Variation Of Wettability Research Articles

Wetting of graphite by molten Cu–xSn–yCr ternary alloys at 1373 K

This paper presents an experimental approach where the effect of Cr and Sn concentrations on the wetting of graphite by molten Cu-xSn-yCr ternary alloys at 1373 K. It shows that a small quantity of Cr addition (≤2 at.%) can improve the wettability significantly owing to the formation of chromium carbides at the interface. Sn addition (x ≤ 30 at.%) can further improve the wettability by decreasing the surface tension. However, higher Sn concentration (x ≥ 40 at.%) will cause the precipitation of main phase at the interface, varying from Cr7C3 to Cr3C2, which in turn will slightly deteriorate the wettability. The phase equilibrium transition point (x ≈ 35% in Cu–xSn–1Cr/Cgraphite) is responsible for wettability variation by the increase of Sn concentration. When the Sn concentration is ≥ 40 at.%, the spreading dynamics are satisfied with the assumption of the classical diffusion-limited spreading model. When the Sn concentration is ≤ 30 at.%, the transport route of Cr is from the Sn segregation layer on the drop surface to the triple line rather than from the internal diffusion of the bulk drop to the triple line, and then a precursor film with the specific width can be formed.

P.181 Machine learning for classification of cognitive impairment according to antipsychotic dopamine receptor occupancy and illness severity in late-life schizophrenia

Hydrodesulfurization of heavy oil is usually operated in a trickle bed reactor. Analysis and design of this reactor require modeling both at the macro-reactor scale and micro-catalyst scale. The paper is focused on the catalyst-level modeling and takes into consideration complex catalyst shapes, wettability, and spatial variation in diffusivity due to catalyst pore plugging. Furthermore, the effects of mass transfer from dry and wet zones around the partially wetted catalyst surface are included. Finite element method is used for two-dimensional analysis as it is versatile and can handle complex shapes. The catalyst-level model includes an updating of effective diffusivity with time, and hence the lifetime of a complex shaped catalyst can be predicted. Long-time operation shows that thickness of plugged pore is large and also non-uniform across the two-dimensional catalyst particle with more plugging near the catalyst surface. In addition, the reaction regime changes with time, the fresh catalyst initially being in a diffusion-resistance-free regime and changing to a strong-diffusion-resistance regime at longer operating times. The computational method can be used for optimization of the operating protocol and to design optimum pore size and shape of the catalyst, although these details are not addressed in this paper.

Modeling of Co-current Spontaneous Imbibition Oil Recovery from Partially Covered Homogeneous Hydrocarbon Reservoir

In this paper, an approximate integral equation solution for a horizontal, unsteady flow of two viscous incompressible fluids is derived. Wettability variation of the porous medium is also considered in the present study. The non-wetting phase recovery fraction is obtained in terms of dimensionless time for 1D model from the derived solution. The derived approximate recovery fraction has been compared with the existing experimental data and empirical correlations for spontaneous imbibition from water-wet medium. It is observed that the normalized water saturation profiles show sharp gradients indicating some instability of the water front. Hence, a linear stability analysis is developed to study viscous instability of the co-current spontaneous imbibition. Viscous instability phenomenon for a two-phase oil–water system is also discussed. The corresponding instability number related to co-current imbibition recovery is estimated. The present study clearly spells out the effect of the instability number on the recovery process and estimates a critical instability number for co-current spontaneous imbibition.

Investigation on dielectric and mechanical properties of epoxy reinforced with glass fiber and nano-silica composites

The composite materials of different filler concentration were fabricated by reinforcing the glass fiber and silica nanoparticles into epoxy to understand the variation in surface wettability, water droplet initiated discharge, dielectric parameters, surface charge, space charge and mechanical properties. Nanofiller inclusion has shown the enhanced surface properties viz. water droplet initiated corona inception voltage (CIV) and hydrophobicity. CIV is high under negative DC voltage followed with positive DC and AC voltage. It is realized that the dielectric constant is increased with the addition of nano-silica. The surface potential has decayed exponentially irrespective of the applied voltage polarity and the type of the sample, whereas, the 3 wt% sample showed the highest decay rate for an applied voltage. Silica filled composites have shown better space charge accumulation and decay characteristics initially and then deteriorated rapidly when the filler concentration is increased. The optimised filler concentration is found considering the minimal space chare accumulation, decay rate and the optimised electric field for the space charge analysis. Further, the optimised field conditions were devised for the optimum filler concentration for the prolonged life span and reliability of the insulation material. The mechanical storage modulus has increased with the addition of nanofiller. The plasma temperature calculated from the LIBS spectra has shown a direct correlation with the surface hardness of the material.

Photothermal Actuation of Diverse Liquids on an Fe3O4-Doped Slippery Surface for Electric Switching and Cell Culture.

The photoinduced manipulation of liquids on a slippery lubricant-infused porous surface (SLIPS) has attracted a tremendous amount of attention because of its merits of contactless stimulation and excellent spatial and temporal control. However, tedious fabrication methods by a combination of template transfer and fluorination for a photothermal-material-doped SLIPS and the lack of deeper systematically quantitative analysis with respect to droplet hydrokinetics are greatly perplexing in both academic research and industrial applications. Here we demonstrate a kind of Fe3O4-doped SLIPS by one-step femtosecond laser cross-scanning, which can readily steer diverse liquids toward arbitrary directions with a fast velocity of up to 1.15 mm/s in the presence of a unilateral NIR stimulus. The underlying mechanism is that the wettability gradient force (Fwet-grad) induced by the temperature gradient arising from asymmetric near-infrared-irradiation (NIR) loading would be generated within 1 s to actuate a targeted droplet's sliding behavior. Through tuning the NIR irradiating sites, we can slide a targeted droplet with controllable directions and routes. On the basis of fundamental physics, we have quantitatively analyzed the relationship among Fe3O4-doped content, lubricant rheological performance, droplet wettability variations, Fwet-grad, and the sliding velocity for diverse liquid species. Accordingly, we can remotely steer liquid droplets to realize the on-off state of an electrical circuit on demand, the droplet fusion of a microfluidic reactor, and the culture/inhibition of biological cells.

Femtosecond laser microstructuring of alumina toughened zirconia for surface functionalization of dental implants

The continuous need for high-performance implants that can withstand mechanical loads while promoting implant integration into bone has focused recent research on the surface modification of hard ceramics. Their properties of biocompatibility, high mechanical and fatigue resistance and aesthetic color have contributed to its succefull applications in dentistry. Alumina toughened Zirconia (ATZ) has been gaining attention as a material for dental implants applications due to its advanced mechanical properties and minimal degradation at body temperature. Still, in order to improve tissue response to this bioinert material, additional modifications are desirable. Improving the surface functionality of this ceramic could lead to enhanced implant-tissue interaction and subsequently, a successful implant integration.In this work, microtopographies were developed on the surface of Alumina toughened Zirconia using an ultrafast laser methodology, aiming at improving the cellular response to this ceramic. Microscale grooves and grid-like geometries were produced on ATZ ceramics by femtosecond laser ablation, with a pulse width of 150 fs, wavelength of 800 nm and repetition rate of 1 kHz. The variation of surface topography, roughness, chemistry and wettability with different laser processing parameters was examined.Cell-surface interactions were evaluated for 7 days on both microstructured surfaces and a non-treated control with pre-osteoblasts, MC3T3-E1 cells. Both surface topographies showed to improve cell response, with increased metabolic activity when compared to the untreated control and modulating cell morphology up to 7 days.The obtained results suggest that femtosecond laser texturing may be a suitable non-contact methodology for creating tunable micro-scale surface topography on ATZ ceramics to enhance the biological response.

Impact of non-uniform wettability in the condensation and condensation-liquid water intrusion regimes in the cathode gas diffusion layer of proton exchange membrane fuel cell

The impact of variations in the wettability properties of the gas diffusion layer substrate on the liquid water distribution and the reactant gas access is studied from pore network simulations considering two main cases: a degradation case where the fraction of hydrophilic pores increases and a case where the spatial distribution of the hydrophobic agent is non-uniform with hydrophobic surfaces and a central region of mixed wettability. Contrary to previous works, this impact is assessed for various regimes of liquid water occurrence. The latter notably include the condensation regime and the mixed regime where the occurrence of liquid water in the gas diffusion layer results from both condensation under the rib and the ingress of liquid water from the catalyst layer or the microporous layer. The study shows that the wettability variation impact is highly dependent on the regime, i.e. on the operating conditions. Whereas this impact is minor when the conditions correspond to the occurrence of the pure condensation regime where the liquid water is confined in the region below the rib, it can be quite significant in the mixed regime when the conditions are such that liquid water is present also in the region below the channel.

Synthesis, characterization and evaluation of bioactivity of glasses in the CaO-SiO2-P2O5-MgO system with different CaO/MgO ratios

Bioactive glasses (80Mg, 70Mg, 60Mg and 50Mg) in the system SiO2-CaO-P2O5-MgO were prepared by sol-gel method and then characterized. The structure of the synthesized samples has been studied by X-ray diffraction (XRD), Fourrier Transform Infrared Spectroscopy (FTIR) and Environmental Scanning Electron Microscopy (ESEM). In vitro bioactivity tests were performed in Simulated Body Fluid (SBF). The apparent density and wettability variation with time were measured. The in vitro studies showed the formation of an apatite-like layer covering areas of the material surface. The variation in the CaO/MgO ratio has an influence on the chemical durability and bioactivity. The XRD and FTIR analysis revealed that the samples with larger CaO/MgO ratio exhibited better bioactivity. The results showed that the 50Mg glass which has the higher content of CaO/MgO is hydrophilic sample for the two used fluids (water and SBF). The porosity and hydrophilicity increase with increased the rate of CaO/MgO. The surface of bioglasses became rougher with the increased CaO/MgO ratio, which may lead to a decrease in water contact angle.

Characterization of Organic Layer in Oil Carbonate Reservoir Rocks and its Effect on Microscale Wetting Properties

Effective production of oil from carbonate reservoirs often requires the application of improved oil recovery technologies such as waterflooding. However, conventional waterflooding in carbonates usually results in low hydrocarbon recovery as most of these formations exhibit a complex pore throats structure and are mostly oil-wet. Therefore, improved insight into the causes of hydrophobic wetting behavior of such reservoirs is important for understanding the fluid distribution, displacement and enhancing recovery processes. The characterization of fluid-rock interactions is, however, challenging with existing laboratory methods, which are typically based on macroscale (mm) observations. In this experimental study, an advanced imaging technique, namely environmental scanning electron microscope, was applied for the comprehensive investigation of microscale (µm) wettability variations in carbonate rocks covered with organic layers. For the first time, the presence of organic layers on the sample was proved using energy dispersive X-ray mapping. Furthermore, the chemical bond of this layer and carbonate rock surfaces was determined using the transmission electron microscopy and electron energy-loss spectroscopy. The thickness of layer was estimated by using image processing software. These findings show that the application of combined microscopic techniques reveals important details about the reason of hydrophobic wetting properties of real carbonate rocks.

Modeling and evaluation of hydrodesulfurization and deactivation rates for partially wetted Trilobe catalyst using finite element method

Hydrodesulfurization of heavy oil is usually operated in a trickle bed reactor. Analysis and design of this reactor require modeling both at the macro-reactor scale and micro-catalyst scale. The paper is focused on the catalyst-level modeling and takes into consideration complex catalyst shapes, wettability, and spatial variation in diffusivity due to catalyst pore plugging. Furthermore, the effects of mass transfer from dry and wet zones around the partially wetted catalyst surface are included. Finite element method is used for two-dimensional analysis as it is versatile and can handle complex shapes. The catalyst-level model includes an updating of effective diffusivity with time, and hence the lifetime of a complex shaped catalyst can be predicted. Long-time operation shows that thickness of plugged pore is large and also non-uniform across the two-dimensional catalyst particle with more plugging near the catalyst surface. In addition, the reaction regime changes with time, the fresh catalyst initially being in a diffusion-resistance-free regime and changing to a strong-diffusion-resistance regime at longer operating times. The computational method can be used for optimization of the operating protocol and to design optimum pore size and shape of the catalyst, although these details are not addressed in this paper.

Brazing temperature-dependent interfacial reaction layer features between CBN and Cu-Sn-Ti active filler metal

CBN/Cu-Sn-Ti (CBN: cubic boron nitride) composites are prepared by active brazing sintering at 1123 K, 1173 K, 1223 K and 1273 K, respectively. The effects of brazing temperature on the wettability, interfacial characteristics, and elemental distribution variations are fully investigated. When the brazing temperature is below 1223 K, completely uncoated and/or partially coated CBN particles with sharp edges can still be observed, and the reaction layer, mainly composed of TiN and TiB2, appears to be thin and uneven. When the brazing temperature is 1223 K, all CBN particles are completely coated, suggesting that adequate wetting has taken place. Besides, as Ti diffuses thoroughly and enriches the interface, the reaction layer, filled primarily by TiN, TiB2 and TiB, becomes thicker (about 1.30 μm), more uniform, stable and continuous. Further increasing the temperature to 1273 K is unnecessary or even harmful as the reaction layer thickness undergoes negligible change yet some tiny micro-cracks appear on the interface, which may likely deteriorate the grinding capability of the final brazing products.

Fresh underground light non-aqueous liquid (LNAPL) pollution source zone monitoring in an outdoor experiment using cross-hole electrical resistivity tomography.

Real-time monitoring of source zone of light non-aqueous liquids (LNAPLs) is important for preventing accidental pollution and taking effective underground pollution remediation measures. As a high-precision monitoring technology, cross-hole electrical resistivity tomography (CHERT) has been widely used to obtain static information regarding underground stratigraphic structures and dynamic information regarding fluid motion. The time-lapse data processing method can be used to obtain pollution zone dynamic change information. Since the leakage rate directly affects the diffusion range of pollution, this study simulated the initial evolution process of LNAPL pollution source regions under two different leakage rates. The time-lapse monitoring of the above process was performed using CHERT. The test results show that CHERT can be used to observe the migration of LNAPLs and the initial evolution of the contaminated area. Differences in leakage rate will result in variation in soil wettability and fluid distribution, which will cause changes in soil resistivity in the corresponding region. The low-saturation LNAPL-contaminated area may exhibit low-resistivity characteristics and is easily overlooked in field investigations. In addition, the degree of contamination in the saturated zone can be quantitatively evaluated by CHERT; however, the pollution range and oil saturation value determined by CHERT are underestimated. The results showed the electrical variation characteristics of the initial evolution process of the fresh pollution source area and provide data that will enable early warnings of LNAPL leakage. This shows that CHERT is a promising tool for monitoring LNAPL pollution source leakage even if further research is needed to fully understand the effect of hydrological processes on electronic signals.

Superhydrophobic polytetrafluoroethylene surfaces with accurately and continuously tunable water adhesion fabricated by picosecond laser direct ablation

Superhydrophobic polytetrafluoroethylene (PTFE) surfaces with accurately and continuously tunable water adhesion were fabricated by a simple and rapid method of picosecond (ps) laser direct ablation. By simply changing laser scan intervals (LSIs) from 5 to 140 μm, three laser-ablated PTFE surfaces, i.e., the two superhydrophobic surfaces with ultralow water adhesion and with tunable water adhesion, and the ordinary hydrophobic surface with ultrahigh water adhesion, could be obtained. Here, the sliding angles of water droplets on these surfaces could be continuously varied from about 1° to about 90°. XPS analysis suggested that the continuous variations of water adhesion and wettability were probably attributed to the change of surface microstructure and not to that of chemical composition. SEM analysis showed that different LSIs resulted in different surface microstructures and different area ratios of the laser-ablated regions to the pristine regions. This was because of the composite ablation process of photothermal and photochemical effects of the special ps laser wavelength (355 nm) and pulse duration (about 10 ps). The tunable water adhesion was verified by the coalescence-induced droplets jumping behavior. This study will provide a novel and versatile method for the rapid fabrication of superhydrophobic material surfaces with accurately and continuously tunable adhesion.

A nanoneedle-based reactional wettability variation sensor array for on-site detection of metal ions with a smartphone

An enhancement of the reactional wettability variation (RWV) sensing strategy is achieved based on the wettability switch of a nanoneedle surface. The sensor unit is formed by coating hydrophobic azoimidazole compounds, as the responder compounds onto the originally hydrophilic surface of cobalt hydroxide nanoneedles. The complexation reaction between metal ions and azoimidazole ligands etches the hydrophobic coating and switches the surface wettability, making the surface hydrophilic again. This switch is revealed by a decrease in the static contact angle (CA) and an increase in the sliding angle of the surface. The reactivity is tuned by the derivatization and conformational manipulation of the azoimidazole compounds. A sensor array composed of six as-tuned sensor units is constructed to distinguish among the species and concentrations of Fe3+, Ni2+ and La3+ at a low limit of 10−6 M using the chemometric method of principal component analysis (PCA). In addition, a new on-site detection strategy is developed based on PCA of the sliding angle, which can be measured conveniently and swiftly with a smartphone app and a commercially available setup. The application of the general RWV strategy is envisioned to open new possibilities for on-site detection.

Effect of pore size and wettability of multilayered coalescing filters on water-in-ULSD coalescence

Coalescing filters are generally used to increase the size of the small drops for their separation from gases and liquids. Many studies have been performed on coalescing filter media. The performances become much more complicated for multilayered media having different properties and systematic studies are needed. Wettability, pore size, face velocity and wetting properties are among the important factors controlling performance. In this work, microscopic studies were performed to visually observe coalescence of water droplets on hydrophilic Nylon and hydrophobic Polypropylene woven sheets in a water-in-diesel emulsion at different face velocities and spacings between the sheets. The combination of hydrophobic sheet followed by hydrophilic sheet had the best performance. Statistical analysis of variance showed that the variations of distance between sheets and the face velocity were not significant factors. To better understand the effects of multilayers in filter performance, pilot scale experiments of stacked layers of woven sheet media of different thicknesses and wetting properties were conducted. Thin media had poor performance, but the performance improved and reached a plateau as the thickness increased. Effects of fiber surface wettability and pore size variations in the layers were also evaluated. Similar to microscope results, the coalescence performance was better for dual layer media with different wetting properties of each layer compared to dual layer media having the same wetting properties of each layer. The pore size was a dominant parameter affecting the performance. When pore size was similar to the average drop size of the water in the upstream, the best performance was observed. For dual layer filters having one layer of small pores and the other of large pores, the observed performance was lower than that of dual layer filters having only large pores but higher than the filters having only small pores.

Wetting Properties of Polyetheretherketone Plasma Activated and Biocoated Surfaces

Polyetheretherketone (PEEK) biomaterial is a polymer which has been widely used since the early 90s as a material for human bone implant preparations. Nowadays it is increasingly used due to its high biocompatibility and easily modeling, as well as better mechanical properties and price compared to counterparts made of titanium or platinum alloys. In this paper, air low-temperature and pressure plasma was used to enhance PEEK adhesive properties as well as surface sterilization. On the activated polymeric carrier, biologically-active substances have been deposited with the Langmuir-Blodgett technique. Thereafter, the surface was characterized using optical profilometry, and wettability was examined by contact angle measuring. Next, the contact angle hysteresis (CAH) model was used to calculate the surface free energy of the modified surface of PEEK. The variations of wettability and surface free energy were observed depending on the deposited monolayer type and its components.

Modification of a Poly(tetrafluoroethylene) Porous Membrane to Superhydrophilicity with Improved Durability

AbstractThe commercial fluorocarbon surfactant (FCS) DuPont™ Zonyl 321 fluorinated cationic surfactants, was employed to modify both flat‐sheet and hollow‐fiber poly(tetrafluoroethylene) (PTFE) porous membranes. The variation of morphology, wettability, and hydrophilicity durability to acid and alkali as well as the filtration performance of both membranes were investigated. Such superhydrophilic membranes showed better wetting stability and higher resistance to acid and alkali solutions. Moreover, both membranes exhibited good filtration performance.

The effect of electrical charge density on the transition behavior between bonding and clogging stages of an electroplated porous surface

A copper plate with a porous layer on its outer surface can significantly enhance heat transfer performance compared with a smooth copper plate. In this work, different from the traditional powder sintering technique, a porous layer consisting of copper powders was prepared by an electroplating method. The bonding mechanism of this electroplated porous surface was analyzed by using scanning electron microscope (SEM) imaging and the X-ray diffraction (XRD) technique. The influences of the electrical charge density adopted in the preparation process on the appearance and oxide phase of the electroplated porous surface were investigated by a 3D optical profiler and energy dispersive spectroscopy (EDS) technique. Moreover, the bonding strength and anti-disturbance ability of the electroplated porous surface were summarized via a thrust test and an ultrasonic vibration test, respectively. Using water droplet spreading and down-absorption tests, the variation of wettability of the prepared porous surface was discussed. With an optimum electrical charge density, it is feasible to securely construct copper powders onto a substrate and form an inter-connective porous layer without compromising its mechanical and porous properties.

Superhydrophobic Plant Leaves: The Variation in Surface Morphologies and Wettability during the Vegetation Period.

In this paper, for the first time, the surface wettability of cloverleaves and lotus leaves with specific surface structures at different growth stages is investigated. It is found that the clover exhibits water-repellent property similar to lotus leaves. Furthermore, the alternation in wettability of cloverleaves and lotus leaves during the whole vegetation period is investigated. The water contact angles and surface morphology of the leaves are measured by means of contact angle measurements and scanning electron microscopy, respectively. The chemical composition of plant leaves is analyzed utilizing Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. It is found that the wettability heavily depends on the surface structures during their growth and aging procedure, which enlightens us to design and fabricate biomimetic multifunctional superhydrophobic surfaces inspired by nature.

Hierarchically aligned gradient collagen micropatterns for rapidly screening Schwann cells behavior.

To penetrate the effect of protein gradient micropattern on peripheral nerve regeneration, the hierarchically aligned gradient collagen micropattern was prepared by micromoulding method and the influence on Schwann cells growth behavior was studied. The morphology, wettability, stability and component variation of the micropatterns were firstly characterized. Then, Schwann cells were cultured and the related mechanism was penetrated. The results showed that the gradient collagen micropattern could be well fabricated. The surface wettability varied with the change of collagen concentration, and the prepared gradient micropattern showed a good stability after PBS immersion for 15 days. The results of Schwann cells culture and morphological index analysis displayed that the prepared gradient collagen micropatten could well regulate the orientation growth of Schwann cells, while a much better cell alignment growth was obtained on the gradient micropattern with higher collagen concentration and wider pattern size. PCR and WB showed that the micropattern structure could effectively up-regulate the key specific genes for axon regeneration and myelination process. Overall, the study provides a systematic and facile method for understanding the effect of various sized micropatterns on cell behavior, which may have a great significance for the development of artificial implants for tissue engineering and regenerative medicine.