Calculation Of Contact Angle Research Articles

Molecular simulation of quartz wetting in crude oil / brine system at reservoir conditions using a novel protocol for contact angle calculation.

Molecular simulation of quartz wetting in crude oil / brine system at reservoir conditions using a novel protocol for contact angle calculation.

Exploring mechanisms of asymmetric droplet impact dynamics on roughness gradient surface

Droplet impact on surfaces with varying roughness and wettability is a common phenomenon in both natural and industrial environments. While previous studies have primarily examined asymmetric droplet rebound driven by impact velocity or Weber number, the influence of surface structure and associated impact mode transitions has received less attention. In this study, molecular dynamics simulations and detailed analyses are employed to investigate the mechanisms governing droplet rebound on nanopillar arrays with gradient distributions. Results reveal that nanopillar height significantly influences rebound direction, with two distinct directional transitions occurring as the height increases. Additionally, the effects of surface structure and Weber number on impact patterns, rebound velocity, and contact time are systematically evaluated, with contact angle calculations shedding light on the underlying force mechanisms. A phase diagram is developed to illustrate the relationship between rebound direction, Weber number, and nanopillar height. The study further extends the analysis to substrates with bidirectional gradient distributions, demonstrating consistency with single-directional gradient results and validating the broader applicability of the findings. This research provides critical insights into droplet dynamics on roughness gradient surfaces, emphasizing the role of nanopillar height and impact mode in controlling droplet behavior and highlighting potential applications in the design of structured array surfaces.

Effect of Pore Structure on Tertiary Low-Salinity Waterflooding in Carbonates: An In-Situ Experimental Investigation

Summary Low-salinity waterflooding (LSW) is an environmentally friendly and economically feasible technology that enhances oil recovery by controlling ionic composition or brine salinity. The recovery efficiency of this technique is strongly affected by the rock pore structure that governs the flow behavior of the injected brine. However, existing experimental studies elaborating on the relationship between pore structure and LSW performance in carbonates remain scarce. To address this gap, three carbonate plugs with different pore structures were displaced sequentially with synthetic high- and low-salinity brine under the capillary-dominated flow regime. High-resolution micro-computed tomography (CT) was used to obtain 3D images of different displacement stages, visualizing the fluid distribution. After image processing and contact angle calculation, it was found that the primary mechanism for enhanced recovery was wettability alteration, transitioning from oil-wet to weakly oil-wet. Significant differences were observed among the three samples. Sample 1 showed the highest additional recovery (22.2%), followed by Sample 2 (11.2%), and the lowest was Sample 3 (4.5%). Despite Sample 1 and Sample 3 having similar and narrow pore size distributions, they exhibited different fluid behaviors during LSW: In Sample 1, oil was mainly displaced from medium-sized pores, whereas in Sample 3, small pores were the main target for brine. The large coordination number likely enhanced the relative permeability of the high-salinity brine. The low-salinity brine followed the pathway formed by the high-salinity brine, affecting the LSW performance. This work provides novel insights into how pore structure affects oil recovery by comparing the response of multiple carbonate samples to LSW.

Study on evaluating and optimizing surface property mechanisms of polyalloy for enhanced OER catalyses via electrodeposited technique coupled with molecular dynamics simulations

Polyalloy catalysts composed of non-precious metals exhibit considerable potentials for facilitating overall water splitting processes in alkaline environments. However, achieving evaluations and optimizations of surface property mechanisms of polyalloy for enhanced OER catalyses is the key scientific issue that urgently need to be solved. Electrodeposited technique coupled with molecular dynamics simulations (MDS) are the key to breaking through aforementioned bottlenecks. Moreover, accurately predicting selections of non-precious metal elements in these catalysts through molecular dynamics simulations poses a challenging task. Here, three distinct non-precious metal catalysts (i.e. Ni, NiCo, and NiCoFe) were successfully synthesized through a facile one-step electrodeposition approach under a three-electrode system, which were deposited onto carbon sheets. For the sake of evaluating catalytic properties, MDS were utilized to calculate contact angles on ideal surfaces, which were verified by experimental measurements. Furthermore, ternary alloy catalysts (i.e. NiCoFe) exhibited an overpotential of 254 mV at a current density of 10 mA cm2 and exhibited remarkable stability over a prolonged 150-hour testing period. Finally, main findings can further underscore potentials of utilizing electrodeposition to fabricate efficient non-precious metal catalytic electrodes for overall water splitting, as well as the feasibility of indirectly predicting electrocatalytic performances of such cost-effective catalysts via MDS.

Insights into the flotation performance of ethylenediamine surface modified hemimorphite: Experimental and DFT study

Upon utilizing micro-flotation, contact angle, AFM, ToF-SIMS, XPS, ICP-OES, and DFT calculations, the influence of ethylenediamine (EDA) on the flotation mechanism of hemimorphite was investigated. The addition of EDA to the flotation system led to a 25.15 % increase in flotation recovery efficiency. Contact angle and AFM analysis indicated that EDA enhanced both the hydrophobicity and surface roughness of hemimorphite. Subsequently, ToF-SIMS deep profiling analysis indicated that EDA modification facilitated the incorporation of sulfur ions into the internal structure of hemimorphite, forming a uniform zinc sulfide film. Furthermore, XPS and ICP-OES analysis demonstrates an increase in sulfides on the surface of the hemimorphite after EDA modification. Additionally, the results of DFT calculations showed that the adsorption energy of an EDA molecule on the hemimorphite (1 1 0) surface was −956.492 kJ/mol.

Calculation of apparent contact angle for sessile droplets on structured hydrophobic surfaces based on dynamic of contact line during droplet formation

The sessile-droplet method is widely used to characterize surface wettability, however, the measured apparent contact angle (APCA) is usually a non-unique value between the advancing and receding contact angles, which seems hardly to be predicted by the classical Cassie-Baxter model. Thus, a reliable calculation model for APCAs of sessile droplets on structured hydrophobic surfaces is needed to guide the structural design of functional hydrophobic surfaces. Focusing on the force and motion analysis of the contact line during the formation process of sessile droplets, a theoretical model was developed to calculate the APCA of the droplet on hydrophobic surfaces featured with square micropillar arrays. The present model considers the synergistic effect of the droplet shape and the contact-line pinning on the APCA. Compared with the Cassie-Baxter model, the APCAs calculated by the proposed model agree better with the experimental data. This study shows that APCA is generally more susceptible to advancing contact angle, which is not significantly different on structured hydrophobic surfaces with different dimensions, resulting in the inability of APCA to accurately characterize surface wettability. As a complement, receding-contact-angle and adhesion-force measurements, which can reflect the effects of structural dimensions, are recommended to be adopted to characterize surface wettability.

Contact angle calculations for argon and water sessile droplets on planar lyophilic and lyophobic surfaces within molecular dynamics modeling

There exist many ways to calculate the contact angle of a sessile droplet on a planar surface on the basis of molecular modeling data, and the result may depend on the chosen approach. This paper presents molecular dynamics simulations of argon and water sessile droplets on simple model and more complex atomistic substrates. Several approaches for calculating contact angles are described. These approaches are based on an analysis of instantaneous droplet’s configurations and averaged density profiles. The latter are analyzed using density cutoffs and the Sobel filters. Parameters of the interaction between the planar surface and the fluid are being tuned in order to consider model lyophilic and lyophobic substrates. Dependences of the contact angle on the strength of interaction between the fluid and the substrate and on the droplet size are obtained. The apparent line tensions for the observed sessile droplets are evaluated.

Study of the contact angle and roughness effects on mercury intrusion porosimetry (MIP) analysis in natural/real carbonate rocks using massive pure minerals and synthetic carbonate rocks

Studying pore networks in rocks is critical for understanding reservoir properties, with mercury intrusion porosimetry (MIP) being a key laboratory method. MIP involves capillary intrusion of mercury, with intrusion pressure (P) related to capillary diameter (d) by the Washburn equation, incorporating mercury properties like contact angle (θ) and surface tension (γ). While a constant contact angle of 140° is typically assumed for MIP, it can vary based on rock mineralogy and surface roughness. This study aims to analyze how contact angle variations and surface roughness affect MIP analysis of carbonate rocks. Initially, contact angle data was obtained for calcite, dolomite, and quartz with varying roughness levels. Synthetic rocks were then constructed using these minerals. MIP was performed using the typical 140° contact angle and a calculated contact angle from the Cassie model, which considers surface composition fraction. Natural rock MIP analysis followed, with contact angles varying due to mineral composition and roughness. The study found higher contact angles than the standard 140°, affecting pore size distributions up to 30%. Natural rock pore network curves were adjusted based on synthetic rock data analysis. These findings emphasize the need for accurate contact angle selection in MIP for precise pore distribution analysis and contribute to the further study of carbonate rocks.

Wettability and reactivity of liquid aluminium and highly deformed steel

The high-temperature liquid Al - solid S355J2N steel interaction was studied using a modified wettability test. A sessile drop method with a capillary purification procedure was employed for the first time, involving non-contact aluminium isothermal heating followed by the dropping of a pure liquid Al drop onto the severely deformed steel substrate and isothermal contact heating of Al with steel. The calculated contact angles and wetting kinetics curves demonstrated a good spreading and wetting of the investigated system. Scanning electron microscopy investigations played an important role in interpretation of the microstructural characteristics of the specimen, especially those located at the drop/substrate interface. The electron backscattered diffraction measurements allowed to characterize the microstructure of the interface zone to obtain more detailed information about the grain size, type of the intermetallic phases: θ-Al13Fe4, Fe2Al5, FCC Al and ferrite and their distribution in the neighborhood of the interface zone. These intermetallics were also confirmed via transmission electron microscopy studies coupled with energy-dispersive X-ray spectroscopy analysis of the drop/substrate interface. Research findings provide valuable insights into the liquid Al and steel interaction during the explosive welding process, where the local melting of metal takes place at the interface of colliding plates, strongly deformed due to the collision.

Galvanic interaction between galena and pyrite with dithiothreitol and its effects on flotation performance

With the advancement of green mine construction and the increasing difficulty of lead–sulphur resources, the traditional lime high-alkalinity lead–sulphur separation technology has exposed many shortcomings. In this study, based on the galvanic interaction of galena and pyrite, an environmental-friendly depressant dithiothreitol (DTT) was used to separate pyrite and galena under low alkalinity. In addition, the mechanism of DTT was revealed by electrochemical, ion dissolution, contact angle, zeta potential and DFT calculation. The results indicated that the galvanic interaction between galena and pyrite promoted the oxidation of galena and the dissolution of Pb2+ from the surface of galena, and Pb2+ would be adsorbed on the pyrite surface and increase the floatability of pyrite. DTT could selectively depress pyrite at low alkalinity. The interaction mechanism of DTT was that DTT could weaken the galvanic interaction of galena and pyrite and complex lead ions. In addition, DTT was adsorbed on the pyrite surface through the Fe-S bond, and the pre-adsorbed DTT hindered the adsorption of DDTC on the pyrite surface, thus the pyrite flotation was depressed.

Modeling Water Interactions with Graphene and Graphite via Force Fields Consistent with Experimental Contact Angles.

Accurate simulation models for water interactions with graphene and graphite are important for nanofluidic applications, but existing force fields produce widely varying contact angles. Our extensive review of the experimental literature reveals extreme variation among reported values of graphene-water contact angles and a clustering of graphite-water contact angles into groups of freshly exfoliated (60° ± 13°) and not-freshly exfoliated graphite surfaces. The carbon-oxygen dispersion energy for a classical force field is optimized with respect to this 60° graphite-water contact angle in the infinite-force-cutoff limit, which in turn yields a contact angle for unsupported graphene of 80°, in agreement with the mean of the experimental results. Interaction force fields for finite cutoffs are also derived. A method for calculating contact angles from pressure tensors of planar equilibrium simulations that is ideally suited to graphite and graphene surfaces is introduced. Our methodology is widely applicable to any liquid-surface combination.

Calculation of contact angle via Young-Dupré equation with molecular dynamic simulation: Kaolinite as an example

To explore the surface wettability, the contact angle was usually experimentally measured by sessile drop method, which is very sensible to the experimental conditions. Molecular Dynamics (MD) simulation method has been applied to study nanodroplets, but the contact angles were usually obtained via curve fittings of the droplets, which is subjective and the errors inevitable. In this work, Young-Dupré equation was applied to calculate the contact angle with the surface tension coefficient of water and the adhesion work of water/surface, which were achieved via MD simulations results. The wettability of layered kaolinite was studied as an example. The computed contact angle of water on the Al-O octahedral surface of kaolinite was 0°, and those on the Si-O tetrahedral surface were roughly 92° ∼ 104°, which agreed well with the results of curve fitting method, about 0° for the Al-O octahedral surface and 106° ± 9° on the Si-O tetrahedral surface. The dipole moment distribution, dipole angle distribution of water molecules, as well as the evolution of hydrogen bond number during the whole dripping process of water droplet on kaolinite surfaces were analyzed to reveal the mechanism of hydrophobic/hydrophilic of different surfaces of kaolinite.

Practical method for studying the dispersion behavior of TiC nanoparticles in molten Mg

The dispersion behavior of TiC nanoparticles in molten Mg was investigated by using molecular dynamics simulations based on Li's theoretical model of nanoparticle capture. First, the contact angles between molten Mg and the TiC substrate were calculated over a temperature range of 973–1173 K, and the error was within 10% of the experimental values. The calculated contact angles and Li's theory, confirmed that the dispersion behavior of TiC nanoparticles in molten Mg can be of three types. Subsequently, the effects of the nanoparticle radius and temperature on the dispersion behavior of TiC nanoparticles in molten Mg were studied. The results showed that TiC nanoparticles having a radius of less than 55.8 nm can be uniformly dispersed in molten Mg at 973 K. For TiC nanoparticles having a mean particle radius of 60 nm, the temperature must exceed 1045 K to achieve self-dispersion of the nanoparticles in the Mg melt. This study presents a practical computational technique for the preparation of Mg matrix nanocomposites.

Nitrogen Plasma Treatment of Composite Materials Based on Polylactic Acid and Hydroxyapatite.

The effect of surface modification by an arc discharge plasma in a nitrogen flow with treatment durations of 5 and 10 min on the physicochemical properties and biocompatibility of the surface of composites based on polylactic acid and hydroxyapatite (PLA/HA) with different mass ratios (80/20, 70/30, 60/40) has been investigated. The aim of this work was to show the correlation between the changes of the physicochemical characteristics (chemical compound, morphology, wettability) of the surface layer of the PLA/HA composites and the cell viability (macrophages) in the presence of the plasma-modified materials. The dependence of alterations of the functional properties (wettability, biocompatibility) on the change in the chemical composition under the plasma exposure has been established. The chemical composition was studied using X-ray photoelectron spectroscopy (XPS), the surface morphology was researched with scanning electron microscopy (SEM), and the wettability of the composite's surface was analyzed by measuring the contact angle and surface energy calculation. In addition, the viability of macrophages was investigated when the macrophages from three donors interacted with a modified PLA/HA surface. It was found that the formation of the new functional groups, -C-N and N-C=O/C=O, improves the wettability of the surface of the composites and promotes the viability of macrophages in the presence of the composite materials. The fundamental principles for obtaining promising materials with the required properties for eliminating bone defects have been created.

Contact angle measurement for polymeric membranes: software selection for ease of use and precision

Contact angle measurement by sessile drop (SD) and captive bubble (CB) method is calculated by the four software, i.e. ‘Angle Tool’ plugin, Drop Snake (DS) plugin, and LB-ADSA plugin of the ImageJ®; and the Ossila® with their advantages and disadvantages. In this study, the ease of use and precision were tested by standard deviation calculation for different hydrophilic membranes. Angle Tool plugin, and DS plugin of ImageJ®; and the Ossila software gave high standard deviations due to rough cut membranes edges giving background shadows misleading the software algorithm. LB-ADSA plugin of the ImageJ® had both advantages of manual drop edge selection and algorithmic calculation of contact angle giving the lowest standard deviation. Therefore, we found that the LB-ADSA plugin of ImageJ® is precise for hydrophilic membranes by both SD and CB methods.

Method for Measuring the Three-Dimensional Morphology of Near-Wall Bubbles and Droplets Based on LED Digital Holography.

Digital holography, recognized for its noncontact nature and high precision in three-dimensional imaging, is effectively employed to measure the morphology of bubbles and droplets. However, in terms of near-wall bubbles and droplets, such as confined bubbles in microfluidic chips, the measurement of the interface morphology of bubbles near the glass surface has not yet been resolved due to the coherent noise resulting from glass surface reflections in microfluidic chips. Accordingly, an off-axis digital holography system was devised by using Linnik interferometry. Measuring the confined bubble interface near the wall within a microfluidic chip and droplet evaporation on solid surfaces was studied. Partially coherent LED sources and reference light modulation techniques were employed in the optical setup to mitigate the coherent noise. Dual exposure and weighted least-squares unwrapping algorithms were introduced to correct phase distortions, enhancing image quality. Imaging two confined CO2 bubbles was done near the wall in silicon oil within a porous microfluidic chip, and contact angles of 4.7 and 4.5° were measured. Additionally, the measurement of the three-dimensional morphology of vertically evaporating deionized water droplets on a glass surface was done, due to which calculation of contact angles at various orientations was possible. This work offers a feasible new method for measuring the 3D interface morphology of bubbles and droplets, particularly in microfluidic visualization, addressing current measurement gaps.

Impact of coating and curing temperature on the formation of CFRP/sealant gradient interphase

Flexible sealant joints are extensively utilized for sealing aircraft wing fuel tanks due to the excellent stress transfer release of gradient interphase. This study investigates the impact of coating and curing temperature on the formation of CFRP/sealant gradient interphase. The interphase quality was identified using SEM equipped with EDS, and a detailed analysis of element concentration transition was performed to understand the interplay between different mechanisms. Contact angle calculation and FTIR-XPS combined spectral analysis were conducted to determine the interfacial physicochemical state. The results showed that coating enhances compatibility and broadens interphase, whereas opposite results were observed at higher temperatures. The improvement of surface energy and wettability, chemical groups, and molecular bonding sites provided by coating promotes interfacial reactivity and molecular mobility. Elevated cure temperature accelerates the formation of cross-linked networks that restricts sealant chain mobility, indicating that vulcanization dominates over diffusion under high cure temperature.

Segmentation of two-phase flow X-ray tomography images to determine contact angle using deep autoencoders

This study improves the characterization of in situ contact angles in porous media by employing deep learning techniques (SegNet, UNet, ResNet, and UResNet) for multiphase segmentation of micro-CT images. The algorithms were tested on high-resolution X-ray images of a steady-state flow experiment where two fluid phases were simultaneously injected at different fractional flows. The models were trained to segment the images into solid, aqueous phase, and non-aqueous phase liquid (NAPL). The UResNet demonstrated the best performance with an f1-score of 0.966 for the test dataset. More importantly, the UResNet offered higher reliability than the watershed algorithm for various fractional flows based on visual inspection and phase distribution analysis. The porosity calculation error of the watershed method (7.8 %) was reduced to 5.1 % by UResNet. Furthermore, UResNet accurately depicted the consistently mixed-wet condition of the rock sample throughout the experiment, in contrast to the watershed segmentation that yielded inconsistencies in contact angle calculations at an aqueous phase fractional flow of 0.01.

Preparation of PDA@AP composite particles by two‐step method and its application in glycidyl azide polymer‐energetic thermoplastic elastomer propellants

AbstractPolydopamine (PDA) has been widely used in the field of energetic materials; however, there are few reports on the ammonium perchlorate (AP) coating of PDA. In this article, to improve the mechanical properties of the GAP‐ETPE‐based propellant, a two‐step method was used to coat the AP with PDA and used in glycidyl azide polymer (GAP) based propellant. SEM, EDS, XRD, and XPS were used to analyze the morphology and composition of PDA@AP, while contact angle testing and calculation were performed to measure the wettability and surface energy of both PDA@AP and GAP‐ETPE. In addition, the tensile strength and elongation of the propellant were measured. The results showed that the PDA@AP composite particles were successfully prepared. The crystal form remained unchanged during the preparation process. The wettability of PDA on AP was improved through the coating of PDA, leading to an increase in the surface energy of AP and enhancing the adhesion between AP and GAP. Mechanical performance testing shows that using PDA@AP in propellants increased the tensile strength of the propellant from 1.2 to 1.8 MPa, while the elongation at break decreased from 208% to 155%. The “dewetting ratio” has also decreased from 2.88 to below 2.5.

The direct observation and distribution regularity of contact angle for spherical particle attached to air bubble in static three-phase system

Contact angle is a typical parameter to indicate the hydrophobicity of solid surface, and it is usually used to evaluate the wettability and floatability of mineral particles. Directly measurement on contact angle of particles is critical for laboratory research and industrial practice in flotation. By combining the image processing analysis and force balance calculation, a composite method to directly measure contact angle of particle was proposed. The good agreement between observed contact angle and calculated contact angle during lots of experiments proved the accuracy and convenience of this measurement method. The fundamental effects of particle size, hydrophobized time, and bubble size on contact angle distribution of particle were investigated using hydrophobized glass beads with different particle size. For glass beads with same surface hydrophobicity, the contact angle showed a nearly constant trend with varying particle size and bubble size. The essence of distribution regularity of contact angle was uncovered through force calculation analysis. Besides, the central angle is always larger than half of contact angle if a smooth spherical particle successfully attached to an air bubble and achieved equilibrium state.