Sessile Drop Method Research Articles

Effect of cationic and anionic surfactants on the wettability and interfacial tension of oil-brine systems in analogous rocks from the Chicontepec Paleochannel, Mexico

The chemical enhanced oil recovery (cEOR) uses substances to improve the mobility of petroleum in reservoirs. Among these substances are the surfactants, whose purpose is to change the wettability and interfacial tension (IFT). We focus on experiments of surfactants in rocks from Chicontepec Paleochannel. CTAB, DTAB and SDS surfactants in brines of NaCl and KCl and mineral oil were investigated for reduction of IFT and contact angle alteration. The sessile and pendant drop methods were used to determine the IFT. The electrical affinity of the rock surface, dissolved ions, and the surfactant molecules, play key roles in the alteration of wettability and IFT. Thus, one scheme of interactions between the electrical charges is proposed on the basis of the rocky characterization and the following results: the lowest contact angle was 106° with CTAB at 0.01 wt% in brines at 9.25 g/L NaCl, and 108° with SDS at 0.01 wt% in brines at 20 g/L NaCl. The smallest IFT was 0.813 dyn/cm with CTAB at 0.5 wt% in brines at 5 g/L KCl. This work serves as first assessments of these surfactants to enhance the production in Chicontepec, employing cheap tensoactives to increase the applicability. Besides, these results will guide future displacement tests as cEOR lab simulation.

Evaluation of Surface Tension of CaO–SiO2–Al2O3‐Based Mold Flux Containing Ce2O3

The calculation model based on the surface tension of CaO–SiO2–Al2O3‐based mold flux containing Ce2O3 is studied using the modified Butler equation, and the surface tension of mold flux is measured by the sessile drop method. The experimental results show that the calculated surface tension based on the model agrees well with the experimental values, and the absolute value of the error is less than 3.23%. With the content of Ce2O3 in the mold flux increasing from 0% to 20%, the surface tension of the mold flux increases from 0.380 to 0.405 N m−1. The O2− dissociated from Ce2O3 makes the radius of the silicon–oxygen tetrahedral anion decrease, and the ion‐to‐ion interaction force in the melt increase. Therefore, the surface tension of the melt increases with the increase of Ce2O3 content in the mold flux. However, the amount of dissociated O2− is limited, so the effect of Ce2O3 on the surface tension of the mold flux is limited.

Methodology for characterizing the printability of hydrogels.

280Currently, the characterization techniques for hydrogels used in bioprinting are extensive, and they could provide data on the physical, chemical, and mechanical properties of hydrogels. While characterizing the hydrogels, the analysis of their printing properties is of great importance in the determination of their potential for bioprinting. The study of printing properties provides data on their capacity to reproduce biomimetic structures and maintain their integrity after the process, as it also relates them to the possible cell viability after the generation of the structures. Current hydrogel characterization techniques require expensive measuring instrument that is not readily available in many research groups. Therefore, it would be interesting to propose a methodology to characterize and compare the printability of different hydrogels in a fast, simple, reliable, and inexpensive way. The aim of this work is to propose a methodology for extrusion-based bioprinters that allows determining the printability of hydrogels that are going to be loaded with cells, by analyzing cell viability with the sessile drop method, molecular cohesion with the filament collapse test, adequate gelation with the quantitative evaluation of the gelation state, and printing precision with the printing grid test. The data obtained after performing this work allow the comparison of different hydrogels or different concentrations of the same hydrogel to determine which one has the most favorable properties to carry out bioprinting studies.

Electrochemical, Biological, and Technological Properties of Anodized Titanium for Color Coded Implants.

Anodization coloring of titanium tools or implants is one of the common methods for the differentiation of each application by its size or type. Commercial purity titanium grade 4 plates (50 × 20 × 0.1 mm) were tested to obtain their electrochemical and other technological properties. The coloring process was done using the potential of 15, 30, 45, 60, and 75 Volts for 5 s in 1 wt. % citric acid in demineralized water solution. Organic acids solutions generally produce better surface quality compared to inorganic acids. The contact angle of colored surfaces was measured by the sessile drop method. Electrochemical impedance spectroscopy and potentiodynamic polarization were used for the determination of selected electrochemical and corrosion parameters of the tested surfaces. It was found that the anodization process decreases corrosion potential significantly. It was also confirmed that a higher potential used for anodization results in higher polarization resistance but also a decrease in corrosion potential. The anodization process at 75 V produces surfaces with the lowest corrosion rate under 1 nm/year and the noblest corrosion potential. It was confirmed that the anodization process in citric acid does not affect titanium cytotoxicity.

SURFACE TENSION AND DENSITY OF INDIUM–TIN MELTS AND THEIR DEPENDENCE ON COMPOSITION AND TEMPERATURE

The paper presents the results of measuring the surface tension (σ) and density (ρ) of indium-tin melts. The measurements of σ and ρ were carried out by different methods. The surface tension was measured by the sessile drop method and the maximum pressure in the droplet, while the density was measured by the areometer and sessile drop methods. High-purity metals In-00, tin – VHF were used for research. The maximum measurement error σ is 0.8%, and ρ is 0.2%. The dependence of σ of In–Sn melts on the composition is characterized by an extremum (flat minimum) in the region of equimolar composition. As the temperature increases, the depth of the minimum decreases, and its position shifts towards pure indium. Molar volumes have small positive deviations from additive values. As the temperature increases, the molar volumes approach additive values. The sessile drop method was used to measure the temperature dependences of σ and ρ of In–Sn solutions diluted with indium. It has been shown that indium additives lower the surface tension of tin. Given that the value of the surface tension of indium is higher than that of tin, this result indicates that the surface tension isotherms of the indium-tin system must pass through a minimum.

Leaf Wettability Difference Among Tea Leaf Ages and Analysis Based on Microscopic Surface Features

The wettability of leaf surface, commonly represented by contact angle (CA), affects various physiological and physical processes. The present study aims to better understand the wettability of tea leaves and elucidate its influence on the energy barrier of the droplet condensation process. The CA values of different leaf ages (young, mature and old) of five famous tea cultivars (Maolu, longjing 43, Huangjinya, Zhongcha 108 and Anji Baicha) were measured via the sessile drop method, and the micro-morphology of two cultivars leaves (Maolu, Zhongcha 108) was investigated by a 3D super depth-of-field digital microscope. Specifically, two radically distinctive types of CA trends were observed, one was the decreased firstly and then increased slightly with the increase of leaf age, while the other stayed constant. The valley depth or maximum height (RZ) of Maolu leaf surface increased with the leaf age while the RZ of Zhongcha 108 leaf remained unchanged by comparing the microscopic features. The Maolu mature leaf CA decline attributed to the young leaf was hydrophilic (θ < 90°), and it was considered that surface structures like folds and pits on old leaf played a crucial role in making CA increased. Small deviation in CA can lead to significant error in calculation of the contact angle function of energy barrier in phase change. It will have great significant for simulating and better understanding the formation of frost on tea leaves.

Process optimization for fabrication of PVDF - TiO2 hydrophobic membrane using phase inversion method for desalination application using VMD

The properties of membranes are significantly influenced by process parameters. To understand the impact of operating parameters on membrane characteristics, a design of experiments was conducted using response surface methodology (RSM). The gradient descent method was employed to determine the optimal conditions for desired membrane characteristics. This study involved the preparation of a hydrophobic flat sheet membrane made of Polyvinylidene fluoride (PVDF) using central composite design (CCD) arrays. The operating variables considered for developing the PVDF flat sheet hydrophobic membrane were polymer concentration, additive concentration, evaporation time, and ethanol concentration in the coagulation bath. The responses, such as contact angle, membrane porosity, and tensile strength, were measured using the sessile drop method, gravimetric method, and universal testing machine. Nonlinear regression models were developed for contact angle, porosity, and tensile strength using minimization of the sum of square errors in CCD, which were found to be in good agreement with experimental data. The results indicated that polymer concentration had the highest synergistic influence on the surface contact angle, but had an antagonistic effect on membrane porosity. The tensile strength of the fabricated membrane increased with polymer concentration but declined with additive concentration. It was important to determine the optimal conditions for the trade-off between the operating parameters and membrane characteristics. The theoretical desired membrane characteristics were determined to be 109 ± 2°, 59.9 ± 2%, and 78.7 ± 1 MPa under optimal conditions of 16.0 wt% polymer concentration, 1.676 wt% TiO2 concentration, 29.09 min of evaporation time, and 39.59 wt% coagulation bath concentration. The experimental values of membrane characteristics under optimal conditions were measured to be 108.2 ± 2°, 58.9 ± 2 %, and 77.3 ± 1 MPa. The fabricated membrane was employed for desalination using vacuum membrane distillation.

Comparative analysis of the biocompatibility of endothelial cells on surfaces treated by thermal plasma and cold atmospheric plasma.

In recent years, cold atmospheric plasma (CAP) is used for surface disinfection. However, little is known about its ability to improve biocompatibility of metallic surfaces when compared to thermal plasma methods. In this context, the study aimed to evaluate the response of human endothelial cells (Ea.hy926) on titanium surfaces treated by non-thermal plasma method and thermal plasma method under nitriding atmosphere. The wettability was characterized by the sessile drop method, the topography and roughness were evaluated by atomic force microscopy (AFM), and the microstructure by grazing angle X-ray diffraction (GIXRD). Endothelial cells were cultured and evaluated for morphology by scanning electron microscopy and viability by an MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay. CAP treatment reduced the contact angle of the Ti surface (13.43° ± 1.48; p<0.05), increasing hydrophilicity. Rz roughness was higher on the nitrided surface (220.44±20.30; p< 0.001) compared to the CAP treated surfaces (83.29 ± 11.61; p< 0.001) and polished (75.98 ±34.21a); p<0.001). The different applied plasma treatments created different titanium surfaces improving the biocompatibility of endothelial cells, however CAP results demonstrate its potential for biomedical applications, considering the low cost and ease of use of the technique, allowing surface treatments before clinical procedures.

Surface free energy and roughness of flowable dental composites

Purpose The surface properties like roughness, wettability and surface free energy are important for utility properties of traditional and flowable dental restorative composites, due to their role in plaque formation, discoloration, mechanical wear or adhesion and bonding. The goal of our work was to assess the surface free energy (SFE) and the surface roughness (Ra) of three commercial flowable dental composites: everX Flow (bulk), everX Flow (dentin) and Flow-Art. Methods Surface roughness, contact angle and surface free energy were determined for tested composites. Two surface states (control and roughened) were compared. Roughness was measured with the use of the 3D optical profilometer. The contact angle (CA) was determined through the sessile drop method with the use of four different probing liquids. This enabled to apply two surface free energy approaches (Owens–Wendt (O-W) and van Oss–Chaudhury–Good (LWAB)). Additionally, Zisman’s approach (γC) was used. Results The water contact angle values were similar for Flow-Art (67.56±1.49°) and everX Flow (bulk) (68.94±2.72°) compared to higher value for everX Flow (dentin) (74.39±2.05°). SFE was in the range from 43 to 50 mJ/m^2 for O-W and from 47 to 62 mJ/m2 for LWAB. The γC was from 37 to 45 mJ/m^2. Conclusions Roughening composites’ surface influenced on increasing the CA value. All approaches of surface free energy calculations provide useful data for predicting interactions between flowable composites and dental tissues. Tested composites showed good wetting for initial state of surface after polymerization. These influence on better adhesion of the material to the bonding system during dental restoration.

Wettability alteration and surfactant adsorption study of methyl ester sulphonate/nano-silica nanofluid on sandstone reservoir rock

This research project set out to investigate low salinity water/Methyl Ester Sulphonate (MES) surfactant/nano-silica synergy to enhance oil recovery from sandstone reservoir. A Series of experimental works, including contact angle measurements (Sessile drop technique) and UV-vis spectrophotometer tests, were conducted to ascertain the effect of the synergy solution on wettability alteration and surfactant adsorption reduction. Results showed that MES surfactant at 750 ppm and 1000 ppm reversed oil-wet sandstone to a water-wet state. Further reduction was observed at low salinity (250 ppm CaCl 2 ) under high pH conditions. The lowest contact angle measured was 18 degrees with the synergy solution of 750 ppm MES and 250 ppm CaCl 2 at high pH conditions. The maximum adsorption capacity was used as criteria to measure surfactant adsorption loss reduction. It was observed that surfactant adsorption capacity reduced from 4.66 mg/g to 0.85 mg/g when 25 ppm nano-silica was added at 70℃ temperature. This shows that the synergy was able to restore wettability to preferable water-wet conditions to support oil recovery and reduce the excessive loss of surfactant to the sandstone reservoir rock. Water-wet wettability condition and surfactant adsorption reduction are beneficial to the c-EOR project in terms of efficient cost savings on the quantity of surfactant usage for the project. At the same time, overall additional oil recovery is greatly improved.

Durability and wettability of varnishes on the modified and aged surfaces of short rotation teak wood

PurposeThe surface characteristics of thermally and chemically modified wood, such as surface roughness, surface free energy (SFE) and wettability, are important properties that influence further manufacturing processes such as gluing and coating. The aim of this paper was to determine the influence of the surface roughness of thermally and chemically modified teak wood on their SFE, wettability and bonding quality for water-based acrylic and solvent-based alkyd varnishes. In addition, durability against subterranean termites in the field of these modified teak woods was also investigated to give a valuable information for their further application.Design/methodology/approachThe woods tested in this study were fast-growing teak woods that were prepared in untreated and treated with furfuryl alcohol (FA), glycerol maleic anhydride (GMA) and thermal. SFE values were calculated using the Rabel method. The wettability values were measured based on the contact angle between varnish liquids and wood surfaces using the sessile drop method, and the Shi and Gardner model model was used to evaluate the wettability of the varnishes on the wood surface. The bonding quality of the varnishes was measured using a cross-cut test based on ASTM 3359-17 standard. In addition, durability against subterranean termites in the field of these modified teak woods was also investigated according to ASTM D 1758-06.FindingsThe results showed that furfurylated and GMA-thermal 220°C improved the durability of teak wood against termites. The furfurylated teak wood had the roughest surface with an arithmetic average roughness (Ra) value of 15.65 µm before aging and 27.11 µm after aging. The GMA-thermal 220°C treated teak wood was the smoothest surface with Ra value of 6.44 µm before aging and 13.75 µm after aging. Untreated teak wood had the highest SFE value of 46.90 and 57.37 mJ/m2 before and after aging, respectively. The K values of untreated and treated teak wood increased owing to the aging treatment. The K values for the water-based acrylic varnish were lower than that of the solvent-based alkyd varnish. The untreated teak wood with the highest SFE produced the highest bonding quality (grades 4–5) for both acrylic and alkyd varnishes. The solvent-based alkyd varnish was more wettable and generated better bonding quality than the water-based acrylic varnish.Originality/valueThe originality of this research work is that it provides evaluation values of the durability and SFE. The SFE value can be used to quantitatively determine the wettability of paint liquids on the surface of wood and its varnish bonding quality.

Production of nanoparticles from resistant starch via a simple three-step physical treatment

The purpose of this study was to physically process Hi-maize 260® granules and investigate the size reduction towards obtaining starch nano-particles, stable in aqueous suspensions. We developed a novel sequential three-step physical process consisting of hydrothermal gelatinization, nano-precipitation and ultrasonic treatment. Ultrasonication proved to be a key-step to dismantle the ununiform agglomerates nanoparticles produced by the nanoprecipitation of the hydrothermally gelatinized starch, furnishing uniform nanoparticles (170 nm). This was unveiled by complementary Dynamic Light Scattering (DLS) and electrophoretic mobility (Z-potential) studies, as well as fluorescence spectroscopy. Notably, this 3-step process reduced the size of the starch particles to nano dimensions without destroying their crystallographic structure, as shown by X-ray diffraction (XRD) and Small Angle X-ray Scattering (SAXS), or changing. their chemical integrity, as validated by Fourier transform infrared spectroscopy (FTIR) and Thermogravimetric Analysis (TGA) analyses. Finally, we evaluated the hydrophobicity of the isolated nanoparticles by employing the sessile drop method, witnessing an increment to the hydrophobicity as a result of size reduction. Collectively, we developed a handy protocol enroot to reduce the size of RS2 starch particles enabling its application in an array of meaningful real-world food applications.

Non-Wetting and Non-Reactive Behavior of Liquid Pure Magnesium on Pure Tungsten Substrates.

The wetting behavior of liquid magnesium drop on pure tungsten substrates was investigated, for the first time, with the sessile drop method combined with non-contact heating and capillary purification of a Mg drop from a native oxide film. A specially designed apparatus dedicated to the investigation of the high-temperature interaction of dissimilar materials was used. The comparative experiments were performed under isothermal conditions at temperatures of 700 °C and 740 °C using two atmospheres: Ar + 5 wt.% H2 and pure Ar, respectively. During high-temperature tests for 180 s, the images of the Mg/W couples were recorded with CCD cameras (57 fps) from two directions of observation. The solidified drop/substrate couples were subjected to structural characterization using scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS). Under the applied measurement conditions, liquid Mg revealed non-wetting behavior on W substrates (a contact angle θ &gt; 90°). The average value of the contact angle under the flowing Ar atmosphere at 740 °C was θav = 115°, whereas it was higher under the flowing Ar + 5 wt.%. H2 atmosphere at a lower temperature of 700 °C, showing θav = 122°. Independently on employed atmosphere and temperature, SEM + EDS analysis of solidified sessile drop couples did not display any new phases and mass transfer between the Mg drop and the W substrate, whereas the presence of discontinuities at the Mg/W interface of cross-sectioned couples were well-distinguished. Non-wetting and a lack of permanent bonding between the Mg drop and W substrates have a good agreement with the Mg-W phase diagram calculated with the help of FactSage software and FTlite database, i.e., the non-reactive nature of the Mg/W couple because W does not dissolve in liquid Mg and it does not form any compounds with Mg. These findings allow for the recommendation of tungsten as a suitable refractory material for long-time contact with liquid Mg in different container-assisted methods of materials characterization as well as in liquid-assisted processing of Mg components.

Experimental basis for determining contact angle in the ideal model of unsaturated soils

In an ideal unsaturated soil model, the contact angle (CA) is often determined by the sessile drop method (SDM), or assumed without any test. However, both approaches can lead to errors in the model calculation results. In this study, methods that combine models of unsaturated soil with CA measurement methods is presented. The characteristics of soil CA were studied using the sessile drop method (SDM) and the direct observation method (DOB). The results demonstrated that the CA values of soils and CA variation characteristics measured with SDM were significantly different from those measured with DOB. SDM measures the CA of a surface, which is a “plane” formed by many particles, whereas DOB measures the CA between soil particles on a smaller scale. The measurement results of SDM can determine the degree of soil hydrophobicity but may cause large errors when used as a parameter of an ideal unsaturated soil model. The DOB can simulate the natural drying-wetting cycles of soils, and its measurement results are closer to the natural conditions. Using the mean CA as a model parameter is reasonable, except when the CA value is 0. The hysteresis phenomenon caused by using CA hysteresis for the soil-water characteristic curve (SWCC) is likely to overestimate the effect of CA hysteresis on soil water retention behavior.

Wetting of Refractory Ceramics with High-Manganese and Structural Steel and Description of Interfacial Interaction

This work aims to describe the interfacial interaction at the interface between refractory material and high-manganese (XT 720) and structural (11 523) steel using a wetting test up to 1600 °C. The contact angles were determined through the sessile drop method, and the results were put into context through degradation testing and the characterization of the interfacial interface by Energy Dispersive X-Ray (EDX), X-Ray Diffraction (XRD) analyses, and Scanning Electron Microscopy (SEM). The lowest resistance to molten steel was observed for chamotte materials, while the highest was observed for materials based on electrofused corundum. High-manganese steel was strongly erosive to the materials tested, with the wetting angle decreasing significantly from 10 to 103° with decreasing Al2O3 content (an increase of 2.4 to 59.4% corundum) in the refractories. Structural steel showed wetting angles from 103 to 127° for identical refractories. These results were consistent with the average erosion depth for Mn steel (0.2–7.8 mm) and structural steel (0–2.4 mm).

Effect of Antimony on Wetting Behavior and Interfacial Reaction between Zinc Liquid and X80 Steel

The wetting behavior of molten Zn and Zn-Sb alloy and X80 steel in a high vacuum environment was studied by the modified sessile drop method. The wetting morphology and interface structure were analyzed by scanning electron microscope and energy dispersive spectrometer. The results show when the content of Sb in Zn-Sb alloy increases from 0.0 wt. % to 1.0 wt. %, the initial contact angle between the droplet and the substrate decreases from 102.8° to 82.5°, and the equilibrium contact angle also decreases from 57.4° to 41.4°. Sb element in the Zn-Sb alloy can reduce the contact angle and improve the wettability due to its smaller surface tension. The spreading process of Zn-Sb alloys on X80 steel can be divided into rapid adsorption, reaction control, steady-state equilibrium stages, and Zn-Sb alloys with different mass fractions have the same spreading kinetics. The volatilized Zn element in the Zn-Sb alloy will reduce the oxide film on the surface of the substrate, making it easier for the Zn-Sb droplet to wet the steel plate and induce the formation of a precursor film. The formation mechanism of the precursor film is the subcutaneous penetration mechanism.

Модифікація поверхні базальтових волокон та вуглецевих матеріалів для покращення їх змочування легкоплавкими розплавами

The effect of metal coatings and coverings on wetting of substrates by In, Sn, Pb in vacuum 1—2•10-3 Pa in the temperature range 400—700 C was studied by the sessile drop method using the capillary purification method of melt. Substrates of hot-polished basalt material, MPG-6 graphite, composite materials based on high-modulus carbon fibers, tapes and fabrics used. Vanadium, niobium, copper and nickel metals were chosen for the coatings, which were sprayed on the materials by electron beam evaporation of metals in vacuum, and titanium, nickel powders for the coatings were used. The nature of the wetting angle dependence on the film thickness is a linear decrease in the angle with increasing film thickness. Studies have shown the possibility of using double films V—Cu, V—Ni for the manufacture of composite materials from basalt fibers.Wetting the vanadium and niobium coatings on surface of the basalt material at by lead, tin and indium improves with increasing film thickness and experimental temperature. The nature of the contact angle–coating thickness dependences for all studied systems is the same: the angle value decreases linearly with increasing film thickness from the angle wetting of the basalt surface to the wetting angle of the compact metal film (V, Nb). The coating thickness, when the contact angle wetting for all adhesive-active metals with high oxygen affinity does not change, is close, and for vanadium is 200•10-10 m, for niobium about 100•10-10 m. Studies have shown the possibility of using double V—Cu and Nb—Cu films for the manufacture of composite materials from basalt fibers and matrix metal. Keywords: contact angle wetting, metal coatings and covering, basalt and carbon materials, low-melting metals.

An effective laser surface treatment method to reduce biofilm coverage of multiple bacterial species associated with medical device infection

Device associated infection (DAI) is recognized as a worldwide health challenge in total joint replacement (TJR). Bacteria exhibit very strong antibiotic tolerance when they attach to a device and form a biofilm and thus DAI is difficult to treat. In this study, a one-step, clean (no chemicals or additional materials involved) and effective surface engineering approach via laser surface treatment (LST) to tackle the DAI challenge is reported. Commercially pure (CP) Ti were laser-treated in open air using continuous wave (CW) fibre laser. The laser-treated CP Ti was tested against five bacterial species including Gram positive (Staphylococcus aureus and Staphylococcus epidermidis) and Gram negative (Pseudomonas aeruginosa, Escherichia coli and Proteus mirabilis). Live/Dead staining and image analysis results indicated that LST can significantly reduce biofilm coverage of the five tested bacterial species on the CP Ti surfaces. Overall biofilm coverage as a percentage of the surface reduced after laser treatment averaging from 4.24 % to 17.4 %. This meant that relative to the untreated surface, biofilm coverage was reduced after laser treatment, ranging from 84.9 % to 95.6 % across the five species. Furthermore, cytotoxicity results (using MTT assay) showed that the laser-treated CP Ti is non-toxic across both L929 fibroblast and RAW macrophage cell lines. Surface properties after LST were investigated using WLI and AFM (measuring micro-/nano-surface roughness and topography) as well as ToF-SIMS (measuring surface chemistry and oxide thickness), respectively. The cross-sectional microstructure at the surface was imaged using SEM and analysed by XRD, whilst the surface wettability was measured using sessile drop method. To summarise, the reduction of biofilm coverage can be attributed to the favourable changes in surface roughness and topography together with the increased concentration of oxides at the topmost surface after LST.

A Method for the Immobilization of Chitosan onto Urinary Catheters

A method for the immobilization of an antibacterial chitosan coating to polymeric urinary medical catheters is presented. The method comprises a two-step plasma-treatment procedure, followed by the deposition of chitosan from the water solution. In the first plasma step, the urinary catheter is treated with vacuum-ultraviolet radiation to break bonds in the polymer surface film and create dangling bonds, which are occupied by hydrogen atoms. In the second plasma step, polymeric catheters are treated with atomic oxygen to form oxygen-containing surface functional groups acting as binding sites for chitosan. The presence of oxygen functional groups also causes a transformation of the hydrophobic polymer surface to hydrophilic, thus enabling uniform wetting and improved adsorption of the chitosan coating. The wettability was measured by the sessile-drop method, while the surface composition and structure were measured by X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. Non-treated samples did not exhibit successful chitosan immobilization. The effect of plasma treatment on immobilization was explained by noncovalent interactions such as electrostatic interactions and hydrogen bonds.

Influence of Fluorine and CaO/Al2O3 Ratio on the Wetting Behavior Between CaO–Al2O3‐Based Mold Flux and Steel Substrate

The wetting behavior of flux melt on the initial solidified shell greatly determines the slag entrapment in the casting product and the sliver defect in the rolled product. Herein, the wetting behavior of CaO–Al2O3‐based mold flux with various fluorine (F) contents and CaO/Al2O3 (C/A) ratio on steel substrate is studied using the sessile drop method. Results show that the contact angle decreases from 71.35° to 59.86° and from 65.96° to 22.73°, meanwhile, the interfacial tension decreases from 1743.02 to 1669.69 mN m−1 and from 1705.40 to 1448.53 mN m−1, with the addition of F and the increase of C/A ratio, respectively. X‐ray photoelectron spectroscopy analysis indicates that the addition of F and increase of C/A ratio lead to positive adsorption () of non‐bridging oxygen (O−) and free oxygen (O2−) at the interface, which is the main reason why the interfacial tension between the mold flux and steel is reduced and the wettability of flux droplet on the steel is enhanced.