The structural evolution of hollow boehmite particles induced by citric acid

• Published in: Materials letters 2013-03, Vol.95, p.9-12
• Main Authors: Han, Qiang, Wu, Xiaofeng, Liao, Yuchao, Li, Dan, Yue, Renliang, Liu, Haidi, Chen, Yunfa
• Format: Article
• Language: English
• Subjects: aluminum; Boehmite; chelation; Citric acid; heat; Microstructure; Nanoparticles; nitrates; scanning electron microscopy; Structural; Surfaces; transmission electron microscopy; urea; X-radiation; X-ray diffraction
• ISSN: 0167-577X; 1873-4979
• DOI: 10.1016/j.matlet.2012.12.065

Spherical boehmite particles with hollow interiors were synthesized in the hydrothermal condition using aluminum nitrate as Al3+ source, urea as precipitator and citric acid as structure directing agent, which was further transformed to hollow γ-Al2O3 products after simply heating post-treatment under 700°C for 4h. The crystal phase, morphologies and microstructure of the sample were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. It is suggested that the as-synthesized boehmite powder possesses hollow interior with ca.1μm in diameter and shells with 100nm in thickness, and the calcinated sample have γ crystal phase without morphological changes after heat post-treatment. The interesting hollow structure evolution was further investigated by comparative experiments and a reasonable evolution mechanism was proposed, in which the chelation of citric acid with Al3+ species and the dissolution of boehmite play the critical role in forming the hollow structure of boehmite.