Fabrication and Characterization of Nickel Microtubes through Electroforming: Deposition Optimization Using Evolutionary Algorithms

The present work involves the fabrication of microtubes through the process of pulse electroforming by employing an in-house-developed micro-electroforming equipment. Theoretical modeling and simulation have demonstrated the role of cathode rotation and pulse waveform in ensuring uniformity of deposition. Nickel microtubes having wall thickness in the range of 8-144 µm have been successfully produced by varying the input parameters, viz. duty cycle and time of deposition. The fabricated micro-tubes have also been tested for their structural and mechanical characterization with the help of FESEM, EDAX, XRD, hardness testing, and surface roughness measurements. The electroformed Ni microtubes exhibit well aligned growth in the <111> direction with minimum crystallite size of 14 nm. The result demonstrates relation among duty cycle, crystallite size and hardness of the tubes. Moreover, the formulation of a multi-objective function and optimization utilizing two evolutionary algorithms, i.e., genetic algorithms and particle swarm optimization, are accomplished. An optimized parameter of 8 hours deposition time and 38.7% duty cycle is recommended. The results show the electroformed Ni tubes to possess geometries in microscale and crystallite size in nanoscale resulting in high hardness and good rigidity.