Technique And Research On Application Of Thermal Shock Resistant Ceramics

This project is to study the method of improving the thermal shock resistance of alumina ceramics,because the tube for protecting thermocouples which is made of common ceramics bears the quick cooling and heating badly,splits very easily.In the experiment,Al₂O₃ powder is the basic material of nano-composite ceramics. We added appropriate amount of other kinds of powder,such as cordierite,aluminium titanate and eucryptite.The progress of making alumina matrix ceramics can be divided into mixing,shaping,discharging plastic and sintering,etc.In the process of shaping and sintering,dry pressing,isostatically pressing shaping technology and pressureless sintering technology were used respectively in the experiment.After the experiment,we determined the material gradient and the best technical process of alumina-cordierite mullite ceramics,alumina-aluminium titanate mullite ceramics and alumina-eucryptite mullite ceramics.In addition,the best synthesis technical of cordierite and eucryptite was also determined.Results of XRD show that the best synthesis technical of cordierite is synthesis temperature is 1400℃,heat preservation time is 2h,cooling rate is 0.8℃/min;The best synthesis technical of eucryptite is synthesis temperature is 1310℃,heat preservation time is 2h,cooling rate is 0.8℃/min.The microstructure of ceramics was observed in SEM.It was founded that the solid solution has formed in the matrix of alumina-cordierite mullite ceramics,and it looks as the shape of long strip distributing without any orderliness.It is effective to abate thermal stress and raise the strength of ceramics for such microstructure,and it is one of the most important reason that the properties of thermal shock resistance of the ceramics can be improved effectively.There are a lot of strengthened grains in the alumina-aluminium titanate mullite ceramics,these grains bond in the matrix so that they can prevent the expansion of crack and abate thermal stress effectively,and it is one of the most important reason that the properties of thermal shock resistance of the ceramics can be improved.The results show that when the amount of additive cordierite w(cordierite)=10%and the sintering temperature is 1520℃,the ceramics can endure the thermal shock with a temperature difference of 1500℃(cooling in air),and this is the best component of alumina-cordierite ceramics.When the amount of additive aluminium titanate w(aluminium titanate)=20%and the sintering temperature to be 1510℃,the ceramics can endure the thermal shock with a temperature difference of 1500℃(cooling in air),and this is the best component of alumina-aluminium titanate ceramics.When the mount of additive eucryptite w(eucryptite)=20%and the sintering temperature is 1500℃,the ceramics can endure the thermal shock with a temperature difference of 1500℃(cooling in air),and this is the best component of alumina-eucryptite ceramics.