Dear Mohsen Sattari, I think there was no or bad ventilation during calcination. My Regards

DOI: 10.5772/67822

Dear Mohsen Sattari, I think there was no or bad ventilation during calcination. My Regards

DOI: 10.5772/67822

The presence of Ti3+ cations can give a blueish or black color to the material. Or you just have organic content inside your sample. You must check that with TG analysis.

Which temperature you used? How long?

Regards,

Hi;

The black color can result from the presence of residual organic matter on the nanoparticles of TiO2. To eliminate the excess of organic precursor it is necessary to make a repeated washing with deionized water and then with anhydrous alcohol.

With my best regards