Structural state of electroless nickel–boron deposits (5 wt.% B): Characterization by XRD and TEM

The structure of electroless nickel–boron with a boron content around 5 wt.% was investigated in the as deposited and heat treated states by X-ray diffraction and by transmission electron microscopy on thinned cross-sections prepared by focused ion beam technique.In the as-deposited state, the presence of areas with short range order has been observed. This shows that electroless nickel–boron coatings with high boron content are not fully amorphous, as is usually stated.After heat treatment, the structure of electroless nickel–boron appeared constituted of nanocrystalline nickel–boride Ni3B.

► TEM has been carried out on nickel–boron samples prepared by the FIB lift-out method.
► Evidence of short range order has been found in 5 wt.% nickel–boron.
► Ordered zones are large and follow a wavy pattern reminiscent previous of sample-bath interface.
► Crystallization during heat treatment occurs preferentially in former ordered zones.
► Arrangement of nano sized grains after heat treatment follow previous wavy pattern.