Studies Of Electroless Plating On Surface Of Fly Ash Cenospheres

Silver-coated fly ash cenospheres were prepared by slowly adding AgNO3into the mixed solution contained D-glucose solution, ammonium spirit and sodium solution after thermo-alkaline and coarsening treatment instead of Palladium salt activating. The composite powders were analyzed by SEM, EDS and XRD, etal. The results revealed that,1. Silver layer were detected after electroless plating by using thermo-alkaline and coarsening treatment, and the layer is complete, uniform and compact. When the pH value is12.5and the loading quantity is4g/L, the resistivity of composite powder prepared after thermo-alkaline treatment can reach to0.05Ω·cm, and the other reaches to0.011Ω·cm2. The composite powder conductivity improved while Ag proportion rised as a result of pH increase. However, too high pH value accelerating selfdecomposition. Compared to thermo-alkline treatment, coarsening treatment made plating solution more stable. Powder load quantity, largely influenced composite on silver relative content and electro-conductivity, should be controlled properly. When redox reaction proceeding efficiently, Ag+concentration should be higher than1.2g/L.3. Plating solution was more stable while adding Cu2+in electroless plating process, but led to less sliver deposit and the silver layer is uncomplete and unsound. Surfactant has little impact on silver plating improvement.4. Both the two composite powders conductivity improved after heat treatment. The silver coated powder prepared after thermo-alkline treatment gained lower resistivity which can reach to0.011Ω·cm after heat treatment at250℃for40minutes. The other reached to0.0043Ω·cm after heat treatment at350℃for20minutes.5. After thermo-alkline treatment, cenospheres surface were occupied by lots of hydroxy groups which attracted Ag+coming to be restored and then Ag deposited. Cenosperes have porous structure and its surface were more active and rough after coarsening, NH3·H2O particles can be adsorbed on the surface in plating solution. Then [Ag(NH3)2]+come into exist after Ag+complexing NH3·H2O, and finally Ag+was restored and Ag deposited on cenospheres surface.