The hydrolysis behavior of ZrB2 powder during attrition milling was studied in de-ionized water and ethanol. Surface characterization, thermal analysis, chemical analysis and electron microscopy were utilized to analyze the surface properties of as-milled powders. The results proved that the surface of ZrB2 powder was mainly composed of Zr-O, B-O and B-OH bonds as hydrolysis proceeded, and the amount of surface B-O bond was found to increase rapidly in water, suggesting a more B2O3-like surface behavior were developed. Results also showed when milled at 300 rpm for 4 h in water, 64.45 at% of B was in the form of B2O3 at a thickness of similar to 3 nm from the surface. The nano-sized surface Zr-B-O oxide layer (similar to 5 nm in thickness) could help to improve the dispersion of powder in aqueous media. (C) 2012 Published by Elsevier B.V.