Angle Spreading Research Articles

Transparent superhydrophilic composite coating with anti-fogging and self-cleaning properties

Superhydrophilic coatings have incomparable advantages in anti-fogging and self-cleaning but are limited to poor abrasion resistance and water resistance. Consequently, the research on the contradiction between hydrophilicity and water resistance, as well as abrasion resistance and visible transmittance, has become a focus of superhydrophilic coatings. Herein, we design a ceramic-polymer superhydrophilic composite coating with a high density, strong cross-linking structure, and smooth surface. Because of its static water contact angle (WCA = 3.2°) and short water spreading time (ST = 1878 ms), the transparent composite coating exhibits anti-fogging performance. Meanwhile, it exhibits anti-fogging durability even after 400 Taber abrasion cycles under a 250 g load or immersion in boiling water for 30 min. Furthermore, the result of self-cleaning characterization and theoretical analysis demonstrate that the low surface roughness endows the composite coating with excellent self-cleaning properties. The composite coating can effectively scavenge oil and dust pollution on its surface in a humid environment. Thus, the developed composite coating in this work is potential in the anti-fogging and self-cleaning fields.

Analysis of spark-generated waveforms coalescing in air using schlieren imaging

Mach waves generated by turbulent structures in supersonic jet flows have the potential to intersect and coalesce, a process proposed as a significant contributor to acoustic waveform steepening in the near field of a jet and to the noise referred to as crackle [Baars et al., AIAA (2013); Fiévet et al., AIAA (2016)]. Numerical simulations of intersecting waveforms have demonstrated that coalescence can lead to increased steepening that is dependent on intersection angle, waveform duration, and geometrical spreading [Willis et al., AIAA (2022)]. In this study, two simplified experiments involving a spark source in air are examined. The first involves grazing incidence on a rigid plane to model symmetric intersection between waveforms. The second involves intersecting waveforms emanating from side-by-side openings in a 3D-printed enclosure. Measurements of nonlinear evolution were made for the intersecting waveforms produced with each experimental setup and compared with measurements made for one waveform alone. Schlieren images of the coalescing waves allow for comparison of waveform steepening between the two cases without the limitations imposed by microphones. The measurements permit assessment of the extent to which coalescence enhances waveform steepening. [WAW is supported by the ARL:UT Chester M. McKinney Graduate Fellowship in Acoustics.]

A Model-Derived Empirical Formulation for Wave Run-Up on Naturally Sloping Beaches

A new set of empirical formulations has been derived to predict wave run-up at naturally sloping sandy beaches. They are obtained by fitting the results of hundreds of XBeach-NH+ model simulations. The simulations are carried out over a wide range of offshore wave conditions (wave heights ranging from 1 to 12 m and periods from 6 to 16 s), and surf zone (Dean parameters aD ranging from 0.05 to 0.30) and beach geometries (slopes ranging from 1:100 to 1:5). The empirical formulations provide estimates of wave set-up, incident and infragravity wave run-up, and total run-up R2%. Reduction coefficients are included to account for the effects of incident wave angle and directional spreading. The formulations have been validated against the Stockdon dataset and show better skill at predicting R2% run-up than the widely used Stockdon relationships. Unlike most existing run-up predictors, the relations presented here include the effect of the surf zone slope, which is shown to be an important parameter for predicting wave run-up. Additionally, this study shows a clear relationship between infragravity run-up and beach slope, unlike most existing predictors.

High-temperature CMAS resistance performance of Ti2AlC oxide scales

Failure of thermal barrier coatings (TBCs) caused by glassy deposits mostly composed of calcium-magnesium-aluminium-silicate (CMAS) has become an urgent issue. The addition of Al and Ti elements in TBCs is beneficial to improve the CMAS resistance. In this paper, bi-layered oxide scales were formed through pre-oxidation of Ti2AlC (POTAC) bulks at high temperatures. The wettability and spreading behaviors of CMAS on the oxide scales, as well as the interaction between them were investigated by a sessile-drop method. The glassy CMAS deposit on the Al2TiO5 layer revealed the largest equilibrium contact angle and slowest diffusion-limited spreading rate among all the samples.

Influence of surface roughness on contact angle hysteresis and spreading work

Surface roughness is an important factor that affects dynamic wetting behavior, which can improve the surface hydrophobicity, so it is of great significance to obtain a better understanding of roughness effect from both theoretical and practical perspectives. In this paper, we studied the influence of macro-size surface roughness on contact angle hysteresis and spreading work and analyzed the relationship between contact angle hysteresis and spreading work. Results showed that as the surface roughness increased, both the advancing contact angle and the receding contact angle continued to increase until their maximum values were reached, and then started to decrease within the range of surface roughness studied, while the contact angle hysteresis presented the opposite trend. In addition, with the increase of surface roughness the spreading work initially increased to a certain maximum value, then continuously decreased to the minimum value, and then began to increase within the range of the surface roughness studied. These trends could be attributed to the surface wetting state (Wenzel state, Cassie state, and transition state) changing with the change of surface roughness. These findings can provide guidance for the preparation of wetted surfaces with specific functions, especially when it is required to change the wettability without changing the surface chemical properties.

High-Temperature Wettability Investigations on Laboratory-Developed CaO-CaF2-SiO2 -Al2O3 Flux System-Based Welding Electrode Coatings for Power Plant Applications

This article is an attempt to examines high-temperature wettability properties of laboratory-developed electrode coatings for power plant applications. The properties include contact angle between the solid/liquid interfaces, spreading area, surface tension, and work of adhesion. Coatings were prepared using CaO-CaF2-SiO2 -Al2O3 basic flux system. The sessile drop method was used to estimate the contact angle at the liquid/solid interface while surface tension was calculated using Young’s and Boni’s equations based on the measured contact angle. The interaction effect of individual minerals and their binary mixtures (CaO.CaF2, CaO.SiO2, CaO.Al2O3, CaF2.SiO2, CaF2.Al2O3, and SiO2.Al2O3) on the wettability properties were studied using the regression analysis. Optimum flux compositions were estimated using Multi-response optimization. The contact angle decreases when basic oxides (CaO, CaF2) were added in a higher proportion than the acidic oxides. With the decrease in the contact angle spreading area increased and CaF2 comes out to be the significant constituent causes the increase in the spreading area. Binary mixtures CaO.CaF2, CaO.SiO2, and CaF2.SiO2 has an increasing effect on the work of adhesion.

A Numerical Study of Micro-Droplet Spreading Behaviors on Wettability-Confined Tracks Using a Three-Dimensional Phase-Field Lattice Boltzmann Model.

Wettability-confined tracks have been extensively used in open-surface microfluidic devices for their high capacity of transporting droplet pumplessly. Inspired by the experimental work of Sen et al. [ Langmuir 2018 , 34 , 1899 - 1907 ], in the present study, a three-dimensional phase-field lattice Boltzmann model is developed and used to investigate the spreading behaviors of microdroplet on a series of wettability-confined tracks. The experimental findings are successfully reproduced through our simulation, where three distinct stages of droplet spreading on the horizontal wettability-confined diverging track are fairly exhibited, that is, the initial stage with droplet front spreading quickly, the intermediate stage with both droplet front and bulge moving forward at a constant speed, and the final stage with droplet front decelerating gradually. Moreover, a parametric study of track divergence angle is further performed, and the influential mechanism of track divergence angle on droplet spreading is further revealed. It is demonstrated that track divergence is responsible for the Laplace pressure gradient and capillary force inside the droplet, which drives the droplet bulge to move forward on the diverging track. With an increase in divergence angle, the capillary force increases linearly, which increases the droplet spreading speed at the initial and intermediate stages, while the peak capillary force comes earlier, and consequently the final decelerating stage comes earlier. On the basis of the parametric study and droplet volume conservation rule, a power law relation between track divergence angle and droplet spreading is proposed, which helps to identify the start of final decelerating stage. Finally, the droplet spreading over various inclined tracks is explored, which can be achieved only when the capillary force at the beginning is larger than the droplet gravity component along the inclined track surface.

Production and Characterization of Glutathione-Chitosan Conjugate Films as Systems for Localized Release of Methotrexate.

Cancer is one of the most serious public health problems that affect humanity. Diverse delivery systems of anticancer drugs have been developed to enhance the treatment effectiveness and patient compliance. Thus, drug delivery systems from polymeric films could be an interesting and promising alternative, especially for skin chemotherapeutics. In this work, polymeric films based on glutathione-chitosan conjugates with degrees of thiolation of 4.4%, 5.1% and 7.0% were synthetized by casting-evaporation method and subsequent loading with methotrexate. The surface properties of these films were evaluated by contact angle and spreading rate measurements. The sessile drop methods along with the thermodynamic parameter of work of adhesion were determined using the Young–Dupré semi-empirical model. The in vitro methotrexate release was assessed at a pH of 4.5 and 7.4 simulating physiological conditions. Data from the resulting profiles were fitted to the order one, Higuchi, Peppas–Sahlin and Korsmeyer–Peppas kinetic models. The results suggest a strong relationship between the thiolation degree and hydrophilic surface properties such as contact angle and water spreading rate, whereas the work of adhesion was not significantly affected. Further, these polymer films could control the methotrexate release through diverse mechanisms such as diffusion and relaxation depending on the thiolation degree and the aqueous medium employed. In fact, as thiolation degree increased, the release mechanism shifted from a primary diffusional type towards a predominant relaxation-driven mechanism. These polymer films could be used as modified systems for anticancer local delivery.

Spreading process simulation and optimization of the flight of municipal sludge rotary dryer

In view of flights spreading process of municipal sludge rotary dryer, the holding capacity and spreading model of flights during sludge drum dryer rotation were established, the influence of setting angle and type of flights on flights tilting angle and material spreading uniformity were investigated through MATLAB programming simulation, and then the structure of flights were optimized. It can be found that the order from large to small of tilting angle of different flight types is arc type, bending type and one-section type, the spreading sludge granules uniformity of bending type flight is better than those of one-section and arc type flight, the hinge connecting part of improved flight can ensure the sludge grabbed, and solve outlet difficult problem of sludge granules at the inlet.

Studying the wettability of Si and eutectic Si-Zr alloy on carbon and silicon carbide by sessile drop experiments

The contact angles of two different systems, molten silicon and a eutectic Si-8 at. pct Zr alloy and their evolution over timeon vitreous carbon and polycrystalline silicon carbide (SiC) substrates were investigated at 1500°C under vacuum, as well as in argon using the sessile drop technique. The contact angle and microstructure of the liquid droplet/solid substrate interface were studied to understand fundamental features of reactive wetting as it pertains to the infiltration process of silicon and silicon alloys into carbon or C/SiC preforms. Both pure Si and theeutectic alloy showed good wettability onvitreous carbon and SiC characterized by equilibrium contact angles between 29° and 39°. Theeutectic alloy showed a higher initial contact angle and slower spreading as compared to that of pure Si. On vitreous carbon bothsilicon and the eutecticalloy formed SiC at the interface, while no reaction was observed on the SiC substrates.

Parametric mapping of linear deposition morphology in uniform metal droplet deposition technique

The parametric mapping of linear deposition morphology with different droplet spacing is first proposed, which provides a baseline for parameter selection in uniform metal droplet deposition technique. Experiments related to linear deposition are carried out with deviating droplet size and deposition placement. Deposition morphology is first categorized into inclined region, wave-shaped region and horizontal region. Horizontal region is further classified into overlapped sub-region, clustered sub-region and discrete sub-region. Mathematical models about classification of deposition morphology are established by these initial parameters: offset ratio, merge ratio, solidification angle, and maximum spreading diameter. After mathematical models are established, boundaries between regions are extracted, and then verified by CCD (Charge-coupled Device) photographs and experimental data. Based on the above models and experiment results, the parametric mapping is found and verified. The following conclusions can be drawn: uncontrollable wave-shaped and clustered regions are not suitable for forming parts, hence the selected process parameters should be avoided in the above regions; Controllable inclined, overlapped and discrete regions can be used to forming part, hence the process parameters should fall into these regions. Furthermore, some possible applications are explored corresponding to three controllable regions with the help of the parametric mapping.

Application of sonochemical technique for sustainable surface modification of polyester fibers resulting in durable nano-sonofinishing

In this study firstly we aimed at introducing the effects of ultrasound and sonochemistry in surface modification of polyester fibers. For this purpose, surface modification of polyester fibers was achieved by ultrasound, and contact angle and water spreading time measurements were used to confirm the treatment efficiency. Hydroxylation of terephthalate was occurred by hydroxyl radicals formed during water sonolysis, forming functional groups on polyester surface, as confirmed by XPS analysis, improving the wettability. Creation of hydroxyl groups under sono surface modification was further assessed by dyeing the samples with reactive dye. Secondly, we investigated the durable nano-sono-finishing of polyester fibers by nano TiO2 particles under ultrasonic bath. Washing durability of the sono-synthesized TiO2 nanoparticles was evaluated confirming the effective role of sonochemical technique in polyester surface modification. Thirdly, the self-cleaning activity of sono-synthesized nano TiO2 treated samples toward degradation of Methylene Blue stain was superior to coating of fabric with commercial nano TiO2 using identical procedure.

On the accuracy of CFD simulations of cross-ventilation flows for a generic isolated building: Comparison of RANS, LES and experiments

Accurate and reliable computational fluid dynamics (CFD) simulations are essential for the assessment of cross-ventilation of buildings. To determine which CFD models are most suitable, validation studies are required. A detailed review of the literature indicates that most CFD validation studies only employed the 3D steady Reynolds-averaged Navier-Stokes (RANS) approach and/or focused on a limited set of flow parameters. Therefore, the objective of this paper is the validation of both 3D steady RANS simulations and large eddy simulation (LES) of cross-ventilation in a generic isolated enclosure with wind-tunnel measurements. The evaluation is based on five parameters: mean velocity, turbulent kinetic energy, ventilation flow rate, incoming jet angle and incoming jet spreading width. The RANS simulations are conducted with the standard k-ε (SKE), RNG k-ε, realizable k-ε (RLZ), SST k-ω and RSM turbulence models, whereas the LES is performed with the dynamic Smagorinsky subgrid-scale model. SST/RNG/RSM reproduce the experimentally observed direction of the incoming jet, but all RANS models fail in reproducing the turbulent kinetic energy, which is too low especially above and below the jet, because steady RANS does not capture the vertical flapping of the jet. This transient feature is reproduced by LES, resulting in a better reproduction of all three measured parameters (velocity, turbulent kinetic energy, volume flow rate). It is concluded that choice of the model (RANS vs. LES) actually depends on which parameter is the target parameter, noting that the use of LES entails an increase in computational demand with a factor of ≈80–100.

Effect of Pd, temperature and time on wetting and interfacial microstructure of bulk metallic glasses TiCuZrPd on Ti-6Al-4V substrate

Melting behavior of TiCuZrPd bulk metallic glasses (BMGs) containing 10, 14, 20 at.% Pd was studied by DSC and their melting range is: 845–910, 831–900, 874–911 °C, respectively. Wetting of TiCuZrPd BMGs on Ti-6Al-4V substrate was studied at 850, 880 °C for 5, 10, 30 min. It was found that wetting angle decreases and spreading area increases with increasing temperature and time. Interfacial microstructure of TiCuZrPd/Ti-6Al-4V solidified couples was studied with scanning electron microscopy and energy dispersive spectroscopy. Three intermediate layers were identified at the interface between Ti-6Al-4V substrate and TiCuZrPd BMGs. The first layer adjacent to substrate is composed mostly of Ti, with concentrations of Al lower and V close to that in Ti-6Al-4V, whereas Cu, Pd and traces of Zr are also present. This indicates that this layer was formed by diffusion of Cu, Pd and Zr into substrate. Second layer, adjacent to the first, has higher concentration of Cu compared to the first, there is no V in this layer and concentration of Al is about 50% lower than that in the first. This and the fact that there is no Al in third layer, adjacent to BMG, indicates that Al and V do not diffuse into BMG. In the third layer concentration of Ti is similar to that in the second layer but still 50% higher than in TiCuZrPd, while concentrations of Cu and Zr are lower and concentration of Pd close to that in TiCuZrPd.

Phytosome-hyaluronic acid systems for ocular delivery of L-carnosine.

This study reports on L-carnosine phytosomes as an alternative for the prodrug N-acetyl-L-carnosine as a novel delivery system to the lens. L-carnosine was loaded into lipid-based phytosomes and hyaluronic acid (HA)-dispersed phytosomes. L-carnosine-phospholipid complexes (PC) of different molar ratios, 1:1 and 1:2, were prepared by the solvent evaporation method. These complexes were characterized with thermal and spectral analyses. PC were dispersed in either phosphate buffered saline pH 7.4 or HA (0.1% w/v) in phosphate buffered saline to form phytosomes PC1:1, PC1:2, and PC1:2 HA, respectively. These phytosomal formulations were studied for size, zeta potential, morphology, contact angle, spreading coefficient, viscosity, ex vivo transcorneal permeation, and cytotoxicity using primary human corneal cells. L-carnosine-phospholipid formed a complex at a 1:2 molar ratio and phytosomes were in the size range of 380–450 nm, polydispersity index of 0.12–0.2. The viscosity of PC1:2 HA increased by 2.4 to 5-fold compared with HA solution and PC 1:2, respectively; significantly lower surface tension, contact angle, and greater spreading ability for phytosomes were also recorded. Ex vivo transcorneal permeation parameters showed significantly controlled corneal permeation of L-carnosine with the novel carrier systems without any significant impact on primary human corneal cell viability. Ex vivo porcine lenses incubated in high sugar media without and with L-carnosine showed concentration-dependent marked inhibition of lens brunescence indicative of the potential for delaying changes that underlie cataractogenesis that may be linked to diabetic processes.

Experimental investigation on wetting process of water droplets on micro-/nanoporous copper films

In this paper, the dynamics of contact angle and droplet spreading were combined to study wetting process of droplet on porous media, revealing comprehensive information about surface spreading and internal spreading of the droplet. To precisely locate the precursor rim in the droplet spreading test, background subtraction method was proposed for use in visualizing the precursor rim. Two types of micro-/nanoporous copper films fabricated by an electrochemical deposition method were tested. The results indicated that contact angle of the micro-/nanoporous copper films decreased with time quickly and became 0° at last, which is a result of surface spreading combined with down-absorption. The dynamic of precursor rim velocity which can reflect the kinetics of internal spreading was divided into three stages: friction dominant stage, balance stage and exhausting stage. In the friction dominant stage, the velocity of precursor rim can be described by an exponential law, while the velocity of precursor rim in balance stage, which is only affected by the internal characteristics of porous media, was proposed to compare internal wettability of porous media.

Effect of Nanofillers on the Spreading Behavior of Biopolymer Materials on Urea Surface

This paper presented new approach where a new modified biopolymer reinforced with bentonite nanoclay is developed and used as the coating material for controlled-release fertilizer. Good wettability properties between coating material and urea surface is necessary to provide uniformity during the coating process of controlled release fertilizer. Seven different blending ratio of modified biopolymer solutions are prepared and evaluated for their wettability properties. The wettability properties measured include the surface tension, contact angle and maximum spreading diameter. Optical Contact Angle device comes with a Charged-Coupled Device (CCD) camera was used to capture every single image of the droplet impact behavior. From the analysis, it is proven that with addition of 2% nanoclay filler reinforced into modified biopolymer with blending ratio of 50/15/2.5/7.5 has the best wettability properties and provides better spreading behavior.

Superhydrophilicity on microstructured titanium surfaces via a superficial titania layer with interconnected nanoscale pores

Microstructured titanium (Ti) surfaces often suffer from poor hydrophilicity which makes the realization of open microfluidic devices difficult. Here, we investigate the effect of a superficial porous titania (TiO2) layer on the hydrophilicity of microstructured surfaces. High aspect ratio Ti micropillars were micromachined from bulk Ti sheets. Porous TiO2 was subsequently grown on Ti micropillars by a wet oxidation route followed by thermal annealing. Porous TiO2 was characterized using atomic force microscopy, x-ray diffraction and x-ray photoelectron spectroscopy. Detailed morphology study and pore size analysis were carried using focused ion beam machining coupled with scanning electron microscopy. Static contact angle and dynamic spreading studies clearly demonstrate enhanced hydrophilicity of microstructured Ti surfaces with a superficial porous TiO2 layer. Such enhancement promises interesting applications in the microfluidics and microsystems fields.

Frequency and angle spreading due to rough interface scattering

A narrow band passive sonar system sensing propagation of acoustic energy reflected from the ocean bottom in shallow water incurs detection losses due to frequency and angle limitations of the processor and receiving array. These losses are expressible as ratios of integrals of a suitably defined bottom scattering function. This talk presents a modeling approach which uses propagation calculations and a tangent plane approximation to the Helmholtz scattering integral at planes within a layered bottom sediment to analyze sensitivities of the spreading problem and to predict system losses. Model results for a few hypothetical but representative sonar systems will be presented.

A Novel On-Eye Wettability Analyzer for Soft Contact Lenses

To develop novel methodology to assess two in vivo wettability parameters, contact angle and index of liquid spreading (ILS), for hydrogel contact lenses and to provide a comprehensive investigation of the measurement errors (repeatability) associated with these two parameters. A Novel On-eye Wettability Analyzer (NOWA) was constructed which delivered a drop of 0.4% sodium hyaluronate mixed with sodium fluorescein directly on to a lens surface in vivo while a two-camera digital system recorded both the resultant contact angle and liquid spreading. Ten subjects each wore a different etafilcon A lens (-0.50 DS) in the right eye for 30 min before measurement on three separate occasions. For contact angles, the coefficient of repeatability (COR) associated with three measurement conditions (image analysis COR, intrasubject COR, and intersubject COR) was determined. For ILS, the COR associated with two measurement conditions (intrasubject COR and intersubject COR) was also determined. The in vivo contact angle for the etafilcon A lens was 19.8° ± 2.9° (mean ± standard deviation). COR values for contact angle were 3.2°, 5.2°, and 8.0° for image analysis, intrasubject measures, and intersubject measures, respectively. The mean ± standard deviation ILS was 2.0 ± 0.3 mm, and COR values were 0.4 and 0.8 mm for intrasubject and intersubject measures, respectively. This research demonstrates that it is possible to obtain hydrogel lens contact angles in vivo and to provide a new wettability parameter (ILS) with the NOWA instrumentation. The COR values obtained were considered to be acceptable. Intersubject COR values were greater than intrasubject COR values for both contact angle and ILS; this is likely to be due to greater variability of tear film characteristics between subjects than within an individual. The use of this novel methodology and its associated clinical parameters across a wider range of lens types in various clinical situations warrants further investigation.