Reduction Of Surface Energy Research Articles

Superhydrophobic Paper from Nanostructured Fluorinated Cellulose Esters.

The development of economically and ecologically viable strategies for superhydrophobization offers a vast variety of interesting applications in self-cleaning surfaces. Examples include packaging materials, textiles, outdoor clothing, and microfluidic devices. In this work, we produced superhydrophobic paper by spin-coating a dispersion of nanostructured fluorinated cellulose esters. Modification of cellulose nanocrystals was accomplished using 2H,2H,3H,3H-perfluorononanoyl chloride and 2H,2H,3H,3H-perfluoroundecanoyl chloride, which are well-known for their ability to reduce surface energy. A stable dispersion of nanospherical fluorinated cellulose ester was obtained by using the nanoprecipitation technique. The hydrophobized fluorinated cellulose esters were characterized by both solid- and liquid-state nuclear magnetic resonance, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and contact angle measurements. Further, we investigated the size, shape, and structure morphology of nanostructured fluorinated cellulose esters by dynamic light scattering, scanning electron microscopy, and X-ray diffraction measurements.

Equilibrium nuclear ensembles taking into account vaporization of hot nuclei in dense stellar matter

We investigate the high-temperature effect on the nuclear matter that consists of mixture of nucleons and all nuclei in the dense and hot stellar environment. The individual nuclei are described within the compressible liquid-drop model that is based on Skyrme interactions for bulk energies and that takes into account modifications of the surface and Coulomb energies at finite temperatures and densities. The free-energy density is minimized with respect to the individual equilibrium densities of all heavy nuclei and the nuclear composition. We find that their optimized equilibrium densities become smaller and smaller at high temperatures because of the increase of thermal contributions to bulk free energies and the reduction of surface energies. The neutron-rich nuclei become unstable and disappear one after another at some temperatures. The calculations are performed for two sets of model parameters leading to different values of the slope parameter in the nuclear symmetry energy. It is found that the larger slope parameter reduces the equilibrium densities and the melting temperatures. We also compare the new model with some other approaches and find that the mass fractions of heavy nuclei in the previous calculations that omit vaporization are underestimated at $T \lesssim 10$MeV and overestimated at $T\gtrsim10$~MeV. The further sophistication of calculations of nuclear vaporization and of light clusters would be required to construct the equation of state for explosive astrophysical phenomena.

One-step hydrothermal method to fabricate drag reduction superhydrophobic surface on aluminum foil

Superhydrophobic surface, covered by micro or nano textured layer, can trap and retain air pockets and possesses unique excellent properties. Here we propose a novel one-step hydrothermal method to fabricate superhydrophobic surface on aluminum foil. The film of sheet structure is Al[CF3(CF2)12COO]3, which can provide micro structures and reduce surface energy. The as-prepared surface with high contact angle and low sliding angle has some interesting characteristics. In the test, the powder dirt can be easily removed from the surface and the formation of ice is inhibited on it. The drag reduction ratio of the superhydrophobic surface is about 20–30% at the velocity of 2–5 m/s. We envision this superhydrophobic surface has a great prospect in industrial applications.

Morphological evolution of Ge/Si nano-strips driven by Rayleigh-like instability

We present the morphological evolution obtained during the annealing of Ge strips grown on Si ridges as a prototypical process for 3D device architectures and nanophotonic applications. In particular, the morphological transition occurring from Ge/Si nanostrips to nanoislands is illustrated. The combined effect of performing annealing at different temperatures and varying the lateral size of the Si ridge underlying the Ge strips is addressed by means of a synergistic experimental and theoretical analysis. Indeed, three-dimensional phase-field simulations of surface diffusion, including the contributions of both surface and elastic energy, are exploited to understand the outcomes of annealing experiments. The breakup of Ge/Si strips, due to the activation of surface diffusion at high temperature, is found to be mainly driven by surface-energy reduction, thus pointing to a Rayleigh-like instability. The residual strain is found to play a minor role, only inducing local effects at the borders of the islands and an enhancement of the instability.

Study on effects of surface roughness on reduction of surface energy

Study on effects of surface roughness on reduction of surface energy

Study on effects of surface roughness on surface energy reduction

Study on effects of surface roughness on surface energy reduction

Atmosphere Has No Energy as It is Balanced Between Gravity and Full Vacuum Universe: A Mini Review

It should be agreed that all objects like planets, stars etc. float in the full vacuum universe. It should also be agreed that atmosphere possessed by these objects is due to gravity and the atmosphere is in the open system full vacuum universe. Here, air molecules always try to escape in full vacuum universe against gravity to have uniformity in the universe. Means it is balanced between gravity and full vacuum universe. It is in science textbooks that the Earth’s atmosphere exerts pressure. But, to have pressure in the system, it must be isolated by boundary and its value is same at any point within. Here, Earth’s atmospheric air neither uniformly distributed nor in a closed system. It is known that gravity is holding each air molecule towards the Earth. On surface, air has high-density molecules and as further go away molecules density decreases. This density difference is balanced between gravity and full vacuum universe. This paper uncovers the misconception regarding Earth’s atmosphere exerts pressure due to its air molecules vertical column mass. To prove the argument, the manometer experiment is visited. In this experiment author makes the effort to raise mercury filled tube up against gravity above pot level then inverts it. Here, mercury level drops because of gravity which creates a vacuum in the top of the tube. This causes reduced surface energy inside wall of the tube. To be in the equilibrium state with outer tube wall, inner wall surface tries to suck in all direction that holds mercury up against gravity that means tube mercury weight is balanced by vacuum and that is demonstrated.

Noble-Metal-Free Co0.6Fe2.4O4 Nanocubes Self-Assembly Monolayer for Highly Sensitive Electrochemical Detection of As(III) Based on Surface Defects

Nanocrystals generally suffer from agglomeration because of the spontaneous reduction of the system surface energy, resulting in blocking the active sites from reacting with target ions, and then severely reducing the electrochemical sensitivity. In this article, a highly ordered self-assembled monolayer array is successfully constructed using ∼14 nm Co0.6Fe2.4O4 nanocubes uniformly and controllably distributed on the surface of a working electrode (glass carbon plate). The large area and high exposure of the surface defects on Co0.6Fe2.4O4 nanocubes are clearly characterized by high-resolution transmission electron microscopy (HRTEM) and atomic-resolution high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). Expectedly, a considerable sensitivity of 2.12 μA ppb-1 and a low limit of detection of 0.093 ppb are achieved for As(III) detection on this highly homogeneous sensing interface; this excellent electroanalysis performance is even better than that of noble metals electrodes. Most importantly, this approach of uniformly distributing the small-sized defective nanoparticles on the electrode surface provides a new opportunity for modifying the electrodes, as well as the realization of their applications in the field of environmental electroanalysis for heavy metal ions.

Facile fabrication of uniform hierarchical structured (UHS) nanocomposite surface with high water repellency and self-cleaning properties

In the present study, two-stage process for the fabrication of superhydrophobic Ni-Cu-TiO2 nanocomposite coatings on the copper substrate has been introduced. Surface modification was performed on the electrodeposited coatings by myristic acid-ethanol solution to achieve superhydrophobicity. Additionally, in order to further study the roughness effect, instead of addition of copper ions in electrodeposition bath, three substrates were roughened by electrochemical etching method. Water repellency properties were studied through measurement of static and dynamic contact angles, and performing bouncing test, self-cleaning and water-jet evaluation. The samples were electrodeposited in various current densities, and the highest corrosion resistance and water repellency properties were obtained for the sample which was electrodeposited in two consecutive steps and modified by a fatty acid called myristic acid (which significantly reduces surface energy of the coating). The highest water contact angle (161°) and the lowest contact angle hysteresis (3°) were obtained for the sample which was coated by 10 mA/cm2 (144 min) and 20 mA/cm2 (18 min), respectively. Since this approach does not require any sophisticated equipment and materials, it shows promising future in the fabrication of superhydrophobic coatings.

The impact of saturation on seismic dispersion in shales — Laboratory measurements

Previous studies found a significant increase of acoustic velocities between seismic and ultrasonic frequencies (seismic dispersion) for shales, which would have to be taken into account when comparing seismic or sonic field data with ultrasonic measurements in the laboratory. We have executed a series of experiments performed with a partially saturated Mancos shale and a Pierre shale I in which the influence of water saturation on acoustic velocities and seismic dispersion was investigated. The experiments were carried out in a triaxial setup allowing for combined measurements of quasistatic rock deformation, ultrasonic velocities, and dynamic elastic stiffness at seismic frequencies under deviatoric stresses. Prior to testing, the rock samples were preconditioned in desiccators at different relative humidities. For both shale types, we present and analyze the experimental results that demonstrate strong saturation and frequency dependence of dynamic Young’s moduli, Poisson’s ratios, and Thomsen’s anisotropy parameters, as well as P- and S-wave velocities at seismic and ultrasonic frequencies. The observed effects can be attributed to water adsorption and capillary pressure that are functions of several factors including water saturation. Water adsorption results in a reduction of surface energy and grain-contact stiffness. The capillary pressure affects the effective stress and possibly also the effective pore-fluid modulus, which may be approximated by Brie’s empirical model. Reasonable fits to the low-frequency seismic data are obtained by accounting for these two effects and applying the anisotropic Gassmann model. The strong increase in dispersion with increasing water saturation is attributed to local flow involving adsorbed (bound) water, but a quantitative description is yet to be provided.

Producing superhydrophobic/oleophobic coatings on Cultural Heritage building materials

Abstract Water is the main vehicle of decay agents in Cultural Heritage building materials exposed to weathering. In this work, a simple method to produce superhydrophobic/oleophobic coatings building materials, including under outdoors conditions, has been developed. In addition, a study of the behavior of the developed coatings on different substrates (limestone, granite, concrete and wood) is reported. The addition of 40 nm-SiO2 nanoparticles to a fluoroalkylsilane reduces surface energy and produces a Cassie-Baxter surface in all the materials evaluated. It promotes high static contact angle values of around 160°, and a contact angle hysteresis of around 3°, giving rise to repellence. The building surfaces also demonstrate an excellent self-cleaning performance. The coatings maintain the building materials esthetics as required in the Cultural Heritage field. Finally, the coating presents a long-lasting performance due to condensation reactions producing effective grafting to the four building materials evaluated.

Nano-Structures Stiction Suppression by Molecular Structure Optimized Surface Energy Reduction Agent

Introduction Ceaseless scaling of semiconductor devices has caused nano-structure stiction issues during drying step of wafer cleaning. The following mechanism is considered to explain nano-structure stiction. Capillary force of remaining liquid in one trench where neighboring trenches are empty causes nano-structure bending, and an adhesive force generated by neighboring nano-structures contact area tends to keep stiction [1][2]. Within the elastic limit, an elastic force overwhelms the adhesive force, so the contacted nano-structures are forced detached again [3][4]. However, if the adhesive force defeats the elastic restoring force, the nano-structures may stay adherent even after drying [5]. To reduce the capillary forces, a low surface tension liquid such as isopropyl alcohol (IPA) has been used rinsing liquid. Furthermore, zero surface tension with super critical fluid (SCF) is beginning to be employed for semiconductor mass production. To suppress the adhesive forces, we have proposed the surface energy reduction process [6]. Moreover, we have already demonstrated this process is more effective for preventing nano-structure stiction than conventional IPA drying. The ideal surface termination is to minimize the number of high energy molecule sites. In case of silicon oxide surfaces, it means to replace highly reactive hydroxyl groups with inactive molecules. In this paper, we will present the proper molecular structure for the surface energy reduction agents and its evaluation method. Experimental Protocol We used two types of silylation agent for the surface energy reduction. The carbon number of straight-chain alkyl group of the agents is 1 and 8, so named as C1 and C8 respectively. We dipped thermally oxidized Si pieces in these agents, and measured the water contact angles. We also estimated the surface free energy from the critical surface tension obtained by Zisman plot. We treated 15nm half pitch SiO2 high aspect ratio line and space patterns with a single wafer cleaning tool, and checked the presence or absence of its pattern stiction with scanning electron microscopy (SEM). Results and Discussion As shown in Fig.1, the water contact angles of thermal SiO2 with C1 and C8 treatment are 85º and 101º. Supposedly, longer straight-chain alkyl groups enables more highly hydrophobic surface. As shown in Figure 2 Zisman plot, critical surface tension of the C8-treated SiO2 surface is 25 mN/m. Whereas the critical surface tension of the C1-treated surface is 22.5 mN/m in spite of its lower water contact angle than that of C8 treated surface. It is supposed that hydrogen bonds influence should be considered in use of a water probe since hydrogen bonds in water generate higher liquid surface tension. As explained by Cassie-Baxter theory, complex surfaces water pinning effect enhances the apparent water contact angle. Namely, in order to suppress nano-structure stiction,we should reduce the surface free energy at the interface between contacting nano-structures [6]. To obtain the surface free energy, we had to eliminate the influence of hydrogen bonds. So, we have focused a nonpolar hydrocarbon probe used for Zisman plot method which is free from hydrogen bonds influence. Eventually, we have obtained the ideal surface free energy of the nano-structure surface. Figure 3 shows the SEM images of the 15nm half pitch line and space samples treated with C1 and C8 respectively. The only C1-treated sample shows no stiction. This result indicates that it is not so important to obtain high water repellency, but is very important to obtain lower surface free energy. Summary We evaluated two types of silylation agent (C1,C8) for suppression of nano-structure stiction. Although C1-treated surface enables lower water contact angle than that of C8, its surface free energy becomes lower. For 15nm half pitch line and space, C8-treatment cannot suppress the line stiction since C8-treatment is insufficient to reduce the surface free energy as C1. We have confirmed that surface free energy reduction is important for the suppression of stiction, and have attained stiction free drying of 15nm half pitch high aspect ratio line & space using C1-treatment.

Process, Physicochemical Characterization and In-Vitro Assessment of Albendazole Microcrystals

Purpose: Albendazole is a poorly soluble drug which limits its oral bioavailability. The study was focussed to enhance the solubility by in-situ micronization.Methods: Albendazole microcrystals were prepared by solvent change method using gum karaya and hupu gum as stabilizing agents and the effect of each stabilizer on the prepared microcrystals were studied. FT-IR, DSC, XRD and SEM analysis were performed as a part of characterization studies. The formulations were evaluated for micromeritics, solubility and drug release. The microcrystals that had shown optimized properties were filled into suitable capsules.Results: The formulations showed reduction in particle size with uniform size distribution and three folds increase in drug release. The microcrystals had shown more than 100-folds increase in solubility compared to pure drug. Surface energy, enthalpy and crystalline nature of microcrystals were found to be reduced. Microcrystals containing gum karaya had shown more drug release. The filled-in capsules also showed increase in drug release rate. The solubility enhancement of albendazole microcrystals was mainly due to the surface adsorption of the stabilizing agents that led to reduction in surface energy and crystalline nature as substantiated by the DSC and XRD studies. The type of stabilizing agent had significant effect on dissolution rate. High affinity of albendazole with gum karaya led to faster drug release profiles.Conclusion: The study proved that in-situ micronization is an effective technique to enhance the solubility and dissolution rate of poorly soluble drugs like albendazole.

Nano-Structures Stiction Suppression by Molecular Structure Optimized Surface Energy Reduction Agent

Scaling of semiconductor devices has caused nano-structure stiction issues during the drying step of wafer cleaning. We have already proposed a surface modification process to reduce the surface energy, and we have demonstrated this process is more effective for preventing nano-structure stiction than conventional IPA (isopropyl alcohol) drying. In this paper, the proper molecular structure is investigated for surface modification agents. It is important for the suppression of stiction to reduce a surface free energy rather than to increase a water contact angle. We have attained stiction free drying of a high aspect ratio pattern with 15 nm half pitch line and space using agents with shorter alkyl groups.

Strain‐Induced Surface Micro/Nanosphere Structure: A New Technique to Design Mechanically Robust Superhydrophobic Surfaces with Rose Petal‐Like Morphology

AbstractA robust surface geometrical structure not only enables a favorable practical application but also leads to a long‐term reliability of superhydrophobic surfaces, and hence it is pivotal to find an effective route to improve the mechanical durability of superhydrophobic surfaces. This study reports a simple magnetron sputtering method to directly construct a robust rose petal‐like copper surface with high water adhesion (petal effect). A stable surface micro/nanosphere topography combining with naturally low surface energy is spontaneously formed by the strain‐induced‐island growth of the copper films during the sputtering process. Further reduced surface energy by fluorosilane, the rose petal‐like surface shows a high water contact angle (≈161.4°), effective adhesion force of ≈154 µN, and no‐loss transportation critical droplet volume of ≈98 µL. In addition, as‐prepared superhydrophobic surfaces exhibit superior mechanical stability according to the thermal shock (−40 °C/90 °C) for ≈500 cycles, water‐impacting test for ≈6 h, and finger touch (≈20 times) as well as tape‐peeling test (≈65 times) without losing superhydrophobicity. This work might provide a novel but simple way to directly and effectively fabricating robust superhydrophobic metallic surfaces for potential industrial applications, and can be easily extended to other metals and alloys.

Effects of iron concentration and redox states on failure of boron-free E-glass fibres under applied stress in different conditions

Hydrolysis resistance of boron-free E-glass fibre with different total iron oxide (\(\hbox {Fe}_{2}\hbox {O}_{3}\)) concentrations, iron redox index and durations of fibre ageing up to 180 days at 50\(^{\circ }\hbox {C}\) with 50% relative humidity (RH) was studied. The effect of ageing on the fibre failure measured in two different test environments was examined by using two-point bending method. Based on the differences in failure strains of the fibres obtained from the two conditions as a function of ageing time, the Griffith theory of solid fracture was applied to estimate glass surface energy difference in ageing conditions. The results showed that stress-assisted hydrolysis, when the fibres were under stress, could lead to about 5.18 times reduction in surface energy to account for 2.30 times reduction in fibre failure strain when tested in 50% RH at room temperature. Our study showed that the boron-free E-glass aged up to 180 days only deteriorated within 13%, independent of total \(\hbox {Fe}_{2}\hbox {O}_{3}\) concentration and \(\hbox {FeO/Fe}_{2}\hbox {O}_{\mathrm{3\,total}}\) ratio, and stress-assisted hydrolysis played a key role during sample testing. Dynamic fatigue of the aged E-glass fibres was also investigated, showing little influence of total \(\hbox {Fe}_{2}\hbox {O}_{3}\) concentration and \(\hbox {FeO/Fe}_{2}\hbox {O}_{\mathrm{3\,total}}\) ratio on fibre stress; corrosion susceptibility was observed.

Modulus- and Surface-Energy-Tunable Thiol-ene for UV Micromolding of Coatings.

Micromolding of UV-curable materials is a patterning method to fabricate microstructured surfaces that is an additive manufacturing process fully compatible with roll-to-roll systems. The development of micromolding for mass production remains a challenge because of the multifaceted demands of UV curable materials and the risk of demolding-related defects, particularly when patterning high-aspect-ratio features. In this research, a robust micromolding approach is demonstrated that integrates thiol-ene polymerization and UV LED curing. The moduli of cured thiol-ene coatings were tuned over 2 orders of magnitude by simply adjusting the acrylate concentration of a coating formulation, the curing completed in all cases within 10 s of LED exposure. Densely packed 50-μm-wide gratings were faithfully replicated in coatings ranging from soft materials to stiff highly cross-linked networks. Further, surface energy was modified with a fluorinated polymer, achieving a surface energy reduction of more than a half at a loading of 1 wt %, and enabling tall (100 μm) defect-free patterns to be attained. The demolding strengths of microstructured coatings were compared using quantitative peel testing, showing its decrease with decreasing surface energy, coating modulus, and grating height. This micromolding process, combining tunability in thermomechanical and surface properties, makes thiol-ene microstructured coatings attractive candidates for roll-to-roll manufacture. As a demonstration of the utility of the process, superhydrophobic surfaces are prepared using the system modified by the fluorinated polymer.

Biomimetic Superhydrophobic Biobased Polyurethane-Coated Fertilizer with Atmosphere "Outerwear".

The development of efficient biobased controlled-release fertilizers has captured much research attention because of the environmental concerns and food scarcity problems. In this work, a biomimetic superhydrophobic biobased polyurethane-coated fertilizer (SBPF) was successfully fabricated by increasing surface roughness and reducing surface energy of polyurethane (PU) coating. The green PU coating was synthesized from low-cost, biodegradable, and renewable cottonseed oil. The nutrient release longevity of SBPF revealed 2-fold enhancement compared with the normal biobased PU-coated fertilizer (BPF). The significant improvement of nutrient release characteristics can be attributed to the atmosphere "outerwear" which ensured the nonwetting contact of water with superhydrophobic surfaces in gas state instead of in liquid state. The new concept introduced in this study can inform the development of the next generation of biobased controlled release fertilizers.

Hydrazine solution processed CuSbSe2: Temperature dependent phase and crystal orientation evolution

CuSbSe2 has attracted huge attention as an absorber material for thin-film solar cells due to its attractive optical and electrical properties, as well as earth-abundant, low-cost, and low-toxic constituent elements. However, different from the conventional inorganic absorbers such as CdTe, CuSbSe2 has a complicated phase space with at least five competitive phases such as Cu2Se, CuSe, Sb2Se3, Cu3SbSe4, and Cu3SbSe3 and crystallizes in two-dimension (2D) layered structure. Crystal phase and orientation strongly correlate with film properties and thus are crucial for device performance. In this paper, by varying the annealing temperature, we carefully investigated the phase, electrical properties and crystal orientation evolutions of hydrazine solution processed CuSbSe2 films. Intermediate Cu3SbSe3 secondary phase was identified, and the temperature dependent orientation change was observed, which is driven by the reduced surface energy, as supported by the first-principle calculations. Finally, a prototype thin film solar cell is fabricated, achieving 2.70% efficiency. Our theoretical calculation and experimental investigation demonstrated the importance of controlling phase composition and crystal orientation in the application for photovoltaics.

The variation of surface free energy of Al during superhydrophobicity processing

Surface free energy (SFE) of solids is a main property. This parameter can be affected by various phenomena such as superhydrophobicity creation. Two circumstances are necessary to achieve superhydrophobicity characteristics. These requirements are roughness improvement as well as surface energy reduction. The ZnO nanoparticle deposition is a suitable method for obtaining desirable roughness and consequently decreased SFE with stearic acid (STA) ethanol solution. The SFE of bare Al at room temperature was investigated using molecular dynamics (MD) simulation. After fabrication of superhydrophobicity property on Al surface, its SFE was calculated by applying equation of state and critical surface tension methods. The comparison between results based on two considered methods led to the fact that SFE significantly reduces after superhydrophobicity processing and reaches to STA, applied as a modifier, surface tension value. In addition to the theoretical results, water contact angle (CA) measurements confirm the SFE reduction due to superhydrophobic processing. Furthermore, the presence of STA on the superhydrophobic surface can be verified experimentally with Fourier transform infrared in conjunction with attenuated total reflection (FTIR-ATR) analysis. Therefore, both computational and experimental results approve the existence of STA on superhydrophobic Al surface and its grafting may lead to SFE reduction.