Coating different thickness nickel-boron nanolayers onto boron carbide particles

This work is focused on electroless coating of nickel-boron (Ni-B) onto boron carbide (B4C) particles. Using NiSO4 as Ni2+ source, SnCl2 as sensitizing agent, PdCl2 as activation agent, and NaBH4 as reducing agent, Ni-B nanolayers of different thicknesses have been successfully coated onto the B4C particles. The B4C particles are around 2 mu m in size and the Ni-13 coating thickness can be adjusted by changing the Ni2+:B4C ratio. For the targeted 1 nm Ni-B thickness, the layer is discontinuous. When the targeted Ni-B layer increases to 5 nm, the coating layer becomes continuous and completely covers the B4C particle surfaces. When the targeted Ni-B coating thickness increases to 10 nm or higher, Ni-B nodules start to form with the mesh-like structures between the Ni-B nodules. The Ni-B nodule size increases with the Ni-13 layer thickness. EDS results show the presence of oxygen in the Ni-13 coating; oxygen content decreases as the Ni-13 coating thickness increases. XPS confirms that B2O3 forms in the coating and the Ni:B ratio decreases with the Ni-B layer thickness. Ni-B electroless coating processes and morphological changes on the B4C particle surfaces with different Ni-B coating thickness are analyzed. (C) 2007 Elsevier B.V. All rights reserved.