Characterization of Glass Beads Surface Modified with Ionic Surfactants

Knowledge of the wetting characteristic of mineral surfaces is very important in enhancing the efficiency of separation of valuable minerals from gangue using froth flotation or oil agglomeration. In this paper a capillary rise technique was used to characterize the glass beads surface modified with cationic surfactant. The glass microspheres were used as model particles with a spherical shape and smooth surface to eliminate the roughness effect. The value of the contact angle for water was found to be 21.5 for unmodified beads, and 61.8, 89.7, 68.4 for 0.1, 1.0, 10 mg/g_solid of CTAB, and 39.8, 68.6, 87.9 for 0.1, 1.0, 10 mg/g_solid of DDAHCl, respectively. Data revealed that the adsorption of surfactant onto glass beads decreased the value of the electron donor component, γ-, which defines the hydrophobicity of the surface. Also, the property of the surface was investigated by flotation and oil agglomeration experiments. It was observed that particles with low value of contact angle for water and high for 1-bromonaphthalene and low value of γ- were floated with a recovery equal to 91.1 and 83.1% for CTAB and DDAHCl, respectively, and effectively agglomerated. This indicates that the capillary rise method can be successfully used to predict the wetting properties of solid particles in mineral processing.     

Surface modification of armos fibers with oxygen plasma treatment for improving interfacial adhesion with poly(phthalazinone ether sulfone ketone) resin

We introduce in this article oxygen plasma treatment as a convenient and effective method for the surface modification of Armos fibers. The effects of oxygen‐plasma‐treatment power on both the Armos fiber surface properties and Armos‐fiber‐reinforced poly(phthalazinone ether sulfone ketone) composite interfacial adhesion were investigated. The Armos fiber surface chemical composition, surface morphology and roughness, and surface wettability as a function of oxygen‐plasma‐treatment power were measured by X‐ray photoelectron spectroscopy, scanning electronic microscopy, atomic force microscopy, and dynamic contact angle analysis. The results show that oxygen plasma treatment introduced a lot of reactive functional groups onto the fiber surface, changed the surface morphology, increased the surface roughness, and enhanced the surface wettability. Additionally, the effect of the oxygen‐plasma‐treatment power on the composite interfacial adhesion was measured by interlaminar shear strength with a short‐beam bending test. Oxygen plasma treatment was an effective method for improving the composite interfacial properties by both chemical bonding and physical effects. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

激光和等离子处理对复合材料表面涂层附着力的影响研究

为了提高环氧涂料在纤维增强聚丙烯复合材料上的附着力,采用激光和等离子体表面前处理方法,应用超景深显微镜、粗糙度测定仪、接触角测试仪以及附着力测试仪,研究了激光和等离子体表面处理对纤维增强聚丙烯复合材料表面形貌、表面粗糙度和表面水接触角的影响,并且探究了这 2种表面处理方式对环氧涂层在复合材料上附着力的影响。结果表明： 2种处理方式均可明显提高环氧涂层在基材上的附着力,附着力均可由不到 1 MPa提高至 8 MPa以上。     

Novel superhydrophobic top coating on surface modified PVC-coated fabric

A superhydrophobic surface was created on poly(vinylchloride)-coated architectural fabric using spray coating method. Dispersions of nanoparticles and a flourochemical were prepared as top coating solutions. After spray-dry-cure process, contact angle, sliding (tilt) angle, 3 M water repellency test and surface morphology were compared between uncoated and top coated PVC surfaces. The results indicated that a specific nano-TiO₂ dispersion top coating produced a superhydrophobic layer on the top of the PVC surface with high contact angle (150°) and very low sliding angle (2°). Combination of two major requirements, the magnified of the degree of roughness and low surface energy, created self-cleaning effect on the PVC surface. Abrasion fastness of superhydrophobic top coating was improved by surface oxidation via UV–ozone surface treatments. Spectroscopic analysis demonstrated that formation of oxygenated functional groups has improved PVC wettability and adhesion. Results of artificial weathering test indicated no change in superhydrophobicity of top coated PVC.     

The influence of pre-bond surface treatment over the reliability of steel epoxy/glass composites bonded joints

A main objective of present research is to consider adhesive bonding as a novel maintenance and repairing damaged section trend for fluid transporting tubes. Nowadays, applying glass fiber reinforced epoxy composite patches (GFRECPs) is considered as an alternative rapid and affordable repair system instead of traditional techniques such as removing strained sections. The main problem with repairing metal pipes using GFRECPs is low strength of adhesion between GFRECPs and a steel substrate. To make adhesion strong enough, it is necessary to excite the intrinsic adhesion forces such as dipoles across the interface which consequently increases a bonding strength due to Van der Waals forces; but secondary forces activation depends on surface regulation levels. In fact, providing a surface with a suitable roughness and increased pureness without any polluters is a key parameter achieving a highly resistant GFRECPs-steel adhesion. To do so, samples were prepared using the SiC paper up to 100, 220, 500 and polished to investigate the effect of different roughness levels in the range of 90.77±1.81 to 2.97±0.05 nm. The surfaces, interface features and bonding strength were characterized applying the atomic force microscope (AFM), water contact angle measurements, FE-SEM, single lap shear (SLS) and T-peel (90°) tests. The results revealed that the highest adhesion strength could be achieved at the polished substrate.     

Gold nanoparticles deposited on glass: physicochemical characterization and cytocompatibility

Properties of gold films sputtered under different conditions onto borosilicate glass substrate were studied. Mean thickness of sputtered gold film was measured by gravimetry, and film contact angle was determined by goniometry. Surface morphology was examined by atomic force microscopy, and electrical sheet resistance was determined by two-point technique. The samples were seeded with rat vascular smooth muscle cells, and their adhesion and proliferation were studied. Gold depositions lead to dramatical changes in the surface morphology and roughness in comparison to pristine substrate. For sputtered gold structures, the rapid decline of the sheet resistance appears on structures deposited for the times above 100 s. The thickness of deposited gold nanoparticles/layer is an increasing function of sputtering time and current. AFM images prove the creation of separated gold islands in the initial deposition phase and a continuous gold coverage for longer deposition times. Gold deposition has a positive effect on the proliferation of vascular smooth muscle cells. Largest number of cells was observed on sample sputtered with gold for 20 s and at the discharge current of 40 mA. This sample exhibits lowest contact angle, low relative roughness, and only mild increase of electrical conductivity.     

WETTABILITY AND SURFACE ENERGETICS OF ROUGH FLUOROPOLYMER SURFACES

Hydrophobic solid surfaces with controlled roughness were prepared by coating glass slides with an amorphous fluoropolymer (Teflon® AF1600, DuPont) containing varying amounts of silica spheres (diameter 48?μm). Quasi-static advancing, θ_A, and receding, θ_R, contact angles were measured with the Wilhelmy technique. The contact angle hysteresis was significant but could be eliminated by subjecting the system to acoustic vibrations. Surface roughness affects all contact angles, but only the vibrated ones, θ_V, agree with the Wenzel equation. The contact angle obtained by averaging the cosines of θ_A and θ_R is a good approximation for θ_V, provided that roughness is not too large or the angles too small. Zisman's approach was employed to obtain the critical surface tension of wetting (CST) of the solid surfaces. The CST increases with roughness in accordance with Wenzel equation. Advancing, receding, and vibrated angles yield different results. The θ_A is known to be characteristic of the main hydrophobic component (the fluoropolymer). The θ_V is a better representation of the average wettability of the surface (including the presence of defects).     

Effects of wood-surface roughness,adhesive viscosity and processing pressure on adhesion strength of protein adhesive

The objective of this research was to study the effects of wood-surface roughness, adhesive viscosity and processing pressure on adhesion strength between soybean protein adhesive and wood, and to seek the relative importance of the individual factors in determining adhesion strength. Processing pressure was found to be the most important factor in determining adhesion strength. An optimum pressure, which was about 4.55 MPa in this research, is needed for development of a strong bond. A higher pressure resulted in reduced adhesion strength, possibly due to damage to the wood surface; a lower pressure also resulted in decreased adhesion strength because of the lack of bond formation. Adhesive viscosity had greater effect on adhesion strength than surface roughness. Contact angle, which was found to be mainly determined by adhesive viscosity and surface roughness, was a major factor controlling adhesive penetration. A smaller contact angle, resulting from lower viscosity and rougher surface, produced deeper penetration, while a larger contact angle, resulting from higher viscosity and smoother surface, produced shallower penetration. An optimum penetration is needed to enhance adhesion strength by developing a three-dimensional interactive zone at the interface. Too deep or too much penetration would result in 'dry-out' at the interface; less penetration would limit the formation of the three-dimensional zone at the interface. Both cases resulted in reduced adhesion strength. Contact angles ranging from 35 to 47° provided the optimum penetration needed for good adhesion. The results of this research could be used as reference to determine optimum process parameters in plywood manufacturing when an aqueous based adhesive is used.     

Particulate reinforcement of polyacrylate elastomers. II. Mechanical properties

This paper presents and discusses results which have been obtained for the mechanical properties of crosslinked polyethylacrylates containing various amounts of microscopic glass beads. The adhesion between the glass beads and the elastomer matrix was varied by subjecting the beads to different surface treatments. That the adhesion is affected by surface treatment has been demonstrated in two ways: (i) Unfilled elastomer sheets have been cast in contact with glasses surfaces which had been treated with the same reagents as were used to treat the beads. The force required to peel the elastomer from the glass was then measured and found to depend strongly upon the surface treatment, (ii) Scanning electron micrographs of the ruptured surfaces of used tensile test-pieces cut from filled elastomer sheets confirm that surface treatment has a profound effect upon the adhesion between bead and matrix. Results are presented for the hardness and tensile stress-strain properties of elastomers containing various amounts of beads. In all cases, the stiffening effect of the beads increases as the adhesion between beads and matrix is improved. Beads which had been treated in such a way as to minimise the, adhesion to the matrix were found to cause an apparent softening of the material as revealed by the tensile stress-strain curve. It has been shown that this effect can be satisfactorily explained if it is assumed that in this case the beads merely serve to increase the void content of the material.     

Effect of roughness as determined by atomic force microscopy on the wetting properties of PTFE thin films

The influence of film roughness on the wetting properties of vacuum-deposited polytetrafluorethylene (PTFE) thin films has been investigated using atomic force microscopy (AFM) and contact angle goniometry. Surface roughness has been characterized by atomic force microscopy in terms of RMS roughness (R_q) and fractal dimensions. A contact angle correlation with surface roughness, as determined by AFM, is evident from these results, which are discussed on the basis of wetting theory. The results also confirm that the high water contact angles (as high as 150°) recently observed at the surface of a new water repulsive coating material (mixture of PTFE and binder) are because of surface roughness. Such measurements clarify the effect of nanometer-size surface asperities on the wetting properties of hydrophobic coating.     

化工设备材料表面及其对界面黏附强度的影响

设备材料的表面粗糙程度对污垢颗粒界面黏附力的影响较大。本文以设备材料粗糙表面为研究对象,考察了传统指标和分形指标的尺度独立性,发现分形指标随尺度的变化分为不稳定分形区和稳定分形区。通过对二维表面轮廓线的分析,将区域分隔临界点的求取转化为取样长度和夹角α值的定量关系求解,通过实验得出其定量关系,找出稳定分形区。采用原子力显微镜测颗粒在不同粗糙表面的黏附力,结合固体污垢清除机理分析,发现表面的粗糙程度对界面黏附力的影响较大。研究表明Ra<0.4627μm时,随着表面粗糙度增加,黏附力减小;1.3461μm< Ra <2.9755μm时,黏附力逐渐增大;Ra>3μm时,黏附力保持稳定。黏附力随着分形指标的变化而变化,其变化趋势与传统指标正好相反。随着分形维数的增大,黏附力先是保持稳定,后逐渐增大,随着加工工艺的改变,表面粗糙程度有个剧烈的变化,分维值锐减,后逐渐增大。     

Study on the pretreatment method of glass-epoxy resin in the presence of TiO2 sol prepared by hydrothermal method

In the present study, the pretreatment of glass-epoxy resin using photoreaction of TiO₂ sol prepared by hydrothermal method was investigated. The surface properties for the pretreated substrate were examined, and the change of contact angle was measured to confirm the hydrophile property caused by the photocatalytic reaction. After the pretreatment, the surface was oxidized with showing no changes in its morphology. However, the surface roughness at nano-scale order increased with the photocatalytic reaction time. When UV light was irradiated for 60 min in TiO₂ sol, the adhesion strength of electroless-plated Cu film was most excellent in other test conditions.     

A simple approach to fabricate sticky superhydrophobic polystyrene surfaces

We present a facile method for the fabrication of a sticky superhydrophobic polystyrene surface using ethanol as the non-solvent. The obtained surface shows the hierarchical textured morphology as well as the multiple scales of roughness and large numbers of microspheres. Without any chemical modification, the prepared polystyrene surface exhibits sticky superhydrophobicity with a high equilibrium contact angle of 153°. Interestingly, a water droplet on the surface cannot move at any tilt angle even when the substrate is turned upside down. The mechanism of the fabricated surface with high adhesion is discussed in detail. Moreover, the obtained polystyrene surface exhibits the strong adhesion to the liquid droplets of pH value from 1 to 14.     

Surfactant-catalyzed SiO2 thin films preparation and characterization

SiO₂ thin films are in high demand for wide range of applications including microelectronics, optoelectronics, solar energy conversion, photocatalysis, and self-cleaning coatings. The performance of thin film is strongly influenced by surface properties like surface roughness, thickness, morphology, wetting behavior, and thermal stability. In these applications, the SiO₂ sols were prepared using tetraethylorthosilicate as a source of SiO₂ and deposited on 100?×?40?×?2?mm³ glass slide using dip-coating method for 2?min and calcined at 250?°C for 30?min. The SiO₂ thin films were obtained using DTAB, SDS, and Tween 20 (Tw 20) surfactants with the thickness of 36.92, 47.15, and 52.39?nm, respectively. Surface morphology was studied with AFM and surface roughness was depicted with 0.9528, 3.6534, and 0.9294?nm. Contact angle measurements have been performed with goniometer to evaluate the wetting behavior of the film. The contact angle of 58.01°, 48.40°, and 37.88° was observed with SDS, DTAB, and Tw 20 film, respectively. The SiO₂ thin films with SDS showed more surface roughness and water repelling ability when compared to DTAB and least with Tw 20.     

Design factors for reducing ice adhesion

The purpose of this study was to investigate the relationships between a type of engineering material and the ice adhesion strength while in direct application in icing conditions. Ice adhesion tests were conducted on various materials with different surface conditions. There is an identified need for systematic studies on the effects of varying surface conditions with well-characterized roughness and accurate adhesion measurement. This information is key in understanding the adhering behaviour of ice which is a necessary prerequisite for modelling the behaviour of ice adhesion to other surfaces and for icing prevention. Results show that the type of material will determine, in large, the strength of the ice adhesion between surfaces with similar roughness characteristics and the receding contact angle of water can be used as a predictor of relative ice adhesion. The adhesive strength of ice can be increased or decreased dramatically by means of adjusting the surface roughness with a uniform process. Each material tested exhibits a similar linear relationship. There was a stark contrast in the ice adhesion between the varying materials despite very similar polished surface conditions and static water contact angles. Ice bonded to the glass surface with an adhesion of 1562 ± 113 kPa, and to aluminum at 1039 ± 117 kPa, and stainless steel at 1022 ± 115 kPa, and finally Teflon at only 33 ± 52 kPa and during 80% of trials the ice/substrate interface was broken with no measured adhesion. The information gathered can be used to improve designs for a number of devices needed in cold weather climates.     

Self-cleaning performance of sol–gel-derived TiO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript> double-layer thin films

The self-cleaning properties of the TiO₂/SiO₂ double-layer films prepared by sol–gel method were investigated. Thin films were prepared by spin coating onto glass and then thermally treated at different temperatures, and characterized using X-ray diffraction, atomic force microscopy, field emission scanning electron microscopy, and UV–visible spectroscopy. The cross-sectional structure of the films was observed by FESEM. The surface roughness of the films was characterized by AFM. The root mean square surface roughness of the thin films was below 2 nm, which should enhance their optical transparency. The photo-induced hydrophilicity of the films was evaluated by water contact angle measurement in air. The photocatalytic activity of the films was studied by the photocatalytic degradation of methylene blue under UV light irradiations. The TiO₂/SiO₂ double-layer thin films are plausibly applicable to developing self-cleaning materials in various applications such as windows, solar panels, cement, and paints.     

Adhesion of solid particles to gas bubbles. Part 2: Experimental

In slurry bubble columns, the adhesion of solid catalyst particles to bubbles may significantly affect the G-L mass transfer and bubble size distribution. This feature may be exploited in design by modifying the hydrophilic or hydrophobic nature of the particles used. Previously we have proposed a generalised model, describing the adhesion of particles to G-L interface under stagnant conditions. In this work, we studied the adhesion of particles characterised by different degree of hydrophobicity and porosity: non-porous polystyrene and glass beads, unmodified and hydrophobised mesoporous silica, and activated carbon particles. Images recorded at high optical magnification show the particles adhering to gas bubbles individually or as aggregates. In aqueous media, higher liquid surface tension and particle surface hydrophobicity increase the adhesion strength and the tendency of particles to agglomerate, in agreement with the model. The adhesion of non-porous rough-surface particles to gas bubbles can be characterised by the receding contact angle. The advancing contact angle represents better the adhesion of the same particles to liquid droplets. We found that the “effective” contact angle of porous particles is much lower than an “intrinsic” contact angle calculated from the heat of immersion in water, or measured by sessile drop method. An equivalent contact angle derived from the Cassie rule explains the wetting behaviour of particles having the pores filled with liquid.     

Fabrication of superhydrophobic transparent cyclic olefin copolymer (COC)-SiO2 nanocomposite surfaces

A superhydrophobic cyclic olefin copolymer (COC) nanocomposite coating was produced with a very simple and easy method. Self-cleaning superhydrophobic COC surfaces were obtained by only adding surface hydrophobized SiO₂ nanoparticles by dip coating method. The influence of concentration of SiO₂ and the coating temperatures on the wettability of the surfaces were investigated. The surface wettability of the coatings was examined with the contact angle measurements and the surface roughness and morphology were analyzed by using atomic force microscope and scanning electron microscopy analysis. Surfaces with certain amounts of COC and SiO₂ showed superhydrophobic character with high water contact angle of 169⁰. Also, the obtained superhydrophobic surfaces show superior water repellent, high transparency, and self-cleaning characteristics.     

Superhydrophobic surface decorated with vertical ZnO nanorods modified by stearic acid

Static and dynamic wettability of the ZnO nanorod surface prepared by a facile and inexpensive route is reported. The wettability of the ZnO surface was controlled and tuned by post hydrophobization using different stearic acid concentrations. The surface of the ZnO nanorods modified with 8 mM stearic acid showed a static water contact angle of 152° and sliding angle of 9°, which indicates superhydrophobicity. This suggests that the combination of the rough structures achieved by the ZnO nanorods and low surface energy provided by stearic acid modification results in superhydrophobicity and a very low sliding angle. The crystal structure, surface chemical elements, surface morphology, surface roughness, and static and dynamic water contact angles of the ZnO coatings were studied in detail. Further, the surface properties were assessed by calculating the surface free energies and work of adhesion for unmodified and stearic-acid-modified ZnO nanostructure surfaces. These coatings can find potential industrial applications in the electronic industry.     

Adhesion Reduction of Diamond-Like Carbon Films Based on Different Contact Geometries by Using an AFM

The effect of reducing adhesion force by coating with a metal-containing diamond-like carbon (DLC) film has been studied by recording force–displacement curves with an atomic force microscope. A flat tip, a spherical tip, and some sharp tips were applied to mimic the different contact geometries. The results show that both under ambient conditions and in dry nitrogen, the DLC film can effectively reduce the adhesion force for different contact geometries. The reduction of the adhesion force was attributed to the decrease of the surface free energy and the increase of the contact angle for water. The reduction ratio of adhesion is closely related to contact geometry, the roughness of DLC film, material characteristics paired with DLC film and the environment. These factors are mutually coupled to determine the final reduction ratio. Under both conditions, the DLC film also plays a role in reducing the wear and tear when measuring the adhesion forces.