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For exploring the effect of thiourea on the corrosion resistance of waterborne acrylic resin organic silane composite passivation film on Zn-Al-Mg coating, an aqueous acrylic resin-organosilane was used as the main film-forming material, and different contents of thiourea were added to formulate a chromium-free passivate solution for the composite passivation of Zn-Al-Mg coatings. The particle size of thiourea was measured by Nano ZS90 nanoparticle size analyzer, and the structure of thiourea was tested by Nicolet 6700 Fourier transform infrared spectrometer(FTIR). In addition, the corrosion resistance of the composite passivation film was analyzed through full immersion test, electrochemical test and neutral salt spray test, and the effect of thiourea content on the corrosion rate of the composite passivation film was explored. Results showed that thiourea possessed an inhibitory effect on the corrosion resistance of Zn-Al-Mg coatings, but too much thiourea could lead to a decrease in the corrosion inhibition of the passivation film. Compared with three different addition amounts of thiourea, the corrosion resistance of the Zn-Al-Mg coating was optimal when the mass fraction of thiourea in the passivation solution was 0.5%. Furthermore, thiourea and waterborne acrylic resin organic silane underwent cross-linking, and after corrosion, they formed a complex with metals, forming a dense network structure, which improved the density of the film layer and reduced the corrosion rate of the film layer.

The chromium-free passivation liquid composed of micro-nano α-Al2O3 modified acrylic resin-organosilane was applied to the surface of the stainless steel substrate, for exploring the impact of the micro-nano α-Al2O3 passivation film formed on the surface of the stainless steel on the surface properties of the stainless steel. The surface characteristics of the substrate through surface hardness testing and scanning electron microscopy testing were analyzed. Meanwhile, the bonding strength of the coating and the corrosion resistance of the substrate were explored through coating adhesion test and electrochemical test. Results showed that the chromium-free passivation liquid modified by micro-nano α-Al2O3 significantly improved the corrosion resistance of stainless steel plates, and the surface hardness was increased by 80%.

This paper aims at preparing UV-curable coatings for hot-dip aluminum-zinc coated steel plates.Using trimethylolpropane triacrylate (TMPTA) and 2-phenoxyethyl acrylate as active diluents,the mixture of modified epoxy acrylate and modified polyester acrylate in a certain proportion as the oligomer,2-methyl-1-[4-(methylthio)benzene]-2-morpholinacetone (907) as the free radical photoinitiator,and isopropyl thioxanthone (ITX) as the sensitizer,the free radical light curing agent formula was compounded using high pressure mercury lamp as radiation source.The as-obtained light curing agent was coated on the surface of hot-dip aluminum-zinc coated steel plate.After curing treatment,the passivation film was characterized by neutral salt spray testing,electrochemical testing and other means.Results showed that the passivation films of this system could be cured at an energy of 600 mJ/cm2,and their general performance and resistance to neutral salt spray test (NSST) were able to meet the basic requirements of downstream users of hot-dip aluminum-zinc coated steel plate.

In recent years, atmospheric composite pollution has become increasingly serious, and accelerating VOC governance has become the focus of and difficulty in atmospheric governance. Volatile organic compounds (VOCs) come from a wide range of sources, and industrial sources are the main source of anthropogenic VOC emissions in China. Chemicals, oil refining, and solvents are three typical VOC-emitting industries, and their control is an important part of accelerating and optimizing VOC governance. It can be controlled by source control, process control, and pipe end treatment; among these, pipe end treatment is divided into recovery technology and destruction technology. In pipeline end treatment, with the key materials of adsorption, absorption, catalytic oxidation, and catalytic combustion, the research and development of adsorbents, absorbents and catalysts has become a hot spot in recent years. This paper summarizes the chemical materials used in typical VOC pipe end-treatment technology (including adsorbents used in the adsorption method, absorbents used in the adsorption method, and catalysts used in the catalytic oxidation and catalytic combustion methods), summarizes the advantages and disadvantages of various materials and their application range, and looks forward to the direction of future developments. [ABSTRACT FROM AUTHOR]

Polyurethane (PU)/Al-graphene composite coating with low infrared emissivity, a low near-infrared reflectivity of 1.06 μm, and satisfactory mechanical properties was prepared by using Al powder and graphene as composite pigments and PU as a binder, respectively. The study investigated the impact of the mass ratio of graphene to Al powder, as well as the total addition of functional fillers (Al powder and graphene), on infrared emissivity and near-infrared reflectivity, and the mechanical properties of the coating were studied. The results show that a large number of conjugated systems in the molecular structure of graphene can produce strong absorption of near-infrared radiation, allowing for the coating to exhibit low reflectivity at 1.06 μm in near-infrared radiation. The flake Al powder, with good electrical conductivity, can create a strong reflection in the 8–14 μm far-infrared radiation range, resulting in low emissivity and providing the coating with good infrared and laser-compatible stealth performance. By adjusting the mass ratio of graphene to Al powder, the infrared emissivity at 8–14 μm can be tuned from 0.371 to 0.644, and the reflectivity at 1.06 μm can be adjusted from 22.9% to 61.6%. Additionally, the coatings demonstrate satisfactory mechanical properties, with adhesion strength, flexibility, and impact strength reaching grade 1, 2 mm, and 50 kg·cm, respectively, for coatings with different mass ratios of graphene to Al powder. The PU/Al-graphene composite coating can be regarded as a new type of infrared and laser compatible stealth coating with good functional and mechanical properties. [ABSTRACT FROM AUTHOR]

In this paper, we theoretically study the achievable capacity of orthogonal and non-orthogonal multiple access (OMA and NOMA) schemes in supporting downlink satellite communication networks. Considering that various satellite applications have different delay quality-of-service (QoS) requirements, the concept of effective capacity is introduced as a delay-guaranteed capacity metric to represent users' various delay requirements. Specifically, the analytical expressions of effective capacities for each user achieved with the NOMA and OMA schemes are first studied. Then, approximated effective capacities achieved in some special cases, exact closed-form expressions of users' achievable effective capacity, and the capacity difference between NOMA and OMA schemes are derived. Simulation results are finally provided to validate the theoretical analysis and show the suitable limitations of the NOMA and OMA schemes, such as the NOMA scheme is more suitable for users with better channel quality when transmit signal-to-noise (SNR) is relatively large, while it is suitable for users with worse link gain when transmit SNR is relatively small. Moreover, the influences of delay requirements and key parameters on user selection strategy and system performance are also shown in the simulations. [ABSTRACT FROM AUTHOR]

The exploration of inexpensive and stable heterogeneous catalysts for C–S coupling reactions remains a challenging issue. Herein, we successfully prepared a new biomass-derived copper catalyst and applied it to the selective C(sp3)–H-directed sulfonylation of ketone hydrazones with commercial sodium sulfinates. The catalyst was characterized using different spectroscopic and microscopic techniques. Importantly, the prepared biomass-supported Cu catalyst catalyzed the C–S coupling reaction with considerably high activity. A variety of aryl and alkyl sulfinates were converted to the corresponding sulfones with good yields. In particular, the heterogeneous catalyst could be recovered easily after the synthesis and consecutively used at least five times with no appreciable decrease in the catalytic activity. Lastly, the copper catalyst is expected to have further applications in organic reactions catalyzed by Cu/CuO2. [ABSTRACT FROM AUTHOR]