Water Drop Contact Angle Research Articles

Are Metal Complexes “Organic,” “Inorganic,” “Organometallic,” or “Metal-Organic” Materials? A case Study for the Use of Trinuclear Coinage Metal Complexes as “Metal-Organic Coatings” for Corrosion Suppression on Aluminum Substrates

This article provides a second manifestation of a new tradition by which the editors of Comments on Inorganic Chemistry wish to lead by example, whereby we start publishing original research content that, nonetheless, preserves the Journal’s identity as a niche for “critical discussion of the current literature” of inorganic chemistry. (For the first manifestation, see: Otten, B. M.; Melancon, K. M.; Omary, M. A. “All That Glitters is Not Gold: A Computational Study of Covalent vs Metallophilic Bonding in Bimetallic Complexes of d10 Metal Centers—A Tribute to Al Cotton on the 10th Anniversary of His Passing,” Comments Inorg. Chem. 2018, 38, 1–35.) Thus, herein we show that a trinuclear copper (I) complex {[3,5-(CF3)2Pz]Cu}3 (henceforth referred to as the “Cu trimer”) can act as a “metal-organic coating” for corrosion protection of aluminum, whereas its silver analogue, {[3,5-(CF3)2Pz]Ag}3 (i.e., the “Ag trimer”), could not. The manuscript was initially submitted to journals that usually publish on “organic coatings” but was rejected on the premise that a metal complex cannot be considered “organic” unless it is incorporated into a polymer. This issue is commented upon herein in the broader context of whether to consider metal complexes “organic,” “inorganic,” “organometallic,” or “metal-organic” materials with manifestations of the use of each classification in the literature. We have found that, upon coating the Cu trimer onto an aluminum (AA 3003) surface, potentiodynamic polarization results in 3.5% NaCl show an increase in corrosion potential (Ecorr) by ~ 0.6 V concomitant with a three-order-of-magnitude decrease in corrosion current density (icorr) from 0.025 µA/cm2 for uncoated aluminum to ~ 9.6 × 10–5 µA/cm2 for the Cu trimer-coated surface. With a double coating, the Cu trimer formed a completely insulating surface with no current flow, even at very high potential magnitude and range. Open circuit potential was used to study the stability of the Cu trimer films on the Al surface in the electrolyte solution. Scanning electron microscopy and Fourier-transform infrared spectroscopy techniques were used to characterize the structure of both the Cu trimer powder and Cu trimer film on the aluminum surface before and after the corrosion tests. The hydrophobicity of the Cu trimer coating was determined by using water drop contact angle measurements, which demonstrated an increase from 65° to 137° for the uncoated and coated aluminum, respectively. The thermal stability of the Cu trimer was analyzed using thermogravimetric analysis, giving rise to weight loss resistance up to ~190 °C. The results clearly demonstrate that the Cu trimer layers exhibit superior stability and potential for corrosion protection of aluminum surfaces in corrosive environments. The Ag trimer analogue, meanwhile, failed the “tape test” that the Cu trimer passed to assess the mechanical stability of such “metal-organic” coatings. Density functional theory (DFT) simulations provide insights on this difference upon modeling the interaction of each cyclotrimer molecule (and other analogous ones) with an Al atom on the one hand and contrasting the resulting binding energies with the corresponding dissociation energies of the metallophically-bound crystalline solid form of each trimer. Thus, it was found that Ag trimer models are bound to the Al atom at least as strongly as Cu trimer models are; yet, that bonding is not sufficiently high so as to overcome the argentophilic attraction, whereas it can overcome the cuprophilic attraction. Other explanations are also given to account for trimer interactions with aluminum oxide as well as partial oxidation of only the Cu trimer, which strengthens the interaction with the Al atom.

Grafted Polymer Coatings Enhance Fouling Inhibition by an Antimicrobial Peptide on Reverse Osmosis Membranes.

Bacterial biofilms that are formed on surfaces are highly detrimental to many areas of industry and medicine. Seawater desalination by reverse osmosis (RO) suffers from biofilm growth on the membranes (biofouling), which limits its widespread use because biofouling decreases water permeance and necessitates module cleaning and replacement, leading to increased economic and environmental costs. Antimicrobial peptides (AMPs) bound covalently to RO membranes inhibit biofilm growth and might delay membrane biofouling. Here we examined how various hydrophilic membrane coatings composed of zwitterionic, neutral, positively charged, and poly(ethylene glycol) (PEG)-grafted polymers affected the biocidal activity and the biofilm inhibition of a covalently bonded AMP on RO membranes. AMP magainin-2 was linked by the copper-catalyzed azide-alkyne cycloaddition reaction to a series of RO membranes that were grafted with different methacrylate polymers. Surface characterization by infrared spectroscopy, X-ray photoelectron spectroscopy, and water drop contact angle gave evidence of successful RO modifications, and zeta potential analysis reflected the increase in surface charge due to the linked, positively charged peptide. All AMP-modified membranes inhibited Pseudomonas aeruginosa growth compared to unmodified membranes, and the grafted methacrylic polymers did not significantly interfere with the peptide activity. On the other hand, membranes coated with zwitterionic and other acrylate polymers including AMP attachment inhibited biofilm growth more than either the AMP or the polymer coating alone. This enhancement led to ∼20% less biofilm biovolume on the membrane surfaces. The combination of antimicrobial coatings with polymer coatings known to resist fouling might aid future designs of surface coatings susceptible to biofilm growth.

Surface modification of silica nanoparticle using dichlorodimethylsilane for preparation of self-cleaning coating based on polyurethane and polydimethylsiloxane

In this work, a superhydrophobic self-cleaning coating was prepared in three steps; firstly, silica nanoparticles were synthesized using stober method, secondly the surface of silica nanoparticles was modified using dichlorodimethylsilane (DDS), finally, surface modified silica nanoparticles were applied on the surface of un-cured polyurethane or polydimethylsiloxane resins which resulted in superhydrophobic coating with suitable self-cleaning properties. Surface modification of silica nanoparticles using different concentration of DDS lead to desired particle size and particle size distribution. The FTIR spectra showed that hydrogen of silica particles are substituted by SiCl(CH3)2 functional groups which are known as the origin of hydrophobicity of the surface. Furthermore, measuring the contact angle of water drop with the coated surface showed that by increasing the silica nanoparticles concentration, the hydrophobicity of the coating was increased. Electrochemical impedance spectroscopy (EIS) results indicated that corrosion resistance of coating depends directly on the concentration of nanoparticles in coating.

Vapor-Phase Plotting of Organosilane Chemical Gradients.

Vapor-phase plotting of organosilane-based self-assembled monolayer (SAM) gradients is demonstrated for the first time. Patterned SAMs are formed by delivering gas-phase organotrichlorosilane precursors to a reactive silica surface using a heated glass capillary. The capillary is attached via a short flexible tube to a reservoir containing the precursor dissolved in toluene. The proximal end of the capillary is positioned at an experimentally optimized distance of 30 μm above the substrate during film deposition. The capillary is mounted to a stepper-motor-driven X, Y plotter for raster scanning above the surface. Two different organotrichlorosilane precursors are employed in this initial demonstration: n-octyltrichlorosilane and 3-cyanopropyltrichlorosilane. The dependence of SAM deposition on ambient relative humidity, capillary-substrate separation, raster-scanning speed, and solvent viscosity and volatility is explored and optimum deposition conditions are identified. The optimized procedures are used to plot uniformly modified square "pads" and gradients of the silanes. Film formation is verified and the gradient profiles are obtained by sessile drop water contact angle measurements, spectroscopic ellipsometry measurements of film thickness, and X-ray photoelectron spectroscopy mapping. The resolution of the plotting process is currently in the millimeter range and depends on capillary diameter and distance from the substrate surface. Vapor-phase plotting affords a unique direct-write method for producing patterned and chemically graded SAMS that may find applications in microfluidic devices, planar chromatography, and optical and electronic devices.

Clay Nanoparticles Composite Membranes Prepared with Three Different Polymers: Performance Evaluation

This paper presents the results obtained from the evaluation of clay nanoparticles as an additive for improving the characteristics and performance of composite membranes cast with polysulfone (PS), polyethersulfone (PES), and polyvinylidene fluoride (PVDF). Different concentrations of clay nanoparticles, ranging from 1 to 10% based on the polymer mass, were used to prepare all dope solutions. The addition of clay nanoparticles changed the internal pore morphology of membranes, which resulted in significant changes on their performance, regarding its water permeability, and fouling potential. The optimum nanoclay concentration for permeability enhancement was different for each polymer, 1.5%, 2.0%, and 6.0% for PS, PES, and PVDF, respectively. This difference can be attributed to the differences of polymer’s hydrophobicity, based on the contact angle of a sessile water drop, which is higher for PVDF (PVDF is more hydrophobic than PS and PES). The flow improvement changed based on the main polymer. Significant changes in internal pore structure were observed for all membranes. The proportion of macrovoids was decreased and pores had a better connectivity across the cross section for PES and PS membranes. For PVDF membranes, the addition of nanoclay had a different effect on their microstructure. In this case, internal pores were 20% wider, factor that increased the average membrane porosity. The simultaneous evaluation of the clay nanoparticles used as an additive have clearly demonstrated its potential application for composite membrane production. It is also worth to note that the best way for identifying and evaluating the potential for an additive for membrane casting is considering its effects for different polymers, under the same casting conditions.

Superhydrophobic, Superoleophobic and Antimicrobial Coatings for the Protection of Silk Textiles

A method to produce multifunctional coatings for the protection of silk is developed. Aqueous dispersion, free of any organic solvent, containing alkoxy silanes, organic fluoropolymer, silane quaternary ammonium salt, and silica nanoparticles (7 nm in mean diameter) is sprayed onto silk which obtains (i) superhydrophobic and superoleophobic properties, as evidenced by the high contact angles (>150°) of water and oil drops and (ii) antimicrobial properties. Potato dextrose agar is used as culture medium for the growth of microorganisms. The protective coating hinders the microbial growth on coated silk which remains almost free of contamination after extensive exposure to the microorganisms. Furthermore, the multifunctional coating induces a moderate reduction in vapor permeability of the treated silk, it shows very good durability against abrasion and has a minor visual effect on the aesthetic appearance of silk. The distinctive roles of the silica nanoparticles and the antimicrobial agent on the aforementioned properties of the coating are investigated. Silica nanoparticles induce surface structures at the micro/nano-meter scale and are therefore responsible for the achieved extreme wetting properties that promote the antimicrobial activity. The latter is further enhanced by adding the silane quaternary ammonium salt in the composition of the protective coating.

Preparation of Water-Repellent Monomolecular Films by CF<sub>4</sub> Plasma Treatment on Hydrocarbon Monolayers

Hydrocarbon monomolecular films were prepared on a glass slide with a chemical adsorption technique. Water-repellent fluorocarbon monomolecular films were prepared by CF4 plasma treatment on the chemically adsorbed hydrocarbon monomolecular films. However, the monomolecular films were usually removed by sputtering when the CF4 plasma was treated, because CF4 plasma contains ions of the fluorocarbon fragments, not only its radicals. Therefore, fluorocarbon ions were removed from the plasma by mesh connected to the earth, and then only fluorocarbon radicals were used for treatment in order to prevent the monomolecular film from being removed. Fourier-transform infrared reflection absorption spectroscopy (FTIR-RAS) revealed that the hydrocarbon groups or hydrogens of the hydrocarbon monomolecular film were substituted with fluorocarbon or a fluorocarbon radical. In addition, the water drop contact angle of the film slightly increased by the treatment. It was demonstrated that water-repellent monomolecular films can be prepared by CF4 plasma treatment on hydrocarbon monolayers. Thus, the plasma treatment technique may be useful into preparing the highly durable fluorinated monomolecular films with the cross linkage inter adsorbed molecules in the monolayer films.

New Field Sampling Method to Analyze Spatial Distribution of Small‐Scale Soil Particle Surface Properties and Processes in Intact Soil

Core Ideas New field sampling and preparation method for thin undisturbed soil slices was developed. Particle surface properties and processes can be determined at small scales. Millimeter‐scale spatial distribution of wetting properties determined by water drop contact angles. Geostatistics revealed different spatial correlation ranges for top‐ and subsoil. This study developed a field sampling and preparation method to obtain soil slices (7.5 by 20 by 3.5 cm, maximum seven parallel slices) with intact surfaces that allows analysis of surface properties and processes with high spatial resolution. In an example application, soil wetting properties (in terms of contact angle, CA) of sandy and loamy top‐ and subsoil slices were analyzed. Mapping of the CA (millimeter grid) revealed high variability (0–130°) for topsoil. Subsoil surfaces were wettable (0–5°), however, high CA (?70°) domains could be identified and associated with a textural boundary. Semivariances indicated higher heterogeneity and higher spatial correlation ranges for the topsoil. Results indicate that our approach allows the detection of small‐scale variations and is a promising tool to analyze surface properties with high spatial resolution on parallel soil slices.

Facile Fabrication of Ordered Component-Tunable Heterobimetallic Self-Assembly Nanosheet for Catalyzing "Click" Reaction.

How to maximize the number of desirable active sites on the surface of the catalyst and minimize the number of sites promoting undesirable side reactions is currently an important research topic. In this study, a new way based on the synergism to achieve the successful fabrication of an ordered heterobimetallic self-assembled monolayer (denoted as BMSAM) with a controlled composition and an excellent orientation of metals in the monolayer was developed. BMSAM consisting of phenanthroline and Schiff-base groups was prepared, and its novel heterobimetallic (Cu and Pd) self-assembled monolayer anchored in silicon (denoted as Si-Fmp-Cu-Pd BMSAM) with a controlled composition and a fixed position was fabricated and characterized by UV, cyclic voltammetry, Raman, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), X-ray diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES), and water-drop contact angle (WDCA) analyses. The effects of Si-Fmp-Cu-Pd BMSAM on its catalytic properties were also systematically investigated using “click” reaction as a template by WDCA, XPS, SEM, XRD, ICP-AES and in situ Fourier transform infrared analyses in a heterogeneous system. The results showed that the excellent catalytic characteristic could be attributed to the partial (ordered or proper distance) isolation of active sites displaying high densities of specific atomic ensembles. The catalytic reaction mechanism of the click reaction interpreted that the catalytic process mainly occurred on the surface of the monolayer, internal active site (Pd) and rationalized that the Cu(I) species and Pd(0) reduced from the Cu(II) and Pd(II) catalyst were active species, which had a proper distance between two different metals. The cuprate–triazole intermediate and the palladium intermediate, whose production is the key step, should lie in a proper position between the copper and active palladium sites, with which the reaction rate of transmetalation would be improved to increase the amount of the undesired Sonogashira coupling product.

Superhydrophobic Coatings on Aluminium Based on Carboxylic Acids

Development of new coatings for corrosion protection should be directed to environmentally friendly yet efficient technologies. Industrial applications additionally demand energy sustainability and cost effectiveness. Among varieties of new coatings being developed superhydrophobic coatings are also in the focus of current research in both academic and industrial sectors. The background of their use, inspired by effects in nature, is the prevention of ingress of electrolyte to underlying substrate and properties of self-cleaning and anti-sticking. Superhydrophic surfaces can be applied to different substrates, from metal, textile, plastics, etc. Superhydrophobicity can be related to surface texture or surface chemistry, e.g., use of silane-, fluoro-based or other compounds [1]. The basic idea of the current research study is to design multifunctional compounds by integrating corrosion inhibitors and hydrophobic agents with lipophilic or fluorous properties into hybrid matrices so as to produce a corrosion resistant hydrophobic coating that display good adhesion to Al substrates. The first step is to test potential candidates for (i) hydrophobic compounds and (ii) corrosion inhibitor compounds. Among hydrophobic compounds, carboxylic acids were tested since they offer environmentally friendly and cheap option. In order to adsorb carboxylic acids on metal surface an appropriate pre-treatment is required. In the present work we investigated the possibility to fabricate superhydrophobic surfaces on aluminium metal pre-treated by alkaline etching at 90 °C [2] which represents a green solution-phase method to produces hierarchical growth of the aluminium hydroxide array. After immersion in ethanol solution of carboxylic acid the surface turns superhydrophobic. In the present study we have investigated the effect of several parameters on the formation of superhydrophobic surface on aluminium pre-treated by etching: type of etching as a pre-treatment, length of carboxylic chain, time of immersion in carboxylic acid and concentration of carboxylic acid. The effect of these parameters on the water contact angle and corrosion properties in 0.5 M NaCl solution were determined. Depending on the type of carboxylic acid a remarkable decrease in both cathodic and anodic current density can be achieved. Optimal parameters were denoted as those achieving high water contact angle, and low corrosion current density combined with a broad passive range. XPS showed that after alkaline etching the aluminium surface was fully covered by an hydroxide layer. ToF-SIMS provided direct evidence of adsorption of octanoic and stearic acids. Coatings prepared on Al by self-assembling in carboxylic acids were tested also by long-term immersion in NaCl solution. Surface durability in terms of resistance in acid and alkaline solution, as well as sliding angle were determined. Morphology of self-assembled carboxylic layers on alkaline etched aluminium analysed by FE-SEM shows nano-rough surface with numerous micro-cones with steps or terraces giving the surface a dual roughness. Composition of the surface was investigated using various surface analytical methods, i.e. FTIR, XPS and SIMS. Adsorption bonding of carboxylic acids to hydroxylated Al surfaces is also being investigated by DFT calculations. We utilized periodic slab model of passivated surface with hydroxylated oxide-layer supported on Al metal. These calculations help us to scrutinize details of how carboxylic head-groups attach to hydroxylated surface and how lateral intermolecular interactions and their self-assembly depends on the length of the aklyl tail. The effect of the organic layer composition on the resulting electronic properties of the passive layer (band gap, electronic workfunction) is also investigated. Fig. 1. FE-SEM image of aluminium surface etched in NaOH and immersed in 5 mM ethanol solution of stearic acid. Detail: contact angle of water drop 156°. Acknowledgments: This work is a part of M.ERA-NET project entitled “Design of corrosion resistant coatings targeted for versatile applications”, acronym COR_ID. The financial support of the project by Ministry of Education, Science and Sport of Republic of Slovenia (Programmes of International Scientific Cooperation) and Agence Nationale de la Recherche, France, is acknowledged.

Organosilane Chemical Gradients: Progress, Properties, and Promise.

Chemical gradients play an important role in nature, driving many different phenomena critical to life, including the transport of chemical species across membranes and the transport, attachment, and assembly of cells. Taking a cue from these natural processes, scientists and engineers are now working to develop synthetic chemical gradients for use in a broad range of applications, such as in high-throughput investigations of surface properties, as means to guide the motions and/or assembly of liquid droplets, vesicles, nanoparticles, and cells and as new media for stationary-phase-gradient chemical separations. Our groups have been working to develop new methods for preparing chemical gradients from organoalkoxysilane and organochlorosilane precursors and to obtain a better understanding of their properties on macroscopic to microscopic length scales. This review highlights our recent work on the development of controlled-rate infusion and infusion-withdrawal dip-coating methods for the preparation of gradients on planar glass and silicon substrates, on thin-layer chromatography plates, and in capillaries and monoliths for liquid chromatography. We also cover the new knowledge gained from the characterization of our gradients using sessile drop and Wilhelmy plate dynamic water contact angle measurements, X-ray photoelectron spectroscopy mapping, and single-molecule tracking and spectroscopy. Our studies reveal important evidence of phase separation and cooperative interactions occurring along multicomponent gradients. Emerging concepts and new directions in the preparation and characterization of organosilane-based chemical gradients are also discussed.

Induced superhydrophobic and antimicrobial character of zinc metal modified ceramic wall tile surfaces

Hydrophobic surfaces are also known to have antimicrobial effect by restricting the adherence of microorganisms. However, ceramic products are produced by high temperature processes resulting in a hydrophilic surface. In this study, an industrial ceramic wall tile glaze composition was modified by the inclusion of metallic zinc powder in the glaze suspension applied on the pre-sintered wall tile bodies by spraying. The glazed tiles were gloss fired at industrially applicable peak temperatures ranging from 980°C to 1100°C. The fired tile surfaces were coated with a commercial fluoropolymer avoiding water absorption. The surfaces were characterized with SEM, EDS, XRD techniques, roughness, sessile water drop contact angle, surface energy measurements, and standard antimicrobial tests. The surface hydrophobicity and the antimicrobial activity results were compared with that of unmodified, uncoated gloss fired wall tiles. A superhydrophobic contact angle of 150° was achieved at 1000°C peak temperature due to the formation of micro-structured nanocrystalline zinc oxide granules providing a specific surface topography. At higher peak temperatures the hydrophobicity was lost as the specific granular surface topography deteriorated with the conversion of zinc oxide granules to the ubiquitous willemite crystals embedded in the glassy matrix. The antimicrobial efficacy also correlated with the hydrophobic character.

Co-immobilization of chitosan and dermatan sulfate from Raja montagui skin on polyethylene terephthalate surfaces: Characterization and antibiofilm activity

ABSTRACTIn this work, polyethylene terephthalate (PET) was chemically modified by covalent co-immobilization of two separate layers of bioactive polymers composed of chitosan and a new dermatan sulfate isolated from Raja montagui skin. The new materials obtained were characterized by determination of carboxyl groups, ATR-FTIR spectroscopy, drop water contact angle, SEM, and TGA measurements. The different immobilizations modified the surface characteristics; especially when the first layer was dermatan sulfate (PET–DS–Chito) which presented the best surface wettability (71 ± 3°). It also reduced the ability of Staphylococcus epidermidis to form biofilm on PET surfaces which could decrease the virulence of vascular prosthesis infections.

Single Molecule Catch and Release: Potential-Dependent Plasmid DNA Adsorption along Chemically Graded Electrode Surfaces.

Single molecule detection methods were employed to study the potential dependent adsorption and desorption of dye labeled plasmid DNA along chemical gradients prepared on indium tin oxide (ITO) electrodes. Gradients were formed over silica-base-layer-coated ITO surfaces by exposing them in a directional fashion to aminopropyltrimethoxysilane from the vapor phase. Sessile drop water contact angle measurements, spectroscopic ellipsometry, and X-ray photoelectron spectroscopy were used to verify that a gradient was formed and to characterize its wettability, thickness, and composition as a function of position. The gradient-coated ITO electrode served as both the working electrode and a window into the electrochemical cell used to manipulate DNA adsorption. For single molecule studies, the electrochemical cell was filled with buffer solution containing YOYO-1-labeled plasmid DNA. Fluorescence videos acquired along the gradients depicted clear position-, potential-, and pH-dependent variations in DNA adsorption and desorption. The results demonstrate that DNA adsorption was largely independent of applied potential and irreversible at high amine coverage (i.e., multilayers), under pH ∼ 6 buffer. DNA adsorption became more reversible as the amine coverage decreased and the solution pH increased. Potential dependent control over DNA adsorption and desorption was best achieved at monolayer-to-submonolayer aminosilane coverage under pH ∼ 8 buffer. The knowledge gained in these studies will aid in the development of electrochemical methods for the capture and release of DNA and other polyelectrolytes at electrode surfaces.

Interaction of human osteoblast-like Saos-2 cells with stainless steel coated by silicalite-1 films

This paper investigates the interaction of human osteoblast-like Saos-2 cells with stainless steel covered by a film of densely inter-grown silicalite-1 crystals with defined outer and inner surfaces. The chemical composition of this film, labeled as SF(RT), was tuned by heat treatment at 300°C and 500°C (labeled as SF(300) and SF(500), respectively) and characterized by X-ray photoelectron spectroscopy (XPS), water drop contact angle (WCA) measurements and scanning electron microscopy (SEM). The number, the spreading area and the activity of alkaline phosphatase of human osteoblast-like Saos-2 cells in cultures on the silicalite-1 film were affected by the chemical composition of its outer surface and by its micro-porous structure. The number and the spreading area of the adhered osteoblast-like cells on day 1 was highest on the surface of SF(RT) relative to their adhesion and spreading on a glass cover slip due to the SF(RT) topology. However, SF(300) markedly supported cell growth during days 3 and 7 after seeding.

Nanocoating on alkali-resistant glass fibers by octadecyltrichlorosilane to improve the mechanical strength of fibers and fibers/epoxy composites

Surface defects cause the measured tensile strength of alkali glass fibers to be significantly lower than their theoretical values. Coatings can be used to “heal” surface flaws and to modify surface properties. In the present work, the nanocoating on alkali-resistant glass (ARG) fiber rovings was carried out by self-assembled monolayers (SAMs) of octadecyltrichlorosilane (OTS). The ARG roving was dipped into OTS nanosol, which deposited the organic–inorganic SAMs of OTS on the ARG surface. The assessment of changes in the fiber surfaces was characterized by scanning electron microscopy (SEM) and fluorescence microscopy, while the chemical changes were characterized by X-ray photoelectron spectroscopy (XPS). Furthermore, the influence of nanocoating on the tensile properties of ARG and OTS-treated ARG with and without an epoxy matrix was also studied. The SEM analysis revealed the formation of nanoscale layers on the ARG surfaces and the XPS confirmed the deposition of organic–inorganic monolayers. The tensile strength of ARG rovings with and without the epoxy matrix was improved significantly. The OTS treatment almost created a superhydrophobic nanocoating on ARG, which was confirmed by the sessile drop water contact angle, and the water absorption by the ARG/epoxy composites reduced.

Cr-Si-Al-N 코팅의 상형성 및 표면 물성에 미치는 Si 함량의 영향

Cr-Si-Al-N coating with different Si content were deposited by hybrid physical vapor deposition (PVD) method consisting of unbalanced magnetron (UBM) sputtering and arc ion plating (AIP). The deposition temperature was <TEX>$300^{\circ}C$</TEX>, and the gas ratio of <TEX>$Ar/N_2$</TEX> were 9:1. The CrSi alloy and aluminum targets used for arc ion plating and sputtering process, respectively. Si content of the CrSi alloy targets were varied with 1 at%, 5 at%, and 10 at%. The phase analysis, composition and microstructural analysis performed using x-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) including energy dispersive spectroscopy (EDS), respectively. All of the coatings grown with textured CrN phase (200) plane. The thickness of the Cr-Si-Al-N films were measured about <TEX>$2{\mu}m$</TEX>. The friction coefficient and removal rate of films were measured by a ball-on-disk test under 20N load. The friction coefficient of all samples were 0.6 ~ 0.8. Among all of the samples, the removal rate of CrSiAlN (10 at% Si) film shows the lowest values, <TEX>$4.827{\times}10^{-12}mm^3/Nm$</TEX>. As increasing of Si contents of the CrSiAlN coatings, the hardness and elastic modulus of CrSiAlN coatings were increased. The morphology and composition of wear track of the films was examined by scanning electron microscopy (SEM) and energy dispersive spectroscopy, respectively. The surface energy of the films were obtained by measuring of contact angle of water drop. Among all of the samples, the CrSiAlN (10 at% Si) films shows the highest value of the surface energy, 41 N/m.

Static contact angle versus volume of distilled water drop on micro patterned surfaces

Static contact angle was determined experimentally in the condition of wetting of polished and laser patterned surfaces of stainless steel substrates by distilled water drops with different volumes. In contrast with polished surface, the contact angle was found to depend on drop volume on micro patterned surfaces. In addition, the enhancement of both hydrophilic and hydrophobic properties was observed on laser patterned surfaces.

Polyamide membrane surface and bulk modification using humid environment as a new heat curing medium

Heat curing was devised in temperature-controlled steam and water environments to synthesize reverse osmosis (RO) polyamide (PA) membrane. The effect of new curing media on the physicochemical properties and RO performance of the synthesized polyamides was fully investigated using X-ray photoelectron spectroscopy (XPS), attenuated total reflection infrared (ATR-IR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and water drop contact angle. The results show a reduction in amide linkage content on the surface of the steam-cured polyamide and surface and bulk of the water-cured polyamide. Additionally, it was revealed that heat curing in the humidity-controlled environment can be considered as a chemical modification process with the ability to change the cross-linking degree in adjustable depth and intensity. Heat curing in steam provided the membrane with great surface hydrophilicity, permeate flux, and salt rejection, which are required for treating dilute solutions. Moreover, the water-cured membrane exhibited extra high surface hydrophilicity and salt rejection that are necessary for treating solutions with high inorganic fouling tendency and high osmotic pressure.

Dynamic measurements and wettability phenomena in mesoporous anodic films prepared on 1050 and 2024T3 aluminium alloys

The wettability of mesoporous anodic films has until now been a parameter rarely studied although it remains crucial especially for sealing treatment following anodising. Wettability measurement is in fact complex as it depends on a number of process parameters relating to the three phases (mesoporous anodic film, deposited liquid and ambient gas). In the present study, an innovative experimental approach was first adopted involving measuring the characteristics of a deposited water drop (contact angle, chord length and height of the drop) in relation to time. Following this, a flow balance allowed the amount of water having infiltrated the mesopores to be determined for two types of anodic film, one tortuous (on an AA 2024T3 substrate), the other not (on an AA 1050 substrate). On the basis of models already available in the literature, a phenomenological mechanism (spreading, penetration and evaporation) was finally proposed and discussed especially with respect to the tortuosity and prior drying of mesoporous anodic films.