Studies of electroless Ni-Co-P ternary alloy on glass fibers

Electroless Ni-Co-P alloys on glass fibers with sodium hypophophite as a reducing agent and sodium citrate as a complexing agent in an alkaline bath was studied. A kind of silane coupling agent was used during its pretreatmeat. Plating rate was determined by measuring the weight of glass fibers after plating. The effect of deposition parameters, such as mole ratios of CoSO₄/(CoSO₄ + NiSO₄) and pH, on the composition and the plating rate of the deposits were examined. The crystallization behavior of Ni-Co-P alloys was studied by using differential scanning colorimetry (DSC) and X-ray diffraction (XRD). It was found that all of the three exothermic peaks in DSC curves alter distinctly as the mole ratios of CoSO₄/(CoSO₄ + NiSO₄) increase. When the concentration of sodium hypophophite is not below 16 g l^{- 1} in the plating bath, the structure of the as-plated Ni-Co-P alloys plated at all conditions is amorphous. The deposit transformed into Ni₅P₂ and Ni₁₂P₅ phase after heat treatment at 300 °C and 420 °C, but they disappear and stable Ni₃P appeared after sintering at 480 °C.