Preparation and properties of oxidized multi-walled carbon nanotube superhydrophobic composites modified by bio-fatty acids.

In this paper, a preparation method of superhydrophobic composites of oxidized multi-walled carbon nanotubes modified by stearic acid (SA) is proposed. Hydroxylated multi-walled carbon nanotubes (HMWCNTs) were obtained by oxidizing multi-walled carbon nanotubes with potassium dichromate to give them hydroxyl groups on the surface. Subsequently, the carboxyl group in the SA molecule was esterified with the hydroxyl group on the HMWCNTs. SA molecules were grafted onto the surface of multi-walled carbon nanotubes. SA modified oxidized multi-walled carbon nanotubes (SMWCNT) superhydrophobic composites were obtained. The results show that the water contact angle (WCA) of superhydrophobic composites can reach up to 174°. At the same time, the modified nanocomposites have good anti-icing and corrosion resistance. After low temperature delayed freezing test, the freezing extension time of the nanocomposite film is 30 times that of the smooth surface. Under strong acid and alkali conditions, the superhydrophobic nanocomposites still maintain good superhydrophobicity. The nanocomposites may have potential applications in the preparation of large-scale superhydrophobic coatings.

Preparation and Anti-Icing Properties of Zirconia Superhydrophobic Coating.

Zirconia (ZrO2) is a ceramic material with high-temperature resistance and good insulating properties. Herein, for the first time, the surface of ZrO2 was modified with docosanoic acid (DCA) to improve its self-cleaning and hydrophobic properties. This surface modification transformed the surface of ZrO2 from hydrophilic to superhydrophobic. A two-step spraying method was used to prepare the superhydrophobic surface of ZrO2 by sequentially applying a primer and a topcoat. The primer was a solution configured using an epoxy resin as the adhesive and polyamide as the curing agent, while the topcoat was a modified ZrO2 solution. The superhydrophobic surface of ZrO2 exhibited a contact angle of 154° and a sliding angle of 4°. Scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, thermogravimetric analysis, and other analytical techniques were used to characterize the prepared zirconia particles and their surfaces. Moreover, results from surface self-cleaning and droplet freezing tests showed that DCA-modified ZrO2 can be well combined, and its coatings show good self-cleaning and anti-icing properties on TA2 bases.

Robust superhydrophobic self-cleaning coating prepared by silane modified multi-walled carbon nanotubes: A combined experimental and molecular dynamics study.

As a functional material, superhydrophobic coating has been widely studied in the field of self-cleaning. However, obtaining superhydrophobic coatings with robustness through simple preparation processes remains a challenge. In this paper, a robust superhydrophobic coating is prepared based on multi-walled carbon nanotubes modified by octyltrimethoxysilane, and its performance and hydrophobic mechanism are studied by experiments and molecular dynamics simulation. The superhydrophobic coating is prepared by one-step spraying method. The coating is characterized and analyzed by scanning electron microscopy and Fourier transform infrared spectroscopy, and the properties of the coating are tested by experiments. Molecular dynamics simulation is used in the study to construct a molecular model system, and the molecular modification mechanism and coating wettability are simulated under the COMPASSII force field. The results show that octyltrimethoxysilane successfully modified carbon nanotubes, and the hydroxyl groups at the head of the molecular chain are bound to the surface of the carbon nanotubes in the form of hydrogen bonds, while the tail of the molecular chain is far away from the surface. After modification, the surface of carbon nanotubes changed from hydrophilic to hydrophobic. The prepared superhydrophobic coating not only has excellent self-cleaning properties, but also exhibits corrosion resistance to acid and alkali solutions. The coating still has superhydrophobic when the wear length is in the range of 400 cm. It can be seen that a robust superhydrophobic self-cleaning coating is successfully prepared by a simple one-step spraying method. The modification mechanism and the hydrophobic mechanism of the coating were obtained by the combination of experiment and molecular dynamics simulation, which provided theoretical support for the superhydrophobic of the coating at the micro level.

Wettability Study of an Acidified Nano-TiO2 Superhydrophobic Surface.

The operation of aerospace equipment is often affected by icing and frosting. In order to reduce the loss caused by icing in the industrial field, it is an effective method to prepare superhydrophobic coatings by modifying nanoparticles with low surface energy materials. In order to explore a method of preparing a superhydrophobic surface that can be popularized, a two-step spraying method was employed to create a superhydrophobic coating. The surface was characterized by Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (SEM). The optimal preparation process was obtained by analyzing the surface contact angle data. The results showed that stearic acid was grafted onto the surface of TiO2 by esterification reaction. The existence of long methyl and methylene hydrophobic groups in the tail of the stearic acid molecule made the modified TiO2 hydrophobic. It is verified that water molecules have strong adsorption on the surface of unmodified TiO2. Stearic acid molecules can reduce the interfacial energy in the system.

Preparation of SiO2 resin coating with superhydrophobic wettability and anti-icing behavior analysis.

Among different types of anti-icing coatings, superhydrophobic surfaces have attracted extensive attention due to their excellent water repellency and low thermal conductivity. We report facile spraying time tuning to optimize the superhydrophobic (SHP) surface coating fabrication by a one-step spraying method of mixing SiO2 nanoparticles with epoxy resin (EP), polyamide resin (PAI), and HFTMS. The wettability performance was optimized by adjusting spraying time from 0 s to 25 s to control surface morphology by adjusting surface morphology and line roughness. With spraying time of 20 s, SiO2 molecular clusters on the superhydrophobic surface showed a maximum water contact angle (WCA) of 160.4° ± 1.3° and a sliding angle (SA) of 4.1° ± 1.0°. What's more, the effect of the coatings' icing behavior were studied by icing heat conduction; SHP-20 delayed the icing time for 410 s at -15 °C, and the icing performance of SHP-20 also declined with the decrease of temperature to -9 °C, -12 °C, -15 °C, and -18 °C. The WCA of SHP-20 can remain above 140.9° ± 1.8° after 40 abrasive 1000# sandpaper wear cycles. The results also provide a basis for the preparation of SHP and anti-icing characteristics.

Experimental study of methane hydrate generation characteristics in the presence of GO and Re-GO.

The industrial application of hydrate technology is greatly hindered by its slow generation rate, low gas storage rate, harsh generation conditions, and poor environmental friendliness of traditional additives. In this paper, the kinetic and thermodynamic promotion effects of graphene oxide (GO) and recovered graphene oxide (Re-GO) on methane hydrate in different systems were studied by the constant volume methods. The promotion mechanism was analyzed from the micro perspectives of molecular physical properties, interfacial reaction, and nucleation sites. It is found that GO has an excellent kinetic and thermodynamic promotion effect on CH4 hydrate generation. After the recovery process, the thermodynamic effect of Re-GO is basically unchanged, and the kinetic promotion effect is slightly reduced. Furthermore, it is verified that the GO material itself does not have a memory effect in hydrate formation. The results show that GO is an excellent accelerator of CH4 hydrate formation with high recovery value, which provides essential data and an experimental basis for the research and application of graphene oxide and hydrate technology in energy storage and cold storage.