Colloid Journal最新文献

It has been shown that the wettability of a material synthesized in the interfacial layer of a liquid/liquid heterogeneous system can be controlled by local vibrations. The influence of the nature of an organic acid, a metal, and a solvent on the contact angle of a material adhered to various substrates has been studied. It has been found that, under local vibrations, a material is synthesized with a more ordered structure, a higher roughness, a lower water content, and, as a consequence, a larger contact angle. Hydrophobic coatings with contact angles of 100–163° have been obtained on the studied substrates, with the coatings retaining their water-repellent properties under atmospheric conditions for a long time.

Kinetic dependences have been determined for the surface tension, dilatational dynamic surface elasticity, and ellipsometric angles of solutions of styrene copolymers with 4-vinylbenzyl chloride modified with N,N-dimethyldodecylamine. The micromorphology of the adsorbed and spread layers of these polyelectrolytes has also been studied. All kinetic dependences of the dynamic surface elasticity have turned out to be monotonic in contrast to those observed for previously studied solutions of polyelectrolytes free of polystyrene fragments. The peculiarities of the surface properties of the studied solutions may be related to the formation of microaggregates in the surface layers, because these microaggregates suppress the formation of loops and tails of polymer chains at the interfaces, and, consequently, decrease the surface elasticity after the local maximum. Atomic force microscopy data also indicate the formation of aggregates with sizes in the Z direction of 1–4 nm in the surface layers. The obtained results confirm the conclusions previously made about the formation of aggregates in the surface layers of solutions of polyelectrolytes containing fragments of sodium poly(styrene sulfonate). A 2D phase transition to a denser surface phase and the formation of aggregates with a size of 40 nm in the Z direction have been observed at surface pressures of 25–30 mN/m for the layers of the studied styrene-free polyelectrolyte spread over an aqueous substrate.

Currently, composites based on glass fibers and epoxy resins are successfully used to produce various structural elements. Such structures often serve under extreme conditions of both the Far North and the tropics, with such conditions having a destructive effect on the materials causing degradation of their properties. In this case, water resistance is an important characteristic of the materials. One of the ways to protect such materials is the use of organosilicate coatings (OSCs) obtained on the basis of organosilicon varnishes and highly dispersed hydrosilicates. This article presents the results of laboratory studies and field tests carried out in areas with very cold, as well as tropical savannah and subequatorial climates, of composite and metallic materials protected with OSCs. The objects of the studies are OSCs based on a binder, KO-921 varnish modified with the aim to improve weather resistance, primarily, moisture resistance, with poly(dimethylsiloxane) and epoxy resin. Water absorption, contact angle, and hardness of OSCs have been studied as depending on the composition of the polymer binders, and the optimal concentrations of the precursors have been determined. The results of field tests have shown that the developed OSCs retain their water-repellent properties during long-term exposure in different climatic conditions, thereby confirming their applicability to protecting various materials under the conditions of both tropics and the Far North.

Superhydrophilic copper surfaces with hierarchical textures have exhibited a high efficiency in fighting against nosocomial infections. However, one of the key drawbacks of these surfaces is their high susceptibility to mechanical contamination with fibrous materials in the course of sanitation procedures. This study has proposed a method for a laser modification enhancing the resistance of superhydrophilic copper surfaces to fiber contamination during their sanitary treatment. The modified surfaces retain their superhydrophilicity and exhibit superhydrophobic properties after the application of a hydrophobic agent. Moreover, the proposed modification method improves the resistance of a hierarchical texture to abrasive wear while remaining preserved high bactericidal properties. The results obtained have suggested that these modified textured copper materials can be used as bactericidal contact surfaces to combat nosocomial infections in medical facilities.

The water-repellent properties have been studied for the surface of a protective metal–ceramic coating based on titanium dioxide. It has been shown that the water-repellent properties of the coating surface can be efficiently changed by varying the technological parameters of spraying. When producing the coatings, technological parameters, such as the distance between a substrate and a detonation gun barrel (spraying distance) and the speed of barrel movement, have been varied. Regularities have been derived to relate the technological parameters of the detonation spraying of the coating and its contact angle. It has been found that, under certain conditions, the dependence of the contact angle on the spraying distance obeys a parabolic law. Parameters have been calculated for the phenomenological equation that adequately describes the observed parabolic dependence. The optimal values of the detonation spraying parameters necessary to achieve the maximum hydrophobicity of the produced coatings have been determined.

The Poisson–Boltzmann equation has been employed to consider the electrostatic interaction between two charged dielectric spherical particles in a solution of a symmetric electrolyte. The interaction forces between the particles of the same radius have been calculated by the finite element method under the condition of uniform charge distribution on their surfaces in the absence of an external field. The dependence of the electrostatic repulsion forces between the particles on the magnitude of the particle charges and the dielectric permittivities of the particle materials and the ambient medium has been analyzed.

The surfaces of solids (gold, silver, and polymers) have been modified with adsorption layers of various compounds. Optimal modification conditions have been determined using the methods of contact angle measuring and quartz crystal microbalance. The degree of surface coverage with the adsorption layer has been calculated and the data obtained have been compared with the results of the direct measurements of adsorption. The surface energy of the modifying layers has been determined and the potential application fields of the modified solids as functional materials have been demonstrated.

Modern power industry widely uses high-voltage overhead lines to transport electrical energy, with these lines encountering the problems of corona discharge and leakage currents, especially under the conditions of rain and snowfall. One of the approaches to solving these problems is the creation of protective coatings that can diminish corona discharge under adverse weather conditions. This paper reports the results of studying a hydrophilic organosilicon coating based on aminopropyltriethoxysilane and poly(ethylene glycol) for aluminum wires. The study of the coating resistance to a long-term contact with water, UV radiation, and ozone-saturated atmosphere has shown that the hydrophilicity of the coating increases under the influence of these factors, thus improving its anticorona properties. Thus, the durability of the developed coating under the operating conditions opens prospects for its use in the power engineering.

It is well known that super-hydrophobic materials have a wide application prospect. However, many methods for preparing super-amphiphobic coatings are too complicated or have poor stability, which limits the practical application of super-amphiphobic materials. In this paper, a stable and durable super-amphiphobic coating is prepared on the fabric surface via a simple sol-gel method. The water and vegetable oil contact angles of this coating are 160.5 ± 0.8° and 154.8 ± 2.6°, respectively. Specifically, the super-amphiphobic coating is prepared by grafting nano-silica on the surface of the fabric by a simple sol-gel method, and then grafted 1H, 1H,2H,2H-perfluorodecyltrimethoxysilane (FAS-17) as a hydrophobic modifier. After various chemical and mechanical stability tests, including concentrated ammonia solution soaking, saturated sodium hydroxide solution soaking, concentrated salt solution soaking, and THF soaking with stirring, the coating still maintains hydrophobicity. And the coating has excellent air permeability, which is expected to have great potential in the field of special protection.

The self-cleaning effect of titanium dioxide coatings is based on the photocatalytic oxidative ability and the phenomenon of photoinduced superhydrophilicity. Doping with metals is used to enhance the photocatalytic activity; however, its influence on the surface hydrophilicity remains to be studied. In this work, the effect of the heterovalent doping of titanium dioxide anatase on its hydrophilic properties has been investigated in detail. Thin xM–TiO₂ films, where the M symbol denotes Nb⁵⁺, Sc³⁺, and Al³⁺, with dopant concentrations of 0.0–1.0 at % have been obtained on glass substrates from solutions of corresponding sols by the deep coating method. The phase composition, surface dopant content, lattice microstress, surface acidity, and electron work function values have been determined and analyzed for three series of doped samples as functions of dopant concentrations. The surface hydrophilicity of xM–TiO₂ nanocoatings has been estimated by measuring water contact angle and surface free energy values. It has been shown that doping with niobium ions affects the wettability of titanium dioxide, while its hydrophilic state remains unchanged upon doping with scandium and aluminum ions. It has been found that the incorporation of niobium ions into anatase drastically increases the hydrophilicity of the surface with a simultaneous change in its acidity and work function. At the same time, as Nb content increases, the electronic factor prevails. The kinetic dependences obtained for the photoinduced water contact angles have shown an increase in the surface hydrophilicity of all investigated coatings irrespective of a dopant type within the studied dopant concentration range, thereby indicating their self-cleaning ability. At the same time, the final UV-induced hydrophilic state depends on a dopant type. The maximum surface hydrophilicity is achieved upon UV irradiation of TiO₂ doped with Nb regardless of its content. UV-irradiated Al-doped TiO₂ coatings exhibit small contact angles, while the photoinduced surface hydrophilicity of Sc-doped titanium dioxide films decreases with increasing scandium concentration.