|
| Design factors | Unit | Levels |
| 1 | 2 | 3 |
|
| Concentration of source of nickel (nickel sulphate solution) (A) | g/L | 20 | 25a | 30 |
| Concentration of reducing agent (sodium hypophosphite solution) (B) | g/L | 14 | 17a | 20 |
| Concentration of source of tungsten (sodium tungstate) (C) | g/L | 15 | 20a | 25 |
| Annealing temperature (D) |
°C | 400 | 500 | 600 |
|