Hexagonal and triangular monodisperse Fe3O4 nanosheets have been synthesized via a two-step microemulsion solvothermal approach in which uniform Fe3O4 nanoparticles are first prepared and then these hydrophobic nanocr...Hexagonal and triangular monodisperse Fe3O4 nanosheets have been synthesized via a two-step microemulsion solvothermal approach in which uniform Fe3O4 nanoparticles are first prepared and then these hydrophobic nanocrystals are dispersed in a uniform microemulsion environment as ＂seeds＂ for further re-growth through a secondary solvothermal process. The growth of anisotropic morphologies has been explained by the presence and orientation of twin planes in the face-centered cubic Fe3O4 which direct the shape of the growing particles. In particular, reentrant grooves resulting from twin planes are favorable sites for the addition of adatoms, leading to anisotropic growth. Triangular nanosheets are believed to contain one twin face which directs the growth of the primary particles in two dimensions. Hexagonal nanosheets are believed to contain two parallel planes that allow the growth edges to regenerate one another. The growth mechanism is evidenced by the analysis of high-resolution transmission electron microscopy （HRTEM） results and the as-prepared Fe3O4 nanoparticles have been shown to be an effective catalyst in the synthesis of quinoxaline.展开更多
Self-healing polyurethane(PU)faces aging deterioration due to active dynamic bonds,which remain a challenging predicament for practical use.In this work,a novel strategy is developed to address this predicament by lev...Self-healing polyurethane(PU)faces aging deterioration due to active dynamic bonds,which remain a challenging predicament for practical use.In this work,a novel strategy is developed to address this predicament by leveraging the hydrophobicity and gas barrier of hydrogenated hydroxyl-terminated polybutadiene(HHPB).The dynamic oxime-carbamate bonds derived from 2,4-pentanedione dioxime(PDO)enable the elastomer to exhibit surface self-repairability upon applied mild heat and achieve~99.5%mechanical self-healing efficiency.The mechanical properties remained nearly intact after 30-d exposure to thermal oxidation,xenon lamp,acids,bases,and salts.Gas permeability,positron annihilation lifetime spectroscopy(PALS),and contact angle measurements reveal the pivotal role of gas barrier,free volume,and hydrophobicity in blocking undesirable molecules and ions which effectively protects the elastomer from deterioration.HHPB-PU also exhibits excellent adhesion to steel substrate.The shear strength achieves(3.02±0.42)MPa after heating at 80°C for 4 h,and(3.06±0.2)MPa after heating at 130°C for 0.5 h.Regarding its outstanding anti-corrosive and weatherproof performances,this self-healable elastomer is a promising candidate in surface-protective applications.展开更多
基金This work was supported by the National Natural Science Foundation ol： China （Nos. 20901069, 50873093, and 21271156） and the Henan Province Scientific and Technological Research Program （No. 092102210054）.
文摘Hexagonal and triangular monodisperse Fe3O4 nanosheets have been synthesized via a two-step microemulsion solvothermal approach in which uniform Fe3O4 nanoparticles are first prepared and then these hydrophobic nanocrystals are dispersed in a uniform microemulsion environment as ＂seeds＂ for further re-growth through a secondary solvothermal process. The growth of anisotropic morphologies has been explained by the presence and orientation of twin planes in the face-centered cubic Fe3O4 which direct the shape of the growing particles. In particular, reentrant grooves resulting from twin planes are favorable sites for the addition of adatoms, leading to anisotropic growth. Triangular nanosheets are believed to contain one twin face which directs the growth of the primary particles in two dimensions. Hexagonal nanosheets are believed to contain two parallel planes that allow the growth edges to regenerate one another. The growth mechanism is evidenced by the analysis of high-resolution transmission electron microscopy （HRTEM） results and the as-prepared Fe3O4 nanoparticles have been shown to be an effective catalyst in the synthesis of quinoxaline.
基金funded by China Postdoctoral Science Foundation(Grant No.2019M652572)and Zhengzhou Major Collaborative Innovation Project(Zhegzhou University,Grant No.18XTZX12001).
文摘Self-healing polyurethane(PU)faces aging deterioration due to active dynamic bonds,which remain a challenging predicament for practical use.In this work,a novel strategy is developed to address this predicament by leveraging the hydrophobicity and gas barrier of hydrogenated hydroxyl-terminated polybutadiene(HHPB).The dynamic oxime-carbamate bonds derived from 2,4-pentanedione dioxime(PDO)enable the elastomer to exhibit surface self-repairability upon applied mild heat and achieve~99.5%mechanical self-healing efficiency.The mechanical properties remained nearly intact after 30-d exposure to thermal oxidation,xenon lamp,acids,bases,and salts.Gas permeability,positron annihilation lifetime spectroscopy(PALS),and contact angle measurements reveal the pivotal role of gas barrier,free volume,and hydrophobicity in blocking undesirable molecules and ions which effectively protects the elastomer from deterioration.HHPB-PU also exhibits excellent adhesion to steel substrate.The shear strength achieves(3.02±0.42)MPa after heating at 80°C for 4 h,and(3.06±0.2)MPa after heating at 130°C for 0.5 h.Regarding its outstanding anti-corrosive and weatherproof performances,this self-healable elastomer is a promising candidate in surface-protective applications.
