Lianhe Liu

Underwater Drag-Reducing Effect of Superhydrophobic Submarine Model

To address the debates on whether superhydrophobic coatings can reduce fluid drag for underwater motions, we have achieved an underwater drag-reducing effect of large superhydrophobic submarine models with a feature size of 3.5 cm × 3.7 cm × 33.0 cm through sailing experiments of submarine models, modified with and without superhydrophobic surface under similar power supply and experimental conditions. The drag reduction rate reached as high as 15%. The fabrication of superhydrophobic coatings on a large area of submarine model surfaces was realized by immobilizing hydrophobic copper particles onto a precross-linked polydimethylsiloxane (PDMS) surface. The pre-cross-linking time was optimized at 20 min to obtain good superhydrophobicity for the underwater drag reduction effect by investigating the effect of pre-cross-linking on surface wettability and water adhesive property. We do believe that superhydrophobic coatings may provide a promising application in the field of drag-reducing of vehicle motions on or under the water surface.

A bio-inspired nacre-like layered hybrid structure of calcium carbonate under the control of carboxyl graphene

In this paper, carboxyl graphene (GO-COOH) sheet matrices, which are heavily oxygenated and are similar to the organic matrices of molluscs, were used to construct nacre-like layered structures. The results showed that the surface of the hybrids was smooth and the cross section had a multilayer structure. Both the surface and the interlayer of the composite material generated calcium carbonate (CaCO3) crystals. Furthermore, the spontaneity of the layered structure was found to be closely related to the concentration of the CaCO3 crystals in which high concentration could inhibit the process, highlighting the determining role of the CaCO3 concentration. To better understand the mechanisms for the formation of the layered structure, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Fourier transform infrared spectrometry (FT-IR) were employed. This work presents an efficient and controllable way to construct nacre-like layered hybrid structures and also has great potential for promoting the application of GO-COOH in biomedical engineering, especially in the field of biomimetic materials.

Hierarchically structured layered-double-hydroxides derived by ZIF-67 for uranium recovery from simulated seawater

Under the background of increasing and sustainable development of nuclear industry, it is significant to develop materials with high adsorption capacity and high selectivity of uranium as adsorbents. In this work, novel Mg-Co layered-double-hydroxide (LDH) with hierarchical structure was synthesized successfully via self-sacrifice template by ZIF-67. X-ray diffraction (XRD) technique, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller surface area measurement (BET) and X-ray photoelectron spectroscopy (XPS) characterization were conducted, which confirmed the specifically hollow structured material possesses high surface area and abundant mesopores that makes uranium ions diffuse into it more easily. In typical batch adsorption experiments, varieties of parameters were investigated in details. In addition, adsorption of trace concentration of uranium (ppb level) in simulated seawater was also studied. The results showed as-prepared Mg-Co LDHs are promising adsorbents for extraction of uranium from simulated seawater.

Catalytic effect of CuO nanoplates, a graphene (G)/CuO nanocomposite and an Al/G/CuO composite on the thermal decomposition of ammonium perchlorate

Tenorite CuO nanoplates, a graphene (G)/CuO nanocomposite and an Al/G/CuO composites were investigated in this paper as potential catalysts for the thermal decomposition of ammonium perchlorate (AP); the most common oxidant used in composite propellant formulations. Tenorite CuO nanoplates and the G/CuO nanocomposite were successfully obtained by a facile hydrothermal method; the Al/G/CuO composite was prepared using physical mixing of the G/CuO nanocomposite and aluminum powder with sonication and dispersion. The catalytic activity of these materials was investigated by thermogravimetric (TG) and differential thermal analysis (DTA). The results of DTA indicated that the three materials ameliorate the thermal decomposition of AP, especially the G/CuO nanocomposite and Al/G/CuO composite, where the high temperature decomposition (HTD) of AP decreases from 432 °C to 325 °C and 315 °C, respectively. Significant decrease in activation energy (Ea) (from 129 kJ mol−1 to 71.47 kJ mol−1 and 56.18 kJ mol−1) was also achieved in the presence of these two materials, showing their strong catalytic activity on the thermal decomposition of ammonium perchlorate.

High damping and mechanical properties of hydrogen-bonded polyethylene materials with variable contents of hydroxyls: Effect of hydrogen bonding density

Hydrogen bonding is considered to have significant effect on the interaction between polymeric chains and on the viscoelasticity of the polymeric materials. In this paper, we attempt to discuss the relationship between hydrogen bonding density and damping behavior and mechanical properties of polyethylene-based polymeric materials. For this reason, a series of pendant chain hydrogen bonding polymers (PCHBP) with different hydrogen bonding density (HBD) were prepared by quantitatively changing the content of pendent hydroxyl groups on the main chain of polyethylene. It was found that PCHBP with low HBD showed similar properties to polyethylene, indicating that the property of the materials was dependent mainly on the structure of the main chain. However, PCHBP with high HBD exhibited two tanδ peaks and a platform of loss modulus as well as a high storage modulus (about 400 MPa) at the second tanδ peak temperature, demonstrating that a polymeric material with high strength and damping properties was obtained. More importantly, the maximum of loss modulus showed a linear increase with the HBD, indicating that a higher HBD greatly improved the damping properties of the polymeric materials.

Synthesis of zinc-based acrylate copolymers and their marine antifouling application

Marine fouling organisms have caused inconvenience to humans for a long time owing to their high vitality and great destructiveness. Self-polishing antifouling coatings are considered to be among the most effective antifouling technologies. In this study, zinc-based acrylate copolymers (ZnPs) were designed and synthesized using a bifunctional zinc acrylate monomer (ZnM) as a new self-polishing monomer, and three acrylate monomers (namely, methyl methacrylate, ethyl acrylate and 2-methoxyethyl acrylate) were used as comonomers. ZnPs that contained the new ZnM were characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy and gel permeation chromatography. Different antifouling coatings were prepared using the previously mentioned ZnPs as the matrix material, and their erosion properties were investigated using a lab rotor test. A field test of the prepared coatings at various geographical locations showed their excellent antifouling performance as they inhibited the settlement of barnacles in both the South China Sea for 9 months and in the Yellow Sea for at least 15 months. The results of this study highlight that the biocidal ZnP-based coatings are highly promising candidates for marine antifouling applications.

Synthesis of hybrid zinc/silyl acrylate copolymers and their surface properties in the microfouling stage

Development of an environmentally friendly and efficient marine antifouling coating is a central goal in marine antifouling. In this study, a series of novel hybrid zinc/silyl acrylate copolymers (Zn/Si-acrylate copolymers) composed of tri(isopropyl)silyl acrylate (TIPSA), zinc-2-ethylhexanoate methacrylate (Zn-monomer), ethyl acrylate and methyl methacrylate were synthesized and their surface compositions, thermal degradation and hydrolysis properties were investigated. After being immersed in seawater, the hydrolysis of TIPSA and Zn-monomer could lead to a gradual self-peeling of the Zn/Si-acrylate surfaces, which was controlled by the ratio of TIPSA to Zn-monomer. The Zn/Si-acrylate copolymers with high Zn-monomer content showed excellent performance in the resistance of diatom Phaeodactylum tricornutum (P. tricornutum) growth on the Zn/Si-acrylate films. Both the self-peeling and release of zinc compounds lead to antifouling properties, which demonstrated that Zn/Si-acrylate copolymers were an effective resin for marine antifouling in static or low flow conditions.

Application of Chemical Doping and Architectural Design Principles To Fabricate Nanowire Co2Ni3ZnO8 Arrays for Aqueous Asymmetric Supercapacitors

Electrode materials derived from transition metal oxides have a serious problem of low electron transfer rate, which restricts their practical application. However, chemically doped graphene transforms the chemical bonding configuration to enhance electron transfer rate and, therefore, facilitates the successful fabrication of Co2Ni3ZnO8 nanowire arrays. In addition, the Co2Ni3ZnO8 electrode materials, considered as Ni and Zn ions doped into Co3O4, have a high electron transfer rate and electrochemical response capability, because the doping increases the degree of crystal defect and reaction of Co/Ni ions with the electrolyte. Hence, the Co2Ni3ZnO8 electrode exhibits a high rate property and excellent electrochemical cycle stability, as determined by electrochemical analysis of the relationship between specific capacitance, IR drop, Coulomb efficiency, and different current densities. From the results of a three-electrode system of electrochemical measurement, the Co2Ni3ZnO8 electrode demonstrates a specific capacitance of 1115 F g(-1) and retains 89.9% capacitance after 2000 cycles at a current density of 4 A g(-1). The energy density of the asymmetric supercapacitor (AC//Co2Ni3ZnO8) is 54.04 W h kg(-1) at the power density of 3200 W kg(-1).

Hierarchical flower like double-layer superhydrophobic films fabricated on AZ31 for corrosion protection and self-cleaning

A stable double-layer superhydrophobic surface was successfully constructed on a magnesium alloy substrate by using a two-step immersion coating method to enhance corrosion resistance. The as-prepared surface had a static water contact angle measured as 160°. The microscopy and chemical composition analysis of the surface were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FI-IR), respectively. Importantly, the as-prepared superhydrophobic surface exhibited good stability and good corrosion resistance performance. In addition, the property of self-cleaning was investigated by using chalk powders. From our study, the superhydrophobic coatings could easily be applied to other materials.

High impact resistance epoxy resins by incorporation of quadruply hydrogen bonded supramolecular polymers

A bisphenol A based epoxy was incorporated with a quadruply hydrogen bonded supramolecular polymer as a toughening agent to prepare a composite epoxy resin with higher impact resistance. The supramolecular polymer comprising poly-(propylene glycol) bis(2-aminopropyl) ether chains and 2-ureido-4[1H]-pyrimidinone moieties (UPy) self-assembled into spherical domains with sizes of 300 nm to 600 nm in diameter by micro phase separation in bulk epoxy matrixes. A significant improvement of 300% in impact resistance of the supramolecular polymer incorporated epoxy resin was obtained when the content of supramolecular polymer was 10 wt%. Tensile tests showed that the mechanical properties of the modified epoxy resin containing the hydrogen-bonded supramolecular polymers are also improved compared with those of the neat epoxy resin.