Investigation On Silica Sol Ceramic Mold

Ceramic mold using silica sol as binder was prepared by the colloidal molding technique. The chief Investigation works are its slurry prescription, drying process, soaking process and molding mechanism of silica sol ceramic mold. The materials used to prepare silica sol mold were JN-30 silica sol, silica powder and NH₄Cl. Some results as follow are obtained by a large quantity experiments.(1) The coagulation harden time of prepared silica sol ceramic slurry with addition 7-8% NH₄Cl solution which concentration is 15% when powder solution ratio is 3.2-3.4 : 1 is only 15-30min.(2) The wet stock of silica sol ceramic mold can be dried by vacuum. The vacuum drying process are:(1) vacuum drying temperature: 80-100℃, vacuum: 0.06-0.07MPa, vacuum drying time: 5h.(3) The repeat experiment show that expectancy on shrinkage ratio and compressive resistance strength of silica sol ceramic mold is separately 0.97%, 1.04% and 5.05MPa. Variance on shrinkage ratio and compressive strength of silica sol ceramic mold is separately 0.0086,0.0086 and 0.4511.(4) Silica sol ceramic mold after drying have to be soaked in high temperature. The roasting process are: (1) roasting temperature: 1050-1150℃(2) soaking time: 2h.(5) The addition of NH₄Cl solution can be reduced by adding a little subnano-SiO₂ to silica powder. The disadvantage caused by NH₄Cl solution is weakened. The proper quantities of addition subnano- SiO₂ is 1.4%. (6) Silica powder added ZrSiO₄ can improve the properties of silica sol ceramic mold. The proper quantities of addition ZrSiO₄ is 20-25%.The results show that NH₄Cl solution can accelerate the coagulation hardening of silica sol ceramic slurry. The wet stock of silica sol ceramic mold can be dried by vacuum, and the drying conditions are not severe. The research found that addition of NH₄Cl solution can be reduced by adding subnano-SiO₂, reducing the disadvantage factors caused by NH₄Cl solution. The properties of silica sol ceramic mold can be improved by adding ZrSiO₄ to silica powder.In this paper, the accelerate coagulation mechanism on NH₄Cl solution in silica sol ceramic slurry were analyzed by associative with coagulation principle, thermodynamics and dynamics. The subnano-SiO₂ cooperating accelerates coagulation mechanics to NH₄Cl solution in silica sol ceramic slurry were analyzed by applying nanometer effect. At the meantime, analyzing the vacuum drying mechanism and soaking mechanism of silica sol ceramic mold.