The Research On The Process Of Self-assemble Film Of SiO₂ Encapsulated On The Surface Of Aluminium Flakes

Due to its special metal and glossy properties,flaky aluminium is widelyused in industrial production,especially in ink,plastic,automotive paint and marine coatings.However,the activity of aluminium flakes seriously affects its practical application,so it is necessary to modify the surface of aluminium flakes to improve its surface anti-oxidation and corrosion resistance.In this work,it was studied that the coating process of using the TEOS as the raw materials,acid and alkali as the catalyst,which would be form nano silica that is two different structures in two steps catalytic coating.The two different structure nano silica would be self-assembly into dense film,which coating on the surface of aluminium flakes in order to avoid corrosion of aluminium flakes.The single catalytic coating process,the effect of the reaction times,the amount of ethanol,catalysis,TEOS;water and aluminium flakes on the quality of the coating was studied in this thesis.The result indicated that the best condition is TEOS:ETOH:HC1:H2O=1:20:0.004:1.6 in acid catalyzed coating,while in alkali catalyzed coating,the best condition is TEOS:ETOH:NH3.H2O:H2O=1:6.25:0.15:0.75.The effect of different sequence of self-assemble between acid and alkali catalyed coating on the quality of the coating was also invesitgated.It means that what is the best self-assemble sequence between the alkaline catalysis coating was prepared by acid catalysis or the acid catalysis coating was prepared by alkaline catalysis.The results show that the best combination of acid catalysis firstly is acid catalytic coating ratio:alkali catalyzed coating ratio =1:1.The best combination of alkali catalysis firstly is alkali catalyzed coating ratio:acid catalytic coating ratio = 2:1.However,the acid catalytic coating firstly is better than alkali catalytic coating firstly from the results of the production of hydrogen.Furthermore,a series of testing including FTIR,XRD,TG,SEM,BET and ZETA potential measurement was conducted for analysis and characterization of the samples.The results show that the two different structure of silica nanoparticles by surface electrostatic force and hydrogen bond to make them self-assembly into dense silica coating on the surface of aluminium flakes.The film is denser than that catalyzed by single acid or alkali catalysis,so it could improve its corrosion resistance and high temperature resistant performance.The feasibility of this self-assembled silicon dioxide film is further verified by theoretical calculation of the self-assembly process of the two different structures of nano-silica particles.