E.A. Pavlatou, M. Raptakis, N. Spyrellis
Surface & Coatings Technology (2007), 201, 4571-4577
Nanocrystalline nickel deposits were produced by applying both direct current (DC) and pulse current electroplating (PC) from an additive-free Watts type bath and in the presence of 2-butyne-1,4-diol (BD). The surface morphology, the preferred orientation, the grain size and the microhardness of the deposits were investigated. Under DC conditions, the addition of BD enhanced the perfection of [100] preferred crystal orientation and promoted a considerable grain refinement. The application of PC technique in presence of small amount of BD (CBD=0.25 mmolL−1) accelerated the textural modification from [100] to [211] with respect to DC conditions and deposits with grain size of 20–60nm were produced. A significant enhancement of microhardness of the produced bright deposits was observed compared to those deposits prepared under DC regime, which could be correlated to the observed crystal orientation mode [211], as well as to the corresponding nanosized crystallites. Progressive addition of BD promoted a peculiar textural modification from [211] to [100] and a possible mechanism of action of BD is proposed taking into account as inhibiting species of the Ni crystal growth not only Ni(OH)2, but also cis-butene-1,4 diol.