also, surface absorption and water intake tests were conducted to appraise the resistance of treatment to absorb water. It was found that all three materials are capable of developing a hydrophobic effect in concrete, but with different efficacy in reducing water absorption. The rate of water absorption was minimum for sodium acetate compared to fluoropolymer and silicate resin treatments. Scanning Electron Microscope (SEM) analysis revealed different interaction approaches for the three materials with concrete. [ABSTRACT FROM AUTHOR]

In this paper, a novel PVA-based polymer nanoparticles/carbon nanotubes (PNP/CNTs) aerogel was successfully developed. Firstly, certain amount water-dispersed carbon nanotubes were introduced into PVA solution and undergo hydrothermal process in the presence of ferric iron to obtain novel PNP/CNTs solution. Then, the PNP/CNTs aerogels were fabricated by the "freeze-thaw" cycle and freeze-drying methods, followed by the vapor deposition of trimethylchlorosilane to obtain hydrophobic aerogel. The morphology and structure of polymer nanoparticles were characterized by SEM, TEM, FT-IR, Raman, UV–vis and XRD. The density, structure and thermal stability of PNP/CNTs aerogel were also investigated. The compressive performance of PNP/CNTs aerogels were better than PVA aerogel and showed small difference before and after hydrophobic treatment. In addition, the adsorption measurements of different aerogels were also studied. The results showed that hydrophobic PNP/CNTs-6 aerogel exhibited better adsorption capacities and reusability than others. These outstanding properties can make PNP/CNTs aerogels considered as a promising candidate to remove organic solvents from aqueous solution. [ABSTRACT FROM AUTHOR]

The impregnation of the exterior surface of a masonry wall with a water repellent is a common intervention in (historic) building renovation and maintenance. Such treatments, whilst degrading at the surface with time under influence of ultra violet light, remain effective below the surface several decades after their application. During renovation works of masonry previously treated with a water repellent, the question arises whether it is necessary to repeat the hydrophobic treatment of the entire masonry after repointing. Opposing opinions exist with this regard, but no research clearly supporting one or the other. This research investigates for the first time the effect of hydrophobic treatment when applied on previously treated and repointed masonry walls. Small masonry walls were subjected to rain periods in the laboratory and their water uptake and drying behaviour were studied. Moreover, this laboratory research was followed by 30 months of outdoor exposition of the masonry specimens. The following cases were considered: (1) wall treated with water repellent, (2) wall treated with water repellent, followed by repointing but without new water repellent treatment, (3) wall treated with water repellent, followed by repointing and retreatment. This was done for three different types of pointing mortar: ordinary Portland cement and natural hydraulic lime with standard sand, and natural hydraulic lime with sand with one grain size. The results show that, after prolonged rain periods, the water uptake by repointed but not retreated masonry is comparable to that of untreated, non-hydrophobic masonry, whereas drying is considerably slower. This leads to a high saturation degree in repointed but not retreated masonry, which, in turn, increases the risk of damage to the masonry by e.g. frost. Therefore, retreating repointed hydrophobic masonry should definitively be considered. • A rain test was performed in laboratory. • Repointed but not retreated masonry, and untreated masonry had similar water uptake. • Repointed but not retreated masonry dried much slower than untreated masonry. • A high saturation degree was measured in repointed but not retreated masonry. • Retreatment of repointed hydrophobic masonry reduces potential risk of damage. [ABSTRACT FROM AUTHOR]

CO 2 hydrogenation to methanol is an efficient way to utilize CO 2 and store hydrogen. However, realizing high activity and methanol selectivity as well as excellent stability are still challenges due to the competitive reverse water-gas shift (RWGS) reaction and the accumulation of water on the catalyst surface. Herein, Cu/ZnO catalyst was prepared by oxalic acid-assisted solid-state grinding method and then was subjected to hydrophobic treatment using stearic acid as a functionalization agent. The effect of stearic acid concentration on the physicochemical properties of Cu/ZnO catalysts and the catalytic activity for low-temperature CO 2 hydrogenation to methanol was investigated and discussed in detail. Detailed catalyst characterizations disclosed that hydrophobic treatment using suitable concentration of stearic acid removed residues from the decomposition of oxalic acid and also increased specific surface area, surface basicity, reducibility and hydrogen adsorption strength on Cu/ZnO catalysts, leading to the enhanced catalytic performance and methanol selectivity. Among all the catalysts, Cu/Zn-2 mM catalyst exhibited methanol selectivity and methanol space time yield (STY) of 78.8% and 87.17 g/kg·h−1 at 200 ℃, much higher than those of untreated Cu/ZnO catalyst (71.7% and 68.93 g/kg·h−1). The hydrophobic Cu/Zn-2 mM catalyst also exhibited outstanding stability for low-temperature CO 2 hydrogenation to methanol, keeping its activity for 100 h without obvious deactivation when compared to untreated Cu/ZnO catalyst. This facile hydrophobic treatment using stearic acid not also enhanced catalytic activity, methanol selectivity and stability of Cu/ZnO catalysts for low-temperature methanol synthesis, but also enlightened the invention of more hydrophobic materials in the near future. [Display omitted] • Hydrophobic Cu/ZnO catalyst was successfully prepared using stearic acid. • The effect of stearic acid concentration was disclosed. • Hydrophobic treatment enhanced catalytic performance and methanol selectivity. • The hydrophobic Cu/Zn-2 mM catalyst kept its activity for 100 h without deactivation. [ABSTRACT FROM AUTHOR]

Abstract Biorelevant dissolution is an indispensable tool utilized during formulation development and optimization for the prediction of in vivo bioavailability of pharmaceutical agents. Within that framework, membrane-permeation dissolution methodologies are widely used to model drug absorption. The current work evaluates polymer membrane surface modifications for production of biomimetic membranes to be employed in biorelevant dissolution studies. Biomimetic membranes exhibit hydrophilic and hydrophobic properties to simulate the intestinal membrane environment. Low temperature plasma treatment of microporous polyethersulfone (PES), nylon and polypropylene (PP) polymer membranes was applied to produce low energy surface layers with permanent hydrophobic and hydrophilic functionalities. Surface modifications on microporous polymer membranes were achieved by plasma treatments using tetrafluoromethane (CF4), perfluorohexane (C6F14), dichloromethane (DCM) and water (H2O). Surface characterization of treated membranes was evaluated using scanning electron microscopy energy dispersive x-ray spectroscopy (SEM-EDS), water contact angle (CA) and x-ray photoelectron spectroscopy (XPS) techniques. SEM-EDS analysis of polymer membranes treated with fluorinated and chlorinated solvents/gases depicts altered surface morphologies with enriched porosity. SEM-EDS and XPS analyses demonstrate the chemical modification at the surface of treated membranes is strongly influenced by the type of treatment gas or solvent. Results show fluorination as a more effective and less destructive treatment technique. XPS confirmed the presence of elemental fluorine functional groups at the surface of the PES and nylon membranes. Evaluating elemental changes (F/C ratio) from multiple techniques confirms fluorinated plasma treatments are localized to the surface of the membrane and do not significantly affect the bulk properties. In a supplemental study, a detailed comparison of the plasma treated polymer membranes and porcine intestines revealed the biomimetic nature of the modified membranes.

Wood that is used in outdoor applications is frequently exposed to weathering and is thus prone to fungal degradation. Ways to prevent fungal degradation include keeping the wood dry. The majority of hydrophobic and wood modification systems have been tested only on freshly treated wood. Little information is available on how various wood-based materials perform after a certain period of weathering. To elucidate this question, 17 wood samples were tested from the following species: oak (Quercus), sweet chestnut (Castanea sativa), European larch (Larix decidua), Scots pine heartwood and sapwood (Pinus sylvestris), Norway spruce (Picea abies), and beech (Fagus sylvatica). Moisture performance of the wood samples was improved with thermal modification, wax, oil, and biocide treatment. Specimens were exposed to various degradation-aging factors (blue stain fungi, decay fungi, artificial weathering, and natural weathering). Various moisture performance tests were applied before and after aging: short-term water uptake (tensiometer), long-term water uptake, water vapor tests, drying tests, etc. The water exclusion efficacy of wood was decreased after aging. Aging factors were found to act synergistically and to have a more prominent influence on less durable wood compared to durable or preservative-treated wood. Wax-treated wood performed best, regardless of which moisture performance test was applied.

Membrane distillation (MD) is a technology that can treat feed solutions with higher osmotic pressure, as well as produce high-purity water. However, the water production cost of the MD process is expensive. In this study, to decrease the water production cost, we attempted to evaluate the effect of membrane characteristics on the long-term stability of a vacuum MD (VMD) system. We fabricated four different types of polyvinylidene difluoride hollow fiber membranes, and operated a VMD system with 3.5 wt% NaCl aqueous solution at 65 °C as a feed under 11 kPa of air gap pressure. Consequently, in the proposed VMD system, it is found that the liquid entry pressure (LEP) is the most important factor. When LEP was higher than 0.37 MPa, the pilot-scale module was very stable for long-term operations, and the vapor flux was approximately 19.3 kg/m2·h with a total salt retention factor of over 99.9% during the 300-h operation.

Abstract We fabricated a new composite material with increased lyocell (a form of rayon that consists of cellulose fiber made from dissolving wood pulp) content through a surface hydrophobic treatment using phenyl silane and fiber carding/melt pressing. A matrix of polylactic acid (PLA) was used to enhance the environment-friendly properties of the composite and a carding process was used to orient the fibers in the composite. The lyocell content was controlled from 10% to 90%. Cross direction (CD) and machine direction (MD) samples were prepared to confirm the effect of the fiber directionality of the composite on its mechanical properties. The MD samples performed better than the CD samples. The tensile, flexural, and impact strengths of the composite were increased by approximately 85%, 155%, and 55%, respectively, after surface treatment. In the heat-resistance evaluation, confirmed by pyrolysis, surface treatment showed an average improvement of more than 10 °C. The water-absorption characteristics showed dramatic improvement, with enhanced surface-wetting properties and excellent initial moisture-absorption properties in the immersion test. Based on the comprehensive results, we conclude that the performance of the composite was satisfactory even when the content of lyocell was 50% or more. Graphical abstract Image 1 Highlights • This paper deals with the development of environmentally friendly green composite materials using regenerated cellulose Lyocell and PLA fibers. • By using carding/melt pressing process technology, it was possible to obtain lyocell rich composite material. • Phenyl silane surface treatment technology is very effective in improving internal bonding strength of composite materials. • Through directional control, composite with very good strength in mechanical direction were produced. • Mechanical properties, heat resistance and water resistance tend to increase with surface treatment. • This technology will be a good example to maximize the content of naturally based fillers. [ABSTRACT FROM AUTHOR]

This work aims at developing a hydrophobic treatment for jute fiber-based nonwovens. Three solutions of titanium dioxide (TiO2) nanoparticles were prepared through a sol-gel method by varying the molar ratio of the various constituents. The nonwoven was pretreated with these solutions before being impregnated with different concentrations of stearic acid. The TiO2 nanoparticles synthesized are amorphous; their size varies with the concentration of ethanol used as a solvent in the sol-gel method. The nanoparticle coating produced on the jute fibers is uniform. The nonwoven wettability was evaluated by measuring its water contact angle and retention time; the nonwoven became hydrophobic at the lowest fatty acid concentration tested. An increase in the stability of the hydrophobicity was observed when the TiO2 nanoparticle pretreatment was used compared to the application of the stearic acid treatment only. No detrimental effect of the hydrophobic treatment on the nonwoven mechanical performance and thermal stability was observed. These results demonstrate the potential of the TiO2 nanoparticle/stearic acid treatment as a fast method to provide a stable hydrophobicity to recycled jute-based nonwovens. [ABSTRACT FROM AUTHOR]

Hydrophobic treatment is an important method to improve the waterproof properties of concrete. To evaluate the effectiveness of hydrophobic treatments on improving the salt frost resistance of concrete, two representative commercial ordinary water repellent agents of silane and organosilicone emulsion were selected, and concrete specimens with three water/cement ratios were fabricated. After the application of repellent agents on concrete surfaces, accelerated saline (5% MgCl2) freeze-thaw cycles were conducted on the specimens. The mass losses and relative dynamic modulus of elasticity (RDME) of concrete were tested periodically. The contact angles and water absorption ratios of concrete with and without hydrophobic treatments were also tested. Results showed that the repellent agents could substantially enhance the hydrophobicity of concrete and greatly reduce its water absorption. Different repellent agents exerted diverse improvements on concrete hydrophobicity. Meanwhile, the repellent agents could improve concrete resistance against salt scaling and RDME losses to a certain degree, and concrete with strong hydrophobicity showed relatively high salt frost resistance. However, the ordinary water repellent agents cannot achieve the same enhancement on salt frost resistance of concrete as that on the water hydrophobicity of concrete. With saline freezing and thawing cycles, the hydrophobic layer formed by the repellent agents on superficial concrete was destroyed gradually. As a result, the salt frost resistance of concrete from the hydrophobic treatments was ultimately lost.

Natural climatic conditions have significant negative impacts on the long-term mechanical properties and dimensional stability of bio-based concrete considering the high water absorption of bio-aggregates and corresponding biodegradations. In this study, the effects of three hydrophobic treatments (integral mixing, aggregate coating, concrete coating) on the physical properties, mechanical strengths, and drying shrinkage characteristics of bio-based peach kernel shell concrete in real climatic natural environments are investigated. Results show that bio-based peach kernel shell concrete has lower mechanical strength in outdoor climatic conditions than in indoor standard curing conditions. The swelling and shrinkage process causes the visible microcrack and debonding between bio-based materials and mortar interface. The drying shrinkage of bio-based peach kernel shell concrete in outdoor conditions is highly dependent on real climatic environments, including temperature, humidity and rainfall. The hydrophobic surface-coated concrete exhibits excellent resistance to real climatic environments, as well as good mechanical strength and dimensional stability, with 15.7% less drying shrinkage in 18 months, compared to reference concrete. Moreover, cellulose and hemicellulose of heat-treated bio-aggregates do not degrade over time in outdoor conditions due to the enhanced biodegradation resistance. The hydrophobic surface coating treatment is recommended for enhancing the service life of bio-based peach kernel shell concrete in real climatic environments. [Display omitted] • Long-term mechanical strength and drying shrinkage of bio-concrete in real climatic environments are investigated. • Effects of real climatic environments (temperature, humidity, rainfall) on bio-concrete are evaluated. • Effects of hydrophobic treatments on the long-term performance of bio-concrete are discussed. • Hydrophobic surface coating improves the dimensional stability of bio-concrete in real climatic environments. [ABSTRACT FROM AUTHOR]

The use of wood in outdoor, above-ground applications is increasing in Europe. To further increase wood usage, more information related to service life and maintenance costs must be provided. Water exclusion efficacy (WEE) is one of the most important factors influencing service life and strongly correlates to wood moisture dynamics, surface properties, and hydrophobicity (WEE as a whole). WEE can be improved with modifications and hydrophobic treatments. The aim of this study was to elucidate which wood surface properties affect WEE and to note changes over time caused by artificial or natural aging. Wood samples of oak (Quercus), sweet chestnut (Castanea sativa), European larch (Larix decidua), Scots pine heartwood and sapwood (Pinus sylvestris), Norway spruce (Picea abies), and beech (Fagus sylvatica) were used to investigate this phenomenon. The moisture performance of the wood samples was improved with thermal modification, wax, oil, and biocide treatment. In total, 17 materials were prepared. After treatment, four different aging procedures were applied. Before and after aging, Fourier transform infrared spectra, colour, and contact angle were determined. The analysis of untreated wood based materials indicated that durability and hydrophobicity are related. Of all the treatments, wax performed the best and retained high hydrophobicity even after the most severe aging method (outdoor exposure).

A novel approach has been presented to add a dual‐crystalline hydrophobic admixture in fresh concrete for improving hydrophobicity against chloride and harmful chemicals. Dual‐crystalline material can utilize water of the fresh concrete to form crystals, but the challenge is to maintain adequate hydration and strength while improving hydrophobicity. This study presents the results from a comprehensive laboratory investigation on the application of 1, 2 and 8% of crystallizing aqueous and cementitious hydrophobic mineral in fresh concrete. Despite the high slump in the fresh mixture, no segregation was observed in the matured concrete. There was a marginal reduction of strength when a high percentage of admixture was used. Despite this, significant reduction of water absorption was observed indicating greater hydrophobicity. The optimum performance was found in mixtures with 2% admixture. Mixture with 2% aqueous hydrophobic admixture revealed marginal strength gain compared to 2% crystalline cementitious hydrophobic admixture, although water protection appears to be better in cementitious mixture. [ABSTRACT FROM AUTHOR]

Abstract: 100 years durability for bridge and tunnel constructions – The variable 3‐stage concept After a relatively short period of use (about 20 years), very high levels of chloride were detected in the components of traffic structures (tunnel walls, emergency walkways, bridge piers, abutments, bridge caps) exposed to chloride impact. On some components, the resulting reinforcement corrosion had already progressed to such an extent that an exchange/demolition of the corresponding components had to be made. In order to be able to plan and execute more durable structures in the future, the so‐called 3‐step‐concept was developed in which a total of three approaches to increase the durability are available and can be assigned individually to the different components. In the derivation of the variable 3‐step concept, various durability‐related damages of traffic structures were first analyzed in order to identify the areas that are still not adequately protected by the normative durability requirements. At the same time, the factors influencing the durability (salt, traffic intensity, removal of the chloride source from the component, component orientation) were worked out, so that a meaningful classification of the components could be made with knowledge of damages and impacts. Based on the factors influencing the resistance side (concrete cover, material resistance concrete and steel, surface protection system), three solution strategies were developed with which the durability of components exposed to chlorides can be improved. Essentially, this is a slowdown in chloride transport through concrete‐technological measures, an increase in critical corrosion‐inducing chloride content by using reinforcing steel with increased corrosion resistance, and inhibiting chloride entry into the structural concrete by applying hydrophobic treatment. In the last step, it was possible to assign the measures necessary to the respective component categories to achieve a durability that is sufficient over the entire service life. [ABSTRACT FROM AUTHOR]

In recent years, micro-direct methanol fuel cells (μDMFC) with high energy density, environmental protection features, rapid start-up, mild operating conditions, and convenient fuel storage have become a research hotspot. Some difficulties must be overcome in order to realize the application of the μDMFC as one of the newest types of portable energy. Currently, water management is one of the main problems researched in the field of μDMFC. Therefore, we propose a new cathode water-feedback structure to alleviate the hazards of water flooding. We designed a new catholic support layer with stainless-steel fiber felt as the base material and carried out hydrophobic treatment on the exterior of the cathode. The influence of this composite material on the cathodic water management system is investigated, and the design scheme of this new structure is verified. Effective water management is verified by comparing photographs of the water flooding phenomenon on the cathode side. By analyzing the polarization curves and discharging curves, we demonstrate the contribution of the novel hydrophobic structure to the performance of the μDMFC. [ABSTRACT FROM AUTHOR]

Quantitative determination of trace elements like S, Fe, Cu, Mn and Pb in gasoline and S in diesel is of great importance due to the growing concerns over air pollution, human health and engine failure caused by utilization of gasoline and diesel with these harmful elements. A method of total reflection X-ray fluorescence (TXRF) was developed to measure these harmful trace elements in gasoline and diesel. A variety of factors to affect measurement results, including TXRF parameters, microwave-assisted digestion conditions and internal standard element and its addition, were examined to optimize these experimental procedures. The hydrophobic treatment of the surface of quartz reflectors to support the analyte with neutral silicone solutions could prepare thin films of gasoline and diesel digestion solutions for subsequent TXRF analysis. The proposed method shows good potential and reliability to determine the content of harmful trace elements in gasoline and diesel with high sensitivity and accuracy without drawing different standard calibration curves, and can be easily employed to screen gasoline and diesel in routine quality control and assurance. [ABSTRACT FROM AUTHOR]

A new line of research to enhance the performance of concrete under adverse (harsh) and normal (air cured) curing conditions is presented. A crystallising hydrophobic admixture and curing agents were added to fresh concrete to improve its resistance against severe environmental conditions. A two-stage approach was pursued by adding the crystallising admixture to fresh concrete followed by curing agents, in a wax and liquid forms, in a separate application process, followed by exposing concrete to normal and adverse curing conditions. Results obtained suggests that protecting concrete with the crystallising admixture followed by applying wax based curing agent improves concrete strength and its resistance to water ingress than concrete cured with the liquid curing agent. When following the crystallising-wax treating system under adverse curing conditions, a more conserved strength was noticed compared to that produced by the crystallising-liquid system. Using the liquid curing agent in concrete with high water to cement ratio (w/c) has increased the cracks in the internal structure, while water permeability has decreased, either under normal curing conditions or adverse conditions. Following this protection-curing system in industry would resolve the problem of applying protection on wet surfaces and increase concrete’s resistance to deterioration. A microscopic study of the crystallising material was attained with a Scanning Electron Microscope (SEM) to check crystal growth with time. [ABSTRACT FROM AUTHOR]

Visualization experiments are performed for horizontal mesh-wick flat-plate heat pipes with the evaporator and condenser sections chemically treated to manifest different surface wettabilities. Deionized water is used as the working fluid. The static contact angles ( θ 0 s) examined include θ 0,e = 0° and 13° (untreated) and θ 0,c = 0°, 13°, 80°, and 120°. The measured evaporator resistances are similar for θ 0,e = 0° and 13°. The condenser resistances for θ 0,c = 0° are the highest as the liquid in the condenser levels up to the wick top. The condensation for θ 0,c = 13° or larger exhibits cyclic dropwise condensation on the islands of exposed wire sections. With θ 0 as large as 120°, the water level in the condenser was lowest but numerous large round drops may sustain a while, along with other rapidly growing drops of different sizes, before they rupture and drain away. These large round drops act as heavy thermal barrier so that condenser resistances for θ 0,c = 80° and 120° are higher than for θ 0,c = 13°. Hydrophilic treatment on the evaporator fails to enlarge Q max , because while the capillarity increases slightly from θ 0 = 13° to θ 0 = 0°, the liquid flow is hindered by the deposited nanostructures. Among all the surface conditions tested, the untreated wick ( θ 0 = 13°) exhibits the best performances in both Q max and total thermal resistance. [ABSTRACT FROM AUTHOR]

Biorelevant dissolution is an indispensable tool utilized during formulation development and optimization for the prediction of in vivo bioavailability of pharmaceutical agents. Within that framework, membrane-permeation dissolution methodologies are widely used to model drug absorption. The current work evaluates polymer membrane surface modifications for production of biomimetic membranes to be employed in biorelevant dissolution studies. Biomimetic membranes exhibit hydrophilic and hydrophobic properties to simulate the intestinal membrane environment. Low temperature plasma treatment of microporous polyethersulfone (PES), nylon and polypropylene (PP) polymer membranes was applied to produce low energy surface layers with permanent hydrophobic and hydrophilic functionalities. Surface modifications on microporous polymer membranes were achieved by plasma treatments using tetrafluoromethane (CF), perfluorohexane (CF), dichloromethane (DCM) and water (HO). Surface characterization of treated membranes was evaluated using scanning electron microscopy energy dispersive x-ray spectroscopy (SEM-EDS), water contact angle (CA) and x-ray photoelectron spectroscopy (XPS) techniques. SEM-EDS analysis of polymer membranes treated with fluorinated and chlorinated solvents/gases depicts altered surface morphologies with enriched porosity. SEM-EDS and XPS analyses demonstrate the chemical modification at the surface of treated membranes is strongly influenced by the type of treatment gas or solvent. Results show fluorination as a more effective and less destructive treatment technique. XPS confirmed the presence of elemental fluorine functional groups at the surface of the PES and nylon membranes. Evaluating elemental changes (F/C ratio) from multiple techniques confirms fluorinated plasma treatments are localized to the surface of the membrane and do not significantly affect the bulk properties. In a supplemental study, a detailed comparison of the plasma treated polymer membranes and porcine intestines revealed the biomimetic nature of the modified membranes. [ABSTRACT FROM AUTHOR]

This work describes hydrophobic treatments developed for natural fibers. They involve the coating of fibers and nonwovens by metal oxide nanoparticles, namely titanium dioxide (TiO 2 ) and zinc oxide (ZnO), followed by the application of a fatty acid. For comparison purposes, the fatty acid treatment was also applied directly on the fibers, i.e. without the intermediate nanoparticle layer. The efficiency of the treatments was assessed on recycled jute in terms of water contact angle and water drop shape retention time. In addition, the effect of the hydrophobic treatment process on the mechanical performance and thermal stability was also measured. The results show the advantage of the metal oxide nanoparticle intermediate layer in providing the natural fibers with stable hydrophobic properties. These treatments provide a nontoxic, low cost solution to make natural fibers hydrophobic, including recycled ones. This opens new opportunities for these fibers as reinforcement for composite parts. [ABSTRACT FROM AUTHOR]

This work aims at developing a hydrophobic treatment for jute fibres based on the grafting and growth of zinc oxide (ZnO) nanorods on the fibre surface. The first step consists in removing impurities from the fibre surface with a scouring treatment. In the second step, the jute fibres are coated with a layer of ZnO nanoseeds. A hydrothermal process is carried out as a third step to ensure a uniform growth of ZnO nanorods on the surface of the jute fibres. Finally, a hydrophobic treatment is performed on the ZnO nanorod-covered jute fibres using stearic acid (SA), i.e., a typical fatty acid. A large improvement in the fibre hydrophobicity was obtained without any negative effect on thermal stability and limited reduction in strength. Complementary measurements by scanning electron microscopy and X-ray diffraction were also performed and revealed a hexagonal system for the ZnO nanorods. [ABSTRACT FROM AUTHOR]

Wood that is used in outdoor applications is frequently exposed to weathering and is thus prone to fungal degradation. Ways to prevent fungal degradation include keeping the wood dry. The majority of hydrophobic and wood modification systems have been tested only on freshly treated wood. Little information is available on how various woodbased materials perform after a certain period of weathering. To elucidate this question, 17 wood samples were tested from the following species: oak (Quercus), sweet chestnut (Castanea sativa), European larch (Larix decidua), Scots pine heartwood and sapwood (Pinus sylvestris), Norway spruce (Picea abies), and beech (Fagus sylvatica). Moisture performance of the wood samples was improved with thermal modification, wax, oil, and biocide treatment. Specimens were exposed to various degradation-aging factors (blue stain fungi, decay fungi, artificial weathering, and natural weathering). Various moisture performance tests were applied before and after aging: short-term water uptake (tensiometer), long-term water uptake, water vapor tests, drying tests, etc. The water exclusion efficacy of wood was decreased after aging. Aging factors were found to act synergistically and to have a more prominent influence on less durable wood compared to durable or preservative-treated wood. Wax-treated wood performed best, regardless of which moisture performance test was applied. [ABSTRACT FROM AUTHOR]

The natural fibrous materials are widely used as thermal insulator for building application. The thermal insulating performance of natural fibrous material are affecting by the high humidity and temperature. Due to high moisture in natural fibrous insulators, they are very susceptible for microorganisms attack as well as the reduction in the thermal insulating properties. In this work, hydrophobic surface treatment was given to the wood fibrous insulator using octadecyltrichlorosilane (OTS). The deposition of OTS monolayers on wood fibers surface was confirmed by X-ray photoelectron microscopy (XPS), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and water contact angle of wood fibers measured by sessile drop method. The influence of hydrophobic treatment on hygric properties of wood fibrous insulator was characterized using especially designed double-climatic set-up. The effectiveness of hydrophobic treated wood fibers towards mould fungi growth was also examined. The hydrophobic treatment improved the hygric properties and effectiveness towards mould significantly. [ABSTRACT FROM AUTHOR]

Whilst the use of curing agents is common practice in the production of reinforced concrete, it is not normal to apply protective treatments to freshly cast concrete. Such treatments, which are generally hydrophobic in nature, are commonly applied to matured concrete, as protection against chloride and water absorption and associated cyclic freeze thaw attack. One gateway issue in respect to the application of such surface treatments to fresh concrete, is its unavoidably high moisture content, which is known to substantially downgrade the effectiveness of silane and siloxane hydrophobic treatments. The possibility of protectively treating fresh concrete is interesting from the logistic and economic standpoints, in the matter of early completion of on-site works. Towards this advantageous position, it is interesting to observe that early surface treatment with a crystallising hydrophobic mineral solution, immediately followed by a curing agent application, safeguards the 28 day strength of concrete in an extremely adverse curing environment. Added to this, the treated concrete sorptivity values with protected curing and the adverse curing regime, are similar, indicating that concrete durability may also be protected by the combined surface treatment, applied as early as 3 h following casting. [ABSTRACT FROM AUTHOR]

Carbon fiber based felt materials are widely used as gas diffusion layer (GDL) in fuel cells. Their transport properties can be adjusted by adding hydrophobic agents such as polytetrafluoroethylene (PTFE). We present a synchrotron X-ray tomographic study on the felt material Freudenberg H2315 with different PTFE finishing. In this study, we analyze changes in microstructure and shape of GDLs at increasing degree of compression which are related to their specific PTFE load. A dedicated compression device mimicking the channel-land pattern of the flowfield is used to reproduce the inhomogeneous compression found in a fuel cell. Transport relevant geometrical parameters such as porosity, pore size distribution and geometric tortuosity are calculated and consequences for media transport discussed. PTFE finishing results in a marked change of shape of compressed GDLs: surface is smoothed and the invasion of GDL fibers into the flow field channel strongly mitigated. Furthermore, the PTFE impacts the microstructure of the compressed GDL. The number of available wide transport paths is significantly increased as compared to the untreated material. These changes improve the transport capacity liquid water through the GDL and promote the discharge of liquid water droplets from the cell. [ABSTRACT FROM AUTHOR]

Silane is a commonly used surface treatment to reduce water entry into concrete. Only limited work has been done to show the effective lifespan of silane treatments. This work uses 360 cores taken from 60 bridge decks treated with silane that have been in-service between 6 and 20 years. Optical staining techniques showed that the average silane thickness started decreasing after 12 years of service. The deterioration primarily occurs from the bulk of the concrete towards the surface. This suggests that deterioration from the alkali pore solution of the concrete may be important. [ABSTRACT FROM AUTHOR]

The use of wood in outdoor, above-ground applications is increasing in Europe. To further increase wood usage, more information related to service life and maintenance costs must be provided. Water exclusion efficacy (WEE) is one of the most important factors influencing service life and strongly correlates to wood moisture dynamics, surface properties, and hydrophobicity (WEE as a whole). WEE can be improved with modifications and hydrophobic treatments. The aim of this study was to elucidate which wood surface properties affect WEE and to note changes over time caused by artificial or natural aging. Wood samples of oak (Quercus), sweet chestnut (Castanea sativa), European larch (Larix decidua), Scots pine heartwood and sapwood (Pinus sylvestris), Norway spruce (Picea abies), and beech (Fagus sylvatica) were used to investigate this phenomenon. The moisture performance of the wood samples was improved with thermal modification, wax, oil, and biocide treatment. In total, 17 materials were prepared. After treatment, four different aging procedures were applied. Before and after aging, Fourier transform infrared spectra, colour, and contact angle were determined. The analysis of untreated wood based materials indicated that durability and hydrophobicity are related. Of all the treatments, wax performed the best and retained high hydrophobicity even after the most severe aging method (outdoor exposure). [ABSTRACT FROM AUTHOR]

The durability of concrete and concrete structures is significantly influenced by environmental conditions, resulting in e.g. the ingress of water and incorporated aggressive agents, with the latter being responsible for initiating and progress of deterioration processes within the material system. In order to reduce the ingress of water, water repellent agents are applied onto the concrete surface (surface treatment), with its performance strongly depending on the agent itself, the mode of application, environmental conditions etc. For the assessment of the performance of surface-treated concrete, standard test methods, such as Karsten-Tube penetration test, contact angle measurement, hydrophobic quality test, as well as more refined test methods, such as Infrared Spectroscopy (IR), moisture sorption analysis, and scanning electron microscopy coupled with elemental X-ray analysis (SEM/EDS) are used. These methods are commonly employed for the assessment of surface-treated ordinary concrete, leaving the question on their applicability to material systems exhibiting a denser microstructure, such as High Performance Concrete (HPC), unanswered. Within this experimental study, the aforementioned test methods are critically reviewed regarding their potential application to HPC, finally providing recommendations for evaluating the performance and durability of water-repellent surface treatment when applied to HPC. [ABSTRACT FROM AUTHOR]

Microelectronic devices are developing rapidly in portability, wearability, and implantability. This puts forward an urgent requirement for the delicate deposition process of materials. Electrohydrodynamic printing has attracted academic and industrial attention in preparing ultrahigh-density microelectronic devices as a new noncontact, direct graphic, and low-loss thin film deposition process. In this work, a printed graphene with narrow line width is realized by combining the electrohydrodynamic printing and surface treatment. The line width of printed graphene on the hydrophobic treatment surface reduced from 80 to 28 μm. The resistivity decreased from 0.949 to 0.263 Ω·mm. Unexpectedly, hydrophobic treatment can effectively induce random stacking of electrohydrodynamic printed graphene, which avoids parallel stacking and agglomeration of graphene sheets. The performance of printed graphene is thus effectively improved. After optimization, a graphene planar supercapacitor with a printed line width of 28 μm is successfully obtained. Its capacitance can reach 5.39 mF/cm 2 at 50 mV/s, which is twice higher than that of the untreated devices. The device maintains 84.7% capacitance after 5000 cycles. This work provides a reference for preparing microelectronic devices by ultrahigh precision printing and a new direction for optimizing two-dimensional material properties through stacking adjustment.