Table 2: Design parameters and their levels.

Design factors UnitLevels
1 2 3

Bath temperature ( ) °C 85 90a95
Reducer concentration ( ) (g/L) 0.6 0.8a1.0
Nickel source concentration ( ) (g/L) 15 20a25
Annealing temperature ( ) °C 250 350a450

a: initial condition.