Washburn Method Research Articles

Improving water management in gas diffusion layers through the optimization of carbon composite microporous layers

Using the Washburn method, the wettability of microporous layer (MPL)-coated carbon-felt gas diffusion layers (GDLs) with liquids with different polarities were studied using process tensiometry. The Washburn approach allows us to study fluid uptake into the electrode pores through capillarity and the resulting liquid-solid internal contact angles. Interpretation using the Owens-Wendt analysis reveals the effects of varying proportions of hydrophobic poly(tetrafluoroethylene) (PTFE) and multi-walled carbon nanotubes (MWCNTs) in the MPL yielding solid-vapor surface energies. An optimal MPL contained a 10 wt% MWCNT/KJB carbon substrate and 10 wt% PTFE loading. This information was corroborated by evaluating these materials in anion exchange membrane fuel cells with simultaneous gas and aqueous electrolyte feed.

Effect of Anionic Surfactants on the Oil-Water-Rock Interactions by an Improved Washburn Method.

The complex and variable structure of subsurface oil reservoirs as well as the small pore throat size of reservoirs make it extremely important to investigate the effect of oil-water-rock interactions for enhancing oil recovery. In this paper, the powder wettability of oil sand with different polar solvents was investigated using the improved Washburn capillary rise method, and the surface free energy of oil sand was calculated in combination with the OWRK method. In addition, the wettability of anionic surfactants HABS and PS solutions on the surface of oil sand was determined, and it showed that their wetting rates showed different trends after CMC (critical micelle concentration). The C×cosθ value of HABS decreased significantly with increasing concentration, whereas PS showed little changes. This may be related to the aggregate structure formed by HABS on the oil sand surface. Meanwhile, the interfacial free energy between crude oil and oil sand was obtained by crude oil-to-oil sand wetting experiments, and found that the wetting rate of crude oil to oil sand was much lower than that of solvents and surfactants. In combination with the above results and the oil-water interfacial tension (IFT), the oil-water-rock three-phase contact angle and the work of adhesion between the crude oil and the solid were obtained by Young's equation. From the three-phase contact angle results, it can be found that the contact angle values of both HABS and PS are obviously higher than that of the simulated water, and both HABS and PS have the ability to significantly reduce the work of adhesion, which shows a strong ability to strip the oil film on the surface of the solid. The research results of this paper are helpful to understand the oil displacement mechanism of chemical flooding in reservoir pores, which is of great significance for improving oil recovery.

PEAKFORCE QUANTITATIVE NANOMECHANICAL MAPPING FOR SURFACE ENERGY CHARACTERIZATION ON THE NANOSCALE: A MINI-REVIEW

Surface energy characterization is important to design the fabrication process of reliable electronic devices. Surface energy is influenced by various factors such as surface functionality and morphology. Owing to the high surface-to-volume ratio, surface energy at the nanoscale can be different from that of the bulk. However, the conventional methods for characterization of surface energy such as a sessile drop or Washburn methods cannot be used for nanoscale samples, owing to the limited volume for characterization. Recently, surface energy characterization on the nanoscale using atomic force microscopy (AFM) with Peak Force-Quantitative Nanomechanical Mapping (PF-QNM) imaging mode has been proposed. The nanoscale AFM tips measure the adhesion forces at the nanoscale, which are converted into surface energy through pre-calibrated curves. Successful surface energy characterization of nanoscale metal samples using AFM with the PF-QNM method has been reported previously. This mini-review discusses the recent progress on surface energy characterization at the nanoscale using AFM with the PF-QNM method. The fundamentals of the PF-QNM mode are introduced, and the results of surface energy characterization are summarized. Consequently, the future research direction for surface energy characterization at the nanoscale is discussed.

The Role of Surface Free Energy in Binder Distribution and Adhesion Strength of Aqueously Processed LiNi0.5Mn1.5O4 Cathodes

This study identifies the critical aspects of binder distribution and mechanical integrity in aqueously processed LNMO cathodes, employing a comprehensive approach involving surface characterization techniques, adhesion strength testing, and electrochemical characterization. The investigation includes the use of the Washburn and Sessile Drop methods for surface free energy analysis, revealing key insights into the interfacial free energy of adhesion between cathode constituents. The results explain the formation of carbon-binder-domains and their impact on adhesion strength, with a particular focus on the conductive additives’ (CA) surface area. The study demonstrates the effectiveness of reducing CA surface area and employing alternative conductive additives, such as vapor-grown carbon fibers (VGCF), in improving adhesion strength and mitigating capacity fade attributed to delamination during cycling. Furthermore, the research emphasizes the role of heat treatment beyond the melting point of the polyvinylidene fluoride (PVDF) latex binder, showcasing its influence on wetting and enhancing mechanical integrity. The presented methodology provides a valuable tool for predicting and optimizing binder distribution, offering insights into improving the overall performance and reliability of aqueously processed cathodes for advanced lithium-ion batteries.

Further Exploration of Heat of Immersion as a Method to Quantify Wettability for Particulates: Effect of Temperature.

A previous paper [Weston et al. Ind. Eng. Chem. Res. 2015, 54, 4274-4284] by our group concluded that to distinguish between the wettability of different particles, heat of immersion is the best method, as opposed to the Washburn or sessile drop method. In this paper, heats of immersion of three different particles with three different wettabilities are measured at different temperatures to examine one critical assumption concerning the temperature dependence of the heat of immersion. In addition, surfactants are added to the water, and the effect of surfactant concentration on the heat of immersion is measured. One particularly noteworthy aspect of the current study is that some measurements were made at temperatures greater than 100 °C and hence pressures higher than atmospheric pressure with no more difficulty than measurements made at atmospheric pressure. The previous paper showed that, for certain particles, the relationship used by us and others between the heat of immersion and contact angle gave impossible values for certain surfaces. In this paper, the derivation of that expression is reexamined, and certain assumptions are highlighted. Because of issues with the assumptions, we agree with the conclusion from our previous paper that using the heat of immersion as a qualitative measure of wetting is appropriate. However, without measurement of the values of the liquid-solid interfacial energy with temperature as well as the gas-solid interfacial energy with temperature, conversion to the contact angle directly is not appropriate. However, for the same surface, using this approach to quantify the contact angle as a function of temperature is likely appropriate if the contact angle is measured using some other method at one temperature, at least over the limited temperature range (up to 150 °C) explored in this study.

Sorption Capabilities of Polypropylene/Modified Polypropylene Fibers

The aim of this paper is to present the influence of the modification of polypropylene (PP) fibers on the sorption capabilities of the fibers. The physical modification of the PP fibers was made with inorganic nanoadditives in the mass, with a view to improving the properties of silicate composites used in the construction industry. The compositions of the modified PP fibers using two different nanoadditives were based on previous work, as well as the work presented in this paper. The prepared modified PP fibers were compared with pure PP fibers, and their mechanical and thermomechanical properties were evaluated. Another task of this work was to evaluate and compare the sorption capabilities of these fibers without the preparation of concrete blocks. Therefore, the Washburn method was used. However, the obtained results led us to the conclusion that the given method points to the excellent transport properties of PP fibers if such properties are used to evaluate the sorption of the fibers. However, the sorption of the prepared modified fibers could be associated with the nanoadditives used, which have a higher water sorption capacity compared to pure PP fibers, and this could also ensure the higher adhesion of the modified PP fibers with inorganic additives to the cement matrix compared to the adhesion of the hydrophobic PP fibers.

Study of the surface energy characteristics of glass and carbon fiber by the Washburn method

The Washburne adsorption method (capillary rise method), as an alternative to the standard single fiber method, is proposed to investigate the surface energy characteristics of glass and carbon fibers using a K- 100 processor tensiometer. The paper considers sample preparation of fibrous materials measured by the Washburn method: filling a Teflon tube with glass and carbon fibers, packing density of the resulting capillary, and determination of the capillarity constant. The results of measurements of the wettability of fibers in test liquids (water, hexane) and in the solution epoxy binder UP-2227N are presented. The influence of appretting on the surface energy characteristics of glass fiber and carbon fiber was studied, a comparative analysis of the obtained values (wetting angle, SEP, adhesion) was carried out before and after the removal of lubricants.

Biosurfactant from a thermo-halophilic strain of Bacillus alveayuensis isolated from a Brazilian oil reservoir: Production, chemical characterization, antimicrobial activity, and efficiency in wettability reversal and oil removal from oil-soaked sand.

Biosurfactants (BS) are amphiphilic molecules from microbial secondary metabolism capable of reducing surface and interfacial tension between non-miscible phases, thus having a wide range of industrial and environmental applications. In this context, the present work aimed to study the biosurfactant produced by the bacterial strain Ar70C7-2, isolated from rocky samples of a deep offshore Brazilian oil reservoir, to evaluate its application in the oil industry. Its optimized production conditions, chemical structure, stability in extreme conditions, surface-active properties in porous media, and antibacterial action were evaluated. Strain Ar70C7-2 showed 100% similarity to Bacillus alveayuensis and was able to produce 0.27 g/L of crude BS in the Mineral Medium with glycerin and NH4NO3 at a ratio of 2, under fixed conditions of 70 g/L NaCl, incubation at 55 °C, and no stirring. The semi-purified BS presented emulsification index (E24) above 55%, surface tension of 31.8 mN/m, interfacial tension (against n-hexadecane) of 17.6 mN/m and CMC of 65 mg/L. The BS belongs to the class of lipopeptides, with a protein composition of 7% and fatty acid chain ranging from C14 to C18, with homologue C16 as the most abundant. Mass spectra of BS indicate the presence of surfactin, iturin, and fengycin families. Semi-purified BS was able to remove approximately 30% of the motor oil (10W40) present in oil-soaked sand, as tested by the contaminated sand washing method; it also promoted the alteration of carbonate wettability, as demonstrated in the flotation test and by the Washburn method. BS inhibited growth of the sulfate-reducing bacteria (SRB) Desulfovibrio marinus BRS-1 at concentrations of 2250 μg/mL and showed bactericidal action at concentrations of 2500 μg/mL. These results demonstrate that the biosurfactant produced by strain Ar70C7-2 has the potential for application in MEOR, bioremediation, and controlling SRB growth, encouraging further studies to validate its prospect in laboratory and field conditions.

Insight on the mechanism of hexagonal pyrrhotite depression by starch during flotation

Polysaccharides such as gelatinized starch have been largely employed to depress specific minerals during froth flotation. In this study, two samples of caustic gelatinized starch (paste starches) with different molecular weights (MW) were used as depressants for hexagonal pyrrhotite. There is an increasing interest in finding more environmentally friendly strategies to depress hexagonal pyrrhotite since this mineral is one major gangue minerals in nickeferrous ore deposits, for instance. The mechanism of adsorption of paste starches on hexagonal pyrrhotite was evaluated by different techniques. Equilibrium adsorption tests suggested that the adsorption is dependent on the depressant molecular weight if it is used in high concentrations. The sequence of conditioning also showed to be relevant. Pre-adsorbed collector highly influenced the adsorption of higher MW paste starch. Langmuir and Brunauer–Emmett–Teller (BET) model fittings of adsorption data in combination with Quartz Crystal Microbalance with Dissipation (QCM-D) results demonstrated a looser packing density of the higher MW paste starch. This conformation provides more room for water molecules within this depressant’s chains. Since trapped water molecules may generate a repulsive hydration force to air bubbles near the mineral surface, pyrrhotite conditioned with the high MW paste starch showed a lower flotation recovery. Higher hydration levels of the higher MW paste starch were also proven by Atomic Force Microscopy (AFM) tests, and indirectly quantified in the contact angle measurements (Washburn method). Although the higher MW paste starch adsorbs less, this depressant still provides a higher surface wettability. This study has reinforced the importance in considering the molecular size of a polysaccharide for sulfide mineral depression.

Study of Surface Wettability of Mineral Rock Particles by an Improved Washburn Method.

The surface wettability of rocks in underground reservoirs affects the distribution of fluids in the reservoir, so the wettability of reservoir minerals is a key factor for crude oil recovery from reservoirs. In this paper, the wettability of quartz sand with different particle sizes in different polar solvents was determined by Washburn's capillary rise method, and the C·cos θ values were calculated first. Next, the experimentally obtained macroscopic contact angle of water on the quartz surface of 15.0° was substituted into C·cos θ to obtain a linear equation between the particle size of quartz sand and the capillary constant C. The particle sizes of oil sand and mineral powder were then substituted into the equation to obtain their capillary constants C. Then, based on the Owens-Wendt-Rabel-Kaelbe (OWRK) equation and the obtained contact angles of solvent on quartz sand, oil sand, and mineral powder, the surface free energy of quartz sand with different particle sizes is calculated as 76.09, 76.65, and 76.42 mN/m, respectively, which are close to the literature results. In addition, the surface free energy of oil sand with different particle sizes was 23.22, 23.45, and 23.63 mN/m, and the results indicated that the polarity of oil sand was low. Meanwhile, the surface free energies of kaolinite, illite, feldspar, and montmorillonite were 61.59, 32.85, 35.87, and 25.91 mN/m, respectively. By the improved Washburn method in this paper, the wettability of different solvents on the surface of reservoir rocks was investigated, and the surface free energy of specific solid particles was calculated, which is important for studying the extraction of crude oil from subsurface reservoir rocks.

Multidimensional evaluation of highly durable scalable and seamlessly integrated fiber-based electrodes for wearable applications

The emergence of “green” electronics is a response to the pressing global situation where conventional electronics contribute to resource depletion and a global build-up of waste. For wearable applications, green electronic textile (e-textile) materials present an opportunity to unobtrusively incorporate sensing, energy harvesting, and other functionality into the clothes we wear. However, the robustness and functional longevity of the majority of e-textiles made of green electronic materials are not sufficient. Here, we demonstrate knittable, washable, durable, electroactive fibers produced through a scalable roll-to-roll coating process using a biocompatible polymer:polyelectrolyte complex poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) ink. In order to analyze the fiber's wetting behavior prior to coating, surface energy of synthetic fiber materials was evaluated. For the first time, the Owens, Wendt, Rabel and Kaelble (OWRK) approach along with the Washburn method were used to determine apparent surface energies of fiber materials and calculate the work of adhesion and interfacial tension between the conductive ink and fiber substates. The coated fibers developed in this study were successfully knitted into 3D textile electrodes using an industrial-scale knitting machine and machine washed for 60 times without any deterioration in performance to collect electrocardiogram signals. The wash durability of the coated fibers in combination with the scalable coating process make these fibers suitable to be integrated into smart textiles and wearable products for various application.

A rate-of-rise facility for measuring properties of wick structures

This work details a mass rate-of-rise (mROR) apparatus and analysis method for the accurate and precise determination of capillary wick parameters: permeability, K, effective pore radius, r eff, and porosity, ϵ. Three factors were examined: (a) the accuracy of the theoretical models and their curve-fitting approaches associated with the mROR technique, (b) the influence of the experimental procedure on repeatability, and (c) how the uncertainty of the experimental input parameters propagates through the data analysis procedure and compounds the overall uncertainty of the wick parameters (K and r eff). Four models and fittings methods were investigated: the Lucas–Washburn method, the gravity-based dm/dt method, the gravity-based t–m method, and the gravity-based m–t method. It is demonstrated that the m–t method developed here shows the lowest error and, equally importantly, that it is free of user decisions in the context of ‘data scrubbing’ because the entire mROR data set is used in its raw form. To test accuracy and repeatability, a precision-controlled mROR apparatus is proposed. Experiments were performed for commercially available wicks. A robust Monte Carlo error analysis method was developed and applied to quantify the overall uncertainty in the wick parameters as a function of the input uncertainties of all measured quantities.

Impact of molecular chain structure of suspension phase on giant electrorheological performance

We demonstrate the impact of diester structure, in particular the alkyl chain length and branching structure, on the giant electrorheological (GER) effect and suspension stability. The existence of oil–particles interaction is of critical importance to induce the GER effect. To quantify GER performance and colloidal stability, we examine the yield stress, current density, field-off viscosity and sedimentation ratio with respect to the variation of chain length and branching structure. The oil–particles interaction is quantitatively analyzed by investigating the cluster size of particles in different diesters by a multiple light scattering analyzer, along with the wettability of different chain lengths of diesters and solid particles by the Washburn method. Our results indicate that long chain lengths favor the formation of particle agglomerates, thereby enhancing the GER effect (such as high yield stress). The attachment of branches on diester causes the formation of electronic correlation between branches and main chain, depending on the position of branches located, and hence results in superior GER performance and favorable suspension stability. An optimal GER fluid constituted by bis(2-ethylhexyl) sebacate is acquired with the achieved yield stress of 113 kPa at electric field strength of 4 kV mm−1 and the prominent integrated GER properties.

Impact of altered hydrophobicity and reduced agglomeration on dissolution of micronized poorly water-soluble drug powders after dry coating

The impact of dry coating with hydrophobic or hydrophilic nano-silica at 25–100% surface area coverage on dissolution of micronized poorly water-soluble drugs was investigated by examining their agglomeration and surface hydrophobicity. Ibuprofen (20 µm and 10 µm) and griseofulvin (10 µm) were selected having differing solubility, hydrophobicity, and surface morphology. Characterization involved particle agglomeration via two dry dispersion methods, drug dissolution using the USP IV method, cohesion reduction through shear testing, and powder wettability via the modified Washburn method. Dry coating dramatically reduced the cohesion hence agglomerate size of both the coated ibuprofen particles, but less for griseofulvin, attributed to its surface morphology. For hydrophobic silica, agglomerate size reduction outweighed the adverse impact of increased surface hydrophobicity for ibuprofen. For griseofulvin, the agglomerate reduction was much lower, not able to overcome the effect of increased drug particle hydrophobicity with hydrophobic silica coating. Hydrophilic silica coating reduced hydrophobicity for all three drug powders, leading to the synergistic improvement in the dissolution along with agglomerate size reduction. Overall, the combined effect of the drug particle surface hydrophobicity and agglomerate size, represented by specific surface area, could explain the dissolution behavior of these poorly water-soluble drugs.

Impact of Surface Properties of Core Material on the Stability of Hot Melt-Coated Multiparticulate Systems

Hot melt coating (HMC) of an active pharmaceutical ingredient (API) powder with lipid-based excipients is an innovative method for manufacturing patient-convenient dosage forms. However, drug release instability is still its main industrial challenge. The correlation between the unstable pharmaceutical product performance with the solid-state alteration of lipids is currently well-investigated. The remaining problem is the inconsistent release alteration of different APIs coated with the same lipid after storage, such as faster release in some cases and slower release in others. The interaction between API surface and lipid-based coating and its alteration during storage were investigated in this work. The surface properties of five different APIs and the coating composition of tripalmitin and polysorbate 65 were screened via Washburn and pendant drop methods, respectively. Metformin hydrochloride and hydrochlorothiazide particles were each coated with the coating composition. The water sorption alteration of coated particles and the crystal growth of tripalmitin in the coating after storage were measured via tensiometry and X-ray diffraction. The cleavage work necessary to overcome the adhesion of coating composition on the core surface was calculated for each API. The accelerated release of the polar core (metformin) after storage was correlated with a low cleavage work and a distinctive phase separation. In contrast, a decelerated release of the hydrophobic core (hydrochlorothiazide) was favored by the crystal growth of the lipid-based coating. The gained knowledge can be used to design the product stability during the formulation development.

Enhanced Washburn Method (EWM): A comparative study for the contact angle measurement of powders

Washburn Method (WM) as a typical contact angle measurement (θ) method can be used for assessment of powder wettability (especially representative particle size range for flotation separation). However, as an indirect method, WM has several limitations. This investigation is going to introduce an Enhanced Washburn Method (EWM), which fills the gap of those WM obstacles, and can be applied for the meaningful indirect θ measurement of powders. For such a purpose, the wettability of quartz powders (d80: 62 μm) was measured in the absence and in the presence of the cationic surfactant Flotigam®EDA at pH 10. EWM by using pre-conditioning of hydrophobized particles via unblock capillaries measured the θ of powders in different conditions. Statistical evaluations indicated that EWM could quite accurately measure θ of the hydrophobized powders, where there is a significant coefficient of determination (R2 above 0.96) between EWM outcomes and other examined direct θ measurement methods (the captive bubble and sessile drop methods).

Rheological behavior of porous pharmaceutical materials: Linking torque profiles during wet massing to water diffusion coefficients and penetration time

Wet massing is commonly performed during the wet granulation process after the addition of a liquid binder. Torque values were measured using a Mixer Torque Rheometer (MTR) by the method of multiple additions of water and variable mixing time. The main objective of this work is to link water diffusion coefficients and penetration time in pharmaceutical powders to torque profiles generated in an MTR. The diffusion coefficients were calculated by fitting the experimental data to an exponential decay function and by minimizing the Root Mean Square Error between the fitted curve and the solution of Fick’s 2nd law. Water penetration times were measured and calculated using experimental drop penetration and Washburn methods, respectively. The main research hypothesis is that the temporal change in torque profiles after each water addition step is related to the mass diffusion coefficients and water penetration time in the powder of varying degrees of water content. The results show that for the microcrystalline cellulose (MCC) powders at varying granulating fluid levels, capillary diffusion seems to be more adequate to explain the rheological behavior observed compared with the Fickian diffusion model.

Evaluation of the surface energy of dispersed aluminium oxide using owens-wendt theory

Knowing the value of the surface energy of powder materials allows to predict the interaction of the solid phase with liquids, the formation of stable dispersions, durable and resistant to aggressive factors of composites. The application of the Owens-Wendt model for determining the change in the surface energy of aluminium oxide modified by various water repellents is considered. Also, to determine the contact angle of the surface of the modified material, the Washburn method is used, which consists in determining the rate of capillary rise of the test fluid. This method is chosen due to low requirements in the accuracy of measuring equipment and at the same time shows a high degree of accuracy of the results.The object of research is a method for determining the surface energy of powder materials, using aluminium oxide modified with polymethylhydrosiloxane as an example. Surface modifications of the aluminium oxide powder are carried out in a xylene suspension.In the work, the determination of surface energy is carried out in accordance with the Owens-Wendt theory by the graphical method in accordance with the obtained values of the contact angle of the material according to the Washburn method. It is established the shape of the particles of aluminium oxide and their average size, and also calculated the specific surface of the material. A modifier, polymethylhydrosiloxane, is found, with the help of which it is possible to obtain a stable superhydrophobic state, and the optimal concentration by determining the contact angles of the powder material with test liquids according to the method proposed by Washburn.To increase the accuracy of determining the surface energy of the material according to the Washburn method, a mixture of water with ethanol is used, and the components of surface tension are calculated. It is shown that the values of the contact angle of the surface of the dispersed material obtained using a mixture as a test liquid can be used to calculate the values of the components of the surface energy of aluminium oxide. In this case, there is a lack of error in the form of the Cassie state, which is observed for hydrophobic dispersed materials when using water as a test fluid.

Crop science: A foundation for advancing predictive agriculture

Crop science: A foundation for advancing predictive agriculture

Measuring surface energy of carbon nanotubes using modified washburn method

In this study, the Washburn method and Owens and Wendt model were used to estimate the surface energy of an industrial grade multiwalled carbon nanotube (MWCNT) having a carbon purity of 90%. Identical MWCNT beds were prepared and tested using seven different solvents covering wide range of surface tensions and polarities. The solvents were water, diiodomethane, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), toluene, chloroform, and n-hexane. DMF showed the highest affinity towards the MWCNT. Therefore, it was used to determine the packing constant of the MWCNT beds assuming perfect wetting between the MWCNT and DMF. The contact angles between the solvents and MWCNT were fitted using the Owens and Wendt model to calculate the dispersive and polar components of the MWCNT surface energy. The test results showed that the surface energy of the 90% carbon pure MWCNT is with dispersive and polar components of and respectively.