Surface Modification Of Zirconia And Gelcasting Process

Zirconia ceramics are widely used in bearings,refractories,sensors,mobile phone backboard and other fields for their high strength,similar hardness to diamond,good wear resistance and beautiful appearance.Especially in the field of mobile phone backplane,with the advent of 5g era,the performance requirements of mobile phone backplane are higher.Zirconia ceramic mobile phone backplane stands out with its own advantages,currently there exist two problems in zirconia ceramic.On the one hand,it is the case of molding technology.At present,most of the zirconia ceramic mobile phone backplane technologies used in China are tape casting,injection molding and so on.These processes have the problems of low mechanical properties and low yield of ceramic products.On the other hand,the agglomeration of nano zirconia powder affects the internal structure uniformity,resulting in the internal inhomogeneity and low impact strength of ceramic products.These problems have become the factors restricting the development of zirconia ceramic mobile phone backplane.Gel-casting process has been widely used in ceramic molding.The high performance ceramic products are prepared by wet molding and sintering through the combination of organic and ceramic powders.The key of the molding process is to prepare slurry with high solid content and low viscosity,and it is difficult to obtain high-performance products.Nano powders are easily agglomerated in water and rice noodles are difficult to obtain good properties.Therefore,the gel-casting process parameters and the problem of rice noodles agglomeration are studied in this paper.In order to solve the agglomeration problem of nano zirconia powder,the properties of water-soluble silane coupling agent(KH550,KH560)and chelating titanate coupling agent-311w on the surface of zirconia powder were studied.A layer of adsorption film was formed by chemical adsorption reaction between the coupling agent and the powder surface,which changed the type of chemical bond on the surface of the powder and solved the problem of powder agglomeration.The properties of zirconia powders before and after modification were characterized by FTIR,BET,TEM,SEM and TG,and the properties of zirconia ceramics after modification were characterized by SEM,XRD and mechanical properties.The experimental results are as follows:the best technological parameters of gel casting are:PBTCA addition amount is 0.2%,p H=10.5,APS is 0.5wt%,TEMED is 0.3vol%,curing temperature is 60 degrees,and sintering temperature is 1520 degrees.At this time,zirconia ceramics with strength of 25.06MPa after drying,strength of 674.83MPa after sintering and17.75KJ/m~2 of impact strength can be obtained.When the amount of KH560 is 0.7%,the bending strength is the most.When the amount of KH550 is 0.7,the bending strength and impact strength are the highest,which are 920.46Mpa and 18.8833KJ/m~2,respectively,which are 36.4%and 6.38%higher than those before modification When the amount of coupling agent-311W is 0.4%,the bending strength and impact strength of zirconia ceramics are the maximum,which are 800.67 Mpa and 16.8KJ/m~2,respectively.The bending strength is increased by 18.64%and the impact strength is decreased,but the effect of improving powder dispersion is the best.