Stearic Acid Ethanol Solution Research Articles

Preparation of cost-effective and hydrophobic freshness indicating labels based on passion fruit peel powder and stearic acid

Freshness indicating labels embedded with pH-sensitive anthocyanins are one type of smart packaging technology. However, the application of freshness indicating labels is mainly restricted by the high cost and hydrophilicity of the labels. In order to reduce the manufacturing cost, passion fruit (Passiflora edulis) peel powder rich in dietary fibers and anthocyanins was used to prepare freshness indicating labels in this study. Moreover, the prepared labels were further soaked in 0.01, 0.05 and 0.1 mol/L of stearic acid ethanol solution to increase the hydrophobicity of the labels. Structural characterization results showed the surface of the labels was covered by self-assembled stearic acid crystals. Stearic acid treatment significantly decreased the moisture content (16.90%→10.92%), hydrophilicity (water contact angle of 40.36°→103.01°), water vapor permeability (18.68 × 10−11 g m−1 s−1 Pa−1 → 8.10 × 10−11 g m−1 s−1 Pa−1) and water uptake ability of the labels, which effectively prevented the leak of anthocyanins from the labels. In addition, stearic acid treatment greatly elevated the inner compactness of the films, resulting in improved tensile strength (3.12 MPa→6.18 MPa) and thermal stability. Moreover, stearic acid treatment well maintained the pH-dependent color changeable ability of the labels. The labels changed from reddish brown to olive and brown in the application of shrimp freshness indicating. When the labels were buried in natural soil at 20 °C for 10 days, 82.74%−98.83% of the labels could be degraded. Therefore, this study provides a new and facile way to prepare freshness indicating labels.

Corrosion resistance study of Zn-Ni-B4C composite superhydrophobic coatings with hierarchical rough structure

The composite electrodeposition was used to successfully prepare Zn-Ni-B4C composite superhydrophobic plating with single γ-Ni5Zn21 phase and hierarchical micro/nanostructures on Q235 steel. The addition of micron B4C particles promoted the formation of micron protrusion structures and the change of current density promoted the development of hierarchical rough structures. Electroplated plated layers were electrodeposited at a current density of 5 A·dm−2 for 30 min and modified with an ethanol stearate solution to achieve a water contact angle of 159°, exhibiting excellent superhydrophobicity. Simultaneously, the superhydrophobic plating exhibits good anti-corrosion performance, and the corrosion current density of the plating in 3.5 wt% NaCl solution decreased significantly by 1 order of magnitude compared to the zinc-nickel alloy plating. After 96 h of immersion, the anti-corrosion performance was higher than the untreated Zn–Ni alloy plating, and the plating was still superhydrophobic after modification by stearic acid ethanol solution.

Facile fabrication of robust superhydrophobic coating for enhanced corrosion protection on AZ91 magnesium alloy by electroless Ni-B/GO plating

Artificial superhydrophobic surfaces have drawn extensive research interest due to their great applicational potential. However, the specialized materials and equipment, multistep preparation processes, and vulnerable rough structures severely restrict their industrial development. In this research, a robust superhydrophobic Ni-B/GO composite coating was fabricated successfully on AZ91 magnesium alloy based on electroless plating (EP), followed by chemical modification with stearic acid ethanol solution. With a water contact angle of 162.8° and a sliding angle of 1.3°, the superhydrophobic coating displayed strong physical/chemical stability and outstanding self-cleaning. Moreover, the superhydrophobic coating revealed excellent corrosion resistance with higher Ecorr (−0.411 V) and lower icorr (2.14 × 10−6 A·cm−2) in 3.5 wt% NaCl solution. Also, the Rct value was 2.75 × 105 Ω·cm2 and increased three orders of magnitude compared with the AZ91 Mg. Therefore, this study offers an innovative perspective for fabricating the micro/nano rough structures on magnesium alloy, and the fabrication of superhydrophobic coatings by electroless nickel plating as a low-cost and eco-friendly method will have good industrial application prospects.

Electrochemical corrosion resistance of hydrophobic coatings on ZE41A magnesium alloy synthesized by hydrothermal method

Two kinds of hydrophobic coatings on ZE41A magnesium alloy are successfully synthesized using hydrothermal method. The surface morphologies, wettability and anti-corrosion properties of hydrophobic coatings are investigated by the method of scanning electron microscopy, X-ray diffraction and electrochemical corrosion tests. Results show that the sample treated in stearic acid ethanol solution with addition of NiSO4 exhibits a morphology possessing large numbers of fine flower-like micro/nano structures, which results in better hydrophobicity and better corrosion resistance.

Constructing Superhydrophobic Surface on Copper Substrate with Dealloying-Forming and Solution-Immersion Method.

In this study, a superhydrophobic surface was constructed on a copper substrate through dealloying-forming and solution-immersion methods. The dealloying process for nanostructures on a copper surface involved the electrodeposition of zinc atoms, and the thermal alloying and chemical dealloying of zinc atoms. Then, a dealloyed copper surface was subsequently modified with low-surface-energy copper stearate to produce a superhydrophobic surface. Scanning electron microscopy, X-ray diffractometry, and Fourier transform infrared spectrometry were employed to characterize the morphological features and composition components of the surface in the fabrication process. The static contact angles of the copper surfaces were compared and evaluated based on various fabrication parameters, including electric current density, corrosive solution concentration, and nanostructures. The results indicated that a leaf-like copper stearate could be constructed through immersing a dealloyed copper plate into a 0.005 mol/L ethanol solution of stearic acid for 5 min. Nanostructures provided more attachment areas on the copper surface to facilitate the formation of copper stearate. The resulting as-prepared surface presented excellent superhydrophobic properties with a contact angle of over 156.5°, and showed the potential properties of non-sticking, self-cleaning, anti-corrosion, and stability. This study provides an efficient approach to fabricate superhydrophobic surfaces for engineering copper metals.

Fabrication and Characterization of Superhydrophobic Al-Based Surface Used for Finned-Tube Heat Exchangers.

Enhancing the heat transfer performance of heat exchangers is one of the main methods to reduce energy consumption and carbon emissions in heating, ventilation, air-conditioning and refrigeration (HVAC&R) systems. Wettability modified surfaces developed gradually may help. This study aims to improve the performance of heat exchangers from the perspective of component materials. The facile and cost-effective fabrication method of superhydrophobic Al-based finned-tube heat exchangers with acid etching and stearic acid self-assembly was proposed and optimized in this study, so that the modified Al fins could achieve stronger wettability and durability. The effect of process parameters on the wettability of the Al fins was by response surface methodology (RSM) and variance analysis. Then, the modified fins were characterized by field-emission scanning electron microscopy (FE-SEM), 3D topography profiler, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR), respectively. The durability of the superhydrophobic fins was investigated by air exposure, corrosion resistance, and mechanical robustness experiments. The RSM and variance analysis demonstrated that a water contact angle (WCA) of 166.9° can be obtained with the etching time in 2 mol/L HCl solution of 10.5 min, the self-assembly time in the stearic acid ethanol solution of 48 h, and drying under 73.0 °C. The surface morphology showed suitable micro-nano structures with a mean roughness (Ra) of 467.58 nm and a maximum peak-to-valley vertical distance (Rt) of 4.095 μm. The chemical component demonstrated the self-assembly of an alkyl chain. The WCAs declined slightly in durability experiments, which showed the feasibility of the superhydrophobic heat exchangers under actual conditions.

Fish-scale nickel mesh with switchable wettability for efficient oil/water separation

In the daily life of human beings, sewage discharge and oil spill accidents occur from time to time. New types of controllable oil/water separation interface materials have received more attention. In this study, we proposed a simple and environmentally friendly method to prepare a Nickel filter with switchable wettability. The final product is prepared by high temperature calcination and soaked with stearic acid ethanol solution. The prepared filter screen has selective separation performance for oil/water mixture with switchable surface wettability between superhydrophobic and superhydrophilic. The separation efficiency is higher than 99.50%, and the flux rate is as high as 46.25 L m−2s−1 for water-removing process and 40.22 L m−2s−1 for oil-removing process. The wettability conversion of the membrane can be achieved through heating treatment and soaking treatment, and it still has good oil/water separation performance. After 20 times of cycles, the separation efficiency remains unchanged, and the flux remain above 40.06 L m−2s−1 for oil removal and 36.81 L m−2s−1 for water removal process. The results show that the prepared nickel filter screen has good practical application prospects such as water reclamation and oil spill treatment.

Superhydrophobic wood surface fabricated by Cu2O nano-particles and stearic acid: its acid/alkali and wear resistance

Abstract Reducing the hydrophilic nature of wood could enhance dimensional stability and improve life cycle performance. Masson pine and pecan wood were modified to create superhydrophobic, self-cleaning functions by spray-coating with Cu2O nano-particles (Cu2O NPs)/phenol formaldehyde (PF) resin mixed solution followed by immersion in a stearic acid ethanol solution. Two types of Cu2O NPs, derived from different concentrations of copper chloride (CuCl2) were evaluated for their ability to improve hydrophobicity of wood surface. A special petal-shaped structure on the edge of Cu2O NPs was found on modified pecan wood, and water contact angles (WCA) of both kind of modified wood reached around 155° and sliding angles (SA) less than 10°. Meanwhile, low liquid permeability and excellent repellency to aqueous solutions with pH = 1 to 13 were achieved. The critical WCA around 150° was also maintained on modified wood surfaces after being immersed in strong acid (pH = 2) and strong alkali (pH = 12) solutions for 12 h. Furthermore, remarkable mechanical durability was obtained after harsh abrading test, which could be attributed to the high bond strength from cured PF resin adhesive. Such highly waterproof, acid/alkali resistant and hard-wearing superhydrophobic surface must have potential to be widely applied in wood products industry.

A solvent-responsive robust superwetting titanium dioxide-based metal rubber for oil-water separation and dye degradation

The sewage treatment technology of oil-water separation based on superwetting materials has been widely employed. However, the stability of substrates was rarely considered in the past few years, which greatly limited the application of superwetting materials in engineering field. As a new robust, three-dimensional porous material, metal rubber (MR) has attracted significant attention for solving this problem. To treat the wastewater containing insoluble heavy/light oil and soluble dyes, herein, MR capable of degrading organic dyes with switchable wettability and high oil-water separation efficiency was prepared. Firstly, the superhydrophilic MR was obtained by anodizing. Then, the wettability of MR surface was reversibly switched between superhydrophilic and superhydrophobic via alternate immersion in stearic acid ethanol solution and tetrahydrofuran (THF) solvent to achieve switchable oil-water separation of MR. The superwetting MR displayed excellent abrasion resistance and retained outstanding oil-water separation performance after 100 times of sandpaper abrasion. Besides, the surface of pure titanium MR was rich in titanium dioxide (TiO2) after anodic oxidation, which could effectively degrade the organic dyes under ultraviolet light. Therefore, the as-prepared superwetting MR possesses the ability to treat complex wastewater and have applications prospects in controllable oil-water separation and self-cleaning surfaces.

Fabrication of the superhydrophobic natural cellulosic paper with different wettability and oil/water separation application

AbstractRenewable superhydrophobic materials have attracted great attention due to their extensive applications in the fields such as cost‐effective and biodegradable oil/water separation field. Herein, we reported an eco‐friendly and facile methodology to develop the superhydrophobic cellulosic paper by immersion method using the ethanol solution of stearic acid. Furthermore, the treated cellulosic papers showed super‐hydrophobicity with water contact angle (WCA) above 153°. Interestingly, this method can realize superhydrophobic‐hydrophilic conversion by simply adjusting the temperature and is amenable for different substrates and with the WCA of 114‐162°. More importantly, the utilization of fluorinated reagents has been avoided, thereby minimizing the production cost and improving safety and environmental aspects. Meanwhile, the modified natural cellulosic paper is applied for oil–water separation, and its separation efficiency was as high as 95% after 10 cycles, indicating the good reusability of stearic acid modified filter papers. Consequently, this simple strategy based on the stearic acid immersion method thus provided an easy conversion of superhydrophobic‐hydrophilic interface and provided facile strategies for conversion of commercial quantitative filter paper to functional materials for oil/water separation.

Copper-based nanoribbons fabricated on a copper substrate by a liquid-solid reaction and their corrosion performance

In this study, copper oxide nanoribbons were fabricated on a Cu substrate by a simple liquid-solid reaction. The superhydrophobic copper oxide surface was formed by the immersion of the sample in an ethanol solution of stearic acid. The water contact angle on this surface was 153.6°. A slippery copper oxide surface was prepared by the immersion of superhydrophobic copper oxide in DuPont Krytox. Electrochemical measurement revealed that the corrosion resistance of the slippery surface was more stable than those of bare Cu and superhydrophobic surface. The inhibition efficiency reached up to 92.68%. This study provided a possible method for preventing copper corrosion.

Hydrophobic Modification of Magnesium Hydroxide Coating Deposited Cathodically on Magnesium Alloy and its Corrosion Protection

In this paper, hydrophobic modification of magnesium hydroxide film prepared by cathodic deposition on ME20M Mg alloy was achieved with ethanol solution of stearic acid. The effects of solution concentration, temperature and treatment time on the surface wettability were investigated. The corrosion behaviors of typical samples were evaluated by droplet test, total immersion corrosion test as well as PDP (Potentiodynamic Polarization) and EIS (Electrochemical Impedance Spectroscopy) techniques, respectively. Adhesion of coatings to the substrate were examined by tape test. The surface morphology and chemical composition of typical coatings were characterized by SEM, FTIR and XRD respectively. The results indicate that the superhydrophobic surface with 151.5° water static contact angle and 1° sliding angle could be fabricated successfully by simple immersion in a low-concentration stearic acid solution for a short period. Compared with blank sample, the composite surface modification based on cathodic deposition (CD) plus hydrophobic treatment (HT) extended the discoloration time in droplet tests by nearly 25 fold, decreased the icorr (corrosion current density) by three orders of magnitude, and increased the characteristic impedance modulus at 0.1 Hz by nearly four orders of magnitude, indicating that the CD/HT composite surface modification could enhance the corrosion resistance of Mg alloy significantly.

Creating Superhydrophobic Polymer Surfaces with Superstrong Resistance to Harsh Cleaning and Mechanical Abrasion Fabricated by Scalable One‐Step Thermal‐Imprinting

AbstractIn this work, a scalable thermal imprinting method that allows to directly fabricate superhydrophobic polymer surfaces with superstrong resistance to harsh cleaning and mechanical abrasion is reported. A titanium (Ti) mold is produced by femtosecond laser processing to possess a hierarchical micro‐ and nanoscale pattern. Through thermal imprinting, this hierarchical pattern onto poly(propylene) sheets is able to be accurately reproduced, rending the polymer surface superhydrophobic. The imprinting method employed uses an aqueous ethanol solution of stearic acid to assist demolding, and periodically uses xylene to limit mold contamination and restore the mold to excellent condition for further imprinting. These strategies allow to repeatedly use the mold over 50 times without degradation. A range of durability tests are further performed, and showed that the produced suprehydrophobility on the poly(propylene) sheets exhibit excellent durability, withstanding brush washing, ultrasound cleaning, and sandpaper abrasion. The reported method can also be used to fabricate superhydrophobic surfaces of various thermoplastics that are broadly utilized in daily life.

Fabrication of corrosion-resistant superhydrophobic coating on magnesium alloy by one-step electrodeposition method

A one-step electrodeposition method was used to construct a superhydrophobic coating on the surface of magnesium alloy. Using magnesium nitrate and ethanol solution of stearic acid as electrolyte, four groups of electrolytes with different ratios of stearic acid and magnesium nitrate were designed to explore the influence of electrolyte to the process. The contact angles of the four coating samples were 136.4 ± 5.8°, 152.7 ± 2.8°, 156.2 ± 4.9° and 155.1 ± 4.4° The addition of magnesium nitrate in the solution increased the hydrogen evolution reaction in the electrodeposition process, which was not conducive to electrodeposition process. During the deposition process, the sample prepared in a molar ratio of stearic acid to magnesium nitrate of 10:1 had the best corrosion resistance, and its corrosion circuit density was 3.74 × 10−8 A/cm2, far lower than the corrosion current density of the magnesium alloy substrate.

A universal method to fabricate Cu films with superhydrophobic and anti-corrosion properties

ABSTRACTMulti-functional Cu films were fabricated by an improved electric brush-plating technique and subsequent immersion treatment in ethanol solution of stearic acid. The brush-plated Cu film exhibited unique lotus-like surface architectures, which endowed it with highly hydrophobicity, instead of metallic intrinsic hydrophilicity. After solution-immersion for certain time, the Cu films were gradually covered by a continuous net-like layer of copper stearate nano-sheets with low surface energy, which finally rendered them stable superhydrophobic and even self-cleaning. Electrochemical measurement revealed that anti-corrosion property of Cu is intimately linked with its surface wettability, and the superhydrophobicity indeed provides high corrosion resistance for Cu substrate in corrosion environment. This strategy can extend generally to other relevant metals.

Superhydrophobic Al Surfaces with Properties of Anticorrosion and Reparability.

Aluminum (Al) is one of the most widely used metals for industry and household applications, but its longevity is limited by its tendency for corrosion. In this work, we report a facile method to fabricate superhydrophobic Al surfaces that have excellent anti-corrosion effect. The surface is obtained by etching Al in CuCl2 solution to form the micro–nano-pit surface texture followed by lowering its surface energy in an aqueous ethanol solution of stearic acid. The superhydrophobic Al surfaces show water contact angles as high as 165°. Electrochemical tests demonstrate that the corrosion rate of the Al surface drops by 94.5% after the superhydrophobic modification (corrosion current density lowers from 1.11 × 10–4 to 6.10 × 10–6 A cm–2). We also show that the superhydrophobic surface will protect the Al from corrosion even under a very harsh environment. In addition, our method is scalable and the superhydrophobic surfaces exhibit excellent flexible and reparable properties. This anti-corrosive superhydrophobic Al surface will prolong Al in its broad usage.

A stable eco-friendly superhydrophobic/superoleophilic copper mesh fabricated by one-step immersion for efficient oil/water separation

With the frequently happened oil spill accidents and increasing discharge of industrial oily wastewater, oil/water separation has become a global challenge for protecting ecological environments. In this research, a superhydrophobic and superoleophilic copper mesh is prepared by a simple one-step immersion approach. A hydrophobic original copper mesh (OCM) turns into a superhydrophobic copper mesh (SHCM) after being immersed in stearic acid ethanol solution for 24 h. The as-fabricated SHCM demonstrates a separation efficiency of over 97% for different oil/water mixtures, and an oil flux of >90 kL·h−1·m−2. Moreover, the SHCM exhibits excellent stability under different working conditions. The SHCM obtained by such simple, scalable, and low cost one-step approach, holds great promise for future applications in oil/water separation.

Improving Corrosion Resistance of Copper by Forming Super Hydrophobic Layer on Surfac

Improving corrosion resistance of copper is often associated with the presence of cuprous oxide (Cu2O) films on the surface. Many surface modification techniques such as chemical etching, oxidation, inhibitors, electro deposition and sol-gel could be employed In the present work a film of Cu2O, which is considered to be protective and strongly adherent to the substrate, is formed. Experimental technique includes etching of copper specimens in ammonia solution, calcination, and then modified in ethanol solution of stearic acid for different times was employed Etching of copper for 60 h in 10 wt. % ammonia solution exhibits a contact angle of 135˚ but the formed layer, which is CuO, has poor adhesion. Modifying of etched-calcined copper in 0.1 mol/L ethanol solution of stearic acid for 3 h shows a superhydrophobic film (Cu2O) with a high contact angle of 160˚, good adhesion and lowest corrosion rate. The contact angle was measured at ambient temperature. The surface morphology and chemical compositions of the samples were investigated with a scanning electron microscopy, EDX and an X-ray diffraction. Electrochemical corrosion behavior was conducted in 3 wt. % NaCl aqueous solution at room temperature. The contact angle was measured using Attension Biolin device (Theta Optical Tensiometers) Also Thickness (using Tooke Inspection Guage OG204 according to ASTM D4138) and adhesion (using X-Cut Tape Adhesion test according to ASTM D3359) of formed films were determined

Preparation and corrosion resistance of superhydrophobic coatings on AZ31 magnesium alloy

Abstract In order to improve the corrosion resistance of the Mg alloys, the superhydrophobic coatings on AZ31 Mg alloy were prepared by a two-step process of micro-arc oxidation treatment and superhydrophobic treatment in stearic acid ethanol solution. The effects of voltages, frequencies and treatment time on the contact angle of the superhydrophobic treated sample were investigated. The results showed that with increasing the voltage, frequency and treatment time, all of the contact angles of the superhydrophobic treated sample increased first, and then decreased, reaching the maximum values at 350 V, 1000 Hz and 5 min, respectively. The optimal superhydrophobic coating was mainly composed of MgO and Mg2SiO4 phases, with the pore diameter of ∼900 nm, the thickness of ∼6.86 μm and the contact angle of 156.96°. The corrosion current density of the superhydrophobic AZ31 sample decreased by three orders of magnitude, and the amount of hydrogen evolution decreased by 94.77% compared with that of the AZ31 substrate sample.

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.