Influence of Ultrasonic Energy on Pore Structure of Ni-P Ultra-Black Films Produced by a Novel Blackening Process

Abstract

Ni-P ultra-black films were prepared by ultrasonic chemical etching of electroless plated Ni-P films using 8 mol/L nitric acid at 40 °C for 20 s with different ultrasonic power ranging from 0 to 195 W. Scanning electron microscopy (SEM) was used to study topographic characteristics of the films. The results show that ultrasonic oscillation plays an important role during ultrasonic chemical etching of electroless plated Ni-P films. The enhanced pore features with higher porosity through coalescence of adjacent isolated pores have been observed at 0-105 W. The increase in pore size of Ni-P etched films with the ultrasonic power (from 105 to 195 W) has been confirmed by SEM characterization. Generally, the dependences of relative etching rate on ultrasonic power are closely associated with pore size, pore shape and the distribution of etching pores.