Production speed too slow, the bottom again, such as nickel oxide layer in gold slot oxidation (or gold reduction), peel tin.

By adopting photo-reduction, chemical and electrochemistry technology, the preparations and influencing factors of nano-silver, nano- nickel and hydration silica were researched respectively.

Selective leaching of nickel, cobalt and copper from cobalt crusts was attained by using ammonium carbonate solution and sulfur dioxide gas as a reductant.