Calculation Of Surface Free Energy Research Articles

A cost effective strategy to fabricate STA@PF@Cu2O hierarchical structure on wood surface: aimed at superhydrophobic modification

Cuprous oxide nanoparticles (Cu2O NPs), phenol formaldehyde (PF) resin, and stearic acid (STA) were used to fabricate hierarchical core/shell structures to endow wood with superhydrophobic function, in which the preparation of Cu2O NPs and the synthesis of PF were carried out simultaneously in one system. The Cu2O NPs with the shape of a symmetrical tetrahexahedron were prepared in this work, and this novel shape is beneficial for creating a superhydrophobic surface. A relatively rough structure in micro/nanoscale was formed on the wood surface after being sprayed with PF@Cu2O coating, which played a vital role in the fabrication of superhydrophobic wood surfaces, as expected. Morphological analysis and surface free energy calculations verified that STA reduced the surface free energy. Application of 12 layers of PF@Cu2O coating followed by 2 h immersion in STA ethanol solution produced wood surfaces with low water permeability and high water contact angles of 153.3°, 153.2°, 150.5° on cross, radial, and tangential sections, respectively. Abrasion tests coupled with subsequent exposure to acidic and alkaline conditions indicated that the coating was resistant to both mechanical wear and chemical degradation. This two-step coating strategy used inexpensive ingredients and could have potential to application as water repellency protection of wood timber.

Impacts of surface wettability and roughness of styrene-acrylic resin films on adhesion behavior of microalgae Chlorella sp

Biofilm attached cultivation is a promising method for efficient production of microalgae. Determining the surface property index to select an appropriate substrate benefiting the algae adhesion and biofilm formation is very important for the cultivation method. This work focused on elucidating and quantifying the influence of surface wettability and roughness of substrate on Chlorella vulgaris adhesion. Firstly, surface modified styrene-acrylic (SA) resin films by adding different dosage of perfluoroalkyl ethyl acrylate (FM) were prepared. Property characterization shows that the surface contact angle in water, formamide and diiodomethane of FM modified SA films is significantly associated with the FM dosage, while the other surface properties including zeta potential, surface potential and surface roughness have insignificant difference. The calculated surface free energy parameters show that the SA films belong to the non-polar substrata. A well quantitative correlation that the adhesion capacity of C. vulgaris linearly declines with the increase of water contact angle was obtained. And a near linear relationship between the adhesion capacity and the surface free energy (γ), or the cohesion free energy (ΔGcoh) was also observed. Secondly, the surface roughness solely changed SA films were prepared by replicating the morphology of stainless steel sieves through the PDMS template method. The patterned SA films have alternately arranged rectangular “valleys” and “ridges”. A well linear correlation between the microalgae adhesion capacity and the surface roughness was also obtained.

Comparison of the Physicochemical Properties of Carboxylic and Phosphonic Acid Self-Assembled Monolayers Created on a Ti-6Al-4V Substrate.

This study compared the tribological properties in nano- and millinewton load ranges of Ti‑6Al-4V surfaces that were modified using self-assembled monolayers (SAMs) of carboxylic and phosphonic acids. The effectiveness of the creation of SAMs with the use of the liquid phase deposition (LPD) technique was monitored by the contact angle measurement, the surface free energy (SFE) calculation, X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FTIR) measurements. The obtained results indicated that more stable and well-ordered layers, which were characterized by the lowest values of the coefficient of friction, adhesion, and wear rate, were obtained using phosphonic acid as a surface modifier. Based on the obtained results, it was found that the Ti-6Al-4V alloy modified by phosphonic acid would be the most advantageous for practical applications, especially in micro- and nanoelectromechanical systems (MEMS/NEMS).

Surface Activation of Polylactic Acid-Based Wood-Plastic Composite by Atmospheric Pressure Plasma Treatment.

Wood-plastic composite (WPC) based on a polylactic acid (PLA) matrix is a promising material since it is biobased, degradable, sustainable, and 3D printable. However, due to its coloring, visible layers after 3D-printing, and small build volumes of these printers, a coating or gluing of parts might be required. This study investigates the influence of a dielectric barrier discharge (DBD) plasma treatment of PLA-based WPC to activate the surface and improve, e.g., coating capabilities. X-ray photoelectron spectroscopy (XPS) measurements showed the oxidation of the surface due to the formation of carbonyl and carboxyl groups. Laser scanning microscopy revealed a surface roughening after the treatment. Contact angles of water and diiodomethane decreased significantly after the plasma treatment and the consecutively calculated surface free energy increased. Finally, two practical adhesion tests revealed an improvement of the applied acrylic dispersion coating’s adhesion to the WPC surface: The assigned cross-cut class improved, and the pull-off strength increased from 1.4 to 2.3 N/mm2.

Oxygen plasma surface treatment of polymer films—Pellethane 55DE and EPR-g-VTMS

A systematic study using a central composite design of experiments (DoE) was performed on the oxygen plasma surface modifications of two different polymers—Pellethane 2363-55DE, which is a polyurethane, and vinyltrimethoxysilane-grafted ethylene-propylene (EPR-g-VTMS), a cross-linked ethylene-propylene rubber. The impacts of four parameters—gas pressure, generator power, treatment duration, and process temperature—were assessed, with static contact angles and calculated surface free energies (SFEs) as the main responses in the DoE. The plasma effects on the surface roughness and chemistry were determined using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Through the sufficiently accurate DoE model evaluation, oxygen gas pressure was established as the most impactful factor, with the surface energy and polarity rising with falling oxygen pressure. Both polymers, though different in composition, exhibited similar modification trends in surface energy rise in the studied system. The SEM images showed a rougher surface topography after low pressure plasma treatments. XPS and subsequent multivariate data analysis of the spectra established that higher oxidized species were formed with plasma treatments at low oxygen pressures of 0.2 mbar.

Preferred growth direction of III–V nanowires on differently oriented Si substrates

One of the nanowire (NW) characteristics is its preferred elongation direction. Here, we investigated the impact of Si substrate crystal orientation on the growth direction of GaAs NWs. We first studied the self-catalyzed GaAs NW growth on Si (111) and Si (001) substrates. SEM observations show GaAs NWs on Si (001) are grown along four <111> directions without preference on one or some of them. This non-preferential NW growth on Si (001) is morphologically in contrast to the extensively reported vertical <111> preferred GaAs NW growth on Si (111) substrates. We propose a model based on the initial condition of an ideal Ga droplet formation on Si substrates and the surface free energy calculation which takes into account the dangling bond surface density for different facets. This model provides further understanding of the different preferences in the growth of GaAs NWs along selected <111> directions depending on the Si substrate orientation. To verify the prevalence of the model, NWs were grown on Si (311) substrates. The results are in good agreement with the three-dimensional mapping of surface free energy by our model. This general model can also be applied to predictions of NW preferred growth directions by the vapor-liquid-solid growth mode on other group IV and III–V substrates.

Influence of Conditions for Production and Thermo-Chemical Treatment of Al2O3 Coatings on Wettability and Energy State of Their Surface

This article presents the influence of the anodizing parameters and thermo-chemical treatment of Al2O3 coatings made on aluminum alloy EN AW-5251 on the surface free energy. The oxide coating was produced by DC (Direct Current) anodizing in a ternary electrolyte. The thermo-chemical treatment of the oxide coatings was carried out using distilled water, sodium dichromate and sodium sulphate. Micrographs of the surface of the Al2O3 coatings were characterized using a scanning microscope (SEM). The chemical composition of the oxide coatings was identified using EDS (Energy Dispersive X-ray Spectroscopy) microanalysis. Surface free energy (SFE) calculations were performed by the Owens–Wendt method, based on wetting angle measurements made using the sessile drop technique. The highest value of surface free energy for the only anodized coatings was 46.57 mJ/m2, and the lowest was 37.66 mJ/m2. The contact angle measurement with glycerine was 98.06° ± 2.62°, suggesting a hydrophobic surface. The thermo-chemical treatment of the oxide coatings for most samples contributed to a significant increase in SFE, while reducing the contact angle with water. The highest value of surface free energy for the coatings after thermo-chemical treatment was 77.94 mJ/m2, while the lowest was 34.98 mJ/m2. Taking into account the contact angle measurement with glycerine, it was possible to obtain hydrophobic layers with the highest angle of 109.82° ± 4.79° for the sample after thermal treatment in sodium sulphate.

Thickness-dependent morphology, microstructure, adsorption and surface free energy of sputtered CeO2 films

Thickness plays a key role in determining the surface morphology, microstructure and properties of films. Herein, CeO2 films with different thickness were deposited onto silicon substrates by magnetron sputtering. Prepared films exhibited preferred crystal orientation of (111) plane, which had the smallest surface energy compared to other crystal orientations. Film thickness affected the surface morphology, microstructure, surface chemistry, as well as wetting properties of CeO2 films. With increasing film thickness, the grain size became larger and the root-mean-square (RMS) roughness increased. More oxygen vacancies were detected for the thicker film, which enhanced the hydrocarbon adsorption and reduced the wetting, the water contact angle could reach 101.8°. In addition, surface free energy calculations showed that the interaction between water and film surface was mainly electrostatic and surface free energy decreased when the film became thicker. Such films with varying thickness and controllable wettability could find various practical applications.

Epoxy coatings with increased hydrophobicity modified by isocyanurate containing siloxane

Isocyanurate containing siloxane was employed for modification of high - solid epoxy coatings based on diglycidyl ether of bisphenol A, which were cured with isophorone diamine. The structure of the samples was investigated by FTIR spectroscopy. The thermal behavior was studied by differential scanning calorimetry and thermogravimetric analysis. Hydrophobicity of coatings was determined by contact angle measurements and by calculation of surface free energy. Performance properties of the coatings were characterized by König hardness, scratch resistance, impact resistance, and gloss measurements.

Understanding Film Thickness‐Dependent Block Copolymer Self‐Assembly by Controlled Polymer Dewetting on Prepatterned Surfaces

AbstractBlock copolymer (BCP) lithography is a versatile bottom‐up approach for the creation of regular nanoscale patterns on large surface areas. The pattern morphology evolving during the microphase separation of a BCP is strongly dependent on the polymer film thickness. Thus, surface wetting as well as interfacial energies between polymer and substrate determine the polymer behavior, however, the complex interplay of those effects is not yet fully understood. In this work, a model describing the film thickness dependence of BCP self‐assembly on prepatterned surfaces is proposed. Polymer dewetting on nanohole‐patterned surfaces is controlled using different prepattern dimensions, polymer amounts, and microphase‐separation temperatures. This is found to allow for a precise local film thickness modulation and thus allows to guide BCP self‐assembly into arrays of tailored hierarchical nanoarchitectures. Analytical calculations of the total surface free energies of the microphase‐separated polymer of different film thicknesses confined inside nanoholes confirm the model. The insights contribute to the understanding of fundamental processes in polymer dewetting and BCP self‐assembly and allow for the controlled creation of advanced hierarchical nanostructures on large areas for applications in optics, plasmonics, and biomedical devices.

Surface modification of reduced graphene oxide‐polyaniline nanotubes nanocomposites for improved supercapacitor electrodes

AbstractIn the present work, irradiation with high energetic ions has been used for surface, structural, and morphological modifications of reduced graphene oxide (RGO) and polyaniline nanotubes (PAniNTs) nanocomposites with a view to enhance their electrochemical performance as supercapacitor electrode. High‐resolution transmission electron microscope micrographs depict defect induced fragmented morphology with stable inner hollow tubes up to a fluence of 2.2 × 1012 ions cm−2, above which drastic degradation of PAniNTs is observed. Irradiation induced annealing effects and structural disorder at varied irradiation fluences have been investigated by micro‐Raman spectroscopy. Formation of shorter PAniNTs of higher surface area due to generation of ion irradiation induced defects and their reorganization results in increased Brunauer‐Emmett‐Teller specific surface area and porosity. Surface energy and wettability of the electrodes increase upon ion irradiation, which improves electrode‐electrolyte interaction at the interface. Surface free energy calculations indicate increased concentration of polar groups on the nanocomposite electrode surface upon irradiation. Electrochemical performance studies indicate enhancement in specific capacitance and cyclic stability from 448 F g−1 and 89% for unirradiated nanocomposite to 482 F g−1 and 92%,, respectively, for the nanocomposite irradiated at 2.2 × 1012 ions cm−2 fluence, which is attributed to the increased surface energy and porosity upon irradiation giving rise to increased electrochemically active sites for charge storage in the electrode.

Langmuir-Blodgett films of membrane lipid in the presence of hybrid silsesquioxane, a promising component of biomaterials.

Functionalized polyhedral oligomeric silsesquioxanes (POSS) derivatives have great potential in biomedical applications such as tissue engineering, drug delivery, biosensors, dental composites and biomedical devices. Having the above in mind, in this paper, the study of the surface characteristics of binary Langmuir-Blodgett films consisting of an open cage silsesquioxane POSS-poly (ethylene glycol) (POSS-PEG) and 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine (DMPE), as a representative of phospholipid was conducted based on contact angle measurements of three liquids. The measured values of the contact angle (with water, formamide and diiodomethane as the wetting liquids) allowed to calculate surface free energy of the films from van Oss et al. approach. The film structure of the deposited layers was evaluated using an atomic force microscope. Analysis of the obtained results led to the conclusion, that the pure DMPE molecules create agglomerates onto a solid substrate, whereas the POSS-PEG molecules form a homogenous monolayer. After an addition of POSS-PEG to lipid film, changes in the surface properties are visible. The wettability as well as surface free energy depend on the molar ratio of both components. The AFM images shed more light on the changes of the DMPE monolayer topography caused by the POSS-PEG addition.

Quantum Mechanical Prediction of Wettability of Multiphase Fluids–Solid Systems at Elevated Temperature

Physiochemical insights into solid–liquid interfaces are essential for characterizing surface wettability and multiphase fluid behaviors in diverse applications. We propose a first-principles approach to predict the polar and thermal effects on wetting properties of crystalline surfaces for a variety of polar or nonpolar liquids. By directly applying the approach to multiphase systems, we simultaneously predict the macroscopic contact angles, the work of adhesion at the solid–liquid interface, and the interfacial tension at the liquid–liquid interfaces. A unique feature of our approach lies in its capability of quantifying the electrostatic interaction at the interfaces of polar liquids and solid surface. Our results reveal a linear relation between the adsorption energy and the electrostatic interaction at the solid–polar liquid interface, which provides a more effective prediction than classical surface free energy calculations. By using quantum molecular dynamics simulation, we predict the variation of...

Novel Synthesis of Choline-Based Amino Acid Ionic Liquids and Their Applications for Separating Asphalt from Carbonate Rocks

In this study, a series of choline-based amino acid ionic liquids have been synthesized in an economic method and are used to assist solvents with extracting asphalt from carbonate rocks. All of the ionic liquids perform well in extracting asphalt, especially choline histidine, by which the single-step recovery of asphalt is up to 91%. Furthermore, oil product with higher quality (fewer solids entrained) is also obtained. Molecular dynamics simulation and thermodynamic equilibrium method are applied to investigate the role of amino acid ionic liquids via interaction energy calculation and surface free energy calculations. The simulation results suggest that the ionic liquid phase is beneficial for the transfer of oil fraction from the carbonate surface to the organic solvent phase. Moreover, the results of simulated calculation show that the introduction of a functional group with conjugated structures into ionic liquid, such as an imidazole ring and a benzene ring, is beneficial for enhancing oil recovery, which are in accordance with the results of experimental tests.

The influence of UV-radiation on hyaluronic acid and its blends with addition of collagen and chitosan

In this paper, the results regarding the influence of UV-irradiation with 254 nm wavelength on the surface and mechanical properties of hyaluronic acid, hyaluronic acid/collagen and hyaluronic acid/collagen/chitosan mixtures are presented. For this study, thin films were prepared by solvent evaporation from solution of HA and mixtures made from HA/Coll and HA/Coll with 30% addition of chitosan. The surface properties of films were investigated by AFM and using contact angle measurements, allowing the calculation of surface free energy and its components. Mechanical properties of films made of biopolymeric blends before and after UV-irradiation have been investigated by mechanical testing machine.

TiO2-Modified Zirconia Surface Improves Epithelial Cell Attachment.

Good cell adhesion is an important prerequisite for soft tissue attachment on implant abutment or crown surfaces. The aim of this study was to evaluate the adhesion and proliferation of human epithelial cells on sol-gel-derived TiO2-coated and noncoated zirconia. Altogether, 56 zirconia disks (Z-CAD, Metoxit) were fabricated for this study. Half of the disks were coated with a sol-gel-derived TiO2 coating (MetAlive, ID Creations). The rest of the disks were noncoated and formed the control group. Surface properties of the disks were characterized by contact angle measurements and surface free energy (SFE) calculation. The cell adhesion was tested by cultivating epithelial cells (20,000 cells/cm2) on the experimental disks for 1, 3, 6, and 24 hours, after which the fluorescence of the samples was measured (BioTek synergy HT). The amount of cells was detected by comparing the fluorescence value to the standard curve. In addition, the proliferation was studied by growing epithelial cells (25,000 cells/cm2) for 1, 3, and 7 days. The number of cells was calculated by defining the absorbance of the samples (Multiskan EX, Thermo Labsystems), followed by a comparison with the standard curve. Finally, the samples were processed for light microscopy. TiO2-coated disks were significantly more hydrophilic with higher total SFE than noncoated disks (P < .05). The amount of epithelial cells was greater on TiO2-coated disks than on controls after 24 hours (P < .05). Regarding cell proliferation, the difference was statistically significant (P < .05) on days 3 and 7. Light microscope evaluation confirmed viable cells, which were in immediate close contact with both substrate surfaces. The cell layers on the coated disks appeared to be more uniform and cell rich than the layers on noncoated disks. This study indicated that TiO2 coating improves epithelial cell attachment and proliferation on zirconia surfaces. This has good potential to enhance formation of the epithelial junction to the coated zirconia surfaces.

Evaluation of protein adsorption to diamond-like carbon (DLC) and fluorinedoped DLC films using the quartz crystal microbalance method.

The aim of the present study was to evaluate albumin adsorption to stainless steel (SUS), diamond-like carbon (DLC) and fluorinedoped DLC (F-DLC) films using the quartz crystal microbalance (QCM) method. Each sensor was characterized using atomic force microscopy, surface roughness and surface wettability measurements and surface free energy calculations. Adsorbed amounts of bovine serum albumin on DLC and F-DLC were significantly lower than that on SUS (p<0.05). The apparent first-order reaction rate, kobs, of F-DLC was significantly larger than those of SUS and DLC (p<0.05). Moreover, significantly lower total surface free energies of DLC and F-DLC influenced the albumin absorbed amounts and kobs. Furthermore, a clear correlation was found between the albumin absorbed amounts and the hydrogen bond component of the total surface free energy. Thus, DLC or F-DLC coating is effective for preventing protein adsorption on orthodontic appliances.

Improvement of surface photostability of bamboo scrimber by application of organic UV absorber coatings

Improving the durability of biological materials is essential for expanding their application areas. In this study, an organic ultraviolet (UV) shielding layer (coating) composed of a UV-curable paint, ethyl acetate, anhydrous alcohol, and an organic UV absorber is constructed on the surface of outdoor bamboo scrimber (OBS). The behaviour of OBS with or without this coating was investigated under accelerated weathering. The physical properties photostability of the samples before and during exposure were evaluated by characterizing the colour and glossiness. Contact angle (CA) measurements and surface free energy (SFE) calculations were performed to investigate the wettability of the coatings. Attenuated total reflectance Fourier transform infrared spectroscopy was used to characterize the changes in the functional groups of the coatings during weathering. The experimental results have shown that the colour, glossiness, CA, SFE, and functional groups photostability of the sample with the UV shielding coating increased significantly compared to those of the control sample. The coating with 5% organic UV absorber was considered as the best UV shielding layer in this study, as it successfully protected the OBS and reduced the surface photodegradation of the substrate and the coating itself.

Mechanism analysis of DTAB on the change in surface wettability of low-rank coal and its relationship to flotability

ABSTRACT The mechanism of dodecyltrimethyl bromide (DTAB) on the change in surface wettability of low-rank coal and its relationship to flotability were investigated in this study. Experimental tests of contact angle, water re-adsorption, fourier transform infrared spectroscopy, van Oss-Chaudhury-Good theory, induction time, and flotation were conducted to analyze the surface hydrophilicity/hydrophobicity, group composition, free energy composition, and flotability. The results indicated that the adsorption capacity of water on low-rank coal first increased and then decreased with increasing DTAB concentration. DTAB can significantly improve the surface hydrophobicity because the oxygen-containing sites on the coal surface were covered by the DTAB head group. The calculation of surface free energy predicted the trends in the change of water-adsorbing ability. Furthermore, the calculation of interfacial interaction free energy proved that the appropriate DTAB concentration is indeed beneficial to prevent the water adsorption. With respect to flotability, it is shown that the addition of DTAB enhanced the flotation yield when DTAB concentration is less than 1.75 mM. The change in flotation yield is closely related to induction time. A lower induction time indicates stronger interaction between the coal particles and bubbles, and will result in high flotation yield.

Preparation and characteristics of antibacterial chitosan films modified with N-halamine for biomedical application.

Several hydantoin derivatives and their N-halamine analogues were examined by spectroscopic methods (IR, 1H-NMR, 13C-NMR), elemental analysis (content of C, H, N), thermogravimetry (TGA), antibacterial tests and experiments of stability in aqueous solution. This research allowed the structural, thermal and antibacterial characteristics of obtained compounds. It was found, the thermal stability of hydantoins depends on their chemical structure and decreases when N-halamine moieties were introduced. In next step, synthesized biocides were added to the chitosan films. The antibacterial properties of received films were proved. It was found that after modification, the thermal stability of CS films decreases in most cases. The surface properties of obtained chitosan films before and after UV irradiation were investigated by means of contact angle measurements allowing the calculation of surface free energy. The chemical and structural changes during UV irradiation were studied by FTIR spectroscopy and SEM microscopy. The results indicated that the introduction of biocides to the CS material contribute to the photooxidation process. The degradation mechanism of obtained materials was proposed. The materials studied in this work may be used in various biomedical applications due to their confirmed biological activity.