Preparation And Process Research Of The Amorphous SiO₂ Gel For Fibre-Optical Perform By Sol-Gel

To prepare the mandril of SiO₂ optical fiber perform which have lower attenuation,we selected TEOS as raw material,C₂H₅OH and H₂O admixture as menstruum, HCl and CH₃NO as additive, prepared the mandril dry-gel material of SiO₂ optical fiber perform with SG(sol-gel)and studied primarily into additive,heat treatment temperature,time,heating-up velocity impact on SiO₂ dry-gel.TheXRD and SEM,ESCA were used to study dry-gel microstructure,chemical bond,phase structure and granularity.We selected preference 6 groups having better transparence,crystalline state,crack control capability in 200 groups of SiO₂ dry-gel executed to test and analyse with XRD and ESCA,and indicate the samples'microstructures are amorphous and the main chemical composition is Si and O.The experiment indicate that:when hydrochloric acid addition is less,the system delaminate.With much hydrochloric acid,steric hindrance of Si ion around is lower,and then hydrolyze velocity will be enhanced,so the gel time is less.When hydrochloric acid reach a fixed value,the yellow substance appear with temperature heating-up. And when TEOS:C₂H₅OH:H₂O:HCl=1:4:8:a,the gel purity is highest.And CH3NO is added to the system,we will find the dry-gel with SEM.Due to CH3NO added,the macropore structure appeared in dry-gel,and weakened capillary,and water transgression faster induce the crack in surface of gel reduced obviously and go to level up.With much CH₃NO addition, granularity of dry-gel largened,specific surface area diminished.But the more CH₃NO is, the worse transparence is.The best capability parameter is C₂H₅OH:H₂O:HCl:CH₃NO =1:4:8:a:b.At temperature 75℃,80℃,85℃,90℃,95℃,heating sol(C₂H₅OH:H₂O:HCl: CH₃NO=1:4:8:a:b) transform entirely into gel,the best temperature is 90℃.Putting the gel into oven at 90℃, we controlled heating-up velocity 1℃/ min,2℃/min,3℃/ min,4℃/min,5℃/ min,constant temperature is 4h,8h,16h,32h,64h,up to 180℃.The result indicate that the higher temperature is,the faster heating-up is,the more the micro-crack and micro-pore in dry-gel are.Iiquor mixture ratio is C₂H₅OH:H₂O:HCl:CH₃NO=1:4:8:a:b,sol reaction temperature is 90℃,gel heat treatment is 110℃,constant temperature time is 32h,SiO₂ dry-gel have best transparence,purity and crack conrol capability.