Stearic Acid Ethanol Solution Research Articles

Construction of caterpillar-like cobalt-nickel hydroxide/carbon cloth hierarchical architecture with reversible wettability towards on-demand oil-water separation

Superwettability materials have focused considerable interest of researchers due to their extensive applications like oil/water separation. Currently, the development of materials with controllable wettability for efficient on-demand oil/water separation is highly desired. In this work, we constructed caterpillar-like cobalt-nickel hydroxide/carbon cloth hierarchical architecture via in situ hydrothermal growth. Interestingly, this hierarchical architecture shows reversible wettability after immersing in stearic acid ethanol solution and tetrahydrofuran, which can be used for efficient on-demand oil/water separation. This hierarchical architecture is proved to have excellent environmental and mechanical durability. Moreover, the fluid-based gating and liquid-infusion-interface mechanism are presented to explain oil/water separation process. The caterpillar-like cobalt-nickel hydroxide/carbon cloth with low cost and simple preparation shows a promising prospect in the application of efficient on-demand oil/water separation.

Superhydrophobic Coatings on Aluminium Based on Carboxylic Acids

Development of new coatings for corrosion protection should be directed to environmentally friendly yet efficient technologies. Industrial applications additionally demand energy sustainability and cost effectiveness. Among varieties of new coatings being developed superhydrophobic coatings are also in the focus of current research in both academic and industrial sectors. The background of their use, inspired by effects in nature, is the prevention of ingress of electrolyte to underlying substrate and properties of self-cleaning and anti-sticking. Superhydrophic surfaces can be applied to different substrates, from metal, textile, plastics, etc. Superhydrophobicity can be related to surface texture or surface chemistry, e.g., use of silane-, fluoro-based or other compounds [1]. The basic idea of the current research study is to design multifunctional compounds by integrating corrosion inhibitors and hydrophobic agents with lipophilic or fluorous properties into hybrid matrices so as to produce a corrosion resistant hydrophobic coating that display good adhesion to Al substrates. The first step is to test potential candidates for (i) hydrophobic compounds and (ii) corrosion inhibitor compounds. Among hydrophobic compounds, carboxylic acids were tested since they offer environmentally friendly and cheap option. In order to adsorb carboxylic acids on metal surface an appropriate pre-treatment is required. In the present work we investigated the possibility to fabricate superhydrophobic surfaces on aluminium metal pre-treated by alkaline etching at 90 °C [2] which represents a green solution-phase method to produces hierarchical growth of the aluminium hydroxide array. After immersion in ethanol solution of carboxylic acid the surface turns superhydrophobic. In the present study we have investigated the effect of several parameters on the formation of superhydrophobic surface on aluminium pre-treated by etching: type of etching as a pre-treatment, length of carboxylic chain, time of immersion in carboxylic acid and concentration of carboxylic acid. The effect of these parameters on the water contact angle and corrosion properties in 0.5 M NaCl solution were determined. Depending on the type of carboxylic acid a remarkable decrease in both cathodic and anodic current density can be achieved. Optimal parameters were denoted as those achieving high water contact angle, and low corrosion current density combined with a broad passive range. XPS showed that after alkaline etching the aluminium surface was fully covered by an hydroxide layer. ToF-SIMS provided direct evidence of adsorption of octanoic and stearic acids. Coatings prepared on Al by self-assembling in carboxylic acids were tested also by long-term immersion in NaCl solution. Surface durability in terms of resistance in acid and alkaline solution, as well as sliding angle were determined. Morphology of self-assembled carboxylic layers on alkaline etched aluminium analysed by FE-SEM shows nano-rough surface with numerous micro-cones with steps or terraces giving the surface a dual roughness. Composition of the surface was investigated using various surface analytical methods, i.e. FTIR, XPS and SIMS. Adsorption bonding of carboxylic acids to hydroxylated Al surfaces is also being investigated by DFT calculations. We utilized periodic slab model of passivated surface with hydroxylated oxide-layer supported on Al metal. These calculations help us to scrutinize details of how carboxylic head-groups attach to hydroxylated surface and how lateral intermolecular interactions and their self-assembly depends on the length of the aklyl tail. The effect of the organic layer composition on the resulting electronic properties of the passive layer (band gap, electronic workfunction) is also investigated. Fig. 1. FE-SEM image of aluminium surface etched in NaOH and immersed in 5 mM ethanol solution of stearic acid. Detail: contact angle of water drop 156°. Acknowledgments: This work is a part of M.ERA-NET project entitled “Design of corrosion resistant coatings targeted for versatile applications”, acronym COR_ID. The financial support of the project by Ministry of Education, Science and Sport of Republic of Slovenia (Programmes of International Scientific Cooperation) and Agence Nationale de la Recherche, France, is acknowledged.

Facile electrodeposition of superhydrophobic and oil-repellent thick layers on steel substrate

The aim of this work is to produce liquid-repellent surface on stainless steel via simple electrodeposition. For this purpose, myristic acid, stearic acid ethanol solution and perfluorooctanoic acid aqueous solution were used. Resulting contact angles and surface energy values were studied. Superhydrophobic and superoleophobic behavior of samples prepared using perfluorooctanoic acid electrolyte were performed by contact angle 159° for deionized water, 153° for olive oil and low surface energy 0.60mJ/m2. Relation between the non-wettable behavior of samples, surface structure, chemical composition and mechanical properties were observed by SEM with EDX analysis, FTIR spectroscopy and tribological measurement, giving the preference to fluorinated precursor and low voltage electrodeposition.

Experimental investigation on surface wettability of copper-based dry bioelectrodes

Laser micromilling technology was used to fabricate a dry bioelectrode with a surface microstructure array, which was then treated with stearic acid ethanol solution. A superhydrophobic dry bioelectrode was obtained. Based on the scanning electron microscopy results, the formation of the dry bioelectrode with a surface microstructure array had been discussed. Later, the contact angle on the bioelectrode surface was analyzed by changing the parameters such as laser processing parameters, spacing of microstructure, and the working media. The results show that the contact angle of the bioelectrode surface treated with stearic acid ethanol solution was approximately 151°, and this value was compared with the result for bioelectrodes that were not treated or placed in air. The laser power and number of scans had significant influences on the contact angle, while the scanning speed had only a slight influence. When the spacing of microstructure was in the range of 0.1–0.5mm, the contact angle increased with a decrease in the spacing of microstructure. In addition, the contact angle on the bioelectrode with deionized water or saline water as the working media was greater than 150°. Our developed dry bioelectrode presented good hydrophobic properties to help to realize a stable measurement system over a long time, which has many applications in the detection and measurement of biological signals.

A facile method to fabricate functionally integrated devices for oil/water separation.

In this paper, we present a facile method for the fabrication of a functionally integrated device, which has the multi-functions of the oil-containment boom, oil-sorption material, and water/oil-separating film, through a single immersion step in an ethanol solution of stearic acid. During the simple immersion process, the two dominant factors of superhydrophobicity, surface roughness and low-surface-energy coatings, could be accomplished simultaneously. The as-prepared functionally integrated device with superhydrophobicity/superoleophilicity displayed a lower density than that of water, such that it could float on water and act as an oil-containment boom; an efficient oil-absorbing property, which was attributed to the capillary effect caused by micrometer-sized pore structures and could be used as oil-sorption materials; a high oil/water separating efficiency which was suitable for water/oil-separating film. In this way, the functions of oil collection, absorption, and water/oil separation are integrated into a single device, and these functions could work independently, reducing the cost in terms of energy consumption and being versatile for a wide range of applications.

Fabrication of anti-adhesion surfaces on aluminium substrates of rubber plastic moulds using electrolysis plasma treatment

An anti-adhesion surface with a water contact angle of 167° was fabricated on aluminium samples of rubber plastic moulds by electrolysis plasma treatment using mixed electrolytes of C6H5O7(NH4)3 and Na2SO4, followed by fluorination. To optimise the fabrication conditions, several important processing parameters such as the discharge voltage, discharge time, concentrations of supporting electrolyte and stearic acid ethanol solution were examined systematically. Using scanning electron microscopy (SEM) to analyse surfaces morphology, micrometer scale pits, and protrusions were found on the surface, with numerous nanometer mastoids contained in the protrusions. These binary micro/nano-scale structures, which are similar to the micro-structures of soil-burrowing animals, play a critical role in achieving low adhesion properties. Otherwise, the anti-adhesion behaviours of the resulting samples were analysed by the atomic force microscope (AFM), Fourier-transform infrared spectrophotometer (FTIR), electrons probe micro-analyzer (EPMA), optical contact angle meter, digital Vickers microhardness (Hv) tester, and electronic universal testing. The results show that the electrolysis plasma treatment does not require complex processing parameters, using a simple device, and is an environment-friendly and effective method. Under the optimised conditions, the contact angle (CA) for the modified anti-adhesion surface is up to 167°, the sliding angle (SA) is less than 2°, roughness of the sample surface is only 0.409μm. Moreover, the adhesion force and Hv are 0. 9KN and 385, respectively.

A novel solution-controlled hydrogel coated mesh for oil/water separation based on monolayer electrostatic self-assembly

Solution-controlled hydrogel coated materials for oil/water separation have been successfully fabricated. The as-prepared mesh can switch between superhydrophilicity/underwater superoleophobicity and superhydrophobicity/superoleophilicity through self-assembly and dis-assembly pathways. The PDMAEMA hydrogel coated mesh is firstly prepared via photo induced free radical polymerization. A facile monolayer electrostatic self-assembly method was involved by immersing the hydrogel coated mesh in an ethanol solution of stearic acid for a few minutes. The stearic acid modified mesh converts to superhydrophobicity/superoleophilicity. More importantly, the mesh can return to the original state swiftly after the dis-assembly of the monolayer by immersion in a NaOH aqueous solution. The unique superiority of this material is that the transition of wettability can be achieved in situ, so that oil and water can pass through the mesh in sequence through the control of the NaOH solution. Therefore, the as-prepared meshes have great potential in practical applications dealing with both water-rich and oil-rich oil/water mixture separation with high separation efficiency (>99.3%). The synthetic method is simple, time saving and cost saving.

A facile solvent-manipulated mesh for reversible oil/water separation.

A controllable oil/water separation mesh has been successfully developed and easily manipulated by immersion in a stearic acid ethanol solution and tetrahydrofuran with a very short period of time. The superhydrophilic and underwater superoleophobic mesh is first obtained via a one-step chemical oxidation and subsequently converts to superhydrophobic after it is immersed in an ethanol solution of stearic acid for 5 min. The surface wettability is regained to superhydrophilic quickly by immersion in tetrahydrofuran for 5 min. More importantly, the reversible superhydrophobic-and-superhydrophilic switching can be repeated multiple times with almost no visible morphology variation. Therefore, this approach provides potential application in controllable oil/water separation and opens up new perspectives in manipulation of various metallic oxide substrates.

Preparation of Superhydrophobic Surface on Copper Foils by a Facile Method

In the paper, we prepared superhydrophobic surfaces on copper foils via a facile solution-immersing method. The influence of experiment conditions, such as solution concentration, immersing time and temperature, on the surface structure is investigated in detail. When the concentration of stearic acid-ethanol solution, the immersing time and the temperature are 2 g/L, 120 min and 40°,respectively, the resulting copper surface possesses great superhydrophobicity with a water contact angle of up to 159° and a sliding angle of only 3°.

Fabrication of superhydrophobic surfaces with high adhesive forces towards water on steel substrates

The present Letter reports a simple and effective two-steps immersion method to fabricate superhydrphobic surfaces with high adhesive forces towards water on steel substrates. The steel plates were firstly immersed in the aqueous CuSO4 solution for 20 s, and then immersed in the stearic acid ethanol solution for 24 h. The sample surfaces were characterised by scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectrophotometry, X-ray diffraction and optical contact angle measurements. The results show that, after two-steps immersion processes, the cupric stearate microspheres with binary micro/nanometre-scale rough structures are formed on the steel surfaces. The as-prepared steel surfaces exhibit a good high adhesive superhydrophobicity with a 166.3° water contact angle and no rolling angle. The high adhesive superhydrophobic surfaces on steel substrates have a good potential application in no loss liquid transportation.