X-ray diffraction studies on the relative proportion and decomposition of amorphous phase in electroless NiB deposits

Abstract

Electroless nickel-boron deposits with 2.34, 3.85 and 4.32 wt.% boron were produced on mild steel substrates. The deposits had a structure consisting of a mixture of microcrystalline nickel and amorphous NiB phases in the as deposited condition. From the ratios of the integrated intensities of the X-ray diffraction profiles of amorphous and crystalline phases, the relative proportion of the two phases was estimated. The quantity of amorphous phase increased with increasing boron content. The amorphous phase decomposed in one single step as Ni+Ni 3B at around 523K. There are indications that boron might be diffusing out of the crystalline phase into the amorphous phase just prior to the decomposition of the amorphous phase.