Sessile Drop Method Research Articles

Synthesis, Self‐Aggregation, Interfacial Behavior and Interaction Studies of Non‐ Cytotoxic Caffeinium‐Based Surface Active Ionic Liquids with Sodium Dodecyl Sulfate

Caffeinium-based surface-active ionic liquids (SAILs), (1-(2-alkanoyl oxy) ethylcaffeinium bromide), [CnEcaf]Br with variable chain length (n=12, 14, 16) were synthesized and their molecular structures were explored by multiple spectral techniques. The critical micelle concentration (CMC) of pure SAILs and their mixtures with sodium dodecyl sulfate (SAIL-DS) in aqueous solution was determined by employing various techniques at 298 K. The tensiometry and dynamic light scattering (DLS) techniques have been employed to gain insight about the interfacial behavior and aggregate size of cat-anionic mixtures in aqueous solution. Interestingly, the interaction parameters ( ) showed strong synergism between these two oppositely charged molecules. Further, it was found that SAIL-DS cat-anionic mixtures exhibit excellent adsorption efficacy and are more effective in lowering the surface tension of water as compared to pure SAILs. The DLS results showed the formation of mixed-size aggregates in SAIL-DS systems. The contact angle and wetting properties of pure SAILs over the parafilm surface were also determined using a static sessile drop method. Further, MTT assay was used to determine the biocompatibility of SAILs on Human embryonic kidney (HEK-293) cell line and in-vitro anti-cancer activity on Lung cancer cells (A549). These SAILs displayed substantial cytotoxicity against cancerous cells, indicating that they could be useful in a variety of biological applications.

Wetting and interfacial interaction of molten iron on MgO substrate under different oxygen partial pressures

The interaction between molten iron and refractory is of great significance to understand the damage of refractory in steelmaking processes. In this work, the interactions between the molten iron and three kinds of magnesia aggregates: No. 1 containing CaZrO3-ZrO2 intergranular phase (mainly CaZrO3), No. 2 containing ZrO2-MgAl2O4 intergranular phase (mainly ZrO2) and No. 3 fused magnesia, were studied by the sessile drop method at 1823 K under two kinds of oxygen partial pressures of PO2 ≈ 1.87 × 10−1 Pa and PO2 ≈ 1.87 × 10−3 Pa. It was found that the interaction mechanism between molten iron and substrate was almost the same under the two oxygen partial pressures. No. 2 substrate had a larger interacted area with molten iron due to its physical properties and chemical composition and more amount of slag was formed between them. The oxygen was easy to be released from the closed pores in No. 2 substrate so that the molten iron on No. 2 substrate had higher oxygen content, resulting in the decreases of the contact angle and the surface tension of molten iron. Accordingly, No. 2 substrate was penetrated most seriously. The intergranular phase of No. 1 substrate was more resistant to FeO corrosion than that of No. 2 substrate. The FeO penetration into No. 3 substrate was mainly along the grain boundary. The larger bulk density and grain size of No. 3 substrate could reduce the FeO penetration.

Marangoni flow patterns of molten pools in multi-pass laser cladding with added nano-CeO2

Adding rare-earth elements has been proven to modify the microstructure and enhance the mechanical properties of the laser cladding layer. However, the effect of such elements on the flow pattern in molten pools has not been extensively determined, especially for multi-pass laser cladding. The surface tension of T15 high speed steel and nano-CeO 2 mixed powders is measured using the sessile drop method. Comparing the results from the high-speed photography of the molten pool flow and the multicomponent multiphase flow model, various Marangoni flows driven by surface tension are elucidated, and the cross-section of the multi-pass cladding is further analyzed. The surface tension increases with increasing CeO 2 content. When CeO 2 is less than 0.6 wt%, the surface tension monotonically increases with increasing temperature, and the molten pool flows inward. When CeO 2 is greater than 0.6 wt%, the surface tension decreases at high temperatures, and the molten pool exhibits double flows. In multi-pass laser cladding, the inclination of the molten pool increases on adding CeO 2 . Consequently, the inclined angle of the cladding pass interface increases, and the fusion line on the substrate tends to be straightened. At 0.9 wt% CeO 2 , the added powders remain at the center of the molten pool because of a low velocity, creating a low-temperature zone. The temperature coefficient of surface tension demonstrates a positive–negative–positive distribution from the center to the surrounding pool surface, thus forming an outflow. The solidus point of the cladding alloys is lower than that of the substrate, resulting in a small indentation at the remelted region between passes, which increases the interfacial zone. • Flow in multi-pass molten pool changes from inward to outward with CeO 2 addition. • Surface tension curve drops at high temperature with CeO 2 composition above 0.6 wt%. • A low velocity and temperature zone forms in the center of molten pool at 0.9 wt% CeO 2 . • Fusion interface matching with experiments is dominated by flow and solidus point.

Impact of nanoparticles–surfactant solutions on carbon dioxide and methane wettabilities of organic-rich shale and CO2/brine interfacial tension: Implication for carbon geosequestration

Rock wetting behaviour and CO2/brine interfacial tension (IFT) have significant impacts on enhanced hydrocarbon recovery (EOR) and carbon geo-sequestration (CGS) projects. Influence of nanoparticles/surfactant solutions (NPS) flooding on EOR and CGS in sandstone and carbonate formation have been examined in recent studies. But the impact of NPS on carbon dioxide (CO2) and methane (CH4) wettabilities of organic-rich shale and CO2/brine IFT is presently unclear. Thus, we measured contact angles, [advancing (θa) and receding (θr)] for CO2/brine and CH4/brine on Marcellus shale with high total organic carbon (14.8 wt%), as well as CO2/brine IFT with Krüss drop shape analyzer (DSA 100) through the sessile drop and pendant drop techniques. Prior to IFT and contact angles measurement, the shale samples were aged in NPS solutions to evaluate the impact of NPS treatment on CO2 geo-storage. Low-cost rice husk silica nanoparticles and saponin surfactant were used for the study due to their environmental friendliness and economic attractiveness. At geo-storage conditions (25 MPa and 353 K), the advancing contact angle of untreated shale was measured as θa=116.22° (CO2-wet condition), whereas the receding contact angle was measured as θr=82.88° (near neutral wettability). However, θa reduced by 56.34° whereas θr reduced by 56.76° when the shale substrate was treated with 0.1 wt% SiO 2 and 0. 2 wt% saponin solutions. CO2/NPS IFT were lower than CO2/brine IFT and the CH4 wettability of the Marcellus shale was significantly lower than the CO2 wettability at all investigated conditions. Contact angles decreased with temperature and increased with CO2/CH4 pressure, whereas CO2/NPS IFT exhibited an opposite trend. The reduction in contact angles and CO2/brine IFT by NPS have significant impacts on adsorption trapping of CO2 in organic-rich shale and hydrocarbon recovery from unconventional shale reservoirs.

Probing Surface and Interfacial Tension of Ionic Liquids in Vacuum with the Pendant Drop and Sessile Drop Method.

We report on the surface and interface tension measurements of the two ionic liquids (ILs) [C8C1Im][PF6] and [m(PEGn)2Im]I (n = 2, 4, 6) in a surface science approach. The measurements were performed in a newly developed and unique experimental setup, which allows for surface tension (ST) measurements using the pendant drop method and for contact angle measurements using the sessile drop method under the well-defined conditions of a high vacuum (from 10-7 mbar). The setup also allows for in vacuum transfer to an ultrahigh vacuum system for surface preparation and analysis, such as in angle-resolved X-ray photoelectron spectroscopy. For [C8C1Im][PF6], we observe a linear decrease in the surface tension with increasing temperature. The ST measured under high vacuum is consistently found to be larger than under ambient conditions, which is attributed to the influence of water uptake in air by the IL. For [m(PEGn)2Im]I (n = 2, 4, 6), we observe a decrease in the ST with increasing polyethylene glycol chain length in a vacuum, similar to very recent observations under 1 bar Argon. This decrease is attributed to an increasing enrichment of the PEG chains at the surface. The ST data obtained under these ultraclean conditions are essential for a fundamental understanding of the relevant parameters determining ST on the microscopic level and can serve as a benchmark for theoretical calculations, such as molecular dynamic simulations. In addition to the ST measurements, proof-of-principle data are presented for sessile drop measurements in HV, and a detailed description and characterization of the new setup is provided.

Anodic Aluminum Oxide(AAO)-Based Chemi-Capacitive Sensor Toward Ethanol Gas

The transducer elements for such sensor arrays need to be small, low-power, and compatible with conventional microprocessing technology. The transducers include chemiresistive gas sensor, FET gas sensor, capacitive gas sensor, and inductive gas sensor. Of these transducers, chemicapacitors and chemiresistors are the best suited for low-power sensor arrays. The change of electrical properties such as conductance or capacitance upon exposure to analytes can be used to detect chemical and biological agents, respectively. Chemiresistors are simply implemented in many application fields, but they have disadvantages such as instability and cross sensitivity. Whereas chemicapacitors are known to provide superior sensitivity and recovery time because capacitance can response to very thin layers of chemoselective material down to a single molecular monolayer, resulting in the elimination of the duration time for capacitance change. In this work, the room-temperature capacitive ethanol gas sensing properties of AAO (anodic aluminum oxide) were studied and the underlying mechanisms were analyzed based on its electrode configuration and detection frequency. Figure 1 shows the progress of the experimental progress according to each electrode patterns and thicknesses.The sensor sensitivity of the chemocapacitive sensor toward ethanol was affected by the humidity because it has higher dielectric constant than ethanol. Therefore, the surface treatment of AAO was carried out by silanization using APTES and HMDS. The degree of hydrophobicity of AAO surface was determined by measuring the water contact angle by the Sessile Drop method. After surface treatment was performed in each method, the sensitivity of the sensor to the wet air was also measured.Through silanization, similar sensor sensitivity to ethanol was obtained, and at the same time, sensor sensitivity to wet air was minimized as illustrated in Figure 2. In this study, the sensor characteristics were optimized by the electrode pattern and thickness, and the gas selectivity of the sensor was improved through surface treatment. Figure 1

Crushed Glass and Oil Extracted from Palm Oil Sludge as Primary Materials in the Production of Hydrophobic Sand for Capillary Barrier Applications

Hydrophobic-coated sand causes a reduction in infiltration, making it suitable for hydrophobic capillary barriers. Borosilicate glass waste was crushed into a synthetic sand 180 µm average, and fatty acids (PFA) were extracted from palm oil sludge. The synthetic sand was coated with PFA using mixing (POS-M) and solvent-assisted (POS-S) methods with stearic-acid-coated sand (SA) as a standard at concentrations varying from 1 to 16 g/kg. Contact angle measurements were undertaken by applying the sessile drop method. The water holding capacity of POS-M and SA were determined, and hydraulic conductivity curves were estimated with the van Genuchten model. Finally, a qualitative assessment of POS-M’s effectiveness as a capillary barrier was performed using a set of micro-tensiometers. Maximum contact angles for POS-M, POS-S, and SA were 119.73°, 118.83°, and 107.48°, respectively, and the saturated hydraulic conductivity of hydrophobized sands showed an exponential change of minus 2. Saturated conditions above the capillary barrier and unsaturated underneath were observed. In conclusion, the results indicate that the zero-waste approach applied through the reuse of solid waste from glass and palm oil production can be a waste management alternative in the production of hydrophobic sands that can be used in hydrophobic capillary barrier applications.

Effect of surfactant content on rheological, thermal, morphological and surface properties of thermoplastic starch (TPS) and polylactic acid (PLA) blends

Miscibility in biopolymeric blends is a critical process that requires evaluation of the effect of surfactants or coupling agents under conditions similar to processing. Different mixtures in the molten state of plasticized starch and polylactic acid in the presence of a surfactant (Tween 20) at different concentrations were studied. This allowed knowing the rheological, thermal and surface behavior of the mixtures. The results of the dynamic rheological analysis showed increases in viscosity in the presence of the surfactant, in which strong interactions were produced at high shear rates that reflect possible crosslinking between the polymer chains, in addition to intermolecular interactions that were evidenced in the infrared spectrum. Likewise, the storage and loss modulus showed transitions mainly from viscous to elastic typical for thermoplastics. The thermogravimetric analysis did not show significant changes between the mixtures. However, the calorimetric analysis showed changes in the crystallinity of the mixtures, the tensoactive promotes greater freedom of movement and rearrangements in the microstructure with decrease of interface between polymers, and less compaction of the material induced by the emulsion. Analysis derived from biopolymeric films against contact with water shows significant changes. Interaction with water in short times (in the order of minutes) according to the sessile drop technique, favors hydrophilicity by increasing the concentration of Tween 20. However, interaction with water for prolonged times (in the order of hours), shows that the absorption reaches saturation in samples a stabilization in the absorption is observed. The results demonstrate that the miscibility of PLA in AS was achieved in the presence of the tween, under conventional processing conditions. The stability of the different formulations allows the production of films for packaging and biomedical applications.

Titanium Anodization in Psidium Guajava

Psidium guajava, commonly known as 'guava', belongs to the Myrtaceae family and is an alternative to the use of traditional methods of corrosion inhibition. The aim of this study is to anodize titanium in an environmentally friendly Psidium guajava electrolyte in order to improve its anti-corrosion performance. For this purpose, samples of CP (commercially pure) titanium grade 2 were anodized in plant extract based on Psidium guajava, with transient variations of current density (1 and 0.1 mA/cm²) and time (5, 30 and 60 min). Samples were characterized in terms of morphology by SEM (Scanning Electron Microscopy) analysis. The hydrophobicity of oxides was evaluated by the sessile drop method. Anodized samples were analyzed for colorimetry by the CIE L*a*b* method and the electrolyte based on Psidium guajava was analyzed by UV-Vis and cyclic voltammetry, in order to understand the compounds and their behavior in the anodizing process. From the obtained results, the oxides generated through anodization at current density of 0.1 mA/cm² were the ones that presented the best performance. The results obtained at 5 and 30 minutes of anodizing showed very similar results and greater reproducibility compared to the others analyzed, which showed the formation of a barrier-type oxide layer in the samples. In the Psidium guajava electrolyte, it was evidenced the presence of phenolic groups in its composition, which is believed to influence the process of formation of the oxide layer in the anodization process.

Discontinuous dewetting dynamics of highly viscous droplets on chemically heterogeneous substrates

HypothesisDroplet spreading on heterogeneous (chemical/structural) surfaces has revealed local disturbances that affect the advancing contact line. With droplet dewetting being less studied, we hypothesize that a receding droplet can be perturbed by localized heterogeneity which leads to irregular and discontinuous dewetting of the substrate. ExperimentsThe sessile drop method was used to study droplet dewetting at a wettability boundary. One-half of a hydrophilic surface was hydrophobically modified with either i) methyloctyldichlorosilane or ii) clustered macromolecules. A Lattice Boltzmann method (LBM) simulation was also developed to determine the effect of contact angle hysteresis and boundary conditions on the droplet dynamics. FindingsThe two surface treatments were optimized to produce comparable water wetting characteristics. With a negative Gibbs free energy on the hydrophilic-half, the oil droplet receded to the hydrophobic-half. On the silanized surface, the droplet was pinned and the resultant droplet shape was a distorted spherical cap, having receded uniformly on the unmodified surface. Modifying the surface with clustered macromolecules, the droplet receded slightly to form a spherical cap. However, droplet recession was non-uniform and daughter droplets formed near the wettability boundary. The LBM simulation revealed that daughter droplets formed when θR > 164°, with the final droplet shape accurately described by imposing a diffuse wettability boundary condition.

Adhesion Forces of Shale Oil Droplet on Mica Surface with Different Roughness: An Experimental Investigation Using Atomic Force Microscopy

In order to investigate the effect of rock surface roughness on the occurrence state of shale oil, muscovite mica was firstly characterized by performing atomic force microscopy (AFM). Two-dimensional (2D) images and the three-dimensional (3D) structure of the mica surface were obtained. Wettability of the micas was measured according to the sessile drop method using shale oil, collected from a lacustrine shale oil well drilling through the Yanchang Formation, Ordos Basin. Then, the adhesion forces between shale oil and mica surface with a different roughness were finely measured using AFM mounted with the shale oil modified probe tips. The adhesion force curves at the approaching and retract modes were obtained. The results show that the average roughness value of the mica samples was about 1 nm, while the maximum height was up to 4 nm. The contact angle between shale oil and mica ranged from 128.73° to 145.81°, and increased with increasing surface roughness, which can be described by the Wenzel model. The adhesion force between shale oil and mica also increased with an increasing contact area. Shale oil can fill the deep valleys on the rough surface of rocks and then form microscopic storage for oil droplets. The maximum adhesion force, reached at a distance of about 5–10 nm between shale oil droplets and micas, was between 14 and 30 nN. The adhesion force disappeared when the distance was larger than 40 nm. These indicate that shale oil in pores with a diameter of less than 10 nm was tightly adsorbed, and formed a layered accumulation pattern. Additional energy is needed to decrease the disjoining pressure and then separate shale oil from these tight pores. Shale oil is freely movable at pores with pore diameters of larger than 40 nm. This work provides a new insight about the interaction between shale oil and rock, and helps to understand the occurrence mechanism of shale oil.

The effect of surface roughness on capillary rise in micro-grooves

The capillary action is a unique feature of micro-grooves with numerous applications. This spontaneous flow eliminates the need for an extra pumping device to deliver a liquid. Capillary action depends on physical properties and features of the solid surface, as well as on thermophysical properties of the liquid. In this study, our previously proposed unifying capillary rise model is extended to include the effect of surface roughness. A new characteristic length scale is proposed that includes salient geometrical parameters, such as micro-grooves height, width, and surface roughness. Furthermore, it is shown that by using the proposed characteristic length scale, it can be determined whether the capillary action would occur in a given micro-groove and liquid. Various metallic and polymeric surfaces with a wide range of surface roughness are fabricated from aluminum, stainless-steel, natural graphite sheet, and 3D-printed stainless-steel and a polymer. A profilometer and sessile drop method are used to measure surface roughness and the contact angles, respectively. The present unifying model is compared against our measured data, and it is shown that it can predict the capillary rise in rough micro-grooves with less than a 10% relative difference. It is observed that the capillary height can be increased for a wetting surface by introducing surface roughness and by using optimal micro-groove cross-sections that are triangular as opposed to rectangular. The proposed compact, unifying model can be used to predict the capillary rise for any given micro-groove cross-section, and as a design tool for numerous industrial and biomedical applications, such as heat pipes, power electronic cooling solutions, sorption systems, medicine delivery devices, and microfluidics that utilize capillary micro-grooves.

Preparation of Cellulose Acetate Nanocomposite Films Based on TiO2-ZnO Nanoparticles Modification as Food Packaging Applications

To develop bio-packaging materials, nanocomposite films of cellulose acetate reinforced with titanium dioxide and zinc oxide nanoparticles were prepared, by the casting method at different weight ratios of ZnO nanoparticles (1.5, 2, and 2.5) wt% and a constant weight ratio of 2 wt% TiO2. ZnO and TiO2 nanoparticles were tested using scanning electron microscopy (SEM). The mechanical properties (tensile strength and elongation) were improved at a fixed level of Cellulose Acetate+ 2% TiO2+1.5wt% ZnO loading. Beyond that level of loading, they decreased. The tensile strength was decreased due to some degrees of agglomeration of filler particles above a critical content. Fourier-Transform Infrared Spectroscopy (FTIR) was conducted to reveal the microstructures and chemical composition of as-prepared composite films. The wettability of the films was also determined by the sessile drop method. An increase in contact angle was also observed by the addition of ZnO content from 70.6° to 77.1° compared to pure Cellulose Acetate, which indicated a value of 61.3°. Antibacterial activity against Escherichia coli and Staphylococcus aureus was enhanced after incorporation of ZnO-TiO2 compared with pure CA. The enhanced wettability and antibacterial activity of the prepared films suggest that they could be used for packaging applications.

Wetting of liquid Zinc-aluminum-magnesium alloy on steel substrate during hot-dipping: Understanding the role of the flux

The surface quality of hot-dipping Zn-Al-Mg coatings was significantly influenced by the composition of fluxes. In this study, five different fluxes were chosen and named as F1 (ZnCl2, NH4Cl), F2 (ZnCl2, NaF), F3 (ZnCl2, NH4Cl, KCl), F4 (ZnCl2, NH4Cl, KCl, SnCl2, HCl), and F5 (ZnCl2, NH4Cl, KCl, BiCl3, HCl). Using the sessile drop method, the influence of different fluxes on the wettability between the liquid Zn-Al-Mg alloy and the steel substrate was elucidated. The results showed that: when the flux composition is ZnCl2-NH4Cl-KCl-BiCl3-HCl, a uniform and dense salt film with a protective effect can be formed on the steel substrate, which prevents the oxidation of the steel substrate and removes the harmful reaction products during hot-dipping. By reducing the solid–liquid interface energy, increasing the work of adhesion between the liquid Zn-6Al-3Mg alloy and steel substrate, and shortening the interface reaction time, the strongest wetting effect between the liquid Zn-6Al-3Mg alloy and the steel substrate was achieved. The coating surface quality was the highest after using the F5 flux. Finally, the mechanism of the assistant plating is discussed.

Modifying geopolymer wettability by plasma treatment and high-carbon fly ash

This paper deals with investigation of changes in geopolymer wettability with increasing mass fraction of high-carbon fly ash and surface treatment by cold atmospheric plasma (CAP) to determine the influence of fly ash on wettability and whether it is a viable method to increase surface wettability for further surface treatment. In this study, multiple samples of geopolymers were prepared, including those with 16% and 32% of high-carbon fly ash from coal-fired power station. Wettability of samples was then measured before and after plasma treatment, both on surface and cut surface by using static sessile drop method to measure the differences in contact angle. While addition of fly ash only had low effect on the wettability, as in most cases, it only lowered the initial contact angle without speeding up the speed of soaking for compact geopolymer and actually slowed the soaking for foamed geopolymer, plasma treatment had significant impact and made the geopolymer completely hydrophobic, making plasma treatment a viable method to increase geopolymer wettability.

Nanostructuring Effect of Nano-CeO2 Particles Reinforcing Cobalt Matrix during Electrocodeposition Process.

The electrodeposition method was used to obtain nanostructured layers of Co/nano-CeO2 on 304L stainless steel, from a cobalt electrolyte in which different concentrations of CeO2 nanoparticles (0, 10, 20, and 30 g/L) were dispersed. The electrodeposition was performed at room temperature using three current densities (23, 48, and 72 mA cm−2), and the time was kept constant at 90 min. The influence of current densities and nanoparticle concentrations on the characteristics of the obtained nanostructured layers is also discussed. An X-ray diffractometer (XRD) was used to investigate the phase structure and cobalt crystallite size of the nanostructured layers, and a contact angle (sessile drop method) was used to assess the wettability of the electrodeposited layers. The roughness of the surfaces was also studied. The results show that the nanostructured layers became more hydrophilic with increasing nanoparticle concentration and increasing current density. In the case of pure cobalt deposits, an increase in the current density led to an increase in the size of the cobalt crystallites in the electrodeposited layer, while for the Co/nano-CeO2 nanostructured layers, the size of the crystallites decreased with increasing current density. This confirms the nanostructuring effect of nano-CeO2 electrocodeposited with cobalt.

Modification of cotton gauze by electrospinning of gelatin and honey biopolymer solution

In this study, bioactive nanofibers were fabricated using gelatin and honey via electrospinning method. Gelatin/honey solutions were fabricated using six blend ratios 95:5, 90:10, 85:15, 80:20, 75:25 and 70:30, respectively. Modern wound dressings, produced by electrospinning of new biopolymers, mimic the structure of skin due to their similarity to the Extracellular Matrix (ECM) fibrillar part, and have the appropriate biocompatibility and antimicrobial properties. Gelatin/honey solutions were electrospun on the cotton gauze for making a double layer dressing to mimic the skin layers. Morphology of gelatin nanofibers and gelatin/honey nanofibers was observed under Scanning Electron Microscope which showed bead-free nanofibers up to incorporation of 10 wt% honey. Electrospun gelatin/honey nanofibers were successfully obtained with average diameters ranging from 189.2 ± 66.2 nm to 323.7 ± 24.1 nm. The Fourier Transform Infrared spectrum illustrated successful incorporation of honey to the gelatin nanofibers. Water contact angle measuring was done with Sessile drop method, which proved hydrophobicity was increased by adding honey. The results suggest the potentials of the dual-layer nanofibrous membrane to use in dermal applications. Therefore, the developed gelatin/honey nanofibrous membranes are promising for wound dressings.

Evaluating wettability of vessels in poplar by Micro-CT imaging

Abstract The wettability of wood affects some natural phenomena and applications in industry, such as the ascent of sap in the plant stem, wood drying, and impregnation processes for wood modification. Wettability is generally evaluated by measuring the contact angle using techniques such as the sessile drop method and the Wilhelmy method. However, these methods are not applicable to phenomena at the micro-scale such as liquid transport in hardwood vessels. In this study, micro-CT was used to measure the contact angle of liquid in a single wood vessel directly at the submicron scale. The wettability of a wood vessel was analyzed using contact angles of distilled water and diiodomethane. Conventional contact angles of the wood surface were measured using a fixed drop technique. The average contact angle in a vessel determined by the direct CT observation was significantly smaller than that on the wood surface measured by the sessile drop technique. This discrepancy is attributable to the higher total surface energy of the vessel compared to the free energy of a flat surface. The difference in surface energy is due to different chemical composition distributions in various cell wall layers, roughness and surface topography between the wood surface and vessels, and moisture state.

Refractories for the processing of Fe–TiC alloy

In order to select the appropriate crucible material for Fe–TiC composite alloy processing, Al2O3, CaZrO3, and MgO-stabilized ZrO2 ceramic substrates were tested for interaction with a liquid Fe–TiC alloy at 1650 °C. The sessile drop method under protective gas was applied to conduct the experiment. The measured contact angle of Fe–TiC alloy followed the tendency of MgO-stabilized ZrO2˃CaZrO3˃Al2O3. After investigations, the Al2O3 substrate was strongly corroded by the liquid Fe–TiC alloy. The CaZrO3 substrate showed a smooth and non-corroded interface after the interaction. Reactions products TiOx and MgTiOx were detected between alloy and Mg–ZrO2 substrate. Obtained results were discussed under consideration of SEM/EDX analysis, which was conducted on the cross-section samples of metal/ceramic compound and on the top surface of the solidified Fe–TiC alloy; and of thermodynamic simulations of the Fe–TiC alloy interaction with the investigated substrates.

Design and synthesis of a new ionic liquid surfactant for petroleum industry

This study is intended to synthesize and assess a new pyridinium-based Ionic Liquid (IL) surfactant, 1-octadecyl-pyridinium bromide, in terms of crude oil–water Interfacial Tension (IFT) reduction and wettability alteration. The synthesized IL surfactant is firstly characterized through proton Nuclear Magnetic Resonance (1H NMR). Then, the pendant-drop and sessile drop techniques are employed to study crude oil–water IFT and the wettability of carbonate rocks. Based on the IFT results, the synthesized IL has a Critical Micelle Concentration (CMC) of 200 ppm, at which crude oil–water IFT reduces by 95.9 %, from an initial value of 23.7 mN/m to 0.97 mN/m. Increasing the salinity up to 100,000 ppm could not make the synthesized IL less effective than that of free from salinity, as the magnitude of IFT is obtained to be 0.938 mN/m at CMC. Based on the wettability investigation phase, the synthesized IL changes the wettability of carbonate slices from oil-wet to intermediate-wet (140.47°–90.97°). It is also observed that the synthesized IL can tolerate harsh salinity conditions as no appreciable change in the contact angle is noticed after increasing the salinity even up to 150,000 ppm (84.54° at CMC). It should be noted that an optimal salinity of 50,000 ppm is found based on the results of IFT and contact angle measurements. The introduced surfactant is expected to exhibit a significant positive impact on the oil recovery factor while implementing chemical flooding.