This study is focused on reduction of Ni(2)O(3) and B(2)O(3) in the Ni-B nanolayer on B(4)C particle surfaces and understanding of the nanolayer composition and morphology changes. Initially, the nanolayer contains Ni(2)O(3), B(2)O(3), and amorphous boron. After 400 degrees C thermal treatment in a H(2)-Ar atmosphere, Ni(2)O(3) is reduced to nickel; the nanolayer morphology is maintained and the coated particles demonstrate magnetism. As the thermal treatment temperature is increased to 550 degrees C, B(2)O(3) is reduced to boron, which reacts with nickel and forms Ni(2)B. Simultaneously, the nanolayer evolves into nanoparticles. Thermal treatment temperature increase to 700-900 degrees C only causes Ni(2)B particle growth but does not fundamentally change the composition or phase. (C) 2009 Elsevier B.V. All rights reserved.