Dear Maryam,

Alumina NW are being obtained when reaction rate between grown oxide and electrolyte is greater than oxide growth. Otherwise, You will get nanopores. 80 V provides quite quick oxide growth rate, so I advice you firstly, to increase the temperature. Of course, the longer second step of anodization, the wider pores (longer reaction between pores and electrolyte).

If I were You I would start from about 20 deg C and about 14-6 hours of the second step.

Good luck!

Thanks so much, you mean i use 80 V with 20 deg C but i cant understand what time we use for first and second anodizing?

The longer first step of anodization, the better arrangement of concaves on the aluminum surface after oxide removal and the better final arrangement. It is up to You, how long You will perform the first step of anodization. It depends how thick aluminum substrate You have. If I were You (assuming You have 0.25 mm thick Al foil) I would use about 10 hrs in the 1st step and after oxide removal I would conduct anodization for about 14-16 hours.

If You won't obtain wires, but pores, I would increase temperature for 10 deg C.

Thanks so much

For better nanostructuring, it is better to anodize in galvanostatic mode!