Huaiyuan Wang

A novel carbon nanotubes reinforced superhydrophobic and superoleophilic polyurethane sponge for selective oil–water separation through a chemical fabrication

Oil spillage and industrial oily wastewater have caused severe environmental concerns. A super absorbent material capable of separating oil–water mixtures, especially with a high absorption capacity and mechanical strength, is urgently desired. Here, a common and feasible approach to fabricate carbon nanotubes (CNTs) reinforced polyurethane (PU) sponge is presented that shows superhydrophobic and superoleophilic properties. The method involves the oxidative self-polymerization of dopamine and the reaction of hydrophilic polydopamine (PDA) with hydrophobic octadecylamine (ODA). The superhydrophobic stability of the as-prepared sponge with temperatures and in corrosive solutions of different pH is investigated. The as-prepared sponge could quickly and selectively absorb various kinds of oils up to 34.9 times of its own weight, and the absorbed oils can be collected by a simple squeezing process. More interestingly, the mechanical strength of the as-prepared sponge is improved due to the structural reinforcement of CNTs anchored on the sponge skeleton. Furthermore, the recovered sponge could be reused to separate oil–water mixture 150 times while maintaining its high absorption capacity. This promising multifunctional sponge exhibits significant potential as an efficient absorbent in large-scale oil–water separation applications.

Superamphiphobic and Electroactive Nanocomposite toward Self-Cleaning, Antiwear, and Anticorrosion Coatings

Multifunctional coatings are in urgent demand in emerging fields. In this work, nanocomposite coatings with extraordinary self-cleaning, antiwear, and anticorrosion properties were prepared on aluminum substrate by a facile spraying technique. Core-shell structured polyaniline/functionalized carbon nanotubes (PANI/fCNTs) composite and nanosized silica were synergistically integrated into ethylene tetrafluoroethylene (ETFE) matrix to construct lotus-leaf-like structures, and 1H,1H,2H,2H- perfluorooctyltriethoxysilane (POTS) was used to decrease the surface energy. The composite coating with 6 wt % PANI/fCNTs possesses superamphiphobic property, with contact angles of 167°, 163°, and 159° toward water, glycerol, and ethylene glycol, respectively. This coating demonstrates stable nonwetting performance over a wide temperature range (<400 °C), as well as outstanding self-cleaning ability to prevent contamination by sludge, concentrated H2SO4, and ethylene glycol. Superamphiphobic surface property could be maintained even after 45 000 times abrasion or bending test for 30 times. The coating displayed strong adhesive ability (grade 1 according to the GB/T9286) on the etched aluminum plate. The superamphiphobic surface could be retained after immersion in 1 mol/L HCl and 3.5 wt % NaCl solutions for 60 and 90 d, respectively. It should be noted that this coating reveals significantly improved anticorrosion performance as compared to the bare ETFE coating and ETFE composite coating without PANI/fCNTs. Such coatings with integrated functionalities offer promising self-cleaning and anticorrosion applications under erosive/abrasive environment.

The fabrication, nano/micro-structure, heat- and wear-resistance of the superhydrophobic PPS/PTFE composite coatings.

A simple engineering method was used to fabricate stability and wear-resistance of superhydrophobic PPS-based PPS/PTFE surfaces through nano/micro-structure design and modification of the lowest surface energy groups (-CF2-), which was inspired by the biomimic lotus leaves. The hydrophobic properties and wear-resistance of the coatings were measured by a contact angle meter and evaluated on a pin-on-disk friction and wear tester, respectively. Moreover, the surfaces of the PPS/PTFE composite coatings were investigated by means of scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), and thermogravimetry (TG) analysis. Results showed that the highest contact angle of the PPS/PTFE surface, with papillae-like randomly distributed double-scale structure, could reach up to 162°. When 1 wt.% PDMS was added, the highest contact angle could hold is 172°. The coatings also retained superhydrophobicity, even under high temperature environment. The investigation also indicated that the coatings were not only superhydrophobic but also oleophobic behavior at room temperature, such as the crude oil, glycerol, and oil-water mixture. The PPS/45%PTFE coatings had more stable friction coefficient and excellent wear-resistance (331,407 cycles) compared with those with less than 45% of PTFE.

Comparative Study of Tribological Properties of Different Fibers Reinforced PTFE/PEEK Composites at Elevated Temperatures

The friction and wear properties of PTFE/PEEK composites filled with potassium titanate whisker (PTW) or short carbon fiber (CF) at elevated temperatures (160, 180, 200, 220, and 240°C), different loads (100 and 200 N), and various sliding velocities (0.7 and 1.4 m/s) were investigated in this article. The results show that the friction coefficient of PTW/PTFE/PEEK composites is more stable and 30% lower than that of CF/PTFE/PEEK composites at various sliding conditions. Moreover, it is found that the wear rate of PTW-filled PTFE/PEEK composites is only 10 to 40% that of CF/PTFE/PEEK composites. The wear rate of PTW/PTFE/PEEK composites is only 20% of CF/PTFE/PEEK composites at 200 N, 1.4 m/s, and 240°C. Scanning electron microscopy (SEM) study reveals that PTW can reduce the adhesive wear of PTFE/PEEK composites.

Non-corrosive green lubricants: strengthened lignin–[choline][amino acid] ionic liquids interaction via reciprocal hydrogen bonding

A series of novel green lubricants with dissolved lignin in [choline][amino acid] ([CH][AA]) ionic liquids (ILs) have been synthesized in this work. The effect of lignin on the thermal and tribological properties of the lignin/[CH][AA] lubricants was systematically investigated by means of thermogravimetric analysis, differential scanning calorimetry, and a friction and wear tester. The lignin in [CH][AA] has been demonstrated to be an effective additive to improve thermal stability, reduce the wear rates and stabilize the friction coefficients of lignin/[CH][AA] lubricants. Density function theory calculations on the electronic structure of [CH][AA] ILs reveal the atomic natural charge of ILs and their hydrogen bonding capability with lignin. Moreover, these green lubricants show excellent anti-corrosive properties against commercial aluminum and iron boards. The strong physical adsorption of [CH][AA] ILs onto the steel surface and the reciprocal hydrogen bonding between [CH][AA] ILs and lignin synergistically contribute to the enhanced lubrication film strength and thus the tribological properties of these new lubricants. This work provides a new perspective on utilizing complete bio-products in advanced tribological lubrication systems. In addition, this will open a new application venue for lignin to improve product value in lignocellulosic biomass utilization.

Superhydrophobic polyaniline hollow spheres with mesoporous brain-like convex-fold shell textures

Novel hollow nano/microspheres of polyaniline (PANI) with mesoporous brain-like convex-fold shell structures were prepared via a new micelle-mediated phase transfer method, using perfluorooctanoic acid (PFOA)/aniline as a soft template. These self-assembled hollow spheres possess high specific surface areas (835.7 m2 g−1), and uniform particle morphology with narrowly distributed particle size can be controlled by adjusting the PFOA/aniline molar ratio and polymerization time. The conductive emeraldine state of PANI is also confirmed by FT-IR spectroscopy, UV-vis spectroscopy, X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry. In particular, these PANI spheres exhibit superhydrophobicity and high oleophobicity simultaneously, with contact angles of 165 ± 0.9°, 134 ± 0.8°, 131 ± 0.9° and 125 ± 0.7° towards water, glycerin, ethylene glycol and corn oil, respectively. Furthermore, the mechanisms of PANI structural evolution are proposed involving the formation, phase transfer and self-reassembly process of PFOA/aniline spherical micelles.

Ionic Grease Lubricants: Protic [Triethanolamine][Oleic Acid] and Aprotic [Choline][Oleic Acid].

Ionic liquid lubricants or lubricant additives have been studied intensively over past decades. However, ionic grease serving as lubricant has rarely been investigated so far. In this work, novel protic [triethanolamine][oleic acid] and aprotic [choline][oleic acid] ionic greases are successfully synthesized. These ionic greases can be directly used as lubricants without adding thickeners or other additives. Their distinct thermal and rheological properties are investigated and are well-correlated to their tribological properties. It is revealed that aprotic ionic grease shows superior temperature- and pressure-tolerant lubrication properties over those of protic ionic grease. The lubrication mechanism is studied, and it reveals that strong physical adsorption of ionic grease onto friction surface plays a dominating role for promoted lubrication instead of tribo-chemical film formation.

Carbon monolith with embedded mesopores and nanoparticles as a novel adsorbent for water treatment

A novel carbon monolith material with embedded mesopores and nanoparticles has been synthesized via a facile catalytic graphitization process by using natural wood as the carbon precursor. BET results reveal a large specific surface area of 273.0 m2 g−1 and a narrow pore size distribution, with pore diameters of ∼4.0 nm. This unique material shows excellent toxic pollutants removal from water, including inorganic heavy metal ion (chromium(VI)) and organic dyes (methylene blue and methyl orange). Isothermal studies reveal its large removal capacities of 49.5, 61.7 and 68.2 mg g−1 for chromium(VI), methyl orange and methylene blue, respectively. Kinetic studies reveal that the removal process follows pseudo-second-order adsorption behavior. A mechanism study demonstrates that adsorption, electrostatic interaction and a redox reaction are involved in the pollutant removal process, and contribute to the large adsorption capacities and excellent rate performance. The widely accessible natural resources, low cost, convenient fabrication, and superior adsorption properties would facilitate this new material promising applications in the fields of water pollutant control and purification.

Preparation of high thermal stability polysulfone microcapsules containing lubricant oil and its tribological properties of epoxy composites

Abstract Polysulfone (PSF) microcapsules containing lubricant oil have been successfully prepared using solvent evaporation method. The results show that lubricant oil was successfully encapsulated and the encapsulation capacity of about 56.0 wt.% was achieved. The uniform microcapsules have nearly spherical shape and quite smooth outer surface. The mean diameter is approximately 156 and 169 μm by using different dispersant solutions. The wall material is porous in structure with wall thickness of about 20 μm. The initial decomposition temperature of PSF is 480 °C. It is higher than traditional poly(urea-formaldehyde) (PUF) and poly(melamine-formaldehyde) (PMF) wall materials with 245 °C and 260 °C initial decomposition temperature, respectively. High thermal stability of PSF microcapsules can be considered as additives in high temperature resistant polymer materials. The frictional coefficient and wear rate of epoxy composites decreased significantly by incorporating microcapsules containing lubricant oil into epoxy. When the concentration of microcapsules was 25 wt.%, the frictional coefficient and specific wear rate were reduced by 2.3 and 18.3 times, respectively, as compared to the neat epoxy.

Grafting heteroelement-rich groups on graphene oxide: Tuning polarity and molecular interaction with bio-ionic liquid for enhanced lubrication

Two different heteroelement-rich molecules have been successfully grafted on graphene oxide (GO) sheets which were then used as lubricant additives in bio-ionic liquid. The grafting was processed with reactions between GO sheets and synthesized heteroelement-rich molecules (Imidazol-1-yl phosphonic dichloride and 1H-1,2,4-triazol-1-yl phosphonic dichloride, respectively). The modified GO (m-GO) was added into [Choline][Proline] ([CH][P]) bio-ionic liquid, and has been demonstrated effective additive in promoting lubrication. Different characterization techniques have been utilized to study the reaction between GO and the two modifiers. The effect of molecular structure of the modifiers on the rheological and tribological properties of m-GO/[CH][P] lubricants was systematically investigated. Both theoretical calculation and experimental results demonstrated that the introduced heteroelement-rich groups are beneficial to increase the robustness of lubrication film by intensified hydrogen bonding and enhance the lubricant/friction surface adhesion by increased polarity of the m-GO. As a result, the interfacial lubrication could be significantly improved by these newly developed m-GO/[CH][P] lubricants.