Investigating On Chemistry Compositions Of The Surface Film Of Sodium Silicate Used Sand Hardened By Ester

The modification of sodium silicate sand and the recycling use of used sodium silicate sand are hot topics in the field of foundry at present, and are key technologies related to the clean production of casting.Firstly, such four nano oxide powder as Al₂O₃,ZnO,TiO₂,SiO₂ were used to carry out modification research on sodium silicate binder. The structure and ingredient of modified sodium silicate binder and sodium silicate sand were analyzed by SEM and X-ray Photoelectron Spectrum. Results show that such nano oxide powder can't improve the strength and collapsibility of sodium silicate remarkably, because the nano powder reacted with strongly-alkaline sodium silicate, and didn't disperse in sodium silicate in the state of grain, so the acidic or amphoteric nano oxide powder can't improve the strength and collapsibility of sodium silicate.Secondly, the emphasis of this paper were put on analysing the main composition of rudimental film on the surface of sodium silicate and its influence to the performance of sodium silicate sand. Results show that, besides the main ingredient such as Na2O and SiO2 etc, there are sodium acetate, sodium oxalate, sodium carbonate, and residual ester in the rudimental film on the surface of sodium silicate. The influence of other salts such as sodium acetate and sodium oxalate on sodium silicate sand is negligible, while the main factor that influences the reclamation of used sodium silicate sand was residual Na2O and ester. The ablated temperature of residual ester was at 300℃-350℃. As a result, most of residual ester on rudimental film of sodium silicate would be ablated at the temperature of 300℃-350℃. Finally, the relation between PH value and the performance of sodium silicate recycling use sand was studied under different conditions through the method of measuring the PH value of aqueous solution of sodium silicate reclamation sand. The results express that PH value can perfectly represent the quality of reclamation sand. The relation between the change quantity of PH value and compression strength of reclamation sand was researched by testing the PH of aqueous solution of sodium silicate used sand.