Yang Li,Chunting Guo,Caixia Qi,Dejian Zhang,Huilai Sun,Shuyan Yang,Yong Wan,Yanshuang Wang
Although the formation of plasma electrolytic oxidation (PEO) coatings on aluminum alloys can significantly enhance their service life, they may still suffer from corrosion damage when exposed to harsh environments with strong corrosivity for a long time. In this work, chitosan (CS) was dissolved in four acids, i.e. hydrochloric acid (HCl), citric acid (CA), lactic acid (LA), and acetic acid (HAc), and deposited onto the PEO-coated 5052 aluminum alloy using dip coating method. Scanning electron microscope (SEM), energy dispersive spectrometer (EDS), atomic force microscope (AFM), contact angle (CA) meter, grazing incidence X-ray diffraction (GIXRD), Fourier transform infrared spectrometer (FTIR), and electrochemical workstation system were used to explore the enhancement of the corrosion resistance of PEO-coated 5052 aluminum alloy by application of CS film prepared in different solvent acids. The results showed that the interactions between chitosan and acid ions affects the uniformity, hydrophobicity , thickness and surface roughness of the CS/PEO coating. The HAc-CS/PEO coating had the lowest surface roughness of 32.4 ± 3.9 nm, the largest contact angle of 85.7 ± 2.0°, and the thickest CS film of 20 μm, which significantly improved corrosion resistance of PEO-coated aluminum alloy.
Four novel choline carboxylate aqueous solution systems were developed by mixing H2O with choline nicotinate [Ch][Na], choline ferulate [Ch][Fa], choline vanillate [Ch][Va] and choline syringate [Ch][Sa]. The solubility of lignin in the four solvents was determined at 25 °C. The influence of the molar ratio of H2O to [Ch][Na] ([Ch][Fa], [Ch][Va] and [Ch][Sa]) and the anionic structure on lignin solubility were systematically investigated. It was found that, the anionic structure and H2O content significantly affected lignin dissolution. Interestingly, H2O/[Ch][Na] and H2O/[Ch][Fa] solvents show efficient capacity for lignin dissolution even at room temperatures. The dissolution of lignin in H2O/[Ch][Na] and H2O/[Ch][Fa] solvents is mainly ascribed to the interaction of lignin with the alkyl chain in the anion and cation dissociated from [Ch][Na]([Ch][Fa]) by H2O. In addition, the recycling of the lignin solvent was examined, and the structure and thermostability of the lignin regenerated from the solvent were also estimated.Keywords:lignin;H2O/choline carboxylate solvent;dissolution mechanism;recycling;regenerated lignin properties
危险品化学品经营许可证（带存储）