Characterization and tribological investigation of Al 2 O 3 and modified Al 2 O 3 sol-gel films Wenguang Zhang*, Weimin Liu, Qunji Xue State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, P.R. China (Refereed) Received 24 March 2000; accepted 17 August 2000 Abstract Thin films of Al 2 O 3 and modified Al 2 O 3 were prepared on a glass substrate by a dip-coating process from specially formulated aqueous sols. The tribological properties of the as-prepared thin films sliding against an Si 3 N 4 ball were evaluated on a one-way reciprocating friction and wear tester. The worn surface morphologies and chemical compositions of the films were examined by means of atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS), respectively. Thermogravimetric analysis (TGA) and differential scanning cal- orimetric analysis (DSC) of dried sols were performed to explore the thermal events occurring during the annealing process of the sol-gel Al 2 O 3 films. The wear mechanisms of the films are discussed based on SEM observation of the worn surface morphologies. As the results, modified sol-gel Al 2 O 3 films are of higher wear resistance than the unmodified one. Meanwhile, the wear life of the modified films is correlated to the additive amount in the starting aqueous sol. In other words, the higher the additive amount in the starting aqueous gel, the longer the wear life of the sol-gel Al 2 O 3 film. SEM observation of the morphologies of worn film surfaces indicates that wear of glass is characteristic of brittle fracture and severe abrasion. Wear of unmodified Al 2 O 3 film is dominated by microfracture and abrasion, while that of modified films by plastic deformation and/or microcracking. © 2001 Elsevier Science Ltd. All rights reserved. Keywords: A. Thin films; A. Oxides; B. Sol-gel chemistry; D. Mechanical properties; D. Surface properties 1. Introduction There have been many investigations of oxide films derived from the sol-gel method because of several advantages, such as low processing temperature, homogeneity, the * Corresponding author. Fax: +86-931-8277088. E-mail address: LSL@ns.LZb.ac.cn (W. Zhang). Pergamon Materials Research Bulletin 36 (2001) 1903–1914 0025-5408/01/$ – see front matter © 2001 Elsevier Science Ltd. All rights reserved. PII: S0025-5408(01)00673-0