Nickel microspheres have been prepared by a hydrothermal process with a template of triblock copolymer HO(CH₂CH₂O)₂₀(CH₂CH(CH₃)O)₇₀(CH₂CH₂O)₂₀H (P123) and a reductant of sodium hy-pophosphite. The prepared products were characterized with X-ray diffraction (XRD), scanning electron mi-croscopy (SEM) and vibrating sample magnetometer (VSM). Results show that the nickel microspheres are composed of nickel nanocrystals, and at least a part of them possess hollow structures. The size of the mi-crospheres decreases with an increase in pH value of the precursor solution, and their aggregation degree to form chainlike assemblies rises with the elevation of temperature. Two kinds of microspheres prepared at 120 and 220 ℃ have diameter ranges of 1.5～4.5 and 0.8～4.5 μm, and consist of nanocrystals with aver-age sizes of 16.0 and 14.2 nm, and their coercivities are 91.5 and 66.1 Oe, respectively.

Key words: nickel microsphere, block polymer, hydrothermal process