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  • Wiley  (2)
  • Chen, Yanqiu  (2)
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  • Wiley  (2)
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  • 1
    In: ChemistrySelect, Wiley, Vol. 5, No. 4 ( 2020-01-31), p. 1552-1559
    Abstract: Cr−Zr bimetallic phosphates catalysts were prepared by sol‐gel method and used in the oxidation of cyclohexane, ethylbenzene and cyclohexene, respectively. The catalysts were characterized by a variety of analytical techniques. The results show that chromium ions enter the framework of mesoporous zirconium phosphate, Cr−Zr phosphates catalysts with molar ratio of Cr: Zr=2 (CrZr 2 P) or Cr: Zr=1 (CrZrP) still retain the mesoporous structure and form composite metal phosphates. Two active centers‐ redox (Cr 6+ ) and acidic sites in these bimetallic phosphates play a synergistic catalytic role in the oxidation of C−H bond. Catalytic activity is closely related to the amount of acid or acid strength, the C=O product selectivity depends on the amount and high dispersion of Cr 6+ species. Acidic sites and redox sites are affected by different molar ratios of chromium/ zirconium. Among the Cr−Zr phosphates catalysts, CrZr 2 P and CrZrP catalysts show excellent activity, just because the formation of mesoporous structure leads to the uniform dispersion of acidic and redox sites.
    Type of Medium: Online Resource
    ISSN: 2365-6549 , 2365-6549
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2020
    detail.hit.zdb_id: 2844262-3
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  • 2
    In: Advanced Engineering Materials, Wiley, Vol. 21, No. 5 ( 2019-05)
    Abstract: Despite of the outstanding chemical‐resistance, thermal and thermomechanical properties, and dielectric performance of three dimensional (3D) printed polyimides, the high dimensional shrinkage (more than 45%) between the as‐printed and final imidized objects may become the biggest obstacle on its practical applications. In this work, the authors present a two‐state curing strategy for realizing 3D printing of high performance polyimides via UV‐assisted direct ink writing (DIW) of poly (amide acid) (PAA) followed by thermal imidization. More specifically, PAA precursors modified with hydroxyethyl methacrylate are printed and thermally imidized at an elevated temperature to form 3D objects, which demonstrate a dimensional shrinkage less than 6%. The outstanding performances regarding thermal resistance, solvent‐proofing, and mechanical strength are comprehensively characterized, and some attracting polyimide functional 3D devices, such as polyimide spring and enameled wire, are readily achieved. Their DIW strategy realizes three‐dimensional polyimide architectures with low volume shrinkage and provides a tremendous potential for 3D printing of polyimides in many fields including aerospace, automobile, microelectronics, and engineering.
    Type of Medium: Online Resource
    ISSN: 1438-1656 , 1527-2648
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 2016980-2
    detail.hit.zdb_id: 1496512-4
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